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GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 21, PAGES 4071–4074, 1998

The Seasonal Variation of Auroral Ion Beams

H. L. Collin

Lockheed Martin ATC, Palo Alto, CA 94304, USA.

W. K. Peterson

Lockheed Martin ATC, Palo Alto, CA 94304, USA.

O. W. Lennartsson

Lockheed Martin ATC, Palo Alto, CA 94304, USA.

J. F. Drake

Lockheed Martin ATC, Palo Alto, CA 94304, USA.

Abstract

We present observations of a seasonal variation in the occurrence frequency of upflowing ions beams near 1 R_E altitude in the 1800-2400 local time sector. These observations were obtained from the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) instrument during POLAR satellite perigee passes from March 1996 to September 1997. We show that the observed variation is most simply interpreted as a variation in the magnitude of the auroral acceleration process responsible for creating upflowing ion beams and precipitating energetic electrons. These observations, the first to find a seasonal effect in the occurence of ion beams, also confirm previous reports which examined related phenomena and provide further evidence that changes in ionospheric conductivity have a measurable effect in the strength of the interaction between the Earth’s magnetosphere and ionosphere.

Received 17 July 1998; accepted 22 September 1998.

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Citation: Collin, H. L., W. K. Peterson, O. W. Lennartsson, and J. F. Drake (1998), The Seasonal Variation of Auroral Ion Beams, Geophys. Res. Lett., 25(21), 4071–4074.

Copyright 1998 by the American Geophysical Union.