We present optical and X-ray time-series photometry of EI UMa that reveal modulation at 746 and 770 s, which we interpret as the white dwarf spin and spin-orbit sidebands. These detections, combined with previous X-ray studies, establish EI UMa as an intermediate polar. We estimate the mass accretion rate to be ~ 3.6 x 10^{17} g s^{-1}, which is close to, and likely greater than, the critical rate above which dwarf nova instabilities are suppressed. We also estimate the white dwarf to have a large magnetic moment mu > (3.4 +/- 0.2) x 10^{33} G cm^3. The high mass accretion rate and magnetic moment imply the existence of an accretion ring rather than a disk, and along with the relatively long orbital period, these suggest that EI UMa is a rare example of a pre-polar cataclysmic variable.

We compare Mars Global Surveyor (MGS) magnetometer/electron reflectometer data with results from a B field–dependent kinetic transport code for “superthermal” electrons. The photoelectrons created on crustal field loops, when they are on the dayside, allow for the exploration of the magnetic topology and the upper atmospheric density structure. A case study of a typical orbit of the MGS satellite through the strong crustal field region in the southern hemisphere of Mars is examined. The results indicate that the low solar wind dynamic pressure during the selected orbit allowed for the expansion of the crustal field line to relatively high altitudes. Another feature of the photoelectrons in the crustal field region is that the distribution at high energies ( E > 100 eV) is far more isotropic than what is expected from collisional scattering processes alone. Several candidate processes are discussed that might be preferentially scattering high‐energy electrons. A final conclusion is that a two‐stream model is inadequate for effectively examining photoelectron pitch angle distributions at Mars in the presence of the crustal fields.