The aurora borealis, also known as the northern lights, has been a puzzle to
scientist for over 30 years. The mystery to science was how exactly the
phenomenon was started in the atmosphere. According to Space.com, scientists
were unsure if the aurora was started as magnetic field lines in the atmosphere
reconnected or if the aurora originated closer to Earth as the result of
explosive instability.
NASA used its five THEMIS spacecraft orbiting the Earth to spot the trigger
for the substorms that cause the aurora to develop. The trigger was very strong
energy bursts in the Earth’s magnetic field. The THEMIS probes monitored the
level of energy in the Earth’s magnetic field. The probes were able to find
substorms that originated in the tail of the Earth’s magnetosphere that flows
away from the sun.
As energy
levels in the magnetic field lines build the lines drew closer to each
other until they reconnected. Once the magnetic field lines reconnected a storm
was set off in the magnetosphere leading to the aurora borealis.
Space scientist Vassilis Angelopoulos from the University of California in
L.A. told Space.com, “We discovered what sparks the magnificent light
show of the aurora. Our data show clearly and for the first time that magnetic
reconnection is the trigger.”
According to the scientists, the better they can understand the storms that
spark the aurora, the better they will be able to prepare for or predict space
weather events that can interfere with communications and endanger any
astronauts in orbit at the time.
Angelopoulos continued saying, “We need to understand this environment and
eventually be able to predict when these large energy releases will happen so
astronauts can go inside their spacecraft and we can turn off critical systems
on satellites so they will not be damaged.”
The THEMIS spacecraft were launched in February 2007 specifically to hunt
for the cause of the substorms in the magnetosphere. The mission was set to
last two years. Another spacecraft called Image was to study the Earth’s
magnetosphere. Image
failed unexpectedly in 2006, but the mission was a success as the Image
spacecraft was only slated to operate for two years.