Energetic charged particle angular distributions near (r ≤ 2 RN) and over the pole of Neptune

Abstract

Energetic ion ( > 28 keV) and electron ( > 22 keV) pitch angle distributions very close to (r ≤ 2RN) and over the north planetary pole of Neptune are presented using data from the Low Energy Charged Particle (LECP) and magnetometer (MAG) Experiments on the Voyager 2 spacecraft. The particle data are temporally structured and spectrally soft; a similarity with Earth‐like auroral signatures has previously been noted. However, the pitch angle distributions (showing trapped distributions at high magnetic latitudes) do not support an Earth‐like auroral interpretation, and alternative explanations for the temporal dynamics must be sought. Between r ∼ 1.6 and 2.0 RN and in the vicinity of the magnetic equator, the higher energy ion and electron pitch angle distributions (E ≥ 80 keV) display dramatic “bite‐outs” at ∼90°. This bite‐out feature could be caused by interactions with the newly discovered ring 1989N3R.