Far-side Imaging of Active Far-side Imaging of Active Regions: Latest DevelopmentsRegions: Latest Developments

Irene González Hernández and the GONG andHMI far-Irene González Hernández and the GONG andHMI far-side teamsside teams

National Solar Observatory, Tucson, AZNational Solar Observatory, Tucson, AZNorthwest Research Associates (CORA), Boulder, CONorthwest Research Associates (CORA), Boulder, CO

Stanford University, Stanford, CAStanford University, Stanford, CA

ContentsContents Introduction to far-side seismic holography

Improving the far-side maps

Calibrating the seismic signal

Success Rate

Variation of the mean phase with the solar cycle !

Improving the signal to noise

Future work and conclusions

Helioseismic Imaging of the Helioseismic Imaging of the FarsideFarside

Helioseismic imaging of sunspots at their antipodes. Lindsey, C. Helioseismic imaging of sunspots at their antipodes. Lindsey, C. & Braun, D.C, 1990, SoPh.& Braun, D.C, 1990, SoPh.

Seismic Images of the Far Side and Interior of the Sun Lindsey, Seismic Images of the Far Side and Interior of the Sun Lindsey, C. & Braun, D.C, 2000, Science.C. & Braun, D.C, 2000, Science.

Pupil

Helioseismic Imaging of the Helioseismic Imaging of the FarsideFarside

Phase of the Correlation

),,(),,(),,( tzHtzHdtzC rrr

Improving the far-side monitorImproving the far-side monitor

FS00543

85 %

MDI (HMI)

GONG

Time Distance ( HMI + GONG)

Users able to subscribe to alerts > %

|B|

Improving the far-side monitorImproving the far-side monitor

Detecting medium size active regions Reducing the noise by combining consecutive, non-overlapping maps

Calibrating in terms of magnetic field strength ( using the relationship found by Gonzalez Hernandez, Hill, Lindsey 2009, ApJ)

Removing the Solar Cycle variation as described by Gonzalez Hernandez, Scherrer and Hill (ApJ, 2010)

Confidence Level (…. Space Weather Journal, 2010)

Adding extra info on date of return and NOAA previous number if existed

Calibrating the far-side signalCalibrating the far-side signal

Calibrating the far-side signalCalibrating the far-side signal

González Hernández, I.; Hill, F.; Lindsey, C. Calibration of Seismic Signatures of Active

Regions on the Far Side of the Sun 2007ApJ...669.1382G

Confidence LevelConfidence Level

REFERENCESGonzález Hernández, I.; Scherrer, P.; Hill, F. A New Way to Infer Variations of the Seismic Solar Radius 2009ApJ...691L..87G <González Hernández, I.; Hill, F.; Lindsey, C. Calibration of Seismic Signatures of Active Regions on the Far Side of the Sun 2007ApJ...669.1382G Fontenla, J. M.; Quémerais, E.; González Hernández, I.; Lindsey, C.; Haberreiter, M Solar irradiance forecast and far-side imaging 2009AdSpR..

Pérez Hernández, F.; González Hernández, I.Green's Functions for Far-Side Seismic Images: A Polar-Expansion Approach 2010ApJ...711..853P

I. González Hernández, F. Hill, P. H. Scherrer, C. Lindsey, and D. C. BraunSpace Weather, 8, S06002, doi:10.1029/2009SW000560, 2010

New Calibrated Far-side mapsNew Calibrated Far-side maps

C. Long. Latitude Phase-shift Prob. Effective-Area Date-of-return Front-side-number 203.039993 -19.876875 -0.159418 87 84.239998

20100911 NOAA 11100

New Calibrated Far-side mapsNew Calibrated Far-side maps

Helioseismic far-side maps on the left and simultaneous STEREO behind observations of AR NOAA 11026 before it appeared on the front side of the Sun on September 21 2009

Further ImprovementsFurther Improvements Sensitivity variation with location !!Sensitivity variation with location !! Detecting smaller active regions (signal-to-Detecting smaller active regions (signal-to-

noise)noise) Duty cycleDuty cycle Hmi combinationHmi combination

Area estimationArea estimation Show current calibrationShow current calibration Talk about Effective areaTalk about Effective area Front side studyFront side study

Error estimationError estimation Integrated IndexIntegrated Index PolarityPolarity

““far-side” imaging of the near far-side” imaging of the near sideside

1 x 3 skip method actually extends well onto the near side!

Why the improvement?Why the improvement? Mean Phase --> Temporal VariationMean Phase --> Temporal Variation

Variation of the seismic solar Variation of the seismic solar radiusradius Solar acoustic radius variation --> solar cycle variationSolar acoustic radius variation --> solar cycle variation

Kholikov & Hill,

2008, SoPh

Far-side maps from time-Far-side maps from time-distacedistace

GONG

MDI

September 03 2005

Courtesy of Junwei Zhao

Seismic holographyTime distance

NOAA 10808

ArtifactsArtifacts Thomas Hartlep,Junwei Zhao Nagi N. Mansour, and Alexander G. Thomas Hartlep,Junwei Zhao Nagi N. Mansour, and Alexander G.

Kosovichev Kosovichev Validating Time-Distance Far-Side Imaging of Solar Validating Time-Distance Far-Side Imaging of Solar Active Regions through Numerical Simulations Active Regions through Numerical Simulations

ApJ, 689:1373–1378, 2008 December 20ApJ, 689:1373–1378, 2008 December 20

Why the improvement?Why the improvement?GONG MDI

060902

060903

060902

060903

The Farside Magnetic IndexThe Farside Magnetic Index

In collaboration with K. Jain, W. K. Tobiska and F. Hill

Comparison with front-side indexes:. The graphic below shows simultaneous observations of Ly-α (lasp.colorado.edu), F10

(www.ngdc.noaa.gov), the calculated Mount Wilson Sunspot Index (www.astro.ucla.edu) and the Far Side Magnetic Index. The sequence spans from October 2002 to December 2006. The different indexes have been scaled and shifted to aid the comparison.

Solar cycle variationSolar cycle variation

Can we improve the Green’s Functions?

More realistic model --> Collaboration with Fernando Pérez at the IAC

Empirical calibration of the dispersion

Dispersion for several bounces

Conclusions and Future workConclusions and Future work

MDI GONG

FS00543

85 %

Time Distance ( HMI + GONG)

Users able to subscribe to alerts > %

|B|

Improving the Maps

Calibration --> extending to the front side

Success Rate --> more accurate determination

Better Signal to Noise --> HMI data/ combination of ray paths / green’s functions / artifacts

Understanding Solar Cycle variations !!!