The Latitudinal Extent of the Equatorial Anomaly,
GEOPHYSICS LAB (AFSC) HANSCOM AFB MA
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The latitudinal extent of the equatorial anomaly has been studied using a theoretical model of the ionosphere which incorporates measured values of vertical E x B drift at the earths magnetic equator. Realistic values of neutral winds are also included. The equatorial anomaly region, typically between plus and minus 20 degrees magnetic latitude, is that part of the world where the highest values of electron density and Total Electron Content, TEC, normally occur, and hence is very important to high frequency propagation and to trans-ionospheric propagation effects. During the daytime upward E x B drift at the magnetic equator drives the ionization across field lines to higher latitudes, causing crests in ionization to occur at approximately plus and minus 15 deg dip latitude. The latitude range over which the anomaly makes a significant difference in values of foF2 and TEC is calculated as a percent departure from the case with no equatorial electric field. Results from the model studies with different values of realistic electric fields show that the effects of the anomaly can be highly variable and widespread in latitude and local time.
- Atmospheric Physics