Feasibility of a Swarm Ionospheric Scintillation (SWIS) proxy for L-band scintillation

We report about the early implementation of SWIS (Swarm Ionospheric Scintillation): a Swarm-based proxy of amplitude scintillation strength on L-band signals through an S4 index. We leverage: (i) on the plasma density data provided by the high-resolution faceplate measurements at a 16 Hz sampling rate made by the EFI onboard Swarm satellites; (ii) on Rino’s theory for weak scattering regime, which adopts a power law phase screen to enable modelling of amplitude scintillations; and (iii) on the reconstruction of the irregularity layer based on the application of the NeQuick2 model, in a data ingestion scheme. This procedure is inspired by the WAM model approach for high-latitudes and for low-latitudes. The density estimates made by Swarm will be used to reconstruct a key-parameter, which is the value of the one-dimensional spectral slope p of the power spectrum of the plasma density irregularities measured in situ. The 16 Hz sampling rate, combined with the Swarm orbital features (speed ~7.5 km and quasi-polar orbits), will allow modelling the effect of spatial scales having a typical scale size of about 500 m along the Swarm flight direction (roughly N-S), which are slightly above the Fresnel’s scale relevant for L-band scintillations (few hundreds of metres) affecting the propagation of GNSS signals. The use of the SWIS proxy for scintillation is potentially of great use for the community involved in studying, monitoring, and modelling the impact of small-scale irregularities on GNSS signals in the space weather context as it complements and extends the information based on ground-based observations, also by covering ionospheric sectors scarcely covered by ground scintillation data, including remote areas and over the oceans, being not easily accessible. We report about its early implementation and testing against ground-based Ionospheric Scintillation Monitor Receivers.