The theory of ballooning perturbations in the inner magnetosphere of the Earth Original Research Article

The low-frequency magnetohydrodynamic waves in the inner magnetosphere of the Earth have been studied using the set of equations of small oscillations obtained in the ballooning approximation from the ideal magnetohydrodynamic equations and the dipole model of the geomagnetic field. This set describes both small-scale and large-scale perturbations in the magnetospheric plasma. In the “cold” plasma approximation, these equations describe toroidal and poloidal shear Alfvén waves. The influence of pressure leads to the appearance of the small-scale slow magnetosonic waves, which are coupled with the poloidal shear Alfvén waves. The stability of the poloidal shear Alfvén waves has been analyzed. They are unstable at large values of pressure gradient.