Space weather has a variety of effects on the ionosphere which is the charged component of the Earth's upper atmosphere lying between 80 and 1000 km. Depending on the processes involved, space weather causes the density of the ionosphere to be enhanced, depleted, or sometimes structured into both enhancements and depletions. Understanding and forecasting these effects is of great importance, because a variety of radio applications and sectors are affected by the ionosphere. For example, the military and civil aviation sectors use both high frequency (HF) signals, at frequencies between 3 and 30 MHz, and global navigation satellite (GNSS) signals, between ~1200 and 1600 MHz, for navigation. Both are sufficiently affected by the ionospheric medium that it has determined the system design and is a major day-to-day operational issue.
Our programme seeks to secure a step-change in the Met Office's (and more broadly the UK's) ability to specify and forecast the ionosphere. To achieve our objectives, we will leverage background IP from previous NERC, EPSRC and Dstl grants and contracts and explore new techniques. In the case of the leveraged IP we expect that all models will be at TRL 6 by the grant end and new research will be on a best efforts basis. We will achieve our objectives by benefitting from a five-institution consortium of some of the country's principal experts and, to maximise interchange of ideas, we will enhance the consortium by opening our technical meetings to other members of the wider UK and international community.
The majority of the programme will focus on environmental models, but while doing this we will maintain an awareness of the applications for these models, in particular aviation.
Lying at the heart of the SWIMMR-I delivery is the University of Birmingham's Advanced Ensemble electron density Assimilation System (AENeAS). This model is a coupled ionosphere-thermosphere physics-based data assimilation model and is based on a state-of-the-art variant of the ensemble Kalman filter. We believe that AENeAS is the only operationally-ready data assimilation model which has a fully physics-based underlying background model (ionosphere and thermosphere). As part of this programme AENeAS will be both operationalised and improved through a number of enhancements to its underlying data assimilation and boundary conditions using the Whole Atmosphere Community Climate Model (WACCM). The improved AeNeAS model will provide global maps of TEC and electron density, and in combination with developments of the University of Lancaster's D-region model, ODRAM, and developments of the University of Leicester's ray tracing expertise, will provide HF products to the aviation industry.
While these activities will enhance the UK's ability to model and forecast ionospheric enhancements and depletions, they will not directly address some of the major problems that GNSS systems have to face. These are due to gradients in the ionosphere and time dependent amplitude and phase variations on the signal, known as scintillation. Both effects will be addressed by a joint team from the Universities of Birmingham and Bath. The University of Bath will focus on a data driven approach appropriate to regions where there are many GNSS ionospheric receivers and the University of Birmingham will focus on two higher risk approaches. In one, the University of Birmingham will use satellite radio occultation measurements to localise and quantify scintillation, and in the other use AENeAS to make probabilistic predictions of when and where strong uplift of the equatorial plasma occurs, a predictor of equatorial scintillation. Both of these approaches are suitable for operation over poorly instrumented areas and consequently the potential benefits are high, but there are significant associated research challenges.