The transfer of solar wind energy into the upper atmosphere through magnetospheric waves

The interaction between the Sun's and the Earth's plasma environments is very dynamic and one of societal and commercial importance. A large proportion of the energy from this terawatt system is transferred from the outer magnetosphere inwards by magnetohydrodynamic (MHD) waves, which propagate in the magnetospheric plasma along magnetic field lines into the upper atmosphere (ionosphere). There, the energy is dissipated through frictional (Joule) heating and energetic particle precipitation (EPP). Fig. 1 presents an overview of the system of interest. By undertaking this study, the student will be able to gauge the impact of geomagnetic activity on the near-Earth space environment. "Space Weather" hazards are now part of the Government's National Risk Register since geomagnetic storms are known to affect human activities on the ground and in space.

The Radio and Space Plasma Physics (RSPP) group at the University of Leicester has unique UK access to a number of important data sets including those from satellites (e.g. the Van Allen Probes, VAPs and the recently launched Japanese Arase mission), ionospheric radars (including SuperDARN and EISCAT) and ground magnetometers (through SuperMag).

MHD waves can be broadly categorised as being externally (solar wind) driven or excited through wave -particle interactions between the Earth's magnetic field and drifting plasma in the van Allen belts. The NASA VAPs mission will observe waves in the magnetosphere and the JAXA Arase mission can determine the flux of EPP entering the upper atmosphere, whilst the NASA Wind spacecraft monitors the solar wind driver for context. The data collected will provide input to up-to-date models of MHD wave generation and solar forcing of the atmosphere. The electric fields associated with MHD waves drive the ionosphere into motion, which is directly measurable by radars such as EISCAT and SuperDARN using techniques pioneered at Leicester. Simultaneously, externally-excited waves (with large scale sizes) are also readily detected by ground magnetometers (SuperMag) whereas particle-driven (smaller scale) waves are more easily observed within the ionosphere and magnetosphere.

Initially, an examination of upstream solar wind (Wind) data will be undertaken to determine magnetospheric drivers and these will be combined with measurements within the magnetosphere (VAP and Arase) to provide a way of determining how the MHD waves are generated and estimates of energy and EPP fluxes which are delivered to the upper atmosphere. A database of events and their characteristics will be derived. These will be compared with existing models of MHD waves.

The observations will be exploited in conjunction with contemporaneous measurements from the EISCAT and SuperDARN radars (including a new digital radar being deployed in Finland in 2021) to provide a detailed picture of the ionospheric conductivity, electrodynamics and EPP occurring during events identified. In addition, the student will utilise a newly developed analysis method (based on the Lomb-Scargle periodogram) to examine the MHD wave signatures in both the SuperDARN measurements and in ground magnetometer data provided by SuperMag. Ultimately, the student will determine the energy pathways from the solar wind into the ionosphere and provide accurate estimates of the total energy transferred through these routes.

The project will build upon over 40 years of experience within the Radio and Space Plasma Physics (RSPP) group in the exploitation and analysis of geophysical data and combining ground- and space-based observations of Space Weather phenomena. Training in relevant plasma and atmospheric physics and radar techniques will be provided as well as training in computer programming, model simulations and the data analysis required. The student will gain a great deal of expertise in research methods, data management, analytical thinking and computer programming.