Chorus Wave Properties From Van Allen Probes: Quantifying the Impact of the Sheath Corrected Electric Field
Abstract
A sheath impedance model has recently been developed to describe how the variable coupling impedance between the Van Allen Probes instrumentation and the ambient plasma affects both the amplitude and phase of electric field wave measurements. Here, the impact of this sheath correction on measured chorus wave properties, including electric field wave power and the Poynting vector, is directly quantified.
It is found that the sheath-corrected electric field wave power is typically between two and nine times larger than the uncorrected measurement, depending on wave frequency. The sheath correction typically increases the Poynting flux by a factor of similar to 2, and causes the polar angle of the Poynting vector to switch hemisphere from parallel to anti-parallel propagation in similar to 2% of cases.
The uncorrected data exhibit significant deviations from the theoretically predicted relationship between the wave vector and the Poynting vector whereas this relationship is well-reproduced with the sheath-corrected observations.