Velocity‐shear‐driven ion‐cyclotron waves and associated transverse ion heating

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Abstract
Recent sounding rocket experiments, such as SCIFER, AMICIST, and ARCS‐4, and satellite data from FAST, Freja, DE‐2, and HILAT, provide compelling evidence of a correlation between small‐scale spatial plasma inhomogeneities, broadband low‐frequency waves, and transversely heated ions. These naturally arising, localized inhomogeneities can lead to sheared cross‐magnetic‐field plasma flows, a situation that has been shown to have potential for instability growth. Experiments performed in the Naval Research Laboratory's Space Physics Simulation Chamber demonstrate that broadband waves in the ion‐cyclotron frequency range can be driven solely by a transverse, localized electric field, without the dissipation of a field‐aligned current. Significant perpendicular ion energization resulting from these waves has been measured. Detailed comparisons with both theoretical predictions and space observations of electrostatic waves found in the presence of sheared cross‐magnetic‐field plasma flow are made.