Focus on Research
Penn State Intercom......April 4 , 2002

Blue jets, blue starters
show similarities

By A'ndrea Messer
Public Information

Blue jets and blue starters form from multiple streamers of electrical energy, rather than as a single glowing column, according to researchers who modeled the formation of these atmospheric phenomena. Research_Pasko

"In 1999, Petrov and Petrova predicted that blue jets and blue starters were made up of a large number of small scale channels or streamers," according to Victor P. Pasko, associate professor of electrical engineering. "We used a modification of a fractal model, a type of model originally developed to study corona streamers in gas insulation systems, to model a blue jet."

Pasko, working with Jeremy J. George, undergraduate in electrical engineering, applied both a two-dimensional and three-dimensional version of the model to replicate a blue jet.

Blue jets were first documented by University of Alaska researchers in 1994, but were probably seen by pilots long before formal documentation occurred. Red sprites, blue jets more familiar cousins, have only been documented for about 10 years. While sprites are more common, forming almost always in a certain-sized lightning storm, they are much shorter lived, lasting only a few milliseconds. Blue jets should be easier to see because their duration is hundreds of milliseconds to a second long, but they are much rarer and their blue light is difficult to see from the ground.

"Both the two-dimensional and three-dimensional models agreed and produced a realistic reproduction of a blue jet," Pasko said. "The charge distribution always creates a cone shape."

The model assumes an internal streamer structure and while there are differences in the two- and three- dimensional models, seem to confirm that blue jets are made of many small streamers and not a solid glowing column.

Since 1994, researchers have studied blue jets to see how they compare to the better-known red sprites. One difference is that while red sprites always follow a substantial lightning strike, blue jets are not directly triggered by lightning. They are, however, related to strong hail activity in thunderstorms.

"Hail is indicative of a large charge separation and hail is negatively charged," Pasko said. "When hail falls from the sky, a very positively charged cloud remains overhead."

Blue jets propagate from the tops of clouds toward the ionosphere 12 to 30 miles high. They are a mile or two at the base and five or six miles at the top and are always cone shaped and blue.

Blue jets propagate slowly from bottom to top, but extinguish simultaneously. Blue starters have the same properties, but travel a shorter distance into the atmosphere.

The researchers did find that using the same fractal models, with a low charge as input, produced short blue jets, or blue starters. "Blue starters appear to be blue jets that never quite make it," Pasko said.

A'ndrea Messer can be reached at aem1@psu.edu.

 

Erie professor's Web site locates
aquatic flies, shares years of research RESEARCH_BugWebsite

To some people, insects are just bugs. To Ed Masteller, insects -- especially Pennsylvania's caddisflies and stoneflies -- are a valuable natural resource and a good indicator of water quality throughout the commonwealth. He's sharing his years of research on these two insects on a new Web site, http://paaquaticfliesrus.bd.psu.edu.

Masteller, known affectionately as the "bug man" by students and colleagues, is professor emeritus of biology at Penn State Erie. In addition to research on caddisflies and stoneflies, he collaborates with Pennsylvania Sea Grant on studies of mayflies, native mussels and has an abiding interest in sustainable ecology. The Web site is named Pennsylvania Aquatic Flies Are Us and includes distribution maps of caddisflies and stoneflies and their occurrence in North America.

"The caddisfly and the stonefly are superior indicators of water quality in Pennsylvania's streams," Masteller said. "Trout fishermen love to see them and will often tie flies that duplicate these two insects."

Masteller received a grant from Pennsylvania's Wild Resource Conservation Fund to study the trichoptera (caddisflies) in 1989-90, and during his research recorded 319 species in 21 families and 73 genera throughout Pennsylvania. He prepared a two-volume report on his findings and shared it with colleagues, and that report is now in its third edition. He also was funded by the Wildlife Resource Conservation Fund in 1995 to study plecoptera (stoneflies). During his research he recorded 134 species in nine families and 41 genera, and produced yet another multi-page volume of his findings.

But Masteller did not stop there. Along with scientific colleagues, fishermen and others throughout Pennsylvania who are interested in collecting and recording data, he continues to find new location in Pennsylvania of both the caddisflies and the stoneflies. Rather than keep publishing additional expensive paper volumes of his records, he opted for a Web site that could be easily updated with new information.

Black holes found
in distant quasars

An international team of scientists led by Niel Brandt, associate professor of astronomy and astrophysics, has used NASA's Chandra X-Ray Observatory to detect the three most distant-known quasars, among the most luminous objects in the universe.

The team's observations with Chandra recorded high-energy X-ray emissions that were produced more than 10 billion years ago by the quasars' massive black holes.

The discovery that these quasars are prodigious producers of X-rays indicates the supermassive black holes powering them were already in place when the universe was only about 1 billion years old.

"Chandra's superb sensitivity has allowed the detection of X-rays from the dawn of the modern universe, when the first massive black holes and galaxies were forming," Brandt said. "These results indicate that future X-ray surveys should be able to detect the first black holes to form in the universe."

The three quasars were recently discovered at optical wavelengths by the Sloan Digital Sky Survey -- a large international effort that aims to observe 100,000 quasars, measure the distances to a million galaxies and produce a comprehensive digital map of the sky. The three quasars are 13 billion light years from Earth, making them the most distant known quasars. Brandt's team includes Donald Schneider, professor of astronomy and astrophysics, who has been chair of the Sloan Digital Sky Survey Quasar Science Group since its inception in the early 1990s and has set many previous records for the discovery of "most distant" quasars, Gordon Richards, postdoctoral scholar, and many scientists from the Sloan survey.

For more of this story, go to http://www.science.psu.edu/alert/Brandt3-2002.htm

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