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Titolo:
Evolution of magnetic field fluctuations in high-speed solar wind streams:Ulysses and Helios observations
Autore:
Horbury, TS; Balogh, A;
Indirizzi:
Imperial Coll, Blackett Lab, London SW7 2BW, England Imperial Coll London England SW7 2BW ackett Lab, London SW7 2BW, England Univ London Queen Mary & Westfield Coll, Astron Unit, London E1 4NS, England Univ London Queen Mary & Westfield Coll London England E1 4NS S, England
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A8, volume: 106, anno: 2001,
pagine: 15929 - 15940
SICI:
0148-0227(20010801)106:A8<15929:EOMFFI>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
GALACTIC COSMIC-RAYS; RADIAL EVOLUTION; MAGNETOHYDRODYNAMIC TURBULENCE; PLASMA OBSERVATIONS; INNER HELIOSPHERE; MINIMUM-VARIANCE; ANISOTROPY; POLE; DEPENDENCE; LATITUDES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Horbury, TS Imperial Coll, Blackett Lab, London SW7 2BW, England Imperial Coll London England SW7 2BW London SW7 2BW, England
Citazione:
T.S. Horbury e A. Balogh, "Evolution of magnetic field fluctuations in high-speed solar wind streams:Ulysses and Helios observations", J GEO R-S P, 106(A8), 2001, pp. 15929-15940

Abstract

Ulysses magnetic field measurements in high-speed streams emanating from the Sun's polar coronal holes reveal a complex combination of fluctuations on different scales. Measurements of the wavenumber dependence of radial andlatitudinal power scaling, spectral index, and anisotropy of undisturbed polar magnetic field fluctuations between 1.4 and 4.1 astronomical units (AU) are presented. These results confirm earlier work and reveal the presenceof three populations: structures at large scales, Alfven waves at intermediate scales, and turbulent fluctuations at the smallest scales. A significant decrease in power with latitude, as a result of overexpansion of polar coronal holes, has consequences for energetic particle diffusion coefficients. Other results, in particular those related to field magnitude variations, are not well understood at this time. A similar analysis of magnetic field fluctuations in high-speed streams at low heliolatitudes between 0.3 and 1 AU, measured by the Hellos spacecraft, shows consistency with Ulysses measurements, suggesting a common origin for fluctuations in ail high-speed streams.

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Documento generato il 29/09/20 alle ore 00:46:33