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

O’Dwyer, B.; Zanna, G. Del; Mason, H. E.; Sterling, Alphonse C.; Tripathi, Durgesh; Young, Peter R.

doi:10.1051/0004-6361/200912701

Cited by 39 publications

(36 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These were obtained by summing the rest and blue-shifted components. The average values in the active region are about 10 9.5 cm −3 , which is typical of an active region (O'Dwyer et al 2010). However, the ribbon structure becomes denser during the small flare, with values in the range 1-3 × 10 10 cm −3 .…”

Section: Flare Kernels: Source Regions Of Chromospheric Evaporationmentioning

confidence: 89%

The 22 May 2007 B-class flare: new insights fromHinodeobservations

Zanna¹,

Mitra-Kraev²,

Bradshaw

et al. 2010

A&A

Self Cite

View full text Add to dashboard Cite

We present multi-wavelength observations of a small B-class flare which occurred on the Sun on 2007 May 22. The observations include data from Hinode, GOES, TRACE and the Nobeyama Radioheliograph. We obtained spatially and spectrally-resolved information from the Hinode EUV Imaging Spectrometer (EIS) during this event. The temporal and temperature coverage of the EIS observations provides new insights into our understanding of chromospheric evaporation and cooling. The flare showed many "typical" features, such as brightenings in the ribbons, hot (10 MK) loop emission and subsequent cooling. We also observed a new feature, strong (up to 170 km s −1 ) blue-shifted emission in lines formed around 2-3 MK, located at the footpoints of the 10 MK coronal emission and within the ribbons. Electron densities at 2 MK in the kernels are high, of the order of 10 11 cm −3 , suggesting a very narrow layer where the chromospheric evaporation occurs. We have run a non-equilibrium hydrodynamic numerical simulation using the HYDRAD code to study the cooling of the 10 MK plasma, finding good agreement between the predicted and observed temperatures, densities and ion populations. Line blending for some potentially useful diagnostic lines for flares, which are observed with Hinode/EIS, is also discussed.

show abstract

Section: Flare Kernels: Source Regions Of Chromospheric Evaporationmentioning

confidence: 89%

The 22 May 2007 B-class flare: new insights fromHinodeobservations

Zanna¹,

Mitra-Kraev²,

Bradshaw

et al. 2010

A&A

Self Cite

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

“…The differential emission measure (DEM) indicates the amount of emission from plasmas at a specific temperature. As such, it can reflect the properties, such as the coronal heating mechanism, and was intensively investigated for variety of solar structures and events (e.g., Del Zanna 2013b; Del Schmelz et al 2013Schmelz et al , 2011bSchmelz et al ,a, 2009Hannah & Kontar 2012;Winebarger et al 2012;O'Dwyer et al 2011;Brooks et al 2012Brooks et al , 2011Reale et al 2009;Siarkowski et al 2008;Parenti & Vial 2007;Schmelz & Martens 2006;Lanzafame et al 2005Lanzafame et al , 2002Judge et al 1997;Thompson 1990;Fludra & Sylwester 1986;Sylwester et al 1980;Craig 1977;Craig & Brown 1976). The properties of emission in the core of an active region have been studied by Warren et al (2011), Tripathi et al (2011), and Viall & Klimchuk (2011, and typically found to be multithermal.…”

Section: Introductionmentioning

confidence: 99%

Differential emission measure analysis of active region cores and quiet Sun for the non-Maxwellianκ-distributions

Mackovjak

Dzifčáková

Dudík

2014

A&A

View full text Add to dashboard Cite

Context. The non-Maxwellian κ-distributions have been detected in the solar wind and can explain intensities of some transition region lines. Presence of such distributions in the outer layers of the solar atmosphere influences the ionization and excitation equilibrium and widens the line contribution functions. This behavior may be reflected on the reconstructed differential emission measure (DEM). Aims. We aim to investigate the influence of κ-distributions on the reconstructed DEMs. Methods. We perform DEM reconstruction for three active region cores and a quiet Sun region using the Withbroe-Sylwester method and the regularization method. Results. We find that the reconstructed DEMs depend on the value of κ. The DEMs of the active region cores show similar behavior with decreasing κ, or an increasing departure from the Maxwellian distribution. For lower κ, the peaks of the DEMs are typically shifted to higher temperatures and the DEMs themselves become more concave. This is caused by the less steep high-temperature slopes for lower κ. However, the low-temperature slopes do not change significantly even for extremely low κ. The behavior of the quiet-Sun DEM distribution is different. It becomes progressively less multithermal for lower κ with the EM-loci plots that indicate near-isothermal plasma for κ = 2. Conclusions. The κ-distributions can influence the reconstructed DEMs. The slopes of the DEM, however, do not change with κ significantly enough to produce different constraints on the heating mechanism in terms of frequency of coronal heating events.

show abstract

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

Cited by 39 publications

References 45 publications

The 22 May 2007 B-class flare: new insights fromHinodeobservations

The 22 May 2007 B-class flare: new insights fromHinodeobservations

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

Differential emission measure analysis of active region cores and quiet Sun for the non-Maxwellianκ-distributions

Contact Info

Product

Resources

About