Daytime altitude variations of the equatorial, topside magnetic field‐aligned ion transport at solar minimum

Abstract

[1] Above the ion density peak, the interhemispheric transport of plasma plays an important role in shaping the spatial density distribution of the ionosphere. This study uses daytime observations of the ion drift, density, and composition near the geomagnetic equator from the Coupled Ion-Neutral Dynamics Investigation on board the Communication/Navigation Outage Forecasting System satellite, for the period of extremely low solar activity present in 2008 and 2009, to explore the altitude variation in interhemispheric transport at heights reaching up to the O + /H + transition height. These observations revealed that the physical processes leading to interhemispheric transport do not change with altitude. These processes include forcing from the lower thermosphere, E B drift, and chemical processes. Their longitudinal variations combine with the structure of the geomagnetic field to cause the differences in interhemispheric transport seen in different longitude regions. At all longitudes, the quantity of plasma crossing the geomagnetic equator depends strongly on ion density, which causes large changes to the altitude variations of the field-aligned plasma drift speed.

On the variation in the ionospheric response to geomagnetic storms with time of onset

“…Neutral winds drag the embedded plasma along with it. When a component of the neutral wind is parallel to the magnetic field, it can push plasma along the field lines [Bramley and Young, 1968;Burrell et al, 2012Burrell et al, , 2013. Enhanced equatorward winds can therefore potentially affect plasma densities by lifting the F layer and reducing loss through recombination [Rishbeth et al, 1987].…”

A Year‐Long Comparison of GPS TEC and Global Ionosphere‐Thermosphere Models

“…Especially at middle and lower latitudes, forcing from the lower atmosphere (e.g., Forbes, 1996;Goncharenko et al, 2010;Immel, 2005;Immel et al, 2009;Scherliess et al, 2008) via eddy diffusion can cause vertical mixing of neutrals that influence the local atomic/molecular ratio. Neutral winds can also push plasma up or down magnetic field lines (Bramley & Young, 1968;Burrell et al, 2012Burrell et al, , 2013. Depending on the angle of the magnetic field and direction of the wind, the winds can move the height of the F 2 peak to higher or lower altitudes (Hedin & Mayr, 1973;Jones & Rishbeth, 1971;Muella et al, 2010;Rishbeth et al, 1978;Rishbeth & Mendillo, 2001).…”

Universal time effect in the response of the thermosphere to electric field changes

“…Therefore, magnetospheric electric fields are a crucial process when considering any possible UT effects. In addition, the component of the neutral wind along the magnetic field can strongly control the structure of the ionosphere-when the magnetic field is oriented between the horizontal and vertical directions, neutral winds can push plasma along the field lines [Bramley and Young, 1968;Burrell et al, 2012Burrell et al, , 2013, causing the height of the F 2 peak to move up or down, depending on the structure of the wind and magnetic field [Hedin and Mayr, 1973;Rishbeth et al, 1978;Rishbeth and Mendillo, 2001;Muella et al, 2010]. The timescale of velocity changes in the ions is significantly shorter than in the neutrals [Vasyliunas, 2005].…”