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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 3
Ann. Geophys., 22, 911–922, 2004
https://doi.org/10.5194/angeo-22-911-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 911–922, 2004
https://doi.org/10.5194/angeo-22-911-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  19 Mar 2004

19 Mar 2004

Radar Observations of 8.3-m scale equatorial spread F irregularities over Trivandrum

D. Tiwari1, A. K. Patra2, C. V. Devasia1, R. Sridharan1, N. Jyoti1, K. S. Viswanathan1, and K. S. V. Subbarao1 D. Tiwari et al.
  • 1Space Physics Laboratory, Vikram Sarabhai Space Center Trivandrum, 695022, India
  • 2National MST Radar Facility, Tirupati, 517502, India

Abstract. In this paper, we present observations of equatorial spread F (ESF) irregularities made using a newly installed 18MHz radar located at Trivandrum. We characterize the morphology and the spectral parameters of the 8.3-m ESF irregularities which are found to be remarkably different from that observed so extensively at the 3-m scale size. We also present statistical results of the irregularities in the form of percentage occurrence of the echoes and spectral parameters (SNR, Doppler velocity, Spectral width). The Doppler spectra are narrower, less structured and less variable in time as compared to those observed for 3-m scale size. We have never observed the ESF irregularity velocities to be supersonic here unlike those at Jicamarca, and the velocities are found to be within ±200ms–1. The spectral widths are found to be less than 150ms–1. Hence, the velocities and spectral width both are smaller than those reported for 3-m scale size. The velocities and spectral widths are further found to be much smaller than those of the American sector. These observations are compared with those reported elsewhere and discussed in the light of present understanding on the ESF irregularities at different wavelengths.

Key words. Ionoshphere (equatorial ionosphere, plasma waves and instabilities; ionospheric irregularities)

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