Theoretical Prediction of Sunquake Waves 

Dr. J.J. Podesta
NASA/GSFC
Seminar March 18, 2005.

ABSTRACT:

The propagation of ring waves across the surface of the sun in response to a flare 
initiated sunquake is modeled using Euler's equations of fluid dynamics. The solar 
convection zone is modeled as a plane parallel gas layer in hydrostatic equilibrium with 
an adiabatic temperature gradient. Small amplitude perturbations about this equilibrium 
state are described by the linearized Euler equations for an inviscid compressible fluid 
(the actual convective motions on the sun are neglected for the purpose of calculating the 
wave motions). The normal modes of oscillation of this solar model, which can be 
expressed in terms of generalized Laguerre polynomials, are used to construct the 
solution of an initial value problem for the linearized equations of motion. Assuming that 
the form of the initial velocity pulse is Gaussian, the solutions for the vertical velocity at 
the solar surface are computed as a function of time and compared to the observational 
data for the sunquake event of 9 July 1996. Model calculations of the position of the 
wave packet as a function of time predict arrival times that are a few minutes ahead of the 
observations (1 to 5 minutes) for the range of distances between 10 and 120 Mm from the 
point of impact or, equivalently, for the range of times between 15 and 50 minutes after 
the assumed time of impact of the flare ejecta (or shock wave) on the solar surface. It is 
concluded that the model is in good agreement with the observational data with an error 
of roughly 10% or 20%.