An innovative new methodology for assessing the effect of space weather on radio signals in the ionosphere has been published in the journal Radio Science.
Researchers from The University of Manchester’s Jodrell Bank Centre for Astrophysics have developed and demonstrated a process for continuous electron density measurement of the previously under-explored D region of the ionosphere — a part of the atmosphere that previously could only be sensitively probed by short-lived rocket-borne instruments.
Accurate and up to the minute data on the interaction between space weather and electron density is vital to maintain services that utilise radio signals — everything from the Global Position System (GPS) used in smart phones, aircraft navigational systems through to the astronomical signals received by radio telescopes.
The new study combined a statistical approach implemented in a unique software modeling programme called IONONEST with data from the Kilpisjärvi Atmospheric and Imaging Receiver Array (KAIRA) radio telescope in Finland, which is capable of making sensitive broadband measurements of the absorption caused to the cosmic radio background by the ionsophere. The resulting data confirmed the process was a successful methodology for measuring the effect of solar weather, the changes it caused to the ionosphere and the resultant impact on radio signals.
Dr Anna Scaife, Head of the Interferometry Centre of Excellence at The University of Manchester and one of the study’s authors, said: “From sitting in a converted train carriage in the frozen north of Finnish Lapland repurposing the KAIRA telescope to crunching data through IONONEST, we have used the technology in new and innovative ways that can really push this science forward. Our aim with this project was to develop ionospheric techniques that can be used more widely by researchers across the world.
“Unlike other methods of measuring the lower ionosphere, the techniques we have developed can be run effectively continuously — providing a long term database that can be used as a basis for ionospheric predictions — and the provision of services for both consumers and scientists that rely on accurate and stable radio wave activity, bridging the gap between science and society.”
The electron density in the D-region is substantially less well understood than the other layers of the ionosphere, and cannot be measured effectively via the most common methods used for observing the ionosphere, such as ionosondes, incoherent scatter radar and GPS networks. Prior to the IONONEST methodology, the primary method to measure electron density height profiles in the D-region was the use of rocket-borne instruments which provide direct observations, however this method is expensive and only produces a single set of data per flight. The use of incoherent scatter radar is limited because the technique is less sensitive than using rocket-borne instruments as well as being both expensive to build and limited in latitude coverage.
The IONONEST methodology uses a statistical technique called nested sampling to invert the multi-frequency data recovered by KAIRA and recover parameterised height profiles of the electron density through the D-region of the ionosphere. The technique is capable of both constraining the optimal parameters of these models as well as statistically selecting the best model from a set. Since the KAIRA telescope is built on the same technology as the larger distributed European radio telescope LOFAR, the IONONEST code can be used directly to perform ionospheric measurements from any LOFAR station.