Nocturnal E-region Climatology Studies using Incoherent Scatter Radar Observations from Arecibo Observatory

Abstract:

The incoherent scatter radar (ISR) at Arecibo probes the ionospheric region of the Earth's atmosphere. It provides information about electron densities starting from about 85 - 90 km. One of the interesting features is the occurrence of Sporadic E, a phenomenon that is characterized by strong electron concentrations, and is related to the wind shear in the atmosphere. In this project we are evaluating the climatology of the nocturnal E region based on the computed E-region Total Electron Content (ErTEC) below 150km. For this, we considered seasonal variation, solar activity, and geomagnetic disturbances. We have analyzed 120 days of data covering the nocturnal E region altitudes (below 150km) from 1986 to 1999. As a conclusion, in the midnight period the ErTEC values are lower during high solar flux in all the seasons except for summertime; it responds differently to solar flux. Results also show high electron density during winter, only at sunset and sunrise. In terms of geomagnetic conditions, summer has a very low percentage of variation for geomagnetic activity while Equinox period display strong variability between ErTEC values during high and low solar activity periods due to geomagnetic disturbances. In addition, winter time exhibits decreasing of ErTEC with the increase of geomagnetic condition independently of the solar activity.