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Lenz, Dawn D.; DeLuca, E. E.; Golub, L.; Rosner, R.; Bookbinder, Jay A.; Litwin, C.; Reale, F.; Peres, G.

doi:10.1023/a:1005209616355

Cited by 29 publications

(30 citation statements)

References 11 publications

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“…Figure 8 clearly shows that the whole loop is involved in coherent emission variations. The presence of a constant high emission level may then indicate that the cooling process involves only a fraction of the individual strands which the loop may consist of (see also Lenz et al 1999). As mentioned above, some thermal structuring along the line of sight may be required also for consistency with Yohkoh data.…”

Section: Discussionmentioning

confidence: 87%

CDS/SoHO multi-line observation of a solar active region: Detection of a hot stable loop and of a cool dynamic loop

Giorgio¹,

Reale²,

Peres³

2003

A&A

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Abstract. We analyze a space-, time-and spectral-resolved SoHO/CDS observation of the evolution of an active region over a time lapse of approximately three hours in various spectral lines emitted in the interval of temperature 1.3 × 10 4 < T < 2.5 × 10 6 K. We identify and characterize two structures of interest: a longer coronal loop (≈5.5 × 10 9 cm), relatively steady and well visible in lines forming at coronal temperatures (e.g. Fe XIV 334.17 Å, Fe XVI 360.76 Å) and a smaller one (≈1.8 × 10 9 cm), transient and visible only in cooler lines (O IV 554.51 Å, O V 629.73 Å). In the hot lines, the longer loop has a bright apex and an emission distribution of constant shape, but of moderately variable absolute intensity; the region around the loop apex shows a distinct brightening practically in all lines. In the hot lines, the brightening appears as a minor perturbation over a steadily high emission level. In the same region the emission measure vs temperature of the hottest lines indicates a temperature of ∼2 MK, lower than the temperature obtained from Yohkoh data taken just before the CDS observation. Comparison with steady-state loop scaling laws and with plasma time scales, and connection to cooling or heating episodes are discussed. As for the cool loop, its whole evolution, from ignition to disappearance, is directly observed, confirming the highly transient nature of such structures. The O V line is blue-shifted at one footpoint, indicating an upflow associated with the loop ignition.

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Section: Discussionmentioning

confidence: 87%

CDS/SoHO multi-line observation of a solar active region: Detection of a hot stable loop and of a cool dynamic loop

Giorgio¹,

Reale²,

Peres³

2003

A&A

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“…Goddard et al (2017) studied the density profiles of 233 coronal loops and found that the majority exhibit evidence for having an inhomogeneous layer of finite width. The potential for seismological techniques to provide structuring information is also relevant for studies of multi-threaded coronal structures considered by many authors (e.g., Lenz et al 1999;Aschwanden et al 2000;Pascoe et al 2007;Brooks et al 2012;Antolin et al 2015;Aschwanden & Peter 2017).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Analysis of Coronal Loops Using Seismology of Damped Kink Oscillations and Forward Modeling of EUV Intensity Profiles

Pascoe

Anfinogentov

Goddard

et al. 2018

ApJ

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The shape of the damping profile of kink oscillations in coronal loops has recently allowed the transverse density profile of the loop to be estimated. This requires accurate measurement of the damping profile that can distinguish the Gaussian and exponential damping regimes, otherwise there are more unknowns than observables. Forward modeling of the transverse intensity profile may also be used to estimate the width of the inhomogeneous layer of a loop, providing an independent estimate of one of these unknowns. We analyze an oscillating loop for which the seismological determination of the transverse structure is inconclusive except when supplemented by additional spatial information from the transverse intensity profile. Our temporal analysis describes the motion of a coronal loop as a kink oscillation damped by resonant absorption, and our spatial analysis is based on forward modeling the transverse EUV intensity profile of the loop under the isothermal and optically thin approximations. We use Bayesian analysis and Markov chain Monte Carlo sampling to apply our spatial and temporal models both individually and simultaneously to our data and compare the results with numerical simulations. Combining the two methods allows both the inhomogeneous layer width and density contrast to be calculated, which is not possible for the same data when each method is applied individually. We demonstrate that the assumption of an exponential damping profile leads to a significantly larger error in the inferred density contrast ratio compared with a Gaussian damping profile.

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“…We estimate the spatial scale of the sub-structure of the coronal loop in the context of a monolithic loop, which may also correspond to the characteristic scale of multi-threaded coronal structures (e.g. Lenz et al 1999;Aschwanden et al 2000;Brooks et al 2012;Antolin et al 2015).…”

Section: Introductionmentioning

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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Untitled

Cited by 29 publications

References 11 publications

CDS/SoHO multi-line observation of a solar active region: Detection of a hot stable loop and of a cool dynamic loop

CDS/SoHO multi-line observation of a solar active region: Detection of a hot stable loop and of a cool dynamic loop

Spatiotemporal Analysis of Coronal Loops Using Seismology of Damped Kink Oscillations and Forward Modeling of EUV Intensity Profiles

Coronal loop density profile estimated by forward modelling of EUV intensity

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