MULTI-STRANDED AND MULTI-THERMAL SOLAR CORONAL LOOPS: EVIDENCE FROM<i>HINODE</i>X-RAY TELESCOPE AND EUV IMAGING SPECTROMETER DATA

Schmelz, J. T.; Saar, S. H.; Nasraoui, K.; Kashyap, Vinay; Weber, Mark; DeLuca, E. E.; Golub, L.

doi:10.1088/0004-637x/723/2/1180

Cited by 40 publications

(27 citation statements)

References 32 publications

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“…Since the plasma is prohibited from moving across magnetic field lines, the energy released by magnetic reconnection is difficult to transfer into the CME LF. Therefore, during the magnetic reconnection, the CME flux rope is heated but the LF remains about the same temperature as the quiet coronal loops (e.g., T ∼ 1.0-3.0 MK; Schmelz et al 2010Schmelz et al , 2011aSchmelz et al , 2011b.…”

Section: Discussionmentioning

confidence: 99%

Differential Emission Measure Analysis of Multiple Structural Components of Coronal Mass Ejections in the Inner Corona

Cheng

Zhang

Saar

et al. 2012

ApJ

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271

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In this paper, we study the temperature and density properties of multiple structural components of coronal mass ejections (CMEs) using differential emission measure (DEM) analysis. The DEM analysis is based on the sixpassband EUV observations of solar corona from the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory. The structural components studied include the hot channel in the core region (presumably the magnetic flux rope of the CME), the bright loop-like leading front (LF), and coronal dimming in the wake of the CME. We find that the presumed flux rope has the highest average temperature (>8 MK) and density (∼1.0 × 10 9 cm −3 ), resulting in an enhanced emission measure over a broad temperature range (3 T(MK) 20). On the other hand, the CME LF has a relatively cool temperature (∼2 MK) and a narrow temperature distribution similar to the pre-eruption coronal temperature (1 T(MK) 3). The density in the LF, however, is increased by 2%-32% compared with that of the pre-eruption corona, depending on the event and location. In coronal dimmings, the temperature is more broadly distributed (1 T(MK) 4), but the density decreases by ∼35%-∼40%. These observational results show that: (1) CME core regions are significantly heated, presumably through magnetic reconnection; (2) CME LFs are a consequence of compression of ambient plasma caused by the expansion of the CME core region; and (3) the dimmings are largely caused by the plasma rarefaction associated with the eruption.

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Section: Discussionmentioning

confidence: 99%

Differential Emission Measure Analysis of Multiple Structural Components of Coronal Mass Ejections in the Inner Corona

Cheng

Zhang

Saar

et al. 2012

ApJ

Self Cite

271

249

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“…They have the same spatial resolution and cover different but overlapping coronal temperature ranges. These properties make a combined data set ideal for multithermal analysis, where the EIS iron lines provide the best information on the cooler corona (log T < 6.5) and the XRT iron-dominated filters provide the best information on the hotter corona (log T > 6.5); see, e.g., Schmelz et al (2010Schmelz et al ( , 2011b and Winebarger et al (2011). Table 2 lists the EIS ions, the wavelengths in angstroms, and the log of the peak formation temperatures of the spectral lines used in this analysis.…”

Section: Discussionmentioning

confidence: 99%

“…The second EMD method, xrt_dem_iterative2, was first developed (Weber et al 2004) and tested (Schmelz et al 2009) for XRT data alone, but is now applied more generally (see, e.g., Schmelz et al 2010;Winebarger et al 2011). The routine employs a forward-fitting approach where an EMD is guessed and folded through each response to generate predicted fluxes.…”

Section: Discussionmentioning

confidence: 99%

The Cold Shoulder: Emission Measure Distributions of Active Region Cores

Schmelz

Pathak

2012

ApJ

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The coronal heating mechanism for active region core loops is difficult to determine because these loops are often not resolved and cannot be studied individually. Rather, we concentrate on the "inter-moss" areas between loop footpoints. We use observations from the Hinode EUV Imaging Spectrometer and the X-Ray Telescope to calculate the emission measure distributions of eight inter-moss areas in five different active regions. The combined data sets provide both high-and low-temperature constraints and ensure complete coverage in the temperature range appropriate for active regions. For AR 11113, the emission can be modeled with heating events that occur on timescales less than the cooling time. The loops in the core regions appear to be close to equilibrium and are consistent with steady heating. The other regions studied, however, appear to be dominated by nanoflare heating. Our results are consistent with the idea that active region age is an important parameter in determining whether steady or nanoflare heating is primarily responsible for the core emission, that is, older regions are more likely to be dominated by steady heating, while younger regions show more evidence of nanoflares.

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“…We also compare our models to Model G (using the Bayes factor K iG ) Observations of hot coronal loops reveal them to be multithermal (e.g. Schmelz et al 2010Schmelz et al , 2014Nisticò et al 2014). However, Aschwanden & Nightingale (2005) found the majority of cooler loops to be well-approximated as isothermal, and Warren et al (2008) found isolated loops typically have very narrow temperature variation across the loop.…”

Section: Methodsmentioning

confidence: 99%

Coronal loop density profile estimated by forward modelling of EUV intensity

Pascoe

Goddard

Anfinogentov

et al. 2017

A&A

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Aims. The transverse density structuring of coronal loops was recently calculated for the first time using the general damping profile for kink oscillations. This seismological method assumes a density profile with a linear transition region. We consider to what extent this density profile accounts for the observed intensity profile of the loop, and how the transverse intensity profile may be used to complement the seismological technique. Methods. We use isothermal and optically transparent approximations for which the intensity of extreme ultraviolet (EUV) emission is proportional to the square of the plasma density integrated along the line of sight. We consider four different models for the transverse density profile; the generalised Epstein profile, the step function, the linear transition region profile, and a Gaussian profile. The effect of the point spread function is included and Bayesian analysis is used for comparison of the models. Results. The two profiles with finite transitions are found to be preferable to the step function profile, which supports the interpretation of kink mode damping as being due to mode coupling. The estimate of the transition layer width using forward modelling is consistent with the seismological estimate. Conclusions. For wide loops, that is those observed with sufficiently high spatial resolution, this method can provide an independent estimate of density profile parameters for comparison with seismological estimates. In the ill-posed case of only one of the Gaussian or exponential damping regimes being observed, it may provide additional information to allow a seismological inversion to be performed. Alternatively, it may be used to obtain structuring information for loops that do not oscillate.

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MULTI-STRANDED AND MULTI-THERMAL SOLAR CORONAL LOOPS: EVIDENCE FROMHINODEX-RAY TELESCOPE AND EUV IMAGING SPECTROMETER DATA

Cited by 40 publications

References 32 publications

Differential Emission Measure Analysis of Multiple Structural Components of Coronal Mass Ejections in the Inner Corona

Differential Emission Measure Analysis of Multiple Structural Components of Coronal Mass Ejections in the Inner Corona

The Cold Shoulder: Emission Measure Distributions of Active Region Cores

Coronal loop density profile estimated by forward modelling of EUV intensity

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