Bottomside ionospheric density monitoring and reconstruction with SuperDARN HF radars
Abstract
High-frequency (HF) communication systems have found a wide range of amateur, commercial, and military applications due to the low power requirements and long-distance nature of the "sky-wave" propagation mode. HF radio waves are refracted as they traverse electron density gradients in the ionized region of Earth s upper atmosphere, known as the ionosphere, potentially reflecting back and forth between the ionosphere and ground out to ranges of several thousand kilometers. However, the ionosphere is a dynamic environmentcontinually responding to space weather effects which can strongly influence propagation of HF radio signals. Specifically, it is the bottomside region of the ionosphere (i.e. below the F-layer density peak) in which HF communication links are susceptible to space weather phenomena associated with particle precipitation and plasma transport processes.The bottomside ionosphere is not easily accessible for in-situ measurements because of thermospheric drag which limitsthe orbital lifetime of low-altitude spacecraft. Remote sensing techniques have therefore been applied to estimate the electron density within this altitude regime; these include vertical and oblique radio soundings from ionosondes, incoherent scatter radar (ISR) observations, and inversion of all-sky airglow imagery. Each of these techniques has its own limitations, often in terms of either spatial coverage or operational costs. Recent advances have also been made in ionospheric electron density reconstruction using total electron content (TEC) measurements between ground-based receivers and space-based Global Navigation Satellite System (GNSS) constellations, however these TEC inversions often have limited altitudinal resolution in the bottomside ionosphere. Ionospheric models, such as the International Reference Ionosphere (IRI), often provide only climatological density profiles and are therefore insufficient for capturing daily space weather variability.The goal of this proposal is to leverage existing infrastructure to resolve two-dimensional electron density structure over spatial scales not available from single-point, vertical incidence observations. The Super Dual Auroral Radar Network (SuperDARN) consists of more than 30 high frequency radars in both the Northern and Southern Hemispheres routinely operating in the 8-20 MHz frequency band to produce global maps of ionospheric plasma motion. By utilizing the down-time available at the end of each standard 1-minute "convection mode" scan, SuperDARN radars can function as an oblique backscatter sounder to sample the bottomside ionosphere out to ranges of more than 1,000 km with a temporal resolution of 10-30 min. We propose to develop and apply backscatter inversion techniques to produce downrange estimates of the bottomside ionospheric density profile along each radar beam direction. We will compare and validate the results of our bottomside ionosphere inversion against vertical electron density profiles measured by ionosondes, as well as fromincoherent scatter radars, where available. Comparisons will also be made between the SuperDARN-derived profiles and ionospheric models, such as IRI and the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM).Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 24, 2023
- Source ID
- N000142312109
Entities
People
- E. G. Thomas
Organizations
- Board of Trustees of Dartmouth College
- Office of Naval Research
- United States Navy