[Loops] [EXTERNAL] Re: Loops Digest, Vol 6, Issue 2

Wed May 19 08:51:42 MDT 2021

Sorry, the third mechanism is actually called "reconnection driven current filamentation." It's something that Judy Karpen, Spiro, and colleagues pointed out some years ago. 

Jim

-----Original Message-----
From: Loops <loops-bounces at solar.physics.montana.edu> On Behalf Of Klimchuk, James A. (GSFC-6710)
Sent: Wednesday, May 19, 2021 9:13 AM
To: Philippa Browning <philippa.browning at manchester.ac.uk>; loops at solar.physics.montana.edu
Subject: Re: [Loops] [EXTERNAL] Re: Loops Digest, Vol 6, Issue 2

Hi Philippa,

Thanks! Yes, the formation of current sheets by kink instability - that you, Alan, and your colleagues have modeled so beautifully - is just one of the several mechanisms for producing current sheets that do not involve a turbulent cascade. We also point to three others in the paper:  

1.  simple driver flows acting on coronal separatrices and QSLs that result from the clumping of the field in the photosphere (what Eric called "coronal tectonics";

2.  complex driver flows involving things like stagnation points;

3.  current driven filamentation that results from patchy reconnection.

Also, Hugh pointed out in an e-mail the current sheets are also produced when new flux emerges into pre-existing flux. This could be very important in the low-lying magnetic carpet of the quiet Sun, but probably is not so important in active regions, which are unipolar over large areas.

Thanks again,
Jim

-----Original Message-----
From: Loops <loops-bounces at solar.physics.montana.edu> On Behalf Of Philippa Browning
Sent: Wednesday, May 19, 2021 5:44 AM
To: loops at solar.physics.montana.edu
Subject: [EXTERNAL] Re: [Loops] Loops Digest, Vol 6, Issue 2

Hi Jim 
Thanks for sharing this nice paper. The ideas you develop do seem very consistent with some of my earlier work, and indeed you do reference Hood et al (2009) (doi: 10.1051/0004-6361/200912285) - thank you! We showed here that even very smooth and simple motions in the photosphere can produce a very complex field in the corona with multiple fragmented current sheets. Whether one calls this "turbulence" or not is a matter of nomenclature, but it is certainly not classic Kolmogorov. Your statement  "It nonetheless has a complex structure that bears no direct relationship to the pattern of driving" sums this up very nicely.
Prior to this, Browning and Van der Linden (2003) (doi   10.1051/0004-6361:20021887) proposed that a repeated series of energy release triggered by kink instability could produce  a distribution of nanoflares - this was verified by Bareford et al (2010, 2011) (10.1051/0004-6361/201014067) where we show you can actually get a power law distribution from a random twistings. These were simple semi-analytical models, but I think there is scope to follow through on some of these ideas with simulations.
Of course the reality involves ongoing  and more complex patterns of driving- and the possibility of avalanching, as we showed in Hood et al (2016) (10.3847/0004-637X/817/1/5) and  pursued in the  interesting recent work of Knizhnik et al of course. It seems one localised  kink instability can generate a lot of current sheets and energy release!
Best wishes
Philippa

-----Original Message-----
From: Loops <loops-bounces at solar.physics.montana.edu> On Behalf Of loops-request at solar.physics.montana.edu
Sent: 18 May 2021 19:00
To: loops at solar.physics.montana.edu
Subject: Loops Digest, Vol 6, Issue 2

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Today's Topics:

   1. Is the corona turbulent? (Klimchuk, James A. (GSFC-6710))

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Message: 1
Date: Tue, 18 May 2021 13:24:09 +0000
From: "Klimchuk, James A. (GSFC-6710)" <james.a.klimchuk at nasa.gov>
To: " (Loops at solar.physics.montana.edu)"
	<Loops at solar.physics.montana.edu>
Subject: [Loops] Is the corona turbulent?
Message-ID:
	<BY3PR09MB857890CB88D737802F4BB975B02C9 at BY3PR09MB8578.namprd09.prod.outlook.com>

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Dear "loops" friends,

You might be interested in the paper that Spiro and I just published concerning the role of turbulence in forming the current sheets that spawn nanoflares in the magnetically closed corona:

https://gcc02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fjournal.frontiersin.org%2Farticle%2F10.3389%2Ffspas.2021.662861%2Ffull%3F%26utm_source%3DEmail_to_authors_%26utm_medium%3DEmail%26utm_content%3DT1_11.5e1_author%26utm_campaign%3DEmail_publication%26field%3D%26journalName%3DFrontiers_in_Astronomy_and_Space_Sciences%26id%3D662861&data=04%7C01%7Cjames.a.klimchuk%40nasa.gov%7C930d0c80004d4213fdbd08d91ac8155b%7C7005d45845be48ae8140d43da96dd17b%7C0%7C0%7C637570268927468887%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=bQb51N%2FcCTVjDiB9joyPIa5KpBRKY7JkGU9b09U3W0w%3D&reserved=0<https://gcc02.safelinks.protection.outlook.com/?url=http%3A%2F%2Flinks.email.frontiersin.org%2Fls%2Fclick%3Fupn%3DDpg5ochww630xh6EMvshS4k2vZe-2Fd8MH-2FVpzt1-2FUQD91C-2FNL5bIclwWnNjv5HD9iMag7H9cVj-2BaBijWs5wuQwUXGW9NyPeWUv4iTl-2BnBax2aHS9bQA35nvW9uq-2Bmr6AtXL2IjuwOUKORbZg-2FzNJWcN4sHVlQ9lSDuuvavFo1L1-2BOVcshXIXHqtOpHeMp-2Fa-2BbbDtcPlJ2HX
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 g6QSXzWA2wXgA4DkQrYG8zw9-2BrhOoZY5D8wkA-3D-3D&data=04%7C01%7Cjames.a.klimchuk%40nasa.gov%7C5e1b386e3d2042eee27f08d919b402e2%7C7005d45845be48ae8140d43da96dd17b%7C0%7C0%7C637569083199946822%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=hjrQ5rwifhz4O8XDZt6jIUTLTdxEi45UOl%2FQuFGWNOU%3D&reserved=0>

We argue that the sheets form primarily from other processes, unrelated to turbulence. Localized temporary bursts of turbulence may nonetheless be generated when the sheets reconnect.

Abstract:
We argue that the magnetically closed corona evolves primarily quasi-statically, punctuated by many localized bursts of activity associated with magnetic reconnection at a myriad of small current sheets. The sheets form by various processes that do not involve a traditional turbulent cascade whereby energy flows losslessly through a continuum of spatial scales starting from the large scale of the photospheric driving. If such an inertial range is a defining characteristic of turbulence, then the magnetically closed corona is not a turbulent system. It nonetheless has a complex structure that bears no direct relationship to the pattern of driving.

Cheers,
Jim

********************************************************************************
James A. Klimchuk
NASA Goddard Space Flight Center
Solar Physics Lab, Code 671
Bldg. 21, Rm. 158
Greenbelt, MD  20771
USA

Phone:  1-301-286-9060<tel:%28301%29%20286-9060>
Fax:      1-301-286-7194<tel:%28301%29%20286-7194>
E-mail:  James.A.Klimchuk at nasa.gov<mailto:James.A.Klimchuk at nasa.gov>
Homepage:  http://science.gsfc.nasa.gov/sed/bio/james.a.klimchuk<http://science.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&&iPhonebookId=15844>

No endorsement by NASA is implied for any correspondence related to my official role in professional organizations.

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