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Dust and Spacecraft Charging Effects Near Asteroids and Comets

Mihaly Horanyi
Delivered As: 
Abstract Text: 

Objects exposed to solar wind plasma and UV radiation charge to a typical electrostatic surface potential on the order of +5V with respect to 0 at infinity. In the vicinity of outgassing asteroid or comet, the produced neutrals become ionized by UV radiation and become an additional source of plasma. The increased plasma density might be sufficiently large to change the sign of the spacecraft potential to negative values. These effects could complicate to analysis and interpretation of plasma and dust measurements, especially if the neutral gas production becomes highly variable, due to jets and/or outbursts of gas, for example. This talk will describe the charging currents, the characteristics of the plasma sheath surrounding a spacecraft, and its consequences. Similar approach is taken to describe the charging of small dust particles. Their charging time, contrary to a spacecraft, can be very long as it is inversely proportional to their size. Hence, depending on the plasma environment and its characteristic variability, small and large particles can intermittently have opposite signs of their charge. In that case both rapid coagulation and disruption can take place, efficiently altering the initial size distribution of the particles. These effects are examined as functions of both the heliocentric distance, setting the production rate of the neutrals and their lifetime, as well as the distance from the object s itself. The possible changes of the expected collection efficiency and sensitivity of in situ dust measurements will be also described.

Uma Gayathri Kamakolanu"...
SSERVI Identifier: 

Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."