Simon G. Shepherd

Research Interests

HF radar development; ionospheric plasma convection and physics; solar wind, magnetosphere, ionosphere coupling; space weather and climatology

Education

• BA, Physics, Middlebury College 1989
• MS, Mechanical Engineering, University of Washington 1991
• PhD, Physics, Dartmouth 1998

Research Projects

• Sub-auroral convection electric fields

  Sub-auroral convection electric fields

  Sub-auroral convection electric fields focuses on the study of ionospheric plasma convection in the plasmasphere boundary layer region where complex coupling between the ionosphere and magnetotail occur during geomagnetically disturbed periods. Measurements from the mid-latitude SuperDARN radars are used in conjunction with other ground and space-based observations of sub-auroral phenomena.

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• Convection electric field climatology and variability

  Convection electric field climatology and variability

  Convection electric field climatology and variability focuses on the large-scale convection of plasma in the Earth's polar ionospheres. Measurements from the SuperDARN network of HF radars are used to look at statistical properties of convection associated with various drivers as well as the observed small-scale variability.

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• Mid-latitude HF radar development

  Mid-latitude HF radar development

  A network of HF radars are being built at several mid-latitude locations to measure ionospheric electric fields. This project involves the construction, maintenance and operation of several HF SuperDARN radars that have recently been built or are in the planning stages.

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Selected Publications

• Sugimura R, Shiokawa K, Otsuka Y, Oyama S-i, Oksanen A, Connors M, Kadokura A, Poddelsky I, Nishitani N, Shepherd SG, et al. (2025) "Multi-event analysis of STEVE, SAR arc, and red/green arc at subauroral latitudes using data from ground optical and radio instruments and the Arase and Van Allen Probes satellites." Journal of Geophysical Research: Space Physics. 130: e2024JA032793. doi:10.1029/2024JA032793.
• Thomas EG, Shepherd SG, Kunduri BSR, Themens DR. (2024) "Multi-frequency SuperDARN HF radar observations of the ionospheric response to the October 2023 annular solar eclipse." Geophysical Research Letters. 51. doi:10.1029/2024GL112450.
• Kunduri BSR, Baker JBH, Ruohoniemi JM, Thomas EG, Huba JD, Emmons DJ, Themens DR, Sterne KT, Farinas Perez G, Bristow WA, Shepherd SG, Holmes JM, Dao EV, Chartier AT, Perry GW, Pandey K. (2024) "HF radar observations and modeling of the impact of the 8 April 2024 total solar eclipse on the ionosphere-thermosphere system." Geophysical Research Letters. 51: e2024GL112484. doi:10.1029/2024GL112484.
• Morita K, Ponomarenko P, Nishitani N, Hori T, Shepherd SG. (2024) "Polarization and m-number characteristics of mid-latitude Pc5 ULF waves observed by SuperDARN radars." Journal of Geophysical Research: Space Physics. 129: e2024JA032592. doi:10.1029/2024JA032592.
• Thomas EG, Shepherd SG, Chisham G. (2024) "Multi-frequency SuperDARN interferometer calibration." Radio Science. 59. doi:10.1029/2024RS007957.
• Perez Macho E, Bristow W, Gallardo-Lacourt B, Shepherd S, Ruohoniemi JM, Correia E. (2024) "Exploring the relationship between STEVE and SAID during three events observed by SuperDARN." Frontiers in Astronomy and Space Sciences, Section Space Physics. 11. doi:10.3389/fspas.2024.1422164.
• Kelley IJ, Kunduri BSR, Baker JBH, Ruohoniemi JM, Shepherd SG. (2023) "Storm time electrified MSTIDs observed over mid-latitude North America." Journal of Geophysical Research: Space Physics. doi:10.1029/2022JA031115.
• Bristow WA, Lyons LR, Nishimura Y, Shepherd SG, Donovan EF. (2022) "High-latitude plasma convection based on SuperDARN observations and the locally divergence free criterion." Journal of Geophysical Research: Space Physics. 127: e2022JA030883. doi:10.1029/2022JA030883.
• Wang Y, Jayachandran PT, Ma Y-Z, Zhang Q, Xing Z-Y, Ruohoniemi JM, Shepherd SG, Lester M. (2022) "Dependencies of GPS scintillation indices on the ionospheric plasma drift and rate of change of TEC around the dawn sector of the polar ionosphere." Journal of Geophysical Research: Space Physics. 127: e2022JA030870. doi:10.1029/2022JA030870.
• Shi X, Lin D, Wang W, Baker JBH, Weygand JM, Hartinger MD, Merkin VG, Ruohoniemi JM, Pham K, Wu H, Angelopoulos V, McWilliams KA, Nishitani N, Shepherd SG. (2022) "Geospace concussion: Global reversal of ionospheric vertical plasma drift in response to a sudden commencement." Geophysical Research Letters. 49: e2022GL100014. doi:10.1029/2022GL100014.
• Kunduri BSR, Baker JBH, Ruohoniemi JM, Thomas EG, Shepherd SG. (2022) "An examination of SuperDARN backscatter modes using machine learning guided by ray-tracing." Space Weather. 20. doi:10.1029/2022SW003130.
• Thomas EG, Shepherd SG. (2022) "Virtual height characteristics of ionospheric and ground scatter observed by mid-latitude SuperDARN HF radars." Radio Science. 57. doi:10.1029/2022RS007429.

News

Dartmouth Engineering Researchers Win DoD Funding for Critical Equipment Upgrades
Jan 11, 2024

SuperDARN in Iceland
Jan 27, 2023

Dartmouth Engineering Researcher Receives Early Career Award
Aug 09, 2019

Dartmouth researcher receives NSF grant to build radar systems for space science and engineering
Mar 06, 2011

In the News