Propagation model for MHD waves in the low solar corona

CASTRO, JOSÉ IGNACIO; FRANCILE, C.N.; BALMACEDA, L. A. ;

Mar del Plata

Conferencia; 55ª Reunión Anual de la Asociación Argentina de Astronomía; 2012

Uchida's model, under the WKB approximation, explains Moreton waves (visible in images taken in the H-alpha spectral line of the solar chromosphere) as an effect on the chromosphere related to a MHD wavefront (fast magneto-sonic mode) propagating in the coronal plasma. Usually, this shock wave is driven by a dynamic process such as a flare or a CME. In the model of Uchida, Moreton waves accelerate as they propagate, but observations and measurements of them reveal a deceleration of the waves that disagree with the theoretical results. This indicates that Uchida's model or its WKB approximation (or both) might be incorrect. In our work we analyze the model of Uchida and the propagation of MHD waves in a low beta-p coronal plasma. Considering impulsive processes close to the solar chromosphere, the curvature effects can be neglected and the problem can be described using Cartesian coordinates. The calculation technique is based on the Fermat's principle.