Abstract
Abstract. We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE) in ExB drift, the asymmetry (Ia) of equatorial ionization anomaly (EIA), and the magnetic activity (Kp) on the generation of equatorial spread F (ESF). Results show that the ESF appears frequently in summer (November, December, January, and February) and equinoctial (March, April, September, and October) months, but rarely in winter (May, June, July, and August) months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s) and smaller |Ia| (<0.3) in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3) and disturbed (Kp≥3) conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.
Highlights
Over the past quarter century, the European Incoherent Scatter (EISCAT) radar has become well established as a tool for observing the ionosphere, both above and below the F2 peak, and is capable of measuring a wide range of ionospheric parameters
The results demonstrate that GPS imaging is capable of locating the main trough, and confirm the potential of MIDAS imaging as a tool for routine monitoring of the ionosphere
The MIDAS inversions result in one-hour movies of the three-dimensional distribution of electron concentration
Summary
Over the past quarter century, the European Incoherent Scatter (EISCAT) radar has become well established as a tool for observing the ionosphere, both above and below the F2 peak, and is capable of measuring a wide range of ionospheric parameters. Good spatial resolution can be obtained owing to the narrow beam pattern of the antenna, which is large in relation to the radio wavelength (Hargreaves, 1992). Beynon and Williams (1978) present a discussion on the early history and development of incoherent scatter radar, and an exCorrespondence to: R. Meggs et al.: Simultaneous observations of the main trough o
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