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Solar wind
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===Fast and slow solar wind=== The solar wind is observed to exist in two fundamental states, termed the slow solar wind and the fast solar wind, though their differences extend well beyond their speeds. In near-Earth space, the slow solar wind is observed to have a velocity of {{val|300|-|500|u=km/s}}, a temperature of ~{{val|100|ul=kilokelvin}} and a composition that is a close match to the [[solar corona|corona]]. By contrast, the fast solar wind has a typical velocity of {{val|750|u=km/s}}, a temperature of {{val|800|u=kilokelvin}}{{Citation needed|reason=The referenced article by Geiss et al 1995 does not provide these numbers|date=July 2024}} and it nearly matches the composition of the Sun's [[photosphere]].<ref>{{Cite journal|last1=Geiss|first1=J.|last2=Gloeckler|first2=G.|last3=Steiger|first3=R. Von|title=Origin of the solar wind from composition data|journal=Space Science Reviews|language=en|volume=72|issue=1–2|pages=49–60|doi=10.1007/BF00768753|issn=0038-6308|bibcode = 1995SSRv...72...49G |year=1995|s2cid=120788623}}</ref> The slow solar wind is twice as dense and more variable in nature than the fast solar wind.<ref name=kallenrode>{{cite book | first=May-Britt | last=Kallenrode | date=2004 | title=Space Physics: An Introduction to Plasmas and | url=https://archive.org/details/springer_10.1007-978-3-662-09959-9 | publisher=Springer | isbn=978-3-540-20617-0 }}</ref><ref>{{cite web | last=Suess | first=Steve | date=June 3, 1999 | url=http://solarscience.msfc.nasa.gov/suess/SolarProbe/Page1.htm | title=Overview and Current Knowledge of the Solar Wind and the Corona | work=The Solar Probe | publisher=NASA/Marshall Space Flight Center | access-date=2008-05-07 | url-status=dead |archive-url = https://web.archive.org/web/20080610125820/http://solarscience.msfc.nasa.gov/suess/SolarProbe/Page1.htm <!-- Bot retrieved archive --> |archive-date = 2008-06-10}}</ref> The slow solar wind appears to originate from a region around the Sun's equatorial belt that is known as the "streamer belt", where coronal streamers are produced by magnetic flux open to the heliosphere draping over closed magnetic loops.{{clarify|date=September 2024}} The exact coronal structures involved in slow solar wind formation and the method by which the material is released is still under debate.<ref>{{cite web | last=Harra | first=Louise |author2=Milligan, Ryan |author3=Fleck, Bernhard | date=April 2, 2008 | url=http://www.esa.int/esaSC/SEMJQK5QGEF_index_0.html | title=Hinode: source of the slow solar wind and superhot flares | publisher=ESA | access-date=2008-05-07 }}</ref><ref>{{Cite journal|last1=Antiochos|first1=S. K.|last2=Mikić|first2=Z.|last3=Titov|first3=V. S.|last4=Lionello|first4=R.|last5=Linker|first5=J. A.|date=2011-01-01|title=A Model for the Sources of the Slow Solar Wind|journal=The Astrophysical Journal|language=en|volume=731|issue=2|pages=112|doi=10.1088/0004-637X/731/2/112|issn=0004-637X|arxiv = 1102.3704 |bibcode = 2011ApJ...731..112A |s2cid=119241929}}</ref><ref>{{Cite journal|last=Fisk|first=L. A.|date=2003-04-01|title=Acceleration of the solar wind as a result of the reconnection of open magnetic flux with coronal loops|journal=Journal of Geophysical Research: Space Physics|language=en|volume=108|issue=A4|pages=1157|doi=10.1029/2002JA009284|issn=2156-2202|bibcode = 2003JGRA..108.1157F |url=https://deepblue.lib.umich.edu/bitstream/2027.42/87652/2/287_1.pdf|url-status=live|archive-url=https://web.archive.org/web/20170816114938/https://deepblue.lib.umich.edu/bitstream/handle/2027.42/87652/287_1.pdf?sequence=2|archive-date=2017-08-16|hdl=2027.42/87652|hdl-access=free}}</ref> Observations of the Sun between 1996 and 2001 showed that emission of the slow solar wind occurred at latitudes up to 30–35° during the [[solar minimum]] (the period of lowest solar activity), then expanded toward the poles as the solar cycle approached maximum. At [[solar maximum]], the poles were also emitting a slow solar wind.<ref name="McComas 1517"/> The fast solar wind originates from [[coronal hole]]s,<ref>Zirker, J. B. (1977), Coronal holes and high‐speed wind streams, ''Reviews of Geophysics'', ''15''(3), 257–269</ref> which are funnel-like regions of open field lines in the Sun's [[magnetic field]].<ref>{{cite journal | last=Hassler | first=Donald M. |author2=Dammasch, Ingolf E. |author3=Lemaire, Philippe |author4=Brekke, Pål |author5=Curdt, Werner |author6=Mason, Helen E. |author7=Vial, Jean-Claude |author8= Wilhelm, Klaus | title=Solar Wind Outflow and the Chromospheric Magnetic Network | journal=Science | date=1999 | volume=283 | issue=5403 | pages=810–813 | doi=10.1126/science.283.5403.810 | pmid=9933156 |bibcode = 1999Sci...283..810H }}</ref> Such open lines are particularly prevalent around the Sun's magnetic poles. The plasma source is small magnetic fields created by [[convection cell]]s in the solar atmosphere. These fields confine the plasma and transport it into the narrow necks of the coronal funnels, which are located only 20,000 km above the photosphere. The plasma is released into the funnel when these magnetic field lines reconnect.<ref>{{cite journal | last=Marsch | first=Eckart |author2=Tu, Chuanyi | date=April 22, 2005 | url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=36998 | title=Solar Wind Origin in Coronal Funnels | journal=Science | volume=308 | issue=5721 | pages=519–23 | publisher=ESA | doi=10.1126/science.1109447 | pmid=15845846 | bibcode=2005Sci...308..519T | s2cid=24085484 | access-date=2008-05-06 }}</ref>
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