Frequency‐Drifting Plasmaspheric Hiss: A Statistical Study From the Van Allen Probes Data

Abstract

AbstractPlasmaspheric hiss, a whistler‐mode emission confined in the high‐density plasmasphere, is of great interest to the space community attributed to its important role in inner magnetospheric dynamics. Their frequency‐time structures provide crucial evidence for understanding the wave origin. In this work, based on ∼7‐year Van Allen Probes data, we statistically studied the frequency‐drifting plasmaspheric hiss characterized by an increasing lower cutoff frequency over a timescale exceeding 1 hr. Frequency‐drifting hiss waves predominantly occur at 3 < L < 6 from predawn to noon during geomagnetic active times. Observations and theoretical analyses suggest the frequency‐drifting hiss could result from the local excitation inside the plasmasphere by energy‐dispersive injected electrons. This unique feature of plasmaspheric hiss waves serves, to a certain extent, as an “identifier” for discerning the wave origins and as a “marker” facilitating the link between hiss waves across a broad spatial range.