High Time Resolution EUV Spectroscopy of Chromospheric Evaporation and Other Solar Phenomena
Abstract
We present light curves and Doppler velocity measurements for a solar flare observed at high time resolution with SOHO's CDS (9.8 s) and Yohkoh's BCS (9.0 s). CDS was able to perform rapid cadence spectroscopy because it was operated in sit-and-stare mode. Coordinated imagery from EIT and TRACE reveal that the CDS slit was positioned directly over the location of flare onset. Emission lines formed at transition region temperatures exhibited upflows of 40 km/s during precursor brightenings, which suggests gentle chromospheric evaporation during those events. The same lines showed downflows of 40 km/s during the flare impulsive phase, when emission lines formed at temperatures around 10 MK exhibited blueshifts. We interpret this to indicate momentum balance between the hot upflowing plasma and the cool downflowing material during chromospheric evaporation. In our quest for rapid cadence EUV spectra during big solar flares, we have also observed numerous less energetic events like nanoflares and blinkers. JWB acknowledges support through NASA grant NAG5-11757; KJHP acknowledges support through an NRC Research Associateship.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2005
- Bibcode:
- 2005AGUFMSH44A..07B
- Keywords:
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- 7519 Flares;
- 7549 Ultraviolet emissions;
- 7554 X-rays;
- gamma rays;
- and neutrinos;
- 7594 Instruments and techniques