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Mason, H. E.; Landi, E.; Pike, C. D.; Young, Peter R.

doi:10.1023/a:1005246220208

Cited by 29 publications

(27 citation statements)

References 19 publications

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“…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.…”

Section: Conclusion and Discussionsupporting

confidence: 92%

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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Section: Conclusion and Discussionsupporting

confidence: 92%

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

O’Dwyer¹,

Zanna²,

Mason³

et al. 2010

A&A

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“…Observations of active regions with the Coronal Diagnostic Spectrometer on SOHO suggest that the hottest temperatures and highest densities are typically found in the core of an active region (e.g., Mason et al 1999;Gallagher et al 2001). For these observations, the SUMER slit was positioned above the core, in the "halo" of cooler, more tenuous loops that typically surround an active region.…”

Section: Summary and Discussionmentioning

confidence: 99%

Density and Temperature Measurements in a Solar Active Region

Warren

Winebarger

2003

ApJ

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We present electron density and temperature measurements from an active region observed above the limb with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory. Density-sensitive line ratios from Si viii and S x indicate densities greater than 10 8 cm as high Ϫ3as 200Љ (or 145 Mm) above the limb. At these heights, static, uniformly heated loop models predict densities close to 10 7 cm . Differential emission measure analysis shows that the observed plasma is nearly isothermal Ϫ3with a mean temperature of about 1.5 MK and a dispersion of about 0.2 MK. Both the differential emission measure and the Si xi/Si viii line ratios indicate only small variations in the temperature at the heights observed. These measurements confirm recent observations from the Transition Region and Coronal Explorer of "overdense" plasma at temperatures near 1 MK in solar active regions. Time-dependent hydrodynamic simulations suggest that impulsive heating models can account for the large densities, but they have a difficult time reproducing the narrow range of observed temperatures. The observations of overdense, nearly isothermal plasma in the solar corona provide a significant challenge to theories of coronal heating.

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“…The accuracy of determination of the densities depends upon the specific method applied and is about 50% (e.g. Mason et al 1999 and references therein). The determination of the density ratio possibly has even larger error, but as the ratio ρ e /ρ 0 is assumed to be small, one can neglect its value in Eq.…”

Section: Error Analysismentioning

confidence: 99%

Determination of the coronal magnetic field by coronal loop oscillations

Nakariakov

Ofman²

2001

A&A

485

444

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Abstract. We develop a new method for the determination of the absolute value of the magnetic field strength in coronal closed magnetic structures, based on the analysis of flare-generated oscillations of coronal loops. Interpretation of the oscillations observed in terms of global standing kink waves allows to connect the period of the oscillations and the loops length with the magnetic field strength in the loops. For loop oscillations observed with TRACE on 14th July 1998 and 4th July 1999, we estimate the magnetic field strength as 4-30 G. Using TRACE 171Å and 195Å images of the loop, taken on 4th July 1999 to determine the plasma density, we estimate the magnetic field in the loop as 13 ± 9 G. Improved diagnostic of the loop length, the oscillation period, and the plasma density in the loop will significantly improve the method's precision.

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Untitled

Cited by 29 publications

References 19 publications

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

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

Density and Temperature Measurements in a Solar Active Region

Determination of the coronal magnetic field by coronal loop oscillations

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