Multidimensional Modeling of Coronal Rain Dynamics

Fang, Xia; Xia, Chun; Keppens, Rony

doi:10.1088/2041-8205/771/2/l29

Cited by 73 publications

(123 citation statements)

References 24 publications

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“…As the coronal rain clumps fall along the loop arcade, they encounter an increasingly more dense atmosphere at the loop foot-points in the TR and on into the chromosphere. The reduced acceleration in the rain has also been observed in quiescent coronal rain (Antolin & Rouppe van der Voort 2012), and this was confirmed numerically to be due to the increase of gas pressure in the lower atmosphere with the greater local densities (Fang et al 2013).…”

Section: Observations Of Flare-driven Coronal Rainsupporting

confidence: 62%

“…Radiative losses increase and dominateover conductive losses, and at a later stage a loop-top thermal instability leads to catastrophic cooling (i.e., accelerated cooling) to chromospheric temperatures, and we observe a substantial loop drainage ordepletion, as observed here in Hα. During the thermal instability, the decrease in temperature in the loop is accompanied by a decrease in pressure, which then accretes plasma from the surrounding atmosphere, leading to the localized formation of dense rain condensations (Goldsmith 1971;Hildner 1974;Antiochos & Klimchuk 1991;Müller et al 2004;Fang et al 2013). Clumpy condensations eventually become dense enough to fall under gravity back to the surface (overwhelming the opposing magnetic pressure force of the loop arcade), resulting in a catastrophic depletion of plasma in the loop.…”

Section: Discussionmentioning

confidence: 99%

“…Coronal rain is a transient phenomenonwithin coronal loops and represents a key component of the mass cyclingbetween the solar chromosphere and corona, and itoccurs frequently in active regions (e.g., Kawaguchi 1970;Leroy 1972;Levine & Withbroe 1977;Schrijver 2001;O'Shea et al 2007;Antolin & Rouppe van der Voort 2012;Fang et al 2013;Ahn et al 2014;Antolin et al 2015, and see references therein). During its formation, coronal rain momentarily constitutes the finest-scale substructures of coronal loops, making it important to investigate with respect to understanding the heating of loops, the building blocks of the solar corona.…”

Section: Introductionmentioning

confidence: 99%

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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: Observations Of Flare-driven Coronal Rainsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observing the Formation of Flare-Driven Coronal Rain

Scullion

Voort

Antolin

et al. 2016

ApJ

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“…Animated views for the entire simulation in the format of Figure 2 are provided as online material, where the mentioned transverse compressions and their transient nature become evident. From our earlier simulations of actual prominence formation due to chromospheric evaporation, thermal instability, and runaway catastrophic cooling events (Xia et al 2011(Xia et al , 2012Fang et al 2013;, these transient shock waves mimic the rebound shock fronts found to result from siphon flow driven impacts on the prominence-corona transition region. These rebound shocks ultimately repeatedly impact on the prominence structure, as a result of successive reflections when they reach chromospherecorona transition regions along the fieldlines.…”

Section: Global Evolutionmentioning

confidence: 71%

Solar Prominences: “Double, Double… Boil and Bubble”

Keppens

Xia

Porth

2015

ApJ

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Observations revealed rich dynamics within prominences, the cool (10 4 K), macroscopic (sizes of order 100 Mm) "clouds" in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to RayleighTaylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting an MHD description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully nonlinear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh-Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence material. Synthetic views at extreme ultraviolet wavelengths show remarkable agreement with observations, with clear indications of shear-flow induced fragmentations.

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“…Interestingly, the blob leaves a trail (see last four images in the upper panel of Fig. 3), which might be a result of continuous cooling in the blob tails (Fang et al 2013). …”

Section: First Sequence Of Blobsmentioning

confidence: 98%

Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012

Vashalomidze

Kukhianidze

Zaqarashvili

et al. 2015

A&A

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Context. The formation and dynamics of coronal rain are currently not fully understood. Coronal rain is the fall of cool and dense blobs formed by thermal instability in the solar corona towards the solar surface with acceleration smaller than gravitational free fall. Aims. We aim to study the observational evidence of the formation of coronal rain and to trace the detailed dynamics of individual blobs. Methods. We used time series of the 171 Å and 304 Å spectral lines obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) above active region AR 11420 on February 22, 2012. Results. Observations show that a coronal loop disappeared in the 171 Å channel and appeared in the 304 Å line more than one hour later, which indicates a rapid cooling of the coronal loop from 1 MK to 0.05 MK. An energy estimation shows that the radiation is higher than the heat input, which indicates so-called catastrophic cooling. The cooling was accompanied by the formation of coronal rain in the form of falling cold plasma. We studied two different sequences of falling blobs. The first sequence includes three different blobs. The mean velocities of the blobs were estimated to be 50 km s −1 , 60 km s −1 and 40 km s −1 . A polynomial fit shows the different values of the acceleration for different blobs, which are lower than free-fall in the solar corona. The first and second blob move along the same path, but with and without acceleration, respectively. We performed simple numerical simulations for two consecutive blobs, which show that the second blob moves in a medium that is modified by the passage of the first blob. Therefore, the second blob has a relatively high speed and no acceleration, as is shown by observations. The second sequence includes two different blobs with mean velocities of 100 km s −1 and 90 km s −1 , respectively. Conclusions. The formation of coronal rain blobs is connected with the process of catastrophic cooling. The different acceleration of different coronal rain blobs might be due to the different values in the density ratio of blob to corona. All blobs leave trails, which might be a result of continuous cooling in their tails.

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Multidimensional Modeling of Coronal Rain Dynamics

Cited by 73 publications

References 24 publications

Observing the Formation of Flare-Driven Coronal Rain

Observing the Formation of Flare-Driven Coronal Rain

Solar Prominences: “Double, Double… Boil and Bubble”

Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012

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