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Advanced Solar Theory (MT5810)

Advanced Solar Theory (MT5810). OUTLINE. Observational properties of the Sun MHD equations (revision) Induction equation - solutions when R m <<1, >>1 Magnetic equilibria Waves Solar wind Reconnection Instabilities. Books: Solar MHD -- ER Priest Camb. Encyc. of the Sun -- K Lang

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Advanced Solar Theory (MT5810)

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  1. Advanced Solar Theory (MT5810) OUTLINE Observational properties of the Sun MHD equations (revision) Induction equation - solutions when Rm <<1, >>1 Magnetic equilibria Waves Solar wind Reconnection Instabilities Books:Solar MHD -- ER Priest Camb. Encyc. of the Sun -- K Lang Nearest Star -- L Golub & J Pasachoff

  2. 1.1 History 1. Observations Ancient observations - sunspots (chinese, greeks) - forgotten Galileo (1610) rediscovered sunspots 1851 -- first photograph of corona (eclipse) 1859 -- first solar flare observed 1908 -- sunspots have strong B 1956 -- foundations of MHD (Cowling) 1957 -- satellite observations of interplanetary medium 1980’s & 90’s -- development of MHD -- space observations (Skylab 73-74, Yohkoh 91-05, SOHO 95 - …, TRACE 98 - …, RHESSI 02 - …

  3. Future Space Missions STEREO (NASA) April 2006 * Two satellites * _ _ _ _ _ _ _ _ _ _ _ _ _* Solar B (Japan-US-UK) Sept 2006 * Connections surface/corona Solar Dynamics Observatory 2008 * _ _ _ _ _ _ _ _ _ _ _ _* Solar Orbiter (ESA) 2012 * _ _ _ _ _ _ _ _ _ _ _ _ *

  4. Ball of gas held together by gravity 1.2 Properties of the SUN ? Tsurface_ _ _ _ _ ? Mass/ s. system _ _ _ _ _ ? Chemical composition _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ? Radius _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ? Age _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

  5. Some other properties ? Mean distance from Earth 93 million miles = 150 million km _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ? Rotation period = 25 days (equator), 37 days (poles) ? Mean density = 1.4 x 103 kg m-3 _ _ _ _ _ _ _ _ _ _ ? Surface gravity = 274 m s-2 _ _ _ _ _ _ _ _ _ _ ? Escape velocity at surface = 618 km s-1_ _ _ _ _

  6. Overall Structure Interior --> Core, Convection zone _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Atmosphere --> Photosphere, Chromosphere, Corona

  7. Photosphere Temperature 6000 K Covered with turbulent convection cells: *_ _ _ _ _ _ _ _ _ _ * (1 Mm) *_ _ _ _ _ _ _ _ _ _ * (15 Mm) ?? why

  8. Amazing images [70 km] from La Palma (Canaries)

  9. In close-up:points, flowers, ribbons(created by magnetic fields)

  10. 1.3 SUNSPOTS Photosphere --> Sunspots Galileo discovered (1610) w. telescope Dark because cool But why cool ? *_ _ _ _ _ _ _ _ _ _ _ _ _ _* ??? why

  11. StunningImagefrom La Palma Penumbral structure created by B

  12. Map ofPhotospheric Magnetic Field White -- towards you; Black -- away from you Regions around sunspots -- bipolar * _ _ _ _ _ _ _ *

  13. 1. Intense magnetic fields over whole Sun SURPRISES: -- • _ _ _ _ _ _ • _ _ _ _ _ _* ?? why 2. Patterns of sunspots/active regions ?? why

  14. 1.4 CORONA (Turkey, 1999) Fine structure Magnetic tubes “prominences” SURPRISE (1940) *_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _* ??why Next: Egypt, March 2006

  15. Picture with X-ray telescope: * *

  16. Yohkoh A magnetic world Amazingly rich variety of MHD phenomena

  17. TRACE (Active region) - from above

  18. *_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ * From side: Magnetic field dominates plasma creates intricate structure/ heats ?? how

  19. 1.5 Solar Activity On top of the “Quiet Sun” (ie the background photosphere, chromosphere & corona), there are several types oftransient phenomena: (i) _ _ _ _ _ _ _ _ _ (ii) _ _ _ _ _ _ _ _ _ (iii) _ _ _ _ _ _ _ _ _ (iv) _ _ _ _ _ _ _ _ _

  20. (ii) Prominences On disc in chromosphere, see as long, thin structures Dark - cutting out light from below * _ _ _ _ _ _ __ _ _ _ _ _ __ _ _ _ _ _ _ _* ???

  21. Sometimes erupt - [look like twisted tube] why ??

  22. (iii) Solar Flare Sudden brightening in chromosphere & corona near sunspots *_ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ * How ??

  23. SOHO Coronagraph -- Artificial eclipse (iv) Coronal Mass Ejections Discovered huge ejections of plasma ?? *_ _ _ _ _ _ _* Can reach Earth - communications / satellites

  24. 1.6 SOHO(Solar & Heliospheric Observatory) Launched 1995. Orbiting Sun at point in phase with Earth Observing Sun continuously for 1st time (ESA/NASA) --> 1st comprehensive view of Sun MANY NEW SURPRISES

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