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Titolo:
A tale of two theories: How the adiabatic response and ULF waves affect relativistic electrons
Autore:
Green, JC; Kivelson, MG;
Indirizzi:
Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA Univ Calif Los Angeles Los Angeles CA USA 90095 Los Angeles, CA 90095 USA Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA Univ Calif Los Angeles Los Angeles CA USA 90095 Los Angeles, CA 90095 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A11, volume: 106, anno: 2001,
pagine: 25777 - 25791
SICI:
0148-0227(20011101)106:A11<25777:ATOTTH>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
RADIATION-BELT; ENERGETIC ELECTRONS; MAGNETIC STORM; SALAMMBO CODE; SOLAR-WIND; ACCELERATION; DIFFUSION; MAGNETOSPHERE; SIMULATIONS; INJECTIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Green, JC Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA Univ Calif Los Angeles Los Angeles CA USA 90095 s, CA 90095 USA
Citazione:
J.C. Green e M.G. Kivelson, "A tale of two theories: How the adiabatic response and ULF waves affect relativistic electrons", J GEO R-S P, 106(A11), 2001, pp. 25777-25791

Abstract

Using data from the Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD)-High Sensitivity Telescope (HIST) instrument on the Polar spacecraft and ground magnetometer data from the 210 meridian magnetometer chain, we test the ULF wave drift resonance theory proposed to explain relativistic electron phase space density enhancements. We begin by investigating changes in electron flux due to the "Dst effect. " The Dst effect refers to the adiabatic response of relativistic electrons to changes in the magnetic field characterized by the Dst index. The Dst effect, assuming no loss or addition of new electrons, produces reversible order of magnitude changes in relativistic electrons flux measured at fixed energy, but it cannot account for the flux enhancement that occurs in the recovery phase of most storms. Liouville's theorem states that phase space density expressed in terms of constant adiabatic invariants is unaffected by adiabatic field changesand thus is insensitive to the Dst effect. It is therefore useful to express flux measurements in terms of phase space densities at constant first, second and third adiabatic invariants. The phase space density is determinedfrom the CEPPAD-HIST electron detector that measures differential directional flux of electrons from 0.7 to 9 MeV and the Tsyganenko 96 field model. The analysis is done for January to June 1997. The ULF wave drift resonancetheory that we test proposes that relativistic electrons are accelerated by an m=2 toroidal or poloidal mode wave whose frequency equals the drift frequency of the electron. The theory is tested by comparing the relativisticelectron phase space densities to wave power determined at three ground stations with L* values of 4.0, 5.7 and 6.2. Comparison of the wave data to the phase space densities shows that five out of nine storm events are consistent with the ULF wave drift resonance mechanism, three out of nine give ambiguous support to the model, and one event has high ULF wave power at thedrift frequency of the electrons but no corresponding phase space density enhancement suggesting that ULF wave power alone is not sufficient to causean electron response. Two explanations of the anomalous event are investigated including excessive loss of electrons to the magnetopause and wave duration.

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Documento generato il 06/04/20 alle ore 04:05:13