Temperature diagnostics with multichannel imaging telescopes

Weber, Mark; DeLuca, E. E.; Golub, L.; Sette, A

doi:10.1017/s1743921304006088

Cited by 57 publications

(35 citation statements)

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“…In fact, different spectrometers working at different wavelength ranges may still observe lines from the same element, so that they will be sampling the same temperature interval regardless of their passband. Thus, our results will be of more general use than Golub et al (2004) and Weber et al (2004).…”

Section: Introductionsupporting

confidence: 64%

“…Similar studies with different goals were recently carried out in preparation for the SDO and Hinode missions by Golub et al (2004) and Weber et al (2004). Both studies were focused on determining how well, and with what uncertainties, could a DEM curve known a priori be reconstructed using data from the limited number of broad-band filter intensities provided by Hinode/XRT and narrow-band filters in SDO/AIA.…”

Section: Introductionmentioning

confidence: 76%

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Monte Carlo Markov chain DEM reconstruction of isothermal plasmas

Landi

Reale

Testa

2012

A&A

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Context. Recent studies carried out with SOHO and Hinode high-resolution spectrometers have shown that the plasma in the off-disk solar corona is close to isothermal. If confirmed, these findings may have significant consequences for theoretical models of coronal heating. However, these studies have been carried out with diagnostic techniques whose ability to reconstruct the plasma distribution with temperature has not been thoroughly tested. Aims. In this paper, we carry out tests on the Monte Carlo Markov chain (MCMC) technique with the aim of determining: 1) its ability to retrieve isothermal plasmas from a set of spectral line intensities, with and without random noise; 2) to what extent can it discriminate between an isothermal solution and a narrow multithermal distribution; and 3) how well it can detect multiple isothermal components along the line of sight. We also test the effects of 4) atomic data uncertainties on the results, and 5) the number of ions whose lines are available for the DEM reconstruction. Methods. We first use the CHIANTI database to calculate synthetic spectra from different thermal distributions: single isothermal plasmas, multithermal plasmas made of multiple isothermal components, and multithermal plasmas with a Gaussian DEM distribution with variable width. We then apply the MCMC technique on each of these synthetic spectra, so that the ability of the MCMC technique at reconstructing the original thermal distribution can be evaluated. Next, we add a random noise to the synthetic spectra, and repeat the exercise, in order to determine the effects of random errors on the results. We also we repeat the exercise using a different set of atomic data from those used to calculate synthetic line intensities, to understand the robustness of the results against atomic physics uncertainties. The size of the temperature bin of the MCMC reconstruction is varied in all cases, in order to determine the optimal width. Results. We find that the MCMC technique is unable to retrieve isothermal plasmas to better than Δ log T 0.05. Also, the DEM curves obtained using lines calculated with an isothermal plasma and with a Gaussian distribution with FWHM of log T 0.05 are very similar. Two near-isothermal components can be resolved if their temperature separation is Δ log T = 0.2 or larger. Thus, DEM diagnostics has an intrinsic resolving power of log T = 0.05. Atomic data uncertainties may significantly affect both temperature and peak DEM values, but do not alter our conclusions. The availability of small sets of lines also does not worsen the performance of the MCMC technique, provided these lines are formed in a wide temperature range. Conclusions. Our analysis shows the present limitations in our ability to identify the presence of strictly isothermal plasmas in stellar and solar coronal spectra.

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Section: Introductionsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 76%

Monte Carlo Markov chain DEM reconstruction of isothermal plasmas

Landi

Reale

Testa

2012

A&A

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“…The older χ 2 minimization program has been replaced with a more robust χ 2 minimization program written by M. Weber for the inversion of the Hinode XRT data (see, e.g. Weber et al 2004), part of the Solarsoft program XRT_DEM_ITERATIVE2.…”

Section: Dem Inversion Softwarementioning

confidence: 99%

CHIANTI – An atomic database for emission lines. Version 8

Zanna

Dere

Young

et al. 2015

A&A

441

407

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We present version 8 of the CHIANTI database. This version includes a large amount of new data and ions, which represent a significant improvement in the soft X-ray, extreme UV (EUV) and UV spectral regions, which several space missions currently cover. New data for neutrals and low charge states are also added. The data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for most of the new datasets are not spline-fitted as previously, but are retained as calculated. This required a change of the format of the CHIANTI electron excitation files. The format of the energy files has also been changed. Excitation rates between all the levels are retained for most of the new datasets, so the data can in principle be used to model highdensity plasma. In addition, the method for computing the differential emission measure used in the CHIANTI software has been changed.

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“…Aschwanden & Boerner 2011) or splines (e.g. Weber et al 2004), the latter used for this CME event by Cheng et al (2012). Again, if the assumption about the form of the DEM is wrong, then the results are difficult to interpret reliably.…”

Section: Introductionmentioning

confidence: 98%

Multi-thermal dynamics and energetics of a coronal mass ejection in the low solar atmosphere

Hannah

Kontar

2013

A&A

104

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Aims. The aim of this work is to determine the multi-thermal characteristics and plasma energetics of an eruptive plasmoid and occulted flare observed by the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA). Methods. We study a 2010 Nov. 3 event (peaking at 12:20 UT in GOES soft X-rays) of a coronal mass ejection and occulted flare that demonstrates the morphology of a classic erupting flux rope. The high spatial and time resolution and six coronal channels of the SDO/AIA images allows the dynamics of the multi-thermal emission during the initial phases of eruption to be studied in detail. The differential emission measure is calculated, using an optimized version of a regularized inversion method, for each pixel across the six channels at different times, resulting in emission measure maps and movies in a variety of temperature ranges. Results. We find that the core of the erupting plasmoid is hot (8-11, 11-14 MK) with a similarly hot filamentary "stem" structure connecting it to the lower atmosphere, which could be interpreted as the current sheet in the flux rope model, though is wider than these models suggest. The velocity of the leading edge of the eruption is 597-664 km s −1 in the temperature range ≥3-4 MK and between 1029-1246 km s −1 for ≤2-3 MK. We estimate the density (in 11-14 MK) of the erupting core and stem during the impulsive phase to be about 3 × 10 9 cm −3 , 6 × 10 9 cm −3 , 9 × 10 8 cm −3 in the plasmoid core, stem, and surrounding envelope of material. This gives thermal energy estimates of 5 × 10 29 erg, 1 × 10 29 erg, and 2 × 10 30 erg. The kinetic energy for the core and envelope is slightly lower. The thermal energy of the core and current sheet grows during the eruption, suggesting continuous influx of energy presumably via reconnection. Conclusions. The combination of the optimized regularized inversion method and SDO/AIA data allows the multi-thermal characteristics (i.e. velocity, density, and thermal energies) of the plasmoid eruption to be determined.

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Temperature diagnostics with multichannel imaging telescopes

Cited by 57 publications

References 0 publications

Monte Carlo Markov chain DEM reconstruction of isothermal plasmas

Monte Carlo Markov chain DEM reconstruction of isothermal plasmas

CHIANTI – An atomic database for emission lines. Version 8

Multi-thermal dynamics and energetics of a coronal mass ejection in the low solar atmosphere

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