Occurrence of the dayside three‐peak density structure in the F₂ and the topside ionosphere

Abstract

In this work, we discuss the occurrence of the dayside three‐peak electron density structure in the ionosphere. We first use a set of ground‐based and satellite‐borne instruments to demonstrate the development of a large‐amplitude electron density perturbation at the recovery phase of a moderate storm of 11 October 2008. The perturbation developed in the F2 and low topside ionospheric regions over the American sector; it was concentrated on the north from the equatorial ionization anomaly (EIA) but was clearly separated from it. At the F2 region height, the amplitude of the observed perturbation was comparable or even exceeded that of the EIA. Further analysis of the observational data together with the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics model simulation results showed that a particular local combination of the thermospheric wind surges provided favorable conditions for the generation of the three‐peak EIA structure. We further proceed with a statistical study of occurrence of the three‐peak density structure in the ionosphere in general. Based on the analysis of 7 years of the in situ data from CHAMP satellite, we found that such three‐peak density structure occurs sufficiently often during geomagnetically quiet time. The third ionization peak develops in the afternoon hours in the summer hemisphere at solstice periods. Based on analysis of several quiet time events, we conclude that during geomagnetically quiet time, the prevailing summer‐to‐winter thermospheric circulation acts in similar manner as the storm‐time enhanced thermospheric winds, playing the decisive role in generation of the third ionization peak in the daytime ionosphere.

Comparison of GOLD Nighttime Measurements With Total Electron Content: Preliminary Results

“…First, the southern hemisphere third peaks are (at 20°S geomag) not as far away from the geomagnetic equator as the one that they found (at 30°S geomag). It is accompanied by a weak EIA southern crest, whereas the third peak in Astafyeva et al (2016) did not necessarily coexist with a weaker EIA southern crest. Figure 9d in Astafyeva et al (2016) showed that sometimes the magnitude of this third peak could be much smaller than the two main crests of EIA.…”

“…It is accompanied by a weak EIA southern crest, whereas the third peak in Astafyeva et al (2016) did not necessarily coexist with a weaker EIA southern crest. Figure 9d in Astafyeva et al (2016) showed that sometimes the magnitude of this third peak could be much smaller than the two main crests of EIA. Second, by checking the GOLD data, we mainly find this third peak phenomenon in October and November.…”

“…They also reproduced the third peak during the December solstices in 2012 in numerical models. Astafyeva et al (2016) utilized electron density profile from CHAllenging Minisatellite Payload (CHAMP) between 2003 and 2009 to do a statistical study on this third peak and found that it mainly appeared in the afternoon in the summer hemisphere at solstices periods during the geomagnetic quiet time. Compared with previous studies, the case on DOY 297 is similar.…”

How Magnetically Conjugate Atmospheres and the Magnetosphere Participate in the Formation of Low‐Energy Electron Precipitation in the Region of Diffuse Aurora

“…This permits us to consider the details of precipitation flux formation based on the steady‐state solution of Equation and explore the details of MI coupling between the two magnetically conjugate atmospheres and the magnetosphere and understand under what conditions interhemispheric asymmetry arises. In this paper, however, we do not discuss how these kinds of the asymmetries form and instead refer readers to many studies of this issue in the literature (e.g., Astafyeva et al, 2016, 2020; Ostgaard et al, 2016; Sato et al, 2016; Zesta et al, 2017, and references therein).…”

Classification of High Density Regions in Global Ionospheric Maps With Neural Networks

“…EIAs are two extended regions of elevated TEC located on opposite sides of geomagnetic equator (see Figure 1a). However, sometimes three distinct anomalies (Maruayama et al, 2016;Astafyeva et al, 2016Astafyeva et al, , 2017 or more are observed (see Figure 1b,c). These multiple daytime TEC intensifications may not fit into strict definition of EIAs.…”