Hot Topic, Warm Loops, Cooling Plasma? Multithermal Analysis of Active Region Loops

Schmelz, J. T.; Pathak, S.; Brooks, David H.; Christian, G. M.; Dhaliwal, Vira

doi:10.1088/0004-637x/795/2/171

Cited by 19 publications

(19 citation statements)

References 35 publications

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“…Figure 4B shows that active region DEMs are peaked at a temperature somewhat higher than that of the quiet corona and that the peak is very broad, with emission extending to high temperatures. These profiles, which are averaged over all active regions present in a given time bin, show general agreement with previously published DEM profiles integrated over whole active regions ( 4 , 31 , 32 ). The predominant active region temperature is around 1.8 MK, with hot cores at a temperature closer to 3 MK.…”

Section: Resultssupporting

confidence: 89%

Global conditions in the solar corona from 2010 to 2017

Morgan

Taroyan

2017

Sci. Adv.

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Section: Resultssupporting

confidence: 89%

Global conditions in the solar corona from 2010 to 2017

Morgan

Taroyan

2017

Sci. Adv.

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“…arxiv we analysed are either cool loop structures or loop footpoints, which are often observed to be dominated by plasma with a very narrow thermal distribution (e.g. Del Zanna 2003; Warren et al 2008;Schmelz et al 2007Schmelz et al , 2014. We also emphasize that we are estimating average values of temperature and density for the emitting plasma.…”

Section: Discussion and Summarymentioning

confidence: 99%

Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS

Polito

Zanna

Dudík

et al. 2016

A&A

100

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The intensity of the O iv 2s 2 2p 2 P-2s2p 2 4 P and S iv 3 s 2 3p 2 P-3s 3p 2 4 P intercombination lines around 1400 Å observed with the Interface Region Imaging Spectrograph (IRIS) provide a useful tool to diagnose the electron number density (N e ) in the solar transition region plasma. We measure the electron number density in a variety of solar features observed by IRIS, including an active region (AR) loop, plage and brightening, and the ribbon of the 22-June-2015 M 6.5 class flare. By using the emissivity ratios of O iv and S iv lines, we find that our observations are consistent with the emitting plasma being near isothermal (logT [K] ≈ 5) and iso-density (N e ≈ 10 10.6 cm −3 ) in the AR loop. Moreover, high electron number densities (N e ≈ 10 13 cm −3 ) are obtained during the impulsive phase of the flare by using the S iv line ratio. We note that the S iv lines provide a higher range of density sensitivity than the O iv lines. Finally, we investigate the effects of high densities (N e 10 11 cm −3 ) on the ionization balance. In particular, the fractional ion abundances are found to be shifted towards lower temperatures for high densities compared to the low density case. We also explored the effects of a non-Maxwellian electron distribution on our diagnostic method.

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“…We also compare our models to Model G (using the Bayes factor K iG ) Observations of hot coronal loops reveal them to be multithermal (e.g. Schmelz et al 2010Schmelz et al , 2014Nisticò et al 2014). However, Aschwanden & Nightingale (2005) found the majority of cooler loops to be well-approximated as isothermal, and Warren et al (2008) found isolated loops typically have very narrow temperature variation across the loop.…”

Section: Methodsmentioning

confidence: 99%

Coronal loop density profile estimated by forward modelling of EUV intensity

Pascoe

Goddard

Anfinogentov

et al. 2017

A&A

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Aims. The transverse density structuring of coronal loops was recently calculated for the first time using the general damping profile for kink oscillations. This seismological method assumes a density profile with a linear transition region. We consider to what extent this density profile accounts for the observed intensity profile of the loop, and how the transverse intensity profile may be used to complement the seismological technique. Methods. We use isothermal and optically transparent approximations for which the intensity of extreme ultraviolet (EUV) emission is proportional to the square of the plasma density integrated along the line of sight. We consider four different models for the transverse density profile; the generalised Epstein profile, the step function, the linear transition region profile, and a Gaussian profile. The effect of the point spread function is included and Bayesian analysis is used for comparison of the models. Results. The two profiles with finite transitions are found to be preferable to the step function profile, which supports the interpretation of kink mode damping as being due to mode coupling. The estimate of the transition layer width using forward modelling is consistent with the seismological estimate. Conclusions. For wide loops, that is those observed with sufficiently high spatial resolution, this method can provide an independent estimate of density profile parameters for comparison with seismological estimates. In the ill-posed case of only one of the Gaussian or exponential damping regimes being observed, it may provide additional information to allow a seismological inversion to be performed. Alternatively, it may be used to obtain structuring information for loops that do not oscillate.

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Hot Topic, Warm Loops, Cooling Plasma? Multithermal Analysis of Active Region Loops

Cited by 19 publications

References 35 publications

Global conditions in the solar corona from 2010 to 2017

Global conditions in the solar corona from 2010 to 2017

Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS

Coronal loop density profile estimated by forward modelling of EUV intensity

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