Farside Helioseismic Holography: Recent Advances I. González Hernández (1), D. Braun (2), S. M. Hanasoge(3), F. Hill (1), C. Lindsey (2), P. Scherrer (3) (1) National Solar Observatory, Tucson, AZ (2) NorthWest Research Associates, Boulder, CO (3) Stanford University, Stanford, CA

Contents Seismic imaging or Helioseismic holography Seismic imaging or Helioseismic holography Data: GONG near-real-time velocity images Data: GONG near-real-time velocity images Prediction capability: NOAA Prediction capability: NOAA Calibration of farside seismic holography signal Calibration of farside seismic holography signal Collaborations Collaborations Conclusions and future work Conclusions and future work

Helioseismic Imaging of the Farside Helioseismic imaging of sunspots at their antipodes. Lindsey, C. & Braun, D.C, 1990, SoPh. Helioseismic imaging of sunspots at their antipodes. Lindsey, C. & Braun, D.C, 1990, SoPh. Seismic Images of the Far Side and Interior of the Sun Lindsey, C. & Braun, D.C, 2000, Science. Seismic Images of the Far Side and Interior of the Sun Lindsey, C. & Braun, D.C, 2000, Science. Egression/Ingression Pupil

Helioseismic Imaging of the Farside Phase of the Correlation Phase-difference due to:  Reduction of gas pressure in magnetic region  displacement of density variation  “Acoustic Wilson depression”  Sound speed enhancement (evidence from acoustic moats) due to thermal anomalies  Inclination of the magnetic field

GONG farside map (Sep ) Helioseismic Imaging of the Farside Longitude-Sin(lat) projection

GONG near-real-time data Continuous stream of velocity images Continuous stream of velocity images Quick calibration done at the sites Quick calibration done at the sites 215x215 Gaussian-smoothed velocity images 215x215 Gaussian-smoothed velocity images Transfer daily from six GONG stations Transfer daily from six GONG stations Images merged in Tucson Images merged in Tucson Farside maps calculated from 1440-min data series twice daily. Farside maps calculated from 1440-min data series twice daily. Maps calculated approx. 12 hours after the last image has been taken. Maps calculated approx. 12 hours after the last image has been taken. Recalculated if the duty-cycle increases due to extra transfer. Recalculated if the duty-cycle increases due to extra transfer. Full-hemisphere farside maps. Full-hemisphere farside maps.

Prediction capability Carrington Longitude sin(latitude) Active Region NOAA Aug 29  Sep (GONG) Sept AR10808 Source: MLSO K-coronameter

Magnetic calibration Analysis of particular cases. Analysis of particular cases. Location Location Classification Classification Evolution of magnetic regions/sunspots Evolution of magnetic regions/sunspots Frontside holography  Relate phase-shifts calculated by seismic imaging with magnetic index on the visible sun. Frontside holography  Relate phase-shifts calculated by seismic imaging with magnetic index on the visible sun. Statistics, statistics: Statistics, statistics: GONG++ July 2001  present GONG++ July 2001  present Use Artificial data to calibrate the effect on the farside signal of different anomalies Use Artificial data to calibrate the effect on the farside signal of different anomalies Φ  B

Calibrating the farside signal

Source: Area(max)NSpots(max)Hale/McIntoshLocation FS region NOAA βγδ / Ekc βγδ / EkcN04W29FS5700 NOAA βγδ / Fkc βγδ / FkcS17W63FS5701 NOAA β / Dao β / DaoN12W22 NOAA βγδ / Fkc βγδ / FkcN08W69FS5702 NOAA β / Dso β / DsoS22W48 NOAA βγδ / Dki βγδ / DkiN03W32FS5703 NOAA β / Dso β / DsoS02W01 NOAA β / Dao β / DaoS08W20

Calibrating the farside signal Source: Area(max)NSpots(max)Hale/McIntoshLocation FS region NOAA βγδ / Ekc βγδ / EkcN04W29FS5700 NOAA βγδ / Fkc βγδ / FkcS17W63FS5701 NOAA β / Dao β / DaoN12W22 NOAA βγδ / Fkc βγδ / FkcN08W69FS5702 NOAA β / Dso β / DsoS22W48 NOAA βγδ / Dki βγδ / DkiN03W32FS5703 NOAA β / Dso β / DsoS02W01 NOAA β / Dao β / DaoS08W20

Magnetic calibration Phase differences calculated for the farside maps using 2.5 years of GONG++ data versus latitude (from August 2001 to December 2003, left). The crosses represent the value of each pixel versus the latitude position in the map. On the right panel, the magnetic flux of the synoptic maps (Kitt Peak) from the same period. Both panels show a greater concentration of magnetic activity in the southern hemisphere as well as major peaks surrounding the 15° latitudes. It is also noticeable that strong features appear closer to the Equator, possibly corresponding to activity at the latest phase of the solar cycle.

Magnetic calibration Histograms of phase difference (from farside maps, left) and magnetic index (Kitt Peak magnetograms, right) versus latitude. The data used span from July 2001 to August The histograms in both cases seem to agree on the presence of more magnetic activity in the southern hemisphere for this period of time.

Magnetic calibration Evolution of the number of FS Active region from July 2001 to August 2005

Magnetic Calibration Scatter plots of phase-shifts from the synoptic maps constructed from farside calculated images (Carrington Rotation 1996, left, and 2009, right) versus the square of the magnetic flux of the frontside synoptic maps from magnetograms (Kitt Peak)

Magnetic Calibration Artificial data with simulated “sunspot” Angular size: 25 –40 degrees Angular size: 25 –40 degrees Radial extend: 1Mm Radial extend: 1Mm Sound speed perturbation: Increase ~10% on average. Sound speed perturbation: Increase ~10% on average.

Bright green  plage (?)  faculae Dark red  penumbra Bright red  umbra Background blue  quiet Light Blue  faint Black  network Dark green  active network Irradiance Variation Courtesy of Juan Fontenla

Conclusions and future work MDI and GONG pipelines are providing daily full-hemisphere farside maps. MDI and GONG pipelines are providing daily full-hemisphere farside maps. Large active regions are seen in consecutive farside maps. Large active regions are seen in consecutive farside maps. Scientific Calibration Scientific Calibration Empirical calibration: Statistics with farside results +frontside analysis Empirical calibration: Statistics with farside results +frontside analysis Calibration of artificial “sunspots” Calibration of artificial “sunspots” Calibrate effect of several bounces and dispersion relation Calibrate effect of several bounces and dispersion relation Ghost signature (?) Ghost signature (?) Collaboration with irradiance variation studies Collaboration with irradiance variation studies Continue refining the technique to improve its capability as a space weather prediction tool Continue refining the technique to improve its capability as a space weather prediction tool