Time-distance helioseismology pipeline generates subsurface maps of
horizontal flow velocities and wave-speed perturbation for the full-disk
Sun, and also for selected active regions. The maps are obtained for
8-hour intervals, and cover horizontal areas of 30° x 30° and 0 -- 20 Mm
Data Analysis Procedure:
The basic procedure for the time-dis
tance data-analysis pipeline is the following:
Track the HMI Dopplergrams with the differential rotation rate
(Snodgrass and Ulrich, 1990), and map the tracked areas into heliographic
coordinates using the Postel's projection. The tracked datacubes represent
3D arrays with dimensions of 512x512x640, with a 0.06° sampling horizontal
scale, and 45-second time cadence, covering 30° x 30° areas for continuous
8 hour intervals.
Phase-speed filtering procedure is then applied to the datacubes,
and acoustic travel times are calculated from the cross-correlation functions.
Two types of travel times are obtained using two different fitting
Gabor wavelet fitting (Duvall & Kosovichev, 1997)
Gizon-Birch (2002) fitting method.
Inversions of the travel-times are performed using the Multi-Channel
Deconvolution method, with two different sensitivity kernels employed:
ray-path approximation kernel
Thus, our products include two sets of acoustic
travel times and four sets of inversion results in both the flow-velocity
and wave-speed perturbation fields.
Available Data products
Full-disk Data Products
The travel times and inverted flow and wave-speed
perturbation maps are provided for 25 areas of 30x30 degrees covering
the full disk and processed independently. Each day is divided into
three 8-hr intervals: 00:00 -- 07:59UT, 08:00 -- 15:59UT, and 16:00
-- 23:59UT. The JSOC series of these data products are:
contains fitted travel times, with data segments 'gabor' from
Gabor wavelet fitting and 'GB' from Gizon-Birch defined travel
times. Users can download either one or both.
contains inversion results, with 'vx' for subsurface east-west
direction velocity, 'vy' for subsurface north-south direction
velocity, and 'cs' for subsurface wave-speed perturbations.
Keywords 'Gabor' and 'GizonBirch' define which
fitted travel times are used, and 'Born' and 'Raypath'
define which sensitivity kernels are used.
The full-disk flow and wave-perturbation maps are then obtained
by merging these 25 areas.