HOUSTON, Sept. 25, 1998 -- Rice University scientists report that a major geomagnetic storm began late on Sept. 24 and was continuing as of last Thursday. Intense auroral displays (the northern and southern lights) associated with the storm were reported at least as far south as Milwaukee.
The storm was tracked by a Rice University space weather model running at the National Oceanographic and Atmospheric Administration's Space Environment Center, the nation's center of space weather services, in Boulder, Colo. The Rice model indicates that the boundary of the earth's magnetosphere--a teardrop-shaped region dominated by the earth's magnetic field--was pushed inside the geostationary orbit altitude, probably exposing communication and navigation satellites to shocked solar wind plasma. The model also indicates storm-generated electrons penetrated the earth's magnetosphere to an unusual depth.
John Freeman, Rice professor of space physics and astronomy, who led the development of the space weather modeling system, and graduate student Andrew Urquhart, an instrumental developer, are analyzing its data.
The geomagnetic storm measured 8.6 on a scale of 0 to 9 used to measure geomagnetic storm intensity. The speed of the solar wind that carries the energy for the storm from the sun reached nearly 1,000 km/s, about twice the normal speed, and the interplanetary magnetic field carried with the solar wind was unusually disturbed.
A storm of this intensity is seen only a few times per decade. This storm may be the harbinger of the next solar maximum due in the year 2000, Freeman says.
This storm apparently originated from an intense solar flare that occurred before midday on Sept. 23. In addition to the slower-moving solar wind plasma that takes a day to arrive at the earth and create the geomagnetic storm, the flare also produced large numbers of very energetic protons that travel at close to the speed of light and arrive at the earth in a few minutes. An additional burst of energetic protons arrived with the storm. Such protons have been known to reduce the output of satellite solar power arrays and could pose a hazard to unprotected astronauts. The storm was expected to subside within the next 24 hours.
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