Active Region Loops: Temperature Measurements as a Function of Time from JointTRACEandSOHOCDS Observations

Cirtain, Jonathan; Zanna, G. Del; DeLuca, E. E.; Mason, H. E.; Martens, Petrus C.; Schmelz, J. T.

doi:10.1086/509769

Cited by 38 publications

(31 citation statements)

References 23 publications

(31 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our SOHO CDS observations showed that the majority of the observed warm loops are long-lasting, i.e. do not appear to cool down or heat up significantly over timescales of hours Cirtain et al 2007). Our results are in contrast to those obtained by Warren et al (2003); Ugarte-Urra et al (2006Viall & Klimchuk (2011), although they do not necessarily imply steady heating for the single structures.…”

Section: )mentioning

confidence: 76%

See 1 more Smart Citation

The multi-thermal emission in solar active regions

Zanna¹

2013

A&A

Self Cite

155

110

View full text Add to dashboard Cite

We present simultaneous SDO AIA and Hinode EIS observations of the hot cores of active regions (ARs) and assess the dominant contributions to the AIA EUV bands. This is an extension of our previous work. We find good agreement between SDO AIA, EVE and EIS observations, using our new EIS calibration and the latest EVE v.3 data. We find that all the AIA bands are multi-thermal, with the exception of the 171 and 335 Å, and provide ways to roughly estimate the main contributions directly from the AIA data. We present and discuss new atomic data for the AIA bands, showing that they are now sufficiently complete to obtain temperature information in the cores of ARs, with the exception of the 211 Å band. We found that the newly identified Fe xiv 93.61 Å line is the dominant contribution to the 94 Å band, whenever Fe xviii is not present. Three methods to estimate the Fe xviii emission in this band are presented, two using EIS and one directly from the AIA data. Fe xviii emission is often present in the cores of ARs, but we found cases where it is formed at 3 MK and not 7 MK, the temperature of peak ion abundance in equilibrium. The best EIS lines for elemental abundance determination and differential emission measure (DEM) analysis are discussed. A new set of abundances for many elements are obtained from EIS observations of hot 3 MK loops. The abundances of the elements with low first ionisation potential (FIP), relative to those of the high-FIP elements, are found to be enhanced by about a factor of three, compared to the photospheric values. A measurement of the path length implies that the absolute abundances of the low-FIP elements are higher than the photospheric values by at least a factor of three. We present a new DEM method customised for the AIA bands, to study the thermal structure of ARs at 1 resolution. This was tested on a few ARs, including one observed during the Hi-C rocket flight. We found excellent agreement between predicted and observed AIA count rates and EIS radiances. Overall we found few differences between the AIA and Hi-C 193 Å images of coronal structures, despite the higher Hi-C resolution (0.25 ). The Hi-C images and the AIA DEM modelling suggest that some of the cooler loops (below 1 MK) are already resolved by AIA, while the hotter (1.5-2.5 MK) "background" emission is in most places still unresolved even at the Hi-C resolution. This unresolved emission is significantly lower than previously observed with TRACE, the SOHO CDS, and Hinode EIS spectrometers. Its enhancement appears to be mostly due to increased iron abundance. We find an ubiquitous presence of emission at different temperatures that is not co-spatial, and suggest that future high-resolution imaging is carried out with isothermal bands.

show abstract

Section: )mentioning

confidence: 76%

“…Most warm loops were found to be nearly isothermal in their cross-section, with filling factors close to one at their base (Del Zanna 2003a;Cirtain et al 2007). Our results have so far been largely confirmed by Hinode EIS and SDO AIA observations.…”

Section: Introductionmentioning

confidence: 96%

The multi-thermal emission in solar active regions

Zanna¹

2013

A&A

Self Cite

155

110

View full text Add to dashboard Cite

show abstract

“…In the least, contamination from diffuse background and/or foreground emission is present, or the plasma is multithermal (e.g., Schmelz et al 2005;Schmelz & Martens 2006;Cirtain et al 2007;Schmelz et al 2007aSchmelz et al , 2008Aschwanden et al 2008;Schmelz et al 2009a;Terzo & Reale 2010;O'Dwyer et al 2010), or there is a contribution from low-intensity high-temperature component (e.g. Reale et al 2009a,b;Schmelz et al 2009b,c).…”

Section: Temperature Diagnostic Using Cifrmentioning

confidence: 99%

Is it possible to model observed active region coronal emission simultaneously in EUV and X-ray filters?

Dudík

Dzifčáková

Karlický

et al. 2011

A&A

View full text Add to dashboard Cite

Aims. We investigate the possibility of modeling the active region coronal emission in the EUV and X-ray filters using one, universal, steady heating function, tied to the properties of the magnetic field. Methods. We employ a simple, static model to compute the temperature and density distributions in the active region corona. The model allows us to explore a wide range of parameters of the heating function. The predicted EUV and X-ray emission in the filters of EIT/SOHO and XRT/Hinode are calculated and compared with observations. Using the combined improved filter-ratio (CIFR) method, a temperature diagnostic is employed to compare the modeled temperature structure of the active region with the temperature structure derived from the observations. Results. The global properties of the observations are most closely matched for heating functions scaling as B 0.7−0.8 0 /L 0.5 0 that depend on the spatially variable heating scale-length. The modeled X-ray emission originates from locations where large heating scale-lengths are found. However, the majority of the loops observed in the 171 and 195 filters can be modeled only by loops with very short heating scale-lengths. These loops are known to be thermally unstable. We are unable to find a model that both matches the observations in all EUV and X-ray filters, and contains only stable loops. As a result, although our model with a steady heating function can explain some of the emission properties of the 171 and 195 loops, it cannot explain their observed lifetimes. Thus, the model does not lead to a self-consistent solution. The performance of the CIFR method is evaluated and we find that the diagnosed temperature can be approximated with a geometric mean of the emission-measure weighted and maximum temperature along the line of sight. Conclusions. We conclude that if one universal heating function exists, it should be at least partially time-dependent.

show abstract

“…Therefore, in this approach it is more adequate to use many filters or lines in terms of differential emission measure distributions DEM(T )/dT (Pottash et al, 1964;Sylwester et al, 1980). Extended discussion of the DEM versus isothermal approximation can by found, for example, in Schmelz et al (2001), Cirtain et al (2007) and references therein.…”

Section: Introductionmentioning

confidence: 99%

Diagnostic of the temperature and differential emission measure (DEM) based on Hinode/XRT data

Siarkowski

Falewicz

Kȩpa³

et al. 2008

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. We discuss here various methodologies and an optimal strategy of the temperature and emission measure diagnostics based on Hinode X-Ray Telescope data. As an example of our results we present the determination of the temperature distribution of the X-rays emitting plasma using a filters ratio method and three various methods of the calculation of the differential emission measure (DEM). We have found that all these methods give results similar to the two filters ratio method. Additionally, all methods of the DEM calculation gave similar solutions. We can state that the majority of the pairs of the Hinode filters allows one to derive the temperature and emission measure in the isothermal plasma approximation using standard diagnostics based on the two filters ratio method. In cases of strong flares one can also expect good conformity of the results obtained using a Withbroe -Sylwester, genetic algorithm and least-squares methods of the DEM evaluation.

show abstract

Active Region Loops: Temperature Measurements as a Function of Time from JointTRACEandSOHOCDS Observations

Cited by 38 publications

References 23 publications

The multi-thermal emission in solar active regions

The multi-thermal emission in solar active regions

Is it possible to model observed active region coronal emission simultaneously in EUV and X-ray filters?

Diagnostic of the temperature and differential emission measure (DEM) based on <I>Hinode</I>/XRT data

Contact Info

Product

Resources

About

Active Region Loops: Temperature Measurements as a Function of Time from JointTRACEandSOHOCDS Observations

Cited by 38 publications

References 23 publications

The multi-thermal emission in solar active regions

The multi-thermal emission in solar active regions

Is it possible to model observed active region coronal emission simultaneously in EUV and X-ray filters?

Diagnostic of the temperature and differential emission measure (DEM) based on &lt;I&gt;Hinode&lt;/I&gt;/XRT data

Contact Info

Product

Resources

About

Diagnostic of the temperature and differential emission measure (DEM) based on <I>Hinode</I>/XRT data