Plasma and Space Physics
Space Physics at Dartmouth
Space Physics at Dartmouth consists of experimental and theoretical research groups in Physics and Astronomy and at the Thayer School of Engineering, which study the near Earth space environment, including phenomena such as the Northern (and Southern) Lights and the Van Allen radiation belts. Our dynamic variable star, the Sun, with an 11-year cycle of sunspot activity, drives phenomena in the Earth's atmosphere, ionosphere and magnetosphere, the cavity which the Earth's magnetic field carves out in the Sun's expanding atmosphere or solar wind. The experimental groups in Physics and Astronomy (LaBelle, Lynch, Millan) measure waves, energetic charged particles and x-rays using ground-based, rocket and balloon platforms, while theoretical and computational modeling of "space weather" and magnetospheric processes is carried out by Denton, Kress, Hudson, Lyon, Müller and students. Fundamental plasma physics processes creating disruptions in fusion plasmas also cause solar flares and create night-time "explosions" of aurora across the polar sky. The phenomenon of "magnetic reconnection" which converts magnetic field energy into particle kinetic energy is the focus of Roger's group.
Mary Hudson studies space weather patterns that originate from solar eruptions following energy and mass transfers through the interplanetary medium all the way the the Earth's ionosphere. Current investigations focus on the evolution of the Van Allen radiation belts.
Barrett Rogers's space physics research focuses on the physics of magnetic reconnection, particle acceleration, global magnetosphere simulations, turbulent cascades, and fluid and kinetic simulations of plasma instabilities.
James LaBelle's research focuses on measurements of plasma waves using NASA sounding rockets and ground-based radio techniques to remotely sense ionospheric plasma processes. The ground-based research is deployed at remote locations including Antarctica, Greenland, Alaska and Northern Canada. LaBelle has active collaborations with groups in North America and Europe.
Kristina Lynch's research focuses on the plasma physics of the Northern Lights. She uses the lower ionosphere as a laboratory for studying interactions between plasmas and probes, between the magnetosphere and the ionosphere. In the laboratory, her students can generate an ionospheric-like plasma in a large vacuum chamber called "the Elephant".
Robyn Millan's research focuses on energetic particles in astrophysical settings. Millan's current experiment (BARREL) will study the Earth's radiation belts using a flotilla of balloons launched from Antarctica.
Research and Adjunct Faculty
Bill Lotko's research within the broader field of geospace science focuses on system-level studies of the solar wind-magnetosphere-ionosphere interaction, its plasma electrodynamics, magnetohydrodynamics, and collisionless transport processes, with applications to space weather prediction.
John Lyon developed the Lyon-Fedder-Mobarry 3D global MHD code for simulation interaction of the Earth's ionosphere and magnetosphere with solar wind plasma. It includes multiple ion species and is coupled to an ionospheric model developed at the National Center for Atmospheric Research and to the Rice Convection Model of the inner magnetosphere. It is now available for runs on demand at NASA's Community Coordinated Modeling Center and is used by researchers worldwide.
Hans Müller investigates the heliosphere, the cavity which the solar wind carves out in the surrounding interstellar medium. With large-scale plasma and neutral kinetic simulations, he explores the physics of the heliosphere, in particular the heliospheric boundaries beyond the planetary system and the entrance of the neutral component of the interstellar gas into the heliosphere. These same tools are also applied to the study of stellar winds elsewhere in the Galaxy.
Plasma Research at Dartmouth
Research in the physics of plasmas and fluids is carried out by Professor Barrett Rogers and Emeritus Professor David Montgomery, and includes studies of nonlinear magnetohydrodynamics and turbulence in plasmas and fluids, investigations of magnetic reconnection, the physics of fusion devices, analytical dynamics, computational physics, plasma simulation, and plasma theory. The department also has a large vacuum calibration and test system for quantifying the response of particle detectors flown on auroral sounding rockets to the space environment, including a plasma source. Further details are described under Professor Kristina Lynch's rocket lab.
Through the efforts of an an international fusion research program, dramatic progress has been made in recent years toward the goal of confining a fusion-grade plasma in the laboratory using intense magnetic fields. The performance of these fusion devices is typically limited by a host of instabilities, which produce turbulence and degrade the confinement of particles and thermal energy. Research on this topic at Dartmouth (Rogers and Montgomery) is focused on understanding the physics of these instabilities as well as the turbulence and transport that they produce. This work relies heavily on both analytic methods as well as state-of-the-art massively parallel numerical simulations.
Professor Barrett Rogers's research is focused on theoretical and computational plasma physics and addresses topics such as basic plasma physics, magnetic reconnection, plasma turbulence, particle acceleration, instabilities, magnetic fusion, and plasma astrophysics of the present and early universe.
Space and laboratory plasmas such as the sun, the magnetopshere, and laboratory fusion experiments often store large quantities of energy in embedded magnetic fields. Magnetic reconnection is a ubiquitous process that can convert some fraction of this energy, often explosively, into high speed flows and thermal energy. Reconnection is the fundamental process underlying cataclysmic phenomena such as coronal mass ejections, magnetospheric substorms, and "sawtooth-crash'' reconnection in tokamak fusion reactors. The rapidity of such events is often so extreme that it has been an ongoing challenge to explain theoretically. Reconnection also generates intense electric fields that can accelerate particles to very high energies.
Turbulence is another ubiquitous feature of plasma systems. It can arise, for example, from non-uniformities in plasma flows, or be driven by instabilities arising from non-uniformities in the plasma density or temperatures. In magnetic fusion experiments, small-scale instabilities generate turbulence at small scales, which in turn transport plasma and heat from the core of fusion reactors to the walls. The convective losses generated in this way are among the greatest difficulties facing the design of a feasible fusion device.
Professor Montgomery's recent activities have included studies of:(1) the effect of an externally-imposed dc magnetic field's partial or total suppression of turbulent magnetohydrodynamic (MHD) dynamo action (see, e.g., D.C. Montgomery et al, Phys. Plasmas 9, 1221 (2002) and 6, 2727 (1999)); (2) the mass flows which necessarily arise in steady-state toroidal confinement devices for magnetic fusion plasmas (see, e.g., L.P. Kamp and D.C. Montgomery, Phys. Plasmas 10, 157 (2003)). The two figures below are taken from a 2004 Kamp/Montgomery paper, and show field lines (magnetic and mechanical streamlines) inside a toroid that is being Ohmically driven when viscous and resistive boundary conditions are being imposed. Both toroidal and poloidal flows necessarily result (see Kamp and Montgomery, J. Plasma Phys, 70, 113 (2004)) even in the laminar steady state; (3) together with P.D. Minninni (Buenos Aires) and L. Turner (Cornell), three-dimensional, spectral-method, magnetohydrodynamic computations of dynamos inside spherical shells have been carried out, with particular reference to the role that magnetic and mechanical helicity might play in the generation of planetary magnetic fields (the figure at the top of this page shows some computer graphics displaying typical evolving computed energy densities and field lines for mechanical and magnetic driven helical flows in the interior of the sphere (Mininni et al, New Journal of Physics 9, 303 (2007)); (4) maximum entropy predictions for the evolution of two-dimensional turbulent vortices both in a Malmberg-Penning electron trap and in numerical solutions of the neutral fluid dynamical equations have been in progress with an experimental group from the University of Delaware (e.g., see D.J. Rodgers et al, Phys. Rev. Letters 102, 244501 (2009)), and also in the completely unbounded case where the Oseen vortex has been shown to be the relaxed long-time state of a compact vorticity distribution with circulation in the absence of boundaries (D.C. Montgomery and W.H. Matthaeus, Phys. Fluids 23, 075104 (2011).
- J.A. Morales, W.T.Bos, K.Schneider, and D.C.Montgomery, "Magnetohydrodynamically generated velocities in confined plasmas", Physics of Plasmas 22, 042515-042532 (2015).
- J.A. Morales, W.T. Bos, K.Schneider, and D.C. Montgomery, "The effect of toroidicity on reversed field pinch dynamics", Plasma Physics and Controlled Fusion 56, 095024-095031 (2014).
- Jorge A. Morales, Wouter J.T. Bos, Kai Schneider, and David C. Montgomery, "Intrinsic Rotation of Toroidally Confined Magnetohydrodynamics", Physical Review Letters 109, 175002 (2012).
- D. J. Rodgers,1 S. Servidio, W. H. Matthaeus,1 D. C. Montgomery, T. B. Mitchell,* and T. Aziz, "Hydrodynamic Relaxation of an Electron Plasma to a Near-Maximum Entropy State" Phys. Rev. PRL 102, 244501 (2009).
- D. J. Rodgers,1 S. Servidio, W. H. Matthaeus,1 D. C. Montgomery, T. B. Mitchell,* and T. Aziz "Nonlinear Magnetohydrodynamics by Galerkin-method Computation" Phys. Rev. PRL 102, 244501 (2009).
- P.D. Mininni, D.C. Montgomery, and L.Turner "Hydrodynamic and magnetohydrodynamic computations inside a rotating sphere" New J. Phys. 9, 303(25 pages), 2007.
- D.C. Montgomery and W.H. Matthaeus, "Oseen vortex as a maximum entropy state in a two dimensional fluid," Phys. Fluids 23, 075104 (2011)
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