Formation of maximum electric potential at the geomagnetic equator by the disturbance dynamo

Abstract

[1] The effect of a disturbance dynamo during geomagnetic activity on the equatorial ionospheric electric fields is investigated, using model results from the NACR/TIEGCM (National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model). Model runs are made for different time-lengths of geomagnetic activity, for different seasons, and for different solar activities to investigate how and where the maximum electric potential forms. Model results show that the maximum electric potential is located at around 300 km altitude and at local time after the pre-reversal enhancement at equinox for high solar activity. For the case at solstice, without pre-reversal enhancement, the location moves to around 110 km altitude and to the local time close to midnight. Giving various parameters in the model runs to simulate different background conditions, many important output quantities are used to study the distributions of perturbed electric potential at the geomagnetic equator. Model investigation indicates that normal quiet time electrodynamics, at different seasons with different solar activities, significantly affect the distribution of perturbed current density associated with geomagnetic activity. Furthermore, model results also reveal that significant perturbed zonal electric fields tend to build up six hours after the onset of geomagnetic activity, except at regions close to sunset and sunrise, and the perturbed vertical electric fields increase with the time length of geomagnetic activity.Citation: Huang, C. M., and M. Q. Chen (2008), Formation of maximum electric potential at the geomagnetic equator by the disturbance dynamo,

Low-latitude ionospheric-thermospheric response to storm time electrodynamical coupling between high and low latitudes

“…The geomagnetic storm can initiate ESF in the post midnight sector because of abnormal upward reversals in the vertical plasma drift under the action of eastward electric fields of ionospheric disturbance dynamo (IDD) [Kelley and Maruyama, 1992;Hysell and Burcham, 1998] and also often because of penetration of eastward electric fields associated with northward turning of IMF Bz . There are ample of studies reported which explain the development/inhibition of ESF during geomagnetic storm and the role of storm time perturbation electric fields during last three decades [Aarons, 1991;Sastri et al, 1993;Abdu et al, 1995;Fejer et al, 1999;Basu et al, 2001bBasu et al, , 2005Sobral et al, 2001;Huang et al, 2005, Huang andChen, 2008;Tulasi Ram et al, 2008].…”

Plasma drift observations associated with intense magnetic storms by the IPEI on board ROCSAT‐1

“…We also see that the magnitudes of the poleward penetration electric fields decay very fast from high latitudes to low latitudes in the southern hemisphere, but some contributions may come from the effect of the local time dependence. These westward plasma drifts presumably result from the penetration electric fields because the meridional electric fields associated with the disturbance dynamo in the daytime are very small as compared with the drift values shown in Figure 5a [ Huang and Chen , 2008], which will be demonstrated in section 3.…”

“…A interesting result revealed from the model run is the nighttime meridional electric field raises to a very large value (e.g., 5.6 mV/m in Figure 7) during the intense storm period, but the maximum magnitude for the eastward zonal component is only up to about 2 mV/m at 0500 LT, where appears the maximum eastward electric field in the storm time [ Scherliess and Fejer , 1997; C.‐M. Huang et al , 2005; Huang and Chen , 2008]. It explains why the westward plasma drifts can be easier seen than the upward/poleward plasma drifts in the nighttime, as shown in Figures 1a and 1b, Figures 3a and 3b and Figures 5a and 5b.…”

“…The resulting perturbed electric fields have comparable magnitudes with those in the quiet time condition, during the main phase or recovery phase of the geomagnetic activity [ Fejer and Scherliess , 1995; Fejer and Scherliess , 1997; Scherliess and Fejer , 1997; Fuller‐Rowell et al , 2002; Richmond et al , 2003; C.‐M. Huang et al , 2005; Huang and Chen , 2008], and can last for many hours while geomagnetic activities decrease. The perturbed zonal electric field caused by the disturbance dynamo, at the low‐latitude and equatorial ionosphere, has an opposite polarity with that of quiet time result; the meridional component is mainly poleward/upward and dominates in the nighttime [ Richmond et al , 2003; C.‐M.…”

“…The perturbed zonal electric field caused by the disturbance dynamo, at the low‐latitude and equatorial ionosphere, has an opposite polarity with that of quiet time result; the meridional component is mainly poleward/upward and dominates in the nighttime [ Richmond et al , 2003; C.‐M. Huang et al , 2005; Huang and Chen , 2008].…”