Issue |
A&A
Volume 376, Number 1, September II 2001
|
|
---|---|---|
Page(s) | 292 - 301 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20010972 | |
Published online | 15 September 2001 |
Oscillations in an active region filament: Observations and comparison with MHD waves
Institut d'Astrophysique Spatiale, Unité Mixte CNRS-Université Paris XI, bâtiment 121, 91405 Orsay Cedex, France
Corresponding author: S. Régnier, stephane.regnier@ias.u-psud.fr
Received:
13
October
2000
Accepted:
18
June
2001
During the MEDOC Campaign 4, on October 1999, observations of a solar active
region filament were carried out by the SUMER/SoHO spectrometer. A time
sequence of this filament has been obtained with a duration of 7 h 30 min and
with a temporal resolution of 30 s. The Fourier analysis of the line-of-sight
Doppler velocities measured in the 584.33 Å HeI line allows us to detect
oscillations in several ranges of periodicities (short periods: less
than 5 min, intermediate periods: 6-20 min, and long periods: greater than 40
min). From a theoretical
point of view, we consider the possible modes of oscillations of an active
region filament. Following [CITE], we treat the filament as a plasma
slab embedded in a uniform magnetic field inclined at an angle ϕ to the
long axis of the slab. Solving the dispersion equations for Alfvén waves and
magnetoacoustic waves, primary and secondary mode frequencies appear to be
non-equidistant.
For the comparison between the observed and
calculated frequencies, we outline an identification method of the oscillation
modes in the observed filament. This
identification provides a diagnostic of the filament: the angle
between the magnetic field and the long axis of the slab is estimated to be 18°, and
the magnetic field strength B (G) is proportional to the square root of the
density (
) in the slab,
.
Key words: Sun: filaments / Sun: oscillations / MHD / waves
© ESO, 2001
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.