Imaging the D-Region Ionosphere Using VLF Network Observations and a Particle Filter

The electron density of the D-region ionosphere (60–100 km) plays a critical role in radio communications, navigation systems, and space environment monitoring. Despite its importance, this region remains difficult to observe. Traditional ground-based Very Low Frequency (VLF) monitoring typically relies on single propagation path measurements, yielding only path-averaged information. In this study, we image the D-region ionosphere using VLF network observations and a particle filter.

 

To address the non-linear and ill-posed problems inherent in D-region ionosphere inversion, we applied a particle filter algorithm to the reconstruction process. The numerical experiments demonstrate the efficacy of the particle filtering approach in D-region ionosphere imaging. Furthermore, we used this method to image the evolution of the D-region ionosphere during a solar eclipse and a solar flare. The results demonstrate the significant promise of the method for remote sensing the D-region ionosphere using VLF network observations, offering a new capability for monitoring the impacts of space weather events on the lower ionosphere.