Advanced separation and classification of ionospheric troughs in midnight conditions

Abstract

This study uses a novel approach to separate and classify different ionospheric troughs from CHAMP satellite data in the winter midnight ionosphere of the southern hemisphere at high solar activity (2000–2002). The main ionospheric trough (MIT) was separated from the high latitude trough (HLT). The separation was performed through an analysis of troughs in the frame of a model of the diffuse auroral particle precipitation. Two types of HLT were distinguished. In the mid-latitude ionosphere, the MIT was separated from the ring ionospheric trough (RIT), which is formed by the decay processes of the magnetospheric ring current. The separation was performed on the basis of an analysis of the prehistory of all geomagnetic disturbances for the period under study. In addition, a decrease in the electron density, which is superimposed on the MIT and masks its minimum position, is quite often observed at American and Atlantic longitudes near the Polar Circle.

Observational Characteristics of High‐Latitude Ionization Trough Seen by Swarm

“…This observation is consistent with the coincidence of the epochs of plasma density and velocity. All the trough events that we examined are characterized by high plasma velocity, and therefore, these events belong to high-latitude trough 2 (HLT2), following the classification by Karpachev (2022aKarpachev ( , 2022b. Electron outflow (or downward FAC) may contribute to the development of high-latitude troughs, but high-speed plasma convection is considered to play the primary role because troughs are detected even in the absence of downward FAC.…”

“…However, the formation of sharp boundaries of high-latitude troughs required an additional process, and Grebowsky et al (1983) suggested the trough formation by the enhanced dissociative recombination rate associated with high-speed plasma convection. Recent studies (Karpachev, 2022a(Karpachev, , 2022b(Karpachev, , 2023, investigated the conditions for the development of high-latitude troughs under midnight, morning, evening, and noon conditions using the electron concentration data from the Challenging Minisatellite Payload (CHAMP) satellite. Following these studies, two types of high-latitude troughs develop.…”

Structure of the High-Latitude Noon Ionosphere of the Southern Hemisphere

“…This article continues a series of studies on the irregular structure of the winter high-latitude ionosphere [1][2][3]. The main purpose of these studies is the separation and classification of ionospheric troughs.…”

“…In addition, there are various types of mid-latitude quasi-troughs. Within the framework of this task, the structures of the midnight ionosphere [1], the early morning and evening ionosphere [2], and the late morning ionosphere [3] were studied in detail. The study was performed using an advanced method based on a simple visual model of the auroral oval [8].…”

Topside sounder as a most reliable instrument for the Space Weather monitoring. Short review and future perspectives.

“…It was the time of many discoveries concerning the ionosphere, especially its structure (equatorial anomaly, main ionospheric trough etс.) [3][4][5][6].…”