University of Maryland
Atlantic Building, Room 2400 4:30 PM Monday, April 10, 2006
Coffee, Tea & Snacks 4:15-4:30 PM

Dennis Papadopoulos
University of Maryland

The Lower Ionosphere as an Active Medium and its Applications to Radiation Belt Control and Underground Exploration

The lower ionosphere, between 70-110 km altitude, constitutes a special form of magneto-plasma resembling more a semiconductor plasma than the traditional space plasmas. Furthermore, in the polar and equatorial regions solar activity in the form of solar wind and radiative heating, drives cross-field currents creating an active magneto-plasma. Over the years the active properties of the ionospheric plasma have been exploited by using it as medium that can convert, in a controlled fashion, HF radio-waves to coherent ELF/VLF waves. In this seminar I will concentrate on the following two topics:

1.I will first present recent results from experiments conducted using the HAARP facility in Alaska and the Jicamarca radar in Peru. The objective of these experiments was to explore and quantitatively understand the key physics puzzles observed in previous investigations, caused by the strong non-linear physics involved in the interaction of modulated HF pulses with the ionospheric plasma. The results led to complete revision of the previous theoretical understanding and scaling of the interaction.
2.I will then follow it with a presentation of concepts and preliminary experimental results on utilizing the ionospherically generated coherent VLF/ELF waves for remote control of the energetic electron fluxes in the radiation belts and for underground exploration.