J.-H. Shue, P. Song, C. T. Russell, J. T. Steinberg, J. K. Chao

The magnetic cloud on January 6-11, 1997 might be the cause of a malfunction and the following loss of Telstar-401 satellite at 1115 UT on January 11. During this event, around 0200 UT on January 11, there was a sudden enhancement in the solar wind dynamic pressure to more 25 times of its normal value. The interplanetary magnetic field was extremely strong and northward (~18 nT). During the pressure enhancement, the Geotail in the flank was in the magnetosheath, and the LANL-094 and GMS-4 geosynchronous satellites also found they were in the magnetosheath. This event provides an excellent opportunity to test and validate the predictability and accuracy of the existing magnetopause location models for the National Space Weather Program. Currently, there are two empirical models that use the solar wind pressure and the north-south component of the interplanetary magnetic field to predict the magnetopause location. The database and method used in deriving the two models are different. While Shue et al.'s [1997] model may be applicable to a larger solar wind parameter range, Roelof and Sibeck's [1993] model is restricted to average solar wind conditions. With small differences, both Shue et al.'s model and extrapolated Roelof and Sibeck's model predict that the magnetopause crosses geosynchronous orbit in the subsolar region. Therefore, both of them predict correctly the magnetopause crossings of LANL-094 and GMS-4. The two models predict completely differently in the flank. Shue et al.'s model is consistent with Geotail's measurement. The extrapolated Roelof and Sibeck's model predicts that the Geotail satellite should remain in the magnetosphere. At 1115 UT, the solar wind condition returned to normal values. The magnetopause moved outward to 8 Re at the subsolar point. The Telstar-401 was far inside the magnetosphere when the malfunction occurred.

Reference:

Roelof, E. C., and D. G. Sibeck, Magnetopause shape as a bivariate function of interplanetary magnetic field Bz and solar wind dynamic pressure, J. Geophys. Res., 98, 21,421, 1993.

Shue, J.-H, J. K. Chao, H. C. Fu, C. T. Russell, P. Song, K. K. Khurana, and H. J. Singer, A new functional form to study the solar wind control of the magnetopause size and shape, J. Geophys. Res., in press, 1997.

(More predictions can be found in http://www-istp.gsfc.nasa.gov/istp/cloud_jan97/theory.html#shue)