Study of Auroral Electron Acceleration in the Laboratory

Particle interactions with Alfv\'en waves have been proposed as a possible means for accelerating electrons and generating aurorae. Auroral theory states that electron acceleration by inertial Alfv\'en waves varies with the perpendicular wavenumber and Alfv\'en wave amplitude. Traditional diagnostics are not sensitive to the predicted small fluctuations of populations in the tail of the distribution function. A novel approach accurately measures this region of the distribution function using the absorption of a small-amplitude high frequency whistler wave. Inertial Alfv\'en waves ($v_{\mbox{th}}/v_A \sim 0.2$) with $\delta B/B \sim 10^{-5}$ are launched in an overdense plasma at the Large Plasma Device (LaPD) with $B=1800$ G. Under these conditions, only the whistler mode propagates parallel to the background field at frequencies just below the electron cyclotron frequency. Initial results show the dielectric perturbation of the distribution function by an Alfv\'en wave. We present further analysis of measurements of the electron distribution function under plasma conditions relevant to the auroral magnetosphere using a range of Alfv\'en wave parameters and compare results to theoretical predictions.