Explaining Sporadic Layers Of Sodium In The Upper Atmosphere

July 06, 1998

WASHINGTON, D.C. -- Researchers at SRI International in Menlo Park, California, and the University of Alaska's Geophysical Institute in Fairbanks have provided new scientific backing to a theory explaining the presence of thin sporadic layers of sodium in the Earth's upper atmosphere. These sporadic layers are in addition to the better understood layer of neutral sodium atoms found between 80 and 100 kilometers altitude, believed to be a by-product of meteors vaporizing on entering the atmosphere.

Using the National Science Foundation's incoherent scatter radar and sodium lidar near Kangerlussuaq, Greenland, Craig J. Heinselman and Dr. Jeffrey P. Thayer of SRI and Dr. Brenton J. Watkins of the University of Alaska have demonstrated an instance of a thin ion layer being pushed downward to a region where chemical catalysts recombined the ionized sodium in that layer. This left a thin layer of neutral sodium behind.

Contrary to the predictions of competing theories, the formation of that neutral sodium layer was not significantly affected by the presence of intense auroral ionization. The findings will be reported in a forthcoming issue of Geophysical Research Letters, published by the American Geophysical Union.

The existence of sporadic sodium in the upper atmosphere has been observed since the late 1970s, and various theories had been advanced to explain its presence and its apparent correlation with layers of metallic ions, called sporadic E. Astronomers use the background sodium layer to create an artificial guide star for the adaptive correction of telescope optics for atmospheric effects.

The inaccessibility of this high altitude region had made it difficult to test these theories, and it is possible that different mechanisms create the sporadic sodium layers at different times and places, the researchers say. The recent addition of a resonant sodium capability to the Arctic Lidar Technology System at the Sondrestrom facility near Kangerlussuaq made the new measurements possible.

"What we are trying to do," says Heinselman, "is understand the physics and chemistry of this region of the atmosphere. Such an understanding could well lead to significant answers with regard to the coupling and transport of gasses to other regions. For example, the rate at which sodium ions are converted to sodium atoms is thought to be governed by the ratio of carbon dioxide to atomic oxygen. If this is in fact the case and if we can measure that conversion rate, we may be able to infer the concentration of carbon dioxide near 90 kilometers altitude. Such information could then be fed back into global models involving this important greenhouse gas."

The research was supported by a cooperative agreement and grants from NSF.
-end-
Editors: A copy of the Heinselman, et. al., paper may be obtained from Harvey Leifert at AGU. It has not yet been scheduled for a specific issue of GRL, but is NOT under embargo.

For further information about this study and its conclusions, you may contact Mr. Heinselman at heinselman@sri.com.
-end-


American Geophysical Union

Related Atmosphere Articles from Brightsurf:

ALMA shows volcanic impact on Io's atmosphere
New radio images from ALMA show for the first time the direct effect of volcanic activity on the atmosphere of Jupiter's moon Io.

New study detects ringing of the global atmosphere
A ringing bell vibrates simultaneously at a low-pitched fundamental tone and at many higher-pitched overtones, producing a pleasant musical sound. A recent study, just published in the Journal of the Atmospheric Sciences by scientists at Kyoto University and the University of Hawai'i at Mānoa, shows that the Earth's entire atmosphere vibrates in an analogous manner, in a striking confirmation of theories developed by physicists over the last two centuries.

Estuaries are warming at twice the rate of oceans and atmosphere
A 12-year study of 166 estuaries in south-east Australia shows that the waters of lakes, creeks, rivers and lagoons increased 2.16 degrees in temperature and increased acidity.

What makes Saturn's atmosphere so hot
New analysis of data from NASA's Cassini spacecraft found that electric currents, triggered by interactions between solar winds and charged particles from Saturn's moons, spark the auroras and heat the planet's upper atmosphere.

Galactic cosmic rays affect Titan's atmosphere
Planetary scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn.

Physics: An ultrafast glimpse of the photochemistry of the atmosphere
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

Using lasers to visualize molecular mysteries in our atmosphere
Molecular interactions between gases and liquids underpin much of our lives, but difficulties in measuring gas-liquid collisions have so far prevented the fundamental exploration of these processes.

The atmosphere of a new ultra hot Jupiter is analyzed
The combination of observations made with the CARMENES spectrograph on the 3.5m telescope at Calar Alto Observatory (Almería), and the HARPS-N spectrograph on the National Galileo Telescope (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma) has enabled a team from the Instituto de Astrofísica de Canarias (IAC) and from the University of La Laguna (ULL) to reveal new details about this extrasolar planet, which has a surface temperature of around 2000 K.

An exoplanet loses its atmosphere in the form of a tail
A new study, led by scientists from the Instituto de Astrofísica de Canarias (IAC), reveals that the giant exoplanet WASP-69b carries a comet-like tail made up of helium particles escaping from its gravitational field propelled by the ultraviolet radiation of its star.

Iron and titanium in the atmosphere of an exoplanet
Exoplanets can orbit close to their host star. When the host star is much hotter than our sun, then the exoplanet becomes as hot as a star.

Read More: Atmosphere News and Atmosphere Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.