Thermodynamic evolution of flares

Sylwester, B.; Sylwester, J.; Jakimiec, J.; Serio, S.; Reale, F.

doi:10.1007/bfb0032637

Cited by 30 publications

(43 citation statements)

References 3 publications

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“…Conductive cooling may account for faster cooling timescales in flaring conditions (Doschek et al 1982) when the temperature gradients are largest. The conductive cooling phase starts at the temperature peak and continues to the peak of the EM (Cargill 1994), which is common in flare observations (Sylwester et al 1993). In this flare, at the start of the cooling phase III, the temperature peaks measurably before the EM (see Figure 20).…”

Section: Conductive Coolingmentioning

confidence: 68%

Observing the Formation of Flare-Driven Coronal Rain

Scullion

Voort

Antolin

et al. 2016

ApJ

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Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal looptops in thermally unstable postflare arcades. We detect fivephases that characterize the postflare decay: heating, evaporation, conductive cooling dominance for ∼120 s, radiative/enthalpy cooling dominance for ∼4700 s, and finally catastrophic cooling occurring within 35-124 s, leading to rain strands with aperiodicity of 55-70 s. We find an excellent agreement between the observations and model predictions of the dominant cooling timescales and the onset of catastrophic cooling. At the rain-formation site, we detect comoving, multithermal rain clumps that undergo catastrophic cooling from ∼1 MK to ∼22,000 K. During catastrophic cooling, the plasma cools at a maximum rate of 22,700 K s −1 in multiple loop-top sources. We calculated the density of the extreme-ultraviolet (EUV) plasma from the differential emission measure of the multithermal source employing regularized inversion. Assuming a pressure balance, we estimate the density of the chromospheric component of rain to be 9.21×10 11 ±1.76×10 11 cm −3 , which is comparable with quiescent coronal rain densities. With up to eightparallel strands in the EUV loop cross section, we calculate the mass loss rate from the postflare arcade to be as much as 1.98×10 12 ±4.95×10 11 g s −1 . Finally, we reveal a close proximity between the model predictions of 10 5.8 K and the observed properties between 10 5.9 and 10 6.2 K, whichdefines the temperature onset of catastrophic cooling. The close correspondence between the observations and numerical models suggests that indeed acoustic waves (with a sound travel time of 68 s) could play an important role in redistributing energy and sustaining the enthalpy-based radiative cooling.

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Section: Conductive Coolingmentioning

confidence: 68%

Observing the Formation of Flare-Driven Coronal Rain

Scullion

Voort

Antolin

et al. 2016

ApJ

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“…a shorter loop length) if significant heating is present during the decay. The slope ζ of the decay path in the density-temperature diagram (Sylwester et al 1993) is maximum (∼2) if the heating is negligible in the decay and minimum (∼0.5) -the slope of the loci of the hydrostatic loops with decreasing temperature -if the heating dominates the decay (Sylwester et al 1993). From Eq.…”

Section: The Flaresmentioning

confidence: 98%

XMM-Newton observation of the young open cluster Blanco 1

Pillitteri

Micela

Reale

et al. 2005

A&A

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Abstract.We study the X-ray variability of the young open cluster Blanco 1 observed with the EPIC camera on board the XMM-Newton X-ray observatory. The time coverage of EPIC observations has allowed us to address short time scale (hours) variability, while the comparison with previous ROSAT observations has allowed us to investigate the variability on time scale of six years. On the time scale of hours, dM stars of the cluster are more variable than solar-mass stars. The main features of X-ray light curves in dM stars appear to be essentially flare-like events with a typical duration of the order of a few ks, while dF-dG stars show smooth variations. Two intense flares were observed in the ZS76 cluster member. From the analysis of the light curves and of the time resolved X-ray spectroscopy we infer that they occurred in arcades, made of several similar coronal loops (∼10 10 cm long), ignited at ∼15 ks time delay. Minor heat pulses may occur in the first flare. The similarity of the two flares and of the flaring inferred structures may suggest that the flares are physically connected to each other. Amplitude variations on the time scale of 6 years are smaller by a factor 2, whereas a factor of 10 is observed on the Sun in the same band. This implies a smaller amplitude of any analog of the 11-yr cycle in these young active coronae.

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“…Some observational support for these scalings comes from the work of Sylwester et al (1993). They first carried out numerical hydrodynamic simulations of cooling flare plasma and from the results calculated n − T and corresponding √ EM − T diagrams, where EM is the emission measure.…”

Section: Comparison Between the Analytical Model And Numerical Simulamentioning

confidence: 99%

“…Subsequent investigations by Sylwester et al (1993) and Cargill et al (1995, hereafter CMA95) showed that while δ was not always two, the generic power-law relationship was very robust. The difference between these two approaches to radiative cooling are significant.…”

Section: Introductionmentioning

confidence: 96%

The cooling of coronal plasmas

Bradshaw¹,

Cargill²

2005

A&A

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Abstract. The robust T ∝ n δ power-law relationship between the temperature (T ) and the density (n) that arises during the radiative cooling phase of a solar coronal loop is investigated. Using an analytical model and numerical hydrodynamic simulations, we demonstrate that radiative energy loss from the transition region is the dominant physical process. It governs the down-flow by which mass is lost from the corona and hence controls the evolution of the entire loop. We also show that the down-flow is initiated by a weakening of the pressure gradient between the corona and the transition region, such that the plasma can no longer be supported in hydrostatic equilibrium. Rather than driving the down-flow, the pressure gradient actually regulates it and acts as a brake against gravitational acceleration.

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Thermodynamic evolution of flares

Cited by 30 publications

References 3 publications

Observing the Formation of Flare-Driven Coronal Rain

Observing the Formation of Flare-Driven Coronal Rain

XMM-Newton observation of the young open cluster Blanco 1

The cooling of coronal plasmas

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