Moreton wave

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

A Moreton 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 who spotted them in 1959.^[2][3][4][5] 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'.)^[6] The reality of Moreton waves (aka 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/second, in conjunction with a big coronal mass ejection in February 2009.^[7][8]

Solar Tsunami

Moreton waves propagate at a speed of 500–1500 km/s. Yutaka Uchida interpreted Moreton waves as MHD fast mode shock waves propagating in the corona. ^[9] He links them to type II radio bursts, which are radio wave discharges created when coronal mass ejections accelerate shocks. ^[10]

Moreton waves can be observed primarily in the Hα band.^[11]

See also

• Solar transition region
• Spicule (solar physics)
• Solar prominence
• Solar surface fusion
• Gravity wave
• Helioseismology
• Asteroseismology
• OSO 8

References

1. ^ Phillips, Tony (November 24, 2009). "Monster Waves on the Sun are Real". NASA. http://science.nasa.gov/science-news/science-at-nasa/2009/24nov_solartsunami/. 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. ^ Google Answers, Biographical info on Gail E. Moreton. Moreton b. 27 Jun 1930 d. Oct. 1982.
6. ^ Chen, P. F.; Wu, S. T.; Shibata, K.; Fang, C. (2002). "Moreton waves and coronal waves". The Astrophysical Journal 572: L99–L102. Bibcode 2002ApJ...572L..99C. doi:10.1086/341486. http://solar.physics.montana.edu/nuggets/2002/020208/020208.html. 
7. ^ Atkins, William (26 November 2009). "STEREO spacecraft finds gigantic tsunami on Sun". iTWire. http://www.itwire.com/science-news/space/29658-stereo-spacecraft-finds-gigantic-tsunami-on-sun. Retrieved 16 July 2010. 
8. ^ JPL/NASA (November 19, 2009). "Mystery of the Solar Tsunami -- Solved". PhysOrg.com. http://www.physorg.com/news177872248.html. Retrieved 16 July 2010. 
9. ^ Sakurai, Takashi (3 September 2002). "SolarNews Newsletter". Solar Physics Division, American Astronomical Society. http://spd.aas.org/SolarNews/archive/news.2002/19.sep. Retrieved 15 June 2011. 
10. ^ Layton, Laura (May 15, 2009). "STEREO Spies First Major Activity of Solar Cycle 24". NASA. http://www.nasa.gov/mission_pages/stereo/news/solarcycle24.html. Retrieved 15 June 2011. 
11. ^ Narukage, N.; et al., 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. http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=288483. Retrieved 2006-12-11. 

• More of Moreton's papers can be found here (SAO/NASA System).

External links

• "Have you ever heard the Sun?" - many recordings (MP3 format) of solar radio emissions including a solar flare shockfront.

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