Linear and Nonlinear Evolution of the Parker Instability of Magnetic-Flux Sheets in Co-Rotating Coordinates

Publications of the Astronomical Society of Japan

Matsumoto, Ryoji³  Shibata, Kazunari¹  Chou, Wenchien²  Tajima, Toshiki² 

[1] National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181;Department of Physics and Institute for Fusion Studies, University of Texas, Austin, TX 78712, USA E-mail(WC):;Department of Physics, Faculty of Science, Chiba University, 1-33 Yayoi-Cho, Inage-ku, Chiba 263

关键词: Magnetohydrodynamics;    "Sun: magnetic fields";    "Star: rotation";   

DOI  :  10.1093/pasj/49.3.389

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

Wepresentastudyofthemagneticbuoyancyinstability(orParkerinstability)ofstellaratmospheres,inparticularthatoftheeffectoftheCoriolisforce,viaalinearstabilityanalysisandnonlinear3-DMHDsimulations.Wefindthatfastrotationstabilizesthismodeforatoroidalfluxsheetlocatedneartotheequator:magneticfluxsheetsinlow-latituderegionsarelocallystable,whilethegrowthrateofthefluxsheetneartothepolarzoneisnotmuchreducedbytheCorioliseffect.Thismayexplaintheobservationalresultthatstellarspotsoffastrotatingstarsappeartowardthepolarregion.AnothereffectoftheCoriolisforceisthatthereisacut-offrotationalangularvelocityabovewhichthelong-wavelengthtransverseperturbationsaremoreunstablethantheshortwavelengthones.Thismayexplainwhylargestellarpatchesareobservedinfastrotatingstars.3-Dsimulationsofmagneticfluxsheetsunderbuoyancyinstabilityhavealsobeencarriedoutinco-rotatingCartesiancoordinates.ThesimulationresultsshowthatthecombinationofthebuoyancyinstabilityandtheCorioliseffectgivesrisetoamechanismtotwistthemagnetic-fluxsheetembeddedinthesolar(orstellar)atmosphereofaslowlyrotatingstar(suchastheSun),emergingtothesurfacewithahelicalstructure.WesuggestthatthiscanbeamodeltoexplaintheS-shapedactiveregionsinthelowlatitudesoftheSunshowninthesoftX-raypicturetakenbytheYohkohsatellite.

【 授权许可】

Unknown