SUN COURSE - SLIDE SHOW 7 Today: waves

(i) Waves in penumbra of sunspot Waves on Sun - 4 exs (i) Waves in penumbra of sunspot

Image enhanced

(ii) Wave from Flare In photosphere (MDI) (8-100 km/s 70 mins)

(iii) ? Structure of Solar Interior Guitar string can oscillate in different normal modes Sun too Recently SOHO discovered several million !! 3D Schematic

Different modes

Sound waves - trapped in convection zone -reflected at top/ refracted at bottom i.e., wave turns !!

Wave paths

SOHO MDI - Line of sight velocity

Close-up

SOHO -- MDI Deduces frequencies: Measures velocity of Sun's surface at million pts/min Deduces frequencies: Deduced T(r) -- agrees with model to < 1%

Power spectrum from MDI Variation of sound speed with depth.

--> Sun’s Internal Rotation Rate At surface: * Faster at equator -- Expect: * const. on cylinders * B generated throughout conv. zone Surprise: -- const on radial lines -- intense shear layer ? site dynamo

The Sun’s Internal Rotation Rate Angular velocity constant on radial lines in the convection zone. Radiative interior in solid body rotation. Thin layer of strong radial shear at the base of the convection zone – tachocline.

See below sunspot by t-distance seismology Wave speed slower - cooler Wave speed higher - B

(iv) Possibly Important for Heating Corona to few MK 2 mechanisms: Reconnection or Waves Originally suggested sound waves - > generate by turbulence - propagate up - shocks But - not observed - magnetic regions hotter ?? Magnetic waves

From TRACE discovered waves after eruption

Wave initiated by a flare

Numerical experiment

(v) Chromosphere/T.R are not static plane layers ! MHD Simulation Corona t. region Chromor Photor light/ dense. Chromosphere pervaded by waves Mode conversions where Cs=Ca

That’s why we have developed a theory for So That’s why we have developed a theory for Magnetic Waves ? Waves heat atmosphere Not corona -- amplitude of waves much too low Chromosphere ?? -- wave power factor 10 too small (Fossum & Carlsson, 2005) But wave theory important for new field of “Coronal Seismology” -- deduce properties of corona