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 !!!