Reply to S. Fuselier et al.'s comment on "Energetic particle sounding of the magnetospheric cusp with ISEE-1"

Abstract

In their comment, Fuselier et al. (2008, hereafter FPT) provide an alternative interpretation to the study done by Whitaker et al. (2007, hereafter WFC). WFC concludes that energetic ions observed in the cusp were accelerated locally, while FPT argues that the ions could have been accelerated at the bow shock and then transported to the cusp. The two analyses interpret observations made by the International Sun Earth Explorer (ISEE)-1 on 30 October 1978 as the spacecraft travelled through the high altitude cusp. ISEE-1 observed an area of depressed and turbulent magnetic field as well as increased energetic (>10 keV) ion and electron flux. FPT identifies the quasi-parallel bow shock as the location of particle acceleration. To show this FPT presents a model that traces particles along magnetic field lines from the cusp to the solar wind at the bow shock. This model argues energized particles from the bow shock gain entry to the magnetosphere through low latitude reconnection, propagate along reconnected field lines to the ionosphere, mirror, and return to high latitudes where they are observed flowing anti-parallel to the magnetic field by ISEE-1. We agree with the FPT model to the extent that with these IMF conditions, reconnection opens the cusp to the solar wind plasma, and newly reconnected field lines will convect tailward, but observations do not support particles being energized at the bow shock and transported to the cusp. We present three inconsistencies between the FPT model and the observations made by ISEE-1: (1) the absence of parallel flowing particles, (2)