J/ApJ/854/78ivo://CDS.VizieR/J/ApJ/854/78doi:10.26093/cds/vizier.18540078CDSFinley A.J.Matt S.P.2019-01-09T08:26:44Z2018-12-20T15:54:50ZCDS support team

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

cds-question@unistra.frmagnetic-fieldsastronomical-modelsDuring the lifetime of Sun-like or low-mass stars a significant amount of angular momentum is removed through magnetized stellar winds. This process is often assumed to be governed by the dipolar component of the magnetic field. However, observed magnetic fields can host strong quadrupolar and/or octupolar components, which may influence the resulting spin-down torque on the star. In Paper I (Finley & Matt 2017ApJ...845...46F), we used the magnetohydrodynamic (MHD) code PLUTO Mignone+ 2007ApJS..170..228M ; Mignone 2009MSAIS..13...67M) to compute steady-state solutions for stellar winds containing a mixture of dipole and quadrupole geometries. We showed the combined winds to be more complex than a simple sum of winds with these individual components. This work follows the same method as Paper I, including the octupole geometry, which not only increases the field complexity but also, more fundamentally, looks for the first time at combining the same symmetry family of fields, with the field polarity of the dipole and octupole geometries reversing over the equator (unlike the symmetric quadrupole). We show, as in Paper I, that the lowest-order component typically dominates the spin-down torque. Specifically, the dipole component is the most significant in governing the spin-down torque for mixed geometries and under most conditions for real stars. We present a general torque formulation that includes the effects of complex, mixed fields, which predicts the torque for all the simulations to within 20% precision, and the majority to within ~5%. This can be used as an input for rotational evolution calculations in cases where the individual magnetic components are known.2018ApJ...854...78Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/854/78CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/MNRAS/390/567 : Magnetic field and velocity of mid M dwarfs (Morin+, 2008)J/ApJ/695/679 : Stellar rotation in M35 (Meibom+, 2009)J/MNRAS/413/2218 : Stellar rotation in Hyades and Praesepe (Delorme+, 2011)J/ApJ/733/115 : Rotation periods and membership in M34 (Meibom+, 2011)J/ApJ/737/L35 : Pulsed Alfven waves in the solar wind (Gosling+, 2011)J/ApJ/738/119 : Conversion from magnetoacoustic to Alfven wavesJ/MNRAS/432/1203 : Rotation periods of M-dwarf stars (McQuillan+, 2013)J/ApJ/776/67 : Rotational tracks (van Saders+, 2013)J/MNRAS/441/2361 : Stellar magnetism, age and rotation (Vidotto+, 2014)J/AJ/152/115 : Pleiades members with K2 LCs. III. (Stauffer+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/854/78https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/854/78http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/854/78https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/854/78https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/854/78http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/854/78GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/ApJ/854/78/table4Input parameters and results from simulations with three magnetic componentsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCase[1/160] Casemeta.idintRdip[0/1] Ratio, dipole to total field strengthphys.magFieldfloatRquad[0/1] Ratio, quadrupole to total field strengthphys.magFieldfloatRoct[-0.9/1] Ratio, octupole to total field strengthphys.magFieldfloatva/vesc[0.5/20] Ratio, Alfven speed to escape velocityphys.veloc.escape;arith.ratiofloatRa/R*[2.7/28.1] Ratio, Alfven to stellar radiusphys.size.radius;arith.ratiofloatUpsilon[4/549000] Wind magnetisation ({Upsilon})phys.magFieldintUpsilonOpen[194/156000] Open flux wind magnetisationphys.magFieldintv(Ra)Avg/vesc[0.1/3.2] Average wind speed at the Alfven surface to escape velocityphys.veloc.escape;arith.ratiofloatJ/ApJ/854/78/table2Input parameters and results from simulations with one & two magnetic componentsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCase[1/160] Casemeta.idintRdip[0/1] Ratio, dipole to total field strengthphys.magFieldfloatRquad[0/1] Ratio, quadrupole to total field strengthphys.magFieldfloatRoct[-0.9/1] Ratio, octupole to total field strengthphys.magFieldfloatva/vesc[0.5/20] Ratio, Alfven speed to escape velocityphys.veloc.escape;arith.ratiofloatRa/R*[2.7/28.1] Ratio, Alfven to stellar radiusphys.size.radius;arith.ratiofloatUpsilon[4/549000] Wind magnetisation ({Upsilon})phys.magFieldintUpsilonOpen[194/156000] Open flux wind magnetisationphys.magFieldintv(Ra)Avg/vesc[0.1/3.2] Average wind speed at the Alfven surface to escape velocityphys.veloc.escape;arith.ratiofloat