On the perpendicular scale of electron phase-space holes

Abstract

The perpendicular scale of electron phase-space holes is investigated using electric field data from the Polar Plasma Wave Instrument. We show that the electron phase-space holes are roughly spherical for Ω(e)/ω(p) > 1, and become more oblate (with the perpendicular scale larger than the parallel scale) with decreasing Ω(e)/ω(p). A scaling argument based upon electron gyrokinetic theory is proposed as a possible explanation for the observed scaling. The data indicate that the ratio of the parallel dimension (L(||)) to the perpendicular dimension (L is perpendicular to) is such that L(||)/L(is perpendicular to) κ (1 + ρ(e) 2 /λ(D) 2)(-1/2). Our results provide a connection between the Geotail measurements in the deep magnetotail, where Ω(e)/ω(p) << 1, and the FAST measurements in the low altitude auroral zone, where Ω(e)/ω(p) >> 1.