Dec 12, 1996

MSFC Earth-Sun Studies Featured at AGU







December 13, 1996

Fountains of electrified gases spewing from the Earth into space and pictures of the aurora during the day will be highlighted by the American Geophysical Union (AGU) annual winter conference in San Francisco Dec. 15-19.

AGU is one of the largest scientific bodies in the world and takes in everything from earthquakes to solar flares - including work by scientists at Marshall Space Flight Center's Space Sciences Laboratory (SSL) to understand what drives the aurora borealis and causes space storms that can black out cities.

At at three sessions during the AGU meeting, Marshall scientists will present their results in several papers, written with colleagues from other institutions, from the Thermal Ion Dynamics Experiment (TIDE) and the Ultraviolet Imager (UVI), two of several instruments aboard the Polar spacecraft launched in 1996.

TIDE recently confirmed that plasmas in the tail of the magnetosphere come from Earth's outer atmosphere being warmed by a flow of materials from space. The magnetosphere is formed by the Earth's magnetic field and buffers the planet from the constant wind of gases streaming from the sun.


Press briefings scheduled for the AGU Fall Meeting include:

Imaging Space Plasmas - Polar UVI and the Inner Magnetosphere Imager on which MSFC will have an important camera. Tuesday, Dec. 17, 12:45 p.m.

Sun-Earth Connections - the new era of coordinated solar-terrestrial research by scientists using Polar and other craft. Time TBD.

"There's a raging controversy over whether the magnetosphere stores energy to any degree, or just dissipates what the solar wind throws at it," said Dr. Tom Moore, director of the space plasma physics branch at SSL and principal investigator for TIDE.

Pictures from the UVI will help scientists decide whether the magnetosphere is driven directly by the solar wind, or it stores then discharges energy like a thunder cloud building a lightning charge.

"Northern winter traditionally has been the busy season for plasma scientists," said Dr. James Spann, a UVI co-investigator at SSL, "because that's when the aurora borealis is almost all in the night sky and can be viewed in visible as well as ultraviolet light."

UVI, included in three sessions at AGU, extends the busy season by letting scientists see what happens during the day. Doing this has been a challenge because the atmosphere's ozone layer reflects solar ultraviolet light that blinds most sensors. Previous instruments let scientists see parts of the daytime aurora, or the entire nightside auora. UVI aboard Polar is the first to show all of both day and nightside auroras. It does this with narrow bandpass filters - filters that admit narrowly define colors - that match lights emitted by the auroras.

UVI lets scientists measure, with precision, the energies flowing into the auroral oval. In addition to striking pictures, UVI reveals the footprint of the Earth's magnetic field lines that may stretch into deep space to several times the distance from Earth to Moon.