ALBERT

Description: The frequencies and amplitudes of inner magnetosphere Pi2 waves are affected by the radial plasma density profile. Variable geomagnetic activity and external driving conditions can affect both wave properties and density profiles simultaneously. When interpreting observations, this can lead to ambiguity about whether changing wave properties are due to changing external conditions, density profiles, or a combination of factors. We present a case study using multi-point ground-based and in situ measurements to examine Pi2 wave properties during a period of variable geomagnetic activity. Multiple satellite passes demonstrate the density profile and plasmapause location is stable for at least two hours over a wide range of MLT. This stability allows us to examine how factors besides the radial density profile affect Pi2 wave properties. We find evidence for Pi2 waves with a broadband frequency spectrum as well as a discrete frequency plasmaspheric virtual resonance (PVR) that is observed at low, mid, and high-latitudes and both inside and outside the plasmapause. The PVR is excited in repeated bursts before, during and after (1) the development of a substorm, (2) several auroral intensifications, (3) the development of Sub-Auroral Polarization Stream (SAPS) flows/electric fields/conductivities, and (4) variable Interplanetary Magnetic Field (IMF) conditions. Through all these changes the PVR frequency remains remarkably stable (8.2 +/− 0.53 mHz, based on low latitude ground magnetometer observations), suggesting these variations have little effect on the frequency. This is consistent with PVR model predictions for a stationary plasmapause.