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A spatial and spectral maximum entropy method as applied to OVRO solar data

Komm, R. W. and Hurford, G. J. and Gary, D. E. (1997) A spatial and spectral maximum entropy method as applied to OVRO solar data. Astronomy and Astrophysics Supplement Series, 122 (1). pp. 181-192. ISSN 0365-0138. https://resolver.caltech.edu/CaltechAUTHORS:20180320-141352202

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Abstract

We present first results of applying a Maximum Entropy Method (MEM) algorithm that acts in both the spatial and spectral domains to data obtained with the frequency-agile solar interferometer at Owens Valley Radio Observatory (OVRO) taken at 45 frequencies in the range 1 – 18 GHz. The traditional MEM algorithm does not exploit the spatial information available at adjacent frequencies in the OVRO data, but rather applies separately to each frequency. We seek an algorithm that obtains a global solution to the visibilities in both the spatial and spectral domains. To simplify the development process, the algorithm is at present limited to the one-dimensional spatial case. We apply our 1-d algorithm to observations taken with the OVRO frequency-agile interferometer of active region AR 5417 near the solar limb on March 20, 1989 (vernal equinox). The interferometer's two 27 m antennas and 40 m antenna were arranged in a linear east-west array, which at the vernal equinox gives a good match to the 1-d algorithm. Our results show that including the spectral MEM term greatly improves the dynamic range of the reconstructed image compared with a reconstruction without using this information. The derived brightness temperature spectra show that for AR 5417 the dominant radio emission mechanism is thermal gyroresonance and we use this information to deduce the spatial variation of electron temperature and magnetic field strength in the corona above the active region.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1051/aas:1997300DOIArticle
https://aas.aanda.org/articles/aas/abs/1997/04/dst6554/dst6554.htmlPublisherArticle
Additional Information:© 1997 European Southern Observatory (ESO). Received: 23 September 1995; Accepted: 8 June 1996; Published online 15 April 1997. We thank Jay Bromley who did the initial programming as an undergraduate student at Caltech. This work was supported by NSF grants ATM-9311416 and AST-9314929, and NASA grant NAGW-4563 to the California Institute of Technology.
Funders:
Funding AgencyGrant Number
NSFATM-9311416
NSFAST-9314929
NASANAGW-4563
Subject Keywords:Sun: corona; Sun: magnetic fields; Sun: radio radiation; techniques: image processing; techniques: interferometric
Issue or Number:1
Record Number:CaltechAUTHORS:20180320-141352202
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180320-141352202
Official Citation:A spatial and spectral maximum entropy method as applied to OVRO solar data. R. W. Komm, G. J. Hurford and D. E. Gary. Astron. Astrophys. Suppl. Ser., 122 1 (1997) 181-192. DOI: https://doi.org/10.1051/aas:1997300
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85382
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:02 Apr 2018 20:59
Last Modified:03 Oct 2019 19:30

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