Ionospheric Impact Response Analysis by Regional Information Integration

The space surrounding Earth is strongly influenced by the solar wind, a stream of charged particles coming from the Sun. Although the Earth's magnetic field shields the planet from the solar wind, some of the impinging energy gets transferred to the magnetosphere, powering a range of phenomena in near-Earth space such as the aurora. The aurora is produced as charged particles spiral down along magnetic field lines and collide with gases in the Earth's upper atmosphere, causing the emission of light. The aurora are the most visible part of a complex system of dynamics that also includes electric currents, magnetic disturbances, plasma winds, and neutral winds, which all vary in response to changes in the solar wind. The coupled dynamics of this system remains poorly understood, even though it takes place only about 100?500 km above us in the ionosphere. The changing ionosphere affects our lives through changes in satellite drag, rapid variations in magnetic field disturbances on ground which can lead to power outages, and the modification of radio waves which affects GPS accuracy. In the IIRARII project we develop new techniques to combine several different types of measurements to map ionospheric electrodynamics in regions with high data density. We have developed a technique called "Local mapping of polar electrodynamics (Lompe)". The Lompe technique is based on work that we have performed in connection with a new satellite project: Electrojet Zeeman Imaging Explorer (EZIE). In the end of 2020, EZIE was selected by NASA for launch in 2024. UiB and the IIRARII project plays a central role in this satellite project. In the spring of 2021 we published a paper that explains how we plan to use EZIE measurements to map electric currents in space. In 2023, we also published an article on how this technique can be optimized, and how to calculate the spatial resolution in the maps. This work was led by PhD student Michael Madelaire. Additionally, PhD student Simon Walker published a study that uses the EZIE technique on ground magnetometer measurements from the Nordic countries to create a 20-year long time series of electric currents in space.

The IIRARII project aims to determine how ionospheric conditions affect transient geospace phenomena. We will achieve this aim by developing new regional data assimilation techniques to maximize the output from dense networks of ionospheric measurements. These techniques will be used to derive maps of ionospheric electrodynamics at high time resolution, which will enable us to address the dynamics of magnetosphere-ionosphere-thermosphere coupling in a completely new way. We will apply the regional data assimilation techniques in events characterized by rapid changes in the magnetosphere, specifically substorms and times of rapid increases in the solar wind dynamic pressure. The ionospheric response to such changes is expected to vary significantly between seasons, since sunlight changes the ionization, and therefore the coupling between plasma and the neutral atmosphere. To address this poorly understood fundamental issue in space physics, we will answer the following questions: How does the ionospheric current system develop during substorms, and how does it depend on seasons? How does ionospheric convection develop during substorms, and how does it depend on seasons? How does ionospheric convection and currents develop after a solar wind pressure increase, and how does it depend on seasons? Finally, we will expand the regional data assimilation techniques, which are based on a 2D description of the ionosphere, to 3 dimensions. The 3D regional data assimilation technique will help achieve full science return from the upcoming EISCAT_3D radar, which will provide volumetric imaging of ionospheric parameters in its field of view. All techniques that are developed in the project will be implemented in Python, and made freely available.