White-Light Flares: TRACE and RHESSI

Observations

H. Hudson (UCB), J. Wolfson (LMSAL)

& T. Metcalf (CORA)

White-Light Flares (WLF)

• “White light” is formed deep in the solar atmosphere and is therefore energetically important (also note “white-light prominences,” which are up in the corona)

• White-light (and UV) continuum emission associates well, at least in part, with the hard X-ray impulsive phase (Neidig)

• There are some WLF observations from space prior to TRACE (Yohkoh; Matthews et al., 2003), but TRACE and RHESSI give us much better data

• Solar-B should be able to make wonderful observations of WLF

Event Selection

• TRACE catalog => events with <10 s cadence in white light and full resolution, GOES C and above, full RHESSI coverage

• Total event list consists of 33 events during RHESSI operations through 2004

• 11 events (X: 0; M: 7; C: 4)• All 11 events have TRACE WL response• All 11 events have RHESSI hard X-ray response• 10/11 events appear to be largely footpoints; one has obvious coronal

sources as well

TRACE spectralResponse

Solar-cycle modulation(Lean, 1997)

Event Lista

aHudson et al., Solar Phys. (in press, 2005)

2002 Oct. 405:35:49 UT

2002 Oct. 510:41:58 UT

WL versus UV (1700A)

TRACE WL WL difference 1700 A

Intermittency

32 x 68 arc s frames

WL-1700A Comparison

Reversed colors!

WL-hard X-ray comparison

Conclusions

• WL emission, as seen by TRACE, is not resolved at angular resolution 1”, temporal resolution 10 s

• The data confirm a strong association with hard X-rays

• Sources may be extended in area and include loop tops

• “True” WL is morphologically different from UV

• TRACE WL contrasts can exceed 100% even for flares below X class

TRACE• The TRACE white light channel has significant

contributions from 1700 Å to 1 m, 0.5” pixels

• UV contributions to the white light channel can be reduced by subtracting the TRACE 1700 channel

RHESSI• Energy range 3 keV - 15 MeV, resolution

(FWHM) ~ 1 keV

• Time resolution 4 sec without image

deconvolution

2004 Jan. 901:40:17 UT

2003 June 1201:27:01 UT

2002 Nov. 218:16:04 UT

2004 July 2200:29:56 UT

2003 Oct. 2302:39:49 UT

2002 July 2503:59:04 UT

2002 July 2619:00:25 UT

2004 July 2413:34:38 UT

Loop-top WL emission (“WL prominence”)

Event of 2002 Nov. 12, 17:58 UT

Statistical Properties offixed differences