Solar atmospheric magnetic effects on global acoustic and atmospheric gravity eigenoscillations

Solar global observations suggest that the frequency and the line width of helioseismic acoustic eigenmodes vary with the solar cycle. One reason for the measured changes could be the variation of the global atmospheric magnetic fields. We model global solar oscillations in a plane-parallel, three-layer model within the framework of linear dissipative magnetohydrodynamics, and study the effects of a homogenous, horizontal atmospheric magnetic field on global oscillations. We find magnetoacoustic f- and p-modes and also atmospheric gravity modes (g-modes) among the eigenoscillations of the system. We conclude that changes in the atmospheric magnetic field can, significantly, shift the frequencies and vary the line width of global oscillation modes.