57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015;
Savannah, Georgia
Session YI3: Eruptions and Jets
9:30 AM–12:30 PM,
Friday, November 20, 2015
Room: Oglethorpe Auditorium
Chair: Auna Moser, General Atomics
Abstract ID: BAPS.2015.DPP.YI3.6
Abstract: YI3.00006 : Laboratory Measurements of Linear Electron Acceleration by Inertial Alfv\'en Waves*
12:00 PM–12:30 PM
Preview Abstract
Abstract
Author:
J.W.R. Schroeder
(University of Iowa)
Alfv\'en waves occur in conjunction with a significant fraction of
auroral electron acceleration [1]. Inertial mode Alfv\'en waves ($v_A >
v_{te}$) in the auroral magnetosphere ($2-4 R_E$) with
perpendicular scales on the order of the electron skin depth
($c/\omega_{pe}$) have a parallel electric field that, according to
theory, is capable of nonlinearly accelerating suprathermal electrons
to auroral energies [2]. Unfortunately, due to space-time ambiguities of
rocket and satellite measurements, it has not yet been possible to
fully verify how Alfv\'en waves contribute to the production of accelerated electrons. To
overcome the limitations of \emph{in situ} spacecraft data, laboratory experiments have
been carried out using the Large Plasma Device (LaPD), an NSF/DOE user
facility at UCLA. An Electron Cyclotron Absorption (ECA) diagnostic
has been developed to record the suprathermal parallel electron
distribution function with 0.1\% precision [3].
The diagnostic records the electron distribution while inertial Alfv\'en waves simultaneously
propagate through the plasma. Recent measurements have isolated
oscillations of suprathermal electrons at the Alfv\'en wave
frequency. Despite complications from boundary effects and the finite
size of the experiment, a linear kinetic model has been produced that
describes the experimental results. To our knowledge this is the first
quantitative agreement between the measured and modeled linear
response of suprathermal electrons to an inertial Alfv\'en wave. This
verification of the linear physics is a necessary step before the
nonlinear acceleration process can be isolated in future
experiments. Presently, nonlinear effects cannot be detected because
of limited Alfv\'en wave amplitudes. Ongoing work is focused on
designing a higher-power antenna capable of efficiently launching
larger-amplitude Alfv\'en waves with tunable perpendicular wavenumber
and developing a theoretical
understanding of the nonlinear acceleration process in LaPD plasma
conditions.\\[4pt]
[1] C. C. Chaston \emph{et. al.}, Geophys. Res. Lett. 34, L07101 (2007).\\[0pt]
[2] C. A. Kletzing, J. Geophys. Res. 99, 11095--11104 (1994).\\[0pt]
[3] D. J. Thuecks, F. Skiff, and C. A. Kletzing, Rev. Sci. Instrum. 83, 083503 (2012).
*This material is based upon work supported by the National Science Foundation under Grants No. 1048957, PHY-10033446, and CAREER AGS-1054061. This work was performed in collaboration with F. Skiff, C. A. Kletzing, G. G. Howes, T. A. Carter, and S. Dorfman.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.YI3.6