Colloquium Announcement

Current sheets are important to space and laboratory plasma, and particularly to the Earth’s magnetotail where a consequential but overlooked transverse ambipolar electric field is self-consistently generated as the magnetotail is compressed by the solar wind. This interaction of large and small-scale physics affects the plasma environment in the magnetosphere, also known as “space weather”. In situ measurements show compression of the magnetotail that creates a thin current sheet of width comparable to the ion gyro-radius (ρi), occasionally with single or double peaked substructures in the current density. Their existence cannot be explained by the

standard Harris equilibrium. Intense lower hybrid wave activity and subsequent magnetic reconnection is also observed in regions with negligible diamagnetic drift but with strongly sheared electron drift. We discuss a generalized Harris model that can explain these seemingly disparate phenomena along with the subtleties of their causal relationships and their cumulative effects on the current sheet dynamics.

Dr. Gurudas Ganguli is the Senior Scientist for Intense Particle Beams and Plasma Processes in the Plasma Physics Division at the Naval Research Laboratory (NRL). Prior to this appointment in June 2012, he was the Head of the Space Analysis and Applications Section, Plasma Physics Division, NRL.  He has a broad range of experience in plasma processes including beam-plasma interactions, plasma turbulence, dusty plasma dynamics, laser-produced plasma expansion, and high energy density physics in hypervelocity impact of projectiles in space.  His work has addressed both natural plasmas as well as induced disturbances in the near-earth space environment.  His research has motivated a number of laboratory and space experiments.  He has led several ONR/NRL, DTRA, DARPA, Air Force and NASA sponsored research programs in ionospheric and magnetospheric plasmas as well as negative ion and dusty plasmas.  He has authored/co-authored more than 170 publications.  He is the recipient of 2014 E. O. Hulburt Award for science, several NRL Berman awards for excellence in research publications, 2014 Edison Award for patent on a novel technique to de-orbit the lethal small orbital debris, and 2010 Technology Transfer Award.  He was a member of the NRL Invention Evaluation Board and ONR panel member to upgrade the Navy S&T strategy plan in 2011 - 2012.  He obtained his B.Sc. degree, from St. Xavier’s College, Ahmedabad, India, in 1974 and Ph.D degree from Boston College, Boston, Massachuttes, in 1980.  He was the Chairman of the International Union of Radio Science, Commission H (US National Chapter), during 2002 – 2005.   He is a Fellow of the American Physical Society, Adjunct Professor of Physics at West Virginia and Auburn Universities, and a member of the American Geophysical Union.  He has given over 100 invited talks at various national and international institutions and was appointed by the American Physical Society as a Distinguished Lecturer in Plasma Physics for 2001 –2002.