Gyrokinetic modelling of the kinetic-ballooning instability in the magnetosphere

Recently, small scale azimuthal structuring in optical signatures associated with low frequency Pc1/2 wave activity has been observed around the time of substorm onset. The characteristic frequency and kinetic-scale structuring have been attributed to the onset of a kinetic ballooning instability, which can occur in high-beta magnetized plasmas in regions where the magnetic curvature and pressure gradient are in opposite directions. We present recent progress on electromagnetic gyrokinetic simulations of the ballooning instability in a realistic stretched dipole geometry to examine the properties of the instability and compare with optical and wave signatures observed at substorm onset.