Constraints on Scale Lengths of Equatorial Electrojet and Counter Electrojet Phenomena From the Indian Sector

Abstract

The present study investigates the longitudinal variability of equatorial electrojet (EEJ) and counter electrojet (CEJ) phenomena using concurrent data from three equatorial and low‐latitude paired stations/sites at 5°, 15°, and 20° longitudinal separation in the Indian sector: (i) Minicoy (72°E, dip latitude 01.32°) and Alibag (72°E, dip latitude 14.06°), (ii) Vencode (77°E, dip latitude 01.02°) and Hyderabad (77°E, dip latitude12.34°), and (iii) Campbell Bay (93°E, dip latitude −0.79°) and Nabagram (93°E, dip latitude 06.79°). The observations, over a period of 12 months, at 72°E and 77°E, and 10 months at 93°E, for the year 2015, reflect the variability in both amplitude and occurrence phenomena at close spatial scales. Significant day‐to‐day variability of EEJ and CEJ is observed, with increasing spatial separation. The closely spaced sites, MNC and VEN, show expected similarity but present striking differences in certain monthly averaged patterns. Concurrent observations from three longitudes reveal increasing EEJ amplitudes from west to east and a new observation of increasing CEJ amplitudes from east to west. From these longitudinal trends, we confirm that EEJ strengths are controlled by the large‐scale DE3 nonmigrating tide. A marked difference in CEJ amplitude between MNC and VEN suggests that scale lengths of CEJ and EEJ are different, and we infer that CEJ are primarily generated by short‐scale length variations in the middle atmosphere caused by localized interactions of planetary and gravity waves and are also influenced by the DE3 nonmigrating tide.

Re‐Visiting EEJ and CEJ Occurrences Pattern Under the Influence of Sq Variations of Both Hemispheres

“…Further, we have re‐visited the observations from Archana et al. (2018) at VEN by considering Sq from both hemispheres shown in Figures 14 and 15. Archana et al.…”

Equatorial Counter Electrojet Longitudinal and Seasonal Variability in the American Sector

“…Their study was limited to the afternoon hours, and the relationship between the DE3 eastward wind and ACEJ did not hold in some longitude sectors (especially in the West Pacific sector), indicating that there are additional sources of CEJ longitudinal variability. Archana et al () also related the CEJ longitudinal variability to the DE3 tide, using geomagnetic ground data from three closely spaced stations in the Indian sector.…”

Spatial Variations in Disturbance Ionospheric Currents—Inference From 12 Geomagnetic Storms

“…Ey data is time shifted by 15 min at the bow shock as the propagation delay to magnetospheric region (Bhaskar & Vichare, 2013; Manoj et al, 2008). EEJ is estimated at each equatorial station by calculating the difference with corresponding midlatitude site normalized for a common latitude (Archana et al, 2018). We calculate CC between EEJ and Ey for intervals of 1 hr with 90% data overlap with CC represented at the center of the hour.…”