[Loops] thermal nonequilibrium and thermal instability

[Hugh Hudson]

Jim, thanks, very clear and helpful as we eager readers of your papers have come to expect. Just a couple of quibbles:

Quibble No. 1. “Coronal rain” has traditionally been a phenomenon associated with “loop prominence systems”, “sporadic coronal condensations”, and many another term, but basically “flares”. I’ll read Patrick’s paper on the synchronization of raining strands next, but this synchronization might be less coincidental in a flare situation.

Quibble No.2. It seems to be customary in this community to use the terms “heating” and “cooling” to be volumetric. You don’t define your terms in this nice paper until Eq. 1, but that’s in the Appendix. I think the physics would be clearer if people made “heating” synonyous with “time rate of change of temperature”, and “cooling” the same way. This is not only more correct terminology, but also closer to the observable (T).

Hugh

> On Nov 26, 2019, at 9:55 PM, Klimchuk, James A. (GSFC-6710) <james.a.klimchuk at nasa.gov> wrote:
> 
> Hi Loops friends,
>  
> Attached is a paper just accepted by Solar Physics entitled "The Distinction Between Thermal Nonequilibrium and Thermal Instability," a topic which has caused some confusion.
>  
> Abstract:
> For some forms of steady heating, coronal loops are in a state of thermal nonequilibrium and evolve in a manner that includes accelerated cooling, often resulting in the formation of a cold condensation. This is frequently confused with thermal instability, but the two are in fact fundamentally different. We explain the distinction and discuss situations where they may be interconnected. Large-amplitude perturbations, perhaps associated with MHD waves, likely play a role in explaining phenomena that have been attributed to thermal nonequilibrium but also seem to require cross-field communication.
>  
> Best wishes,
> Jim
>  
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> James A. Klimchuk
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> <tne_vs_instability19_accepted.pdf>_______________________________________________
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