Torsional alfvén waves in small scale current threads of the solar corona
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Authors
Copil, P.
Voitenko, Y.
Goossens, M.
Discipline
Physical sciences
Subject
Coronal loops
Eigen modes
Hall MHD
In-phase
Magnetic flux tube
Magnetohydrodynamics (MHD)
Magnetohydrodynamics suns
N-waves
Phase speed
Radial direction
Small scale
Solar corona
Sun: corona
Wave dissipation
Wave profiles
Wave spectra
Liquefaction of gases
Magnetic flux
Magnetic structure
Magnetohydrodynamics
Solar radiation
Sun
Tubes (components)
Magnetic fields
Audience
Scientific
Date
2010Metadata
Show full item recordDescription
Context. The magnetic field structuring in the solar corona occurs on large scales (loops and funnels), but also on small scales. For instance, coronal loops are made up of thin strands with different densities and magnetic fields across the loop. Aims. We consider a thin current thread and model it as a magnetic flux tube with twisted magnetic field inside the tube and straight field outside. We prove the existence of trapped Alfvén modes in twisted magnetic flux tubes (current threads) and we calculate the wave profile in the radial direction for two different magnetic twist models. Methods. We used the Hall MHD equations that we linearized in order to derive and solve the eigenmode equation for the torsional Alfvén waves. Results. We show that the trapped Alfv én eigenmodes do exist and are localized in thin current threads where the magnetic field is twisted. The wave spectrum is discrete in phase velocity, and the number of modes is finite and depends on the amount of the magnetic field twist. The phase speeds of the modes are between the minimum of the Alfvén speed in the interior and the exterior Alfén speed. Conclusions. Torsional Alfvén waves can be guided by thin twisted magnetic flux-tubes (current threads) in the solar corona. We suggest that the current threads guiding torsional Alfvén waves, are subject to enhanced plasma heating due to wave dissipation.
Citation
Copil, P.; Voitenko, Y.; Goossens, M. (2010). Torsional alfvén waves in small scale current threads of the solar corona. , Astronomy and Astrophysics, Vol. 510, Issue 1, A17, DOI: 10.1051/0004-6361/200912784.Identifiers
scopus: 2-s2.0-77149130176
Type
Article
Peer-Review
Yes
Language
eng