A Mars Odyssey

When images from NASA’s Polar spacecraft and the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft were analyzed, scientists were surprised to discover the northern and southern auroras were not mirror images as had previously been believed. The movements of the auroras are based upon the way the Earth’s magnetic field inclines toward the Sun as well as the conditions in the solar wind. Studying the relationship of the auroras to the solar wind will enable scientists to predict the effects of future space weather. Auroras form circular bands called auroral ovals around the north and south poles. These features are also called the aurora borealis, or northern lights, and aurora australis, or southern lights.

Lead author Timothy J. Stubbs of the Laboratory for Extraterrestrial Physics at NASA’s Goddard Space Flight Center explained, “This is the first analysis to use simultaneous observations of the whole aurora in both the Northern and Southern Hemispheres to track their location.”

The outer atmosphere of the Sun is a plasma of very thin electrified gas which, since it flows outward from the Sun at about 250 miles per second, is also called the solar wind When the solar wind flows into the Earth’s magnetic field, the Earth’s field is compressed into an elongated bubble known as the magnetosphere. Under most circumstances this magnetosphere acts as a shield to protect the planet from the solar wind, but, on occasion, when the conditions are favorable, the solar winds penetrate this barrier and particles become energized. When these energized particles hit the upper atmosphere of the Earth, the resulting light phenomena is referred to as an aurora.

The researchers noted the auroral ovals shift in opposite directions according to the relative position of the Interplanetary Magnetic Field (IMF), or the Sun’s magnetic field, coming from the Sun along with the solar wind. The ovals also move in opposite directions depending upon how far the North magnetic pole of the Earth is tilting towards the Sun. Some of the differences in the movements were due to the ability of the solar wind to penetrate one pole but not the other or to suspected imperfections in the Earth’s magnetic field. The magnetic field surrounding the Earth is similar to the field around a bar magnet which is revealed by the pattern iron filings will form around the magnet. Since the Earth’s magnetic field is not a perfect dipole, this imperfection could possibly be a factor in the auroras not being mirror images of each other.

This entry was posted on Wednesday, September 26th, 2007 at 11:40 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.