Where Is the Chromospheric Response to Conductive Energy Input From a Hot Pre-Flare Coronal Loop?

Abstract

Before the onset of a flare is observed in hard X-rays there is often a prolonged pre-flare or pre-heating phase with no detectable hard X-ray emission but pronounced soft X-ray emission suggesting that energy is being released and deposited into the corona and chromosphere already at this stage. This work analyses the temporal evolution of coronal source heating and the chromospheric response during this pre-heating phase to investigate the origin and nature of early energy release and transport during a solar flare. Simultaneous X-ray, EUV, and microwave observations of a well observed flare with a prolonged pre-heating phase are analysed to study the time evolution of the thermal emission and to determine the onset of particle acceleration. During the 20 minutes duration of the pre-heating phase we find no hint of accelerated electrons, neither in hard X-rays nor in microwave emission. However, the total energy budget during the pre-heating phase suggests that energy must be supplied to the flaring loop to sustain the observed temperature and emission measure. Under the assumption of this energy being transported toward the chromosphere via thermal conduction, significant energy deposition at the chromosphere is expected. However, no detectable increase of the emission in the AIA wavelength channels sensitive to chromospheric temperatures is observed. The observations suggest energy release and deposition in the flaring loop before the onset of particle acceleration, yet a model in which energy is conducted to the chromosphere and subsequent heating of the chromosphere is not supported by the observations.

The Spectral Content of SDO/AIA 1600 and 1700 Å Filters from Flare and Plage Observations

“…Inglis & Christe 2014, Wright et al 2017) and flares (e.g. Hannah & Kontar 2013, Battaglia et al 2014, Simões et al 2015a). In the UV range, however, the presence of recombination edges and spectral lines originating from neutral and weakly-ionized metals, which are unlikely to be optically thin, prevents the direct use of synthetic spectra for similar analysis.…”

Can Substorm Particle Acceleration Be Applied to Solar Flares?

“…However, the population that is initially outside of the loss cone becomes energized and escapes when the loss cone widens and might contribute to footpoint sources. The effective heating in the trap could also render it a possible mechanism for flares that show prolonged heating before the impulsive phase (e.g., Veronig et al 2002;Battaglia et al 2014) or for a long time during the post-flare phase (e.g., Kuhar et al 2017), which is apparently without a significant acceleration. It could also be a mechanism for flares that appear entirely thermal (e.g., Fleishman et al 2015).…”

Untitled

“…Íàêîïèâøåéñÿ â íàñòîÿùåå âðåìÿ ìàòåðèàë íàáëþäåíèé, ïîëó÷åííûé ïðè îáðàáîòêå äàííûõ îò ìèññèé «Hinode» (So lar B), SDO è IRIS, ïîçâîëÿåò ñäåëàòü íåñêîëüêî âàaeíûõ âûâîäîâ îòíîñèòåëüíî âñåõ âîçìîae íûõ ñöåíàðèåâ ðàçâèòèÿ âñïûøå÷íîãî ïðîöåññà â àòìîñôåðå àêòèâ íîé îáëàñòè è òåñíî ñâÿçàííîé ñ íèìè ïðîáëåìû íàãðåâà õðîìîñôåðû è êîðîíû Ñîëíöà [11,13,14,16,31,32,44,48,57]. Âî-ïåðâûõ, î÷åâèäíîé ñòàëà íåîáõîäèìîñòü âêëþ÷åíèÿ õðîìîñôåðû è ïåðå õîäíîé îáëàñòè â êà÷åñòâå âàaeíåéøåãî îòäåëüíîãî ýëåìåíòà â ýíåðãåòè -÷åñêóþ öåïî÷êó «ôîòîñôåðà -êîðîíà» [13,14].…”

“…Âî-âòîðûõ, öåëûé ðÿä íàáëþäåíèé, ïîëó÷åííûõ â âûøåóïîìÿíóòûõ ìèññèÿõ, ñòàâÿò â îòäåëüíûõ ñëó÷àÿõ ïîä ñîìíåíèå íàëè÷èå ÿâëåíèé, èãðàþùèõ îñíîâíóþ ðîëü â íàèáîëåå ïîïóëÿðíûõ ìîäåëÿõ äèíàìè -÷åñ êèõ ïðîöåññîâ â àòìîñôåðå àêòèâíîé îáëàñòè íàêàíóíå âñïûøêè è âî âðåìÿ åå ðàçâèòèÿ. Ñþäà ìîaeíî îòíåñòè îòñóòñòâèå âûñîêîýíåð -ãè÷ íûõ ÷àñòèö â íèaeíèé õðîìîñôåðå ïîñëå ôëýø-ôàçû âñïûøêè [16], ðàñïîëîaeåíèå îáëàñòè ïåðâè÷íîãî ýíåðãîâûäåëåíèÿ âñïûøêè íå â êîðî íàëüíîé îáëàñòè íàä ïåòëåé èëè àðêàäîé ïåòåëü [50], à â íèae íåñðåäíåé õðîìîñôåðå -âáëèçè èõ îñíîâàíèé [31,45,48,49], íåîáúÿñíèìî íèçêèå ñ òî÷êè çðåíèÿ èçâåñòíûõ òåîðèé òåìïåðàòóðû îòäåëüíûõ âñïûøåê [27,31,34]. Ïîäîáíûå ôàêòû òðåáóþò ñâîåãî îáúÿñ íåíèÿ èëè íà óðîâíå íîâîé òåîðèè, èëè íà óðîâíå îðèãèíàëüíîé êîíöåïöèè èññëåäîâàíèé.…”