Astron. Astrophys. 348, 627-635 (1999)

Power spectra comparison between GOLF and spatially masked MDI velocity signals

C.J. Henney ¹, R.K. Ulrich ¹, L. Bertello ¹, R.S. Bogart ², R.I. Bush ², P.H. Scherrer ², T. Roca Cortés ³ and S. Turck-Chièze <sup>4

1</sup> Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1562, USA
² Stanford University, CSSA-HEPL, Stanford, CA 94305-4085, USA
³ Instituto de Astrofísica de Canarias, Departamento de Astrofisica, U. de La Laguna, E-38200 La Laguna, Spain
⁴ Service d'Astrophysique, DSM/DAPNIA, CE Saclay, F-91191 Gif-sur-Yvette, France

Received 19 April 1999 / Accepted 9 June 1999

Abstract

The Global Oscillations at Low Frequency (GOLF) and the Michelson Doppler Imager (MDI) instruments aboard the Solar and Heliospheric Observatory (SOHO) give an excellent opportunity to search for solar low frequency oscillation modes previously undetected from ground based experiments. Presented here is a comparison of the velocity power spectra between the two instruments. In addition, this paper outlines work towards creating a GOLF-simulated signal utilizing MDI velocity images. The simulation of the GOLF signal is achieved by integrating spatially weighted masks with MDI full-disk Doppler images. The GOLF-simulated signal and a selection of additional spatially masked MDI velocity signals are compared with the observed GOLF signal for a 759 day period from May 25, 1996 through June 22, 1998. Ultimately, a cross-analysis process between GOLF and MDI signals could lead to an enhancement of our ability to detect low frequency solar oscillations. For low degree () and low frequency acoustic modes, the signal-to-background ratio between GOLF and the spatially masked MDI velocity data is compared here.

Key words: Sun: atmosphere Sun: oscillations

Send offprint requests to: C.J. Henney

Correspondence to: henney@astro.ucla.edu

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. The GOLF signal
  • 2.1. The GOLF velocity response
• 3. Integrated full-disk MDI velocity signal
  • 3.1. Modeling the GOLF signal
  • 3.2. Additional spatial masks
  • 3.3. Power spectra fitting
• 4. Results and discussion
  • 4.1. Power spectra comparison
  • 4.2. Signal-to-background comparison
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: July 26, 1999
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