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Mapping active regions in the Far Side of the Sun using helioseismology

This article discusses the use of helioseismology to map active regions in the far side of the Sun. It covers topics such as prediction capability, calibration of far-side seismic holography signal, "far-side" imaging of the near side, and the connection between CMEs and flares.

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Mapping active regions in the Far Side of the Sun using helioseismology

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  1. Mapping active regions in the Far Side of the Sun using helioseismology I. González Hernández, F. Hill (1) C. Lindsey and D. Braun (2) (1) National Solar Observatory, Tucson, AZ (2) NorthWest Research Associates, Boulder, CO

  2. Contents • Helioseismic holography of the Far Side of the Sun: a quick review. • Prediction capability: NOAA10808 & NOAA10923 • Calibration of far-side seismic holography signal • “Far-side” imaging of the near side • CME and Flare connection • Conclusions and future work

  3. EARTH Pupil Courtesy of D. Braun Far Side Seismic Holography • 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.

  4. AR10808 Active Region NOAA-10923 Oct 31 -> Nov 10 2006 AR10923 sin(latitude) Prediction capability Active Region NOAA-10808 Aug 29 -> Sep 9 2005 sin(latitude) Carrington Longitude

  5. Calibrating the far-side signal

  6. Calibrating the far-side signal

  7. Calibrating the far-side signal

  8. Calibrating the far-side signal

  9. NOAA 10808 (far side) Braun & Lindsey 2001, ApJ, 560, L189 NOAA 10808 (near side) “far-side” imaging of the near side

  10. “far-side” imaging of the near side 1 x 3 skip method actually extends well onto the near side! can fill in some of this area with 1 x 4 skip method (in progress…)

  11. CME and Flare connection

  12. AR10806 AR10808 CME and Flare connection The left panel shows overlaid on the C2 LASCO image the front side of the Sun taken by the EIT instrument. The right panel shows the calculated farside map for that day as seeing from Earth perspective, i.e. looking directly through the Sun. ”….By 00:24 UT, signature of a huge and apparently backsided CME can be seen all above the E Limb (most likely related to Event #2). Though the timing seems to match that of the event from AR 10806, the event off limb is most probably from the back side of the Sun. In summary, the event as a whole can be determined as an asymmetric full halo CME. Several components contribute to the overall shape of the complex event, at least one of them frontsided, associated with a B-class X-ray flare on NOAA AR 10806. However, the bigger contribution seems to have its origins on the backside” (G. Stenborg, SOHO-LASCO Operations Scientist).

  13. using both far-side and near-side images to understand physics of phase-shifts/travel-times understanding physics can: • lead to better calibration of far-side signatures • lead to improved models of subsurface structure • lead to detection of emerging ARs travel-time pert. (sec) 2 mHz 3 mHz 4 mHz 5 mHz Braun & Birch 2007 (in prep.)

  14. Conclusions and future work • Space weather: • MDI and GONG pipelines are providing daily full-hemisphere farside maps. • Large active regions are seen in consecutive far-side maps. • Scientific Calibration • Empirical calibration: Statistics with far-side results +front-side analysis • Calibration of artificial “sunspots” • Calibrate effect of several bounces and dispersion relation • Ghost signature --> solar features? • Collaboration with irradiance variation studies

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