Evidence of short spatial variability of the equatorial electrojet at close longitudinal separation

The characteristics of longitudinal variability of equatorial electrojet (EEJ) and counter electrojet (CEJ), presented in this study, are based on concurrent observations from a hitherto unsampled region of the world to examine the (1) degree of correlation between hourly means and monthly averaged hourly means of ground observations with equatorial electrojet climatological model (EEJM-2.0), (2) day-to-day longitudinal variability of EEJ strength between the pairs of sites, and (3) longitudinal variability in occurrences of counter electrojet. The analyses are based on the data obtained from an observatory and three new remote sites in the northern Indian Ocean at a longitudinal separation of approximately 15 degrees: Hyderabad (HYB) and Vencode (VEN) at 77 degrees E and Port Blair (PBR) and Campbell Bay (CBY) at 93 degrees E, for a period of 4 months during Lloyd's D-season (November 2011 to February 2012) and comparison with the EEJM-2.0 based on CHAMP satellite data. At both longitudes, the overall correlation of monthly mean hourly values (i.e., from 05: 00 to 19: 00 LT) between the observed EEJ strength and modeled current density from EEJM-2.0 is good (r > 0.8). However, a significant lack of correlation is witnessed on day-to-day peak values (i.e., 12: 00 LT) between the observed variations and the model at both sites. Further, a comparison of noontime peaks between the two sites shows a considerable day-to-day variability. A large number of CEJs (43 events) are recorded during the study: at CBY (15 events) and VEN (28 events). Analyses of the CEJ events highlight the variability of CEJ phenomena in terms of amplitude, dates, and time of occurrence over 15 degrees longitude separation. The local nature of perturbations causing CEJ is evident; the possible factors are being non-migrating eastward and westward propagating diurnal tides and local meteorological phenomena associated with upper mesospheric temperature, wind, and density variations.