Intermittent Coronal Loop Oscillations by Random Energy Releases

Mendoza-Briceño, César A.; Erdélyi, R.

doi:10.1086/505642

Cited by 30 publications

(18 citation statements)

References 40 publications

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“…Mendoza-Briceño et al (2006) reported for this case a period of about 180 s, coming from a wavelet analysis of their time series, which matches well with this calculation. This might be and indication that the fundamental slow mode is being excited in their model, even if its spatial structure is not evident in their simulations due to the propagation, dissipation and nonlinear effects considered in their calculations.…”

Section: Slow Modes Of An Averaged Density Equilibrium Generated By Rsupporting

confidence: 88%

“…We deduce that it is not only important the total amount of material in the loop, but also its distribution. We can compare our analytical work with results obtained from 1D numerical simulations by Selwa et al (2005) and Mendoza-Briceño et al (2006), since the only comparison in these works was done with the results for a homogeneous loop. The hyperbolic density profile used in Selwa et al (2005) has a high density contrast between the footpoints and the apex.…”

Section: Discussionmentioning

confidence: 99%

“…Next we study the case of an equilibrium that arises from numerical simulations (Mendoza-Briceño et al 2006). To obtain the equilibrium, a number of pulses were introduced at random times and locations in a region near the footpoints.…”

Section: Slow Modes Of An Averaged Density Equilibrium Generated By Rmentioning

confidence: 99%

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Slow MHD oscillations in density structured coronal loops

Díaz

Roberts

2006

A&A

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Aims. Signals of stationary slow modes have been detected in observational data and modelled through numerical computations, comparing these results with the modes of a homogeneous tube. Here we explore the effect of structure along the magnetic field on the modes of oscillation of a coronal loop. Methods. We present a limit in which the slow mode is decoupled from the other magnetohydrodynamic modes, describing its behaviour in terms of a relatively simple partial differential equation. This equation is solved analytically and numerically for various longitudinal profiles. Results. For low density contrast between footpoints and apex, the modes of the structured tube are similar to the modes of the homogeneous tube, evolving regularly from them, with small modifications in frequency and spatial structure. As the density contrast is increased, the extrema are displaced towards the dense layers and the frequencies of the higher harmonics are strongly modified. Finally, as the ratio is increased further, two types of modes appear: modes approximately line-tied in the dense layer and modes with high amplitude in them (with avoided crossings between them in the dispersion diagrams). Conclusions. Different regimes can be identified, depending on the density contrast between the loop footpoints and its apex. This allows us to compare apparently different numerical results and understand their various features. Our analytical results are in accordance with current numerical simulations.

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Section: Slow Modes Of An Averaged Density Equilibrium Generated By Rsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

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Slow MHD oscillations in density structured coronal loops

Díaz

Roberts

2006

A&A

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“…One-dimensional calculations of time-dependent plasma behavior in response to impulsive heating just above the chromosphere were reported recently by Testa et al (2005) and Mendoza-Briceño & Erdélyi (2006) for semicircular flux tubes representing typical coronal loops of vastly different lengths (200 and 10 Mm, respectively). These studies are not directly comparable to the prominenceoriented work discussed here, because of fundamental differences in the assumed symmetries, heating pulse characteristics, and boundary conditions.…”

Section: Discussionmentioning

confidence: 94%

Condensation Formation by Impulsive Heating in Prominences

Karpen

Antiochos

2008

ApJ

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Our thermal nonequilibrium model for prominence formation provides an explanation for the well-observed presence of predominantly dynamic, cool, dense material suspended in the corona above filament channels. According to this model, condensations form readily along long, low-lying magnetic field lines when heating is localized near the chromosphere. Often this process yields a dynamic cycle in which condensations repeatedly form, stream along the field, and ultimately disappear by falling onto the nearest footpoint. Our previous studies employed only steady heating, as is consistent with some coronal observations, but many coronal heating models predict transient episodes of localized energy release (e.g., nanoflares). Here we present the results of a numerical investigation of impulsive heating in a model prominence flux tube and compare the outcome with previous steady-heating simulations. We find that condensations form readily when the average interval between heating events is less than the coronal radiative cooling time ($2000 s). As the average interval between pulses decreases, the plasma evolution more closely resembles the steady-heating case. The heating scale and presence or absence of background heating also determine whether or not condensations form and how they evolve. Our results place important constraints on coronal heating in filament channels and strengthen the case for thermal nonequilibrium as the process responsible for the plasma structure in prominences.

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“…The intermittent behavior of coronal loops, and their modeling by random energy deposition representing nanoflares of locally damped wave heating, was studied by Mendoza-Briceño et al (2002 and Mendoza-Briceño & Erdélyi (2006). However, showed that the observed spiky intensity profiles due to impulsive releases of energy could also be specifically obtained from nonlinear Alfvén wave heating.…”

Section: Introductionmentioning

confidence: 99%

Predicting Observational Signatures of Coronal Heating by Alfvén Waves and Nanoflares

Antolin

Shibata

Kudoh

et al. 2008

Astrophysical Journal

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Alfvén waves can dissipate their energy by means of nonlinear mechanisms, and constitute good candidates to heat and maintain the solar corona to the observed few million degrees. Another appealing candidate is nanoflare reconnection heating, in which energy is released through many small magnetic reconnection events. Distinguishing the observational features of each mechanism is an extremely difficult task. On the other hand, observations have shown that energy release processes in the corona follow a power-law distribution in frequency whose index may tell us whether small heating events contribute substantially to the heating or not. In this work we show a link between the power-law index and the operating heating mechanism in a loop. We set up two coronal loop models: in the first model Alfvén waves created by footpoint shuffling nonlinearly convert to longitudinal modes which dissipate their energy through shocks; in the second model numerous heating events with nanoflare-like energies are input randomly along the loop, either distributed uniformly or concentrated at the footpoints. Both models are based on a 1.5-dimensional MHD code. The obtained coronae differ in many aspects; for instance, in the flow patterns along the loop and the simulated intensity profile that Hinode XRT would observe. The intensity histograms display power-law distributions whose indexes differ considerably. This number is found to be related to the distribution of the shocks along the loop. We thus test the observational signatures of the power-law index as a diagnostic tool for the above heating mechanisms and the influence of the location of nanoflares.

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Intermittent Coronal Loop Oscillations by Random Energy Releases

Cited by 30 publications

References 40 publications

Slow MHD oscillations in density structured coronal loops

Slow MHD oscillations in density structured coronal loops

Condensation Formation by Impulsive Heating in Prominences

Predicting Observational Signatures of Coronal Heating by Alfvén Waves and Nanoflares

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