CORONAL SEISMOLOGY USING EIT WAVES: ESTIMATION OF THE CORONAL MAGNETIC FIELD STRENGTH IN THE QUIET SUN |
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Matthew West Submitted: 2011-03-14 09:34
Coronal EIT waves have been observed for many years. The nature of EITwaves is still contentious, however, there is strong evidence thatsome of them might be fast magnetosonic waves, or at least have a fastmagnetosonic wave component. The fast magnetosonic wave speed isformed from two components; the Alfvén speed (magnetic) and the soundspeed (thermal). By making measurements of the wave speed, coronaldensity and temperature it is possible to calculate the quiet-Suncoronal magnetic field strength through coronal seismology. In thispaper, we investigate an EIT wave observed on 2009 February 13 by theSECCHI/EUVI instruments on board the STEREO satellites. The waveepicenter was observed at disk center in the STEREO B (Behind)satellite. At this time, the STEREO satellites were separated byapproximately 90°, and as a consequence the STEREO A (Ahead)satellite observed the wave on the solar limb. These observationsallowed us to make accurate speed measurements of the wave. Thebackground coronal density was derived throughHinode/Extreme-ultraviolet Imaging Spectrometer observations of thequiet Sun and the temperature was estimated through the narrowtemperature response in the EUVI bandpasses. The density, temperature,and speed measurements allowed us to estimate the quiet-Sun coronalmagnetic field strength to be approximately 0.7 ± 0.7 G.
Authors: M. J. West, A. N. Zhukov, L. Dolla, and L. Rodriguez
Projects: STEREO
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Publication Status: published
Last Modified: 2011-03-14 23:35
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