Session 10

SHINE Workshop, June 23-27, 2008

Vector Magnetic Data Input into

Global Models (Session 10) Chairs: Marc DeRosa and Ilia Roussev

Working Group Summary

Coming soon from SDO/HMI: vector B, full-disk high-cadence, from space, continuously.... What are you going to do with it???

Session 10

SHINE Workshop, June 23-27, 2008

Vector Magnetic Data Input into Global Models (Session 10)

Speaker Summaries

Steve Tomczyk (HAO)“Vector Magnetic Fields from the Helioseismic and Magnetic Imager (HMI) Instrument”

HMI will take 6 narrow-band filtergram images (4096x4096 pixels), inverted to produce vector data every 10 min

Disambiguated magnetograms produced every 3 hr, but on selected patches every 10 min

Observables: total flux density, filling factor, and uncertainty estimates

Haosheng Lin (IfA)“Observational Test of Potential Coronal Magnetic Field Model”

Gets plane-of-sky vector magnetograms off limb using SOLARC at Haleakala

LOS degeneracy can be resolved

For a 2007 case study, measurements agree with potential extrapolation

Incomplete knowledge of plasma properties in the corona precludes accurate forward modeling of polarization signals (maybe modelers can provide useful test cases?)

Session 10

SHINE Workshop, June 23-27, 2008

Vector Magnetic Data Input into Global Models (Session 10)

Speaker Summaries

Yang Liu (Stanford)“SOHO/MDI Level 1.8 Magnetograms”

MDI magnetograms corrected for zero-point variations, underestimation of flux densities, saturation effects, and cosmic ray hits

Remaining issues: non-uniform noise level across disk, magnetic field polarity reversal during major flares

K.D. Leka (CoRA)“Introduction to Using Full-Disk Vector Field Data for the SHINE Community”

Tutorial describing various vector magnetograms currently available or soon-to-be available (IVM, SOLIS+GONG, Hinode/SOT, SDO/HMI)

Issues include: averaging polarization signal vs inverted magnetograms, non-LTE effects in inversion, different disambiguation schemes, visualization of vector B.

Resolutions to many of these issues depends on how you want to use the vector magnetogram data!

Session 10

SHINE Workshop, June 23-27, 2008

Vector Magnetic Data Input into Global Models (Session 10)

Discussion Summary

Specific terminology (magnetic flux density vs. field strength, Mx/cm2 vs. Gauss, transverse vs. horizontal components of B, LOS vs. vertical/radial components of B)

Utility of B for various types of field extrapolations:

Potential: good initial estimate, commonly used for global models

Force-free, MHD: more computationally intensive, but more physically realistic (maybe hybrid models are most useful?)

Is a force-free or magnetostatic model for low corona even appropriate given observed dynamics in the chromosphere?

In any case, force-free and MHD models rely on well constructed vector magnetogram data and uncertainty estimates

This is only the beginning! Send us (Ilia or Marc) your feedback as to what you want to hear about in future SHINEs!