Coronal Magnetic Fields: Plan of Action

1. Coronal Magnetic Fields: Plan of Action • Hare and hounds initiative (leader: Penn) • Initiative on instrumental limits (leaders: Mickey, Penn) • Initiative on pioneering measurements of magnetic fields in the solar corona (Leaders: Kuhn, Lin, Mickey) • Initiative on the use of Coronal Magnetic Field measurements in theoretical models (Leaders: Fisher, Roussev, Li) • Initiative on integration with other measurements (leader: Hudson[?]) • Appendix: Other research projects spawned by our workshop: Measurement of prominence masses and geometries [Hudson]

2. Hare and Hounds Initiativeleader: Penn • 1. Generate coronal models: active region, flux rope, helmets, CMEs, filaments: B(x,y,z), n(x,y,z), T(x,y,z) (15 Jan) • Global analytic and plane parallel atmosphere (BC) • Aulanier filament models and BC Low filament models • Use potential field or MHD simulation, then add better coronal energy balance physics post-facto (Lundquist, Fisher, Alexander)

3. Hare & Hounds (cont’d) 2. Convert models to I(x,y,lam,pol) (Lin, Judge? Casini?, Gibson?) (15 Mar) • Collisions modifying pol signal • Projection • NRL (physical and intensity calculation)?

4. Hare & Hounds (cont’d) 3. Add telescope, compute data, analyze (15 Apr) • Kuhn (Solar-C) gallery of diff. structures • Penn (ATST) • Tomczyk (COMP)

5. Initiative on instrumental limitsleaders: Mickey, Penn Definitions: • Class 1 observations –use the instrument as a coronagraph (no magnetic information), look in continuum, see ne distribution • Class 2 observations – use the integrated IR coronal emission line to look at linear polarization (related to transverse field direction) and in total intensity – intensity defines where the corona is emitting in, e.g., FeXIII compared to all coronal plasma • Class 3 observations – Measure Zeeman splitting – resolve line profile and have high polarization sensitivity.

6. Initiative on instrumental limits (cont’d) • Action: a group of experimentalists (Penn, Mickey, H. Lin, & Kuhn) will quantify, for the Solar-C telescope, what spatial & temporal resolutions are practical & feasible for given sensitivities in each of the 3 classes of observation.

7. Initiative on Pioneering Coronal Magnetic Field msmts (Leaders:Kuhn, Lin, Mickey) • Primary Goal: Answer this question:Is there conclusive evidence for a flux rope in corona before eruption? If so, what is the field strength, twist, and length of the rope?

8. Initiative on Pioneering Coronal Magnetic Field msmts (cont’d) Observing plan for primary goal: • systematic measurement of the linear and circular polarization of long-lived prominences that cross both limbs of the Sun. Frequently, these are tilted w/r to azimuthal direction. Getting observations on both limbs allows for a possible reconstruction of the desired flux rope parameters. [H. Lin, Kuhn, Mickey] • Observe prominences in H with the IVM [Mickey, others?]

9. Initiative on Pioneering Coronal Magnetic Field msmts (cont’d) • Secondary observational goals: • Measure linear and circular polarizations in a helmet streamer • Look for polarization signatures of quasi-separatrix surfaces in the solar corona • Examine the polarization structure near a coronal hole-streamer boundary

10. Initiative on Pioneering Coronal Magnetic Field msmts (cont’d) • Long term goal: 3-d synoptic magnetic field maps of the large scale corona. This would be extremely valuable for comparison with large scale models of the corona (such as source-surface models). • Solar-C observations will provide a test bed of concepts for coronal observations from ATST

11. Initiative on the use of coronal magnetic field measurements in theoretical models (Leaders: Fisher, Roussev, Li) Observations with Solar-C that could test models of flux-rope like structures: (1) filament models (e.g. Aulanier) (2) flux rope models e.g. Roussev-Titov/Demoulin (3) analytic models of BC Low. Inverse versus normal filament topology (4) filament models that are not highly twisted - eg Dahlburg & Antiochos(??) Action: Get model originators to Identify the features of these models that would allow for observational discrimination

12. Initiative on the use of coronal magnetic field measurements in theoretical models (cont’d) Use coronal field measurements to test models of helmet-streamer and active region structures: (1) source-surface models (Li); (2) MHD solar-wind/helmet streamer models (Michigan, Ledvina, CISM efforts of Mikic & Linker) (3) active region models (Abbett/Fisher/Lundquist),

13. Other measurements to coordinate with coronal B measurements (leader – Hudson[?]) • TRACE (field lines) – develop algorithm for using xray images to reconstruct field line curves [Hudson??] • Coordinate obs. with UVCS to get T,n,v diagnostics to go along with the B msmts [Jing Li] • Radio msmts tie down field in active regions [BBSO? Owens Valley? Dale Gary?] • Energetic particle measurements [Hudson?] • Chromospheric vector magnetograms [Metcalf?? Leka??] Action item: Get confirmed leader for this initiative and finish identifying people who want to do these things.

14. Appendix: Measurement of prominence masses and geometries (leader – Hudson) Overview of techniques 1.1 H-alpha 1.2 EUV absorption 1.3 Thomson scattering 1.4 Micro/mm free-free emission 2. Characterization of masses 2.1 Quiescent prominences 2.2 Erupting prominences 2.3 Active-region prominences 3. Filament masses related to CMEs and flares 3.1 Statistics 3.2 Morphology 3.3 Transformation during eruption