Featured Research

from universities, journals, and other organizations

Filamentary Structure Of Atmospheric Sprites Confirmed

Date:
December 11, 1998
Source:
Stanford University
Summary:
Stanford researchers have put red sprites under a telescope and found that they consist of thousands of fiery streamers, each only a few meters wide.

Stanford researchers have put red sprites under a telescope and found that they consist of thousands of fiery streamers, each only a few meters wide.

Related Articles


For several years members of Stanford's Very Low Frequency Research Group (VLF) have been studying this dazzlingly bright but subliminally brief form of lightning that occurs high in the atmosphere above large thunderstorms.

Last year the researchers proposed that sprites may have such a filamentary structure. To test this hypothesis they acquired a small telescope capable of viewing the features of red sprites in unprecedented detail and installed it in a prime, sprite viewing location, the Langmuir Laboratory of the New Mexico Institute of Technology and Mining in Socorro.

"The laboratory is located on top of an 11,000-foot peak and provides clear views of thunderstorms in Kansas, Colorado, Texas, and northwest Mexico," said Umran S. Inan, professor of electrical engineering and head of the VLF research group.

Until now observations of sprites, which can be more than 25 miles wide and 25 miles in height, have been made from a considerable distance with low-light-level video cameras capable of capturing the images of these extremely brief flashes. In these images, sprites appear as large blobs of red light. But these images can not distinguish features that are less than 400 to 600 feet in size, so details the size of the predicted streamers were not visible.

The main problem with getting detailed pictures of sprites is their brevity. With a lifetime of milliseconds, individual sprites do not last long enough for a telescope operator to zero in on them.

"Fortunately, our knowledge of sprite behavior came to the rescue," said Inan. "We knew from past observations that, when a storm kicks up sprites, they tend to appear repeatedly at about the same place for 10, 20 even 30 minutes."

That allowed the telescope operator, Elizabeth Gerken, to catch sprites in the act by positioning the telescope at the location of a previous sprite and catching its successors. The 16-inch wide, 6-foot long telescope, which was purchased off the shelf from Orion Telescopes & Binoculars, can distinguish details down to 30 feet in size from a distance of 300 miles.

"The system worked almost from the beginning," said Gerken, a graduate student in electrical engineering and a Stanford graduate fellow. Working typically past midnight in the chilly night air of the mountain-top observatory, she successfully recorded the most detailed images of this elusive atmospheric phenomenon ever taken.

The pictures show the streamers that the researchers had predicted, but their shape and complex arrangement came as a complete surprise. "What we are seeing is not explained by any theory. We are all somewhat at a loss," said team member Christopher Barrington-Leigh, a graduate student in applied physics.

In the images, most of the streamers are vertical, but many are tilted at a variety of angles. Many streamers are present in one frame and absent in the next ‚ meaning that they have lifetimes of less than 17 milliseconds ‚ but some individual branches seem to persist through several frames. Most leave solid streaks. Others turn on and off, creating what appear as dashed lines or beaded forms.

The researchers are poring over the images, looking for patterns. Gerken, who has spent the most time examining them, says that many streamers have a branching, tree-like structure. She has observed that the streamers tend to branch upward at the top of the sprite, while they tend to branch downward near the bottom.

According to the Stanford researchers, the streamers are caused by a build-up of electrostatic charge in the atmosphere created by strokes of lightning. When a large bolt of lightning flashes from the top of a thunderhead to the ground in a matter of milliseconds, it leaves behind large amounts of uncompensated electrical charge in the atmosphere. This creates an intense electrostatic field in the region above the thunderstorm. If the lightning discharge is large enough, then the electrostatic field causes the air to ionize at thousands of points where the field is strongest.

Normally, air, which is made up primarily of electrically neutral molecules, has a relatively high electrical resistance. But an electric field that is strong enough will accelerate ambient electrons to energies sufficient to knock additional electrons off the air molecules in collisions, causing them to become electrically charged. Such ionized air molecules conduct electricity much more readily than normal air molecules.

In the region between 30 and 50 miles in altitude above a thunderstorm, the Stanford researchers predicted that small scale spark channels will form at the electrical breakdown points. These channels, which give off a blue glow, should be propelled upward (although a few may streak downward) with velocities as fast as one-tenth of the speed of light, leaving behind glowing red streamers of ionized gas.

The new pictures confirm this general scenario, but the researchers say that they need to do a lot of additional work to explain the rich, unexpected detail that they have discovered. For example, they also predicted that the streamers would glow for a few milliseconds before burning out, but the new pictures indicate that some of them last much longer than predicted.

-30-

By David F. Salisbury


Story Source:

The above story is based on materials provided by Stanford University. Note: Materials may be edited for content and length.


Cite This Page:

Stanford University. "Filamentary Structure Of Atmospheric Sprites Confirmed." ScienceDaily. ScienceDaily, 11 December 1998. <www.sciencedaily.com/releases/1998/12/981211083459.htm>.
Stanford University. (1998, December 11). Filamentary Structure Of Atmospheric Sprites Confirmed. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/1998/12/981211083459.htm
Stanford University. "Filamentary Structure Of Atmospheric Sprites Confirmed." ScienceDaily. www.sciencedaily.com/releases/1998/12/981211083459.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Antarctic Sea Ice Mystery Thickens... Literally

Antarctic Sea Ice Mystery Thickens... Literally

Newsy (Nov. 25, 2014) Antarctic sea ice isn't only expanding, it's thicker than previously thought, and scientists aren't sure exactly why. Video provided by Newsy
Powered by NewsLook.com
3D Map of Antarctic Sea Ice to Shed Light on Climate Change

3D Map of Antarctic Sea Ice to Shed Light on Climate Change

Reuters - Innovations Video Online (Nov. 24, 2014) A multinational group of scientists have released the first ever detailed, high-resolution 3-D maps of Antarctic sea ice. Using an underwater robot equipped with sonar, the researchers mapped the underside of a massive area of sea ice to gauge the impact of climate change. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Car Park Solution for Flexible Green Energy

Car Park Solution for Flexible Green Energy

Reuters - Innovations Video Online (Nov. 24, 2014) A British solar power start-up says that by covering millions of existing car park spaces around the UK with flexible solar panels, the country's power problems could be solved. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins