Variation of Thermal Structure with Height of a Solar Active Region Derived from<i>SOHO</i>CDS and<i>YOHKOH</i>BCS Observations

Sterling, Alphonse C.; Pike, C. D.; Mason, H. E.; Watanabe, Tetsuya; Antiochos, S. K.

doi:10.1086/307820

Cited by 9 publications

(8 citation statements)

References 28 publications

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“…Then using this height (about 45 000 km) and I fg for SiXII, we computed the scale-height H for this line. It is considerably reduced compared to the quietSun value (about 42 000 km compared to 85 000 km), which is consistent with the findings of Sterling et al (1999). Now using this new H for SiXII, we were able to obtain a plaussible solution for heights h and h within the EUV filament extension.…”

Section: Mgx and Sixii Coronal Linessupporting

confidence: 88%

“…This is because the filament is located in an active region (see Aulanier & Schmieder 2002) where the scale-heights can be quite different from those of the quiet Sun. In such a case one can use the results of Sterling et al (1999) which show that in an active region, the MgIX scale-height is similar to the quiet-Sun scale-height of MgIX derived from Fludra et al (1999), but for hotter lines the emission is much more concentrated towards the limb. Therefore, we took in our analysis H for MgX from Fludra et al (1999) (about 30 000 km) and using f (h) we computed the height at which I fg can be obtained.…”

Section: Mgx and Sixii Coronal Linesmentioning

confidence: 99%

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On the nature of extended EUV filaments

Anzer

Heinzel

2003

A&A

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Abstract. This paper describes the properties of extended EUV filaments and the theoretical modelling of them. We summarise the general aspects of the depression of EUV-line emission and give an interpretation of recent filament observations in transition-region and coronal lines. The EUV filament was found to be located relatively high in the corona (at least 20 000 km above the solar surface) and this requires an MHD scenario alternative to the parasitic-polarity model of Aulanier & Schmieder (2002). Here we present a new idea for the support of cool gas in the magnetic arcade of a prominence which is capable of explaining both wide and vertically extended EUV filaments. Our mechanism is based upon the twisting of individual flux tubes, similar to the one which was suggested by Priest et al. (1989). Finally, the consequences of this new model are discussed.

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Section: Mgx and Sixii Coronal Linessupporting

confidence: 88%

Section: Mgx and Sixii Coronal Linesmentioning

confidence: 99%

On the nature of extended EUV filaments

Anzer

Heinzel

2003

A&A

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“…BCS however did not have any spatial resolution, and those studies inferred the height structure of the temperature by using the solar limb as an occulting edge for a single active region which rotated around the disk and behind the limb. Sterling et al (1999) verified BCS findings by measuring spectral-scans from the Coronal Diagnostic Spectrometer (CDS) on the SOHO, integrated over different heights of an active region. Others have also investigated the thermal structure of active regions with various instruments (e.g., Pye et al 1978;Schadee et al 1983;Watanabe et al 1995;Yoshida & Tsuneta 1996;Warren & Winebarger 2003).…”

Section: Introductionmentioning

confidence: 69%

“…Consistent with the previous studies (Gabriel & Jordan 1975;Vaiana 1976;Webb 1981;Mason et al 1999;Del Zanna & Mason 2003;Milligan et al 2005;Tripathi et al 2006), we have found the temperature of this active region to be highest in its core, log T ∼ 6.6, with lower temperatures at higher heights. Here in this analysis, we are able to go beyond the work of, e.g., Sterling (1997) and Sterling et al (1997Sterling et al ( , 1999, which was primarily based on non-spatially-resolved observations. For example, we have found that the hottest locations occur in concentrated regions inside the core of the active region.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Hinode extreme-ultraviolet imaging spectrometer observations of a limb active region

O’Dwyer¹,

Zanna²,

Mason³

et al. 2010

A&A

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Aims. We investigate the electron density and temperature structure of a limb active region. Methods. We have carried out a study of an active region close to the solar limb using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray telescope (XRT) on board Hinode. The electron density and temperature distributions of the coronal emission have been determined using emission line intensity ratios. Differential emission measure (DEM) analysis and the emission measure (EM) loci technique were used to examine the thermal structure of the emitting plasma as a function of distance from the limb. Results. The highest temperature and electron density values are found to be located in the core of the active region, with a peak electron number density value of 1.9 × 10 10 cm −3 measured using the Fe XII 186.887 Å to 192.394 Å line intensity ratio. The plasma along the line of sight in the active region was found to be multi-thermal at different distances from the limb. The EIS and XRT DEM analyses appear to be in agreement in the temperature interval from log T = 6.5−6.7. Conclusions. Our results provide new constraints for models of coronal heating in active regions.

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“…Imaging spectrometers, apart from allowing the study of spectrally pure images, also allow us to measure detailed plasma properties such as electron temperature, density, and bulk plasma motions. Several excellent examples of EUV and X-ray imaging and spectroscopy of active regions can be found in the following : Solar EUV Rocket Telescope and Spectrograph (SERTS) in Brosius et al (1996Brosius et al ( , 1997a, Y ohkoh in Sterling et al (1997Sterling et al ( , 1999, CDS in Fludra et al (1997) and , and T RACE in Schrijver et al (1999) and Aschwanden et al (1999Aschwanden et al ( , 2000aAschwanden et al ( , 2000b.…”

Section: Introductionmentioning

confidence: 99%

The Extreme‐Ultraviolet Structure and Properties of a Newly Emerged Active Region

Gallagher

Phillips

Lee

et al. 2001

ApJ

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The structure and properties of a newly emerged solar active region (NOAA Active Region 7985) are discussed using the Coronal Diagnostic Spectrometer (CDS) and the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. CDS obtained high-resolution EUV spectra in the 308È381 and 513È633 wavelength ranges, while EIT recorded full-disk EUV images in A A the He II (304 Fe IX/X (171 Fe XII (195 and Fe XV (284 bandpasses. Electron density mea-A ), A ), A ), A ) surements from Si IX, Si X, Fe XII, Fe XIII, and Fe XIV line ratios indicate that the region consists of a central high-density core with peak densities of the order of 1.2 ] 1010 cm~3, which decrease monotonically to D5.0 ] 108 cm~3 at the active region boundary. The derived electron densities also vary systematically with temperature. Electron pressures as a function of both active region position and temperature were estimated using the derived electron densities and ion formation temperatures, and the constant pressure assumption was found to be an unrealistic simpliÐcation. Indeed, the active region is found to have a high-pressure core (1.3 ] 1016 cm~3 K) that falls to 6.0 ] 1014 cm~3 K just outside the region. CDS line ratios from di †erent ionization stages of iron, speciÐcally Fe XVI (335.4and Fe XIV A ) (334.4 were used to diagnose plasma temperatures within the active region. Using this method, peak A ), temperatures of 2.1 ] 106 K were identiÐed. This is in good agreement with electron temperatures derived using EIT Ðlter ratios and the two-temperature model of Zhang et al. The high-temperature emission is conÐned to the active region core, while emission from cooler (1È1.6) ] 106 K lines originates in a system of loops visible in EIT 171 and 195 images. Finally, the three-dimensional geometry of the A active region is investigated using potential Ðeld extrapolations from a Kitt Peak magnetogram. The combination of EUV and magnetic Ðeld extrapolations extends the "" core-halo ÏÏ picture of active region structure to one in which the core is composed of a number of compact coronal loops that conÐne the hot, dense, high-pressure core plasma while the halo emission emerges from a system of cooler and more extended loops.

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Variation of Thermal Structure with Height of a Solar Active Region Derived fromSOHOCDS andYOHKOHBCS Observations

Cited by 9 publications

References 28 publications

On the nature of extended EUV filaments

On the nature of extended EUV filaments

Hinode extreme-ultraviolet imaging spectrometer observations of a limb active region

The Extreme‐Ultraviolet Structure and Properties of a Newly Emerged Active Region

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