Data on the Sun's activities during a recent series of strong solar storms were gathered by an entire fleet of NASA's Sun-Earth Connection spacecraft. The atmospheric data from NASA's newest solar spacecraft, TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics), is providing important new information on the final link in the Sun-Earth Connection chain of physical processes that connect the Sun and Earth.

An artist's concept of the TIMED saatellite deployed in space. Photo: JHU/APL

"Several NASA spacecraft observed this strong activity as it came from the Sun. Now TIMED provides the critical link between what happened on the Sun and Earth's response," said Sam Yee, leader of TIMED's science team, at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

"TIMED allows us to observe the global reaction of our upper atmosphere to solar activity," said Mary Mellott, TIMED program scientist, NASA Headquarters in Washington. "One of the important current puzzles for the Sun-Earth Connection (SEC) community is determining why some solar activity has significant geospace impact and some does not. Being able to monitor the impact so well with TIMED should allow the scientific community to make significant progress toward solving this SEC mystery."

Along with TIMED, a fleet of observatories in space and on the ground observed a powerful flare April 21 as part of the Max Millennium program. The program, sponsored by NASA as part of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) mission, focuses on solar active regions with the potential to produce storm activity. Every 24 hours, an e-mail message with the current target is sent to participating observatories so that coordinated observations can be made.

The Transition Region and Coronal Explorer spacecraft got a close-up look at the flare and its aftermath, while RHESSI recorded flashes of X-rays that reveal impulsive energy- release processes in flares, and the Solar and Heliospheric Observatory (SOHO) got the big-picture view, including the ejection of electrified gas clouds into space. Additional observatories on the ground participated, like the Nobeyama Radio Observatory, Nagano, Japan, which tracked radio emission from the flare and its aftermath. Other spacecraft near Earth, like the Advanced Composition Explorer (ACE), the Imager for Magnetopause to Aurora Global Exploration (IMAGE), and the Polar and Wind spacecraft, will be consulted to determine the effects on the Earth.

"Detailed modeling using data from the many instruments will take a long time, but it may help us in understanding the basic processes at play during a solar explosion, called a solar flare," said Stein Vidar Hagfors Haugan, a SOHO scientist based at NASA's Goddard Space Flight Center, Greenbelt, Md. "The idea is that observing more pieces of the same picture is a lot better than observing the same number of pieces of different pictures at different times."

Preliminary TIMED data was featured in a special session at the Spring 2002 American Geophysical Union meeting in Washington. TIMED, the first of NASA's Solar Terrestrial Probes missions, began its science mission in January 2002 and studies the influences of both the Sun and humans on one of the Earth's least understood atmospheric regions -- the Mesosphere and Lower Thermosphere/Ionosphere (MLTI) -- the gateway between Earth's environment and space. The MLTI region is located approximately 40-110 miles (60-180 kilometers) above the surface of the Earth.

Space weather in Earth's upper atmospheric regions can affect satellite communications and orbital tracking, spacecraft lifetimes and the reentry of piloted vehicles. "When a change occurs in one region of our atmosphere, it affects other regions," Yee says. "It's important that we better understand how this gateway region responds to various solar inputs, which affect our atmosphere's overall energy balance."