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Titolo:
Evolution and dissipation of imbedded rotational discontinuities and Alfven waves in nonuniform plasma and the resultant proton heating
Autore:
Vasquez, BJ; Hollweg, JV;
Indirizzi:
Univ New Hampshire, Ctr Space Sci, Inst Study Earth Oceans & Space, Durham, NH 03824 USA Univ New Hampshire Durham NH USA 03824 eans & Space, Durham, NH 03824 USA
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
fascicolo: A4, volume: 106, anno: 2001,
pagine: 5661 - 5681
SICI:
0148-0227(20010401)106:A4<5661:EADOIR>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
MAGNETIC-FLUX TUBES; COMPRESSIBLE MAGNETOHYDRODYNAMIC TURBULENCE; SOLAR-WIND; CORONAL HOLES; LOW-FREQUENCY; VELOCITY DISTRIBUTIONS; NUMERICAL-SIMULATION; RESONANCE-ABSORPTION; SURFACE-WAVES; ACCELERATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
82
Recensione:
Indirizzi per estratti:
Indirizzo: Vasquez, BJ Univ New Hampshire, Ctr Space Sci, Inst Study Earth Oceans & Space, Durham, NH 03824 USA Univ New Hampshire Durham NH USA 03824 , Durham, NH 03824 USA
Citazione:
B.J. Vasquez e J.V. Hollweg, "Evolution and dissipation of imbedded rotational discontinuities and Alfven waves in nonuniform plasma and the resultant proton heating", J GEO R-S P, 106(A4), 2001, pp. 5661-5681

Abstract

We show that nonuniform Alfven speed gradients across field lines generally arise from the evolution of Alfven waves. The evolution of a group of nonlinear Alfven waves with the same sign of parallel wavenumber generate small amplitude pressure-balanced structures (PBSs) which cause the speed variations. This always causes refraction. In most cases, the Alfven waves also couple to magnetosonic waves and acquire a weak compressional component andcan undergo resonant absorption or transfer, wherein wave energy can propagate across field lines. At large amplitudes the waves also generate imbedded rotational discontinuities (RDs). Some of these RDs can be dissipated owing to resonant transfer. This process could partly contribute to the observed decrease of solar wind RDs with increasing distance from the Sun. Resonant transfer also triggers a cascade due to steepening, which leads to sustained proton heating. The cascade produces oblique and large wavenumber waves which travel in different directions and have associated compressions. Protons interact with these by pitch angle scattering. They gain energy fromsecond-order Fermi acceleration and from Landau and transit time damping. Oblique waves are inferred to be present in the dissipation range of Alfvenic fluctuations at 1 AU. We argue that the process of proton heating shouldproceed similarly to simulation results. We also propose a role for the wave imbedded RD in coronal heating through its formation in the chromosphereand its likely dissolution in the corona where wave amplitudes are very small.

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Documento generato il 02/04/20 alle ore 21:07:31