A Moreton wave, Solar Tsunami, or Moreton-Ramsey wave is the chromospheric signature of a large-scale

solar corona In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's Stellar atmosphere, atmosphere. It is a hot but relatively luminosity, dim region of Plasma (physics), plasma populated by intermittent coronal structures such as so ...

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...

. Described as a kind of

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

tsunami A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...

", they are generated by

solar flares A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Stellar atmosphere, Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar partic ...

. They are named for American astronomer Gail Moreton, an observer at the Lockheed Solar Observatory in

Burbank Burbank may refer to: Places Australia * Burbank, Queensland, a suburb in Brisbane United States * Burbank, California, a city in Los Angeles County * Burbank, Santa Clara County, California, a census-designated place * Burbank, Illinois, ...

, and Harry E. Ramsey, an observer who spotted them in 1959 at The Sacramento Peak Observatory. He discovered them in

time-lapse photography Time-lapse photography is a technique in which the frequency at which film frames are captured (the frame rate) is much lower than the frequency used to view the sequence. When played at normal speed, time appears to be moving faster and th ...

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 The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space (now Airbus Defence and Space) that was launched on a Lockheed Martin Atlas IIAS la ...

(SOHO) 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".) The reality of Moreton waves (also known as fast-mode MHD waves) has also been confirmed by the two Solar Terrestrial Relations Observatory (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 A coronal mass ejection (CME) is a significant ejection of plasma mass from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understandin ...

in February 2009. Moreton measured the waves propagating at a

speed In kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. Intro ...

of 500–1500 km/s. Yutaka Uchida interpreted Moreton waves as MHD fast mode shock waves propagating in the corona. He links them to type II radio bursts, which are radio-wave discharges created when coronal mass ejections accelerate shocks. Moreton waves can be observed primarily in the Hα band.

References

* More of Moreton's papers can be foun
here (SAO/NASA System)

External links

- many recordings (MP3 format) of solar radio emissions including a solar flare shockfront. {{The Sun Stellar phenomena Solar phenomena

See also

References

External links