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Titolo:
Energy spectra of 50-keV to 20-MeV protons accelerated at corotating interaction regions at Ulysses
Autore:
Desai, MI; Marsden, RG; Sanderson, TR; Lario, D; Roelof, EC; Simnett, GM; Gosling, JT; Balogh, A; Forsyth, RJ;
Indirizzi:
Univ Maryland, Dept Phys, MI Desai Space Phys Grp, College Pk, MD 20742 USA Univ Maryland College Pk MD USA 20742 Phys Grp, College Pk, MD 20742 USA Europeandspace Agcy, Estec, Dept Space Sci, NL-2200 AZ Noordwijk, Netherlan European Space Agcy Noordwijk Netherlands NL-2200 AZ oordwijk, Netherlan Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA Johns Hopkins Univ Laurel MD USA 20723 ppl Phys Lab, Laurel, MD 20723 USA Univ,Birmingham, Sch Astrophys & Space Phys, Birmingham B15 2TT, W Midlands Univ Birmingham Birmingham W Midlands England B15 2TT B15 2TT, W Midlands Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA Univ Calif Los Alamos Natl Lab Los Alamos NM USA 87545 amos, NM 87545 USA UnivrLondon Imperial Coll Sci Technol & Med, Blackett Lab, Space & Atmosphe Univ London Imperial Coll Sci Technol & Med London England SW7 2BZ osphe
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A4, volume: 104, anno: 1999,
pagine: 6705 - 6719
SICI:
0148-0227(19990401)104:A4<6705:ESO5T2>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
ROTATING INTERACTION REGIONS; DIFFUSIVE SHOCK ACCELERATION; IONS OBSERVED UPSTREAM; SOLAR-WIND STREAM; SOUTH POLAR PASS; EARTHS BOW SHOCK; INTERPLANETARY SHOCKS; PARTICLE-ACCELERATION; SPATIAL VARIATION; ECLIPTIC-PLANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
61
Recensione:
Indirizzi per estratti:
Indirizzo: Desai, MI Univ Maryland, Dept Phys, MI Desai Space Phys Grp, College Pk, MD 20742 USA Univ Maryland College Pk MD USA 20742 College Pk, MD 20742 USA
Citazione:
M.I. Desai et al., "Energy spectra of 50-keV to 20-MeV protons accelerated at corotating interaction regions at Ulysses", J GEO R-S P, 104(A4), 1999, pp. 6705-6719

Abstract

We analyze here the energy spectra of 50-keV to 20-MeV protons acceleratedat corotating shocks observed at Ulysses in the southern heliosphere during 1992 and 1993. In general, our results are inconsistent with the predictions of two models based on diffusive shock acceleration theory (Fisk and Lee [1980] and Jones and Ellison [1991]). The main results are the following:(1) The relationships between the spectral indices and the shock compression ratio show significant departures from those predicted by the two models; the observed spectra are substantially harder than predicted; (2) the spectral indices at the reverse shocks depend strongly on the heliographic latitude of Ulysses; the hardest spectra are associated with strong quasi-perpendicular shocks observed between 20 degrees S and 30 degrees S; (3) the spectral indices at the reverse shocks are anticorrelated with the upstream plasma velocity V-u' in the de Hoffman-Teller frame of the shock; and (4) the spectral indices at the forward shocks show no dependence on either the shock parameters or the heliographic latitude. The latitudinal dependence ofthe reverse shock spectra is probably related to the tilt (similar to 25 degrees) of the heliospheric current sheet with respect to the solar equatorial plane during 1992 and 1993. The negative correlation between the spectral indices at the reverse shocks and V-u' indicates that the gradient driftmechanism plays a crucial role in accelerating particles at corotating interaction regions (CIRs). The differences in our observations at the forwardand reverse shocks may be due to the presence of a more energetic seed population and an enhancement in the level of magnetic field fluctuations upstream of the trailing edges of the CIRs.

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Documento generato il 03/12/20 alle ore 16:02:16