Northern Lights Dance In X-Ray Light
In an unusual observation, a team of scientists has scanned the
northern polar region of Earth with NASA's Chandra X-ray
Observatory. The results show that the aurora borealis, or
"northern lights," also dance in X-ray light, creating changing
bright arcs of X-ray energy above the Earth's surface.
While other satellite observations had previously detected
high-energy X-rays from the Earth auroras, the latest Chandra
observations reveal low-energy X-rays generated for the first time
during auroral activity.
The researchers -- led by Dr. Ron Elsner of NASA's Marshall
Space Flight Center in Huntsville, AL -- used Chandra to observe
the Earth 10 times over a four-month period in 2004. The images
were created from approximately 20-minute scans during which
Chandra was aimed at a fixed point in the sky and the Earth's
motion carried the auroral regions through Chandra's field of
Auroras are produced by
solar storms that eject clouds of energetic charged particles.
These particles are deflected when they encounter the Earth's
magnetic field, but in the process large electric voltages are
created. Electrons trapped in the Earth's magnetic field are
accelerated by these voltages and spiral along the magnetic field
into the polar regions. There they collide with atoms high in the
atmosphere and emit X-rays. Chandra has also observed dramatic
auroral activity on Jupiter.
Dr. Anil Bhardwaj is the lead author on a paper describing these
results in the Journal of Atmospheric and Solar-Terrestrial
Physics. Dr. Bhardwaj was a co-investigator on this project
and worked with Dr. Elsner at NASA's Marshall Space Flight Center
while this research was conducted.
The research team also includes Randy Gladstone, Southwest
Research Institute, San Antonio, Texas; Nikolai �stgaard,
University of Bergen, Norway; Hunter Waite and Tariq Majeed,
University of Michigan, Ann Arbor; Thomas Cravens, University of
Kansas, Lawrence; Shen-Wu Chang, University of Alabama, Huntsville;
and Albert E. Metzger, Jet Propulsion Laboratory, Pasadena,
NASA's Marshall Space Flight Center, Huntsville, AL, manages the
Chandra program for the agency's Science Mission Directorate. The
Smithsonian Astrophysical Observatory controls science and flight
operations from the Chandra X-ray Center in Cambridge, MA.