Jahn, J.-M.,
Co-Authors: G D Reeves, R Friedel, M G Henderson, M Walt, S J Lev-Tov, H D Voss, and J B Blake,
Title: Loss of Energetic Protons in Earth's Inner Magnetosphere as Measured with POLAR.,
Reference: AGU Spring Meeting, Boston, MA, May 26-29, 1998.
Reference Type: Contributed Talk
CEPPAD: true
CAMMICE: false
RAPID: false
Abstract:
Pitch angle diffusion is one of the two major processes responsible for the loss of trapped energetic ions in earth's inner magnetosphere. It changes the location of particle mirror points through violation of one or more adiabatic invariants. If the mirror points are driven into the loss cone the particles can get lost in the dense low-altitude atmosphere. The CEPPAD Source/loss-cone Energetic Particle Spectrometer (SEPS) on the POLAR satellite is ideally suited to measure this particle loss. Solid-state detector arrays located on the despun platform of the satellite provide continuous measurements of the magnetic field aligned ion loss cone region with high spatial resolution. We use these SEPS measurements to first establish quiet-time proton pitch angle distributions for angles $\leq 25 \deg$ as a function of local time and L-shell. We compare these measurements with theoretically expected distributions in the loss cone region. During magnetically quiet times the particle loss is typically dominated by the charge exchange of energetic ions with low-energy neutral atoms of earth's exosphere. Based on this quiet-time database we go on to examine examples of loss cone pitch angle distributions associated with the enhanced levels of magnetic activity and plasma waves during geomagnetic storm periods. We compare and contrast SEPS measurements with data from other instruments flown on the POLAR spacecraft.
