Explosive Chromospheric Evaporation and Warm Rain in a C3.1 Flare Observed by IRIS, Hinode/EIS, and RHESSI

Journal Article · Tue Oct 10 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA8A68· OSTI ID:22875718

Brosius, Jeffrey W.

IRIS and EIS observed a GOES C3.1 flare in stare mode on 2014 March 15. The GOES flare started at 00:21:35 and peaked at 00:26:30 UT. The IRIS slit pointed near the center of the flare, while the EIS slit pointed 35{sup ′′} to its west. About 4 minutes before the GOES flare start, the IRIS C ii and Si iv intensities became (and remained) greater than their pre-flare averages, indicating that the flare had begun and that the chromosphere and transition region were involved. IRIS first detected blueshifted Fe xxi emission at 00:22:42 UT, by which time the C ii and Si iv intensities had increased by factors around 100 and their profiles were redshifted. Simultaneous, cospatial blueshifted Fe xxi emission with redshifted C ii and Si iv emission indicates explosive chromospheric evaporation. EIS spectra reveal Fe xxiii emission that is too weak to measure velocities, and intensity enhancements by factors about 1.7 in the Fe xiv and Fe xvi emission. Lines from both of these coronal ions show redshifts ≈9 km s{sup −1} around 00:24:00 UT, and the Fe xiv 264.7/274.2 intensity ratio reveals an increase of n {sub e} from (1.03±0.20)×10{sup 9} before to (3.58±0.68)×10{sup 9} cm{sup −3} during the flare. The redshifted coronal line emission and increased n {sub e} are consistent with warm rain falling and accumulating in the remote area observed by EIS. A fit to the RHESSI hard X-ray spectrum yields a nonthermal energy injection rate of 4.9×10{sup 26} erg s{sup −1}, from which we estimate a HXR beam energy flux range consistent with explosive evaporation.

• OSTI ID: 22875718
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 848; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHROMOSPHERE
EMISSION
EXPLOSIVES
GAMMA RADIATION
HARD X RADIATION
RED SHIFT
SOLAR FLARES
SUN
ULTRAVIOLET RADIATION
VELOCITY
X-RAY SPECTRA