Taking Pictures Of The Invisible Tracking Weather Above The Sky

Los Alamos' research was presented today at the Fall Meeting of the American Geophysical Union in San Francisco.

Developing what he calls "weather maps for the radiation belts," Geoff Reeves of the Los Alamos Space and Atmospheric Sciences group and Mike Henderson of Los Alamos' Space and Remote Sensing Sciences group devised a way to take rough, low-resolution satellite data and create more informative composite images of the solar-wind-driven particles trapped in the magnetosphere.

Used as still pictures or animated for time-lapse movies, their pictures show the ebb and flow of these particles as they near the earth and are drawn around and down the magnetic field lines. These images are especially critical for understanding the progress and structure of a space phenomenon called geomagnetic storms.

Geomagnetic storms are the space equivalent of hurricanes in the Atlantic. For years scientists believed that geomagnetic storms were made up of smaller "substorms" which occur more frequently and in isolation. But more recently scientists have found that storms and substorms are related - but distinctly different - phenomena. This is similar to discovering that hurricanes and thunderstorms are related, but that a hurricane is not just a cluster of thunderstorms or a larger, more intense thunderstorm.

"In this research we have discovered that geomagnetic storms and substorms both inject protons into the radiation belts with about the same intensity, but in storms the injection takes place over a much larger area, moves through the radiation belts in a different way and lasts for a longer period of time," Reeves explained. "While some of these results were suspected before, neutral atom imaging has allowed us to 'see' the process and study it in detail for the first time."

Understanding how protons move around the earth during and after solar storms can provide protective navigation guidance to satellites, permit scheduling of astronauts' space walks at safer times and alert researchers to shield vulnerable satellite instruments.

The Earth's magnetosphere is composed of electrons and ions that are "trapped" on magnetic field lines that balloon out from the earth's poles. The magnetosphere is a large-scale and dynamic system, but to study it scientists have relied on a limited number of single-point satellite measurements.

Neutral atom imaging takes advantage of rare collisions, called charge-exchange collisions, between magnetospheric ions and atoms that have escaped from the Earth's atmosphere. The newly-created neutral atoms are collected from remote locations to create images of the magnetosphere.

To understand the neutral atom imaging process, think of a video camera collecting light particles, called photons. The more photons the camera collects the brighter the image. The camera converts those photons to a digital signal that indicates how bright the light coming from a particular direction is. The Los Alamos imager works in a similar way except that, instead of collecting photons, it collects neutral atoms from the magnetosphere and indicates how many of those come from a particular direction.

Assimilation of this data into computer models is producing remarkable insights into geophysical processes, Reeves said.

"Seeing the effect of these geomagnetic storms allows us to better assess the space environment and its effects on the operation and health of military and commercial satellites," he noted.

Future missions to the magnetosphere will carry dedicated, Los Alamos-designed, neutral atom imaging instruments. These include NASA's IMAGE mission and TWINS, which will provide the first stereoscopic images of the magnetosphere.

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.