# Diagnostics of plasma in the ionospheric D-region: detection and study of different ionospheric disturbance types

## TL;DR

This paper reviews methods for detecting and studying various ionospheric disturbances using VLF/LF radio waves, focusing on their classification, detection techniques, and analysis of perturbations caused by solar activity, earthquakes, and other events.

## Contribution

It introduces new detection procedures for ionospheric disturbances in time and frequency domains based on VLF/LF signal analysis.

## Key findings

- Detection of long-lasting perturbations from solar X-ray flares
- Identification of short-term disturbances from gamma-ray bursts
- Analysis of ionospheric signals post-earthquake events

## Abstract

Here we discuss our recent investigations of the ionospheric plasma by using very low and low frequency (VLF/LF) radio waves. We give a review of how to detect different low ionospheric reactions (sudden ionospheric disturbances) to various terrestrial and extra-terrestrial events, show their classification according to intensity and time duration, and present some methods for their detections in time and frequency domains. Investigations of detection in time domain are carried out for intensive long-lasting perturbations induced by solar X-ray flares and for short-lasting perturbations caused by gamma ray bursts. We also analyze time variations of signals used in the low ionospheric monitoring after earthquake events. In addition, we describe a procedure for the detection of acoustic and gravity waves from the VLF/LF signal analysis in frequency domain. The research of the low ionospheric plasma is based on data collected by the VLF/LF receivers located in Belgrade, Serbia.