TITLE

Slow EIT waves as gravity modes

AUTHOR(S)
Vranjes, J.
PUB. DATE
June 2011
SOURCE
Physics of Plasmas;Jun2011, Vol. 18 Issue 6, p062902
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The EIT waves [named after the extreme-ultraviolet imaging telescope (EIT) onboard the solar and heliospheric observatory (SOHO)] are in the literature usually described as fast magneto-acoustic (FMA) modes. However, observations show that a large percentage of these events propagate with very slow speeds that may be as low as 20 km/s. This is far below the FMA wave speed which cannot be below the sound speed, the latter being typically larger than 102 km/s in the corona. In the present study, it is shown that, to account for such low propagation speed, a different wave model should be used, based on the theory of gravity waves, both internal (IG) and surface (SG) ones. The gravity modes are physically completely different from the FMA mode, as they are essentially dispersive and in addition the IG wave is a transverse mode. Both the IG and the SG mode separately can provide proper propagation velocities in the whole low speed range.
ACCESSION #
62010262

 

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