Interaction of electromagnetic waves and energetic charge particles in geospace plasma
Modeling of radiation belt dynamics
Instability and propagation of plasma waves
- Applications of plasma waves
The Earth’s magnetosphere, our geospace environment a few thousand kilometers above the Earth’s surface, consists of energetic charge particles trapped by the Earth’s magnetic field. Those energetic particles exhibit great variability due to solar activities, and pose a great threat to spacecraft orbiting in it and to astronauts. Understanding and predicting their variability are of great interest for space weather. A variety of naturally occurring electromagnetic waves, from Ultra Low Frequency to Very Low Frequency, play important roles in dynamics of those energetic charge particles, especially the radiation belts referring to population of electrons and protons with relativistic energy in geospace. The physical process involved is called wave-particle resonant interaction, where electromagnetic waves seen by particles match fundamental frequencies of trapped particles, leading to stochastic change in particles’ energy and momentum. My research interest is to study the nature of electromagnetic waves in our geospace and the effect of wave-particle interaction. We use various numerical simulation techniques to address the following questions, how are electromagnetic waves generated due to what kind of free energy, how do them propagate in complex geospace medium, where is the wave energy absorbed, how those waves affect energetic particles, and how do we model temporal evolution and spatial distribution of energetic particle population due to wave-particle interaction. These questions are the compelling science topics of the NASA’s $700M two-twin Van Allen Probes Mission. The mission, named after Dr. Van Allen who made the discovery of the radiation belts in 1958, was launched in 2012 August and aims at identifying fundamental mechanisms responsible for radiation belt loss and acceleration.
For more information on Van Allen Probes from NASA
or from youtube (search for “Van Allen probes”)
or from wiki
Chen, L., R. M. Thorne, and J. Bortnik (2011), The controlling effect of ion temperature on EMIC wave excitation and scattering, Geophys. Res. Lett., 38, L16109, doi:10.1029/2011GL048653. 2011 - Publication
Toshi Nishimura, Jacob Bortnik, Wen Li, Richard Thorne, Lunjin Chen, Larry Lyons, Vassilis Angelopoulos, Stephen Mende, John W. Bonnell, Olivier Le Contel, Christopher Cully, Robert E. Ergun, Hans-Ulrich Auster (2011), Multi-event study of the correlation between pulsating aurora and whistler-mode chorus emissions, J. Geophys. Res., 116, A11221, doi:10.1029/2011JA016876. 2011 - Publication
Li, W., J. Bortnik, R. M. Thorne, Y. Nishimura, V. Angelopoulos, and L. Chen (2011), Modulation of whistler mode chorus waves: 2. Role of density variations, J. Geophys. Res., 116, A06206, doi:10.1029/2010JA016313 2011 - Publication
Li, W., R. M. Thorne, J. Bortnik, Y. Nishimura, V. Angelopoulos, L. Chen, J. P. McFadden, and J. W. Bonnell (2010), Global Distributions of Suprathermal Electrons Observed on THEMIS and Potential Mechanisms for Access into the Plasmasphere, J. Geophys. Res., 115, A00J10, doi:10.1029/2010JA015687. 2010 - Publication
Chen, L., R. M. Thorne, V. K. Jordanova, and R. B. Horne (2010), Global simulation of magnetosonic wave instability in the storm time magnetosphere, J. Geophys.
Res., 115, A11222, doi:10.1029/2010JA015707. 2010 - Publication
Chen, L., R. M. Thorne, V. K. Jordanova, C. Wang, M. Gkioulidou, L. Lyons, and
R. B. Horne (2010), Global simulation of EMIC wave excitation during the 21 April
2001 storm from coupled RCM–RAM–HOTRAY modeling, J. Geophys. Res., 115,
A07209, doi:10.1029/2009JA015075. 2010 - Publication
Shprits, Y. Y., L. Chen, and R. M. Thorne (2009), Simulations of pitch angle scattering of relativistic electrons with MLT-dependent diffusion coefficients, J. Geophys.
Res., 114, A03219, doi:10.1029/2008JA013695. 2009 - Publication
Chen, L., R. M. Thorne, and R. B. Horne (2009), Simulation of EMIC wave excitation.
in a model magnetosphere including structured high-density plumes, J. Geophys..
Res., 114, A07221, doi:10.1029/2009JA014204. 2009 - Publication
Chen, L., J. Bortnik, R. M. Thorne, R. B. Horne, and V. K. Jordanova
(2009), Three dimensional ray tracing of VLF waves in a magnetospheric environment containing a plasmaspheric plume, Geophys. Res. Lett., 36, L22101, doi:10.1029/2009GL040451. 2009 - Publication
Xiao, F., L. Chen, H. Zheng, Q. Zhou, and S. Wang (2008) Propagation of Superluminous
L–O Mode Waves During Geomagnetic Activities Plasma Sci. Technol.
10, 546, doi:10.1088/1009-0630/10/5/05. 2008 - Publication