vfisv update and effects of the variation of hmi filter profiles on the inversions

VFISV update and effects of the variation of HMI

filter profiles on the inversions

R. Centeno and S. Tomczyk

Rebecca Centeno

SDO SWG meeting -- Sept 9, 2009

VFISV updateFilter profiles

HMI dataVFISV descriptionVFISV current status

Rebecca Centeno


• 5-6 spectral points

• 4-6 modulation states

• Cadence: ~90-120 seconds

• ~12-minute averages for magnetic field measurements(Borrero et al. 2007)

• 4096x4096 pixels

HMI data



Rebecca Centeno


Forward modeling: Milne-Eddington approximation with Zeeman-induced Stokes profiles

Filtering: Synthetic profiles are computed at high spectral resolution and then filtered with HMI’s filter profiles

Inversion: Levengberg-Marquardt iterative scheme tries to match synthetic Stokes profiles to observed data in a least-squares sense. Free parameters: , B, , , vLOS, 0, D, , B0, B1

VFISV

Borrero et al 2009



Rebecca Centeno


12500 inversions per second! But is straightforward parallelizable.

F90 inversion code has been thoroughly tested and is working fine.

Version 1.05 works with HMI-like data (actually filters Hinode SP Stokes data with HMI filter profiles and then inverts 6 point spectral lines).

Code has been implemented into pipeline (R. Bogart)Some issues with the C wrapper

VFISV


HMI filter profilesCharacterizationTest inversions

Rebecca Centeno


Filter profiles change across the FOV: amplitudes, integrated areas, shapes, side-lobes, spectral shifts.

Filter profiles variation across the FOV



Rebecca Centeno



This can have effects on the inversion results: velocity, magnetic field strength and topology…




Rebecca Centeno




We have to invert approx. 4096x4096 pixels every 10 minutes




Rebecca Centeno




We have to invert approx. 4096x4096 pixels every 10 minutes

We can’t afford to compute the filter profiles for each pixel!!




Rebecca Centeno



Is it reasonable to use a unique set of HMI filter profiles for all the pixels in the inversions?



Rebecca Centeno


Statistical properties: AMPLITUDES

Flatfielding will take care of the area differences among the filters



Rebecca Centeno


Statistical properties: SHIFTS

We expect the filter shifts to affect the retrieved velocities



Rebecca Centeno


Statistical properties: SKEWNESS

Differences in shapes could affect other quantities



Rebecca Centeno


Inversions

Hinode SPdata



Rebecca Centeno


Inversions

Hinode SPdata

HMI fakeStokes

64x64HMI filters



Rebecca Centeno


Inversions

Hinode SPdata

HMI fakeStokes

64x64HMI filters

central filters

correct filters

shifted central filters

3 inversions



Rebecca Centeno


Inversions

Hinode SPdata

HMI fakeStokes

64x64HMI filters

central filters

correct filters


3 inversions

Referenceresults

Residual differences




Rebecca Centeno


Inversions

Hinode SPdata

HMI fakeStokes

64x64HMI filters

central filters

correct filters


Referenceresults



Are they good enough?

3 inversions



Rebecca Centeno


Results

Inversion results for magnetic pixels: central filters

VL

OS

Mag

neti

c fi

eld

stre

ngth



Rebecca Centeno


Results

Inversion results for magnetic pixels: central filters

VL

OS

Mag

neti

c fi

eld

stre

ngth

Magnetic properties don’t notice the differences in

shapes, amplitudes and shifts of the filter profiles!!



Rebecca Centeno


Results

Inversion results for non-magnetic pixels: central filters

VL

OS

Mag

neti

c fi

eld

stre

ngth



Rebecca Centeno


Results

Inversion results for non-magnetic pixels: shifted central filters

VL

OS

Mag

neti

c fi

eld

stre

ngth



Rebecca Centeno


Results

Inversion results for non-magnetic pixels: shifted central filters

VL

OS

Mag

neti

c fi

eld

stre

ngth

Residual velocity differencesNOT due to filter shifts



Rebecca Centeno


Results

“Actual” vs. “central” filter profiles:



Rebecca Centeno


Results

Side-lobe imbalance not well accounted for

with central filters

“Actual” vs. “central” filter profiles:



Rebecca Centeno


Results

Filter profiles change across the FOV: amplitudes, integrated areas, shapes, side-lobes, spectral shifts. How does if affect the inversion results?

Changes in HMI filter profiles don’t affect retrieved magnetic properties

Bulk filter shifts affect velocities

Residual effects on velocities from side-lobe imbalance

Inversions CAN be carried out with one set of filter profilesBUT careful calibration for retrieved velocities is necessary!

vfisv update and effects of the variation of hmi filter profiles on the inversions

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