1. Preflare physical conditions inferred from Hinode Hugh Hudson (UC Berkeley) and Ed DeLuca (CfA)

2. Comments Theorists want to know what conditions prevail when a flare happens Hinode has the best resolution ever We reconnoiter the XRT data EIS data are in principle much more powerful for this purpose

3. Methods Identify flares/microflares in XRT movies Try to identify common footpoints Do RTV-based analysis to get limits

5. B3.2 Three Microflares

6. Microflare #1

7. Microflare #1: New features flare

8. Microflare #2

9. Microflare #2: Could be pre-existing

10. Microflare #3

11. Microflare #3: New features flare

12. Preflare (log)Flare (log)Difference

13. C-class flare of 2007 June 5

16. Analysis for preflare (T, n) S = n 2 f(T)  V XRT response T ~ (pL) 1/3 RTV law => S ~ T 4 f(T) Tf(T) 1/4 = T ref f(T ref ) 1/4 * (S/S ref ) 1/4 Solve for T = T(T ref, S) The pre-event density n follows from the RTV scaling since n ~ T 2 for a fixed reference geometry (nearby loop)

17. Results of RTV-based analysis Temperature: < 1MK Density: < 1 x 10 8 cgs Plasma beta: < 1 x 10 -4 Alfvén speed: > 0.1 c (100 G)

18. Brosius & Phillips, ApJ 613, 580 (2004): TRACE/SOHO/Yohkoh comparisons; a possible counterexample?

20. Conclusions In several microflares and one C-class event, XRT usually sees an “empty corona” prior to the flare (at least 3/4 cases) Using RTV scaling to compare with similar AR loops, we find low temperatures and densities These imply low plasma beta and high Alfvén speeds (> 0.1c)

21. What is there before the flare? Hinode can tell us where Magnetic heating's brought to bear Upon coronal plasma rare An X-ray image just before Shows the active-region core To have some loops, and rather more Emptiness, void loops in store Does a flare loop coincide With preflare loop, or lie beside? The blink technique that we've applied Allows us quickly to decide. And thus we set an upper limit. We must now interpret it; To get a pre-flare pressure fit RTV can help a bit Conclusions we can now unfold: The pre-flare plasma's thin and cold, Do not believe the textbooks old Hinode's worth its weight in gold A curiosity indeed! That flare occurrence seems to need Cold voids to be there as a seed Flare instability to breed. Without loop interaction Can we trust in reconnection? Or can our (TBD) theory section Invoke some brilliant new direction ?