Nocturnal variations of F-region vertical ionization velocities near the magnetic equator

Abstract

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City" downloadurl="http://www.5iamas-microsoft-com:office:smarttags"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/"> F-region vertical plasma drifts at the magnetic equatorial station, Ibadan (7.4 °N, 3.9 °E; 6°S dip) are inferred from the time variation of the hourly-recorded ionosonde virtual height (<i style="">h'</i>F<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City" downloadurl="http://www.5iamas-microsoft-com:office:smarttags"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/">) of F-layer data; obtained during 1957/58 International Geophysical Year (IGY) period under geomagnetically quiet and disturbed nights. Prominent nocturnal vertical drift characteristics are presented at African longitudinal sector. Seasonal effects appeared to be pronounced during undisturbed and disturbed nighttime conditions. Also, pre-reversal peak velocity obviously varies considerably with season. In addition, pre-reversal peak velocity exhibits significant variability with 10.7 cm Solar Flux Index and average Zurich monthly sunspot numbers. Furthermore the threshold parameters, such as, <b style="">E</b> × <b style="">B</b> vertical drifts and virtual height (<i style="">h'</i>F) required to cause spread-F irregularities are determined to be approximately 30 m/s and 400 km, respectively. Results obtained by the authors are in good accord with those for other low-latitude regions that employ other observational techniques. There are several likely processes responsible for the quiet and disturbed times plasma drift variability in the night hours at equatorial regions. </smarttagtype></smarttagtype></smarttagtype></smarttagtype>