Leveraging Natural and Anthropogenic HF Noise as an Ionospheric Sounder
Abstract
Since the mid 20th century High Frequency (HF; 3-30 MHz) ionospheric sounders have primarily consisted of a transmitter and a receiver that sweep or step through a set of frequencies. The amount of time each frequency takes to travel to the ionosphere and back again (an ionogram) can be used to estimate the electron density profile of the bottom side ionosphere. Traditionally, noise sources such as lightning and powerline emissions in the HF band have a negative effect on a receivers signal to noise ratio (SNR). However, upon further inspection it is clear that these sources of noise possess the temporal and spectral qualities required for accurate sounding. We show that these noise sources can be reframed as signal sources using broadband measurements and a little bit of a priori information. For instance, intracloud lightning occurs at altitudes of a few km, and the HF noise can be measured up to 100s of km away. This pure amplitude waveform can easily be measured and then used as a reference signal for extracting the ionospheric reflection and thereby creating an ionogram. Similarly, the HF emissions from powerlines consists of a pattern of short broadband pulses that repeats at the grid operating frequency (60 Hz in North America). We give multiple examples of how the repeating qualities these signals can be leveraged to extract ionospheric parameters. Given the widespread nature of lightning and even more so electrical grids, these sources of noise provide an excellent opportunity for data driven ionospheric models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSA32A..03O