Dependence of the Equatorial Electrojet on Auroral Activity and In Situ Solar Insulation

Abstract

By using 10 years of Challenging Minisatellite Payload satellite observations, we investigate the average conditions of the interplanetary magnetic field (IMF) prevailing during the westward counter equatorial electrojet (CEJ). Equally, we compared the average IMF conditions accompanying high-latitude field-aligned currents of the Region 1 (R1) and Region 2 (R2). It shows that both CEJ and high-latitude field-aligned currents events when R2 is greater than R1 tend to happen preferably during the northward turning of the IMF Bz and the substorm recovery phase. Sunlight has an important influence on the longitudinal distribution of the equatorial electrojet (EEJ), and the effect is opposite to the tidal electric field at E region. The anticorrelation between cos 0.5 (SZA) (solar zenith angle effect) average values during CEJ events and EEJ intensity is most prominent around June solstice. By using combined measurements from Challenging Minisatellite Payload and DMSP satellites, it is found that before the occurrence and in the initial phase of a subauroral polarization stream the EEJ gets enhanced, and after about 30 min it reduces in intensity. The CEJ occurrence rate more than doubles during subauroral polarization stream periods compared to normal conditions.

Relationship between large-scale ionospheric field-aligned currents and electron/ion precipitations: DMSP observations

“…5a, but for the electron energy flux distribution in the southern hemisphere Fig. 5 (continued) dusk sides, which is consistent with the previous findings (e.g., Christiansen et al 2002;Le et al 2010;Wang et al 2019). All these comparisons further support the reliability of the DMSP FACs.…”

Effects of Subauroral Polarization Streams on the Equatorial Electrojet During the Geomagnetic Storm on June 1, 2013

“…Various mechanisms have been proposed to explain the storm‐time EEJ, including zonal and meridional winds (e.g., Anandarao & Raghavarao, 1987; Wang et al., 2019). During a geomagnetic storm, the high‐latitude Joule heating and ion‐drag force can trigger disturbances in the coupled I–T system and the disturbance wind can travel to low latitudes and alter equatorial dynamo electric fields and currents (Blanc & Richmond, 1980).…”

“…The potential roles of SAPS in the high-to low-latitude coupling of the upper atmosphere and its impact on the CEJ have been investigated in several previous studies. For example, Wang et al (2019) used 10year CHAMP observations and reported that the CEJ occurrence rate during SAPS is double compared with that under normal conditions, indicating the potential effects of SAPS. However, the internal physical mechanisms of the CEJ changes during the SAPS period have not been elucidated.…”

“…first discovered by Gouin (1962) based on the negative deflection of the horizontal magnetic field around local noon and were called CEJ by Gouin and Mayaud (1967). Subsequently, researchers explored the variability of the CEJ with respect to the local time (LT), longitude, and season (e.g., Alken & Maus, 2007;Kikuchi et al, 2000Kikuchi et al, , 2003Lühr et al, 2008Lühr et al, , 2012Soares et al, 2018;Vichare & Rajaram, 2011;Vineeth et al, 2012Vineeth et al, , 2016Wang et al, 2019Wang et al, , 2020Yamazaki, Stolle, Matzka, Liu, & Tao, 2018;Zhou et al, 2018). Rastogi (1974) used magnetic field measurements from equatorial stations and studied the LT variation of the daytime CEJ, which can be expressed by depressions in the geomagnetic horizontal component.…”

Recent ionospheric investigations in China (2018–2019)

“…Wang H et al (2019) used 10 years of CHAMP observations to investigate how the counter equatorial electrojet (CEJ) depends on interplanetary magnetic field (IMF) conditions. The longitudinal distribution of the equatorial electrojet (EEJ) is closely modulated by the solar zenith angle.…”