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Advanced Solar Theory: Observational Properties, MHD Equations, and Solar Dynamics

Dive into advanced solar theory with a comprehensive outline covering observational properties of the Sun, MHD equations, and solutions for varying magnetic Reynolds numbers. Explore magnetic equilibria, waves, solar winds, and phenomena like solar flares and coronal mass ejections. Historical milestones in solar observations, from ancient sunspots to modern space missions like SOHO and Solar Dynamics Observatory, are detailed. Key aspects of solar structure, including the atmosphere and sunspots, are examined, making it a critical resource for understanding solar physics and its complexities.

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Advanced Solar Theory: Observational Properties, MHD Equations, and Solar Dynamics

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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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