Abstract:
This paper reports the statistical analysis of zonal drift velocity of equatorial plasma bubbles
(EPBs) inferred from advanced optical technique (all-sky imager) with OI 630.0-nm airglow emission from
January to April of 2011 to 2013. Over 143 nights of observations have been carried out using all-sky imager
over low-latitude station Kolhapur (16.8°N, 74.2°E; 10.6°N dip latitude), out of which 58 nights showed
signatures of EPBs. We study the hourly, monthly, and seasonal variation in zonal drift velocity of EPBs. Also,
the magnetically disturbed nights (Ap > 18) are separately studied. It is observed that (a) the daily peak zonal
drift velocity is seen to be positively correlated to corresponding daily averaged 10.7-cm solar flux. (b) The
zonal drift velocity is found to be larger in the equinox months than that of winter months. (c) During the
disturbed nights the zonal drift velocity gets slower and one of the disturbed nights showed the latitudinal
variation in zonal drift velocity during the development phase of EPBs before midnight hours. We suggest
that this variation might be occurred due to the disturbance dynamo electric fields at low latitude, which
reduces the EPBs’ eastward velocity. (d) The zonal drift velocity of EPBs presented in this paper is in good
agreement with the previous studies as well as the HWM-07 model values.
