Lectures on Solar Physics

TheideafortheselectureseriesaroseataWorkshoponsolarphysicswhichwas heldattheInterUniversityCentreforAstronomyandAstrophysics(IUCAA), Pune/IndiainDecember2000. ThisWorkshopaimedtopresentacompreh- siveandup-to-dateoverviewofsolarphysicsforinterestedstudentsandfaculty inotherbranchesofastrophysics. Itwasintendedtoshowthatthis?eld,c- centratingonourcloseststar,isavitalandexciting?eldofresearch. Forthis purposeanumberofcomprehensivereviewswereorganisedwhichassumedthat theaudiencewouldhaveonlyabasicphysicsbackgroundbuthadnoprior knowledgeaboutsolarphysics. Thesetoflecturescoveredtopicsrangingfrom thesolarcoretotheconvectionzone,thephotosphere,chromosphere,andcorona andextendingtothesolarwindintheinterplanetarymedium DuringandaftertheWorkshoptherewasmuchenthusiasmforthisform ofpresentationanditwasfeltthattheselectures,augmentedbyincludingthe latestresearch?ndingsinthe?eld,wouldbebene?cialtoamuchlargeraudience. Thustheplanforthisbookoriginatedwhichcouldthenberealisedthanksto thepublishers,Springer-Verlag. Thereare9articlesbasedonthelecturesgivenattheWorkshop.Thearticle byChitreon"OverviewofSolarPhysics"givesanintroductiontothewhole varietyofphenomenaofsolarphysics,theproblemsandtheirsolutionsand salientresults. Thearticleon"InstrumentationandObservationaltechniques relatedtoSolarPhysics"byBhatnagardescribesindetailtheprinciplesof- larinstrumentationnormallyusedtotakesimplewhitelight,monochromatic andspectroscopicobservations. Practicalmethodstomeasureimportantbasic parameters,likearea,positionandtheclassi?cationofsunspotsaredescribed indetail. Antia'sarticleon"SolarInteriorandSeismology"describesthesolar interior,thetechniqueofhelioseismologyandhowthisnewtechniqueallowsa determinationoftheinternalstructureanddynamicsoftheSunandconstrains theoriesofstellarstructure,evolutionandangularmomentumtransport. - bastha'sarticleon"TheActiveandExplosiveSun"givesanoverviewofhighly time-dependentphenomenainthephotosphere,chromosphereandcoronaofthe Sunandprovidessometheoreticalmodelsofthesolar?ares. Hasan'sarticle on"MagneticFluxTubesandActivityontheSun"discussesthegeneration, storageandemergenceofmagnetic?eldsintheformofsmall-scale?uxtubes andexaminestheirroleinheatingofthechromosphere.Ventakrishan'sar- cleon"SolarMagneticFields"givesatheoreticaloverviewofthegeneration VI Preface ofmagnetic?eldsbythedynamomechanism,thegeneralmagnetic?eldtop- ogyandhowthemagnetic?eldsaremeasured. Ulmschneider'scontributionon "ThePhysicsofChromospheresandCoronae"discusseswhyallstarslikethe Sunhavehotouterchromosphericandcoronallayers. Itidenti?estheheating mechanismsanddynamicalprocesseswhichtakeplacebothinthepresenceand absenceofmagnetic?elds. ThearticlebyDwivedion"TheSolarCorona"gives ageneraloverviewofthesolarcorona,howitisobservedandwhatthephy- calprocessesleadingtoitsformationare. FinallyManoharan'scontributionon "TheSolarWind"describesthegenerationandmeasurementofthesolarwind derivedfrominsituobservationsbyspacecraftandinterplanetaryscintillation studies. Wehopethatbyreadingtheselectures,interestedpeople,amateurs,graduate andpostgraduatestudentswillbemotivatedtotakeupsolarphysicsasanarea ofresearch,andshareourexcitementaboutthewondersofourneareststar- theSun. WearethankfultoT. PadmanabhanandtheInterUniversityCentrefor AstronomyandAstrophysics,PunefororganisingandhostingthisWorkshop onSolarPhysics. Mumbai,Udaipur,Heidelberg H. M. Antia February2003 A. Bhatnagar P.Ulmschneider ListofContributors AshokAmbastha S. S. Hasan Udaipur Solar Observatory Indian Institute of Astrophysics Physical Research Laboratory Bangalore560034,India P. O. Box No. 198 hasan@iiap. ernet. in Udaipur313001,India ambastha@prl. ernet. in P. K. Manoharan Radio Astronomy Centre H. M. Antia Tata Institute Tata Institute of Fundamental Research of Fundamental Research P. O. Box 8 Homi Bhabha Road Udhagamandalam (Ooty) 643001, Mumbai400005,India India antia@tifr. res. in mano@racooty. ernet. in ArvindBhatnagar Udaipur Solar Observatory P. Ulmschneider Physical Research Laboratory Institut fur TheideafortheselectureseriesaroseataWorkshoponsolarphysicswhichwas heldattheInterUniversityCentreforAstronomyandAstrophysics(IUCAA), Pune/IndiainDecember2000. ThisWorkshopaimedtopresentacompreh- siveandup-to-dateoverviewofsolarphysicsforinterestedstudentsandfaculty inotherbranchesofastrophysics. Itwasintendedtoshowthatthis?eld,c- centratingonourcloseststar,isavitalandexciting?eldofresearch. Forthis purposeanumberofcomprehensivereviewswereorganisedwhichassumedthat theaudiencewouldhaveonlyabasicphysicsbackgroundbuthadnoprior knowledgeaboutsolarphysics.Thesetoflecturescoveredtopicsrangingfrom thesolarcoretotheconvectionzone,thephotosphere,chromosphere,andcorona andextendingtothesolarwindintheinterplanetarymedium DuringandaftertheWorkshoptherewasmuchenthusiasmforthisform ofpresentationanditwasfeltthattheselectures,augmentedbyincludingthe latestresearch?ndingsinthe?eld,wouldbebene?cialtoamuchlargeraudience. Thustheplanforthisbookoriginatedwhichcouldthenberealisedthanksto thepublishers,Springer-Verlag. Thereare9articlesbasedonthelecturesgivenattheWorkshop. Thearticle byChitreon"OverviewofSolarPhysics"givesanintroductiontothewhole varietyofphenomenaofsolarphysics,theproblemsandtheirsolutionsand salientresults. Thearticleon"InstrumentationandObservationaltechniques relatedtoSolarPhysics"byBhatnagardescribesindetailtheprinciplesof- larinstrumentationnormallyusedtotakesimplewhitelight,monochromatic andspectroscopicobservations. Practicalmethodstomeasureimportantbasic parameters,likearea,positionandtheclassi?cationofsunspotsaredescribed indetail.Antia'sarticleon"SolarInteriorandSeismology"describesthesolar interior,thetechniqueofhelioseismologyandhowthisnewtechniqueallowsa determinationoftheinternalstructureanddynamicsoftheSunandconstrains theoriesofstellarstructure,evolutionandangularmomentumtransport. - bastha'sarticleon"TheActiveandExplosiveSun"givesanoverviewofhighly time-dependentphenomenainthephotosphere,chromosphereandcoronaofthe Sunandprovidessometheoreticalmodelsofthesolar?ares. Hasan'sarticle on"MagneticFluxTubesandActivityontheSun"discussesthegeneration, storageandemergenceofmagnetic?eldsintheformofsmall-scale?uxtubes andexaminestheirroleinheatingofthechromosphere. Ventakrishan'sar- cleon"SolarMagneticFields"givesatheoreticaloverviewofthegeneration VI Preface ofmagnetic?eldsbythedynamomechanism,thegeneralmagnetic?eldtop- ogyandhowthemagnetic?eldsaremeasured. Ulmschneider'scontributionon "ThePhysicsofChromospheresandCoronae"discusseswhyallstarslikethe Sunhavehotouterchromosphericandcoronallayers. Itidenti?estheheating mechanismsanddynamicalprocesseswhichtakeplacebothinthepresenceand absenceofmagnetic?elds.ThearticlebyDwivedion"TheSolarCorona"gives ageneraloverviewofthesolarcorona,howitisobservedandwhatthephy- calprocessesleadingtoitsformationare. FinallyManoharan'scontributionon "TheSolarWind"describesthegenerationandmeasurementofthesolarwind derivedfrominsituobservationsbyspacecraftandinterplanetaryscintillation studies. Wehopethatbyreadingtheselectures,interestedpeople,amateurs,graduate andpostgraduatestudentswillbemotivatedtotakeupsolarphysicsasanarea ofresearch,andshareourexcitementaboutthewondersofourneareststar- theSun. WearethankfultoT. PadmanabhanandtheInterUniversityCentrefor AstronomyandAstrophysics,PunefororganisingandhostingthisWorkshop onSolarPhysics. Mumbai,Udaipur,Heidelberg H. M. Antia February2003 A. Bhatnagar P. Ulmschneider ListofContributors AshokAmbastha S. S. Hasan Udaipur Solar Observatory Indian Institute of Astrophysics Physical Research Laboratory Bangalore560034,India P. O. Box No. 198 hasan@iiap. ernet. in Udaipur313001,India ambastha@prl. ernet. in P. K. Manoharan Radio Astronomy Centre H. M. Antia Tata Institute Tata Institute of Fundamental Research of Fundamental Research P. O.Box 8 Homi Bhabha Road Udhagamandalam (Ooty) 643001, Mumbai400005,India India antia@tifr. res. in mano@racooty. ernet. in ArvindBhatnagar Udaipur Solar Observatory P. Ulmschneider Physical Research Laboratory Institut fur .. Theoretische Astrophysik P. O. Box No. 198 Univ. Heidelberg Udaipur313001,India Tiergartenstr. 15 arvind@prl. ernet. in 69121Heidelberg,Germany ulm@ita. uni-heidelberg. de S. M. Chitre Department of Physics University of Mumbai P. Venkatakrishnan Mumbai400098,India Udaipur Solar Observatory kumarchitre@hotmail. com Physical Research Laboratory P. O. Box No. 198 BholaN. Dwivedi Udaipur313001,India Department of Applied Physics pvk@prl. ernet. in Institute of Technology Banaras Hindu University Varanasi221005,India dwivedi@banaras. ernet. in TableofContents OverviewofSolarPhysics S. M. Chitre...1 1 Introduction...1 2 CompositionandStructureoftheSun...3 2. 1 EquationsofStellarStructure...4 2. 2 TheStandardSolarModel...7 3 ProbesoftheSun'sInterior...10 3. 1 SolarNeutrinoProblem...