RHESSI-Nessie II WG 3: “From sites of radiation to particle sources” Three sub-groups, to have appointed times in the program Specific educational questions.

RHESSI-Nessie II WG 3:“From sites of radiation to particle sources”

• Three sub-groups, to have appointed times in the program

• Specific educational questions to be shared and perhaps answered by Friday

• Collaborations leading to meaningful papers to be encouraged

Focus area #1: propagation

• “Realistic” magnetic fields: drifts, scattering, energy losses, trapping, Neupert effect

• Interested members? Fletcher, Galloway, Gordovskyy, Hannah, Hudson, Melnikov, Petrosian, Veronig

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Null?

Separatrices?

Anzer-Pneuman, 1982

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Focus area #2: Radiation

1. “Realistic” magnetic fields: Microwave and X-ray luminosity, coronal emission, Alfven speeds, “cornucopia effect”

• Interested members? Fletcher, Gallagher, Hudson, Mann, McTiernan, Veronig, Warmuth

Focus area #3: Footpoint physics

• Particle penetration into the lower atmosphere. Positron creation and decay. DEM.

• Interested members? Allred, Brown, Fletcher, Hudson, Murphy, Ryan, Veronig, Woods

Bastille day 2000 (Fletcher & Hudson, 2001)

Tentative schedule, Team 3

Wednesday 11:00 - lunch Team organization; Propagation themeWednesday 14:00 - 16:00 Focus area #1: Radiation themeWednesday 16:30 - supper Focus area #2: Events

Thursday 09:30 - 10:30 Discussion of coronaThursday 11:00 - lunch Focus area #3: Footpoint physicsThursday 14:00 - 16:00 Propagation: answers to questionsThursday 16:30 - supper Radiation: answers to questions

Friday 09:00 - 10:30 Footpoints: answers to questionsFriday 11:00 - lunch Working session(s)Friday 14:00 - 16:00 Recap, followed by working session(s)

RHESSI current sheet?

• Sui & Holman, ApJ 2001

• Homologous flare to that discussed by Astrid

• Signature appears in two other events

• Current-sheet signatures in UVCS data

Radiative hydrodynamicsen train

Propagation Questions

• To what extent are electron footpoints smeared out by drift motions? Being studied… maybe?

• To what extent can ions and electrons be separated spatially? Considerably

• Do separatrices correspond to ribbons, or (Metcalf et al, 2003) are they intriguingly related? Being studied

• Does trapping and Coulomb loss explain 34-GHz looptop sources? Being studied… probably?!

• At what time scale does the steady-state approximation break down? Experts discussing

Cartoon by Jakimiec

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Radiation Questions

• Does trapping and Coulomb loss explain 34-GHz looptop sources? Being studied… probably?!

• Can a coronal loop be dense enough to stop 60 keV electrons? Yes; new input to models

• Do RHESSI observatinos suggest a coronal current sheet? Yes… being studied

• Can “realistic” field extrapolations help to understand flare X-ray sources? Being studied

Footpoint Questions

• Do electron-heated atmospheres produce thick enough transition regions to explain the 511-keV line width? No

• Do proton-heated atmospheres produce thick enough transition-region material to explain the 511-keV line width? Being studied

• Do we understand footpoint DEMs well enough to explain ribbon radiation? Being studied

• Do we understand why hard X-ray footpoint structures are so concentrated in the ribbons? Being studied

Slide 8

April 21, 2002:Brian Dennis, of course!

Collaborative projects

• Inputs for radiative hydrodynamics models, for example the return current

• Proton beam simulations and 511 line• Intercomparison of B-cubes for AR 486 and

others• “Realistic” magnetic models applied to flare

radiation sources