ALBERT

Description: Diffuse synchrotron emission from galactic cosmic ray electrons ASTRA Proceedings, 2, 21-26, 2015 Author(s): G. Di Bernardo, D. Grasso, C. Evoli, and D. Gaggero Synchrotron diffuse radiation (SDR) emission is one of the major Galactic components, in the 100 MHz up to 100 GHz frequency range. Its spectrum and sky map provide valuable measure of the galactic cosmic ray electrons (GCRE) in the relevant energy range, as well as of the strength and structure of the Galactic magnetic fields (GMF), both regular and random ones. This emission is an astrophysical sky foreground for the study of the Cosmic Microwave Background (CMB), and the extragalactic microwave measurements, and it needs to be modelled as better as possible. In this regard, in order to get an accurate description of the SDR in the Galaxy, we use – for the first time in this context – 3-dimensional GCRE models obtained by running the DRAGON code. This allows us to account for a realistic spiral arm pattern of the source distribution, demanded to get a self-consistent treatment of all relevant energy losses influencing the final synchrotron spectrum.

Description: The cosmic ray anisotropy below 10 15 eV ASTRA Proceedings, 2, 27-33, 2015 Author(s): G. Di Sciascio The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: A Consistent Scenario for the IBEX Ribbon, Anisotropies in TeV Cosmic Rays, and the Local Interstellar Medium N. A. Schwadron, P. Frisch, F. C. Adams, E. R. Christian, P. Desiati, H. O. Funsten, J. R. Jokipii, D. J. McComas, E. Moebius, and G. Zank ASTRA Proc., 2, 9-16, doi:10.5194/ap-2-9-2015, 2015 We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: TeV Cosmic Ray Anisotropy and the Heliospheric Magnetic Field P. Desiati and A. Lazarian ASTRA Proc., 1, 65-71, doi:10.5194/ap-1-65-2014, 2014 Cosmic rays are observed to possess a small non uniform distribution in arrival direction. Such anisotropy appears to have a roughly consistent topology between tens of GeV and hundreds of TeV, with a smooth energy dependency on phase and amplitude. Above a few hundreds of TeV a sudden change in the topology of the anisotropy is observed. The distribution of cosmic ray sources in the Milky Way is expected to inject anisotropy on the cosmic ray flux. The nearest and most recent sources, in particular, are expected to contribute more significantly than others. Moreover the interstellar medium is expected to have different characteristics throughout the Galaxy, with different turbulent properties and injection scales. Propagation effects in the interstellar magnetic field can shape the cosmic ray particle distribution as well. In particular, in the 1–10 TeV energy range, they have a gyroradius comparable to the size of the Heliosphere, assuming a typical interstellar magnetic field strength of 3 μG. Therefore they are expected to be strongly affected by the Heliosphere in a manner ordered by the direction of the local interstellar magnetic field and of the heliotail. In this paper we discuss on the possibility that TeV cosmic rays arrival distribution might be significantly redistributed as they propagate through the Heliosphere.

Description: Diffuse synchrotron emission from galactic cosmic ray electrons G. Di Bernardo, D. Grasso, C. Evoli, and D. Gaggero ASTRA Proc., 2, 21-26, doi:10.5194/ap-2-21-2015, 2015 Magnetic fields permeate the interstellar medium (ISM), extending far beyond the Galactic disc. The non-thermal phenomena, like e.g. the Galactic radio emission is doubtless a viable method of observation to clearly delineate the magnetic structure of our Galaxy. In this regard, the aim addressed in this contribution is to simulate the polarized Galactic synchrotron emission, due to the diffuse radiation by charged relativistic particles, at all relevant frequencies, 10 MHz up to 100 GHz.

Description: Effects of stellar evolution and ionizing radiation on the environments of massive stars J. Mackey, N. Langer, S. Mohamed, V. V. Gvaramadze, H. R. Neilson, and D. M.-A. Meyer ASTRA Proc., 1, 61-63, doi:10.5194/ap-1-61-2014, 2014 We discuss two important effects for the astrospheres of runaway stars: the propagation of ionizing photons far beyond the astropause, and the rapid evolution of massive stars (and their winds) near the end of their lives. Hot stars emit ionizing photons with associated photoheating that has a significant dynamical effect on their surroundings. 3-D simulations show that H ii regions around runaway O stars drive expanding conical shells and leave underdense wakes in the medium they pass through. For late O stars this feedback to the interstellar medium is more important than that from stellar winds. Late in life, O stars evolve to cool red supergiants more rapidly than their environment can react, producing transient circumstellar structures such as double bow shocks. This provides an explanation for the bow shock and linear bar-shaped structure observed around Betelgeuse.

Description: Cosmic ray transport and anisotropies to high energies P. L. Biermann, L. I. Caramete, A. Meli, B. N. Nath, E.-S. Seo, V. de Souza, and J. Becker Tjus ASTRA Proc., 2, 39-44, doi:10.5194/ap-2-39-2015, 2015 Using the data from the Interstellar Medium (ISM) we propose a physical model for the spectrum of the magnetic irregularities in the ISM. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: The cosmic ray anisotropy below 10 15 eV G. Di Sciascio ASTRA Proc., 2, 27-33, doi:10.5194/ap-2-27-2015, 2015 The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: The Local Bubble as a cosmic-ray isotropizer I. Gebauer, M. Weinreuter, S. Kunz, and D. Gaggero ASTRA Proc., 2, 1-3, doi:10.5194/ap-2-1-2015, 2015 The Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can dilute the directional information of energetic positrons and electrons in cosmic rays.

Description: Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube F. Bos, F. Tenholt, J. Becker Tjus, and S. Westerhoff ASTRA Proc., 2, 5-8, doi:10.5194/ap-2-5-2015, 2015 Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: The large-scale anisotropy with the PAMELA calorimeter A. Karelin, O. Adriani, G. Barbarino, G. Bazilevskaya, R. Bellotti, M. Boezio, E. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. Galper, S. Koldashov, S. Koldobskiy, S. Krut'kov, A. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. Mayorov, W. Menn, M. Mergé, V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. Ricciarini, R. Sarkar, M. Simon, V. Scotti, R. Sparvoli, P. Spillantini, Y. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. Voronov, Y. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 35-37, doi:10.5194/ap-2-35-2015, 2015 The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n -1 .

Description: Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays M. Kroll, J. Becker Tjus, B. Eichmann, and N. Nierstenhöfer ASTRA Proc., 2, 57-62, doi:10.5194/ap-2-57-2015, 2015 It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: Search for a positron anisotropy with PAMELA experiment B. Panico, O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, U. Giaccari, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 17-20, doi:10.5194/ap-2-17-2015, 2015 The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: The power spectrum of cosmic ray arrival directions M. Ahlers ASTRA Proc., 2, 45-49, doi:10.5194/ap-2-45-2015, 2015 Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: Observations of the anisotropy of cosmic rays at TeV–PeV S. BenZvi ASTRA Proc., 1, 33-37, doi:10.5194/ap-1-33-2014, 2014 During the past decade, multiple observatories have reported significant observations of the anisotropy of cosmic rays in the TeV energy band. The anisotropy has been observed at large scales and small scales in both the Northern and Southern Hemispheres. The source of the anisotropy is not well-understood, though both a galactic and a heliospheric origin have been suggested. We discuss recent observations of the shape and energy dependence of the anisotropy, with particular attention to measurements by the IceCube Neutrino Observatory in the Southern Hemisphere and the Milagro and High-Altitude Water Cherenkov (HAWC) observatories in the Northern Hemisphere.

Description: Lyman-α observations of astrospheres J. L. Linsky and B. E. Wood ASTRA Proc., 1, 43-49, doi:10.5194/ap-1-43-2014, 2014 Charge-exchange reactions between outflowing stellar wind protons and interstellar neutral hydrogen atoms entering a stellar astrosphere produce a region of piled-up-decelerated neutral hydrogen called the hydrogen wall. Absorption by this gas, which is observed in stellar Lyman-α emission lines, provides the only viable technique at this time for measuring the mass-loss rates of F–M dwarf stars. We describe this technique, present an alternative way for understanding the relation of mass-loss rate with X-ray emission, and identify several critical issues.

Description: Cosmic ray particles from exploding massive stars with winds P. L. Biermann ASTRA Proc., 1, 29-31, doi:10.5194/ap-1-29-2014, 2014 The origin of cosmic rays is still unsettled. Many sources have been proposed over the years, and exploding stars still provide the most promising candidates. Here we examine one of these scenarios, and compare the resulting predictions with data: Massive stars have winds, and when these stars explode, the resulting shock runs through the wind. The observable phenomenon is called radio-supernova, and many have been observed in non-thermal radio emission. This emission allows to determine the magnetic field in the wind as a function of radius, and so allows to check, whether such explosions can achieve the high energies required and also explain the flux and the spectra of cosmic rays. The observations show this to be the case, and so we conclude that radio supernovae can explain the high-energy Galactic cosmic rays over the entire energy range, and that the spectral predictions are compatible with observations.

Description: A solution to the cosmic ray anisotropy problem P. Mertsch and S. Funk ASTRA Proc., 2, 51-55, doi:10.5194/ap-2-51-2015, 2015 Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube ASTRA Proceedings, 2, 5-8, 2015 Author(s): F. Bos, F. Tenholt, J. Becker Tjus, and S. Westerhoff Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: The large-scale anisotropy with the PAMELA calorimeter ASTRA Proceedings, 2, 35-37, 2015 Author(s): A. Karelin, O. Adriani, G. Barbarino, G. Bazilevskaya, R. Bellotti, M. Boezio, E. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. Galper, S. Koldashov, S. Koldobskiy, S. Krut'kov, A. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. Mayorov, W. Menn, M. Mergé, V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. Ricciarini, R. Sarkar, M. Simon, V. Scotti, R. Sparvoli, P. Spillantini, Y. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. Voronov, Y. Yurkin, G. Zampa, and N. Zampa The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n -1 .

Description: Cosmic ray transport and anisotropies to high energies ASTRA Proceedings, 2, 39-44, 2015 Author(s): P. L. Biermann, L. I. Caramete, A. Meli, B. N. Nath, E.-S. Seo, V. de Souza, and J. Becker Tjus A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum k -5/3 at small scales λ = 2 π/ k with k the wave-number, then a saturation spectrum k -1 , and finally a shock-dominated spectrum k -2 mostly in the halo/wind outside the Cosmic Ray disk. In an isotropic approximation such a model is consistent with the Interstellar Medium (ISM) data. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: The power spectrum of cosmic ray arrival directions ASTRA Proceedings, 2, 45-49, 2015 Author(s): M. Ahlers Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: A solution to the cosmic ray anisotropy problem ASTRA Proceedings, 2, 51-55, 2015 Author(s): P. Mertsch and S. Funk Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence F. Fraschetti ASTRA Proc., 2, 63-65, doi:10.5194/ap-2-63-2016, 2016 Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.

Description: Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence F. Fraschetti ASTRA Proc., 2, 63-65, doi:10.5194/ap-2-63-2016, 2016 Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.

Description: 〈b〉Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence〈/b〉〈br〉 F. Fraschetti〈br〉 ASTRA Proc., 2, 63-65, https://doi.org/10.5194/ap-2-63-2016, 2016〈br〉 Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.

Description: 〈b〉The power spectrum of cosmic ray arrival directions〈/b〉〈br〉 M. Ahlers〈br〉 ASTRA Proc., 2, 45-49, https://doi.org/10.5194/ap-2-45-2015, 2015〈br〉 Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: 〈b〉Cosmic ray transport and anisotropies to high energies〈/b〉〈br〉 P. L. Biermann, L. I. Caramete, A. Meli, B. N. Nath, E.-S. Seo, V. de Souza, and J. Becker Tjus〈br〉 ASTRA Proc., 2, 39-44, https://doi.org/10.5194/ap-2-39-2015, 2015〈br〉 Using the data from the Interstellar Medium (ISM) we propose a physical model for the spectrum of the magnetic irregularities in the ISM. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: 〈b〉A Consistent Scenario for the IBEX Ribbon, Anisotropies in TeV Cosmic Rays, and the Local Interstellar Medium〈/b〉〈br〉 N. A. Schwadron, P. Frisch, F. C. Adams, E. R. Christian, P. Desiati, H. O. Funsten, J. R. Jokipii, D. J. McComas, E. Moebius, and G. Zank〈br〉 ASTRA Proc., 2, 9-16, https://doi.org/10.5194/ap-2-9-2015, 2015〈br〉 We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: 〈b〉Search for a positron anisotropy with PAMELA experiment〈/b〉〈br〉 B. Panico, O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, U. Giaccari, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, and N. Zampa〈br〉 ASTRA Proc., 2, 17-20, https://doi.org/10.5194/ap-2-17-2015, 2015〈br〉 The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: 〈b〉Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays〈/b〉〈br〉 M. Kroll, J. Becker Tjus, B. Eichmann, and N. Nierstenhöfer〈br〉 ASTRA Proc., 2, 57-62, https://doi.org/10.5194/ap-2-57-2015, 2015〈br〉 It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: 〈b〉A solution to the cosmic ray anisotropy problem〈/b〉〈br〉 P. Mertsch and S. Funk〈br〉 ASTRA Proc., 2, 51-55, https://doi.org/10.5194/ap-2-51-2015, 2015〈br〉 Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for 〈i〉hadronic〈/i〉 CRs is not understood, in the sense that isotropic diffusion models 〈i〉overpredict〈/i〉 the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: The power spectrum of cosmic ray arrival directions M. Ahlers ASTRA Proc., 2, 45-49, doi:10.5194/ap-2-45-2015, 2015 Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: The Local Bubble as a cosmic-ray isotropizer I. Gebauer, M. Weinreuter, S. Kunz, and D. Gaggero ASTRA Proc., 2, 1-3, doi:10.5194/ap-2-1-2015, 2015 The Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can dilute the directional information of energetic positrons and electrons in cosmic rays.

Description: A Consistent Scenario for the IBEX Ribbon, Anisotropies in TeV Cosmic Rays, and the Local Interstellar Medium N. A. Schwadron, P. Frisch, F. C. Adams, E. R. Christian, P. Desiati, H. O. Funsten, J. R. Jokipii, D. J. McComas, E. Moebius, and G. Zank ASTRA Proc., 2, 9-16, doi:10.5194/ap-2-9-2015, 2015 We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: TeV Cosmic Ray Anisotropy and the Heliospheric Magnetic Field P. Desiati and A. Lazarian ASTRA Proc., 1, 65-71, doi:10.5194/ap-1-65-2014, 2014 Cosmic rays are observed to possess a small non uniform distribution in arrival direction. Such anisotropy appears to have a roughly consistent topology between tens of GeV and hundreds of TeV, with a smooth energy dependency on phase and amplitude. Above a few hundreds of TeV a sudden change in the topology of the anisotropy is observed. The distribution of cosmic ray sources in the Milky Way is expected to inject anisotropy on the cosmic ray flux. The nearest and most recent sources, in particular, are expected to contribute more significantly than others. Moreover the interstellar medium is expected to have different characteristics throughout the Galaxy, with different turbulent properties and injection scales. Propagation effects in the interstellar magnetic field can shape the cosmic ray particle distribution as well. In particular, in the 1–10 TeV energy range, they have a gyroradius comparable to the size of the Heliosphere, assuming a typical interstellar magnetic field strength of 3 μG. Therefore they are expected to be strongly affected by the Heliosphere in a manner ordered by the direction of the local interstellar magnetic field and of the heliotail. In this paper we discuss on the possibility that TeV cosmic rays arrival distribution might be significantly redistributed as they propagate through the Heliosphere.

Description: Cosmic rays as regulators of molecular cloud properties M. Padovani, P. Hennebelle, and D. Galli ASTRA Proc., 1, 23-27, doi:10.5194/ap-1-23-2014, 2014 Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.

Description: Lyman-α observations of astrospheres J. L. Linsky and B. E. Wood ASTRA Proc., 1, 43-49, doi:10.5194/ap-1-43-2014, 2014 Charge-exchange reactions between outflowing stellar wind protons and interstellar neutral hydrogen atoms entering a stellar astrosphere produce a region of piled-up-decelerated neutral hydrogen called the hydrogen wall. Absorption by this gas, which is observed in stellar Lyman-α emission lines, provides the only viable technique at this time for measuring the mass-loss rates of F–M dwarf stars. We describe this technique, present an alternative way for understanding the relation of mass-loss rate with X-ray emission, and identify several critical issues.

Description: A solution to the cosmic ray anisotropy problem P. Mertsch and S. Funk ASTRA Proc., 2, 51-55, doi:10.5194/ap-2-51-2015, 2015 Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays M. Kroll, J. Becker Tjus, B. Eichmann, and N. Nierstenhöfer ASTRA Proc., 2, 57-62, doi:10.5194/ap-2-57-2015, 2015 It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: The large-scale anisotropy with the PAMELA calorimeter A. Karelin, O. Adriani, G. Barbarino, G. Bazilevskaya, R. Bellotti, M. Boezio, E. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. Galper, S. Koldashov, S. Koldobskiy, S. Krut'kov, A. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. Mayorov, W. Menn, M. Mergé, V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. Ricciarini, R. Sarkar, M. Simon, V. Scotti, R. Sparvoli, P. Spillantini, Y. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. Voronov, Y. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 35-37, doi:10.5194/ap-2-35-2015, 2015 The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n -1 .

Description: Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube F. Bos, F. Tenholt, J. Becker Tjus, and S. Westerhoff ASTRA Proc., 2, 5-8, doi:10.5194/ap-2-5-2015, 2015 Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence F. Fraschetti ASTRA Proc., 2, 63-65, doi:10.5194/ap-2-63-2016, 2016 Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.

Description: The cosmic ray anisotropy below 10 15 eV G. Di Sciascio ASTRA Proc., 2, 27-33, doi:10.5194/ap-2-27-2015, 2015 The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: Cosmic ray transport and anisotropies to high energies P. L. Biermann, L. I. Caramete, A. Meli, B. N. Nath, E.-S. Seo, V. de Souza, and J. Becker Tjus ASTRA Proc., 2, 39-44, doi:10.5194/ap-2-39-2015, 2015 Using the data from the Interstellar Medium (ISM) we propose a physical model for the spectrum of the magnetic irregularities in the ISM. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: Diffuse synchrotron emission from galactic cosmic ray electrons G. Di Bernardo, D. Grasso, C. Evoli, and D. Gaggero ASTRA Proc., 2, 21-26, doi:10.5194/ap-2-21-2015, 2015 Magnetic fields permeate the interstellar medium (ISM), extending far beyond the Galactic disc. The non-thermal phenomena, like e.g. the Galactic radio emission is doubtless a viable method of observation to clearly delineate the magnetic structure of our Galaxy. In this regard, the aim addressed in this contribution is to simulate the polarized Galactic synchrotron emission, due to the diffuse radiation by charged relativistic particles, at all relevant frequencies, 10 MHz up to 100 GHz.

Description: Effects of stellar evolution and ionizing radiation on the environments of massive stars J. Mackey, N. Langer, S. Mohamed, V. V. Gvaramadze, H. R. Neilson, and D. M.-A. Meyer ASTRA Proc., 1, 61-63, doi:10.5194/ap-1-61-2014, 2014 We discuss two important effects for the astrospheres of runaway stars: the propagation of ionizing photons far beyond the astropause, and the rapid evolution of massive stars (and their winds) near the end of their lives. Hot stars emit ionizing photons with associated photoheating that has a significant dynamical effect on their surroundings. 3-D simulations show that H ii regions around runaway O stars drive expanding conical shells and leave underdense wakes in the medium they pass through. For late O stars this feedback to the interstellar medium is more important than that from stellar winds. Late in life, O stars evolve to cool red supergiants more rapidly than their environment can react, producing transient circumstellar structures such as double bow shocks. This provides an explanation for the bow shock and linear bar-shaped structure observed around Betelgeuse.

Description: Observations of the anisotropy of cosmic rays at TeV–PeV S. BenZvi ASTRA Proc., 1, 33-37, doi:10.5194/ap-1-33-2014, 2014 During the past decade, multiple observatories have reported significant observations of the anisotropy of cosmic rays in the TeV energy band. The anisotropy has been observed at large scales and small scales in both the Northern and Southern Hemispheres. The source of the anisotropy is not well-understood, though both a galactic and a heliospheric origin have been suggested. We discuss recent observations of the shape and energy dependence of the anisotropy, with particular attention to measurements by the IceCube Neutrino Observatory in the Southern Hemisphere and the Milagro and High-Altitude Water Cherenkov (HAWC) observatories in the Northern Hemisphere.

Description: Search for a positron anisotropy with PAMELA experiment B. Panico, O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, U. Giaccari, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 17-20, doi:10.5194/ap-2-17-2015, 2015 The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: Clumps in stellar winds J. S. Vink ASTRA Proc., 1, 39-41, doi:10.5194/ap-1-39-2014, 2014 We discuss the origin and quantification of wind clumping and mass–loss rates (Ṁ), particularly in close proximity to the Eddington (Γ) limit, relevant for very massive stars (VMS). We present evidence that clumping may not be the result of the line-deshadowing instability (LDI), but that clumps are already present in the stellar photosphere.

Description: MHD flows at astropauses and in astrotails D. H. Nickeler, T. Wiegelmann, M. Karlický, and M. Kraus ASTRA Proc., 1, 51-60, doi:10.5194/ap-1-51-2014, 2014 The geometrical shapes and the physical properties of stellar wind – interstellar medium interaction regions form an important stage for studying stellar winds and their embedded magnetic fields as well as cosmic ray modulation. Our goal is to provide a proper representation and classification of counter-flow configurations and counter-flow interfaces in the frame of fluid theory. In addition we calculate flows and large-scale electromagnetic fields based on which the large-scale dynamics and its role as possible background for particle acceleration, e.g., in the form of anomalous cosmic rays, can be studied. We find that for the definition of the boundaries, which are determining the astropause shape, the number and location of magnetic null points and stagnation points is essential. Multiple separatrices can exist, forming a highly complex environment for the interstellar and stellar plasma. Furthermore, the formation of extended tail structures occur naturally, and their stretched field and streamlines provide surroundings and mechanisms for the acceleration of particles by field-aligned electric fields.

Description: Cosmic ray particles from exploding massive stars with winds P. L. Biermann ASTRA Proc., 1, 29-31, doi:10.5194/ap-1-29-2014, 2014 The origin of cosmic rays is still unsettled. Many sources have been proposed over the years, and exploding stars still provide the most promising candidates. Here we examine one of these scenarios, and compare the resulting predictions with data: Massive stars have winds, and when these stars explode, the resulting shock runs through the wind. The observable phenomenon is called radio-supernova, and many have been observed in non-thermal radio emission. This emission allows to determine the magnetic field in the wind as a function of radius, and so allows to check, whether such explosions can achieve the high energies required and also explain the flux and the spectra of cosmic rays. The observations show this to be the case, and so we conclude that radio supernovae can explain the high-energy Galactic cosmic rays over the entire energy range, and that the spectral predictions are compatible with observations.

Description: Cosmic ray transport and anisotropies to high energies P. L. Biermann, L. I. Caramete, A. Meli, B. N. Nath, E.-S. Seo, V. de Souza, and J. Becker Tjus ASTRA Proc., 2, 39-44, https://doi.org/10.5194/ap-2-39-2015, 2015 Using the data from the Interstellar Medium (ISM) we propose a physical model for the spectrum of the magnetic irregularities in the ISM. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays M. Kroll, J. Becker Tjus, B. Eichmann, and N. Nierstenhöfer ASTRA Proc., 2, 57-62, https://doi.org/10.5194/ap-2-57-2015, 2015 It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: A Consistent Scenario for the IBEX Ribbon, Anisotropies in TeV Cosmic Rays, and the Local Interstellar Medium N. A. Schwadron, P. Frisch, F. C. Adams, E. R. Christian, P. Desiati, H. O. Funsten, J. R. Jokipii, D. J. McComas, E. Moebius, and G. Zank ASTRA Proc., 2, 9-16, https://doi.org/10.5194/ap-2-9-2015, 2015 We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: MHD flows at astropauses and in astrotails D. H. Nickeler, T. Wiegelmann, M. Karlický, and M. Kraus ASTRA Proc., 1, 51-60, https://doi.org/10.5194/ap-1-51-2014, 2014 The geometrical shapes and the physical properties of stellar wind – interstellar medium interaction regions form an important stage for studying stellar winds and their embedded magnetic fields as well as cosmic ray modulation. Our goal is to provide a proper representation and classification of counter-flow configurations and counter-flow interfaces in the frame of fluid theory. In addition we calculate flows and large-scale electromagnetic fields based on which the large-scale dynamics and its role as possible background for particle acceleration, e.g., in the form of anomalous cosmic rays, can be studied. We find that for the definition of the boundaries, which are determining the astropause shape, the number and location of magnetic null points and stagnation points is essential. Multiple separatrices can exist, forming a highly complex environment for the interstellar and stellar plasma. Furthermore, the formation of extended tail structures occur naturally, and their stretched field and streamlines provide surroundings and mechanisms for the acceleration of particles by field-aligned electric fields.

Description: Observations of the anisotropy of cosmic rays at TeV–PeV S. BenZvi ASTRA Proc., 1, 33-37, https://doi.org/10.5194/ap-1-33-2014, 2014 During the past decade, multiple observatories have reported significant observations of the anisotropy of cosmic rays in the TeV energy band. The anisotropy has been observed at large scales and small scales in both the Northern and Southern Hemispheres. The source of the anisotropy is not well-understood, though both a galactic and a heliospheric origin have been suggested. We discuss recent observations of the shape and energy dependence of the anisotropy, with particular attention to measurements by the IceCube Neutrino Observatory in the Southern Hemisphere and the Milagro and High-Altitude Water Cherenkov (HAWC) observatories in the Northern Hemisphere.

Description: Cosmic rays as regulators of molecular cloud properties M. Padovani, P. Hennebelle, and D. Galli ASTRA Proc., 1, 23-27, https://doi.org/10.5194/ap-1-23-2014, 2014 Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.

Description: Cosmic ray particles from exploding massive stars with winds P. L. Biermann ASTRA Proc., 1, 29-31, https://doi.org/10.5194/ap-1-29-2014, 2014 The origin of cosmic rays is still unsettled. Many sources have been proposed over the years, and exploding stars still provide the most promising candidates. Here we examine one of these scenarios, and compare the resulting predictions with data: Massive stars have winds, and when these stars explode, the resulting shock runs through the wind. The observable phenomenon is called radio-supernova, and many have been observed in non-thermal radio emission. This emission allows to determine the magnetic field in the wind as a function of radius, and so allows to check, whether such explosions can achieve the high energies required and also explain the flux and the spectra of cosmic rays. The observations show this to be the case, and so we conclude that radio supernovae can explain the high-energy Galactic cosmic rays over the entire energy range, and that the spectral predictions are compatible with observations.

Description: Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube F. Bos, F. Tenholt, J. Becker Tjus, and S. Westerhoff ASTRA Proc., 2, 5-8, https://doi.org/10.5194/ap-2-5-2015, 2015 Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: The large-scale anisotropy with the PAMELA calorimeter A. Karelin, O. Adriani, G. Barbarino, G. Bazilevskaya, R. Bellotti, M. Boezio, E. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. Galper, S. Koldashov, S. Koldobskiy, S. Krut'kov, A. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. Mayorov, W. Menn, M. Mergé, V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. Ricciarini, R. Sarkar, M. Simon, V. Scotti, R. Sparvoli, P. Spillantini, Y. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. Voronov, Y. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 35-37, https://doi.org/10.5194/ap-2-35-2015, 2015 The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n -1 .

Description: Diffuse synchrotron emission from galactic cosmic ray electrons G. Di Bernardo, D. Grasso, C. Evoli, and D. Gaggero ASTRA Proc., 2, 21-26, https://doi.org/10.5194/ap-2-21-2015, 2015 Magnetic fields permeate the interstellar medium (ISM), extending far beyond the Galactic disc. The non-thermal phenomena, like e.g. the Galactic radio emission is doubtless a viable method of observation to clearly delineate the magnetic structure of our Galaxy. In this regard, the aim addressed in this contribution is to simulate the polarized Galactic synchrotron emission, due to the diffuse radiation by charged relativistic particles, at all relevant frequencies, 10 MHz up to 100 GHz.

Description: The cosmic ray anisotropy below 10 15 eV G. Di Sciascio ASTRA Proc., 2, 27-33, https://doi.org/10.5194/ap-2-27-2015, 2015 The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: Effects of stellar evolution and ionizing radiation on the environments of massive stars J. Mackey, N. Langer, S. Mohamed, V. V. Gvaramadze, H. R. Neilson, and D. M.-A. Meyer ASTRA Proc., 1, 61-63, https://doi.org/10.5194/ap-1-61-2014, 2014 We discuss two important effects for the astrospheres of runaway stars: the propagation of ionizing photons far beyond the astropause, and the rapid evolution of massive stars (and their winds) near the end of their lives. Hot stars emit ionizing photons with associated photoheating that has a significant dynamical effect on their surroundings. 3-D simulations show that H ii regions around runaway O stars drive expanding conical shells and leave underdense wakes in the medium they pass through. For late O stars this feedback to the interstellar medium is more important than that from stellar winds. Late in life, O stars evolve to cool red supergiants more rapidly than their environment can react, producing transient circumstellar structures such as double bow shocks. This provides an explanation for the bow shock and linear bar-shaped structure observed around Betelgeuse.

Description: Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence F. Fraschetti ASTRA Proc., 2, 63-65, https://doi.org/10.5194/ap-2-63-2016, 2016 Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.

Description: A solution to the cosmic ray anisotropy problem P. Mertsch and S. Funk ASTRA Proc., 2, 51-55, https://doi.org/10.5194/ap-2-51-2015, 2015 Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: Lyman-α observations of astrospheres J. L. Linsky and B. E. Wood ASTRA Proc., 1, 43-49, https://doi.org/10.5194/ap-1-43-2014, 2014 Charge-exchange reactions between outflowing stellar wind protons and interstellar neutral hydrogen atoms entering a stellar astrosphere produce a region of piled-up-decelerated neutral hydrogen called the hydrogen wall. Absorption by this gas, which is observed in stellar Lyman-α emission lines, provides the only viable technique at this time for measuring the mass-loss rates of F–M dwarf stars. We describe this technique, present an alternative way for understanding the relation of mass-loss rate with X-ray emission, and identify several critical issues.

Description: Clumps in stellar winds J. S. Vink ASTRA Proc., 1, 39-41, https://doi.org/10.5194/ap-1-39-2014, 2014 We discuss the origin and quantification of wind clumping and mass–loss rates (Ṁ), particularly in close proximity to the Eddington (Γ) limit, relevant for very massive stars (VMS). We present evidence that clumping may not be the result of the line-deshadowing instability (LDI), but that clumps are already present in the stellar photosphere.

Description: The power spectrum of cosmic ray arrival directions M. Ahlers ASTRA Proc., 2, 45-49, https://doi.org/10.5194/ap-2-45-2015, 2015 Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: Search for a positron anisotropy with PAMELA experiment B. Panico, O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, U. Giaccari, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, and N. Zampa ASTRA Proc., 2, 17-20, https://doi.org/10.5194/ap-2-17-2015, 2015 The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: The Local Bubble as a cosmic-ray isotropizer I. Gebauer, M. Weinreuter, S. Kunz, and D. Gaggero ASTRA Proc., 2, 1-3, https://doi.org/10.5194/ap-2-1-2015, 2015 The Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can dilute the directional information of energetic positrons and electrons in cosmic rays.

Description: TeV Cosmic Ray Anisotropy and the Heliospheric Magnetic Field P. Desiati and A. Lazarian ASTRA Proc., 1, 65-71, https://doi.org/10.5194/ap-1-65-2014, 2014 Cosmic rays are observed to possess a small non uniform distribution in arrival direction. Such anisotropy appears to have a roughly consistent topology between tens of GeV and hundreds of TeV, with a smooth energy dependency on phase and amplitude. Above a few hundreds of TeV a sudden change in the topology of the anisotropy is observed. The distribution of cosmic ray sources in the Milky Way is expected to inject anisotropy on the cosmic ray flux. The nearest and most recent sources, in particular, are expected to contribute more significantly than others. Moreover the interstellar medium is expected to have different characteristics throughout the Galaxy, with different turbulent properties and injection scales. Propagation effects in the interstellar magnetic field can shape the cosmic ray particle distribution as well. In particular, in the 1–10 TeV energy range, they have a gyroradius comparable to the size of the Heliosphere, assuming a typical interstellar magnetic field strength of 3 μG. Therefore they are expected to be strongly affected by the Heliosphere in a manner ordered by the direction of the local interstellar magnetic field and of the heliotail. In this paper we discuss on the possibility that TeV cosmic rays arrival distribution might be significantly redistributed as they propagate through the Heliosphere.

Description: The Local Bubble as a cosmic-ray isotropizer ASTRA Proceedings, 2, 1-3, 2015 Author(s): I. Gebauer, M. Weinreuter, S. Kunz, and D. Gaggero The arrival directions of energetic positrons and electrons convey fundamental information on their origin. PAMELA, and more recently AMS, have measured an anomalous population of energetic positrons, which cannot be explained in standard cosmic ray propagation models. Two possible sources have been extensively discussed: astrophysical point sources, such as local pulsars, and dark matter. In the first case an anisotropy in the flux of energetic particles is expected. Reliable predictions of the level of anisotropy need to account for the Sun's peculiar environment: the Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can indeed dilute the directional information of energetic positrons and electrons.

Description: Gamma-ray emitting supernova remnants as the origin of Galactic cosmic rays ASTRA Proceedings, 2, 57-62, 2015 Author(s): M. Kroll, J. Becker Tjus, B. Eichmann, and N. Nierstenhöfer It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: Search for a positron anisotropy with PAMELA experiment ASTRA Proceedings, 2, 17-20, 2015 Author(s): B. Panico, O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. M. Galper, U. Giaccari, A. V. Karelin, S. V. Koldashov, S. Koldobskiy, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. G. Mayorov, W. Menn, M. Mergé, V. V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, R. Sarkar, V. Scotti, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. I. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, and N. Zampa The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: A Consistent Scenario for the IBEX Ribbon, Anisotropies in TeV Cosmic Rays, and the Local Interstellar Medium ASTRA Proceedings, 2, 9-16, 2015 Author(s): N. A. Schwadron, P. Frisch, F. C. Adams, E. R. Christian, P. Desiati, H. O. Funsten, J. R. Jokipii, D. J. McComas, E. Moebius, and G. Zank The Interstellar Boundary Explorer (IBEX) observes enhanced ~ keV energy Energetic Neutral Atoms (ENAs) from a narrow "ribbon" that stretches across the sky and appears to be centered on the direction of the local interstellar magnetic field. The Milagro collaboration, the Asγ collaboration and the IceCube observatory have made global maps of TeV cosmic rays. This paper provides links between these disparate observations. We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: Cosmic rays as regulators of molecular cloud properties M. Padovani, P. Hennebelle, and D. Galli ASTRA Proc., 1, 23-27, doi:10.5194/ap-1-23-2014, 2014 Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.

Description: Incorporating magnetic field observations in wind models of low-mass stars A. A. Vidotto ASTRA Proc., 1, 19-22, doi:10.5194/ap-1-19-2014, 2014 Stellar winds of cool, main-sequence stars are very tenuous and difficult to observe. Despite carrying away only a small amount of the stellar mass, they are important for regulating the rotation of the star and, consequently, its activity and magnetism. As it permeates the interplanetary space, the stellar wind interacts with any exoplanet encountered on its way, until it reaches the interstellar medium (ISM). These interactions can result in complex physical processes that depend on the characteristics of the wind. To better constrain the wind characteristics, more realistic wind models that account for factors such as stellar rotation and the complex/diverse observationally-derived stellar magnetic field configurations of cool stars are required. In this paper, I present a three-dimensional model of the wind of cool stars, which adopt as boundary condition observationally-derived magnetic maps. I also discuss how these studies are relevant for, e.g., the characterisation of the interaction between stellar winds and planets/ISM, and the propagation of cosmic rays.

Description: MHD flows at astropauses and in astrotails D. H. Nickeler, T. Wiegelmann, M. Karlický, and M. Kraus ASTRA Proc., 1, 51-60, doi:10.5194/ap-1-51-2014, 2014 The geometrical shapes and the physical properties of stellar wind – interstellar medium interaction regions form an important stage for studying stellar winds and their embedded magnetic fields as well as cosmic ray modulation. Our goal is to provide a proper representation and classification of counter-flow configurations and counter-flow interfaces in the frame of fluid theory. In addition we calculate flows and large-scale electromagnetic fields based on which the large-scale dynamics and its role as possible background for particle acceleration, e.g., in the form of anomalous cosmic rays, can be studied. We find that for the definition of the boundaries, which are determining the astropause shape, the number and location of magnetic null points and stagnation points is essential. Multiple separatrices can exist, forming a highly complex environment for the interstellar and stellar plasma. Furthermore, the formation of extended tail structures occur naturally, and their stretched field and streamlines provide surroundings and mechanisms for the acceleration of particles by field-aligned electric fields.

Description: Clumps in stellar winds J. S. Vink ASTRA Proc., 1, 39-41, doi:10.5194/ap-1-39-2014, 2014 We discuss the origin and quantification of wind clumping and mass–loss rates (Ṁ), particularly in close proximity to the Eddington (Γ) limit, relevant for very massive stars (VMS). We present evidence that clumping may not be the result of the line-deshadowing instability (LDI), but that clumps are already present in the stellar photosphere.

Description: 〈b〉The large-scale anisotropy with the PAMELA calorimeter〈/b〉〈br〉 A. Karelin, O. Adriani, G. Barbarino, G. Bazilevskaya, R. Bellotti, M. Boezio, E. Bogomolov, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, R. Carbone, P. Carlson, M. Casolino, G. Castellini, C. De Donato, C. De Santis, N. De Simone, V. Di Felice, V. Formato, A. Galper, S. Koldashov, S. Koldobskiy, S. Krut'kov, A. Kvashnin, A. Leonov, V. Malakhov, L. Marcelli, M. Martucci, A. Mayorov, W. Menn, M. Mergé, V. Mikhailov, E. Mocchiutti, A. Monaco, N. Mori, R. Munini, G. Osteria, F. Palma, B. Panico, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. Ricciarini, R. Sarkar, M. Simon, V. Scotti, R. Sparvoli, P. Spillantini, Y. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. Voronov, Y. Yurkin, G. Zampa, and N. Zampa〈br〉 ASTRA Proc., 2, 35-37, https://doi.org/10.5194/ap-2-35-2015, 2015〈br〉 The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n〈sup〉-1〈/sup〉.

Description: 〈b〉The cosmic ray anisotropy below 10〈sup〉15〈/sup〉 eV〈/b〉〈br〉 G. Di Sciascio〈br〉 ASTRA Proc., 2, 27-33, https://doi.org/10.5194/ap-2-27-2015, 2015〈br〉 The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: 〈b〉Diffuse synchrotron emission from galactic cosmic ray electrons〈/b〉〈br〉 G. Di Bernardo, D. Grasso, C. Evoli, and D. Gaggero〈br〉 ASTRA Proc., 2, 21-26, https://doi.org/10.5194/ap-2-21-2015, 2015〈br〉 Magnetic fields permeate the interstellar medium (ISM), extending far beyond the Galactic disc. The non-thermal phenomena, like e.g. the Galactic radio emission is doubtless a viable method of observation to clearly delineate the magnetic structure of our Galaxy. In this regard, the aim addressed in this contribution is to simulate the polarized Galactic synchrotron emission, due to the diffuse radiation by charged relativistic particles, at all relevant frequencies, 10 MHz up to 100 GHz.

Description: 〈b〉Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube〈/b〉〈br〉 F. Bos, F. Tenholt, J. Becker Tjus, and S. Westerhoff〈br〉 ASTRA Proc., 2, 5-8, https://doi.org/10.5194/ap-2-5-2015, 2015〈br〉 Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: 〈b〉The Local Bubble as a cosmic-ray isotropizer〈/b〉〈br〉 I. Gebauer, M. Weinreuter, S. Kunz, and D. Gaggero〈br〉 ASTRA Proc., 2, 1-3, https://doi.org/10.5194/ap-2-1-2015, 2015〈br〉 The Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can dilute the directional information of energetic positrons and electrons in cosmic rays.

Description: Synchrotron diffuse radiation (SDR) emission is one of the major Galactic components, in the 100 MHz up to 100 GHz frequency range. Its spectrum and sky map provide valuable measure of the galactic cosmic ray electrons (GCRE) in the relevant energy range, as well as of the strength and structure of the Galactic magnetic fields (GMF), both regular and random ones. This emission is an astrophysical sky foreground for the study of the Cosmic Microwave Background (CMB), and the extragalactic microwave measurements, and it needs to be modelled as better as possible. In this regard, in order to get an accurate description of the SDR in the Galaxy, we use – for the first time in this context – 3-dimensional GCRE models obtained by running the DRAGON code. This allows us to account for a realistic spiral arm pattern of the source distribution, demanded to get a self-consistent treatment of all relevant energy losses influencing the final synchrotron spectrum.

Description: The arrival directions of energetic positrons and electrons convey fundamental information on their origin. PAMELA, and more recently AMS, have measured an anomalous population of energetic positrons, which cannot be explained in standard cosmic ray propagation models. Two possible sources have been extensively discussed: astrophysical point sources, such as local pulsars, and dark matter. In the first case an anisotropy in the flux of energetic particles is expected. Reliable predictions of the level of anisotropy need to account for the Sun's peculiar environment: the Sun resides in the so-called Local Bubble, an underdense region, embedded in a dense wall of molecular clouds. This structure is expected to act as an efficient cosmic-ray isotropizer. Using realistic assumptions on the impact of the Local Bubble on cosmic-ray diffusion, we demonstrate that the Local Bubble can indeed dilute the directional information of energetic positrons and electrons.

Description: Recent modelling of solar energetic particles (SEPs) propagation through the heliospheric turbulence, also discussed in this workshop, has investigated the role of the pitch-angle scattering and the perpendicular transport in spreading particles in heliolongitude, as shown by multi-spacecraft measurements (STEREO A/B, ACE, SOHO, etc.) at 1 AU in various energy ranges. In some events the first-order pitch-angle anisotropy of the particles distribution is not-negligible. We calculate the average perpendicular displacement due to the gradient/curvature drift in an inhomogeneous turbulence accounting for pitch-angle dependence for two MHD turbulence models: (a) 3-D isotropic, (b) anisotropic as conjectured by Goldreich-Sridhar. We find in both cases that the drift scales as (1 − μ2)2 with the cosine of pitch-angle μ, in contrast with previous models for transport of SEPs. This result can impact the models of propagation of SEPs through the heliosphere.

Description: It is generally believed that the cosmic ray spectrum below the knee is of Galactic origin, although the exact sources making up the entire cosmic ray energy budget are still unknown. Including effects of magnetic amplification, Supernova Remnants (SNR) could be capable of accelerating cosmic rays up to a few PeV and they represent the only source class with a sufficient non-thermal energy budget to explain the cosmic ray spectrum up to the knee. Now, gamma-ray measurements of SNRs for the first time allow to derive the cosmic ray spectrum at the source, giving us a first idea of the concrete, possible individual contributions to the total cosmic ray spectrum. In this contribution, we use these features as input parameters for propagating cosmic rays from its origin to Earth using GALPROP in order to investigate if these supernova remnants reproduce the cosmic ray spectrum and if supernova remnants in general can be responsible for the observed energy budget.

Description: The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

Description: Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (〉 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Description: The Interstellar Boundary Explorer (IBEX) observes enhanced ~ keV energy Energetic Neutral Atoms (ENAs) from a narrow "ribbon" that stretches across the sky and appears to be centered on the direction of the local interstellar magnetic field. The Milagro collaboration, the Asγ collaboration and the IceCube observatory have made global maps of TeV cosmic rays. This paper provides links between these disparate observations. We develop a simple diffusive model of the propagation of cosmic rays and the associated cosmic ray anisotropy due to cosmic ray streaming against the local interstellar flow. We show that the local plasma and field conditions sampled by IBEX provide characteristics that consistently explain TeV cosmic ray anisotropies. These results support models that place the interstellar magnetic field direction near the center of the IBEX ribbon.

Description: A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum k-5/3 at small scales λ = 2 π/k with k the wave-number, then a saturation spectrum k-1, and finally a shock-dominated spectrum k-2 mostly in the halo/wind outside the Cosmic Ray disk. In an isotropic approximation such a model is consistent with the Interstellar Medium (ISM) data. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.

Description: The measurement of the anisotropy in the cosmic ray (CR) arrival direction distribution provides important informations on the propagation mechanisms and on the identification of their sources. In the last decade the anisotropy came back to the attention of the scientific community, thanks to several new two-dimensional representations of the CR arrival direction distribution which clearly showed the existence of anisotropies at different angular scales in both hemispheres. The origin of the observed anisotropies is still unknown. So far, no theory of CRs in the Galaxy exists yet to explain the observations leaving the standard model of CRs and that of the local magnetic field unchanged at the same time. In this paper the observations of Galactic CR anisotropy will be briefly summarized, with particular attention to the results obtained by the ARGO-YBJ experiment in the Northern Hemisphere.

Description: Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

Description: Various experiments show that the arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It was recently argued that this small scale structure may arise naturally by cosmic ray diffusion in a large-scale cosmic ray gradient in combination with deflections in local turbulent magnetic fields. We show via analytical and numerical methods that the non-trivial power spectrum in this setup is a direct consequence of Liouville's theorem and can be related to properties of relative diffusion.

Description: The large-scale anisotropy (or the so-called star-diurnal wave) has been studied using the calorimeter of the space-born experiment PAMELA. The cosmic ray anisotropy has been obtained for the Southern and Northern hemispheres simultaneously in the equatorial coordinate system for the time period 2006–2014. The dipole amplitude and phase have been measured for energies 1–20 TeV n-1.