Solar rotation period driving modulation of plasmaspheric convection

Using Van Allen Probes data, we present the first in situ observations of convective processes in the inner-magnetosphere being driven at the solar rotation period ( 27 days) and harmonics. Analysis of the cold plasma density and electric fields in the inner-magnetosphere show intervals of strong solar rotation period modulation of the plasmapause location ( 1RE peak-to-peak), cold plasma density ( 250 cm-3 peak-to-peak), and large scale electric field ( 0.3 mV/m peak-to-peak) at L = 2.5 - 5.0. To identify the controlling factor, the periodicities in these quantities are compared to solar EUV Lyman Ha emissions, solar wind velocity, solar wind dawn-dusk electric field, and the Kp index. Results indicate that the 27-day periodicity in convective driving is due to geoeffective conditions in the solar wind passing over earth with the same periodicity. This effect becomes more prominent in the declining phase of the solar cycle. Unlike studies of the ionospheric variability, the plasmaspheric density often anti-correlates at the solar rotation period with the solar EUV. Variations in the plasmapause location at the solar rotation period anti-correlate with solar wind electric field, magnetospheric electric field, and Kp index, indicating that convective erosion is the dominate physical process controlling the plasmapause at these timescales.