Formation and identification of counter electrojet (CEJ)

Abstract

This study investigates the possible occurrence of counter equatorial electrojet (CEJ) and a quicker method for identification of CEJ. Data from a chain of magnetic observatories of World Data Center for Geomagnetism in Tokyo, Japan, was employed. It is strikingly interesting to observe that most CEJ occurred from morning through new dusk, with almost the same pattern of dHin depression. In Ascension Island (ASC), Huancayo (HUA) and Pondicherry (PND), most ∆H were found to be less than zero, which reveals an indication of full CEJ. Partial CEJ occurrences were observed during some hours at these stations where ∆Hin >0. It is suggested that IMF turning north indicates CEJ, hence storm effects could also be attributed to CEJ existence. Some of our new findings are at variance with results of some previous workers; hence further work is suggested for further clarification. A quick method of easy identification of CEJ is suggested.

Variability of equatorial counter electrojet signatures in the Indian region

“…The underlying processes that drive the variability in the CEJ current at two different longitudes and the spatial scales of the characteristics are still an open question [ Denardini et al , ]. Very few attempts have been made to assess CEJ variability and its longitudinal separation at 25° or less [ Vichare and Rajaram , ; Francisca et al , ], although study of satellite and ground measurements did indicate a decrease in spatial correlation of EEJ strength at 15–20° longitude separation [ Manoj et al , ; Alken and Maus , ]. Following these observations, the ongoing experiment to obtain continuous data at equatorial station pairs separated by 15° longitude (i.e., Vencode and Hyderabad and Campbell Bay and Port Blair) in the Indian region was initiated in 2010.…”

“…Substantial day‐to‐day variability of CEJ over a large longitudinal range (greater than 45°) has been extensively reported [ Gouin , ; Rao and Raja Rao , ; Patil et al , ; Alex and Mukherjee , ; Doumouya et al , ; Francisca et al , ; Bolaji et al , ]. Rangarajan and Rastogi [] and Kane and Trivedi [] inferred that CEJ events may not occur on the same day at locations separated by 30° longitude or less, suggesting that the variability in occurrence pattern at observatories is due to the neutral wind patterns, which are confined at longitudinal zones.…”

“…Rangarajan and Rastogi [] and Kane and Trivedi [] inferred that CEJ events may not occur on the same day at locations separated by 30° longitude or less, suggesting that the variability in occurrence pattern at observatories is due to the neutral wind patterns, which are confined at longitudinal zones. Using Ascension Island, Huancayo, and Pondicherry magnetic observatories, Francisca et al [] reported that CEJ occurrence is not concurrent at these widely separated longitudes and demonstrated the effect of CEJ on EEJ amplitudes, causing deviations in the monthly averages of EEJ amplitudes at the three observatories.…”

“…Based on observations from ground magnetometer, radar, and satellite measurements, different mechanisms have been proposed for westward currents arising by multiple processes influencing ionospheric electrodynamics. Of these, principal ones are as follows: (i) upward penetration of the gravity waves from mesosphere to lower thermosphere region [ Raghavarao and Anandarao , ; Vineeth et al , , ], (ii) appropriate phase combination of global scale tidal wind modes [ Somayajulu et al , ; Gurubaran , ; Sridharan et al , ; Manju and Viswanathan , ], (iii) influence of solar flares [ Rastogi , 1999; Manju and Viswanathan , ; Manju et al , ], (iv) change in atmospheric temperature associated with the sudden stratospheric warming [ Stening et al , ; Rastogi , 1999; Liu and Roble , ; Sidharan et al , ], (v) during substorm recovery phase [ Kikuchi et al , ; McCreadie , ], and (vi) change in orientation of interplanetary magnetic field southward component B z [ Alex and Mukherjee , ; Sizova , , ; Francisca et al , ; Phani Chandrasekhar and Thinesh Kumar , ].…”

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

“…Changes in the E-region irregularities and the reversal of ionospheric drifts have been associated with CEJ events (Fambitakoye et al 1973;Rastogi 1974). The westward currents manifested during some instances of CEJs may be caused by reversal of the interplanetary magnetic field (IMF-Bz) component from south to north (Rastogi 1974;Sizova 2002;Francisca et al 2013) and or atmospheric tidal effects (Bhargava et al 1980;Somayajulu et al 1993;Sridharan et al 2002). Recent studies show that rise in atmospheric temperature connected with the phenomena of sudden stratospheric warming (SSW) exhibits positive correlation with occurrences of CEJs (Matsuno 1971;Liu and Roble 2002;Sridharan et al 2009).…”