Physics – Plasma Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh33a1823d&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SH33A-1823
Physics
Plasma Physics
[7507] Solar Physics, Astrophysics, And Astronomy / Chromosphere, [7867] Space Plasma Physics / Wave/Particle Interactions
Scientific paper
The chromospheric and coronal plasmas of the solar atmosphere are much hotter than the visible photosphere. The heating mechanisms in these regions, however, have not yet been fully understood. Alfven waves have long been considered to play a crucial role in heating of plasmas, and numerous theoretical and experimental papers have been published to investigate resonant heating of ions by Alfven waves. In these works, the cyclotron resonant condition is necessary for ion heating by the Alfven waves, and in general the frequencies of the applied Alfven waves are comparable to the cyclotron frequency. However, the heating of ions by low-frequency Alfven waves and related problems have triggered great interest in recent years. Among these works, various simulation and theoretical methods, such as test particle approach with analytic solutions, hybrid simulations, and kinetic theory, have been used to validate the heating mechanism by low-frequency Alfven wave interactions. Evidence of ion heating by low-frequency Alfven waves has also been found in laboratory experiments and observations. In this paper we demonstrate that the low-frequency Alfven waves propagating along the background magnetic field can heat ions even in the partially ionized chromosphere. The heating process in the present work is due to a randomization of the spatial velocity distribution in the ion population, which is caused by non-resonant Alfven wave interactions. We find that this heating process becomes less efficient than the situation with no ion-neutral collisions. Another interesting result of ion-neutral collisions is that the velocity distribution of the ions becomes a ring after a period of time during the heating process, which demonstrates that a balance is eventually achieved between the energy loss due to collisions with neutrals and the energy obtained from the Alfven waves. Moreover, we determine that the heating process is only effective for low-beta plasmas and Alfven wave frequencies lower than 0.6 Hz; the most efficient heating occurs when Alfven wave frequencies lower than 0.01 Hz. Additionally, our heating mechanism is strongly supported by the recent observations of large amplitude, low frequency Alfven waves in the solar chromosphere by the Hinode satellite.
Dong Cailing
Paty Carol S.
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