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Titolo:
Electron heating and phase space signatures at supercritical, fast mode shocks
Autore:
Hull, AJ; Scudder, JD; Larson, DE; Lin, R;
Indirizzi:
Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA Univ Calif Berkeley Berkeley CA USA 94720 Sci Lab, Berkeley, CA 94720 USA Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA Univ Iowa Iowa City IA USA 52242 t Phys & Astron, Iowa City, IA 52242 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A8, volume: 106, anno: 2001,
pagine: 15711 - 15733
SICI:
0148-0227(20010801)106:A8<15711:EHAPSS>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
EARTHS BOW SHOCK; QUASI-PERPENDICULAR SHOCKS; COLLISIONLESS SHOCKS; RESOLVED LAYER; HIGH-BETA; PLASMA; INSTABILITY; MECHANISM; FIELDS; WAVES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Hull, AJ Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA Univ Calif Berkeley Berkeley CA USA 94720 Berkeley, CA 94720 USA
Citazione:
A.J. Hull et al., "Electron heating and phase space signatures at supercritical, fast mode shocks", J GEO R-S P, 106(A8), 2001, pp. 15711-15733

Abstract

We investigate the effect of the nonmonotonic features of the macroscopic magnetic field B(x) and the deHoffmann-Teller frame electrostatic potentialPhi (HT)(x) the electron distribution functions within collisionless, fastmode shocks. The Signatures of electron distribution functions are explored by using Liouville's theorem in the adiabatic approximation to map model upstream and downstream boundary electron velocity distribution functions to regions inside model shocks with monotonic and nonmonotonic magnetic fields under the empirically motivated approximation that delta Phi (HT) proportional to deltaB. In the case of shocks with monotonically increasing magnetic fields, we show that there are no "exclusion" regions and that the electron distribution function at all pitch angles and hence the electron temperature increase can be explained by the reversible behavior of magnetized electrons in the shock macroscopic electric and magnetic fields. However, atshocks with nonmonotonic magnetic fields, there exist regions of inaccessibility which are outside the domain of the one-Dimensional (1-D), steady state Vlasov-Liouville (V-L) approach as defined by the upstream and downstream boundaries. Such regions, if occupied, may be filled by electrons scattered into these regions by waves, or perhaps by reversible processes such asthe adiabatic convection of electrons into these regions of a curved bow shock, or by coherent nonadiabatic access. As a further test, the V-L methodis employed to study, for the first time, the detailed signatures of full 3-D electron velocity distribution functions observed by the Wind spacecraft through the resolved layer of a supercritical, fast mode Earth bow shock crossing. We demonstrate that much of the complex structure of the observedelectron distribution function within the shock layer can be explained by the motion of adiabatic electrons in the nonmonotonic shock macroscopic magnetic and electric fields. However, a significant portion of electron phasespace appears to be the remnants of electron phase space holes. The mechanisms responsible for allowing electrons to gain access to the exclusion regions are not well understood and may have important implications on the thermodynamic properties of collisionless shocks.

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Documento generato il 15/07/20 alle ore 05:35:17