[extropy-chat] Graps Seminar and Colloquium at USC on November 6

[Amara Graps]

Hello,

A heads-up. I'm giving a colloquium (more general) and a seminar
(more technical)  for the Department of Physics and Astronomy,
at the University of Southern California (USC) on November 6. The
abstracts are below. I'll send another notice when the date gets
closer.

Amara


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http://physics.usc.edu/Colloquia/ViewTalk.php?t=2294

Watering the Earth

Amara L. Graps

Institute of Physics of Interplanetary Space (IFSI), Rome, Italy
and
Planetary Science Institute (PSI), Tucson, Arizona

Amara.Graps at ifsi-roma.inaf.it

Abstract:

Water is one of the key molecules of life, and a fundamental solvent of
our own human life form. The planet that spawned our watery origins,
Earth, presently carries enough surface water in vapor or liquid form to
cover the entire planet to a depth of about 3 km. The fact that nearly
three-quarters of the Earth's surface is covered by seas triggered
writer Arthur C. Clarke to question why our planet is called *Earth*,
when it could more aptly be called *Ocean*. Driven by our watery
origins, we naturally look for other life forms in the universe at the
"water hole" (wavelengths 18-21 cm). Simultaneously, we search, and
find, water in planetary atmospheres, comets, asteroids, interplanetary
dust, and molecular clouds. Water drives our questions about terrestrial
and extraterrestrial life  and we wonder how we came to exist on a
planet so rich in water in the first place. So then, how _did_ our
planet Earth get its water? The short answer is: 'we still don't know'.

Despite our living embedded in the Earth environment, the origin of
our atmosphere is one of the most puzzling enigmas in the planetary
sciences. The processes and sources that contributed to its formation
require knowledge of the formation of the solar nebula, Earth and its
planetary neighbors, and each of their subsequent interactions,
including the smaller members of the clan: asteroids, meteorites and
comets. Timing and location is everything in this story and our main
tool for trying to understand the puzzle will be elemental isotopic
abundance measurements.

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Tracing our Origins: The Charging and Dynamics of (local) Cosmic Dust

Amara L. Graps

Institute of Physics of Interplanetary Space (IFSI), Rome, Italy
and
Planetary Science Institute (PSI), Tucson, Arizona

Amara.Graps at ifsi-roma.inaf.it

Abstract:

The charging of cosmic dust as a topic of study provides nonintuitive
details of the important charge parameter in the electrodynamical force,
which plays a dominant role over the gravitational force for the
Universe's cosmic dust particles. Cosmic dust particles are rarely
electrically neutral because they are immersed in space plasmas,
collecting ions, electrons, residual high-energy particles, and
receiving ultraviolet radiation from nearby stars. The tiny particles
electrically and dynamically respond to their environment with surface
charge potentials which closely follow the surrounding plasma and
magnetic field conditions. At the same time that the particle "charges
up", it is responding to its environment dynamically via the Lorentz
electromagnetic force. Therefore, small cosmic dust particles are ideal
tracers of their astrophysical environments.

A variety of charged cosmic dust populations exist within the
magnetospheres of the planets in our solar system. The variable charging
of the small dust particles leads to the particle's nonintuitive
circumplanetary trajectories. One of the most dramatic examples of the
charging of cosmic dust is the Jovian dust streams: high-speed (at least
200 km/sec) collimated streams of submicron-sized particles traveling in
the same direction from a source (Io) in the Jovian system.  Saturn,
with a different source (unknown) and a different plasma environment
joins Jupiter with a similar dust stream phenomenon. The Earth's GEO
dust and spacecraft debris yields yet another class of charged particles.
With time permitting, I will show examples of the charging effects
on dust particles' dynamics in the magnetospheres of the Earth, Jupiter
and Saturn.

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-- 

Amara Graps, PhD      www.amara.com
Istituto di Fisica dello Spazio Interplanetario (IFSI), Roma, ITALIA
Associate Research Scientist, Planetary Science Institute (PSI), Tucson