Show 1 -- photosphere & sunspots SUN COURSE - SLIDE SHOW 4 Show 2 -- corona & solar cycle Today: Sun today + waves + prominences +UFOs Show 3 -- SOHO Sun today from SoHO Photo sphere Magnetic Field Corona (2.0 MK) LASCO C2 2. Waves on Sun - 4 exs (i) Waves in penumbra of sunspot (ii) Wave from Flare In photosphere (MDI) (8-100 km/s 70 mins) (iii) Solar Interior Guitar string can oscillate in different normal modes Sun too Recently SOHO discovered several million !! 3D Schematic Sound waves -reflected at top/ refracted at bottom Use properties to infer structure interior Helioseismology - trapped in convection zone - different waves sense diff. regions i.e., wave turns !! (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 3. Prominences On disc in Halpha, see long, thin filaments 200 Mm x 6 Mm Dark - cutting out light from below Inside a.r. - small Outside - large (feet) At limb - 50 Mm i.e. in corona On Disc 3D Structure At Limb Fine Structure -> transverse magnetic field inclined to axis Large Quiescent Prominence Active Region Prominence --> Field along prominence --> Magnetic flux tube In Eclipse Properties Immense, dense, cool vertical sheet of plasma in corona Density m -3 (1000 corona) Temperature 10, 000 K ( 0.01 corona) Change slowly in shape --- long-lived (1-200 days) Much fine structure Reach down in series of feet Lie along polarity inversion line At some stage, may become unstable - ascend and disappear: An erupting prominence Generally reform in same place Polarity inversion line Erupting Promin ence Finally - Granpa