Dusty plasma in the universe and in the laboratory
August 16, 2016 by Augusto Carballido, Jorge Carmona-Reyes And Truell Hyde, The Conversation
… researchers think that 99 percent of the matter in our universe is in a plasma state. Many processes that occur in the universe are due in part to the presence of plasma.
Here on Earth, industry uses techniques that involve manipulating these ionized gases for microchip production, as well as for welding materials such as aluminum. Research facilities study plasma in hope of hitting on an efficient nuclear fusion process for energy production. In all these instances micron-size dust is present – which can be a good or a bad thing, depending.
The presence of dust in plasma makes it tricky to study them in a laboratory setting. Here at Baylor University’s Center for Astrophysics, Space Physics and Engineering Research (CASPER), we’ve built a sophisticated experimental facility to investigate these dusty plasma systems. We hope to answer fundamental questions related to dust-plasma interactions both on Earth and in space, in the process advancing our understanding of physics and astrophysics. Our investigations will allow us to untangle issues like the role of dust buildup in super-high-speed crashes in space, the formation of planets, and even areas belonging to life sciences, such as double-helix molecular interaction.
Solid swimmers in an electrical sea
Dusty plasma, also called complex plasma, contains small, solid particles distributed throughout the ionized gas. These particles can have the shape of a sphere, a rod or an irregular “pancake.” The reason dusty plasma are very interesting, and even technologically valuable, comes down to the fact that the dust particles themselves can become electrically charged.
We can think of dust particles as swimmers in a sea of electrons and ions – negative and positive charges, respectively. Electrons are so tiny compared to the dust that they easily stick to the particles’ surfaces. When that happens, a dust particle will become negatively charged.
Because like charges repel each other, that bit of dust will now feel a push from other negatively charged dust particles. Likewise, that same negatively charged dust particle will feel a pull by the positive ions in the plasma, because charges of opposite signs attract each other. The net result is that dust particles will be pushed and pulled in many different directions, making them move in complex and fascinating ways.
Dusty plasma ‘in the wild’
One place to find dusty plasma is in Earth’s atmosphere, where they’re generated when meteoroids enter the atmosphere’s upper layers at speeds of several kilometers per second. Researchers study them with specialized radars that can detect the ball of plasma that forms around the meteroids as they heat up due to friction with the air.
At high geographic latitudes (between 50° and 70° north and south of the equator) an intriguing phenomenon occurs. Clouds made of tiny ice crystals and dust appear at an altitude of about 80 kilometers during the summer months. Known as noctilucent clouds, they are too thin to be visible in daylight, but they glow before sunrise or after sunset when the sun is below the horizon.
The clouds’ icy dust particles are thought to play a role in the chemical composition of the atmosphere at those altitudes. In particular, their presence may be related to depletion of sodium and potassium. And since noctilucent clouds reside in an ionized region of the atmosphere (specifically, the lower ionosphere), their icy dust particles become electrically charged by electrons. These conditions give rise to a variety of electromagnetic phenomena researchers are actively investigating.
Effect of plasma nonuniformity on electron energy distribution in a dusty plasma
I Denysenko1,4,3, M Y Yu1 and S Xu2
Published 20 January 2005 • 2005 IOP Publishing Ltd Journal of Physics D: Applied Physics, Volume 38, Number 3
The effect of plasma nonuniformity on the electron energy distribution function (EEDF) and plasma parameters such as the ion density, electron temperature and dust charge in a dusty plasma are studied using a Boltzmann equation for the electrons and the fluid equations for the ions. The EEDF and the plasma parameters are obtained taking into account electron diffusion. The effect of the dusts on the electron energy-relaxation length is shown to be significant. The latter decreases as the dust density and/or size increase. Only at relatively high dust densities/sizes do the results of the homogeneous Boltzmann equation approach that of the more accurate kinetic equation.
St. Lawrence Island (two above) (Central Siberian Yupik: Sivuqaq) is located west of mainland Alaska in the Bering Sea, just south of the Bering Strait. The village of Gambell is located on the northwest cape, 58 kilometres (36 miles) from the Chukchi Peninsula in the Russian Far East. The island is part of Alaska, but closer to Siberia than to the Alaskan mainland. St. Lawrence Island is thought to be one of the last exposed portions of the land bridge that once joined Asia with North America during the Pleistocene period. It is the sixth largest island in the United States and the 113th largest island in the world.
Northeast Cape Air Force Station, at the island’s other end, was a United States Air Force facility consisting of an Aircraft Control and Warning (AC&W) radar site, a United States Air Force Security Service listening post; and a White Alice Communications System (WACS) site that operated from about 1952 to about 1972. The area surrounding the Northeast Cape base site had been a traditional camp site for several Yupik families for centuries. After the base closed down in the 1970s, many of these people started to experience health problems. Even today, people who grew up at Northeast Cape have high rates of cancer and other diseases, possibly due to PCB exposure around the site. According to the State of Alaska, those elevated cancer rates have been shown to be comparable to the rates of other Alaskan and non-Alaskan arctic natives who were not exposed to a similar Air Force facility. In any event, the majority of the facility was removed in a $10.5 million cleanup program in 2003. Monitoring of the site will continue into the future. WIKI
Bristol Bay Alaska (two above) http://go.nasa.gov/2fTmnqn
Tip of Baja CA (two above) http://go.nasa.gov/2fTjiqh http://go.nasa.gov/2fTeRfm
Tip of S. America & east http://go.nasa.gov/2ghWiye http://go.nasa.gov/2fTnLJD