Latitudinal profile of the ionospheric disturbance dynamo magnetic signature: comparison with the DP2 magnetic disturbance

Abstract

Abstract. During magnetic storms, the auroral electrojets intensification affects the thermospheric circulation on a global scale. This process which leads to electric field and current disturbance at middle and low latitudes, on the quiet day after the end of a storm, has been attributed to the ionospheric disturbance dynamo (Ddyn). The magnetic field disturbance observed as a result of this process is the reduction of the H component amplitude in the equatorial region which constitutes the main characteristic of the ionospheric disturbance dynamo process, associated with a westward electric current flow. The latitudinal profile of the Ddyn disturbance dynamo magnetic signature exhibits an eastward current at mid latitudes and a westward one at low latitudes with a substantial amplification at the magnetic equator. Such current flow reveals an "anti-Sq" system established between the mid latitudes and the equatorial region and opposes the normal Sq current vortex. However, the localization of the eastward current and consequently the position and the extent of the "anti-Sq" current vortex changes from one storm to another. Indeed, for a strong magnetic storm, the eastward current is well established at mid latitudes about 45 • N and for a weak magnetic storm, the eastward current is established toward the high latitudes (about 60 • N), near the Joule heating region, resulting in a large "anti-Sq" current cell. The latitudinal profile of the Ddyn disturbance as well as the magnetic disturbance DP2 generated by the mechanism of prompt penetration of the magnetospheric convection electric field in general, show a weak disturbance at the low latitudes with a substantial amplification at the magnetic equator. Due to the intensity of the storm, the magnitude of the DP2 appears higher than the Ddyn over the American and Asian sector contrary to the African sector.

Equatorial ionosphere responses to two magnetic storms of moderate intensity from conjugate point observations in Brazil

“…Daytime EIA suppression due to DDEF was reported by Sreeja et al [2009] during a moderate storm of January 2005. Such daytime EIA suppression generally occurs in association with the equatorial electrojet (EEJ) attenuation, as both are controlled by the same equatorial zonal electric field [see, e.g., Sastri , 1988; Le Huy and Amory‐Mazaudier , 2005; Zaka et al , 2009; Rastogi and Klobuchar , 1990]. We may examine the EIA response features with the help of the foF2, hmF2 and F layer height variations over the EIA trough (crest) location Sao Luis (Cachoeira Paulista) plotted in Figure 7.…”

Signature of the coronal hole near the north crest equatorial anomaly over Egypt during the strong geomagnetic storm 5 April 2010

“… Le Huy and Amory‐Mazaudier [2005, 2008] isolated the magnetic disturbance due to this physical process and named it Ddyn. During the last decades many experimental and theoretical studies illustrated the characteristics of to the ionospheric disturbance dynamo process [ Fejer et al , 1983; Sastri , 1988; Abdu et al , 1997; Fambitakoye et al , 1990; Mazaudier and Venkateswaran , 1990; Fejer and Scherliess , 1995; Richmond et al , 2003; Zaka et al , 2009, 2010a, 2010b]. The storm winds also lift the ionization to regions of lower loss, producing daytime increases in hmF2, in foF2, and in total electron content (TEC) and global changes in the atmospheric composition [ Jones , 1971; Jones and Rishbeth , 1971; Volland , 1979].…”

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…The westward disturbance winds, and thus the electrodynamic disturbances, can persist for many hours after the high-latitude energy input ceases (Huang et al 2005a(Huang et al , 2005b. Accordingly, the disturbance dynamo effects are often detected during the recovery phase of a storm (e.g., Le Huy and Amory-Mazaudier 2005;Zaka et al 2009;.…”