Solar Cycle 24 Group F

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** COMMENT: This could be the low energy end of a spectrum
** COMMENT: This could be the low energy end of a spectrum
** Could be due to differential rotation, stress build-up
** Could be due to differential rotation, stress build-up
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==Wednesday==
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===Session 3: 09:00 - 10:30 – Intro talks (continued), Events Talks===
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====Virendra Verma: On the New Classifications of Solar Coronal Mass Ejections Based on LASCO/SOHO Observations (10 min)====
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* See how CMEs are connected with solar surface phenomena
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** Is initial speed of CMEs enough for escape velocity?
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* Two kinds – escape v and non-escape v CMEs
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** Many CMEs have non-escape v CMEs
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** Q: Accounting for LOS?
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*** No. Using plane-of-sky velocities. (COMMENT: not sure of validity…)
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* 59% have escape velocity
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** Half show (+) acceleration, half (-) acceleration
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** Overall, 2/3 have (+) acceleration (more non-escape have (+) acceleration)
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* Correlating flares and CMEs
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** 1/4 as many CMEs as flares
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* Higher velocities  have higher (-) acceleration
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** Appears to be a cut-off trend
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** COMMENT: most CMEs still have (+) acceleration, though
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* 5-10% of non-escape CMEs have zero velocity by 20 Rsun (?!?!)
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** Data come from LASCO CDAW catalog
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** COMMENT: suggestion that CMEs fade out, become unobservable
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* Most CMEs show (+) acceleration to 20 Rsun, a few have zero velocity at 20 Rsun
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** Q: How does a decelerating non-escape CME ESCAPE?!?!
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*** Measuring from edge of LASCO – presumably already escaped!
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*** COMMENT: does this, plus plane-of-sky problem, negate study results?
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* Conclusion: CMEs velocity affected by solar wind to accelerate or decelerate
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** COMMENT: Zhang & Dere (2006) shows (+) acceleration of CMEs , more than solar wind
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** Q: How to add acceleration to CMEs?
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*** Lorentz force?
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*** Mass deposit for transient coronal holes?
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* COMMENT: NEED TO ACCOUNT FOR PLANE-OF-SKY VELOCITIES TO MATCH ESCAPE VELOCITIES
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** Track back to sources using dimming regions?
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* COMMENT: Large statistical study will help
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====Dave Webb: Possible Events====
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* Possible types of CMEs
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** Limb events
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*** Good for accurate tracking, kinematics
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** Earth/STEREO-directed CMEs
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*** Can be connected to ICME
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*** Can be connected to source region on-disk
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** "Cradle to grave"
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*** Across multiple instruments
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* What is a source region?
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** Coronal surface phenomena: dimmings, waves
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** CME-flare relationship
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** Relating "cavities", prominences to 3-part CME
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* Necessity of current sheets?
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** Sometimes see bright rays in white light
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** 9 Apr 2008 shows a good one
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* Change of ICME definition now that they can be _imaged_?
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** Q: how to explain periodicity domination in HI data at 1 AU?  What does in-situ data look like?
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* Importance of prominences?
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* Campaigns:
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** WHI: 20 March-16 April 2008
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** 9 Apr 2008: XRT "cartwheel event"
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** Anything seen by STEREO, Hinode
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* Events (STEREO, Hinode):
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** 2006 Dec 13-15
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** 2007 Jan 21-25
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** 2007 May 19-22
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*** Set of homologous events
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** 2007 May 23
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** 2007 Nov 14-18
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*** Set of homologous events
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** 2007 Dec 31
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** 2008 March 25
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** 2008 April 9
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** 2008 April 26
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** 2007 May 17
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** 2008 June 6
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====Yan Li:  Overview of 19 May 2007 event ====
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* AR had homologous CMEs
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* CME is partial halo, pretty faint in LASCO
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* First fast CME seen by STEREO
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* On-disk origin
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** Can see wave, filament eruption, sigmoid
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** Complex neutral line structure
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* May not be truly "homologous", as different neutral lines erupt
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* Can see "Post-CME" loops under filament
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* Dimming region near filament location
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* Magnetic topology:  Breakout is lateral
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* Looked at total flux, see cancellation
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** Region is decaying
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* COMMENT: need to improve vector field analysis, add error bars
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====Alphonse Sterling: Overview of 20 May 2007 event====
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* Homologous with previous event, different neutral line
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* Small flare: B7
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* Filament eruption (surge-like)
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* TRACE  shows "surge", loop expansion
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* Quantitative evidence of cancellation, flux decrease
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** COMMENT: Is observed flux cancellation really the CME trigger?
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** COMMENT: Large-scale, quantitative study would be useful
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** Cancellation could be powering TRACE loops
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* Have SOT, EIS data of filament eruption (almost)
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** Fe XII shows persistent red-shifted flows (BEFORE eruption )
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* Conclusion: cancellation powers eruption
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* Q: Why is this event different?
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** Events like this might help us figure out how to PREDICT eruptions
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** Quantitative understanding of cancellation may help
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===Session 4: 11:00 - 12:30 – Joint with E (Flares)===
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NOTE: Group E didn’t know we were coming.  Not much CME discussion.
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====Eduard Kontar: X-ray Measurements of Magnetic Field and Density Structure in the Chromoshere ====
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* Looking at TRACE coronal loops
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* Can infer magnetic field from coronal observations
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* What is the structure of a flaring loop in the chromosphere?
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** Example: funnel
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* Limb flare from 6 Jan 2004
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** RHESSI data shows footpoints, looptop source
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* Energy of high energy electrons determines emission height in chromosphere (Aschwanden 2002)
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** Higher energy sources lower in chromosphere
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* Source sizes change with energy too
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** Increase in source size with height implies strong horizontal B
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* What is the actual footpoint shape?
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** Changes with energy – higher energy flatter
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* At scale height of 900 km, should expect strong horizontal B
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* Q: were other effects that would cause small source size considered (higher energy scattering etc.)?
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* Q: How get height measurements?
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** Use a density measurement
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====S. Masuda: GEMSIS-Sun: Modeling particle acceleration and transport in solar flares====
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* Flares related to successive reconnection
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* Hard x-ray emission corresponds to particle acceleration
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* Plasmoid should an indicator of magnetic reconnection
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* Can derive E from footpoint motion
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* Particle acceleration/transport related to magnetic field configuration
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* Acceleration sources:
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** B gradient
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** Curvature drift
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** Centripetal acceleration
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* Numerical model:
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** Able to produce a loop-top source
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** Produces an upward beam (source of Type III radio burst?)
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* Future plans
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** Include diffusion in model
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** Convert simulation output to emission
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** Need to understand multi-wavelength observations
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* Q: Does most acceleration come from loop-top? -Yes
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* Q: What processes are missing?
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====Pascal Saint-Hilare: X-ray emission from a current sheet in the wake of a CME & Long data accumulations with RHESSI====
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* Observations showing temperature goes down in wake of CME
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* RHESSI shows plasmoid moving out
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* Discontinuities seen at RHESSI flare onset
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* Try imaging spectroscopy to eliminate background
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** Results in double power law, see no non-thermal x-rays
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** No hard x-rays - hidden by soft x-rays?
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* Coronal probably not powered by accelerated particles
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* Why do higher energies come from higher altitudes?
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** Height related to ln(energy), fit not very good
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** COMMENT: consistent with high post-flare loops, cusps
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* COMMENT: flare driven for 8 hrs, likely a connection during this time between CME and post-flare loops
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** Adiabatic heating does not fit
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====Lindsay Glesener, Sam Krucker: Coronal HXR sources====
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* HXR emission from:
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** Acceleration region and paths away
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** Footpoints
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* Occulted flares eliminate bright footpoints
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* On Masuda flare loop-top source:
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** How many electrons necessary to produce HXR source?
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** HXR emission related to density
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** Assumption: density around 10^9
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** COMMENT: Need to account for temperature as well as density.  Also, could density be higher?
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** Energy of thermal/non-thermal electrons?
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*** Loop-top source entirely non-thermal (all electrons accelerated)
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*** Acceleration in loop-top source
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** Example: occulted flare from 2007 Dec 31
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*** Same event as discussed by Webb
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*** Microwave, HXR sources match
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**** COMMENT: could be a limb effect

Revision as of 20:39, 10 December 2008

Contents

McAteer Notes

INTRODUCTION

STERLING Earliest phases of solar eruptions

preflare phase & trigger mechanism for filaments as tracer of B field, slow rise -> flare + fast rise

few (12) example event studied. 2 may 2007, TRACE & HINODE, good example.

filaments undergo slow rise (few km/s), then fast. the slow rise is linear then flare at start of fast eruption. could be some signatures of 'breakout'

dimmings - local (near neutral line) or remote (associated with breakout?)


WHAT WILL WE LEARN: how common is a slow rise? what triggers slow & fast rise phases?

where to go from here? Clearly Hinode and SECCHI 171 2 min cadence? so synoptic data modes are fine for this project?


ATRILL Coronal waves and dimmings

EIT waves map the CME footpoints? Angelos -mixing lateral mass expansion & wave? Atrill - the expansion of CME stops when wave stops.

Explains the brightnenings at the CME legs

WD - Tunnelling of waves into coronal hole?

Dimmings: could be evacuation or cooling also agree with deep core and secondary dimmings

Mass measurements from plasma outflows?

Angelos: No brightenings in 304, so not reconnection? McAteer: reflection and refraction problem?

Attril: does not mean there is no wave, the CME footpoints could cause a wave?

why/how do CD disappear while magnetic connectivity of the CME ejecta to Sun is maintained? recovery can be due to Interchange reconnection.

reconnection rate at same speed as the wave? 0.1 X 0.2 alfven speed - too low?

expansion of cme flanks should correspond with eit wave speed.

Occams razor? why add in CME flanks and then introduce wave anyway. Overly complex?

WHAT WILL WE LEARN? New tests from multi viewpoint?

MCATEER CME Kinematics

–Kinematics is the study of the motion

–Energetics is the study of the forces which cause the motion.

•What forces govern the propagation?

•What forces govern the expansion?

from height time profiles -> acceleration profiles

• What are we tracking?

- image to image,

- event to event,

- study to study

• Can we reduce the errors?

• Are we capturing the full profile?

- What about lower down?


combine with mass -> work done, force and power.

WHAT WILL WE LEARN:

Known Knowns

•Well characterized and large sample studies from 3-30RSUN

•Well developed techniques to study energetics and kinematics


Known Unknowns

•Behaviour at 1-3RSUN and greater than 30RSUN

•Even at 3-30RSUN,

–where do the forces act and over what distance?

–when do the forces act and over what timescale?

Unknown Unknowns?

-What is the initiation mechanism?

-What is the CME - flare/filament link?

-The ever-illusive current sheet - any other choice?


from stereo - better H-T low down, and multi direction.

more automated tracking.


STEED locating the solar source

ICME ejecta - components of ICME show a left -handed cloud (-ve helicity)

launch window determined - 80hours before, roughly noon 10-april 2006 no obvious cme signatures (flares, dimmings, etc) survey possible launch regions.

search for source region with -Ve helicity. only one possible no erupting filaments, or possible cmes (because of lack of launch, conclude a back-sided event)

find some evidence of cusp shaped loop - > eruption signature? without vector data- cannot rule out helicity problems.


WHAT WILL WE LEARN?

HOWARD source regions A skeptics view of flare-cme relationship

how do we define a flare and a cme? cme- outward propagation of brightness enhancement in WLC flare - brightening in cr, tr or coronal emmisison

associating lists is dangerous all current theories have a flare as necessary consequence of eruption, but not neccesaary cause and effect.

There are CME without flares -called backside, faint flare (not in GOES) there are cmes which have no chromospheric signatures - 'streamer blowout'

with stereo - we can see these are not backsided.

obvious controversy suggest we are a long way from solving this problem -different people see different conclusions from the same data!

WHAT WILL WE LEARN? Need to nail down an agreed definition? With STEREO we can rule out backsided possibility - can we also rule out the 'too low for GOES? If so, then we have a non-flare CME and we need a new approach.


VERMA A new classification of CMEs?

calculate escape velocity Alphonse- What about LOS projection? - not accounted for.

NEVCME 41%, mostly +ve accleration Ev CMEs 59%, half +ve, half -ve overall 68% show +ve acc

WHAT WILL WE LEARN:

LOS question is vital: problems with just looking at the stats, not looking at the data


EVENTS

WEBB - overall discussion and questions to be addressed

Types of CMES -limb (good for H-T) -earth directed OR spacecraft directed (good for connecting CME / ICME and finding source regions -cradle to grave events

What is source region? dimmings, waves, slow rises extents, locations flares, prominences cavities

How essential are current sheets? 9-Apr-2008 has well observed current sheet?

How do we define an ICME now that we can image ICMEs what do we see in HI and how does this compare to in-situ?

How essential are prominences & eruption - joint with WG J

Campaign Focus events WHI 20 march -16 april 2008 9 apr 2008 event

Events Obs Science

2006 dec 13-15 2 X-ray flare near sun center ICME flux rope, SEP at earth, STEREO space weather event. secchi.nrl.navy.mil/spwx/

2007 Jan 24-25 2 CMEs east limb. SECCHI, SOHO, SMEI papers: Harrison et al, Lugaz et al, Webb et al

2007 May 19-22 2 events near sun center, HINODE & STEREO 3D view of filament lift off

2007 May 23 AR on west, wave, prom eruption, CME HINODE & STEREO

2007 Nov 14-18 3 events, 1 at sun center

2007 Dec 31 east limb

2008 March 25 east limb, during WHI

2008 April 9 west limb, XRT, EIS, SECCHI, UVCS interaction with CH

2008 April 26 near sun center, fast cme & euv wave

2008 May 17 sun - STEREO interaction

2008 Jun 6 magnetic cloud at STEREO B

2008 Feb 4-8 2008 June 2-6 wood et al. 2008 robbrecht et al. 2008


WHAT ARE THE ISSUES? connection with flares - few large (>M) flares since STEREO launched.

LI - May 19, 2007 CME & B field of AR 10956

B9 flare, 960Km/s sun center AR pre eruption sigmoid structure in XRT B field topology - Li et al, ApJL 2008 classic breakout model configuration?

total B flux in region decreased 17% 48 hours before flare, so weakening of overlying field?

pre flare brigthening - tether cutting?


STERLING - May 20, 2007

B7 flare, well observed with TRACE, STEREO pre flare surges. reduction in B field

Angelos- constant flux cancellation, so what can we say quantitatively?

EIS box also rastered over this region.

-persistent red shifted flow and non thermal broadenings

-strongest shifts are 20Km/s

-typical densities of fewX 10^9 cm^-3

WHAT WILL WE LEARN?

Angelos - anything new?

Sterling - can we predict eruption?

Cartoon picture explanation. again person A see different conclusion from same data than person B.

EVENT 3

Wills-Davey Notes

Tuesday

Session 1: 14:30 - 16:00 - Intro Talks

Alphonse Sterling: Introduction to Group F Agenda

Alphonse Sterling: The earliest phases of solar eruptions

Gemma Atrill: Coronal ’waves’ and dimmings - what can they tell us about their CME counterparts?

Session 2: 16:30 - 18:00 - Intro talks (continued)

James McAteer: Kinematics of Coronal Mass Ejections: Theory and Observations

Kimberley Steed: Solar source of a magnetic cloud; overview of 13 April 2006 event

Russ Howard: A skeptic’s view of CME-Flare relationship

Wednesday

Session 3: 09:00 - 10:30 – Intro talks (continued), Events Talks

Virendra Verma: On the New Classifications of Solar Coronal Mass Ejections Based on LASCO/SOHO Observations (10 min)

Dave Webb: Possible Events

Yan Li: Overview of 19 May 2007 event

Alphonse Sterling: Overview of 20 May 2007 event

Session 4: 11:00 - 12:30 – Joint with E (Flares)

NOTE: Group E didn’t know we were coming. Not much CME discussion.

Eduard Kontar: X-ray Measurements of Magnetic Field and Density Structure in the Chromoshere

S. Masuda: GEMSIS-Sun: Modeling particle acceleration and transport in solar flares

Pascal Saint-Hilare: X-ray emission from a current sheet in the wake of a CME & Long data accumulations with RHESSI

Lindsay Glesener, Sam Krucker: Coronal HXR sources

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