Imaging and Spectroscopic Observations of Magnetic Reconnection and Chromospheric Evaporation in a Solar Flare

Tian, Hui; Li, Gang; Reeves, Katharine K.; Raymond, J. C.; Guo, Fan; Liu, W.; Bin, Chen; Murphy, N. A.

doi:10.1088/2041-8205/797/2/l14

Cited by 142 publications

(141 citation statements)

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“…It was hypothesized that this was due to a downward shock produced during the reconnection process. 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.…”

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

confidence: 58%

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

confidence: 58%

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

et al. 2016

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“…The strong redshifts (∼100 km s −1 ), observed during the pre-flare phase, were most likely associated with the downflows associated with the reconnection driving the untwisting jets. Recently, Tian et al (2014) also reported strong redshifts (∼125 km s −1 ) using the IRIS data and interpreted them as being a reconnectiongenerated downflow/hot retracting loops. It is likely that slow reconnection starts (20:50 UT onwards) during the pre-flare heating phase, generating small untwisting jets, which probably follow the inner spine of the fan loops.…”

Section: Summary and Discussionmentioning

confidence: 93%

FORMATION AND ERUPTION OF A SMALL FLUX ROPE IN THE CHROMOSPHERE OBSERVED BY NST,IRIS, ANDSDO

Kumar

Yurchyshyn

Wang

et al. 2015

ApJ

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Using high-resolution images from the 1.6 m New Solar Telescope at Big Bear Solar Observatory, we report the direct evidence of chromospheric reconnection at the polarity inversion line between two small opposite polarity sunspots. Small jetlike structures (with velocities of ∼20-55 km s ) were observed at the reconnection site before the onset of the first M1.0 flare. The slow rise of untwisting jets was followed by the onset of cool plasma inflow (∼10 km s −1 ) at the reconnection site, causing the onset of a two-ribbon flare. The reconnection between two sheared J-shaped cool Hα loops causes the formation of a small twisted (S-shaped) flux rope in the chromosphere. In addition, Helioseismic and Magnetic Imager magnetograms show the flux cancellation (both positive and negative) during the first M1.0 flare. The emergence of negative flux and the cancellation of positive flux (with shear flows) continue until the successful eruption of the flux rope. The newly formed chromospheric flux rope becomes unstable and rises slowly with a speed of ∼108 km s −1 during a second C8.5 flare that occurred after ∼3 hr of the first M1.0 flare. The flux rope was destroyed by repeated magnetic reconnection induced by its interaction with the ambient field (fan-spine topology) and looks like an untwisting surge (∼170 km s −1 ) in the coronal images recorded by the Solar Dynamics Observatory/Atmospheric Imaging Assembly. These observations suggest the formation of a chromospheric flux rope (by magnetic reconnection associated with flux cancellation) during the first M1.0 flare and its subsequent eruption/disruption during the second C8.5 flare.

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“…There are still many areas of this work that can be improved to remove assumptions and generalize the model, however, such as determining how the electron beam parameters vary from thread to thread or finding an upper limit to the number of threads. It is also often true that Si IV has a stronger stationary component in other flares than was seen in this one (e.g., Tian et al 2014), so that further work may be required to determine whence the difference arises.…”

Section: Implications and Conclusionmentioning

confidence: 94%

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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Imaging and Spectroscopic Observations of Magnetic Reconnection and Chromospheric Evaporation in a Solar Flare

Cited by 142 publications

References 50 publications

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

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

FORMATION AND ERUPTION OF A SMALL FLUX ROPE IN THE CHROMOSPHERE OBSERVED BY NST,IRIS, ANDSDO

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

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