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Grant Stephens

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  • B.S., Astronomy and Astrophysics
    2009, Penn State
  • B.S., Physics
    2009, Penn State
  • M.S., Applied Physics
    2013, Johns Hopkins

The Earth’s magnetic field forms a protective cocoon from the solar wind called the magnetosphere. The magnetosphere is not a static structure and reacts to changes in the solar wind. For example, the Sun will occasionally emit a large bundle of magnetized plasma termed a coronal mass ejection or CME. When a CME sweeps past the Earth it can trigger a large magnetic disturbance throughout the magnetosphere called a geomagnetic storm. Another type of disturbance, substorms, occurs when a large amount of magnetic energy is stored on the nightside of the Earth which is suddenly released, accelerating particles toward the poles and lighting the night sky with the aurora. Both storms and substorms are important aspects of space weather and can have profound impacts on both spacecraft and astronauts. Grant Stephens’ research involves describing these events using data-driven models of the magnetosphere’s magnetic field and electric current systems. He employs data-mining methods to extract information on the dynamics of these systems from decades of spacecraft magnetometer measurements which then gets ingested into the model, forming a global picture of storms and substorms. Additionally, Grant has developed similar models for other planets such as Mercury and Saturn.

Scholarly Publications

Characteristics of Energetic Electrons Near Active Magnetotail Reconnection Sites: Tracers of a Complex Magnetic Topology and Evidence of Localized Acceleration

Geophysical Research Letters, 2021
Drew L. Turner, Ian J. Cohen, Samuel T. Bingham, Grant K. Stephens, Mikhail I. Sitnov, Barry H. Mauk, Richard E. Denton, Trevor W. Leonard, Joseph F. Fennell, J. Bernard Blake, Roy B. Torbert, James L. Burch, (2021), Characteristics of Energetic Electrons Near Active Magnetotail Reconnection Sites: Tracers of a Complex Magnetic Topology and Evidence of Localized Acceleration, Geophysical Research Letters , 48, 2, https://doi.org/10.1029/2020gl090089

Reconstructing Substorms via Historical Data Mining: Is It Really Feasible?

Journal of Geophysical Research: Space Physics, 2021
N. A. Tsyganenko, V. A. Andreeva, M. I. Sitnov, G. K. Stephens, J. W. Gjerloev, X. Chu, O. A. Troshichev, (2021), Reconstructing substorms via historical data mining: Is it really feasible?, Journal of Geophysical Research: Space Physics , https://doi.org/10.1029/2021ja029604

Reconstruction of Extreme Geomagnetic Storms: Breaking the Data Paucity Curse

Space Weather, 2020
M. I. Sitnov, G. K. Stephens, N. A. Tsyganenko, H. Korth, E. C. Roelof, P. C. Brandt, V. G. Merkin, A. Y. Ukhorskiy, (2020), Reconstruction of Extreme Geomagnetic Storms: Breaking the Data Paucity Curse, Space Weather , 18, 10, https://doi.org/10.1029/2020sw002561

Storm Time Plasma Pressure Inferred From Multimission Measurements and Its Validation Using Van Allen Probes Particle Data

Space Weather, 2020
G. K. Stephens, S. T. Bingham, M. I. Sitnov, M. Gkioulidou, V. G. Merkin, H. Korth, N. A. Tsyganenko, A. Y. Ukhorskiy, (2020), Storm Time Plasma Pressure Inferred From Multimission Measurements and Its Validation Using Van Allen Probes Particle Data, Space Weather , 18, 12, https://doi.org/10.1029/2020sw002583

Global Empirical Picture of Magnetospheric Substorms Inferred From Multimission Magnetometer Data

Journal of Geophysical Research: Space Physics, 2019
G. K. Stephens, M. I. Sitnov, H. Korth, N. A. Tsyganenko, S. Ohtani, M. Gkioulidou, A. Y. Ukhorskiy, (2019), Global Empirical Picture of Magnetospheric Substorms Inferred From Multimission Magnetometer Data, Journal of Geophysical Research: Space Physics , 124, 2, 1085--1110, https://doi.org/10.1029/2018ja025843

Signatures of Nonideal Plasma Evolution During Substorms Obtained by Mining Multimission Magnetometer Data

Journal of Geophysical Research: Space Physics, 2019
M. I. Sitnov, G. K. Stephens, N. A. Tsyganenko, Y. Miyashita, V. G. Merkin, T. Motoba, S. Ohtani, K. J. Genestreti, (2019), Signatures of Nonideal Plasma Evolution During Substorms Obtained by Mining Multimission Magnetometer Data, Journal of Geophysical Research: Space Physics , 124, 11, 8427--8456, https://doi.org/10.1029/2019ja027037

Calibration, Projection, and Final Image Products of MESSENGER's Mercury Dual Imaging System

Space Science Reviews, 2018
Brett W. Denevi, Nancy L. Chabot, Scott L. Murchie, Kris J. Becker, David T. Blewett, Deborah L. Domingue, Carolyn M. Ernst, Christopher D. Hash, S. Edward Hawkins, Mary R. Keller, Nori R. Laslo, Hari Nair, Mark S. Robinson, Frank P. Seelos, Grant K. Stephens, F. Scott Turner, Sean C. Solomon, (2018), Calibration, Projection, and Final Image Products of MESSENGER's Mercury Dual Imaging System, Space Science Reviews, 214, 1

Effects of electrojet turbulence on a magnetosphere-ionosphere simulation of a geomagnetic storm

Journal of Geophysical Research-Space Physics, 2017
M. Wiltberger, V. Merkin, B. Zhang, F. Toffoletto, M. Oppenheim, W. Wang, J. G. Lyon, J. Liu, Y. Dimant, M. I. Sitnov, G. K. Stephens, (2017), Effects of electrojet turbulence on a magnetosphere-ionosphere simulation of a geomagnetic storm, Journal of Geophysical Research-Space Physics, 122, 5, 5008-5027

Spatial Structure and Asymmetries of Magnetospheric Currents Inferred from High-Resolution Empirical Geomagnetic Field Models

Dawn-Dusk Asymmetries in Planetary Plasma Environments, 2017
Mikhail I. Sitnov, Grant K. Stephens, Nikolai A. Tsyganenko, Aleksandr Y. Ukhorskiy, Simon Wing, Haje Korth, Brian J. Anderson, (2017), Spatial Structure and Asymmetries of Magnetospheric Currents Inferred from High-Resolution Empirical Geomagnetic Field Models, Dawn-Dusk Asymmetries in Planetary Plasma Environments, 230 , 199-212

Determining shape of a seasonally shadowed asteroid using stellar occultation imaging

Planetary and Space Science, 2016
Scott L. Murchie, Hari Nair, Grant K. Stephens, (2016), Determining shape of a seasonally shadowed asteroid using stellar occultation imaging, Planetary and Space Science, 131, 24-32

Empirical modeling of the storm time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents

Journal of Geophysical Research-Space Physics, 2016
G. K. Stephens, M. I. Sitnov, A. Y. Ukhorskiy, E. C. Roelof, N. A. Tsyganenko, G. Le, (2016), Empirical modeling of the storm time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents, Journal of Geophysical Research-Space Physics, 121, 1, 157-170

Empirical reconstruction of storm time steady magnetospheric convection events

Journal of Geophysical Research-Space Physics, 2013
G. K. Stephens, M. I. Sitnov, J. Kissinger, N. A. Tsyganenko, R. L. McPherron, H. Korth, B. J. Anderson, (2013), Empirical reconstruction of storm time steady magnetospheric convection events, Journal of Geophysical Research-Space Physics, 118, 10, 6434-6456

Forecasting of global data-binning parameters for high-resolution empirical geomagnetic field models

Space Weather-the International Journal of Research and Applications, 2012
M. I. Sitnov, A. Y. Ukhorskiy, G. K. Stephens, (2012), Forecasting of global data-binning parameters for high-resolution empirical geomagnetic field models, Space Weather-the International Journal of Research and Applications, 10