Influence of ionospheric conductivity on the ballooning modes in the inner magnetosphere of the Earth

The generation of ballooning perturbations in the inner magnetosphere of the Earth was investigated in the dipole model of the geomagnetic field taking into account the ionospheric boundary conditions. The ionosphere is considered as a thin layer with finite conductivity. A special attention was paid to the study of the influence of ionospheric conductivity on the stability of ballooning perturbations. It was demonstrated that in the case of insulating ionosphere, flute perturbations are generated and they determine the stability of magnetospheric magnetohydrodynamic modes. An analytical stability criterion was obtained for these perturbations. Conforming to the results of the paper (Hameiri, E., Ballooning modes on open magnetic field lines. Phys. Plasmas 6(3), 674–685, 1999), it also determines the stability boundary of magnetospheric magnetohydrodynamic perturbations in the resistive boundary case. In the case of resistive ionosphere, stable toroidal Alfvén waves are slowly decaying. The spectrum of coupled poloidal Alfvén and slow magnetosonic eigenmodes was also investigated for perfectly conductive ionosphere.