Effect of interhemispheric currents on equivalent ionospheric currents in two hemispheres: Simulation results

Abstract

In this research, we used numerical simulation to study the effect of interhemispheric field‐aligned currents (IHCs), going between two conjugate ionospheres in two hemispheres, on the equivalent ionospheric currents (EICs). We computed the maps of these EICs in two hemispheres during summer‐winter conditions, when the effect of the IHCs is especially significant. The main results may be summarized as follows. (1) In winter hemisphere, the IHCs may significantly exceed and be a substitute for the local R1 currents, and they may strongly affect the magnitude, location, and direction of the EICs in the nightside winter auroral ionosphere. (2) While in summer polar cap the EICs tend to flow sunward, and in winter polar cap the EICs turn toward dawn due to the effect of the IHCs. (3) The well‐known reversal in the direction of the EICs in the vicinity of the midnight meridian, in winter hemisphere, is observed not at the polar caps boundary (as usually expected) but equatorward of this boundary in the region of the IHCs location. (4) The IHCs in winter hemisphere may be, in fact, not only a substitute for the R1 currents but also the major source of the Westward Auroral Electrojet, observed in both hemispheres during substorm activity.

Energy‐Dispersive Field‐Aligned Warm Ion Enhancement in the Plasma Sheet During a Substorm Growth Phase: A THEMIS Event

“…The perturbations were southward and eastward at both stations but vertically downward (upward) at lower (higher) latitudes (indicated by magenta arrows), indicating an enhancement of the westward equivalent current. Such a current enhancement can be associated with enhanced region‐2 FACs under enhanced global convection (Lyatskaya et al., 2016). The above observations suggested that the equatorward penetration of the enhanced convection was likely to reach the TH‐D location first after around 03:15 UT and then the TH‐E location sometime later.…”

Dynamics of the field-aligned currents distribution asymmetry during substorms in the equinox season

“…Suvorova [2017] показала, что различие координат геомагнитных полюсов в Северном и Южном полушариях вызывает сильную асимметрию освещенности и, соответственно, волновой проводимости полярной ионосферы в летние и зимние месяцы. Теоретические работы [Richmond, Roble, 1987;Benkevich et al, 2000;Benkevich, 2006;Lyatskaya et al, 2014Lyatskaya et al, , 2015 рассматривают квазистационарные модели электрической цепи, содержащей генератор и две параллельно соединенные ионосферы в сезоне зима-лето. Модели предсказывают, что из областей с резким перепадом проводимости летней полярной ионосферы, особенно на терминаторе, могут стекать квазистационарные МПТ.…”

“…Однако используемая процедура статистического усреднения данных наблюдений с интервалом 10 мин не позволяет проследить глобально более быструю динамику интенсивности ПТ в ходе взрывной фазы. То же можно сказать и о наиболее развитых теоретических моделях МПТ [Lyatskaya et al, 2015] в квазистационарном приближении.…”