COSMO-LC Data Analysis and Interpretation
Magnetometry PRODUCTS and TOOLS
Sarah Gibson
Enrico Landi, Steven Tomczyk, Joan Burkepile, Roberto Casini Brandon Larson, Scott Sewell, Alfred de Wijn
National Center for Atmospheric Research
Why do we need COSMO?
Courtesy Merkin, Lyon, Wiltberger
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To observe the magneto thermal environment of the solar corona:the source of space weather
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If we ever want to predict Bz at the Earth, we need to be able to quantify the global coronal magnetic fieldCOSMO-LC: Magnetically-sensitive measurements
2145_HMI_THERMO_MED_H2.dat White light PB
-2 -1 0 1 2
(Y_pos Rsun) UNITS: 10^-8 Bsun LOG -2 -1 0 1 2 (Z_pos Rsun) -2.4 -1.7 -0.90 -0.15 0.60 1.4 2.1
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Coronal forbidden lines emission arises from both collisional excitation (~N2) and resonance scattering from anisotropic radiation (~N)•
Sensitive to Zeeman and saturated Hanle effectso
COSMO-LC Level 1: Stokes I, Q, U, V
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ΘB = magnetic inclination along line of sight•
ΦB = magnetic azimuth in plane of sky•
ϑB = angle between B and solar localvertical
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σ (alignment) goes through zero andchanges sign at van Vleck angle 54.74:
1-3cos2(ϑB)=0
5
Lin et al., 2004
COSMO-LC Level 2 products: B
LOS•
Quantitative measure of magnetic field strength•
Weighted integral along LOS (similar to pB)•
BLOS maps: plane of sky, Carrington, solar cycleCourtesy Joan Burkepile
COSMO-LC Level 2 products: Azimuth
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Measures POS magnetic direction (with 90 degree flip when crosses V. Vleck angle)•
Quantifies expansion of flux tubes (significant to solar wind acceleration)CoMP I with polarization vectors CoMP Azimuth - black=radial; blue=clockwise tilt; red=counterclock tilt
COSMO-LC Level 2 products: Degree of polarization
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Example: coronal cavities, can be stable for multiple days, but ultimately CME•
Coronal cavities well-modeled by magnetic flux ropes•
Line-of-sight alignment minimizes projection issues•
Degree of polarization (+ azimuth) good diagnostic of magnetic topologyCoMP P
NLFFF extrapolation with flux insertion SXR Sigmoid
Linear polarization lagomorph
in coronal cavity Flux rope model forward-integrated for linear polarization
Savcheva et al., 2012
Bak-Steslicka et al., 2013
cavity center
Model P Bak-Steslicka et al., 2013
9 Rachmeler et al., 2014 CoMP degree of polarization (greyscale) and polarization vectors/ AIA 193
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Pseudostreamers:
characteristic
signature in
linear
polarization
COSMO-LC Level 2 products: Doppler velocity
Tian et al., 2013 Bak-Steslicka et al., 2013
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CMEs and CME
precursors
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Magnetic flux
COSMO-LC Level 2 products: Waves
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Ubiquitous waves in Doppler velocity
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Products: phase speed, direction of propagation, damping
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Constrains B
POSand POS direction; heating/wind models
Tomczyk et al. 2007 Morton et al. 2015
White light pB PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 dataFe XIII Intensity PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 dataDegree of polarization Fe XIII PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 dataAzimuth Fe XIII
PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 dataBLOS Fe XIII
PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 dataBLOS Fe XIV
PSI MAS
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Given plasma/magnetic fields synthesizes multi-λ observables•
Works with any analytic or numerical model•
Applies CLE code of Judge & Casini for visible/IR polarimetry•
Can generate synthetic COSMO Level-2 data•
Can add photon noise to telescope specificationsCOSMO-LC Tools: FORWARD SolarSoft IDL package
5 minute integration of circular polarization for Fe XIII
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Can help validate/choose between modelsCOSMO-LC Tools: FORWARD SolarSoft IDL package
CoMP MAS
COSMO-LC Tools: FORWARD SolarSoft IDL package
Dis$nguishing)between)models)
Flux)rope) Sheared)arcade) Spheromak) L/I) L/I) L/I) V/I) V/I) V/I) Rachmeler)et)al.,)2013)COSMO-LC Tools: From FORWARD to inverse
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Local source (e.g. loop)•
Methods for vector B inversion developed using circular and linearpolarization measurements and solar rotation (Kramar et al., 2006; 2013)
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Assumes minimal evolution on solar time scales; apply solenoidal condition as regularization term; line-of-sight photospheric magnetic field required as boundary condition (initial condition, e.g. potential)•
Non-local methods: tomography•
Using Fe XIII 1074.7 and 1079.9 nm data, analytic solution for vector B (Plowman 2014)Line%of%sight,field, Linear,polariza4on,
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Can vary model parameters and examine e.g. how currents affect linear polarization signal:forward fitting
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Forward fittingInterpolated χ2surface
COSMO-LC Tools: COSMO data incorporation methods
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MHD-model based approach to forward-fitting the global field(NCAR-CfA collaboration — DOC-FM)
Initial guess global magnetic field
Generate synthetic observables
Model Data
Add currents (flux-‐rope
insertion) where don’t match
Solve for best fit parameters (location, orientation, strength, height of ropes).
Real χ2surface
COSMO-LC Tools: Community test-beds
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3D representations of plasma and magnetic field (ground truth)•
Forward-modeled multi-wavelength synthetic observables•
For developing/testing inversion/data-incorporation techniques inadvance of COSMO pB EUV (211) Stokes V (100MHz) Stokes V (10747 A)
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Quiescent filament flux rope with thermodynamics - FanCOSMO-LC Tools: Community test-beds
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3D representations of plasma and magnetic field (ground truth)•
Forward-modeled multi-wavelength synthetic observables•
For developing/testing inversion/data-incorporation techniques inadvance of COSMO
pB
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Global model with quiescent filaments (Mackay/Yeates/ Dalmasse)COSMO-LC Tools: Community test-beds
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3D representations of plasma and magnetic field (ground truth)•
Forward-modeled multi-wavelength synthetic observables•
For developing/testing inversion/data-incorporation techniques inadvance of COSMO
pB
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Active region simulation (Rempel)Conclusions
COSMO-LC will be an unprecedented resource for reconstructing the global coronal magnetic field
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BLOS maps (quantify coronal magnetic field strength)•
Azimuth and degree of polarization (POS direction/flux-tube expansion; magnetic topological diagnostic)•
Doppler velocity (magnetic flux surfaces; waves - phase speed, direction of propagation, damping)We are developing tools to maximize effectiveness of COSMO data
