POLAR AURORA
nature's wonder
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Magnetic Field Lines |
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The same process is also
essential to the aurora. We already mentioned large electric currents
flowing from the tail into the polar regions and back again, flowing
along magnetic field lines, earthward on the morning side of midnight,
outbound on the evening side (for the main circuit--a secondary one
also exists). They were first mapped in 1973 by two US scientists,
Al Zmuda and Jim Williamson--not with a well-supported space research
mission, but using a small experiment and a bummed "piggy-back" ride
with a navigational satellite of the US Navy. Those currents are
now known as "Birkeland currents, " honoring the Norwegian
who first shot electron beams at a magnet in vacuum. |
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©2006 Rae Brimer Gutierrez
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