Editing Interplanetary medium (section)

==Composition and physical characteristics==
The interplanetary medium includes [[Interplanetary dust cloud|interplanetary dust]], [[cosmic ray]]s, and hot [[Plasma (physics)|plasma]] from the [[solar wind]].<ref name="EA-20190312">{{cite news |author=NASA |title=What scientists found after sifting through dust in the solar system |url=https://www.eurekalert.org/pub_releases/2019-03/nsfc-wsf031219.php |date=12 March 2019 |work=[[EurekAlert!]] |access-date=12 March 2019 }}</ref>{{Failed verification|date=June 2019}} The density of the interplanetary medium is very low, decreasing in inverse proportion to the square of the distance from the Sun. It is variable, and may be affected by [[magnetic field]]s and events such as [[coronal mass ejection]]s.   Typical particle densities in the interplanetary medium are about 5-40&nbsp;particles/cm{{sup|3}}, but exhibit substantial variation.<ref name=":0">{{Cite tech report|number=NASA-TM-X-55995|title=Micro-scale structures in the interplanetary medium|author-first=Leonard&nbsp;F.|author-last=Burlaga|date=September 1967|institution=[[NASA]] [[Goddard Space Flight Center]]|url=https://ntrs.nasa.gov/api/citations/19680000537/downloads/19680000537.pdf|access-date=17 August 2023}}</ref>{{Rp|location=Figure 1}}  In the vicinity of the [[Earth]], it contains about 5&nbsp;particles/cm{{sup|3}},<ref name=":2">{{Cite journal |last1=Eviatar |first1=Aharon |last2=Schulz |first2=Michael |date=1970 |orig-date=7 July 1969 |title=Ion-temperature anisotropies and the structure of the solar wind |journal=Planetary and Space Science |location=Northern Ireland |publisher=Pergamon Press |volume=18 |issue=3 |pages=321–332 |doi=10.1016/0032-0633(70)90171-6|bibcode=1970P&SS...18..321E }}</ref>{{Rp|page=326}} but values as high as 100&nbsp;particles/cm{{sup|3}} have been observed.<ref name=":0" />{{Rp|location=Figure 2}}

The temperature of the interplanetary medium varies through the solar system.  [[Joseph Fourier]] estimated that interplanetary medium must have temperatures comparable to those observed at [[Earth's poles]], but [[Right for the wrong reason|on faulty grounds]]: lacking modern estimates of [[Atmospheric circulation|atmospheric heat transport]], he saw no other means to explain the relative consistency of [[Earth's climate]].<ref>{{Cite journal |last=Fourier |first=Jean-Baptiste&nbsp;Joseph |author-link=Joseph Fourier |date=1 September 2004 |orig-date=1827 |title=Mémoire sur les Températures du Globe Terrestre et des Espaces Planétaires |trans-title=On the Temperatures of the Terrestrial Sphere and Interplanetary Space |url=https://geosci.uchicago.edu/~rtp1/papers/Fourier1827Trans.pdf |journal=Mémoires D l'Académie Royale des Sciences de l'Institute de France |volume=VII |pages=570–604 |translator-last=Pierrehumbert |translator-first=R.&nbsp;T.}}</ref>  A very hot interplanetary medium remained a minor position among geophysicists as late as 1959, when Chapman proposed a temperature on the order of 10000&nbsp;K,<ref name=":3">{{Cite journal |last=Chapman |first=S. |date=1959 |title=Interplanetary Space and the Earth's Outermost Atmosphere |url=https://www.jstor.org/stable/100693 |journal=Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences |volume=253 |issue=1275 |pages=462–481 |doi=10.1098/rspa.1959.0208 |jstor=100693 |bibcode=1959RSPSA.253..462C |s2cid=95492893 |issn=0080-4630|url-access=subscription }}</ref> but observation in [[Low Earth orbit]] of the [[exosphere]] soon contradicted his position.{{Citation needed|date=August 2023}}  In fact, both Fourier and Chapman's final predictions were correct: because the interplanetary medium is so [[rarefied]], it does not exhibit [[thermodynamic equilibrium]].  Instead, different components have different temperatures.<ref name=":0" />{{Rp|page=4}}<ref name=":2" /><ref name=":1">{{Cite journal |last1=Sittler |first1=Edward&nbsp;C. |last2=Guhathakurta |first2=Madhulika |date=1 October 1999 |orig-date=20 March 1998 |title=Semi&shy;empirical two-dimensional magneto&shy;hydro&shy;dynamic model of the solar corona and interplanetary medium |journal=The Astrophysical Journal |publisher=[[American Astronomical Society]] |publication-place=USA |volume=523 |pages=812–826 |doi=10.1086/307742|doi-access=free }}  Corrected in [[Digital object identifier|doi]]:[http://dx.doi.org/10.1086/324303 10.1086/324303].</ref>  The solar wind exhibits temperatures consistent with Chapman's estimate in [[cislunar space]],<ref name=":2" />{{Rp|pages=326,329}}<ref name=":1" /><ref>{{Cite tech report|last1=Burlaga|first1=L.&nbsp;F.|last2=Ogilvie|first2=K.&nbsp;W.|title=Solar wind temperature and speed|date=October 1972|publisher=[[US Department of Commerce]] [[National Technical Information Service]]|publication-place=Springfield, VA|url=https://ntrs.nasa.gov/api/citations/19730003092/downloads/19730003092.pdf|access-date=17 August 2023|number=NASA-TM-X-66091}}</ref> and dust particles near Earth's orbit exhibit temperatures {{Cvt|257|-|298|K|F}},<ref name=":4">{{Cite journal |last1=Dumont |first1=R. |last2=Levasseur-Regourd |first2=A.-C. |date=Feb 1998 |orig-date=16 December 1986 |title=Properties of interplanetary dust from infrared and optical observations I: Temperature, global volume intensity, albedo and their heliocentric gradients |url=https://adsabs.harvard.edu/full/1988A%26A...191..154D |journal=Astronomy and Astrophysics |volume=191 |issue=1 |pages=154–160 |bibcode=1988A&A...191..154D |issn=0004-6361 |via=[[NASA]] [[Astrophysics Data System]]}}</ref>{{Rp|page=157}} averaging about {{Cvt|283|K|F}}.<ref>{{Cite web |last=Libal |first=Angela |date=1 June 2023 |title=The Temperatures of Outer Space Around the Earth |url=https://sciencing.com/temperatures-outer-space-around-earth-20254.html |access-date=2023-08-18 |website=Sciencing |publisher=[[Leaf Group]] Media |language=en |publication-place=Santa Monica, CA}}</ref>  In general, the solar wind temperature decreases [[Inverse-square law|proportional to the inverse-square]] of the distance to the Sun;<ref name=":3" /> the temperature of the dust decreases proportional to the inverse [[cube root]] of the distance.<ref name=":4" />{{Rp|page=157}}  For dust particles within the [[asteroid belt]], typical temperatures range from {{Cvt|200|K|F}} at 2.2&nbsp;AU down to {{Cvt|165|K|F}} at 3.2&nbsp;AU.<ref>{{cite journal
  | author=Low, F. J.
  | display-authors=etal
  | title=Infrared cirrus&nbsp;– New components of the extended infrared emission
  | journal=Astrophysical Journal Letters
  | date=1984
  | volume=278
  | pages=L19–L22
  | bibcode=1984ApJ...278L..19L
  | doi=10.1086/184213 }}</ref>

Since the interplanetary medium is a [[Plasma (physics)|plasma]], or gas of [[ion]]s, the interplanetary medium has the characteristics of a plasma, rather than a simple gas. For example, it carries the Sun's magnetic field with it, is highly electrically conductive (resulting in the [[heliospheric current sheet]]), forms plasma [[Double layer (plasma)|double layer]]s where it comes into contact with a planetary magnetosphere or at the [[Heliopause (astronomy)|heliopause]], and exhibits filamentation (such as in [[Aurora (astronomy)|aurorae]]).

The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. If space were a vacuum, then the Sun's {{10^|−4}} tesla magnetic dipole field would reduce with the cube of the distance to about {{10^|−11}} tesla. But satellite observations show that it is about 100 times greater at around {{10^|−9}} tesla. [[Magnetohydrodynamic]] (MHD) theory predicts that the motion of a conducting fluid (e.g., the interplanetary medium) in a magnetic field induces electric currents which in turn generate magnetic fields, and in this respect it behaves like an [[MHD dynamo]].