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Imaging The Invisible: A New Look At Space Weather

March 31, 2003

How is it possible to image tiny particles that are normally invisible? What happens to our planet and its surroundings when huge solar storms collide with Earth's magnetic shield? These are just some of the questions that will be addressed this week during the UK/Ireland National Astronomy Meeting in Dublin.

Our Earth is continually buffeted by a stream of energy in the form of electromagnetic radiation (photons) and electrically charged particles from the Sun (the solar wind). Sometimes huge clouds erupt from the Sun's turbulent atmosphere, sending one thousand million tonnes of gas hurtling towards our world at speeds of anything up to 2000 km/s. Higher levels of electromagnetic radiation accompany these high speed clouds.

Apart from creating the beautiful auroras (Northern and Southern Lights), space weather events such as these can disrupt power grids, interfere with navigation and communication systems, and disable satellite control systems, so it is becoming increasingly important for operational reasons to understand what happens when these storms arrive at the Earth.

Until recently, it has been extremely difficult to monitor the drastic, global-scale changes in the temperature and composition of Earth's upper atmosphere and magnetosphere resulting from electromagnetic radiation and plasma (electrified gas) emanating from the Sun.

Now, revolutionary new satellite technology is revealing the secrets of this ever-changing interaction. On Tuesday 8 April, Dr. Robert Meier (U.S. Naval Research Laboratory) will be presenting examples of recent space weather images from the NASA TIMED and IMAGE missions.

"Satellite imagery provided meteorology with a dramatic step forward nearly 50 years ago, by enabling a global context for weather studies," explained Dr. Meier. "New imaging instruments now being placed into Earth orbit are affording the space weather community a similar step forward."

"Remote sensing of the space environment near Earth is crucial in order to give us the global perspective needed to interpret and forecast numerous space weather phenomena and their impacts on society," he said.

Observations by the NASA IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite have shown spectacular global-scale changes in the Earth's magnetosphere during geomagnetic storms. They reveal that the solar wind compresses and distorts the magnetosphere, allowing large amounts of plasma (electrified gas) and magnetic energy to be transferred into the Earth system.

Large streams of charged particles flow from the inner to the outer magnetosphere. And large regional space weather systems are initiated at altitudes between 100 and 1000 km as streams of energetic particles pour in from the magnetosphere above the Earth's magnetic poles. These particles, along with heating by electrical currents, cause upwelling that changes the composition and temperature of the upper atmosphere, producing weather fronts.

Meanwhile, data from the NASA TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) satellite are revealing details of weather events in the upper atmosphere and ionosphere that have never been seen before. Large-scale changes are seen in images of atmospheric composition that show gases moving from polar regions toward the equator at altitudes above 100 km. Depletions in the electron density take place in these areas of disturbed space weather.

TIMED images also show for the first time magnetic fields in the ionosphere, much like iron filings on paper reflect the presence of a nearby magnet.

"These new missions allow us to expand our concept of weather to tens of thousands of km above the Earth's surface," said Meier.

Royal Astronomical Society (RAS)