Multi-Scale Irregularities Product for Space Weather Applications Utilizing High-Resolution Swarm Plasma Density Data

The Earth’s ionospheric dynamics are of multi-scale in nature, and the small-scale phenomena have been difficult to measure by in-situ techniques because of low data resolution. In this paper, we make use of 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. The new data is named as MUlti‑Scale Irregularities produCt (MUSIC) dataset. 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, from late 2014 to the end of 2025, the available data from Swarm A amounts to about eight years. 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 ±60º 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, with the variations attributed to the seasonal variations of the E region conductance in the polar regions. 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. The MUSIC dataset is now available through the Swarm dissemination server at https://swarm-diss.eo.esa.int/#swarm/Advanced/Plasma_Data/TDS_EFI_MUS_FP.