March 2013
You can find here tables of mode frequencies, line-widths,
asymmetries and amplitudes, resulting from fitting full-disk data,
for l=100 to l=1000 (or 900) resulting from ridge fitting, corrected to
produce mode estimates.
I have now fitted three instruments (MDI, GONG and HMI) for three
Dynamics epochs:
The exact same epochs were fitted for each instrument for each year, as
determined by MDI's full-disk images availability, only the fill factor is different.
The following files explain the formats, or hold IDL routines:
- multiplets.txt: description of format and content of multiplets.dat
- cg-coefs.txt: description of format and content of cg-coefs.dat
- singlets.txt: description of format and content of singlets.dat
- routines.sav: my IDL routines, as a save set, needed for reproducing the plots,
including read_struct(), that can be used to read the .dat files.
- plot-multiplets.pro: IDL routine to plot multiplets.dat
- plot-cg-coefs.pro: IDL routine to plot cg-coefs.dat
A paper, in preparation, will describe these results. Despite my best efforts,
results from co-eval observations using different instruments (and different
but appropriate leakage matrices) do not produce the exact same results.
Comparisons of the co-eval results, for frequencies and CG coefs, are in the
following PDF files:
- compare-2002-frq.pdf: MDI & GONG 2002 frequencies
- compare-2002-cgs.pdf: MDI & GONG 2002 CG coefs
- compare-2002-cgs-raw.pdf: MDI & GONG 2002 raw (uncorected) CG coefs
- compare-2010-frq.pdf: MDI, GONG & HMI 2010 frequencies
- compare-2010-cgs.pdf: MDI, GONG & HMI 2010 CG coefs
- compare-2010-cgs-raw.pdf: MDI, GONG & HMI 2010 raw (uncorected) CG coefs
In each subdirectory, the tables are in the following files:
- multiplets.dat: Table of multiplets (l, n), after fitting CG
coefs to the singlets.
- multiplets-xx-yyyy.pdf: resulting plot.
- cg-coefs-xx-yyyy.dat: Table of Clebsch-Gordan coefficients
- cg-coefs-xx-yyyy.pdf: resulting plot.
- singlets-xx-yyyy.dat.gz: Table of singlets (l,n,m), some 5.2 million
modes, for all azimuthal orders and all degrees from l=100 to l=1000 (gzip compressed file).
where xx-yyyy corresponds to intrument and year (like mdi-2001).
NOTE that the dots in some of the PDF plots "disappear" at some zoom
level(s) when viewing them with acroread - zoom in or out to see them. |
The paper,
published in the ApJ
and available at astro-ph, that describes the methodology used
to produce these tables:
Accurate Characterization of High-Degree Modes Using MDI Observations
S.G. Korzennik(1), M.C. Rabello-Soares(2,3),
J. Schou(2) and T.P. Larson(2)
(1) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA
(2) W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA
(3) now at Universidade Federal de Minas Gerais, Physics Department, Minas Gerais, Brazil
ABSTRACT
We present the first accurate characterization of high-degree modes,
derived using the best MDI full-disk full-resolution data set available. A
ninety day long time series of full-disk two arc-second per pixel resolution
dopplergrams was acquired in 2001, thanks to the high rate telemetry provided
by the Deep Space Network. These dopplergrams were spatially decomposed using
our best estimate of the image scale and the known components of MDI's image
distortion. A multi-taper power spectrum estimator was used to generate
power spectra for all degrees and all azimuthal orders, up to l = 1000. We
used a large number of tapers to reduce the realization noise, since at high
degrees the individual modes blend into ridges and thus there is no reason to
preserve a high spectral resolution. These power spectra were fitted for all
degrees and all azimuthal orders, between l = 100 and l = 1000, and for all
the orders with substantial amplitude. This fitting generated in excess of
5.2×10^6 individual estimates of ridge frequencies, line-widths, amplitudes
and asymmetries (singlets), corresponding to some 5,700 multiplets (l,
n). Fitting at high degrees generates ridge characteristics, characteristics
that do not correspond to the underlying mode characteristics. We used a
sophisticated forward modeling to recover the best possible estimate of the
underlying mode characteristics (mode frequencies, as well as line-widths,
amplitudes and asymmetries). We describe in detail this modeling and its
validation. The modeling has been extensively reviewed and refined, by
including an iterative process to improve its input parameters to better
match the observations. Also, the contribution of the leakage matrix on the
accuracy of the procedure has been carefully assessed. We present the derived
set of corrected mode characteristics, that includes not only frequencies,
but line widths, asymmetries and amplitudes. We present and discuss their
uncertainties and the precision of the ridge to mode correction schemes,
through a detailed assessment of the sensitivity of the model to its input
set. The precision of the ridge to mode correction is indicative of any
possible residual systematic biases in the inferred mode characteristics. In
our conclusions, we address how to further improve these estimates, and the
implications for other data sets, like GONG+ and HMI.
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