2. Observing the Sun from space: Highlights from Yohkoh, SOHO, TRACE, RHESSI H.S. Hudson Space Sciences Lab University of California, Berkeley

3. March 27, 2006 L’Aquila 2 SUMMARY OF LECTURE I. Overview of the Sun 2. Observational technique 3. The solar space observatories 4. Informal access 5. Research frontiers 6. Conclusions, solved problems, new interesting questions

4. March 27, 2006 L’Aquila 3 Yohkoh soft X-rays Magnetic field I. Overview of the Sun

5. March 27, 2006 L’Aquila 4 Yohkoh SXT: The Solar Cycle

6. March 27, 2006 L’Aquila 5 Solar Atmosphere – Temperature and Emission Visible/IR UV/EUV

7. March 27, 2006 L’Aquila 6 How smooth is the Sun? * (Fivian et al. 2005) * Rough structure <1 mas, Oblateness ~ 10 mas

8. March 27, 2006 L’Aquila 7 Physical effects in transition zone Outwards through the thin layer between  5000 = 1 and the corona involves - a drop in opacity (thick/thin) - a loss of collisionality (Maxwellian/non) - a sudden decrease of plasma beta (high/low) This structure is thus complex, dynamic, and full of waves that become shocks - confused contribution functions; 3D structure - uncertainties in magnetic-field mapping

9. March 27, 2006 L’Aquila 8 De Pontieu et al. 2003

10. March 27, 2006 L’Aquila 9 G. A. Gary, Solar Phys. 203, 71 (2001) (v A ~ 200  -1/2 km/s) CH Distribution of coronal plasma  = P g /P B

11. March 27, 2006 L’Aquila 10 Photosphere – High Resolution Image Image from Swedish Vacuum Solar Telescope, La Palma, 24 July 2002. Sunspot umbrae Granules of rising hot plasma …here comes Solar-B!

12. March 27, 2006 L’Aquila 11 2. Observational technique Imaging (movie technique) - direct YSSST - synthesis YR Spectroscopy - simple Y - dispersive (e.g., stigmatic slit) SSS - non-dispersive (pulse counting) YYR Polarimetry Solar-B Y = Yohkoh S = SOHO T = TRACE R = RHESSI

13. March 27, 2006 L’Aquila 12 An example of imaging and spectroscopy (HRTS rocket)

14. March 27, 2006 L’Aquila 13 How to multiplex data Monochromatic imaging (x, y, ) Stigmatic slit (x, y, ) Non-dispersive (x, y, ) - low resolution at longer wavelengths

15. March 27, 2006 L’Aquila 14 3. The recent solar space observatories Yohkoh: HXT, SXT, BCS, WBS (1991-2001) SOHO: MDI, EIT, LASCO, MDI… (>1995) TRACE: UV/EUV imager (>2000) RHESSI: Rotating modulation collimators (>2002)

16. March 27, 2006 L’Aquila 15 Y S T R

17. March 27, 2006 L’Aquila 16 SXTYohkoh Soft X-rayGeneral HXTYohkoh Hard X-rayFlares BCSYohkoh X-ray spectraFlares/ARs CDSSOHO EUV spectraGeneral EITSOHO EUV imagesGeneral LASCOSOHO CoronagraphCMEs MDISOHO Visible Helioseismology, magnetography etc SUMERSOHO UV spectraAtmosphere UVCSSOHO Coronal UVCorona ImagerTRACE UV/EUVGeneral Spectral ImagerRHESSI HXR/  -ray Flares Some key instruments in space

18. March 27, 2006 L’Aquila 17 4. Informal access Each of the four missions sponsors some form of Web journalism Yohkoh science nuggets (http://ydac.mssl.ucl.ac.uk/nuggets/) SOHO Hot Shots (http://sohowww.nascom.nasa.gov/) TRACE picture of the day (http://trace.lmsal.com/POD/TRACEpod.html) RHESSI science nuggets (http://sprg.ssl.berkeley.edu/~tohban/nuggets/)

19. March 27, 2006 L’Aquila 18

20. March 27, 2006 L’Aquila 19

21. March 27, 2006 L’Aquila 20

22. March 27, 2006 L’Aquila 21

23. March 27, 2006 L’Aquila 22

24. March 27, 2006 L’Aquila 23 5. Research frontiers A single TRACE movie illustrates several discoveries from this era: - Dimming (CME/flare relationship) - Instability (loop disruption) - Macroscopic loop oscillations - Initial field contraction

25. March 27, 2006 L’Aquila 24

26. March 27, 2006 L’Aquila 25 Case studies Case study: Longcope et al., 2005 Case study: Sudol & Harvey, 2005 Case study: Kopp et al., 2004

27. March 27, 2006 L’Aquila 26 GONG SOHO/MDI B dB Flare of 2003 Oct. 29

28. March 27, 2006 L’Aquila 27 Flare of 2001 Aug. 25 GONG + TRACE 1600A Other examples with GOES times

29. March 27, 2006 L’Aquila 28 Interpretation of field changes The line-of-sight photospheric B field changes impulsively and irreversibly during every flare The patterns of change can guide us to a more complete understanding of the coronal restructuring: Will we at last have the means to observe flux transfer in flares directly? This can done much better with vector magnetograms at rapid temporal cadence (<< 1 min) - Solar-B? SDO? ATST? FASR?

30. March 27, 2006 L’Aquila 29 Longcope et al. 2005 Example of magnetic domain structure based on photospheric fields

31. March 27, 2006 L’Aquila 30 Flare luminosity The major solar space observatories are not the whole story Kopp et al. (2004) => L flare ~ 10 2 L x Flare luminosity has a major contribution from the impulsive phase at UV/EUV wavelengths

32. March 27, 2006 L’Aquila 31 Kopp et al., 2004

33. March 27, 2006 L’Aquila 32 Conclusions The four CCD-era solar space observatories have revolutionized solar physics The data are informally accessible, but are also generally in the public domain with their software New missions will follow soon: Solar-B, STEREO, SDO

34. March 27, 2006 L’Aquila 33 New exciting questions Can before/after magnetograms identify magnetic reconnection in flares/CMEs? Does the pre-flare corona initiate the nonthermal process? Can we obtain closure on CME mass, energy, and helicity? How do we relate the solar cycle to stellar X-ray luminosities? How do we explain HXR/  -ray footpoint disagreements? And many more…