Climatology of Spread F over Tucumán from Massive Statistical Analysis of Autoscaled Data

Automatic ionogram interpretation methods developed for real-time ionospheric monitoring can be applied in retrospective studies to analyze large quantities of data. The Autoscala software, implemented for such a purpose, includes a routine for automatic detection of diffused echoes known as spread F, which appear in ionograms due to the presence of ionospheric irregularities along the radio signal path. The main objective of this routine is to reject bad quality ionograms. This new capability was used in a climatological study including a large number of ionograms recorded at the low-latitude ionospheric station of Tucumán (26.9° S, 294.6° E, magnetic latitude 15.5° S, Argentina). The study took into account different levels of geomagnetic and solar activity from 2012 to 2020. The results demonstrate the capability of Autoscala to capture the main signature characteristics of spread F and the temporal evolution of the ionosphere peak heigh hmF2, capturing the post-sunset plasma surge that precedes development of spread F. Maximum occurrence of spread F is observed in local summer, with a tendency to shift before midnight with increasing solar activity. Other new climatological details that emerged from the study are illustrated and briefly discussed, dealing with connection with geomagnetic activity, and morning hmF2 behavior after extremely marked nighttime spread F occurrence.

Evolution of the Pakistan Space Weather Centre (PSWC)

This work focuses on the progress of space weather monitoring in Pakistan. Pakistan's first geomagnetic observatory was established in Quetta in 1953. However, the beginning of what we would now call space weather services on a formal level took place in 1971, when the national space agency, the Pakistan Space and Upper Atmosphere Research Commission (SUPARCO), established the country's first ionospheric station. Later, in 1983, a geomagnetic observatory was set up in Karachi with the aim of providing high frequency (HF) support and geomagnetic storm alerts to relevant users. With the progression of time, nations began to prioritize space weather monitoring to ensure the safety and security of technological assets. Therefore, it was considered imperative to upgrade the array of instruments in order to maintain the reliability of operations and the efficient utilization of data to contribute to research at local, regional and global scales. Pakistan has recently established a dedicated space weather monitoring facility known as the Pakistan Space Weather Centre (PSWC). This paper describes the historic evolution of space weather infrastructure in Pakistan and the current contribution of the PSWC.

Geomagnetic disturbances at F1-layer heights under different solar activity conditions over Norilsk

We analyze the influence of geomagnetic disturbances on the electron density Ne at Norilsk ionospheric station (69° N; 88° E) at F1-layer heights (120–200 km). For the analysis, we have selected 25 moderate and weak geomagnetic disturbances for two seasons — spring and fall — of 2003–2014. Using the Ne values obtained from measurements made with the Norilsk digisonde during this period, we analyze Ne variations during geomagnetic disturbances in spring and fall for a long period of time. We determine the effect of spring-fall asymmetry occurring in all solar activity phases and manifesting itself in a significant decrease in the electron density during the main phase of fall storms at all heights in comparison with quiet days: up to 2.6 times at a height of 200 km and slightly less at lower heights. This phenomenon is not observed during spring disturbances: Ne variations are much weaker.

Electron density in the F1 layer over Norilsk in 2007–2014

We report the results of the analysis of annual variations in daily electron density (N) for various solar activity conditions — minimum, rise, and maximum (2007–2014) — obtained from digisonde measurements at the ionospheric station Norilsk (69.4° N, 88.1° E). New coefficients of the known semi-empirical model (SEM) describing the connection between N and thermosphere characteristics are calculated to identify regularities of these variations exactly at Norilsk station. The height changes of annual variations in the noon electron density N are obtained in the F1 region (120–200 km). The experimental data approximation describes N quite satisfactorily at these heights in the daytime of different seasons under different solar activity conditions. It is shown that in the years of solar minimum at all heights of the F1 layer the tendency remains for maximum N in summer and for minimum N in winter. In later years and in the year of maximum solar activity, a characteristic feature of the behavior of N is the change in the phase of the annual variation by 180° in the range of heights from 170 to180 km: maximum N is observed in winter; and minimum, in summer.

Electron density in the F1 layer over Norilsk in 2007–2014

We report the results of the analysis of annual variations in daily electron density (N) for various solar activity conditions — minimum, rise, and maximum (2007–2014) — obtained from digisonde measurements at the ionospheric station Norilsk (69.4° N, 88.1° E). New coefficients of the known semi-empirical model (SEM) describing the connection between N and thermosphere characteristics are calculated to identify regularities of these variations exactly at Norilsk station. The height changes of annual variations in the noon electron density N are obtained in the F1 region (120–200 km). The experimental data approximation describes N quite satisfactorily at these heights in the daytime of different seasons under different solar activity conditions. It is shown that in the years of solar minimum at all heights of the F1 layer the tendency remains for maximum N in summer and for minimum N in winter. In later years and in the year of maximum solar activity, a characteristic feature of the behavior of N is the change in the phase of the annual variation by 180° in the range of heights from 170 to180 km: maximum N is observed in winter; and minimum, in summer.

Geomagnetic disturbances at F1-layer heights under different solar activity conditions over Norilsk

We analyze the influence of geomagnetic disturbances on the electron density Ne at Norilsk ionospheric station (69° N; 88° E) at F1-layer heights (120–200 km). For the analysis, we have selected 25 moderate and weak geomagnetic disturbances for two seasons — spring and fall — of 2003–2014. Using the Ne values obtained from measurements made with the Norilsk digisonde during this period, we analyze Ne variations during geomagnetic disturbances in spring and fall for a long period of time. We determine the effect of spring-fall asymmetry occurring in all solar activity phases and manifesting itself in a significant decrease in the electron density during the main phase of fall storms at all heights in comparison with quiet days: up to 2.6 times at a height of 200 km and slightly less at lower heights. This phenomenon is not observed during spring disturbances: Ne variations are much weaker.

Electron density at F1-layer heights in the last solar minimum (2007–2009)

We present the results of the analysis of annual variations in daily electron density (N) at heights 140–160 km for the last solar minimum (2007–2009) obtained from digisonde measurements at the ionospheric station Irkutsk (52 °N, 104 °E). New coefficients of the known semi-empirical model (SEM) describing the connection between N and thermospheric characteristics are calculated to identify regularities of these variations. We have revealed that a characteristic feature of the annual N variations during the solar minimum is a change in their phase by 180° in a relatively narrow altitude interval (170–180 km). These results and the new SEM coefficients are original and important for atmospheric and ionospheric physics.