Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Microflare Heating From RHESSI and Hinode Observations Ryan Milligan NASA-GSFC

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Energy released during flares… Is divided between: –Directly heating plasma in the corona at the magnetic reconnection site –Accelerating electrons out of the thermal distribution These in turn drive chromospheric evaporation, filling the loop with high-temperature plasma This aim of this study is to investigate the mechanism responsible for unusually high- temperatures observed during a microflare using RHESSI and Hinode

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC SOT Ca IIEIS Fe XVXRT Ti_poly Red = downflows Blue = upflows Fe XXIV 6-12 keV He II Fe XII Fe XV

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Spectrum taken from 1 minute at flare peak Corrections for pulse pile-up and gain offset were applied RHESSI Spectral Analysis

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Gain offset correction Before the anneal RHESSI calibration was poorly known Data could be modified manually by fine-tuning the gain offset drm_mod works only for single detector

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Gain offset correction Before the anneal RHESSI calibration was poorly known Data could be modified manually by fine-tuning the gain offset drm_mod works only for single detector

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Pileup correction Criteria for pileup –Total counts >10 4 –Excess emission at ~13 keV (twice the peak at 6.7 keV in A0 state) pileup_mod works only for single detector

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Pileup correction Criteria for pileup: –Total counts >10 4 –Excess emission at ~13 keV (twice the peak at 6.7 keV in A0 state) pileup_mod works only for single detector

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Peak temperature of 15±1 MK No evidence for nonthermal emission Presence of Fe/Ni feature at 8 keV confirms high- continuum temperature Spectral Fit Results

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Hannah et al. (2008)Feldman et al. (1996) Statistics of Flare Temperatures

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Klimchuk et al. (2008) EBTEL 0D hydro-code Models plasma parameters for various forms of injected energy Peak temp is higher when less energy is used to accelerate electrons

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC If the flow in XRT is real: Plasma flows left to right along the loop Evaporation occurs at X-ray temperatures Fe XV redshifts are “chromospheric condensation” due to the overpressure of rising material - too hot according to models - requires electron beam Blueshifts at right FP are due to the heat flux along the loop

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC If flow in Fe XV is real: Plasma flows from right to left along the loop Brightening in XRT is actually a build up of hot material being deposited in the left leg of the loop Upflow velocity consistent with evaporation due to thermal conduction

Cycle 24 Meeting, Napa December 2008 Ryan Milligan NASA/GSFC Conclusions Above-average temperature of 15 MK was observed during a B-class flare Absence of nonthermal emission plus low- velocity upflows suggest that direct heating in the corona was responsible –Consistent with recent hydrodynamical model –Evaporation still required to supply material to corona Contradicting flow patterns were observed by EIS and XRT