Mar 8 2005
From The Space Library
NASA-funded researchers reported that they had discovered that lightning in clouds a few miles above the ground clears a safe zone in the Van Allen Belt~ the radiation belt located thousands of miles above Earth. Without this zone, satellites would have no safe area in which to orbit. The discovery, which NASA described as unexpected, resolved a 40-year debate about how the safe zone forms and how the region clears after magnetic storms fill it with radiation. Previously, the prominent theory held that turbulence in the zone generates radio waves in space, which clear the radiation. However, lightning also generates radio waves. The research team had confirmed the lightning theory using a global map of lightning activity created from data that the Micro Lab 1 spacecraft had collected. The team had also collected radio-wave data from the Radio Plasma Imager aboard the Imager for Magnetopause to Aurora Global Exploration (IMAGE) spacecraft, combining that data with archival data from the Dynamics Explorer spacecraft. These two data sets showed that radio-wave activity in the safe zone closely follows terrestrial lightning patterns; if the radio waves had originated in space rather than Earth, no such correlation would exist. Therefore, the team had concluded that lightning clears radiation within a few days following magnetic storms. According to NASA, engineers could eventually design spacecraft that generate radio waves at the correct frequency and location to clear radiation belts around other planets, enabling humans to explore planets and moons such as Jupiter's Europa. (NASA, “NASA Finds Lightning Clears Safe Zone in Earth's Radiation Belt,” news release 05-070, 8 March 2005, http://www.nasa.gov/home/hqnews/2005/mar/HQ_05070_radiation_belt.html (accessed 29 June 2009); Agence-France Presse, “Lightning Cuts Safe Zone Between Earth Radiation Belts: NASA,” 9 March 2005.)
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