Science Seminars

2/10/2011 – Radar observation of meteor generated plasmas: understanding the impacts billions of sand and dust sized meteoroids

Speaker: Lars Dyrud (Johns Hopkins University, Applied Physics Laboratory)
Date: Thursday, Feb 10, 2011
Time: 4:00pm
Location: Duane D-142

Seminar Abstract:

Over 100 kilotons of meteoric material hits the Earth every year, yet the average mass, velocity (15-55 km/s), and chemical composition of the particles comprising this mass flux remain poorly constrained. This is because the vast majority of this flux is composed of particles of micron size that are no larger than a grain of sand or piece of dust. Such micro-meteoroids traditionally do not reach the ground becoming meteorites, and their trails are so dim that they are invisible to most optical systems. However, trails produced from micrometeroids generate 1014 or more free electrons at altitudes near 100 km, representing substantial enhancements to the natural ionosphere which presents a comparatively large radar cross section. This seminar will focus on the plasma processes that occur during meteor trail production and evolution and the associated radar reflections that occur during each stage of evolution. Our goal is that by understanding the plasma physics and radar reflection of meteor plasmas, we may provide answers regarding the meteor flux, its influence to the upper atmosphere and ionosphere, and its relation to planetary astronomy and the dangers posed to manned and unmanned space flight.