From: baalke@zagami.jpl.nasa.gov   
      
   News Office   
   Massachusetts Institute of Technology   
   Cambridge, Massachusetts   
      
   NOVEMBER 14, 2003   
      
   Solar outbursts provide "perfect storms" for Haystack space weather watchers   
   By Carolyn Collins Petersen   
      
   On the morning of October 28, 2003 a gigantic solar flare sent a powerful burst   
   of energy and matter racing out into space. It was the third most powerful ever   
   measured and astronomers classified it as an X17.2 flare (on a scale of x-ray   
   intensity ranging from 1 to 20). The coronal mass ejection associated with it   
   unleashed a flood of charged particles directly toward Earth and triggered   
   auroral displays seen as far south as Texas. During the next few days, two more   
   giant eruptions of the Sun also sent their energy hurtling towards Earth.   
      
   During the next few days, two more giant eruptions also sent their energy   
   hurtling towards Earth.   
      
   For the atmospheric scientists at MIT's Haystack Observatory who track dynamic   
   interactions between the sun and Earth, these outbursts were the perfect   
   storms:   
   strong, fast-moving solar winds and streams of plasma interacting with Earth's   
   magnetic field, creating magnetic disturbances and circulating electrical   
   currents in the upper atmosphere. While satellite operators, pipeline companies   
   and grid owners rushed to shut down and safeguard their equipment, Haystack   
   space weather watchers swung into action, measuring the activity with the   
   Westford, Mass.-based Millstone Hill Radar, a Global Positioning Satellite   
   receiver tied into a worldwide network of more than 900 GPS sites and a series   
   of optical instruments.   
      
   The observatory's radars, supported by the National Science Foundation, charted   
   changes in the ionosphere (a region of the Earth's atmosphere extending from   
   about 100 to 1,000 kilometers above the Earth's surface), measured the   
   thickness   
   of the ionosphere and tracked auroral displays as they danced overhead.   
      
   Now, more than two weeks after the events, the data gathered at Haystack and   
   its   
   associated facilities are just starting to be analyzed. Preliminary indications   
   show incredible changes in Earth's upper atmosphere during late October,   
   resulting from disturbances characterized by John Foster, the observatory's   
   associate director and leader of the Atmospheric Sciences Group at Haystack, as   
   the most violent in years. "These powerful storms were the biggest in this   
   solar   
   cycle and in this decade," he said. "The effects we've observed, such as the   
   redistribution of the ionosphere, are the most pronounced of any we've seen to   
   this date."   
      
   While the upper atmosphere is constantly changing during storms, Foster noted   
   that the ionospheric redistribution during the latest events gave Haystack   
   observers plenty of data to analyze over the coming months. "We are doing   
   leading-edge research here at Haystack in this area," he said. "In particular,   
   the mid-latitude geomagnetic storm response is something that we've been doing   
   fundamental work on for the past couple of years."   
      
   Foster's team will use their data to quantify the size and effects of   
   perturbations of the upper atmosphere, and integrate that into what's already   
   known about space weather. And, since the sunspot group that birthed these   
   outbursts will soon rotate Earthward, the science teams are getting ready for   
   another round of severe space weather around Thanksgiving. "This group is large   
   and active," Foster said. "It will come back and point at the Earth again, and   
   when it does, we'll be ready for it. We're planning to have our full monitoring   
   system in place to catch all the changes in Earth's ionosphere as they occur."   
      
   The sun and Earth: electrical ties that bind   
      
   These geomagnetic storms are powerful evidence of the electrical ties coupling   
   Earth and the sun, particularly when they stir up activity in the near-Earth   
   environment. Space weather-induced disturbances, plus the effects from more   
   humdrum solar activity, have been a research focus of the Haystack group for   
   more than 30 years. Yet it is only recently that the full story of sun-Earth   
   interactions has started to unfold, and space weather plays a huge role.   
      
   The sun-Earth connection is an intricate one. Earth floats along cocooned   
   inside   
   a thick atmosphere, protected by a magnetic field (its magnetosphere), warmed   
   by   
   sunlight but also buffeted by the solar wind and stronger outbursts from the   
   sun. The sun, in turn, has its own complex magnetic field structure. The most   
   obvious manifestations of that structure show up as sunspots (where intense   
   magnetic lines of force break through the surface), prominences (which are   
   supported and pervaded by magnetic fields), and streamers and loops that are   
   shaped by magnetic lines of force.   
      
   Outbursts from the sun are pervaded by magnetic fields, and when these hit   
   Earth's magnetosphere, we get space weather. Solar ultraviolet radiation and   
   X-rays interact with the top of our atmosphere to create the ionosphere, and   
   radiation strips electrons of atoms of atmospheric gas, creating a region of   
   positively charged ions and free negative electrons, usually pervaded by an   
   electrical current. This ionospheric soup bends or reflects radio and radar   
   signals and allows them to bounce around the planet. Changes in the   
   composition,   
   temperature and location of the ionosphere show up as perturbations in the   
   propagation of radio signals, and those perturbations can be used as   
   diagnostics   
   of the ionosphere and the space weather that affects it.   
      
   Space weather originates with solar activity that arrives at Earth in stages,   
   and during storms like those unleashed in late October, the magnetosphere   
   really   
   takes a beating. A snowstorm of energetic particles from an outburst starts to   
   arrive about 20 minutes after the outburst and poses hazards to spacecraft   
   electronics and any astronauts on orbit. Plasmas (with entrained magnetic   
   fields) arrive a day or so after the flare. They set off geomagnetic storms,   
   cause currents to flow in the magnetosphere, heat the ionosphere and energize   
   particles, which in turn increases drag on orbiting satellites. The electrons   
   in   
   the ionosphere collide with molecules, causing auroral displays and raising the   
   risk of electrostatic discharges that can damage spacecraft hardware.   
      
   During heavy bouts of space weather, material in the upper ionosphere is   
   redistributed from Earth's lower latitudes to the mid-latitudes and ultimately   
   up to the rarefied atmosphere over the polar regions. This happens very   
   quickly,   
   said Foster, who described charged plasmas in the ionosphere moving at speeds   
   of   
      
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