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EARTH'S
AURORAS MAKE RARE JOINT APPEARANCE IN A FEATURE FILM Scientists
using NASA's Polar spacecraft have captured the first-ever movie of auroras dancing
simultaneously around both of Earth's polar regions. During a space weather storm
on October 22, Polar's Visible Imaging System observed the aurora borealis
and aurora australis (northern and southern lights) expanding and brightening
in parallel at opposite ends of the world. The images confirm the three-century
old theory that auroras in the northern and southern hemispheres are nearly mirror
images -- conjugates - of each other. "This
is the first time that we have seen both auroral ovals simultaneously with such
clarity," says Dr. Nicola Fox, the science operations manager for the Polar
spacecraft, based at NASA Goddard Space Flight Center. "With these images,
we have the ability to see the dynamics of conjugate auroras."
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2 | | | Auroras
occur when fast-moving particles trapped in Earth's magnetic field come crashing
down into the gases of Earth's upper atmosphere. Those particles (electrons and
protons) can only move along the invisible magnetic field lines, which are connected
to Earth near the North and South poles. When a space weather event pours energy
into the space around Earth and energizes the magnetic field, those particles
travel to both ends of the field lines, creating auroral displays in approximately
2500 mile diameter rings encircling each pole. "For
the first time, the northern and southern auroral ovals were observed simultaneously
with enough resolution to confirm that the northern and southern aurora are mirror
images of each other on a global scale," says Dr. John Sigwarth, a space
physicist at the University of Iowa who helped design and operate the VIS cameras.
"Further analysis of these images should help us determine if the all of
the auroral features are exactly mirrored down to the finest detail." Preliminary
research suggests that while the auroras mimic each other on broad scales, there
are also some fine features that do not match.
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3 | | | The
first recorded sighting of conjugate auroras occurred in September 1770, during
the expeditions of Captain James Cook. While exploring Australia and the South
Pacific on the HMS Endeavour, Cook's crew noted "a phenomenon appeared in
the heavens in many things resembling the Aurora Borealis." Later studies
of the Qing-shigao, a draft history of the Chinese Qing Dynasty, revealed
that an aurora was observed on the same night - September 16, 1770 - in the northern
hemisphere.
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4 | | | In
the years since then, scientists have conducted ground- and aircraft-based studies
of simultaneous auroras in both hemispheres. In the 1980s, NASA's Dynamics Explorer
spacecraft snapped three images of auroral crowns around both poles, but those
images were taken on different days and times and did not allow researchers to
study the variations of the ovals. Polar
was launched by NASA in 1996 to study the aurora, the radiation belts, and other
phenomena in the space around Earth. Back
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