2. MRT workshop, August 10, 2004 Active-region magnetic structures and their perturbations by flares H.S. Hudson SSL/UCB

3. MRT workshop, August 10, 2004 Outline Description of a solar active region Magnetic structure Waves, oscillations, and restructuring RHESSI observations of eruptive flares

4. MRT workshop, August 10, 2004 TRACE 171A view of an active region, courtesy LMSAL “cool stars” Web material

5. MRT workshop, August 10, 2004 Mechanical properties of an active region in the corona Flares and CMEs are magnetically driven, according to consensus, from energy stored in the corona In such conditions, (low plasma  ), the mechanical stresses can be represented as a pressure and a tension Dissipation is normally slow The volume is electrically equipotential except for the Rosseland-Pannekoek potential

6. MRT workshop, August 10, 2004 G. A. Gary, Solar Phys. 203, 71 (2001) CH

7. MRT workshop, August 10, 2004 What are the loops? The loops show the direction of the magnetic field The X-ray visibility of the corona is a monotonic increasing function of the gas pressure In an active region, the loop dimensions are typically smaller than the scale height The footpoints of a loop lie in a transition layer at the appropriate pressure The magnetic field must be slightly depressed in the visible loops

8. MRT workshop, August 10, 2004 Lundquist et al., SPD 2004

9. MRT workshop, August 10, 2004 NOAA 10486, Haleakala IVM data,  cube Roumeliotis-Wheatland-McTiernan method pixel size ~3000 km ScaledNot scaled

10. MRT workshop, August 10, 2004 AR8210 courtesy J. McTiernan

11. MRT workshop, August 10, 2004 Conjecture: Most of the free energy in an active region is concentrated very near its base

12. MRT workshop, August 10, 2004 The normal state of the active- region corona is an equilibrium An equilibrium system will oscillate around its rest configuration if perturbed slightly We observe coronal oscillations via spectroscopy, photometry, and in movies The oscillations have small amplitudes and can be studied via MHD theory

13. MRT workshop, August 10, 2004 Kink-mode oscillations Flare waves associated with metric type II bursts often (12/30 cases) appear with TRACE loop oscillations These oscillations allow us to study the equilibrium state of the non-erupting part of the corona

14. MRT workshop, August 10, 2004 Aschwanden et al., Solar Phys. 206, 99 (2002)

15. MRT workshop, August 10, 2004 Narukage et al., PASJ 56, L5 (2004)

16. MRT workshop, August 10, 2004 SUMER’s oscillations Wang, T. J. et al., ApJ 574, L101 (2003)

17. MRT workshop, August 10, 2004 Yohkoh’s oscillations (BCS) Mariska, J. et al., SPD poster (2004)

18. MRT workshop, August 10, 2004 Schrijver et al., Solar Phys. 206, 69, 2002

19. MRT workshop, August 10, 2004 Three things the movie showed Early inward motions, prior to the eruption Dimming - the CME starting off Excitation of coupled normal modes in the arcade (arcade blowout)

20. MRT workshop, August 10, 2004 SXT observations of the blow-out of an X-ray “loop prominence system”

21. MRT workshop, August 10, 2004 Studying coronal equilibria On large scales the corona tends be stable We can study the equilibrium states via the oscillations; there are several modalities Propose to use “instrumented hammer” approach to characterize eigenstates Propose to study before/after equilibrium states using FASR and Solar-B

22. MRT workshop, August 10, 2004 H. Wang et al., ApJ 576, 497 (2002)

23. MRT workshop, August 10, 2004 Magnetic challenge: Can any existing model of a flare or CME properly describe the change in the coronal magnetic field?

24. MRT workshop, August 10, 2004 Cartoon showing magnetic implosion Post-event field Pre-event field Isomagnetobars Limb Hudson & Cliver, JGR 106, 25,199 (2001)

25. MRT workshop, August 10, 2004 Conclusions Unlike the cosmologists, we don’t have a standard model for a flare/CME - we do have cartoons, though: http://solarmuri.ssl.berkeley.edu/~hhudson/ cartoons/ http://solarmuri.ssl.berkeley.edu/~hhudson/ cartoons/

26. MRT workshop, August 10, 2004 Serious conclusions Extrapolation techniques to learn about the coronal magnetic field are inherently flawed It will be better in the future to assimilate more precise methods, such as - TRACE coronal imagery (direction of B) - FASR gyroresonance surfaces (magnitude of B) - Mechanical models (matching eigenfrequencies)

27. MRT workshop, August 10, 2004 From the Flare/CME Cartoon Archive http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/

28. MRT workshop, August 10, 2004 Null? Separatrices? Anzer-Pneuman, 1982

29. MRT workshop, August 10, 2004 Forbes, T., JGR 105, 23,153, 2000 Gallagher, P. personal communication 2004

30. MRT workshop, August 10, 2004

31. RHESSI observations of early inward motions

32. MRT workshop, August 10, 2004 Sui et al., 2004

33. MRT workshop, August 10, 2004 Sui et al., 2004