Hollweg, JV;
Verscharen, D;
Chandran, BDG;
(2014)
Magnetohydrodynamic slow mode with drifting He++: implications for coronal seismology and the solar wind.
The Astrophysical Journal
, 788
(1)
, Article 35. 10.1088/0004-637X/788/1/35.
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Abstract
The MHD slow mode wave has application to coronal seismology, MHD turbulence, and the solar wind where it can be produced by parametric instabilities. We consider analytically how a drifting ion species (e.g. He++) affects the linear slow mode wave in a mainly electron-proton plasma, with potential consequences for the aforementioned applications. Our main conclusions are as follows. 1. For wavevectors highly oblique to the magnetic field, we find solutions that are characterized by very small perturbations of total pressure. Thus, our results may help to distinguish the MHD slow mode from kinetic Alfvén waves and non-propagating pressure-balanced structures, which can also have very small total pressure perturbations. 2. For small ion concentrations, there are solutions that are similar to the usual slow mode in an electron-proton plasma, and solutions that are dominated by the drifting ions, but for small drifts the wave modes cannot be simply characterized. 3. Even with zero ion drift, the standard dispersion relation for the highly oblique slow mode cannot be used with the Alfvén speed computed using the summed proton and ion densities, and with the sound speed computed from the summed pressures and densities of all species. 4. The ions can drive a non-resonant instability under certain circumstances. For low plasma beta, the threshold drift can be less than that required to destabilize electromagnetic modes, but damping from the Landau resonance can eliminate this instability altogether, unless Te/Tp ≫ 1.
| Type: | Article |
|---|---|
| Title: | Magnetohydrodynamic slow mode with drifting He++: implications for coronal seismology and the solar wind |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1088/0004-637X/788/1/35 |
| Publisher version: | https://doi.org/10.1088/0004-637X/788/1/35 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | solar wind; Sun: corona; Sun: helioseismology |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10081143 |
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