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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 8
Ann. Geophys., 20, 1203–1212, 2002
https://doi.org/10.5194/angeo-20-1203-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 20, 1203–1212, 2002
https://doi.org/10.5194/angeo-20-1203-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Aug 2002

31 Aug 2002

Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar

J. L. Chau2,1, R. F. Woodman1, and L. A. Flores2 J. L. Chau et al.
  • 1Radio Observatorio de Jicamarca, Instituto Geofísico del Perú, Lima, Perú
  • 2Laboratorio de Física, Universidad de Piura, Piura, Perú
  • Correspondence to: J. L. Chau (chau@geo.igp.gob.pe), Perú

Abstract. We present a summary of the statistical characteristics of echoes from ionospheric (E- and F-region) field-aligned irregularities obtained with the Piura VHF radar. This radar is located at ~ 7.0° dip latitude, just outside the equatorial electrojet (EEJ) region. Our results are based on (1) intermittent observations made between 1991 and 1999 just few days a year, and (2) continuous observations made between January 2000 and June 2001. During most of the intermittent observations, simultaneous measurements of EEJ and equatorial spread F (ESF) irregularities were performed with the Jicamarca VHF radar. From the continuous measurements, we have obtained the diurnal and seasonal characteristics of a variety of parameters (percentage of occurrence, signal-to-noise ratio and/or Doppler velocities) from the lower and upper E-region irregularities and also from F-region irregularities over Piura. For example, we have found that (1) the E-region echoes are stronger and occur more frequently during local summer (i.e. between December and March); (2) between May and June, the E-region echoes are weaker and occur less frequently; moreover, during these months, a semidiurnal wave with large amplitudes is observed in the meridional wind (> 100 ms- 1); (3) there is vertical wavelength of about 20 km in the Doppler velocity, particularly after midnight; (4) the lower (upper) E-region Doppler velocities are influenced mainly by meridional winds (equatorial F-region vertical drifts). In addition, we have observed that the seasonal and daily occurrences of Piura F-region irregularities are similar to the occurrence of topside ESF irregularities over Jicamarca. The likelihood of occurrence of F-region irregularities over Piura and, therefore, topside ESF over Jicamarca is greater when there are no E-region irregularities over Piura. On the other hand, there is more probability of observing bottomtype/bottomside ESF irregularities over Jicamarca when E-region irregularities are observed over Piura.

Key words. Ionosphere (ionospheric irregularities; equatorial ionosphere; instruments and techniques)

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