Studies of Electromagnetic Fields in the Atmosphere

(Faculty Mentor: Victor Pasko)

    Communications and Space Sciences Laboratory at Penn State University is actively involved in studies of the effects of the strong electromagnetic radiation generated by lightning discharges on the near Earth's electromagnetic environment, including their effects on the Earth's mesospheric and lower ionospheric regions. The importance of tropospheric thunderstorms on a global scale is underscored by the facts that more than 2000 thunderstorms are active at any given time over the Earth's surface and on average lightning strikes the Earth approximately 100 times per second leading to intense electromagnetic pulses of approximately 20 Gigawatts peak power emitted by lightning currents. Lightning discharges radiate broadband electromagnetic pulses known as radio atmospherics (commonly called "sferics") with the peak power typically confined to the range of extremely low frequencies, 15 Hz - 1.5 kHz. The electromagnetic pulses in this frequency range are trapped in the waveguide formed by the Earth surface and the ionosphere and are able to travel thousands of kilometers with very low attenuation.

    The REU student will be involved in the ongoing research to develop realistic two and three dimensional finite difference time domain (FDTD) models to simulate the propagation of lightning generated electromagnetic fields in the earth-ionosphere waveguide. The basic requirement for this project is familiarity with electromagnetics. A working knowledge of C and MATLAB is also required. The project will provide an excellent opportunity to master your programming skills and also will allow you to learn about some numerical techniques commonly used for solution of engineering electromagnetics problems.

Studies of Lightning Induced Electrical Discharges in the Upper Atmosphere

    Red sprites are upper atmospheric optical phenomena associated with thunderstorms that have only recently been documented using low light level television technology. Sprites are spectacular luminous features occupying volumes in excess of thousands of cubic kilometers at mesospheric/lower ionospheric altitudes above thunderstorms. It appears from space shuttle observations that sprites occur over most regions of the globe (in temperate and tropical areas, over the oceans, and over the land). To date sprites have been successfully detected from ground and airborne platforms in North, Central and South America, in Australia, over winter storms in Japan, and over Europe. In spite of the apparently high global occurrence rates, and the rapid progress achieved in recent years in experimental and theoretical studies of sprites, the importance of this fascinating natural phenomenon on the global near Earth thermal and chemical environment is still not quantified. Are sprites only pretty and beautiful like rainbows, or do they significantly impact the atmosphere? This is a very hot topic in the current atmospheric research. Communications and Space Sciences Laboratory at Penn State University is actively involved in development of gas discharge and optical emissions models of sprites in order to answer a broad range of questions related to the microphysics and energy budget of sprites and channels by which their energy is dissipated in the mesospheric and lower ionospheric regions.

    The REU student will be directly involved in research and software development related to modeling studies of filaments of ionization (so called streamers), which in accordance with recent experimental discoveries constitute small scale building blocks of the large scale sprite phenomena. The basic requirement for this project is to be familiar with C programming language and MATLAB. Some elementary knowledge of electromagnetics is also necessary. This introductory project will provide an excellent opportunity to learn about numerical techniques used in science and engineering for solution of partial differential equations and also will help to master your programming skills.

Visualization and Analysis of Simulated Atmospheric Gravity Wave Data

    On very large scales, the atmosphere acts much like an incompressible fluid. Traveling mechanical waves of low frequency and large wavelength occur as a result of buoyant air motion—these "Gravity Waves" typically have wavelengths spanning tens of kilometers and periods greater than 5 minutes. It is now well known that gravity waves generated by convective sources (e.g., thunderstorms) at tropospheric altitudes represent significant sources of energy and momentum depositions and turbulence generation at mesospheric altitudes.  The importance at mesospheric altitudes of upward traveling gravity waves excited by convection in thunderstorms is underscored by the exponential decrease of atmospheric density with height and the principle of conservation of energy. In order for the wave's kinetic energy per unit volume to remain constant as wave travels upward, the perturbation velocity associated with the wave must increase exponentially. Therefore, waves originally generated in troposphere grow considerably by the time they reach mesospheric altitudes and are able to sufficiently affect motions in the upper atmosphere. Communications and Space Sciences Laboratory at Penn State University is involved in studies of these waves using high-resolution, two-dimensional, numerical simulations that output "images" of mass density, momentum, and energy density for moments of time. From this data, we measure properties such as velocity, temperature, pressure, or relative density. We can also extract spectral properties of wave number and frequency. This is helpful in understanding nonlinear behavior. Using a sequence of output data, we can follow the spectral evolution of the system over time. We can also use the spectral data to specify image filters to isolate specific phenomena.

    The undergraduate researcher would work with assistance from a graduate student to develop and analysis and visualization tools in MATLAB. This interested applicant should have a basic understanding of linear wave motion and signal or image processing. MATLAB programming skills would be very helpful, but much will be learned along the way. For a student interested in space sciences, remote sensing, or image processing, this could be an exciting introductory project.