white-light flares: trace and rhessi observations

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