ALBERT

Description: Author(s): L. Berger, R. F. Wimmer-Schweingruber, and G. Gloeckler The small amount of heavy ions in the highly rarefied solar wind are sensitive tracers for plasma-physics processes, which are usually not accessible in the laboratory. We have analyzed differential streaming between heavy ions and protons in the solar wind at 1 AU. 3D velocity vector and magnetic ... [Phys. Rev. Lett. 106, 151103] Published Thu Apr 14, 2011

Description: In the last decade a significant discovery has been made in the heliosphere: the spectrum of particles accelerated in both the inner heliosphere and in the heliosheath is the same: a power law in particle speed with a spectral index of -5, when the spectrum is expressed as a distribution function; or equivalently, a differential intensity spectrum that is a power law in energy with a spectral index of -1.5. In the inner heliosphere this common spectrum occurs at quite low energies and is most evident in instruments designed to measure suprathermal particles. In the heliosheath, the common spectrum is observed over the full energy range of the Voyager energetic particle instruments, up to energies of ~100 MeV. The remarkable discovery of a common spectrum is compounded by the realization that no traditional acceleration mechanism, i.e. diffusive shock acceleration or stochastic acceleration, can account for the common spectrum. There is thus an opportunity to once again demonstrate the relevance of heliospheric physics by developing a new acceleration mechanism that yields the common spectrum, with the expectation that such a new acceleration mechanism will find broader applications in astrophysics. In this paper, the observations of the common spectrum in the heliosphere are summarized, with emphasis on those that best reveal the conditions in which the acceleration must operate. Then, building on earlier work, a complete derivation is presented of an acceleration mechanism, a pump acceleration mechanism, that yields the common spectrum, and the various subtleties associated with this derivation are discussed.

Description: For instruments that use time-of-flight techniques to measure space plasma, there are common sources of background signals that evidence themselves in the data. The background from these sources may increase the complexity of data analysis and reduce the signal-to-noise response of the instrument, thereby diminishing the science value or usefulness of the data. This paper reviews several sources of background commonly found in time-of-flight mass spectrometers and illustrates their effect in actual data using examples from ACE-SWICS and MESSENGER-FIPS. Sources include penetrating particles and radiation, UV photons, energy straggling and angular scattering, electron stimulated desorption of ions, ion-induced electron emission, accidental coincidence events, and noise signatures from instrument electronics. Data signatures of these sources are shown, as well as mitigation strategies and design considerations for future instruments.

Description: The Voyager 1 spacecraft is currently in the vicinity of the heliopause, which separates the heliosphere from the local interstellar medium. There has been a precipitous decrease in particles accelerated in the heliosphere, and a substantial increase in galactic cosmic rays (GCRs). The evidence is unclear, however, as to whether Voyager 1 has crossed the heliopause into the local interstellar medium, or remains within the heliosheath. In this Letter we propose a test that will determine whether Voyager 1 has crossed the heliopause: If Voyager 1 remains in the heliosheath, the high densities observed must be due to compressed solar wind, with the consequence that Voyager 1 will encounter another current sheet, where the polarity of the magnetic field reverses. Voyager 1 observations can be used to predict that the next current sheet crossing is likely to occur during 2015.

Description: Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, E J -- Marsden, R G -- Balogh, A -- Gloeckler, G -- Geiss, J -- McComas, D J -- McKibben, R B -- MacDowall, R J -- Lanzerotti, L J -- Krupp, N -- Krueger, H -- Landgraf, M -- New York, N.Y. -- Science. 2003 Nov 14;302(5648):1165-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14615526" target="_blank"〉PubMed〈/a〉

Description: The low-energy charged particle (LECP) instrument on Voyager 2 measured within the magnetosphere of Neptune energetic electrons (22 kiloelectron volts 〈/= E 〈/= 20 megaelectron volts) and ions (28 keV 〈/= E 〈/= 150 MeV) in several energy channels, including compositional information at higher (〉/=0.5 MeV per nucleon) energies, using an array of solid-state detectors in various configurations. The results obtained so far may be summarized as follows: (i) A variety of intensity, spectral, and anisotropy features suggest that the satellite Triton is important in controlling the outer regions of the Neptunian magnetosphere. These features include the absence of higher energy (〉/=150 keV) ions or electrons outside 14.4 R(N) (where R(N) = radius of Neptune), a relative peak in the spectral index of low-energy electrons at Triton's radial distance, and a change of the proton spectrum from a power law with gamma 〉/= 3.8 outside, to a hot Maxwellian (kT [unknown] 55 keV) inside the satellite's orbit. (ii) Intensities decrease sharply at all energies near the time of closest approach, the decreases being most extended in time at the highest energies, reminiscent of a spacecraft's traversal of Earth's polar regions at low altitudes; simultaneously, several spikes of spectrally soft electrons and protons were seen (power input approximately 5 x 10(-4) ergs cm(-2) s(-1)) suggestive of auroral processes at Neptune. (iii) Composition measurements revealed the presence of H, H(2), and He(4), with relative abundances of 1300:1:0.1, suggesting a Neptunian ionospheric source for the trapped particle population. (iv) Plasma pressures at E 〉/= 28 keV are maximum at the magnetic equator with beta approximately 0.2, suggestive of a relatively empty magnetosphere, similar to that of Uranus. (v) A potential signature of satellite 1989N1 was seen, both inbound and outbound; other possible signatures of the moons and rings are evident in the data but cannot be positively identified in the absence of an accurate magnetic-field model close to the planet. Other results indude the absence of upstream ion increases or energetic neutrals [particle intensity (j) 〈 2.8 x 10(-3) cm(-2) s(-1) keV(-1) near 35 keV, at approximately 40 R(N)] implying an upper limit to the volume-averaged atomic H density at R 〈/= 6 R(N) of 〈/= 20 cm(-3); and an estimate of the rate of darkening of methane ice at the location of 1989N1 ranging from approximately 10(5) years (1-micrometer depth) to approximately 2 x 10(6) years (10-micrometers depth). Finally, the electron fluxes at the orbit of Triton represent a power input of approximately 10(9) W into its atmosphere, apparently accounting for the observed ultraviolet auroral emission; by contrast, the precipitating electron (〉22 keV) input on Neptune is approximately 3 x 10(7) W, surprisingly small when compared to energy input into the atmosphere of Jupiter, Saturn, and Uranus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krimigis, S M -- Armstrong, T P -- Axford, W I -- Bostrom, C O -- Cheng, A F -- Gloeckler, G -- Hamilton, D C -- Keath, E P -- Lanzerotti, L J -- Mauk, B H -- Van Allen, J A -- New York, N.Y. -- Science. 1989 Dec 15;246(4936):1483-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17756004" target="_blank"〉PubMed〈/a〉

Description: Broad regions on both sides of the solar wind termination shock are populated by high intensities of non-thermal ions and electrons. The pre-shock particles in the solar wind have been measured by the spacecraft Voyager 1 (refs 1-5) and Voyager 2 (refs 3, 6). The post-shock particles in the heliosheath have also been measured by Voyager 1 (refs 3-5). It was not clear, however, what effect these particles might have on the physics of the shock transition until Voyager 2 crossed the shock on 31 August-1 September 2007 (refs 7-9). Unlike Voyager 1, Voyager 2 is making plasma measurements. Data from the plasma and magnetic field instruments on Voyager 2 indicate that non-thermal ion distributions probably have key roles in mediating dynamical processes at the termination shock and in the heliosheath. Here we report that intensities of low-energy ions measured by Voyager 2 produce non-thermal partial ion pressures in the heliosheath that are comparable to (or exceed) both the thermal plasma pressures and the scalar magnetic field pressures. We conclude that these ions are the 〉0.028 MeV portion of the non-thermal ion distribution that determines the termination shock structure and the acceleration of which extracts a large fraction of bulk-flow kinetic energy from the incident solar wind.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Decker, R B -- Krimigis, S M -- Roelof, E C -- Hill, M E -- Armstrong, T P -- Gloeckler, G -- Hamilton, D C -- Lanzerotti, L J -- England -- Nature. 2008 Jul 3;454(7200):67-70. doi: 10.1038/nature07030.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA. robert.decker@jhuapl.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18596801" target="_blank"〉PubMed〈/a〉

Description: Observations by MESSENGER show that Mercury's magnetosphere is immersed in a comet-like cloud of planetary ions. The most abundant, Na+, is broadly distributed but exhibits flux maxima in the magnetosheath, where the local plasma flow speed is high, and near the spacecraft's closest approach, where atmospheric density should peak. The magnetic field showed reconnection signatures in the form of flux transfer events, azimuthal rotations consistent with Kelvin-Helmholtz waves along the magnetopause, and extensive ultralow-frequency wave activity. Two outbound current sheet boundaries were observed, across which the magnetic field decreased in a manner suggestive of a double magnetopause. The separation of these current layers, comparable to the gyro-radius of a Na+ pickup ion entering the magnetosphere after being accelerated in the magnetosheath, may indicate a planetary ion boundary layer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slavin, James A -- Acuna, Mario H -- Anderson, Brian J -- Baker, Daniel N -- Benna, Mehdi -- Gloeckler, George -- Gold, Robert E -- Ho, George C -- Killen, Rosemary M -- Korth, Haje -- Krimigis, Stamatios M -- McNutt, Ralph L Jr -- Nittler, Larry R -- Raines, Jim M -- Schriver, David -- Solomon, Sean C -- Starr, Richard D -- Travnicek, Pavel -- Zurbuchen, Thomas H -- New York, N.Y. -- Science. 2008 Jul 4;321(5885):85-9. doi: 10.1126/science.1159040.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. james.a.slavin@nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18599776" target="_blank"〉PubMed〈/a〉

Description: The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 +/- 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 +/- 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zurbuchen, Thomas H -- Raines, Jim M -- Gloeckler, George -- Krimigis, Stamatios M -- Slavin, James A -- Koehn, Patrick L -- Killen, Rosemary M -- Sprague, Ann L -- McNutt, Ralph L Jr -- Solomon, Sean C -- New York, N.Y. -- Science. 2008 Jul 4;321(5885):90-2. doi: 10.1126/science.1159314.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. thomasz@umich.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18599777" target="_blank"〉PubMed〈/a〉

Description: The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space called the heliosphere. The recently launched Interstellar Boundary Explorer (IBEX) spacecraft has completed its first all-sky maps of the interstellar interaction at the edge of the heliosphere by imaging energetic neutral atoms (ENAs) emanating from this region. We found a bright ribbon of ENA emission, unpredicted by prior models or theories, that may be ordered by the local interstellar magnetic field interacting with the heliosphere. This ribbon is superposed on globally distributed flux variations ordered by both the solar wind structure and the direction of motion through the interstellar medium. Our results indicate that the external galactic environment strongly imprints the heliosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McComas, D J -- Allegrini, F -- Bochsler, P -- Bzowski, M -- Christian, E R -- Crew, G B -- DeMajistre, R -- Fahr, H -- Fichtner, H -- Frisch, P C -- Funsten, H O -- Fuselier, S A -- Gloeckler, G -- Gruntman, M -- Heerikhuisen, J -- Izmodenov, V -- Janzen, P -- Knappenberger, P -- Krimigis, S -- Kucharek, H -- Lee, M -- Livadiotis, G -- Livi, S -- MacDowall, R J -- Mitchell, D -- Mobius, E -- Moore, T -- Pogorelov, N V -- Reisenfeld, D -- Roelof, E -- Saul, L -- Schwadron, N A -- Valek, P W -- Vanderspek, R -- Wurz, P -- Zank, G P -- New York, N.Y. -- Science. 2009 Nov 13;326(5955):959-62. doi: 10.1126/science.1180906. Epub 2009 Oct 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Southwest Research Institute, San Antonio, TX 78228, USA. dmccomas@swri.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19833923" target="_blank"〉PubMed〈/a〉