sun course - slide show 4
DESCRIPTION
SUN COURSE - SLIDE SHOW 4. Show 1 -- photosphere & sunspots. Today: Sun today + waves + prominences +UFO’s. Show 2 -- corona & solar cycle. Show 3 -- SOHO. Sun today from SoHO. Photo sphere. Magnetic Field. Corona (2.0 MK). LASCO C2. 2. Waves on Sun - 4 exs. - PowerPoint PPT PresentationTRANSCRIPT
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
QuickTime™ and aYUV420 codec decompressorare needed to see this picture.
(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
QuickTime™ and aPhoto decompressorare needed to see this picture.
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