Quasi-periodic emissions (15–[formula omitted]) from the poles of Jupiter as a principal source of the large-scale high-latitude magnetopause boundary layer of energetic particle

Abstract

In this study, we concentrate on the examination of the quasi-periodic behavior of 0.5–1.6MeV(∼40–400keV) protons (electrons) and of relativistic (>16MeV) electrons, observed at Jupiter by two different experiments onboard Ulysses, the HI-SCALE and COSPIN, respectively, within the large-scale south duskside magnetopause boundary layer (MPBL) of energetic particles, from ∼20:00UT, day 41, to 12:00UT, day 43. During those times, the observations confirm the transition of Ulysses to an important magnetospheric region with particle intensities comparable to the magnetodisk levels. A careful analysis of high time-resolution intensity, anisotropy and spectral measurements suggests the following: (1) The quasi-periodic ∼40min (QP-40) energetic electron (>∼40keV) and proton (>∼0.5MeV) emissions from the south pole were a characteristic phenomenon in the south duskside MPBL; an almost continuous QP 40-min variation has been confirmed in energetic electron observations. (2) When the QP-40 modulation was not evident in energetic particle intensities, it was still detectable in spectral and anisotropy observations. (3) The QP-40 emission is a principal, but not the only periodic, energetic electron and proton emission; other periodicities (∼15,∼20,∼30,∼50,∼60,∼80min) were also significant in energetic particle spectral and anisotropy observations. We infer that QP-40 emissions along with other periodic emissions (∼15,∼20,∼30,∼50,∼60,∼80min) were the principal source of the large-scale high-latitude MPBL of energetic particles during Ulysses outbound pass of Jupiter.