Mid and low-latitudinal ionospheric field-aligned currents derived from the Swarm satellite constellation and their variations with local time, longitude, and season

Latitude Dependence of Interhemispheric Field‐Aligned Currents (IHFACs) as Observed by the Swarm Constellation

“…However, the systematics of midlatitude IHFAC (or IRC) can be found in figures of several previous publications though they were mostly out of the main focus of those papers. In an observational respect, Fathy et al (, Figure 9 and Abstract) reported systematic behavior of midlatitude (|MLAT|> 35°) IHFACs under some seasonal, GLON, and LT conditions though it is not as conspicuous as in our Figures and when averaged over different GLON sectors (Fathy et al, , Figure 4). As for computer simulations, Richmond and Roble (, Figures 7d and 9c) reveal that the two IHFAC systems can exist during equinox for certain longitude sectors.…”

“…Thanks to the coordinated observations of the Swarm satellite constellation (dual‐satellite FAC data of Swarm), Lühr et al () verified, with less assumptions, the results of previous studies. Based on the same data set but for an extended period of about 5 years, Fathy et al () studied the statistical behavior of IHFACs over a wide latitude region range between 15° and 55° in each hemisphere. In summary, only a handful of papers until now have shown clear observational evidences of IHFACs using satellite‐based measurements.…”

“…Simulation studies, such as Yamazaki and Maute (, Figure 9c), also focused mainly on near‐equatorial IHFACs. To the best of the authors' knowledge, only Fathy et al () examined IHFACs over extended MLAT ranges: between 15° and 55° MLAT in each hemisphere. While that study reported a certain latitude dependence of IHFACs, a well‐organized behavior of midlatitude (e.g.,|MLAT|> 35°) IHFACs cannot be deduced from their results (see Figures 4–6 in Fathy et al, ).…”

“…To the best of the authors' knowledge, only Fathy et al () examined IHFACs over extended MLAT ranges: between 15° and 55° MLAT in each hemisphere. While that study reported a certain latitude dependence of IHFACs, a well‐organized behavior of midlatitude (e.g.,|MLAT|> 35°) IHFACs cannot be deduced from their results (see Figures 4–6 in Fathy et al, ). Furthermore, it was not discussed in detail why midlatitude IHFACs show different trends, if any, from low‐latitude currents.…”

“…The peculiarities of December solstice IHFACs are also missing in Lühr et al () because the Swarm dual‐satellite FAC data for these months were not available at the time of this initial study. While Fathy et al () argued similarities of IHFACs between September (March) and December (June) under some LT and GLON conditions, it was not explicitly discussed whether IHFACs during equinoxes resembles the overall trends of those of June or of December solstices. Lately, Lühr et al () have intensively studied the peculiar behavior of low‐latitude IHFACs during December solstice, as observed by the Swarm constellation.…”