1. White-Light Flares: TRACE and RHESSI Observations H. Hudson (UCB), T. Metcalf, J. Wolfson (LMSAL), L. Fletcher & J.I. Khan (Glasgow)

2. White-Light Flares “White light” is formed deep in the solar atmosphere and is therefore energetically important (also note “white-light prominences”) White-light (and UV) continuum emission associates well, at least in part, with the hard X-ray impulsive phase There are some observations from space prior to TRACE (Yohkoh; Matthews et al., 2003), but TRACE and RHESSI are better

3. Observational questions to be asked What are the observational characteristics of the new TRACE capability? Is the white-light/hard X-ray association always there? Do the TRACE broad-band observations differ morphologically from earlier observations? Do white light and UV sources match? Is white-light emission present in every flare in a proportional manner?

4. Initial database TRACE catalog => events with <10 s cadence in white light and full resolution, GOES C and above Total event list consists of 33 events during RHESSI operations through 2004 15 events studied thus far (X: 1; M: 11; C: 3) All 15 events have TRACE WL response All 15 events have RHESSI hard X-ray response

5. TRACE The TRACE white light channel has significant contributions from 1700 Å to 1  m The TRACE pixel size is 0.5” TRACE WL images show solar granulation, sunspots and faculae similar to other imaging at short wavelengths UV contributions to the white light channel can be reduced by subtracting the TRACE 1700 channel.

6. AGU/SPD May 27, 2005 TRACE spectral Response Solar-cycle modulation (Lean, 1997)

7. Event list 13-FEB-02 07:12:00 C7.8 TRACE RHESSI >07:03 UT 26-JUL-02 00:10:00 M4.9 TRACE RHESSI >00:32 26-JUL-02 19:03:00 M1.0 TRACE RHESSI 4-OCT-02 05:38:00 M4.0 TRACE RHESSI 4-OCT-02 22:43:00 M2.7 TRACE RHESSI >22:42 12-NOV-02 18:56:00 M2.9 TRACE RHESSI >19:01 11-JUN-03 20:14:00 X1.6 TRACE RHESSI >20:22 12-JUN-03 01:30:00 M7.3 TRACE RHESSI 23-OCT-03 02:41:00 M2.4 TRACE RHESSI 23-OCT-03 07:08:00 M3.2 TRACE RHESSI >07:07 8-JAN-04 05:07:00 M1.3 TRACE RHESSI 8-JAN-04 16:41:00 C1.3 TRACE RHESSI >16:39 9-JAN-04 01:44:00 M3.2 TRACE RHESSI 22-JUL-04 00:32:00 M9.1 TRACE RHESSI

8. C7.8 13-Feb-02 WL contrast ~20% noise @ 1.8% per pixel WL observed during RHESSI 25-50 keV UV contours relatively extended WL sources are patches unresolved by TRACE EVENT #1 WL+1700AWL difference

9. Six events from survey, 128x128 arc s

10. WLF is impulsive: event #5 (M4.9) GOES TRACE WL

11. AGU/SPD May 27, 2005 TRACE WLTRACE 1700 A

12. AGU/SPD May 27, 2005 A gradual white-light event: Neupert effect

13. AGU/SPD May 27, 2005 A gradual white-light event: RHESSI overlay

14. AGU/SPD May 27, 2005

15. Conclusions WL emission, as seen by TRACE, shows rapid small-scale features and closely resembles the UV morphology The data confirm the impulsive-phase association with hard X-rays, also found for extended non-thermal phase Sources may be extended in area, but include many tiny (arc-s scale) emission patches The data are consistent with the idea that white light correlates with total flare energy Extended events show similar morphology and don’t require further classification Contrasts can exceed 100%

16. AGU/SPD May 27, 2005 World’s record white-light flare? C1.3!!

17. Observational questions half-answered What are the observational characteristics of the new TRACE capability? Great Is the white-light/hard X-ray association always there? Yes Do the TRACE broad-band observations differ morphologically from earlier observations? Somewhat Do white light and UV sources match? TBD Is white-light emission present in every flare in a proportional manner? Yes

18. AGU/SPD May 27, 2005 Important open questions What can we learn about WLF spectra from the new data (not only TRACE, but MDI, GONG, IVM, etc…)? What will the improved knowledge of flare energetics tell us?

19. The First Observation of a Solar Flare Carrington 1859