From: baalke@zagami.jpl.nasa.gov   
      
   Nancy Neal/Don Savage   
   Headquarters, Washington                 December 3, 2003   
   (Phone: 202/358-1547)   
      
   Bill Steigerwald   
   Goddard Space Flight Center, Greenbelt, Md.   
   (Phone: 301/286-5017)   
      
   RELEASE: 03-386   
      
   STORMY SPACE WEATHER SLIPS THROUGH CRACKS   
      
        Immense cracks in Earth's magnetic field remain open for   
   hours, allowing the solar wind to gush through and power   
   stormy space weather, according to new observations from   
   NASA's IMAGE spacecraft and the joint NASA/European Space   
   Agency (ESA) Cluster satellites.   
      
   The cracks were previously detected, but researchers now know   
   they can remain open for long periods, rather than opening and   
   closing for just very brief intervals. This new discovery   
   about how the Earth's magnetic shield is breached is expected   
   to help space physicists give better estimates of the effects   
   of severe space weather.   
      
   "We discovered that our magnetic shield is drafty, like a   
   house with a window stuck open during a storm," said Dr.   
   Harald Frey of the University of California (UC), Berkeley,   
   lead author of a paper on this research published Dec. 4 in   
   Nature. "The house deflects most of the storm, but the couch   
   is ruined. Similarly, our magnetic shield takes the brunt of   
   space storms, but some energy continually slips through its   
   cracks, sometimes enough to cause problems with satellites,   
   radio communication and power systems," he said.   
      
   "The new knowledge that the cracks are open for long periods,   
   instead of opening and closing sporadically, can be   
   incorporated into our space weather-forecasting computer   
   models to more accurately predict how our space weather is   
   influenced by violent events on the sun," said Dr. Tai Phan,   
   also of UC Berkeley, co-author of the Nature paper.   
      
   The solar wind is a stream of electrically charged particles   
   (electrons and ions) blown constantly from the sun. The solar   
   wind transfers energy from the sun to the Earth through the   
   magnetic fields it carries and its high speed (hundreds of   
   miles/kilometers per second). It can get gusty during violent   
   solar events, like Coronal Mass Ejections (CMEs), which can   
   shoot a billion tons of electrified gas into space at millions   
   of miles per hour.   
      
   Earth has a magnetic field that extends into space for tens of   
   thousands of miles, surrounding the planet and forming a   
   protective barrier to the particles and snarled magnetic   
   fields the sun blasts toward it during CMEs. However, space   
   storms, which can dump 1,000 billion watts, more than   
   America's total electric-generating capacity, into the Earth's   
   magnetic field, indicated the shield was not impenetrable.   
      
   In 1961, Dr. Jim Dungey of the Imperial College, United   
   Kingdom, predicted cracks might form in the magnetic shield   
   when the solar wind contained a magnetic field oriented in the   
   opposite direction to a portion of the Earth's field. In these   
   regions, the two magnetic fields would interconnect through a   
   process known as "magnetic reconnection," forming a crack in   
   the shield through which the electrically charged particles of   
   the solar wind could flow. In 1979, Dr. Goetz Paschmann, of   
   the Max Planck Institute for Extraterrestrial Physics,   
   Germany, detected the cracks using the International Sun Earth   
   Explorer spacecraft. However, since this spacecraft only   
   briefly passed through the cracks during its orbit, it was   
   unknown if the cracks were temporary features or if they were   
   stable for long periods.   
      
   In the new observations, the Imager for Magnetopause to Aurora   
   Global Exploration (IMAGE) satellite revealed an area almost   
   the size of California in the arctic upper atmosphere   
   (ionosphere) where a 75-megawatt "proton" aurora flared for   
   hours. This aurora, energetic enough to power 75,000 homes,   
   was different from the visible aurora known as the Northern   
   and Southern lights. It was generated by heavy particles   
   (ions) hitting the upper atmosphere and causing it to emit   
   ultraviolet light, which is invisible to the human eye but   
   detectable by the Far Ultraviolet Imager on IMAGE.   
      
   While the aurora was being recorded by IMAGE, the four-   
   satellite Cluster constellation flew far above IMAGE, directly   
   through the crack, and detected solar wind ions streaming   
   through. Normally, these solar wind ions would be deflected by   
   Earth's shield, so Cluster's observation showed a crack was   
   present. This stream of solar wind ions bombarded our   
   atmosphere in precisely the same region where IMAGE saw the   
   proton aurora. The fact that IMAGE was able to view the proton   
   aurora for more than nine hours, until IMAGE progressed in its   
   orbit to where it could not observe the aurora, implies the   
   crack remained continuously open. Estimating from the IMAGE   
   and Cluster data, the crack was twice the size of the Earth at   
   the boundary of our magnetic shield, about 38,000 miles   
   (60,000 km) above the planet's surface. Since the magnetic   
   field converges as it enters the Earth in the polar regions,   
   the crack narrowed to about the size of California down near   
   the upper atmosphere.   
      
   IMAGE was launched March 25, 2000 to provide a global view of   
   the space around Earth influenced by the Earth's magnetic   
   field. The Cluster satellites, built by ESA, and launched July   
   16, 2000, are making a three-dimensional map of the Earth's   
   magnetic field. For images, movies and more information, on   
   the Internet, visit:   
      
   http://www.gsfc.nasa.gov/topstory/2003/1203image_cluster.html   
      
   -end-   
      
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