Unsteady reconnection session

1SHINE2009 Intrator LA-UR-08-0324

Unsteady reconnection session

• Working group coordinators: T. Intrator, J. Borovsky - LANL • 30-40 participants• Energy stored in stressed magnetic fields

can produce large scale explosive events• Unsteady, impulsive, multi time scale,

probably requires 3D to exist• Reality is rarely steady state, but our

concepts & models are• How and where does reconnection

– Initiate? … Stagnate?


Unsteady solar reconnection

• Surveys of solar flare energy release observations– L. Fletcher-Univ. Glasgow: Unsteady signatures in solar flares

– J. Qiu- Univ. Montana: Reconnection in solar flares -- 2D to 3D

– P. Bellan-Caltech: Alfven waves = field line twist = energy flow

• Flare energy release is probably mediated by reconnection, but not yet definitively proven– No clean diagnostics for electron acceleration time scales

– Hard to separate time and spatial scales

– Overlapping time scales are not very distinct

– measured data characteristic time scales evenly spread down to resolution ≈ 0.1-0.3 seconds, probably faster in future data

– Proxy data: UV footpoints track reconnection inflow speed => “rcxn rate”


Unsteady 3D Reconnection

•3D geometry? • Sweet-Parker model is a 2D concept

– T. Forbes - UNH: 3D models for reconnection in solar flares.

– T. Intrator - LANL: 3D experiment

– I. Roth - UCB-SSL: Generalized vorticity, asymmetric rcxn

• Quasi separatrix layers and slip-squash reconnection seem practical alternatives to singular spine-fan-separator concepts.

• Lab experiment invokes Sweet-Parker definition for onset threshold. Convenient but correct?

• THEMIS Spacecraft observes asymmetric reconnection


Impulsive Magnetic Reconnection

•Onset of reconnection?– A. Bhattacharjee - UNH: Tectonic model => unsteady rcxn

dynamics

– M. Yamada - Princeton: MRX data shows impulsive rcxn

– T. Intrator - LANL: RSX data shows kink instigated rcxn

• Unsteady dynamics can follow from 2D & 3D theories, definitely occurs in 3D lab data, nature



•Flow fields?• Proxy flare measurements can back out in-

flow, reconnection rate assuming MHD– magnetic flux conservation

– photospheric line-tying

– separatrices in motion

– energy release/transport along the “line”

•Dynamics? – Back reaction of flux pileup on initial state?– Compressibility? Stagnation flows?– Some laboratory data (RSX)



• Boundary conditions?– Some discussion of line tying. Concluded that

this is a boundary condition and applies to field lines at the boundary. But many presume it to be a stronger condition than this.


Scientific desires

• Improved proxy data for flares, or more direct measurements– Faster time cadence– Improve measurements or estimates for B,

velocity, reconnection rate– Deconvolve temporal and spatial scales

• More attention to 3D concepts, theories• Some laboratory data


Unsteady Magnetic Reconnection


Unsteady rcxn session• Wednesday morning, Salon E

– 10:05-11:05AM, 11:05-11:30-break, 11:30AM-1:00PM =>150min

• Invited talks: ≈ 25 minutes each– Intrator intro - 5 min

– L. Fletcher-Univ. Glasgow: Unsteady signatures in solar flares

– J. Qiu- Univ. Montana: Reconnection in solar flares -- 2D to 3D

– T. Forbes - UNH: 3D models for reconnection in solar flares

– A. Bhattacharjee - UNH: Impulsive current sheets & rcxn

– Roth, Intrator, Yamada, Bellan

– Edmondson, Evans, Savage, … posters or talks? others??

– Posters P142-P146

Unsteady reconnection session

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