Far-side Imaging and ActivityFar-side Imaging and Activity

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

National Solar Observatory, Tucson, AZNational Solar Observatory, Tucson, AZStanford University, Stanford, CAStanford University, Stanford, CA

Northwest Research Associates (CORA), Boulder, CONorthwest Research Associates (CORA), Boulder, CO

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|

Calibrating the far-side signalCalibrating the far-side signal

Carrington Longitude

sin

(lati

tud

e)

Active Region NOAA-10808

Aug 29 -> Sep 9 2005AR108

08

Active Region NOAA-10923

Oct 31 -> Nov 10 2006

AR10923

sin

(lati

tud

e)

Calibrating the far-side signalCalibrating the far-side signal

Calibrating the far-side signalCalibrating the far-side signal

““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!

Success rateSuccess rate

MDI

MDI

+

GONG

GONG

Success RateSuccess Rate

Why the improvement?Why the improvement?

Different length Different length of time seriesof time series

Duty CycleDuty Cycle Phase correctionPhase correction Bad dataBad data

Why the improvement?Why the improvement? Phase CorrectionPhase Correction

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

Solar cycle variationSolar cycle variation Mean Phase --> Solar Cycle variation --> Solar acoustic Mean Phase --> Solar Cycle variation --> Solar acoustic

radius variation (??)radius variation (??)

Solar cycle variationSolar cycle variation Mean Phase --> Solar Cycle variation --> Solar acoustic Mean Phase --> Solar Cycle variation --> Solar acoustic

radius variation--> Localized to surface magnetic areas (?)radius variation--> Localized to surface magnetic areas (?)

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

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 !!!