Advertisement Helioseismology Summer School August 24 – August 28, 2010 Beijing Normal University Contact: Prof. Shaolan Bi Lecture Language: Mandarin
HMI Routine Helioseismology Results that You Can Download and Use Junwei Zhao W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA94305-4085
Time-distance pipeline generates subsurface (up to 30Mm[?] below the photosphere) flow maps and sound-speed perturbation maps for the following two types: • Routine production: daily (nearly) full disk maps and synoptic maps • User selected areas (most likely, active regions)
1. Routine Production Input Every 8 hours, we select 480-minute Doppler observations and make time-distance measurements. Inversions are done to derive subsurface flow fields and sound-speed perturbations. A total of 25 areas are selected and used to generate full-disk subsurface map.
1. Routine Production Every 8 hours, we generate a nearly full-disk map. For every Carrington rotation, we generate a synoptic map, updated daily though.
2. User Designated Area Input output Users are free to select their interested active regions, and request a computation of cross-covariance or subsurface structures.
Tracking, Remapping, and Time-Distance Measurement Each of 25 areas is tracked with the Snodgrass rate at the center of the area, and each area has a dimension of 512x512x640 with a spatial sampling of 0.06o/pixel, and a temporal cadence of 45 sec. Phase-speed filtering is then applied. After time-distance measurement, the resultant dimension becomes 256x256 with 0.12o/pixel. annulus # phase speed (μHz/l) FWHM annulus range (deg) 1 3.40 1.00 0.54 – 0.78 2 4.00 1.00 0.78 – 1.02 3 4.90 1.25 1.08 – 1.32 4 6.592 2.149 1.44 – 1.80 5 8.342 1.351 1.92 – 2.40 6 9.288 1.173 2.40 – 2.88 7 10.822 1.895 3.12 – 3.84 8 12.792 2.046 4.08 – 4.80 9 14.852 2.075 5.04 – 6.00 10 17.002 2.223 6.24 – 7.68 11 19.133 2.03 7.68 – 9.12
Initial Results from HMI: Routine Production of Synoptic Maps
Map for Divergence (Supergranulation) Divergence computed from horizontal flow fields at the depth of 0-1 Mm. Positive regions represent positive divergence, i.e., supergranules.
Plenty of Supergranulation! Every 8 hours, we have full-disk supergranulation maps at different depths. The plentiful data will be very useful for supergranulation studies.
Divergence times Vorticity Horizontal component of divergence multiplying the vertical component of vorticity represents kinetic helicity, in some sense. This value has clear latitudinal dependence, and that is mainly caused by the Coriolis force.
Synoptic Flow Chart (Large Scale Flows) This flow chart displays large scale flows comparable to the ring-diagram analysis. The original flow map has 3000x1000 vectors, but this map only has 120x40 vectors. This rotation covers from May 19 to June 17, 2010.
Far-Side Active Region Imaging Pipeline (Largely Not Yet Ready)
Solar Far-Side Image from Helioseismic Holography The Sun is not transparent to light, but it is completely transparent to acoustic waves. However, it is not an easy thing to image the active regions in the far-side of the Sun. Lindsey & Braun, 2000, Science, 287, 1799 Figure courtesy: SOHO/MDI
To download data, go to page: http://jsoc.stanford.edu/ajax/lookdata.html