Issue |
A&A
Volume 516, June-July 2010
|
|
---|---|---|
Article Number | A84 | |
Number of page(s) | 8 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361/200913874 | |
Published online | 20 July 2010 |
Instability of twisted magnetic tubes with axial mass flows
1
Space Research Institute, Austrian Academy of Sciences, Graz, Austria e-mail: teimuraz.zaqarashvili@oeaw.ac.at
2
Abastumani Astrophysical Observatory at Ilia State University, Kazbegi ave. 2a, Tbilisi, Georgia
3
Departament de Física, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain e-mail: [toni.diaz;ramon.oliver;dfsjlb0]@uib.es
Received:
15
December
2009
Accepted:
16
March
2010
Context. Recent observations of various kinds of jets in the solar atmosphere motivate studying the influence of mass flow on the stability of solar magnetic structures.
Aims. We study the influence of axial mass flows on the stability of twisted magnetic flux tubes.
Methods. We use the incompressible magnetohydrodynamic equations to get the dispersion relation governing the behaviour of normal modes in uniformly twisted magnetic tubes with sub-Alfvénic flows. The dispersion relation is then solved analytically and numerically to find stability criteria for twisted tubes with flow.
Results. Two main important results are found. First, the axial mass flow reduces the threshold of kink instability in twisted magnetic tubes. Second, the twist of magnetic tubes leads to the Kelvin-Helmholtz instability of sub-Alfvénic flows for the harmonics with a large enough azimuthal wave number –m.
Conclusions. The observed mass flow may trigger the kink instability in magnetic configurations that are near their stability threshold, leading to solar flares and coronal mass ejections. The effect is more significant for photospheric magnetic tubes than for coronal ones. Sub-Alfvénic flows undergo the Kelvin-Helmholtz instability in slightly twisted magnetic tubes if the azimuthal wavenumber is big enough.
Key words: magnetohydrodynamics (MHD) / instabilities / Sun: atmosphere
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.