Simulation of electric field and current during the 11 June 1993 disturbance dynamo event: Comparison with the observations

Abstract

[1] The ionospheric disturbance dynamo signature in geomagnetic variations is investigated using the National Center for Atmospheric Research ThermosphereIonosphere-Electrodynamics General Circulation Model. The model results are tested against reference magnetically quiet time observations on 21 June 1993, and disturbance effects were observed on 11 June 1993. The model qualitatively reproduces the observed diurnal and latitude variations of the geomagnetic horizontal intensity and declination for the reference quiet day in midlatitude and low-latitude regions but underestimates their amplitudes. The patterns of the disturbance dynamo signature and its source "anti-Sq" current system are well reproduced in the Northern Hemisphere. However, the model significantly underestimates the amplitude of disturbance dynamo effects when compared with observations. Furthermore, the largest simulated disturbances occur at different local times than the observations. The discrepancies suggest that the assumed high-latitude storm time energy inputs in the model were not quantitatively accurate for this storm.

The equatorial electrojet during geomagnetic storms and substorms

“…The westward disturbance electrojet at t 4 could be contributed by the eastward steady‐state penetration electric field but be dominated by the westward disturbance dynamo electric field. The prompt penetration electric field under steady state conditions has been noticed in numerical simulations [ Peymirat et al , ; Zaka et al , ], but often overlooked in interpreting observations. For example, Fejer and Scherliess [] and Fejer et al [] attributed the disturbance electric field after four hours of high geomagnetic activity to the sole effect of the disturbance dynamo.…”

Geomagnetic lunar and solar daily variations during the last 100 years

“…The solar activity dependence of S q variations is mainly due to enhanced ionospheric conductivities during high solar activity periods, which lead to increased ionospheric currents [ Takeda et al , ]. Also, the high‐latitude electric field, driven by the magnetospheric dynamo, is enhanced during high solar activity periods, which leaks to lower latitudes and affects S q currents [ Zaka et al , ]. The effect of solar activity on S q variations is evident even on time scales longer than a solar cycle (∼11 years).…”

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].…”