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| Titel |
From Alfvén waves to kinetic Alfvén waves in an inhomogeneous equilibrium structure |
| VerfasserIn |
Francesco Pucci, Christian L. Vasconez, Oreste Pezzi, Sergio Servidio, Francesco Valentini, William H. Matthaeus, Francesco Malara |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135340
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| Publikation (Nr.) |
 EGU/EGU2016-16195.pdf |
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| Zusammenfassung |
| Kinetic Alfvén waves are believed to primary form fluctuations in a hydromagnetic
turbulence at scales of the order of the ion inertial length. We study a model where an initial
Alfvén wave propagates inside an equilibrium structure which is inhomogeneous in the
direction perpendicular to the equilibrium magnetic field. In a previous paper [1]
this situation has been considered in a particular configuration where the initial
wavevector is parallel to the magnetic field and the wave is polarized perpendicular
to the inhomogeneity direction. Here, we consider other configurations, with a
different polarization and possible initial oblique propagation. We employ numerical
simulations, using both a Hall-Magnetohydrodynamics and a Hybrid Vlasov-Maxwell
model.
Results show that in all the considered cases the time evolution leads to the formation of
Kinetic Alfvén waves within the inhomogeneity regions, which are identified by a
comparison with analytical linear theory results. Then, in this context the formation of
Kinetic Alfvén waves seems to be a general phenomenon which could be also extended to
more complex situations, like turbulence. Kinetic simulations show that Kinetic Alfvén
waves modify the ion distribution function, generating temperature anisotropy of both
parallel and perpendicular to the local magnetic field as well as particle beams aligned along
the local magnetic field. These results could be relevant both in the solar corona and in
large-scale structures of the solar wind, where Alfvénic fluctuations are present along with
large-scale inhomogeneities.
[1] C. Vasconez et al., Kinetic Alfvén waves generation by large-scale phase-mixing, The
Astrophysical Journal 815.1, 7 (2015). |
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