PROPERTIES OF CHROMOSPHERIC EVAPORATION AND PLASMA DYNAMICS OF A SOLAR FLARE FROM<i>IRIS</i>OBSERVATIONS

Sadykov, Viacheslav; Domínguez, Santiago Vargas; Kosovichev, A. G.; Sharykin, I. N.; Struminsky, A. B.; Zimovets, I. V.

doi:10.1088/0004-637x/805/2/167

Cited by 48 publications

(72 citation statements)

References 36 publications

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“…The two lines were redshifted during that time period, and remained redshifted even after the impulsive phase, gradually decreasing in magnitude over timescales exceeding 20 minutes at some positions. Similar trends in Si IV and other cool lines were reported by other authors in larger flares seen with IRIS, e.g., Sadykov et al (2015), Brannon et al (2015), Polito et al (2016).…”

Section: Introductionsupporting

confidence: 90%

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

Reep

Warren

Crump

et al. 2016

ApJ

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Results from the Solar Maximum Mission showed a close connection between the hard X-ray (HXR) and transition region (TR) emission in solar flares. Analogously, the modern combination of RHESSI and IRIS data can inform the details of heating processes in ways that were never before possible. We study a small event that was observed with RHESSI, IRIS, SDO, and Hinode, allowing us to strongly constrain the heating and hydrodynamical properties of the flare, with detailed observations presented in a previous paper. Long duration redshifts of TR lines observed in this event, as well as many other events, are fundamentally incompatible with chromospheric condensation on a single loop. We combine RHESSI and IRIS data to measure the energy partition among the many magnetic strands that comprise the flare. Using that observationally determined energy partition, we show that a proper multithreaded model can reproduce these redshifts in magnitude, duration, and line intensity, while simultaneously being well constrained by the observed density, temperature, and emission measure. We comment on the implications for both RHESSI and IRIS observations of flares in general, namely that: (1) a single loop model is inconsistent with long duration redshifts, among other observables; (2) the average time between energization of strands is less than 10 s, which implies that for a HXR burst lasting 10 minutes, there were at least 60 strands within a single IRIS pixel located on the flare ribbon; (3) the majority of these strands were explosively heated with an energy distribution well described by a power law of slope »-1.6; (4) the multi-stranded model reproduces the observed line profiles, peak temperatures, differential emission measure distributions, and densities.

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Section: Introductionsupporting

confidence: 90%

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

Reep

Warren

Crump

et al. 2016

ApJ

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“…Recent results from the IRIS mission have also shown similar results but with strong down-flows seen in Fe XXI spatially coincident with the loop top -consistent with hot-retracting loops for example (Tian et al, 2014). Sadykov et al (2015) found evaporation flows in the Fe XXI ion in a flare. Polito et al (2015) found that after this blue-shifted plasma was observed, the Fe XXI intensity slowly moved from the footprints to the top of the flare loops.…”

Section: Evaporation In Flares -Is This Different In Eruptive and Nonsupporting

confidence: 57%

The Characteristics of Solar X-Class Flares and CMEs: A Paradigm for Stellar Superflares and Eruptions?

et al. 2016

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This paper explores the characteristics of 42 solar X-class flares that were observed between February 2011 and November 2014, with data from the Solar Dynamics Observatory (SDO) and other sources. This flare list includes nine X-class flares that had no associated CMEs. In particular our aim was to determine whether a clear signature could be identified to differentiate powerful flares that have coronal mass ejections (CMEs) from those that do not. Part of the motivation for this study is the characterization of the solar paradigm for flare/CME occurrence as a possible guide to the stellar observations; hence we emphasize spectroscopic signatures. To do this we ask the following questions: Do all eruptive flares have long durations? Do CME-related flares stand out in terms of active-region size vs. flare duration? Do flare magnitudes correlate with sunspot areas, and, if so, are eruptive events distinguished? Is the occurrence of CMEs related to the fraction of the activeregion area involved? Do X-class flares with no eruptions have weaker non-thermal signatures? Is the temperature dependence of evaporation different in eruptive and non-eruptive flares? Is EUV dimming only seen in eruptive flares? We find only one feature consistently associated with CME-related flares specifically: coronal dimming in lines characteristic of the quiet-Sun corona, i.e. 1 -2 MK. We do not find a correlation between flare magnitude and sunspot areas. Although challenging, it will be of importance to model dimming for stellar cases and make suitable future plans for observations in the appropriate wavelength range in order to identify stellar CMEs consistently.

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“…Perhaps the most significant challenge presented by these data is the persistent redshifts observed in Si IV and C II. Persistent redshifts have been observed with IRIS for a number of events and are not an idiosyncrasy of the data that we have analyzed (see Brannon et al 2015;Brosius & Daw 2015;Sadykov et al 2015;Polito et al 2016).…”

Section: Summary and Discussionmentioning

confidence: 68%

Transition Region and Chromospheric Signatures of Impulsive Heating Events. I. Observations

Warren

Reep

Crump

et al. 2016

ApJ

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We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (EIS) allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event, the intensities in each pixel for the Si IV 1402.770 Å, C II 1334.535 Å, Mg II 2796.354 Å, and O I 1355.598 Å emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si IV, C II, and Mg II during the impulsive phase. Mg II shows redshifts during the bursts and stationary emission at other times. The Si IV and C II profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates.

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PROPERTIES OF CHROMOSPHERIC EVAPORATION AND PLASMA DYNAMICS OF A SOLAR FLARE FROMIRISOBSERVATIONS

Cited by 48 publications

References 36 publications

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

The Characteristics of Solar X-Class Flares and CMEs: A Paradigm for Stellar Superflares and Eruptions?

Transition Region and Chromospheric Signatures of Impulsive Heating Events. I. Observations

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