Show 1 -- photosphere & sunspots

SUN COURSE - SLIDE SHOW 4

Show 2 -- corona & solar cycleToday: Sun today + waves + prominences +UFO’s

Show 3 -- SOHO

Sun todayfromSoHO

Photo

sphere

Magnetic Field

Corona (2.0 MK)

LASCO C2

2. Waves on Sun - 4 exs (i) Waves

in penumbra of sunspot

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(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

ω =kcs , where

cs2 = γ p / ρ = γ RT ,

so T ↑⇒ k↓.

But k=(k r ,kθ ) and kθ const,

so k r decreases - 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

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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 10 17 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