The magnetic cataclysmic variable AE Aquarii hosts a rapidly rotating white
dwarf which is thought to expel most of the material streaming onto it.
Observations of AE Aqr have been obtained in the wavelength range of 5 - 70
microns with the IRS, IRAC, and MIPS instruments on board the Spitzer Space
Telescope. The spectral energy distribution reveals a significant excess above
the K4V spectrum of the donor star with the flux increasing with wavelength
above 12.5 microns. Superposed on the energy distribution are several hydrogen
emission lines, identified as Pf alpha and Hu alpha, beta, gamma. The infrared
spectrum above 12.5 microns can be interpreted as synchrotron emission from
electrons accelerated to a power-law distribution dN=E^{-2.4}dE in expanding
clouds with an initial evolution timescale in seconds. However, too many
components must then be superposed to explain satisfactorily both the
mid-infrared continuum and the observed radio variability. Thermal emission
from cold circumbinary material can contribute, but it requires a disk
temperature profile intermediate between that produced by local viscous
dissipation in the disk and that characteristic of a passively irradiated disk.
Future high-time resolution observations spanning the optical to radio regime
could shed light on the acceleration process and the subsequent particle
evolution.Comment: 15 pages, 3 figures, accepted for publication in Ap