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Space Weather and Space Exploration. Dr. David H. Hathaway NASA/MSFC National Space Science and Technology Center 2006 July 20. Outline. Space Weather What is it and why should we care? The Solar Wind The Solar Eruptions Flares, Prominence Eruptions, Coronal Mass Ejections
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Space Weather and Space Exploration Dr. David H. Hathaway NASA/MSFC National Space Science and Technology Center 2006 July 20
Outline • Space Weather • What is it and why should we care? • The Solar Wind • The Solar Eruptions • Flares, Prominence Eruptions, Coronal Mass Ejections • The Solar Activity Cycle • Magnetic Fields • The Key to Understanding Solar Activity • Space Weather Related Missions • Conclusions
Effects on Satellites Over 4500 spacecraft anomalies or malfunctions have been attributed to the space radiation environment.
Effects on Humans Energetic particles from solar flares can be hazardous to astronauts beyond the protection of Earth’s magnetosphere. Passengers on trans-Atlantic flights receive the equivalent of several chest X-rays on each flight during solar maximum.
The Solar Wind The solar wind streams off of the Sun at speeds of 400-800 km/s (1-2 Million MPH). The wind expands through the solar system and doesn’t stop until it reaches the interstellar medium at a surface about twice as far out as Pluto.
Sunspots Sunspots are cooler, darker regions on the solar surface where intense magnetic fields emerge from the deep interior
The “11-year” Sunspot Cycle [Schwabe, 1844] Each cycle has its own special characteristics – maximum amplitude, length, shape, etc.
The Maunder Minimum During the Maunder Minimum (1645-1715) solar activity seemed to cease entirely. Predicting the size of future cycles is extremely important for satellite (and Space Station) operations.
Magnetism is the Key The Solar Spectrum The Zeeman Effect
Hale’s Polarity Law [Hale, 1924] The polarity of the preceding spots in the northern hemisphere is opposite to the polarity of the preceding spots in the southern hemisphere. The polarities reverse from one cycle to the next.
Polar Field Reversal at Cycle Maximum [Babcock, 1959] The polarity of the polar magnetic fields reverses at about the time of the solar activity maximum. (Result of Joy’s Law + Hale’s Law + Meridional Flow + Flux Cancellation across the equator?)
Magnetic Field and Solar Flares Flares are likely to occur when the magnetic field along the neutral line between opposite polarity regions is sheared or twisted from the direction given by the potential field. Vector Magnetograms are needed to determine the presence of this magnetic shear.
Correlations with CMEs Red + => CME Blue + => no CME
Current Missions Ulysses (ESA/NASA – 1990) SOHO(ESA/NASA – 1995) TRACE (NASA – 1998) RHESSI (NASA –2002)
Future Missions STEREO (NASA -2006/08) Solar Dynamics Observatory (NASA -2008/04) Solar-B (Japan/US/UK –2006/09)
Conclusions • Space Weather must be understood and reliably predicted for safe and successful space exploration • Additional scientific research is needed to do this http://solarscience.msfc.nasa.gov/