The E region wind dynamo is a key linkage in atmosphere‐ionosphere coupling, but relatively little is known about variability of the corresponding E region currents in terms of connections with atmosphere dynamics. In this paper we analyze ground magnetic variations ΔB during 2009 at two midlatitude stations to reveal planetary wave (PW) periodicities near those of well‐known atmospheric normal modes, i.e., 5, 10, and 16 days. In the neutral atmosphere these waves are westward propagating with zonal wave number s = 1. The two stations are at the same magnetic latitude and are nearly conjugate in longitude, which leads to following new insights: First, the amplitude and phase variations between the two stations do not conform to simple westward propagating waves with zonal wave number s = 1, implying that the underlying physics is more complex, in part due to modulation by the predominantly s = 1 longitude‐dependent magnetic field. There is also compelling evidence that much ΔB variability near PW periods arises through the product of solar‐controlled conductivity and PW‐related electric field in the expression for electric current, mainly arising from solar radiation periodicities longer than the solar rotation period. For instance, interactions between solar periodicities in conductivity near 53d and 83d and PW periodicities in total electric field yield secondary peaks in the ΔB spectrum that contribute to its variability at periods less than 20d. In fact, most of the observed ΔB variability arises from these two latter sources, rather than directly from the original driving PW oscillations.
Substorms are explosive disturbances in our magnetotail that impact the earth's ionosphere. They happen on average several times per day and as a result of this phenomenon, we can see the marvelous aurora. Substorms happen on the nightside of the earth and can take place over a wide range of latitudes and longitudes. In this study, we show that substorms tend to begin at earlier local times during geomagnetically active times than during quiet times. We interpret this tendency as a sign that ionospheric conditions may play a role in determining where substorms occur.
Ionospheric dayside dynamics is strongly controlled by the interaction between the Interplanetary Magnetic Field (IMF) and the Earth's magnetic field near the dayside magnetopause, while nightside ionospheric dynamics depends mainly on magnetotail activity. However, we know little about the influence of magnetotail activity on the dayside ionospheric dynamics. We investigate this by performing superposed epoch analyses of ground magnetic field data for substorms occurring during northward IMF. In such substorms, dayside reconnection is minimized, allowing us to separate the effects of the magnetotail activity on the dayside current system. We find that as nightside activity elevates, the dayside ionospheric current elevates. Our analyses indicate that the lobe cells are less distinct before onset than during non‐substorm northward IMF conditions. They become more pronounced after onset, possibly due to magnetospheric reconfiguration or a remote effect of the nightside current. We discuss possible mechanisms that may explain our observations.
<p>Substorm onset location varies over a range of magnetic local time (MLT) and magnetic latitudes (MLat). It is well known that about 5% of the variation in onset MLT can be explained by variations in interplanetary magnetic field orientation and dipole tilt angle. Both parameters introduce an azimuthal component in the magnetic field in the magnetosphere such that the projection of the onset MLT in the ionosphere is shifted. The MLT of the onset near the magnetopsheric equatorial plane is even less predictable. Recent studies have suggested that gradients in the ionospheric Hall conductance lead to a duskward shift of tail dynamics, which could also influence the location of substorm onset. Our goal is to test these ideas by quantifying the dependence of the spatial variation of the onset location on external and internal conditions. We focus on the correlation between the substorm onset location with conditions prior to the onset, such as the interplanetary magnetic field By component, dipole tilt angle, and estimates of the Hall conductance. Linear regression analysis is used to determine the substorm onset location dependence on the proposed variables.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.