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  • Yamazaki_et_al-2016-Journal_of_Geophysical_Research-_Space_Physics

    Rights statement: ©2016. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Day-to-day variability of midlatitude ionospheric currents due to magnetospheric and lower atmospheric forcing

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Published
<mark>Journal publication date</mark>23/07/2016
<mark>Journal</mark>Journal of Geophysical Research: Space Physics
Issue number7
Volume121
Number of pages20
Pages (from-to)7067-7086
<mark>State</mark>Published
Early online date23/07/16
<mark>Original language</mark>English

Abstract

As known from previous studies on the solar quiet (Sq) variation of the geomagnetic field, the strength and pattern of ionospheric dynamo currents change significantly from day to day. The present study investigates the relative importance of two sources that contribute to the day-to-day variability of the ionospheric currents at middle and low latitudes. One is high-latitude electric fields that are caused by magnetospheric convection, and the other is atmospheric waves from the lower atmosphere. Global ionospheric current systems, commonly known as Sq current systems, are simulated using the National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model. Simulations are run for 1–30 April 2010 with a constant solar energy input but with various combinations of high-latitude forcing and lower atmospheric forcing. The model well reproduces geomagnetic perturbations on the ground, when both forcings are taken into account. The contribution of high-latitude forcing to the total Sq current intensity (Jtotal) is generally smaller than the contribution of wave forcing from below 30 km, except during active periods (Kp≥4), when Jtotal is enhanced due to the leakage of high-latitude electric fields to lower latitudes. It is found that the penetration electric field drives ionospheric currents at middle and low latitudes not only on the dayside but also on the nightside, which has an appreciable effect on the Dst index. It is also found that quiet time day-to-day variability in Jtotal is dominated by symmetric-mode migrating diurnal and semidiurnal tidal winds at 45–60° latitude at ∼110 km.

Bibliographic note

©2016. The Authors.
This is an open access article under the terms of the Creative Commons
Attribution License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited.