A Reconnection-Driven Model of the Hard X-Ray Loop-Top Source From Flare 2004 February 26

Longcope, D. W.; Qiu, Jiong; Brewer, Jasmine

doi:10.3847/1538-4357/833/2/211

Cited by 19 publications

(17 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A coronal origin, from thermal 30-50 MK gas, may also be possible but generating the requisite gas density is challenging. For example, Caspi & Lin (2010) also found two components of X-ray continuum emission in an energetic (X4.8) solar flare: a superhot (T e > 30 MK) component, likely due to direct coronal heating and compression during the magnetic reconnection process (Longcope & Guidoni 2011;Longcope et al 2016), and a hot (T e 25 MK) component that they attributed to chromospheric evaporation. However, an extension of their model spectra to the FUV predicts F 1142 = 5 × 10 −17 erg cm −2 s −1 Å−1 , a factor of ∼20 below the observed FUV flux.…”

Section: Discussionmentioning

confidence: 98%

A Hot Ultraviolet Flare on the M Dwarf Star GJ 674

Froning

Kowalski

France

et al. 2019

ApJL

View full text Add to dashboard Cite

As part of the Mega-MUSCLES Hubble Space Telescope (HST) Treasury program, we obtained timeseries ultraviolet spectroscopy of the M2.5V star, GJ 674. During the FUV monitoring observations, the target exhibited several small flares and one large flare (E F U V = 10 30.75 ergs) that persisted over the entirety of a HST orbit and had an equivalent duration > 30, 000 sec, comparable to the highest relative amplitude event previously recorded in the FUV. The flare spectrum exhibited enhanced line emission from chromospheric, transition region, and coronal transitions and a blue FUV continuum with an unprecedented color temperature of T c 40, 000 ± 10, 000 K. In this paper, we compare the flare FUV continuum emission with parameterizations of radiative hydrodynamic model atmospheres of M star flares. We find that the observed flare continuum can be reproduced using flare models but only with the ad hoc addition of hot, dense emitting component. This observation demonstrates that flares with hot FUV continuum temperatures and significant EUV/FUV energy deposition will continue to be of importance to exoplanet atmospheric chemistry and heating even as the host M dwarfs age beyond their most active evolutionary phases.

show abstract

Section: Discussionmentioning

confidence: 98%

A Hot Ultraviolet Flare on the M Dwarf Star GJ 674

Froning

Kowalski

France

et al. 2019

ApJL

View full text Add to dashboard Cite

show abstract

“…Direct in situ heating of plasma at loop tops has been suggested as necessary to explain certain flare observations (e.g. Battaglia et al 2009 suggest that energy release from reconnection (Cheung et al 2019) and retraction of flare loops (Longcope & Klimchuk 2015;Longcope et al 2016Longcope et al , 2018 can deposit energy at the loop tops. This energy would then be transported to the lower atmosphere via the conductive flux.…”

Section: Flares Driven By Thermal Conductionmentioning

confidence: 99%

He I 10830 Å Dimming During Solar Flares, I. The Crucial Role of Non-Thermal Collisional Ionisations

Kerr,

Xu,

Allred

et al. 2021

Preprint

View full text Add to dashboard Cite

While solar flares are predominantly characterised by an intense broadband enhancement to the solar radiative output, certain spectral lines and continua will, in theory, exhibit flare-induced dimmings. Observations of transitions of orthohelium He i λλ10830 Å and the He i D3 lines have shown evidence of such dimming, usually followed by enhanced emission. It has been suggested that non-thermal collisional ionisation of helium by an electron beam, followed by recombinations to orthohelium, is responsible for overpopulating the those levels, leading to stronger absorption. However it has not been possible observationally to preclude the possibility of overpopulating orthohelium via enhanced photoionisation of He i by EUV irradiance from the flaring corona followed by recombinations. Here we present radiation hydrodynamics simulations of non-thermal electron beam-driven flares where (1) both non-thermal collisional ionisation of Helium and coronal irradiance are included, and (2) only coronal irradiance is included. A grid of simulations covering a range of total energies deposited by the electron beam, and a range of non-thermal electron beam low-energy cutoff values, were simulated. In order to obtain flare-induced dimming of the He i 10830 Å line it was necessary for non-thermal collisional ionisations to be present. The effect was more prominent in flares with larger low-energy cutoff values and longer lived in weaker flares and flares with a more gradual energy deposition timescale. These results demonstrate the usefulness of orthohelium line emission as a diagnostic of flare energy transport.

show abstract

“…Thermal conduction occurs strictly along the field line and drives evaporation from a chromosphere orders of magnitude denser and cooler than the corona. These aspects of the post-reconnection dynamics are essential in making comparisons to flare observations, which are often dominated by evaporated plasma (Longcope et al 2016). Most significantly, under the TFT model, the flaring loop is energized by the magnetic energy released by retraction of the postreconnection flux tube.…”

Section: Transient Patchy Reconnection In Three Dimensionsmentioning

confidence: 99%

Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Longcope

Unverferth

Klein

et al. 2018

ApJ

Self Cite

View full text Add to dashboard Cite

Current sheets are believed to form in the wakes of erupting flux ropes and to enable the magnetic reconnection responsible for an associated flare. Multiwavelength observations of an eruption on 2017 September 10 show a long, linear feature widely taken as evidence of a current sheet viewed edge-on. The relation between the hightemperature, high-density plasma thus observed and any current sheet is not yet entirely clear. We estimate the magnetic field strength surrounding the sheet and conclude that approximately one-third of all flux in the active region was opened by the eruption. Subsequently decreasing field strength suggests that the open flux closed down over the next several hours through reconnection at a rate F 5 10 17 Mx s −1. We find in AIA observations evidence of downward-moving, dark structures analogous to either supra-arcade downflows, more typically observed above flare arcades viewed face-on, or supra-arcade downflowing loops, previously reported in flares viewed in this perspective. These features suggest that the plasma sheet is composed of the magnetic flux retracting after being reconnected high above the arcade. We model flux tube retraction following reconnection to show that this process can generate high densities and temperatures as observed in the plasma sheet. The retracting flux tubes reach their highest temperatures at the end of their retraction, well below the site of reconnection, consistent with previous analysis of AIA and EIS data showing a peak in the plasma temperature near the base of this particular sheet.

show abstract

A Reconnection-Driven Model of the Hard X-Ray Loop-Top Source From Flare 2004 February 26

Cited by 19 publications

References 54 publications

A Hot Ultraviolet Flare on the M Dwarf Star GJ 674

A Hot Ultraviolet Flare on the M Dwarf Star GJ 674

He I 10830 Å Dimming During Solar Flares, I. The Crucial Role of Non-Thermal Collisional Ionisations

Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection

Contact Info

Product

Resources

About