OUR NEW SUN (Cool Stars 15, July 21, 2008) Eric Priest Hinode X-ray Telescope

Solar-Stellar Connection -- Workshop -- Bonas (1980)

1. INTRODUCTION Revolution in solar physics over past 10 years. Many advances -- profound implic ns other stars. Fund l qns nature Sun not yet answered -- but major progress. Here, brief overview of new Sun revealed by these advances (contrib ns solar group) -- but leave you to make own connections

Solar MHD Group at St A: Permanent: Eric Priest -- reconnection, coronal heating Alan Hood -- instability, flux emergence Bernie Roberts -- waves, seismology Thomas Neukirch -- particle acceleration Andrew Wright -- magnetospheres Clare Parnell -- photospheric flux, coronal heating Duncan Mackay -- global fields, prominences, CMEs Ineke De Moortel -- coronal seismology Postdocs: Vasilis Archontis -- flux emergence Rhona Maclean -- magnetic topology Andrew Haynes -- 3D reconnection James McLaughlin -- nonlinear MHD waves Stephane Regnier -- force-free fields David Pascoe -- MHD waves + 15 PhD students (in Maths Dept)

1st Professor of Maths: James Gregory ( ) Co-founder of Calculus Invented Gregorian Telescope Traditionally close link Mathematics - Astronomy -- Taylor expansions -- Differentiation is inverse of integration -- Change of variable in integration [-- Series for sin x and tan x]

James Gregory (1638) Lab -- see meridian line [& clock (1st to beat < 1 sec)]

Advances: from Theory + Observations: Yohkoh ( ): dynamic corona [soft & hard X-rays] SoHO (1995-…): interior + atmosphere TRACE (1998-…): fine structure corona [EUV]

STEREO (OCT …): 2 spacecraft -- stereoscopic images of corona and CMEs [see Simon Plunkett talk] Hinode (Sept, …) Solar Optical Telescope （ SOT ） EUV Imaging Spectrometer （ EIS ） X-ray Telescope （ XRT ） -- high-resolution connections photosphere & corona

Interior: Core (< 0.25 R 0 ), [R 0 = 700 Mm] Convection zone (> 0.7 R 0 ) Atmosphere: Photosphere (6000K), Chromosphere, Corona Overall Structure of Sun

2. SOLAR INTERIOR Several million global normal modes (few mm/sec amplitude) Helioseismology --> T(r) -- [agrees with model to < 1%] Internal rotation

Internal Rotation - At surface:faster at equator Expect:* const. on cylinders * B generated throughout conv. zone Surprise: -- const on radial lines Site dynamo: but details v. uncertain: Tachocline ?? nature instability, validity mean-field theory, coupling to cz & interior, nature of meridional flow. ?? Small-scale dynamo near surface -- intense shear layer

Covered with turbulent convection cells: “Granulation” (1 Mm) “Supergranulation” (15 Mm) 3. PHOTOSPHERE

Photospheric Magnetic Field  Active regions  Intense magnetic fields over whole Sun -- vertical -- at edges supergranule cells White -- towards Black -- away

But new white light obsns 0.1” from Swedish telescope! Zoom from full disk by factor 100 to 70 km resolution [Carlsson et al]

** Hinode: Clare Parnell: Measure B at resolution 0.1arcsec [10 16 Mx] -- much more magnetic flux than thought -- concentrated around granules (Going from SoHO MDI to Hinode, flux increases by 50%); --> surprising distrib flux [wed]. Another discovery: horizontal field at edges granules [mean 50 G] >> Vertical field between grans [10 G] (Tsuneta & Lites)

Radiative MHD Simul n [Hansteen &Carlsson] Corona Chromo r Photo r light/ dense. t. region Chromosphere/t. region not static plane layers ! in response to phot c granulation

-- explain formation of Plasma Jets (ubiquitous in Hinode) & dynamic heating in corona by reconnection. t =10 min t =55 min 3D MHD flux emergence simul ns (Hood,Archontis,…)

4. 3D RECONNECTION-- In 3D, reconnection at nulls or at non-nulls (QSLs) In 2D, reconnection at null points, B = 0 In 2D, magnetic lines slip through plasma -- but change connections only at X Many New Features (Hornig, Pontin, Wilmot-Smith, Priest)

In 3D --fieldlines continually change their connections in D -- flux tubes split, flip and do not rejoin perfectly !

5. CORONA - few 10 6 K- intricate loops (TRACE)

Topology of Coronal Fields - Complex In 2D -- Separatrix curves In 3D -- Separatrix surfaces -- intersect in Separator * Reconnection transfers flux * Parnell, Maclean, Haynes developing standard codes to find “Skeletons” sunspots

MHD Model of elementary interaction driven by motion 2 photo c sources (Haynes, Parnell et al 2007) Separator Negative Separatrix Surface Positive Separatrix Surface - and + phot c magnetic fragments in overlying B.  Separatrix surfaces. Move sources & watch Interaction  flux tube joining sources

Cross-sections of Separatrix Surfaces 2 separators 5 separators Separatrix surfaces (positive, negative) & Separators ( ) Number of separators: X

HOW is CORONA HEATED ? Construct coronal field lines from observed magnetograms - (Close, Parnell, Priest) Time for all field lines to reconnect only 1.5 hours

--> Coronal Tectonics Model Each ‘Coronal Loop’ --> surface in many B sources  Flux from each source separated by (separatrix) surfaces  As sources move --> J sheets on surfaces --> Reconnect --> Heat  Corona filled w. myriads of J sheets, heating impulsively

Other aspects of Corona: (i) Model global evolution of: Sun’s surface B r -- flux emergence, differ l rotation, meridional flow, diffusion; --> nonlinear force-free coronal B --> location & chirality of prominences (Mackay and Yeates) (ii) Use techniques of coronal seismology to deduce properties of corona from observed oscillations (De Moortel & Roberts)

Ulysses: Sunspot minimum Sunspot maximum 6. SOLAR WIND - Velocity (polar plot) FAST(700 km/s) coronal holes SLOW (300 km/s) streamers IRREGULAR But mechanism for accelerating wind unkown

Hinode: Sakao discovered strong outflows from active regions at 140 km/s as Doppler shift in Fe XV:

7. ORIGIN of SOLAR FLARES /CORONAL MASS EJECTIONS -- cause of eruption not yet identified. ? instability or catastrophe Working on: *Storage preflare energy in nonlinear force-free field (Regnier) *Topology of field (Maclean, Parnell) *3D reconnection process (Priest, Parnell ….) *Particle acceleration mechanisms (Neukirch) [DC E and collapsing trap]

Outer Corona [from SOHO] on October 28, 2003 Coronal Mass Ejection 2000 km/s Snow -- rel c particles

Thurs Aurora in St Andrews

Zoom -- power of SoHO -- cf diff. layers

8. CONCLUSIONS  Solar Physics - golden age - space observations  Dynamo - not simple model  Flux emerges thro’ photo sph over range scales  Corona complex topology -- ? heated by tectonics  Solar wind highly variable -- mechanism unknown  Huge progress towards fundamental qns S. Phys.  Solar flare mechanism -- many complex parts  3D reconnection -- completely different from 2D Encourage forge sc. links with solar physics

Enjoy the rest of your week Enjoy your week in St A