Radio Investigations for Space Environment Research (RISER)

The Earth's orbit is located within a dynamic and active interplanetary space environment where the Sun's atmosphere continually expands through the solar system (the heliosphere) to form the supersonic solar wind, which carries with it the interplanetary magnetic field. This magnetised wind continuously buffets the Earth's magnetic environment, producing space-weather effects which disrupt satellite communications and global positioning systems, are hazardous for technological infrastructures including satellites, power grids, and pipelines, and are potentially deadly for astronauts. Currently, only one hour of confirmed advance warning of the approach of adverse conditions is available provided by spacecraft directly measuring the interplanetary environment just in front of the Earth. The aim of the Radio Investigations for Space Environment Research (RISER) project is to reliably-increase that forecast time to up to four days by using a novel remote-sensing technique that allows the inner heliosphere's density and velocity structure to be imaged and assimilated into propagation models that track solar wind features and predict their arrival at the Earth. This technique uses the LOw Frequency ARray (LOFAR, the world's largest low-frequency radio-telescope) to detect radio signals from distance, astronomical radio sources, and to observe how these signals are made to twinkle (scintillate) as they pass through the turbulent heliosphere. This can also be accomplished for the Earth's ionised atmosphere (the ionosphere) to measure the impact of the Sun on Earth. The research within the RISER project is summarised as follows: 1. To investigate how to increase the robustness of the "interplanetary scintillation" (IPS) technique (twinkling of radio stars) using LOFAR, and how to upgrade LOFAR such that it can make continuous observations of the inner heliosphere (LOFAR for Space Weather, LOFAR4SW), while allowing its other scientific observations to continue simultaneously. 2. To optimise the assimilation of IPS data into propagation models that can forecast how the solar wind structures will evolve as they move through the inner heliosphere and the timing of their arrival at Earth. 3. Investigate comprehensive observations and measurements of the response of the Earth's space environment, and assess the impact of the heliospheric structures on the terrestrial environment: i.e. the "geoeffectiveness" of different heliospheric structures will be measured, indicating how hazardous they are for technological systems. Space weather is hazardous for many operators and end-users of technological systems. Reliable mitigation strategies for many of these technologies depend on accurate forecasting of the likely impact of space-weather conditions on operations. RISER will provide both improved forecasting and improved understanding of the impact of different heliospheric structures on geospace and technological systems within it. Improving advanced warning of approaching hazards from one hour to four days will be a major benefit to society. RISER shall indeed identify those results and model improvements that can be earmarked as strong candidates for eventual operational implementation at the Met Office. Therefore, with our holistic approach, this project aims to (A) investigate how LOFAR can be utilised for continuous and systematic tracking and detection of heliospheric structures; (B) advance the understanding of how the Earth's space-environment/ionised-atmosphere system responds to the interaction between heliospheric structures tracked through observations using LOFAR and the Earth's own magnetic field; (C) advance the capability of space-weather predictions by assimilating information from the continuous LOFAR tracking, the Earth space-environment response, and the impact caused to technologies on Earth; and (D) identify which RISER research outcomes can be exploited for improved operational space weather forecasts.