Use of Terrestrial High Frequency Signals in Riometer Data to Explore the Size of D‐Region Electron Density Enhancements

This paper presents the first observations from the prototype Space Weather Adaptive Network (SWAN) riometers, which are capable of simultaneous measurements of narrow‐band terrestrial signal power and Cosmic Noise Absorption (CNA). We describe a methodology by which we can use coincident CNA and loss of known skywave‐mode, High Frequency (HF) signals to estimate a minimum size (geographic extent) of D‐region electron density enhancements. We demonstrate our technique with an example event. This methodology and early results provide a pathfinder for a continent‐wide array of SWAN instruments which would be capable of utilizing multiple intersecting terrestrial HF ray paths to reconstruct the size of D‐region electron density enhancements at the time of initial HF signal loss. Key Points Simultaneous cosmic noise absorption and terrestrial High Frequency signal loss can be used to infer the size of D‐region enhancements The technique described here can be scaled up to network‐level providing a mechanism to resolve spatial scales of D‐region enhancements