ALBERT

Beschreibung: zit. bei Park et al. (1987), ähnlich zu deren Verfahren, allerdings Anwendung auf Magnetometer Daten.

Beschreibung: Leakage of ions from the magnetosphere into the magnetosheath remains an important topic in understanding the plasma physics of Earth's magnetopause and the interaction of the solar wind with the magnetosphere. Here, using sophisticated instrumentation from two spacecraft (RBSPICE on the van Allen Probes and EIS on the MMS) spaced uniquely near and outside the dayside magnetopause, we are able to determine the escape mechanisms for large gyroradii oxygen ions and much smaller gyroradii hydrogen and helium ions. The oxygen ions are entrained on the magnetosphere boundary while the hydrogen and helium ions appear to escape along reconnected field lines. These results have important implications for not only Earth's magnetosphere, but also other solar system magnetospheres.

Beschreibung: We report, for the first time, an auroral undulation event on 1 May 2013 observed by an all-sky imager (ASI) at Athabasca ( L = 4.6), Canada, for which in situ field and particle measurements in the conjugate magnetosphere were available from a Van Allen Probes spacecraft. The ASI observed a train of auroral undulation structures emerging spontaneously in the pre-midnight subauroral ionosphere, during the growth phase of a substorm. The undulations had an azimuthal wavelength of ~180 km and propagated westward at a speed of 3–4 km s −1 . The successive passage over an observing point yielded quasi-periodic oscillations in diffuse auroral emissions with a period of ~40 s. The azimuthal wave number m of the auroral luminosity oscillations was found to be m ~ −103. During the event the spacecraft – being on tailward stretched field lines ~0.5 R E outside the plasmapause that mapped into the ionosphere conjugate to the auroral undulations – encountered intense poloidal ULF oscillations in the magnetic and electric fields. We identify the field oscillations to be the second harmonic mode along the magnetic field line through comparisons of the observed wave properties with theoretical predictions. The field oscillations were accompanied by oscillations in proton and electron fluxes. Most interestingly, both field and particle oscillations at the spacecraft had one-to-one association with the auroral luminosity oscillations around its footprint. Our findings strongly suggest that this auroral undulation event is closely linked to the generation of second harmonic poloidal waves.

Beschreibung: Magnetotail processes and structures related to substorm growth phase/onset auroral arcs remain poorly understood mostly due to the lack of adequate observations. In this study we make a comparison between ground-based optical measurements of the premidnight growth phase/onset arcs at subauroral latitudes and magnetically conjugate measurements made by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe-B (RBSP-B) spacecraft crossing L values of ~5.0–5.6 in the premidnight inner tail region. The conjugate observations offer a unique opportunity to examine the detailed features of the arc location relative to large-scale Birkeland currents and of the magnetospheric counterpart. Our main findings include (1) At the early stage of the growth phase the quiet auroral arc emerged ~4.3° equatorward of the boundary between the downward Region-2 (R2) and upward Region-1 (R1) currents; (2) Shortly before the auroral breakup (poleward auroral expansion) the latitudinal separation between the arc and the R1/R2 demarcation narrowed to ~1.0°; (3) RBSP-B observed a magnetic field signature of a local upward field-aligned current (FAC) connecting the arc with the near-Earth tail when the spacecraft footprint was very close to the arc; and (4) The upward FAC signature was located on the tailward side of a local plasma pressure increase confined near L ~5.2–5.4. These findings strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via the local upward FAC.

Beschreibung: Abstract Ion transport from the plasma sheet to the ring current is the main cause of the development of the ring current. Energetic (〉150 keV) ring current ions are known to be transported diffusively in several days. A recent study suggested that energetic oxygen ions are transported closer to the Earth than protons due to the diffusive transport caused by a combination of the drift and drift‐bounce resonances with Pc 3–5 ultralow frequency waves during the 24 April 2013 magnetic storm. To understand the occurrence conditions of such selective oxygen increase (SOI), we investigate the phase space densities (PSDs) between protons and oxygen ions with the first adiabatic invariants (μ) of 0.1–2.0 keV/nT measured by the Radiation Belt Storm Probes Ion Composition Experiment instrument on the Van Allen Probes at L ~ 3–6 during 90 magnetic storms in 2013–2017. We identified the SOI events in which oxygen PSDs increase while proton PSDs do not increase during a period of ~9 hr (one orbital period). Among the 90 magnetic storms, 33% were accompanied by the SOI events. Global enhancements of Pc 4 and Pc 5 waves observed by ground magnetometers during the SOI events suggest that radial transport due to combination of the drift‐bounce resonance with Pc 4 oscillations and the drift resonance with Pc 5 oscillations can be the cause of SOIs. The contribution of the SOI events to the magnetic storm intensity is roughly estimated to be ~9% on average.

Beschreibung: Energetic particle transport into the inner magnetosphere during geomagnetic storms is responsible for significant plasma pressure enhancement, which is the driver of large-scale currents that control the global electrodynamics within the magnetosphere-ionosphere system. Therefore, understanding the transport of plasma from the tail deep into the near-Earth magnetosphere, as well as the energization processes associated with this transport, is essential for a comprehensive knowledge of the near-Earth space environment. During the main phase of a geomagnetic storm on March 17 th 2013 (minimum Dst ~ −137 nT), the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on the Van Allen Probes observed frequent, small-scale proton injections deep into the inner nightside magnetosphere in the region L  ~ 4 – 6. Although isolated injections have been previously reported inside geosynchronous orbit, the large number of small-scale injections observed in this event suggests that, during geomagnetic storms injections provide a robust mechanism for transporting energetic ions deep into the inner magnetosphere. In order to understand the role that these injections play in the ring current dynamics, we determine the following properties for each injection: i) associated pressure enhancement, ii) the time duration of this enhancement, iii) and the lowest and highest energy channels exhibiting a sharp increase in their intensities. Based on these properties, we estimate the effect of these small-scale injections on the pressure buildup during the storm. We find that this mode of transport could make a substantial contribution to the total energy gain in the storm-time inner magnetosphere.

Beschreibung: 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〉

Beschreibung: 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〉

Beschreibung: 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〉

Beschreibung: At Venus the Energetic Particles Detector (EPD) on the Galileo spacecraft measured the differential energy spectra and angular distributions of ions 〉22 kiloelectron volts (keV) and electrons 〉 15 keV in energy. The only time particles were observed by EPD was in a series of episodic events [0546 to 0638 universal time (UT)] near closest approach (0559:03 UT). Angular distributions were highly anisotropic, ordered by the magnetic field, and showed ions arriving from the hemisphere containing Venus and its bow shock. The spectra showed a power law form with intensities observed into the 120- to 280-keV range. Comparisons with model bow shock calculations show that these energetic ions are associated with the venusian foreshock-bow shock region. Shock-drift acceleration in the venusian bow shock seems the most likely process responsible for the observed ions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Williams, D J -- McEntire, R W -- Krimigis, S M -- Roelof, E C -- Jaskulek, S -- Tossman, B -- Wilken, B -- Studemann, W -- Armstrong, T P -- Fritz, T A -- Lanzerotti, L J -- Roederer, J G -- New York, N.Y. -- Science. 1991 Sep 27;253(5027):1525-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17784094" target="_blank"〉PubMed〈/a〉