Multi-Scale Irregularities Product: a data product utilizing the high-resolution Swarm plasma density data for space weather applications

TL;DR

This paper develops a high-resolution data product from Swarm satellite plasma density measurements to characterize ionospheric irregularities across different scales and conditions, aiding space weather research.

Contribution

It introduces a novel set of parameters derived from Swarm data to analyze multi-scale ionospheric irregularities, with statistical insights into their dependence on various geophysical factors.

Findings

High-latitude irregularities are persistent poleward of 60° magnetic latitude.

Low-latitude irregularities are prominent during 19-01 local time near the magnetic equator.

Spectral slope variations show seasonal patterns, peaking in local summer.

Abstract

We use the high-resolution Swarm faceplate plasma density data at 16 Hz to develop a set of parameters that can characterize multi-scale ionospheric structures and irregularities along the Swarm orbit. We present the methods for calculating density gradients over different window sizes, rate of change of density index, power spectral density and the spectral slope at both low and high latitudes. The faceplate plasma data are not continuously available through the years. However, about 8 years of data from Swarm A are processed from late 2014 to the end of 2025. Some statistical results from Swarm A are presented. The variations of plasma structures and irregularities are dependent on solar activity, season, local time and geomagnetic activities, and the variations show different patterns between low and high latitudes. For example, the high-latitude ionosphere is characterized by persistent ionospheric structures and irregularities poleward of 60 magnetic latitude, while the low-latitude ionospheric irregularities are only dominant during 19-01 local time near the magnetic equator. The occurrence of steep spectral slope at high latitudes shows clear seasonal variations, i.e., it maximizes during local summer and minimizes during local winter in both hemispheres. However, the occurrence of steep spectral slope at low latitudes is only sensible when significant plasma structures and irregularities are present. We further calculate the histogram of spectral slopes at low latitudes when the rate of change of density index is enhanced. The histogram resembles a Gaussian distribution with an expected value of 1.97. The processed data are available to the wider community. Given the high resolution, this new data product will be useful for the scientific communities that are interested in the magnetosphere-ionosphere-thermosphere coupling and near-Earth space environment.