Ionospheric mass ejection in response to a CME

T. E. Moore,¹ W. K. Peterson,² C. T. Russell,³ M. O. Chandler,⁴ M. R. Collier,¹ H. L. Collin,² P. D. Craven, ⁴
R. Fitzenreiter,¹ B. L. Giles,¹ and C. J. Pollock⁵

Received January 16, 1999, revised April 28, 1999, accepted May 14, 1999

Abstract:

We report observations of a direct ionospheric plasma outflow response to the incidence of an interplanetary shock and associated coronal mass ejection (CME) upon the earth's magnetosphere. Data from the WIND spacecraft, 185 upstream, document the passage of an interplanetary shock at 23:20 UT on 24 Sept. 1998. The polar cap plasma environment sampled by the POLAR spacecraft changed abruptly at 23:45 UT, reflecting the compressional displacement of the geopause relative to the spacecraft. POLAR left the polar wind outflow region and entered the mantle flows. Descending toward the dayside cusp region, POLAR later returned from the mantle to an enhanced polar wind flux dominated by O plasma and eventually containing molecular ions. The enhanced and O- dominated outflow continued as the spacecraft passed through the high altitude cleft and then the southern cleft at lower altitude. Such a direct response of the ionosphere to solar wind dynamic pressure disturbances may have important impacts on magnetospheric dynamics.

¹NASA GSFC, Greenbelt, MD, USA.
²LMATC, Palo Alto, CA, USA.
³ESS, U. of CA, Los Angeles, CA, USA.
⁴NASA MSFC, Huntsville, AL, USA.
⁵SwRI, San Antonio, TX, USA.

© 1999 by the American Geophysical Union.
Paper number 1999GL900456.

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