磁層頂結(jié)構(gòu)的MHD模擬研究.pdf

1、摘要由于缺少衛(wèi)星觀測(cè)數(shù)據(jù)，基于觀測(cè)的磁層頂位形模型還不夠理想。隨著計(jì)算機(jī)技術(shù)和數(shù)值模擬方法的發(fā)展，基于對(duì)磁層頂位形的物理理論研究構(gòu)建的數(shù)值模擬數(shù)據(jù)是解決這一問題的有效途徑。本文采用太陽(yáng)風(fēng)一磁層一電離層系統(tǒng)全球磁流體力學(xué)(MHD)的數(shù)值模擬數(shù)據(jù)，研究磁層頂?shù)慕Y(jié)構(gòu)及單一條件下的位形，主要研究了幾種不同太陽(yáng)風(fēng)動(dòng)壓&和行星際磁場(chǎng)IMF的z分量&條件下，地球赤道面和子午面的磁層頂位置和形狀特征。對(duì)赤道面磁層頂?shù)哪M結(jié)果顯示：磁層頂日下點(diǎn)高度r。主

2、要由Dp控制。隨著Dp增加，磁層頂被壓縮，r。顯著減小。相同^條件下，在IMF2分量由南向(B:0)逐漸增大的過程中，r。緩慢增大。不同條件下MHD模擬所得磁層頂張角0變化較小，反映了赤道面磁層頂結(jié)構(gòu)的自相似性。與Shueetal.[1998](Shue98)低緯磁層頂經(jīng)驗(yàn)?zāi)Ｐ捅容^發(fā)現(xiàn)，MHD模擬能較好再現(xiàn)磁層頂日下點(diǎn)位置rQ對(duì)！^和《的依賴關(guān)系。MHD模擬和經(jīng)驗(yàn)?zāi)Ｐ徒o出的磁層頂張角^差別較小但MHD模擬中令隨&的變化趨勢(shì)并非經(jīng)驗(yàn)?zāi)Ｐ椭?/p>

3、的簡(jiǎn)單線性關(guān)系。對(duì)子午面的研究發(fā)現(xiàn)：采用以電流密度極大值為判據(jù)MHD模擬數(shù)據(jù)描繪的磁層頂位形和高緯經(jīng)驗(yàn)?zāi)Ｐ虰oardsenetal.[2000](B00)—致，具有內(nèi)凹結(jié)構(gòu)特征。論證了由于子午面存在極尖區(qū)，不能簡(jiǎn)單利用Shueetal.[1997](Shue97)低緯磁層頂位形函數(shù)擬合計(jì)算r。。行星際磁場(chǎng)為南向時(shí)，隨磁場(chǎng)強(qiáng)度增強(qiáng)，日下點(diǎn)距離減??；行星際磁場(chǎng)為北向時(shí)，隨磁場(chǎng)增強(qiáng)，日下點(diǎn)距離rQ增大。動(dòng)壓增大，日下點(diǎn)距離&減小。南向磁場(chǎng)增強(qiáng)

4、，背陽(yáng)面的磁層頂張角變大。在子午面cusp磁尾側(cè)的模擬數(shù)據(jù)與Shue97模型符合較好，行星際磁場(chǎng)南向分量越大，磁層頂?shù)膹埥莂越大，磁層頂擴(kuò)張更加顯著。在磁場(chǎng)為南向增大時(shí)，隨)增大aAbstractBecauseofthelackofsufficientsatellitedatatherearefewhighlatitudemagopauseshapemodels.Withthedevelopmentofcomputertechnolog

5、ynumericalsimulationmethodsthesimulationdatabasedonphysicaltheyofmagopauseisbecomingeffectivesubstitutes.Inthispapertheglobalmagohydrodynamics(MHD)numericalsimulationdataofthecoupledmodelofsolarwindmagosphereionospheresy

6、stemareusedtostudythethreedimensionalstructureofthemagopauseitsshapeatdistinctconditions.Westudythepositionshapeofthemagopauseunderseveralsolarwinddynamicpressure(Dp)interplaarymagicfield(IMF)conditions.Thesimulationresu

7、ltsofequatialplaneshowthatthesubsolarposition(r0)ofthemagopauseismainlycontrolledbyDpwithsignificantdecreasingofr0asDpincreases.AtcertainDpwhensouthernIMFB_(B_0)increasesthesubsolarpositionr0keepsgraduallyincreasing.Fall

8、casesstudiedheretheflareangle(p)ofthemagopauseexperiencesverysmallchange.Thisprovidesanevidencefthestructuralselfsimilarityofthemagopauseinequatialplane.ComparedwiththeempiricallowlatitudemagopausemodelofShue98MHDsimulat

9、ioncanreproducethedependenceofthesubsolarpointrQonDpandB:.Astotheflareangle(althoughthedifferencebetweenourMHDsimulationempiricalmodelfeachcaseisverysmallthevariationofwithIMFB_inMHDresultsisnotthelinearrelationshipassho

10、wninempiricalmodel.ItisfoundthatinthenoonmidnightmeridianplanethemagopauseshapehasevidentconcavefeatureswhichisconsistentwiththeexperiencemodelofBoardseal.[2000].Thecuspstructureofthemeridionalplanedoesnotfollowthemodelo

11、fShueetal.[1997]flowlatitudemagopause.Byanalyzingthechangeofthemagopauseshapeparametersonthenoonmidnightmeridianplaneweobtainthesameresultswiththatofempiricalmodel.Thesimulationresultsshowthatinthenoonmidnightmeridianpla