The Global Morphology of Wave Poynting Flux: Powering the Aurora
A. Keiling,1*
J. R. Wygant,1
C. A. Cattell,1
F. S. Mozer,2
C. T. Russell3
Large-scale, electric currents flowing along magnetic field lines
into the polar regions of Earth are thought to be the main contributors
of the energy that powers the ionospheric aurora. However, we have
found evidence for global contributions from electromagnetic waves
(Alfvén waves). Data that were collected from the Polar
spacecraft over the course of 1 year show that the flow of wave
electromagnetic energy at altitudes of 25,000 to 38,000 kilometers
delineates the statistical auroral oval. The Poynting flux of
individual events distributed along the auroral oval was larger than 5 ergs per square centimeter per second, which is sufficient to power
auroral acceleration processes. This evidence suggests that in addition
to magnetic field-aligned currents, the dayside and nightside aurora is
globally powered by the energy flow of these high-altitude Alfvén
waves.
1 Department of Physics and Astronomy,
University of Minnesota, Minneapolis, MN 55144, USA.
2 Space Science Laboratory, University of
California, Berkeley, CA 94720, USA.
3 Institute of
Geophysics and Planetary Physics, University of California, Los
Angeles, CA 90024, USA.
*
Present address: Centre d'Etude Spatiale des Rayonnements,
Toulouse, France.
To whom correspondence should be addressed. E-mail:
akeiling{at}ham.space.umn.edu
