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Ann. Geophys., 22, 2097-2105, 2004
www.ann-geophys.net/22/2097/2004/
© European Geosciences Union 2004
Pi2-pulsations observed in energetic electron precipitation and magnetic field in association with a substorm surge
A. Åsnes1, J. Stadsnes1, J. Bjordal1, N. Østgaard2,3, D. L. Detrick4, T. J. Rosenberg4, and S. E. Haaland5,6
1Department of Physics, University of Bergen, Allegt. 55, 5007 Bergen, Norway
2NASA/Goddard Space Flight Center, Greenbelt, MD 20771,USA
3University of California, Berkeley, CA94720-7450, USA
4University of Maryland, College Park, MD 20 742–24 331, USA
5International Space Science Institute, Switzerland
6Max-Planck Institut für extraterrestrische Physik (MPE), Garching , Germany
Abstract. For a substorm 24 July 1998 PIXIE observes the onset and expansion during a perigee pass of the Polar
satellite. This gives an opportunity to follow the evolution of the onset and expansion phase, almost
on a global scale with relatively high temporal resolution. The substorm is presented with multiple
observations throughout the magnetosphere. Following the onset of the substorm we observe a localised
region of modulated energetic electron fluxes following the passage of the westward travelling surge
in the pre-midnight region. We count at least six clear pulses with a period of approximately one
minute. Concurrent magnetic ground measurements show similar characteristics, almost simultaneously
with the pulses in precipitation. We propose several possible mechanism for the pulsations, amongst
them the theory of modulated wave particle interaction first proposed by coroniti70.
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