Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare |
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Peter Gömöry Submitted: 2016-02-16 13:12
We analyzed high-cadence sit-and-stare observations acquired with theHinode/EIS spectrometer and HXR measurements acquired with RHESSIduring an M-class flare. During the flare impulsive phase, we observeno significant flows in the cooler Fe XIII line but strong upflows, upto 80-150 km s-1, in the hotter Fe XVI line. The largest Doppler shiftsobserved in the Fe XVI line were co-temporal with the sharp intensitypeak. The electron density obtained from a Fe XIII line pair ratioexhibited fast increase (within two minutes) from the pre-flare levelof 5.01x109 cm-3 to 3.16x1010 cm-3 during the flarepeak. The nonthermal energy flux density deposited from the coronalacceleration site to the lower atmospheric layers during the flarepeak was found to be 1.34x1010 erg/s/cm2 for a low-energycut-off that was estimated to be 16 keV. During the decline flarephase, we found a secondary intensity and density peak of loweramplitude that was preceded by upflows of 15 km s-1 that were detectedin both lines. The flare was also accompanied by a filament eruptionthat was partly captured by the EIS observations. We derived Dopplervelocities of 250-300 km s-1 for the upflowing filament material.Thespectroscopic results for the flare peak are consistent with thescenario of explosive chromospheric evaporation, although acomparatively low value of the nonthermal energy flux density wasdetermined for this phase of the flare. This outcome is discussed inthe context of recent hydrodynamic simulations. It providesobservational evidence that the response of the atmospheric plasmastrongly depends on the properties of the electron beams responsiblefor the heating, in particular the steepness of the energydistribution.
Authors: Gömöry, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K.
Projects: Hinode/EIS
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Publication Status: Accepted for publication in Astronomy and Astrophysics
Last Modified: 0000-00-00 00:00
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