"And there shall be signs in the sun,
and in the moon, and in the stars; and upon the earth
distress of nations, with perplexity; the sea and the
waves roaring; Men's hearts failing them for fear,
and for looking after those things which are coming on
the earth: for the powers of heaven shall be shaken."
Luke 21:25,26
NASA - Something
big is about to happen on the sun. According to
measurements from NASA-supported observatories, the sun's
vast magnetic field is about to flip.
"It looks like we're no
more than 3 to 4 months away from a complete field
reversal," says solar physicist Todd Hoeksema of
Stanford University. "This change will have ripple
effects throughout the solar system."
The sun's magnetic
field changes polarity approximately every 11 years.
It happens at the peak of each solar cycle as the sun's
inner magnetic dynamo re-organizes itself. The
coming reversal will mark the midpoint of Solar Cycle 24.
Half of 'Solar Max' will be behind us, with half yet to
come.
Hoeksema is the
director of Stanford's Wilcox Solar Observatory, one of
the few observatories in the world that monitor the sun's
polar magnetic fields. The poles are a herald of
change. Just as Earth scientists watch our planet's polar
regions for signs of climate change, solar physicists do
the same thing for the sun. Magnetograms at Wilcox have
been tracking the sun's polar magnetism since 1976, and
they have recorded three grand reversals—with a fourth in
the offing.
Solar physicist Phil
Scherrer, also at Stanford, describes what happens: "The
sun's polar magnetic fields weaken, go to zero, and then
emerge again with the opposite polarity. This is a regular
part of the solar cycle."
A reversal of the
sun's magnetic field is, literally, a big event. The
domain of the sun's magnetic influence (also known as the
"heliosphere") extends billions of kilometers beyond
Pluto. Changes to the field's polarity ripple all the way
out to the Voyager probes, on the doorstep of interstellar
space.
When solar
physicists talk about solar field reversals, their
conversation often centers on the "current sheet."
The current sheet is a sprawling surface jutting outward
from the sun's equator where the sun's slowly-rotating
magnetic field induces an electrical current. The
current itself is small, only one ten-billionth of an amp
per square meter (0.0000000001 amps/m2), but there’s a lot
of it: the amperage flows through a region 10,000 km thick
and billions of kilometers wide. Electrically
speaking, the entire heliosphere is organized around this
enormous sheet.
During field
reversals, the current sheet becomes very wavy. Scherrer
likens the undulations to the seams on a baseball.
As Earth orbits the sun, we dip in and out of the current
sheet. Transitions from one side to another can stir up
stormy space weather around our planet.
Cosmic rays are also
affected. These are high-energy particles accelerated to
nearly light speed by supernova explosions and other
violent events in the galaxy. Cosmic rays are a
danger to astronauts and space probes, and some
researchers say they might affect the cloudiness and
climate of Earth. The current sheet acts as a barrier to
cosmic rays, deflecting them as they attempt to penetrate
the inner solar system. A wavy, crinkly sheet acts as a
better shield against these energetic particles from deep
space.
As the field
reversal approaches, data from Wilcox show that the sun's
two hemispheres are out of synch.
"The sun's north
pole has already changed sign, while the south pole is
racing to catch up," says Scherrer. "Soon, however, both
poles will be reversed, and the second half of Solar Max
will be underway." When that happens, Hoeksema and
Scherrer will share the news with their colleagues and the
public. source- NASA