Prof Tim Yeoman

photoProfessor of Magnetospheric Physics

B.Sc. (Bristol), D.Phil (York)

Tel: 0116 252 3564

Email: yxo@leicester.ac.uk

Office: Room F67, Physics and Astronomy

Miscellaneous links I find useful related to teaching and research can be found on my research group homepage

Personal details

B.Sc. (Bristol), D.Phil (York)

I graduated from the University of Bristol in 1985, and went on to the University of York, gaining a D.Phil. in the Physics of Ultra Low-Frequency waves observed in the Earth's magnetosphere in 1988.  I joined the University of Leicester as a PDRA that year, and joined the Academic staff here as a Lecturer, in 1992.  I was promoted to Reader in 2000 and was awarded a personal Chair in Magnetospheric Physics in 2007. I was Academic Director of the College of Science and Engineering from 2013-2016.

Websites

Miscellaneous links I find useful related to teaching and research can be found on my research group homepage

Teaching

Teaching activities, 2018-19:

· PA1120 Light and Matter

· PA2240 Electromagnetic Fields

· PA 3603 The Space Environment

· PA3280 Physics Challenge

 

I also regularly offer Pair Projects in the 3rd year, and Specialist Research Projects and Advanced Study projects in the 4th year.

 

Publications

Selected publications

  1. J. K. Sandhu, T. K. Yeoman, M. K. James, I. J. Rae, and R. C. Fear (2018). “Variations of high-latitude geomagnetic pulsation frequencies: A comparison of time-of-flight estimates and IMAGE magnetometer observations”. Journal of Geophysical Research: Space Physics. 2017JA024434,   http://dx.doi.org/10.1002/2017JA024434.
  2. A. G. Burrell, G. W. Perry, T. K. Yeoman, S. E. Milan, and R. Stoneback (2018). “Solar Influences on the Return Direction of High-Frequency Radar Backscatter”. Radio Science 53.4, pp. 577–597. URL: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017RS006512.
  3. M. K. James, E. J. Bunce, T. K. Yeoman, S. M. Imber, and H. Korth (2016). “A statistical survey of ultralow-frequency wave power and polarization in the Hermean magnetosphere”. Journal of Geophysical Research-Space Physics 121.9, 8755–8772. http://dx.doi.org/10.1002/2016JA023103.
  4. James, M. K., T. K. Yeoman, P. N. Mager, and D. Y. Klimushkin (2013), The spatio-temporal characteristics of ULF waves driven by substorm injected particles, J. Geophys. Res.: Space Physics., 118, 1737–1749, http://dx.doi.org/10.1002/jgra.50131.

Online Full (ish) publication list:

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Research

My research centres on the analysis and interpretation of data from spacecraft particle and field instruments and ground-based magnetometer and ionospheric radar data. Current research activities include:

ULF waves

Ultra low frequency (ULF) waves are an important coupling mechanism between the magnetosphere and the ionosphere since they transfer both energy and momentum. These processes are most significant in the high-latitude ionosphere, where the magnetosphere-ionosphere interaction is strongest. The waves also act as an important diagnostic of magnetospheric morphology and dynamics. High-frequency radio experiments, such as SuperDARN and spacecraft such as Cluster are providing exciting new information on ULF waves, and we also explore the ULF wave populations of other solar system bodies.

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Field line eigenfrequency (in mHz) mapped to the T96 equatorial plane and the AACGM field line footprint latitude in the northern hemisphere.  The time-of-flight approximation was used with T96 magnetic field and the Sandhu empirical plasma mass density models (from publication (1) above)

mercury-waves

Transverse waves mapped into the equatorial plane (left) of Mercury, and to the Mercury surface (right), separated into left handed and right handed polarisation. All polarisations are included on the top, and only the most circular polarisations on the bottom (from publication (3) above).

Solar wind-magnetosphere coupling

The large-scale transport of mass, momentum and energy into the Earth's magnetosphere-ionosphere system from the solar wind is mainly controlled by processes at the dayside magnetopause in the cusp region. These processes cause transient flows in the high latitude ionosphere, which can be studied with the SuperDARN radars, and auroral emissions which may be imaged from the ground, or by space-borne auroral imagers.  Recent research has greatly improved our understanding of the effects of the solar cycle on radar performance and measurements.

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(a) Solar cycle F10.7 and (b) Cosmic ray levels from 1996 to 2008. (c) noon and (d) midnight HF radar ground scatter occurrence from in front of and behind the Hankasalmi radar (from publication (2) above).

Magnetospheric substorms

Much of the energy which enters the Earth's magnetosphere through processes at the dayside magnetopause is eventually released into the nightside upper atmosphere through magnetospheric substorm processes.  High frequency (HF) ionospheric radars have proved to be a powerful technique for investigating the spatial and temporal development of the ionospheric conductivities and electric fields during the three phases of the magnetospheric substorm. New, multi-instrument studies are providing a new set of opportunities for understanding the complex dynamics of the nightside magnetosphere.

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Following substorm onset, waves are generated through collisionless wave-particle interactions by westward drifting energetic ions and eastward drifting energetic electrons (from publication (4) above).

 

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Department of Physics & Astronomy,
University of Leicester,
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