charles@utastro.UUCP (Charles Sandel) (08/20/84)
The solar wind influences both the Earth --
and the sun. We'll talk about it --
right after this.
August 20 The Solar Wind
Occasionally gigantic flares are seen on the sun
-- and, a day or so later,
people in Earth's northern hemisphere often see an intense display of the
aurora borealis, or northern lights.
It took many decades to interpret this clue --
but it's now known that flares on the sun
eject charged particles -- protons and electrons -- at high speeds.
The particles reach the vicinity of the Earth a day or two later.
Some become trapped in Earth's magnetic field
and cascade down along field lines
toward the Earth's magnetic poles.
When energetic particles such as these
from the sun strike the atmosphere of the Earth,
they cause it to fluoresce, or glow --
for much the same reason that fluorescent light bulbs glow.
Then we here on Earth see the northern lights.
So, spectacular displys of northern lights result from solar flares --
which eject charged particles from the sun at high speeds.
Such solar flares can also cause radio blackouts on our world.
But even when the sun is relatively quiet,
steady streams of electrons and protons flow from the sun --
this outflow is called the "solar wind."
The solar wind not only affects the Earth and other planets --
it also acts to slow the sun's rotation.
As the solar wind moves outward
from the sun, it acts like the outspread arms
of a spinning ice skater to slow down the rotation of the sun.
In the nearly five billion years since the sun was formed,
its spin has been reduced by the solar wind -- perhaps so much that
the sun now rotates at only one per cent of its original speed.
Script by Joe Patterson and Deborah Byrd.
(c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin
--
*>> Charles Sandel <<*
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