Moreton wave

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Animation of a Moreton wave which occurred on December 6, 2006

A Moreton wave or Moreton-Ramsey wave is the chromospheric signature of a large-scale solar coronal shock wave. Described as a kind of solar "tsunami",[1] they are generated by solar flares. They are named for American astronomer Gail Moreton, an observer at the Lockheed Solar Observatory in Burbank, and Harry E. Ramsey, an observer who spotted them in 1959 at The Sacremento Peak Observatory.[2][3][4] He discovered them in time-lapse photography of the chromosphere in the light of the Balmer alpha transition.

There were few follow-up studies for decades. Then the 1995 launch of the Solar and Heliospheric Observatory led to observation of coronal waves, which cause Moreton waves. Moreton waves were a research topic again. (SOHO's EIT instrument discovered another, different wave type called "EIT waves".) [5] The reality of Moreton waves (a.k.a. fast-mode MHD waves) has also been confirmed by the two STEREO spacecraft. They observed a 100,000-km-high wave of hot plasma and magnetism, moving at 250 km/s, in conjunction with a big coronal mass ejection in February 2009.[6][7]

Solar Tsunami

Moreton measured the waves propagating at a speed of 500–1500 km/s.[6] Yutaka Uchida interpreted Moreton waves as MHD fast mode shock waves propagating in the corona.[8] He links them to type II radio bursts, which are radio-wave discharges created when coronal mass ejections accelerate shocks.[9]

Moreton waves can be observed primarily in the band.[10]

See also[edit]

References[edit]

  1. ^ Phillips, Tony (November 24, 2009). "Monster Waves on the Sun are Real". NASA. Retrieved 16 July 2010. 
  2. ^ Moreton, G. E. (1960). "Hα Observations of Flare-Initiated Disturbances with Velocities ~1000 km/sec". Astronomical Journal. 65: 494. Bibcode:1960AJ.....65U.494M. doi:10.1086/108346. 
  3. ^ Moreton, G. E. & Ramsey, H. E. (1960). "Recent Observations of Dynamical Phenomena Associated with Solar Flares". Publications of the Astronomical Society of the Pacific. 72 (428): 357. Bibcode:1960PASP...72..357M. doi:10.1086/127549. 
  4. ^ Athay, R. Grant; Moreton, Gail E. (1961). "Impulsive Phenomena of the Solar Atmosphere. I. Some Optical Events Associated with Flares Showing Explosive Phase". Astrophysical Journal. 133: 935. Bibcode:1961ApJ...133..935A. doi:10.1086/147098. 
  5. ^ Thompson, B.; Plunkett, S. P.; Gurman, J. B.; Newmark, J.S.; St. Cyr, O.C.; Michels, D.J. (1998). "SOHO/EIT observations of an Earth-directed coronal mass ejection on May 12, 1997". Geophysical Research Letters. 25: 2465–2468. Bibcode:1998GeoRL..25.2465T. doi:10.1029/98GL50429. 
  6. ^ a b Atkins, William (26 November 2009). "STEREO spacecraft finds gigantic tsunami on Sun". iTWire. Retrieved 16 July 2010. 
  7. ^ JPL/NASA (November 19, 2009). "Mystery of the Solar Tsunami -- Solved". PhysOrg.com. Retrieved 16 July 2010. 
  8. ^ Sakurai, Takashi (3 September 2002). "SolarNews Newsletter". Solar Physics Division, American Astronomical Society. Retrieved 15 June 2011. 
  9. ^ Layton, Laura (May 15, 2009). "STEREO Spies First Major Activity of Solar Cycle 24". NASA. Retrieved 15 June 2011. 
  10. ^ Narukage, N.; Eto, Shigeru; Kadota, Miwako; Kitai, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari (2004). "Moreton waves observed at Hida Observatory" (PDF). Proceedings IAU Symposium. 2004 (223): 367–370. doi:10.1017/S1743921304006143. Retrieved 2006-12-11. 

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