Overview

Project Highlights:

  • Use of novel satellite and analysis techniques to monitor the coupled solar wind-magnetosphere-ionosphere-atmosphere system
  • Quantification of energy deposition in the upper atmosphere over a solar cycle
  • Repercussions for downward energy transport to the troposphere

The electrodynamic interaction between the solar wind and the Earth’s magnetosphere results in ~1 teraWatt of energy being deposited in the polar regions of the ionosphere and upper atmosphere through Joule heating.  The coupling is mediated by a complex electrical current system that connects the atmosphere with interplanetary space [e.g., Milan et al., 2016].  Despite the energy being deposited in the upper atmosphere (above 100 km), it has been found to influence atmospheric geopotential height [Boberg and Lundstedt, 2003] and surface air temperature [Seppälä et al., 2009; Baumgaertner et al., 2011].  Finding the causal mechanism for the downward coupling of this solar-terrestrial interaction, and determining the implications for climate change modelling, is hampered by a lack of comprehensive understanding of the energy deposition at high altitude.  This project will employ novel measurement and analysis techniques to quantify the temporal and spatial variations in the Joule heating and related electrodynamic properties of the interaction.

The rate of energy deposition is expected to depend on many factors, including the level of solar illumination of the polar regions, the speed of the solar wind flow, the strength and orientation of the interplanetary magnetic field carried from the Sun, and complex dynamical processes within the magnetosphere-ionosphere-atmosphere system; these factors vary on a wide range of timescales that encompass the characteristic response time of the magnetosphere to solar wind disturbances (minutes to hours), the rotation rate of the planet, the solar rotation rate (27 days), seasonally, and the solar cycle (11 years).  Of particular interest is the recent unexpected discovery that the coupling currents are significantly stronger in the northern hemisphere than in the southern hemisphere, with implications for whole atmosphere dynamics, for reasons as yet unknown [Coxon et al., 2016].

The project will incorporate data from a large array of satellite and ground-based observatories to produce the first complete record of the temporal and spatial fluctuations of ionospheric Joule heating over a complete solar cycle.  A key aim is to understand the hemispheric asymmetry of the energy deposition.  This dataset will be used to quantify the importance of solar-terrestrial coupling for whole atmosphere dynamics.

Artist’s impression of the electrical current system that links the magnetosphere and ionosphere, produces the Northern and Southern Lights, and is responsible for depositing ~1 teraWatt of energy in the upper atmosphere.

Methodology

The datasets used to determine global Joule heating rates will include observations from the 66 polar-orbiting satellites of the Iridium telecommunications constellation, ionospheric flow measurements from the 31 coherent radars of the Super Dual Auroral Radar Network (SuperDARN), auroral imagery from the SSUSI cameras onboard three satellites of the Defense Meteorological Satellite Program (DMSP), and ground magnetometer data from the SuperMAG network.

The Iridium data will be combined using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) method to monitor the global pattern of magnetosphere-ionosphere coupling currents [Anderson et al., 2000].  The project will develop a new analysis technique, based upon the spherical elementary current system (SECS) approach of Amm [1997] and Amm and Viljanen [1999], to invert the AMPERE data into separate electrodynamic properties including ionospheric electric fields and conductances, from which Joule heating can be computed.  Ground-truth will be provided by ionospheric electric field measurements from SuperDARN, estimates of aurorally-produced conductance from DMSP, and ground magnetic perturbations from SuperMAG.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. 

The project will build upon 20 years of experience within the Radio and Space Plasma Physics (RSPP) group at the University of Leicester in combining ground- and space-based observations of geophysical phenomena, and the design, operation, and exploitation of ionospheric radars.  Training in relevant plasma and atmospheric physics and radar techniques will be provided, as well as training in computer programming, data analysis, and inversion techniques required.  The student will gain expertise in research methods, data management, analytical thinking and computer programming.

Timeline

Year 1: Familiarisation with the research literature and atmospheric and ionospheric physics.  Training in computer programming and data visualisation.  Initial studies with AMPERE, SuperDARN, DMSP, and SuperMAG data.

Year 2: Development of inversion technique for analysis of AMPERE data, and quantification of Joule heating rates.

Year 3: Investigation of Joule heating rate dependence on solar and illumination conditions, and ramifications for downward transport of energy. Throughout the duration of the project the student will be expected to publish their work in refereed journals and present their findings at both national and international meetings.

Partners and collaboration (including CASE)

The project will require wide collaboration. As the PI institute of SuperDARN, Leicester has strong links with the PI institutes of the 30+ constituent radars around the world.  The project will also require close links with the PIs of AMPERE (B. J. Anderson), DMSP SSUSI (L. Paxton), and SuperMAG (J. Gerloev), all at the Johns Hopkins University Applied Physics Laboratory (JHU/APL).

Further Details

Prof Steve Milan,steve.milan@le.ac.uk, 0116 223 1896

Dr Suzie Imber, si88@le.ac.uk, 0116 223 1302