Bill Lotko headshot2

William Lotko

Sue and John Ballard '55 TT'56 Professor of Engineering, Emeritus

Professor Lotko discusses his research in space weather prediction and his approach to teaching at Dartmouth.

Education

  • BS, Engineering Physics, University of Kansas 1973
  • MS, Physics, University of Missouri 1976
  • PhD, Physics, University of California, Los Angeles 1981

Research Interests

Geospace environment; space plasma physics, modeling, simulation; magnetohydrodynamics; electromagnetic fields and waves

Selected Publications

Awards

  • Fellow, American Geophysical Union

Research Projects

  • Computational plasma dynamics

    Computational plasma dynamics

    Computational plasma dynamics focuses on the development of computer models for diagnosing and predicting plasma, magnetofluid, and electromagnetic processes in the near-earth space environment.

  • Geospace environment modeling

    Geospace environment modeling

    Geospace environment modeling research focuses on the development of computer models and satellite- and ground-based data streams for diagnosing and predicting plasma, magnetofluid, electromagnetic and radiation processes in geospace, including Earth's magnetosphere and ionosphere. Geospace encompasses the aerospace environment for hundreds of communication, navigation, meteorological, military, remote sensing, and research satellites.

  • Dynamics of magnetosphere-ionosphere coupling

    Dynamics of magnetosphere-ionosphere coupling

    This project addresses the NASA Roadmap challenge to explain, model and predict “how mass and energy flows in the magnetosphere-ionosphere (MI) system determine and control their coupled behavior.” It takes a critical step in integrating theoretical and empirical knowledge of the three key agents of dynamic MI coupling – energy deposition, electron precipitation, and ion outflows – to improve our ability to predict regional and global dynamics of geospace. The primary research objectives are to determine:

    1. How these individual elements interact to regulate their collective behavior
    2. How they determine and control the MI interaction
    3. How they impact the greater solar wind – magnetosphere - ionosphere interaction over the spectrum of interplanetary driving conditions

    Global simulation models are being developed to study the effects of solar wind-magnetospheric dynamics on low-altitude energy deposition, and the effects of ionospheric activity on the magnetosphere including scale-interactive transport of magnetic flux, mass, and energy. The models treats the 1) global multifluid-magnetohydrodynamics of the solar wind-magnetosphere-ionosphere interaction; 2) global thermosphere-ionosphere electrodynamics and circulation; and 3) electrodynamic and kinetic linkages involving quasistatic and Alfvén wave dynamics, ionospheric outflows, and electron precipitation in the collisionless MI “gap region.”

    This project is funded by a grant from NASA.

  • Magnetohydrodynamics

    Magnetohydrodynamics

    Magnetohydrodynamics (MHD) is a combination of fluid mechanics and electromagnetics concerned with the motion of electrically-conducting liquids and gases in the presence of a magnetic field. Examples of technical applications are electric power generation, electromagnetic pumping and propulsion as well as control of moving molten metals. MHD research at Thayer School is concerned with the high-speed flow of tenuous, ionized gas from the Sun past the Earth's magnetic field. The research is fundamental in nature but also contributes to the development of a national space-weather forecasting capability. This capability is important for the safe operation of manned spacecraft and a variety of communications, global-positioning, and defense satellite systems, as well as for protection against geomagnetically-induced electric power outages on Earth.

  • Magnetotail asymmetry from ionospheric Hall conduction

    Magnetotail asymmetry from ionospheric Hall conduction

    Satellite measurements show that the distributions of high-speed plasma flows at distances of 10 to 30 Earth radii in Earth’s magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. Global numerical simulations are being used to investigate the role of the electrodynamic interaction between Earth’s magnetosphere and ionosphere, in particular, the meridional gradient in the ionospheric Hall conductance, in producing observed asymmetries. The simulation experiments are designed to address the following questions:

    1. What controls the relative diversion of Hall current into field-aligned and secondary ionospheric currents at Hall conductance gradients?
    2. What are the causes, and magnetospheric implications, of two-cell ionospheric convection states that have more flux circulating in the dusk cell than the dawn cell?
    3. How do interplanetary conditions control the degree of rotation of the ionospheric convection pattern and the dawn-dusk asymmetry in flux circulation, and what are the implications for the distribution of nightside reconnection and plasmasheet convection?

    This project is funded by a grant from NASA.

  • Simulation of polar cap fast flow channels and their impacts on auroral and magnetotail activity

    Simulation of polar cap fast flow channels and their impacts on auroral and magnetotail activity

    This project explores a newly proposed pathway to the development of the important class of auroral activations called poleward boundary intensifications (PBIs). PBIs are powered by Alfvénic electromagnetic power flowing into the polar cap boundary region from the magnetotail, and they are precursors to very dynamic and energetic events called auroral substorms. Localized channels or jets of fast polar convection flowing from higher latitudes into the nightside auroral – polar cap boundary appear to initiate PBI onset. The recent development of very high-resolution grids for the Dartmouth Lyon-Fedder-Mobarry global simulation model of geospace is enabling its application to this problem. The project has the following objectives:

    1. Analyze modalities of formation of fast flow channels in the polar ionosphere.
    2. Determine their evolution and properties across the PC, in the lobes and magnetotail.
    3. Evaluate their casual impacts on auroral and magnetotail activity and plasmasheet dynamics.

Videos

Seminar: Forecasting Space Weather