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
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
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