CEDAR: Meteor Plasmas--Theory, Simulations and Observations

Trustees Of Boston University, Boston

Investigators

Abstract

Every year thousands of tons of meteoric material enter the Earth's upper atmosphere, mostly in the form of meteoroids smaller than a grain of sand. Their entry into the atmosphere causes the particles to heat and ablate leaving trails of hot gas and plasma. Optical instruments can detect only large meteors; radars can detect much smaller particles and account for more measurements than all other techniques. Meteor radars, instruments which observe the meteor trails, have been used for decades to measure the winds near the mesopause and in the lower thermosphere. To enable better understanding of meteor evolution and observations, the investigators are focusing on answering four long-standing questions in meteor physics: (1) how do meteor plasmas evolve from creation until diffusion into the atmosphere? (2) is it possible to model, analytically or via simulations, each stage of meteor evolution to generate quantitative estimates of meteor characteristics? (3) what are the radiowave scattering characteristics during the meteors' passage through the atmosphere? (4) what information can be reliably extracted from meteor radar data? These questions are highly relevant to upper atmospheric science since their resolution will improve radar measurements of meteors leading to better estimates of the winds and temperatures in the lower thermosphere. The research will also enable evaluation of where and what meteoric material is being deposited into the atmosphere. Current estimates of total meteoric input are extremely uncertain. These estimates are useful in atmospheric modeling, in formulating and testing theories of solar system evolution, and in spacecraft design. The research team is the only one in the world with the ability to simulate meteor evolution from first principles and to analyze meteor radar data in terms of plasma theory and scattering. Building on past work, the investigators will develop a full treatment of meteor diffusion in a magnetized and collisional ionosphere. The massively parallel multi-dimensional fluid/kinetic simulators to be developed will be capable of modeling collisional plasma physics processes extending from the microsecond to the second time scale and from the millimeter to tens of meters length scale. The modeling and simulations studies will include treatment of multiple ion species, electrodynamic effects, scattering effects, and the effects of a realistic E region which may be subject to large neutral winds. The models and theoretical interpretations will be exercised through application to observations obtained from various radars including Jicamarca, ALTAIR, AMISR, Millstone Hill, Arecibo, Sondrestrom, and EISCAT. The investigation supports participation by a postdoctoral scholar and a graduate student; two undergraduate students are also typically involved. Through this project, they will receive extensive training in observing, data analysis and interpretation, theoretical calculations, and numerical modeling. International and domestic collaborations with other research groups are planned and will provide further opportunities for student involvement and advancement.