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  Global-Mode Analysis of Full-Disk Data from the Michelson Doppler Imager and the Helioseismic and Magnetic Imager

Larson, T., & Schou, J. (2018). Global-Mode Analysis of Full-Disk Data from the Michelson Doppler Imager and the Helioseismic and Magnetic Imager. Solar Physics, 293: 29. doi:10.1007/s11207-017-1201-5.

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 Creators:
Larson, TimothyP., Author
Schou, Jesper1, Author              
Affiliations:
1Department Solar and Stellar Interiors, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832287              

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Free keywords: Helioseismology, Observations, Oscillations, Solar
 MPIS_GROUPS: Solar and Stellar Interiors
 MPIS_PROJECTS: SDO: German Data Center
 MPIS_PROJECTS: SDO
 MPIS_PROJECTS: SOHO
 Abstract: Building upon our previous work, in which we analyzed smoothed and subsampled velocity data from the Michelson Doppler Imager (MDI), we extend our analysis to unsmoothed, full-resolution MDI data. We also present results from the Helioseismic and Magnetic Imager (HMI), in both full resolution and processed to be a proxy for the low-resolution MDI data. We find that the systematic errors that we saw previously, namely peaks in both the high-latitude rotation rate and the normalized residuals of odd a-coefficients, are almost entirely absent in the two full-resolution analyses. Furthermore, we find that both systematic errors seem to depend almost entirely on how the input images are apodized, rather than on resolution or smoothing. Using the full-resolution HMI data, we confirm our previous findings regarding the effect of using asymmetric profiles on mode parameters, and also find that they occasionally result in more stable fits. We also confirm our previous findings regarding discrepancies between 360-day and 72-day analyses. We further investigate a six-month period previously seen in f-mode frequency shifts using the low-resolution datasets, this time accounting for solar-cycle dependence using magnetic-field data. Both HMI and MDI saw prominent six-month signals in the frequency shifts, but we were surprised to discover that the strongest signal at that frequency occurred in the mode coverage for the low-resolution proxy. Finally, a comparison of mode parameters from HMI and MDI shows that the frequencies and a-coefficients agree closely, encouraging the concatenation of the two datasets.

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Language(s): eng - English
 Dates: 2018-03-052018
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1007/s11207-017-1201-5
 Degree: -

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Title: Solar Physics
  Other : Sol. Phys.
Source Genre: Journal
 Creator(s):
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Publ. Info: Dordrecht, Holland : Kluwer, etc.
Pages: - Volume / Issue: 293 Sequence Number: 29 Start / End Page: - Identifier: ISSN: 0038-0938
CoNE: https://pure.mpg.de/cone/journals/resource/954925445694