J/ApJ/738/119ivo://CDS.VizieR/J/ApJ/738/119doi:10.26093/cds/vizier.17380119CDSCally P.S.Hansen S.C.2013-03-03T15:24:36Z2013-02-13T15:42:36ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frthe-sunmagnetic-fieldspolarimetryastronomical-modelsAlfven waves may be generated via mode conversion from fast magnetoacoustic waves near their reflection level in the solar atmosphere, with implications both for coronal oscillations and for active region helioseismology. In active regions this reflection typically occurs high enough that the Alfven speed a greatly exceeds the sound speed c, well above the a=c level where the fast and slow modes interact. In order to focus on the fundamental characteristics of fast/Alfven conversion, stripped of unnecessary detail, it is therefore useful to freeze out the slow mode by adopting the gravitationally stratified cold magnetohydrodynamic model c->0. This provides a benchmark for fast-to-Alfven mode conversion in more complex atmospheres. Assuming a uniform inclined magnetic field and an exponential Alfven speed profile with density scale height h, the Alfven conversion coefficient depends on three variables only: the dimensionless transverse-to-the-stratification wavenumber {kappa}=kh, the magnetic field inclination from the stratification direction {theta}, and the polarization angle {phi} of the wavevector relative to the plane containing the stratification and magnetic field directions. We present an extensive exploration of mode conversion in this parameter space and conclude that near-total conversion to outward-propagating Alfven waves typically occurs for small {theta} and large {phi} (80-90{deg}), though it is absent entirely when {theta} is exactly zero (vertical field). For wavenumbers of helioseismic interest, the conversion region is broad enough to encompass the whole chromosphere.2011ApJ...738..119Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/738/119CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/737/L35 : Pulsed Alfven waves in the solar wind (Gosling+, 2011)J/MNRAS/410/735 : MAG waves in magnetic and rotating stars (Campos, 2011)J/ApJS/169/439 : Models of solar magnetic structures (Socas-Navarro, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/738/119https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/738/119http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/738/119https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/738/119https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/738/119http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/738/119GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/ApJ/738/119/table1Forward Alfven conversion coefficient A^+^ for a range of {kappa}, {phi}, and magnetic field inclinations {theta}recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordinttheta[10/80] Magnetic field inclination from the stratification direction {theta}degpos.posAngintkappa[0/5] Transverse-to-the-stratification wavenumber {kappa}em.wavenumberfloatA+5Alfven conversion coefficient at {phi}=5{deg} polarization anglestat.fit.paramfloatA+15Alfven conversion coefficient at {phi}=15{deg} polarization anglestat.fit.paramfloatA+25Alfven conversion coefficient at {phi}=25{deg} polarization anglestat.fit.paramfloatA+35Alfven conversion coefficient at {phi}=35{deg} polarization anglestat.fit.paramfloatA+45Alfven conversion coefficient at {phi}=45{deg} polarization anglestat.fit.paramfloatA+55Alfven conversion coefficient at {phi}=55{deg} polarization anglestat.fit.paramfloatA+65Alfven conversion coefficient at {phi}=65{deg} polarization anglestat.fit.paramfloatA+75Alfven conversion coefficient at {phi}=75{deg} polarization anglestat.fit.paramfloatA+85Alfven conversion coefficient at {phi}=85{deg} polarization anglestat.fit.paramfloatA+95Alfven conversion coefficient at {phi}=95{deg} polarization anglestat.fit.paramfloatA+105Alfven conversion coefficient at {phi}=105{deg} polarization anglestat.fit.paramfloatA+115Alfven conversion coefficient at {phi}=115{deg} polarization anglestat.fit.paramfloatA+125Alfven conversion coefficient at {phi}=125{deg} polarization anglestat.fit.paramfloatA+135Alfven conversion coefficient at {phi}=135{deg} polarization anglestat.fit.paramfloatA+145Alfven conversion coefficient at {phi}=145{deg} polarization anglestat.fit.paramfloat