查看“︁阿耳芬面”︁的源代码

[[File:Parker Solar Probe touches the Sun.webm|thumb|美國國家航空暨太空總署2021年4月的動畫顯示，派克太陽探測器穿過太陽的外層大氣，即[[日冕|恆星日冕]]。日冕邊緣的邊界是阿耳芬面。在該面內部（左邊的圓圈），電漿通過來回傳播到該面的波與太陽連接。在它之外（右邊的圓圈），太陽的磁場和引力太弱，無法約束電漿，它變成了[[太陽風]]，在[[太陽系]]中快速奔跑，以至於太陽風中的波無法回到太陽<ref name=animation/>。]]

'''阿耳芬面'''是恆星{{link-en|星冕|Stellar corona}}與[[星風]]之間的邊界，定義為星冕電漿的[[阿爾文波#阿耳芬速度|阿耳芬速度]]和大尺度星風速相等的地方。它以[[漢尼斯·阿爾文|漢尼斯·阿耳芬]]命名，也被稱為「阿耳芬臨介面」、「阿耳芬點」或「阿耳芬半徑」。2018年，[[派克太陽探測器]]成為第一艘穿越[[太陽]]阿耳芬面的太空船。

== 定義 ==
[[File:Simulated stellar wind environment for AU Mic driven by the different ZDI maps of the star.jpg|thumb|模擬的[[顯微鏡座AU]]星風環境。半透明的陰影顯示了星風的阿耳芬面<ref name="Alvarado-Gómez"/>。]]
[[File:Effect of magnetic field strength and geometry on the AS.jpg|thumb|磁場强度和幾何形狀對阿耳芬面的影響。阿耳芬面深受表面幾何形狀變化的影響<ref name="Chebly"/>。]]
[[File:Simulated stellar wind environment for the Proxima Cen system.jpg|thumb| [[毗鄰星]]系統的模擬星風環境。紫色[[等值面]]對應於星風的阿耳芬面<ref>{{cite journal |last1=Alvarado-Gómez |first1=Julián D. |last2=Drake |first2=Jeremy J. |last3=Garraffo |first3=Cecilia |last4=Cohen |first4=Ofer |last5=Poppenhaeger |first5=Katja |last6=Yadav |first6=Rakesh K. |last7=Moschou |first7=Sofia P. |title=An Earth-like Stellar Wind Environment for Proxima Centauri c |journal=The Astrophysical Journal Letters |date=1 October 2020 |volume=902 |issue=1 |pages=L9 |doi=10.3847/2041-8213/abb885 |issn=2041-8205|arxiv=2009.07266 |doi-access=free }}</ref>。]]

恆星沒有固體表面。然而，它們有一個過熱的大氣層，由通過重力和磁力結合的物質形成<ref name="touching">{{citation-attribution|1={{cite web |last1=Hatfield |first1=Miles |title=NASA Enters the Solar Atmosphere for the First Time |url=https://www.nasa.gov/feature/goddard/2021/nasa-enters-the-solar-atmosphere-for-the-first-time-bringing-new-discoveries |website=NASA |date=13 December 2021 |access-date=30 July 2022 |archive-date=15 December 2021 |archive-url=https://archive.today/20211215144804/https://www.nasa.gov/feature/goddard/2021/nasa-enters-the-solar-atmosphere-for-the-first-time-bringing-new-discoveries |url-status=live }}}}</ref>。{{link-en|星冕|stellar corona}}它延伸到恆星（太陽）表面或[[光球層]]之外，被認為是恆星的外邊界。它標誌著向[[星風]]（[[太陽風]]）的過渡，星風穿過[[行星系統]]。這個極限（邊界）是由星風中的擾動不能傳播回恆星表面的距離來定義的。如果向外的星風速度超過1馬赫，即太陽風定義的「音速」，這些擾動就不能向恆星傳播回來。這個距離在恆星周圍形成了一個不規則的「面」，稱為'''阿耳芬面'''<ref name=NASA>{{citation-attribution|1={{cite web |title=SVS: Parker Solar Probe: Crossing the Alfven Surface |url=https://svs.gsfc.nasa.gov/4958 |website=svs.gsfc.nasa.gov |access-date=30 July 2022 |language=en |date=14 December 2021 |archive-date=8 August 2022 |archive-url=https://web.archive.org/web/20220808233611/https://svs.gsfc.nasa.gov/4958 |url-status=live }}}}</ref>。它也可以被描述為重力和磁場太弱而無法約束將物質推離恆星的熱量和壓力的點。這是恆星大氣結束和星風開始的地方<ref name="touching"/>。

Adhikari、Zank、和Zhao（2019）將阿耳芬面定義為<ref>{{cite journal |last1=Adhikari |first1=L. |last2=Zank |first2=G. P. |last3=Zhao |first3=L.-L. |title=Does Turbulence Turn off at the Alfvén Critical Surface? |journal=The Astrophysical Journal |date=30 April 2019 |volume=876 |issue=1 |pages=26 |doi=10.3847/1538-4357/ab141c|bibcode=2019ApJ...876...26A |s2cid=156048833 |doi-access=free }}</ref>：
<blockquote>
大尺度[[太陽風]]速度<math>U</math>和[[阿爾文波#阿耳芬速度|阿耳芬速度]] <math>V_{\text{A}}</math>的位置相等，因此，它將區分出「次阿耳芬冕流」|<math>U</math>|≪|<math>V_{\text{A}}</math>|從超阿耳芬太陽風流 |<math>U</math>|≫|<math>V_{\text{A}}</math>|
</blockquote>

DeForest、Howard、和McComas (2014)定義阿耳芬面為<ref>{{cite journal |last1=DeForest |first1=C. E. |last2=Howard |first2=T. A. |last3=McComas |first3=D. J. |title=Inbound waves in the solar corona: a direct indicator of Alfvén Surface location |journal=The Astrophysical Journal |date=12 May 2014 |volume=787 |issue=2 |pages=124 |doi=10.1088/0004-637X/787/2/124|arxiv=1404.3235 |bibcode=2014ApJ...787..124D |s2cid=118371646 }}
</ref>：
<blockquote>
一個自然邊界，標誌著單個電漿包和磁通量與太陽本身的因果斷開。阿耳爾芬面是加速太陽風的徑向運動通過徑向[[阿爾文波#阿耳芬速度|阿耳芬速度]]的軌跡，因此任何物質的位移都不能將資訊帶回日冕。因此，它是日冕的自然外邊界，也是行星際空間的內邊界。
</blockquote>

阿耳芬面將星風的次阿耳芬面和超阿耳芬面分開，星風會影響系統中行星軌道周圍任何[[磁層]]/[[電離層]]的結構<ref name="Alvarado-Gómez">{{cite journal |last1=Alvarado-Gómez |first1=Julián D. |last2=Cohen |first2=Ofer |last3=Drake |first3=Jeremy J. |last4=Fraschetti |first4=Federico |last5=Poppenhaeger |first5=Katja |last6=Garraffo |first6=Cecilia |last7=Chebly |first7=Judy |last8=Ilin |first8=Ekaterina |last9=Harbach |first9=Laura |last10=Kochukhov |first10=Oleg |title=Simulating the Space Weather in the AU Mic System: Stellar Winds and Extreme Coronal Mass Ejections |journal=The Astrophysical Journal |date=1 April 2022 |volume=928 |issue=2 |pages=147 |doi=10.3847/1538-4357/ac54b8 |issn=0004-637X|doi-access=free |arxiv=2202.07949 }} [[File:CC BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}</ref>。阿耳芬面的特徵可以作為恆星[[適居帶]]的內邊界<ref name="Chebly">{{cite journal |last1=Chebly |first1=Judy J. |last2=Alvarado-Gómez |first2=Julián D. |last3=Poppenhaeger |first3=Katja |title=Destination exoplanet: Habitability conditions influenced by stellar winds properties |journal=Astronomische Nachrichten |date=May 2022 |volume=343 |issue=4 |doi=10.1002/asna.20210093 |url=https://onlinelibrary.wiley.com/doi/full/10.1002/asna.20210093 |access-date=18 May 2023 |language=en |issn=0004-6337 |arxiv=2111.09707 |s2cid=238922661 |archive-date=18 May 2023 |archive-url=https://web.archive.org/web/20230518070205/https://onlinelibrary.wiley.com/doi/full/10.1002/asna.20210093 |url-status=live }} [[File:CC BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}</ref>。阿耳芬面「名義上」可以在10-30個恆星半徑處找到<ref>{{cite journal |last1=Goelzer |first1=Molly L. |last2=Schwadron |first2=Nathan A. |last3=Smith |first3=Charles W. |title=An analysis of Alfvén radius based on sunspot number from 1749 to today |journal=Journal of Geophysical Research: Space Physics |date=January 2014 |volume=119 |issue=1 |pages=115–120 |doi=10.1002/2013JA019420 |language=en|doi-access=free }}</ref>。

== 研究 ==
研究人員不確定太陽阿耳芬臨界面的確切位置。根據日冕的遠程影像，估計它距離太陽表面10到20個太陽半徑<ref name="touching"/>。2021年4月28日，在第八次飛越太陽時，美國國家航空暨太空總署的派克太陽探測器（PSP）在18.8個太陽半徑處遇到了特定的磁性和粒子條件，表明它穿透了阿耳芬面<ref name="touching"/><ref name=animation>{{cite web |title=GMS: Animation: NASA's Parker Solar Probe Enters Solar Atmosphere |url=https://svs.gsfc.nasa.gov/14036 |website=svs.gsfc.nasa.gov |access-date=30 July 2022 |language=en |date=14 December 2021 |archive-date=4 October 2022 |archive-url=https://web.archive.org/web/20221004004943/https://svs.gsfc.nasa.gov/14036 |url-status=live }}</ref>；探測器用其{{link-en|FIELDS}}和{{link-en|SWEAP}}儀器量測了太陽風電漿環境<ref name=NASA/>。美國國家航空暨太空署將這一事件描述為「觸及太陽」<ref name="touching"/>。在飛越過程中，派克太陽探測器多次進出日冕。這證明了阿耳芬臨界面形狀不像光滑的球，而是有尖刺和穀，使其表面起皺的預測<ref name="touching"/>。

2021年4月28日世界時09:33，派克太陽探測器進入[[光球層]]上方{{convert|13|e6km|e6mi|abbr=off}}的太陽磁化大氣層，在阿耳芬臨界面下方穿越五小時，進入電漿，與太陽發生因果接觸，阿耳芬馬赫數為0.79，磁壓主導離子和電子壓力。磁測圖表明，該區域是在[[盔狀流#偽流媒體|偽流光]] （{{lang-en|pseudostreamer}}）上方快速膨脹的日冕磁場線上出現的穩定流。該流的「次阿耳芬」性質可能是由於偽流光底部的磁重聯受到抑制，該區域的異常低密度和磁測圖證明了這一點<ref>{{cite journal |last1=Kasper |first1=J. C. |last2=Klein |first2=K. G. |last3=Lichko |first3=E. |last4=Huang |first4=Jia |last5=Chen |first5=C. H. K. |last6=Badman |first6=S. T. |last7=Bonnell |first7=J. |last8=Whittlesey |first8=P. L. |last9=Livi |first9=R. |last10=Larson |first10=D. |last11=Pulupa |first11=M. |last12=Rahmati |first12=A. |last13=Stansby |first13=D. |last14=Korreck |first14=K. E. |last15=Stevens |first15=M. |last16=Case |first16=A. W.|author-link16=Anthony W. Case |last17=Bale |first17=S. D. |last18=Maksimovic |first18=M. |last19=Moncuquet |first19=M. |last20=Goetz |first20=K. |last21=Halekas |first21=J. S. |last22=Malaspina |first22=D. |last23=Raouafi |first23=Nour E. |last24=Szabo |first24=A. |last25=MacDowall |first25=R. |last26=Velli |first26=Marco |last27=Dudok De Wit |first27=Thierry |last28=Zank |first28=G. P. |title=Parker Solar Probe Enters the Magnetically Dominated Solar Corona |journal=Physical Review Letters |date=14 December 2021 |volume=127 |issue=25 |pages=255101 |doi=10.1103/PhysRevLett.127.255101|pmid=35029449 |doi-access=free }} [[File:CC BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}</ref>。

== 進階讀物 ==
* {{cite journal |last1=Kasper |first1=Justin C. |last2=Klein |first2=Kristopher G. |title=Strong Preferential Ion Heating is Limited to within the Solar Alfvén Surface |journal=The Astrophysical Journal Letters |date=1 June 2019 |volume=877 |issue=2 |pages=L35 |doi=10.3847/2041-8213/ab1de5|arxiv=1906.02763 |bibcode=2019ApJ...877L..35K |s2cid=174801124 |doi-access=free }}
* {{cite journal |last1=Guilet |first1=Jerome |last2=Foglizzo |first2=Thierry |last3=Fromang |first3=Sebastien |title=Dynamics of an Alfven surface in core collapse supernovae |journal=The Astrophysical Journal |date=2010 |volume=729 |issue=1 |page=71 |doi=10.1088/0004-637X/729/1/71 |arxiv=1006.4697|s2cid=118461285 }}
* {{cite journal |last1=Fionnagáin |first1=D ó |last2=Vidotto |first2=A A |last3=Petit |first3=P |last4=Folsom |first4=C P |last5=Jeffers |first5=S V |last6=Marsden |first6=S C |last7=Morin |first7=J |last8=do Nascimento |first8=J-D |title=The Solar Wind in Time II: 3D stellar wind structure and radio emission |journal=Monthly Notices of the Royal Astronomical Society |date=22 November 2018 |doi=10.1093/mnras/sty3132 |url=https://academic.oup.com/mnras/article/483/1/873/5199230 |access-date=18 May 2023|doi-access=free |arxiv=1811.05356 }}
* {{cite journal |last1=Garraffo |first1=Cecilia |last2=Drake |first2=Jeremy J. |last3=Cohen |first3=Ofer |title=The dependence of stellar mass and angular momentum losses on latitude and on active region and dipolar magnetic fields |journal=The Astrophysical Journal |date=27 October 2015 |volume=813 |issue=1 |pages=40 |doi=10.1088/0004-637X/813/1/40|arxiv=1509.08936 |s2cid=118740200 }}
* {{cite journal |last1=Vidotto |first1=A. A. |last2=Jardine |first2=M. |last3=Morin |first3=J. |last4=Donati |first4=J. F. |last5=Opher |first5=M. |last6=Gombosi |first6=T. I. |title=M-dwarf stellar winds: the effects of realistic magnetic geometry on rotational evolution and planets |journal=Monthly Notices of the Royal Astronomical Society |date=21 February 2014 |volume=438 |issue=2 |pages=1162–1175 |doi=10.1093/mnras/stt2265 |doi-access=free |url=https://academic.oup.com/mnras/article/438/2/1162/1006909 |access-date=18 May 2023|arxiv=1311.5063 }}
* {{cite journal |last1=Vidotto |first1=Aline A. |title=The evolution of the solar wind |journal=Living Reviews in Solar Physics |date=26 April 2021 |volume=18 |issue=1 |pages=3 |doi=10.1007/s41116-021-00029-w |pmid=34722865 |language=en |issn=1614-4961|pmc=8550356 }}

== 參考資料 ==
{{reflist}}

== 外部連結 ==
* {{cite web |title=Solving the sun's super-heating mystery with Parker Solar Probe |url=https://news.umich.edu/solving-the-suns-super-heating-mystery-with-parker-solar-probe/ |website=University of Michigan News |access-date=30 July 2022 |date=4 June 2019}}

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{{恆星|state=collapsed}}

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