2601:1C2:C102:5F2E:5443:A506:ACBA:EE9B: Seems to be entirely written by the author of multiple sources to push his fringe theory

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Seems to be entirely written by the author of multiple sources to push his fringe theory

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{{Short description|Decrease in cosmic ray intensity}}
A '''Forbush decrease''' is a rapid decrease in the observed [[galactic cosmic ray]] intensity following a [[coronal mass ejection]] (CME). It occurs due to the [[magnetic field]] of the [[plasma (physics)|plasma]] [[solar wind]] sweeping some of the galactic cosmic rays away from [[Earth]]. The term ''Forbush decrease'' was named after the [[United States|American]] physicist [[Scott Forbush|Scott E. Forbush]], who studied [[cosmic rays]] in the 1930s and 1940s.

==Observation==
[[File:ExtremeEvent 20120304-00h 20120317-24h.jpg|thumb|right|320px|Forbush Decrease in March 2012.<ref>{{cite web | title=Extreme Space Weather Events | publisher=[[National Geophysical Data Center]] | url=http://sxi.ngdc.noaa.gov/sxi_greatest.html | access-date=2012-04-19 | archive-date=2012-05-22 | archive-url=https://web.archive.org/web/20120522031032/http://sxi.ngdc.noaa.gov/sxi_greatest.html | url-status=dead }}</ref>]]

The Forbush decrease is usually observable by [[particle detector]]s on Earth within a few days after the CME, and the decrease takes place over the course of a few hours. Over the following several days, the galactic cosmic ray intensity returns to normal. Forbush decreases have also been observed by humans on ''[[Mir]]'' and the [[International Space Station]] (ISS), at other locations in the inner heliosphere such as the [[Solar Orbiter]] spacecraft,<ref name="Freiherr von Forstner Dumbović Möstl Guo p. ">{{cite journal | last1=Freiherr von Forstner | first1=J. L. | last2=Dumbović | first2=M. | last3=Möstl | first3=C. | last4=Guo | first4=J. | last5=Papaioannou | first5=A. |display-authors=4 | title=Radial evolution of the April 2020 stealth coronal mass ejection between 0.8 and 1 AU. Comparison of Forbush decreases at Solar Orbiter and near the Earth | journal=Astronomy & Astrophysics | date=2021-03-03 | volume=A1 | issn=0004-6361 | doi=10.1051/0004-6361/202039848 | page=656| arxiv=2102.12185 | bibcode=2021A&A...656A...1F | s2cid=232035885 }}</ref> and at Mars with the [[Mars Science Laboratory]] rover's [[Radiation assessment detector]]<ref name="Freiherr von Forstner Guo Wimmer‐Schweingruber Hassler 2018 pp. 39–56">{{cite journal | last1=Freiherr von Forstner | first1=Johan L. | last2=Guo | first2=Jingnan | last3=Wimmer-Schweingruber | first3=Robert F. | last4=Hassler | first4=Donald M. | last5=Temmer | first5=Manuela |display-authors=4 | title=Using Forbush Decreases to Derive the Transit Time of ICMEs Propagating from 1 AU to Mars | journal=Journal of Geophysical Research: Space Physics | publisher=American Geophysical Union (AGU) | volume=123 | issue=1 | year=2018 | issn=2169-9380 | doi=10.1002/2017ja024700 | pages=39–56| arxiv=1712.07301 | bibcode=2018JGRA..123...39F | doi-access=free }}</ref> and the [[MAVEN]] orbiter,<ref name="Guo Lillis Wimmer-Schweingruber Zeitlin 2018 p=A79">{{cite journal | last1=Guo | first1=Jingnan | last2=Lillis | first2=Robert | last3=Wimmer-Schweingruber | first3=Robert F. | last4=Zeitlin | first4=Cary | last5=Simonson | first5=Patrick |display-authors=4 | title=Measurements of Forbush decreases at Mars: both by MSL on ground and by MAVEN in orbit | journal=Astronomy & Astrophysics | volume=611 | year=2018 | issn=0004-6361 | doi=10.1051/0004-6361/201732087 | page=A79| arxiv=1712.06885 | bibcode=2018A&A...611A..79G | doi-access=free }}</ref> as well as in the outer solar system by instruments onboard ''[[Pioneer 10]]'' and ''[[Pioneer 11|11]]'' and ''[[Voyager 1]]'' and ''[[Voyager 2|2]]'', even past the orbit of [[Neptune]].

The magnitude of a Forbush decrease depends on three factors:
* the size of the CME
* the strength of the magnetic fields in the CME
* the proximity of the CME to the Earth

A Forbush decrease is sometimes defined as being a decrease of at least 10% of galactic cosmic rays on Earth, but ranges from about 3% to 20%. The amplitude is also highly dependent on the energy of cosmic rays that is observed by the specific instrument, where lower energies typically show larger decreases.<ref name="Lockwood Webber Debrunner 1991 p=5447">{{cite journal | last1=Lockwood | first1=J. A. | last2=Webber | first2=W. R. | last3=Debrunner | first3=H. | title=The rigidity dependence of forbush decreases observed at the Earth | journal=Journal of Geophysical Research | publisher=American Geophysical Union (AGU) | volume=96 | issue=A4 | year=1991 | issn=0148-0227 | doi=10.1029/91ja00089 | page=5447| bibcode=1991JGR....96.5447L }}</ref> Reductions of 30% or more have been recorded aboard the ISS.

The overall rate of Forbush decreases tends to follow the 11-year [[sunspot]] cycle. It is more difficult to shield astronauts from galactic cosmic rays than from solar wind, so future astronauts might benefit most from radiation shielding during [[Solar minimum|solar minima]], when the suppressive effect of CMEs is less frequent.

==See also==
*[[Ionizing radiation]]

==References==
{{Reflist}}

==External links==
*[https://web.archive.org/web/20100403062301/http://science.nasa.gov/headlines/y2005/07oct_afraid.htm Who's Afraid of a Solar Flare?] from Science@NASA
*[http://www.ips.gov.au/Geophysical/1/4 Cosmic Ray Data Applications to Space Weather Forecasting] {{Webarchive|url=https://web.archive.org/web/20051016005339/http://www.ips.gov.au/Geophysical/1/4 |date=2005-10-16 }}

{{DEFAULTSORT:Forbush Decrease}}
[[Category:Cosmic rays]]
[[Category:Solar phenomena]]

Forbush decrease - Revision history

2601:1C2:C102:5F2E:5443:A506:ACBA:EE9B: Seems to be entirely written by the author of multiple sources to push his fringe theory