Storm time observations of plasmasphere erosion flux in the magnetosphere and ionosphere

Plasmasphere erosion carries cold dense plasma of ionospheric origin in a storm‐enhanced density plume extending from dusk toward and through the noontime cusp and dayside magnetopause and back across polar latitudes in a polar tongue of ionization. We examine dusk sector (20 MLT) plasmasphere erosion during the 17 March 2013 storm ( Dst ~ −130 nT) using simultaneous, magnetically aligned direct sunward ion flux observations at high altitude by Van Allen Probes RBSP‐A (at ~3.0 Re) and at ionospheric heights (~840 km) by DMSP F‐18. Plasma erosion occurs at both high and low altitudes where the subauroral polarization stream flow overlaps the outer plasmasphere. At ~20 UT, RBSP‐A observed ~1.2E12 m −2 s −1 erosion flux, while DMSP F‐18 observed ~2E13 m −2 s −1 sunward flux. We find close similarities at high and low altitudes between the erosion plume in both invariant latitude spatial extent and plasma characteristics.