Title : Nonlinear Generation of Whistler Waves in Space Plasmas
Abstract : A sounding rocket based experiment to demonstrate the ability to produce and harness electromagnetic whistler waves in the ionosphere will be discussed. Release of high-speed neutral barium atoms (8- 10 km/s) generated by a shaped charge explosion perpendicular to the Earth’s magnetic field can be used as the source of free energy to seed lower hybrid turbulence. The Ba atoms are photo-ionized forming a ring velocity distribution of heavy Ba+ ions perpendicular to the ambient magnetic field that is known to generate lower hybrid waves [1]. The lower hybrid waves can be converted into electromagnetic whistler waves through nonlinear scattering by thermal electrons. The whistlers have large group velocity and can propagate out of the source region to affect plasma properties in remote locations in the magnetosphere. Induced nonlinear scattering of the lower hybrid waves into whistler/magnetosonic waves has been theoretically established [2,3] and experimentally demonstrated in laboratory [4]. The escape of the whistlers from the ionospheric source region and the consequences on the trapped population in the Earth’s radiation belts will be analyzed.
[1] Mithaiwala et al., Phys Plasmas, 17, 042113, 2010. [2] Ganguli et al., Phys Plasmas, 7, 052310, 2010. [3] Mithaiwala et al., Phys Plasmas, 18, 2011. [4] Tejero et al., Phys. Rev. Lett., (submitted).
Gurudas Ganguli is the Senior Scientist for Intense Particle Beams and Plasma Processes at the Plasma Physics Division, Naval Research Laboratory, Washington DC. He received his B.Sc. in physics from St. Xavier's College, Ahmedabad, India in 1974 and Ph.D. in Physics from Boston College, Boston, MA in 1980. His research interests concern the study of turbulent and coherent processes in collisional and collisionless plasmas, dusty plasmas, and their applications to both space and laboratory. He has contributed to the physics of ionospheric and magnetospheric plasmas including the dynamics in the earth’s natural and artificial radiation belts. He is a Fellow of the American Physical Society and member of the American Physical Society, American Geophysical Union, and International Union of Radio Science.