Bibcode
González-Morales, P. A.; Khomenko, E.; Cally, P. S.
Bibliographical reference
The Astrophysical Journal, Volume 870, Issue 2, article id. 94, 12 pp. (2019).
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1
2019
Journal
Citations
21
Refereed citations
20
Description
Coupling between fast magnetoacoustic and Alfvén waves can be
observed in fully ionized plasmas mediated by stratification and 3D
geometrical effects. In Paper I, Cally & Khomenko have shown that in
a weakly ionized plasma, such as the solar photosphere and chromosphere,
the Hall current introduces a new coupling mechanism. The present study
extends the results from Paper I to the case of warm plasma. We report
on numerical experiments where mode transformation is studied using
quasi-realistic stratification in thermodynamic parameters resembling
the solar atmosphere. This redresses the limitation of the cold plasma
approximation assumed in Paper I, in particular allowing the complete
process of coupling between fast and slow magnetoacoustic modes and
subsequent coupling of the fast mode to the Alfvén mode through
the Hall current. Our results confirm the efficacy of the mechanism
proposed in Paper I for the solar case. We observe that the efficiency
of the transformation is a sensitive function of the angle between the
wave propagation direction and the magnetic field, and of the wave
frequency. The efficiency increases when the field direction and the
wave direction are aligned for increasing wave frequencies. After
scaling our results to typical solar values, the maximum amplitude of
the transformed Alfvén waves, for a frequency of 1 Hz,
corresponds to an energy flux (measured above the height of peak Hall
coupling) of ∼103 W m‑2, based on an
amplitude of 500 m s‑1 at β = 1, which is
sufficient to play a major role in both quiet and active region coronal
heating.
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