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  • 1
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    Modulation of galactic cosmic rays during the unusual solar minimum between cycles 23 and 24 (2014)
    Wiley
    Details
    Publication Date: 2014-03-12
    Description: During the recent solar minimum between cycles 23 and 24 (solar minimum P 23/24 ) the intensity of Galactic Cosmic Rays (GCRs) measured at the Earth was the highest ever recorded since space age. It is the purpose of this paper to resolve the most plausible mechanism for this unusually high intensity. A GCR transport model in three-dimensional heliosphere based on a simulation of Markov stochastic process is used to find the relation of cosmic ray modulation to various transport parameters, including solar wind (SW) speed, distance of heliospheric boundary, magnitude of interplanetary magnetic field (IMF) at the Earth, tilt angle of heliospheric current sheet (HCS), values of parallel and perpendicular diffusion coefficients. We calculate GCR proton energy spectra at the Earth for the last three solar minima P 21/22 , P 22/23 , and P 23/24 , with the transport parameters obtained from observations. Besides weak IMF magnitude and slow SW speed, we find that a possible low magnetic turbulence, which increases the parallel diffusion and reduces the perpendicular diffusion in the polar direction, might be an additional possible mechanism for the high GCR intensity in the solar minimum P 23/24 .
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Energetic Charged-Particle Phenomena in the Jovian Magnetosphere: First Results from the Ulysses COSPIN Collaboration (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-09-11
    Description: The Ulysses spacecraft made the first exploration of the region of Jupiter's magnetosphere at high Jovigraphic latitudes ( approximately 37 degrees south) on the dusk side and reached higher magnetic latitudes ( approximately 49 degrees north) on the day side than any previous mission to Jupiter. The cosmic and solar particle investigations (COSPIN) instrumentation achieved a remarkably well integrated set of observations of energetic charged particles in the energy ranges of approximately 1 to 170 megaelectron volts for electrons and 0.3 to 20 megaelectron volts for protons and heavier nuclei. The new findings include (i) an apparent polar cap region in the northern hemisphere in which energetic charged particles following Jovian magnetic field lines may have direct access to the interplanetary medium, (ii) high-energy electron bursts (rise times 〈/= 1 minute and energies extending to 〉 approximately 17 megaelectron volts) on the dusk side that are apparently associated with field-aligned currents and radio burst emissions, (iii) persistence of the global 10-hour relativistic electron "clock" phenomenon throughout Jupiter's magnetosphere, (iv) on the basis of charged-particle measurements, apparent dragging of magnetic field lines at large radii in the dusk sector toward the tail, and (v) consistent outflow of megaelectron volt electrons and large-scale departures from corotation for nucleons.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, J A -- Anglin, J D -- Balogh, A -- Burrows, J R -- Cowley, S W -- Ferrando, P -- Heber, B -- Hynds, R J -- Kunow, H -- Marsden, R G -- McKibben, R B -- Muller-Mellin, R -- Page, D E -- Raviart, A -- Sanderson, T R -- Staines, K -- Wenzel, K P -- Wilson, M D -- Zhang, M -- New York, N.Y. -- Science. 1992 Sep 11;257(5076):1543-50.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17776166" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Cosmic ray and solar particle investigations over the South polar regions of the sun (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-05-19
    Description: Observations of galactic cosmic radiation and anomalous component nuclei with charged particle sensors on the Ulysses spacecraft showed that heliospheric magnetic field structure over the south solar pole does not permit substantially more direct access to the local interstellar cosmic ray spectrum than is possible in the equatorial zone. Fluxes of galactic cosmic rays and the anomalous component increased as a result of latitude gradients by less than 50% from the equator to -80 degrees . Thus, the modulated cosmic ray nucleon, electron, and anomalous component fluxes are nearly spherically symmetric in the inner solar system. The cosmic rays and the anomalous nuclear component underwent a continuous, -26 day recurrent modulation to -80.2 degrees , whereas all recurring magnetic field compressions and recurring streams in the solar wind disappeared above approximately 55 degrees S latitude.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, J A -- Connell, J J -- Lopate, C -- McKibben, R B -- Zhang, M -- Anglin, J D -- Ferrando, P -- Rastoin, C -- Raviart, A -- Heber, B -- Muiller-Meliin, R -- Kunow, H -- Sierks, H -- Wibberenz, G -- Bothmer, V -- Marsden, R G -- Sanderson, T R -- Trattner, K J -- Wenzel, K P -- Paizis, C -- New York, N.Y. -- Science. 1995 May 19;268(5213):1019-23.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17774228" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Ulysses observations of Jupiter's 10 h modulation in interplanetary space in 2004 (2013)
    Wiley
    Details
    Publication Date: 2013-07-04
    Description: [1]  Since the Pioneer 10/11 mission, Jupiter is known as a dominant and almost constant source of MeV electrons in the inner heliosphere. An interesting feature of the Jovian electron source is the fact that Jupiter's rotation period (∼ 10 h) can frequently be recovered in the energy spectrum of Jovian electrons in the vicinity of the planet. However, this modulation has never been convincingly reported to exist beyond ∼ 1 AU away from the planet. In order to search for the 10 h modulation in the heliosphere, we re-examined Ulysses MeV-electron data from the High Energy Telescope (HET) and Kiel Electron Telescope (KET) for the second Jupiter flyby using a Lomb-Scargle spectral analysis. From day 140 to day 147 of 2004, when Ulysses was ∼ 1.2 AU away from the planet at low latitudes during the spacecraft's second flyby, a clear 10 h modulation signature was found when electrons were streaming away from Jupiter. We present data of an event that suggests the presence of the 10 h modulation even at ∼ 2.2 AU.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    An empirical modification of the force field approach to describe the modulation of galactic cosmic rays close to Earth in a broad range of rigidities (2017)
    Wiley
    Details
    Publication Date: 2017-11-07
    Description: On their way through the heliosphere, Galactic Cosmic Rays (GCRs) are modulated by various effects before they can be detected at Earth. This process can be described by the Parker equation, which calculates the phase space distribution of GCRs depending on the main modulation processes: convection, drifts, diffusion and adiabatic energy changes. A first order approximation of this equation is the force field approach, reducing it to a one-parameter dependency, the solar modulation potential ϕ . Utilizing this approach, it is possible to reconstruct ϕ from ground based and spacecraft measurements. However, it has been shown previously that ϕ depends not only on the Local Interstellar Spectrum (LIS) but also on the energy range of interest. We have investigated this energy dependence further, using published proton intensity spectra obtained by PAMELA as well as heavier nuclei measurements from IMP-8 and ACE/CRIS. Our results show severe limitations at lower energies including a strong dependence on the solar magnetic epoch. Based on these findings, we will outline a new tool to describe GCR proton spectra in the energy range from a few hundred MeV to tens of GeV over the last solar cycles. In order to show the importance of our modification, we calculate the global production rates of the cosmogenic radionuclide 10 Be which is a proxy for the solar activity ranging back thousands of years.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    The new Local Interstellar Spectra and Their Influence on the Production Rates of the Cosmogenic Radionuclides 10Be and 14C (2016)
    Wiley
    Details
    Publication Date: 2016-12-07
    Description: With Voyager1 crossing the outer boundary of our solar system at the end of 2012, for the first time in the instrumental era an un-modulated local interstellar spectrum (LIS) at galactic particle energies below ~500 MeV has been measured. On the basis of these as well as PAMELA and AMS02 measurements, most recently three new LIS models have been proposed in the literature. In this study we compare the newest LIS models to previously most often used ones. Thereby, we investigate and discuss the influence of theses LIS models on the terrestrial production rates of the cosmogenic radionuclides 10 Be and 14 C, which are produced due to the interaction of galactic and solar cosmic rays with atmospheric constituents. After being transported within the atmosphere they are preserved in natural archives such as, e.g., ice-sheets or tree rings, forming a unique tool to study the solar modulation of thousands of years back in time. To parameterize the heliospheric modulation we apply the force-field approximation for the individual LIS models from which LIS-dependent solar modulation parameter (φ) values are derived. Furthermore, we present updated sets of linear regression functions containing the opportunity to convert the LIS-dependent φ-values between the investigated LIS models. The results are then applied to a long-term reconstruction of the solar modulation parameter.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 7
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    Wide longitudinal distribution of interplanetary electrons following the 7 February 2010 solar event: Observations and transport modeling (2014)
    Wiley
    Details
    Publication Date: 2014-07-22
    Description: We analyze 65–105 keV electrons in the 7 February 2010 solar electron event observed simultaneously by STEREO-A, STEREO-B, and ACE. A method to reconstruct the full electron pitch angle distributions from the four SEPT sensors on STEREO-A/B and the EPAM instrument on ACE in the energy range of approximately 60–300 keV for periods of incomplete angular coverage is presented. A transport modeling based on numerical solutions of a three-dimensional particle propagation model which includes pitch angle scattering and focused transport is applied to the intensity and anisotropy profiles measured on all three spacecraft. Based on an analysis of intensity gradients observed between the three spacecraft we find that the lateral transport of the electrons occurs partially close to the Sun, due to effects of non-radial divergence of magnetic field lines or particle diffusion, and partially in the interplanetary medium. For the mean free paths characterizing the electron diffusion parallel and perpendicular to the interplanetary magnetic field we derive values of λ ∥  ~ 0.1 AU and λ ⊥  ~ 0.01 AU. In comparison with results from other particle events we had previously analyzed in a similar manner we discuss whether the diffusion mean free paths parallel and perpendicular to the average magnetic field might be related with each other, and whether the particle transport perpendicular to the average magnetic field is more likely due to particles following meandering magnetic field lines, or due to particles being scattered off individual field lines.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 8
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    On‐the‐fly calculation of absorbed and equivalent atmospheric radiation dose in a water phantom with the AtRIS (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Computation of the ionization and radiation dose in arbitrary (exo‐) planetary atmospheres due to energetic particles is recently becoming more important due to several reasons that are either correlated with the detection of trace gases for life on exoplanets or with computing dose rates at arbitrary altitudes in the Earth atmosphere. We previously presented AtRIS, a new Geant4‐based code tailored specifically to enable parametric studies of radiation propagation through exoplanetary atmospheres [Banjac et al., 2019, DOI:10.1029/2018JA026042]. Therein, the calculation of ion‐electron pair production rates, which are a mandatory input for chemical and atmospheric modeling, has been presented and validated against Earth measurements and also other, similar, but solar‐system‐specific Geant4‐based codes (PLANETOCOSMICS). In addition to providing input for atmospheric modeling of exoplanets, with AtRIS we aim to directly characterize the habitability by calculating the absorbed dose. In this technical validation study, after showing a detailed analysis of the secondary particles contributing to the atmospheric radiation, we describe a feature of the code which makes direct parametric studies of the interrelation of incident radiation and the resulting absorbed dose throughout the atmosphere possible. In a validation case study configured using an atmospheric model obtained with NRLMSISE‐00 and a primary proton and helium GCR flux calculated using a recent improvement of the force‐field approach, we have compared simulation results with measurements obtained with the Flight Radiation Environment Detector (FRED). We show that AtRIS can reproduce the measured dose rate dependence on altitude.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Yield Function of the DOSimetry TELescope Count and Dose Rates Aboard the International Space Station (2021)
    Details
    Publication Date: 2021-07-21
    Description: The Earth is constantly hit by energetic particles originating from galactic sources. The flux of these particles is altered by the magnetized solar wind in the heliosphere and the Earth's magnetic field. For this reason, the ability of a particle to approach a spacecraft in low Earth orbit depends on its energy and the position of the spacecraft within the Earth's magnetosphere. Moreover, there are some areas (radiation belts) where the particles are trapped for a long time and, therefore, the flux of energetic particles is particularly high. Occasionally, solar energetic particles contribute to the energetic particle flux too. DOSimetry TELescope (DOSTEL) is one of the instruments aboard the International Space Station (ISS) that monitors the radiation field within the European module Columbus. Because being installed inside the ISS, particles produced by the interaction between the “primary” radiation and the ISS materials are also measured. To describe the observations in such a complex radiation field, we follow the method by Caballero‐Lopez and Moraal (2012, Journal of Geophysical Research, 117[A12], A12103. doi:10.1029/2012JA017794) to compute the so‐called yield function using precise measurements of the proton and helium energy spectra obtained by alpha magnet spectrometer and the systematic variation of the DOSTEL measurements within the Earth's magnetosphere.
    Description: Key Points: Energetic particles Influence of the Earth magnetosphere on the count‐ and dose rate aboard International Space Station (ISS) Yield function
    Description: Bundesministerium Wirtschaft
    Keywords: 629.416 ; energetic particle measurements ; galactic cosmic rays ; yield function
    Type: article
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    CITATION GEO-LEO
  • 10
    Electronic Resource
    Electronic Resource
    ULYSSES observations of energetic particle acceleration and the superposed CME and CIR events of November 1992 (1996)
    Springer
    Annales geophysicae 14 (1996), S. 400-410 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract During November 1992, a series of forward and reverse shocks passed the ULYSSES spacecraft. Spectral and anisotropy measurements are reported for protons and alpha particles between 0.28 and 6 MeV observed by the Energetic Particle Composition Experiment, data recorded by the Magnetometer Experiment and the high-energy (2.7-300 MeV) proton data from the Kiel Electron Telescope. An analysis of energetic particle, plasma and magnetometer data from ULYSSES has allowed a unique study of the corresponding arrival of fare particles, particles within a corotating interaction region and particles transported with a coronal mass ejection. We present an analysis of these data in terms of possible diffusive shock acceleration but conclude that this is likely to be incompatible with the short transit time of the particles. Shock drift acceleration of particles with energies 0.3 MeV/nucleon or solar acceleration followed by particle trapping behind the shock front are alternative possibilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-0400-4
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    Paper (German National Licenses)
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