Cracks in Earth's Magnetic Shield
Immense cracks in our planet's magnetic field can remain open for
hours, allowing the solar wind to gush through and power stormy space
weather.
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Dec. 3, 2003:Â
Earth is surrounded by a magnetic force field--a bubble in space called
"the magnetosphere" tens of thousands of miles wide. Although many
people don't know it exists, the magnetosphere is familiar. It's a far
flung part of the same planetary magnetic field that deflects compass
needles here on Earth's surface. And it's important. The magnetosphere
acts as a shield that protects us from solar storms.
According to new observations, however, from
NASA's IMAGE spacecraft and the joint NASA/European Space Agency
Cluster satellites, immense cracks sometimes develop in Earth's
magnetosphere and remain open for hours. This allows the solar wind to
gush through and power stormy space weather.
Above: An artist's rendition of NASA's IMAGE satellite flying through a 'crack' in Earth's magnetic field. [
more]
"We've
discovered that our magnetic shield is drafty, like a house with a
window stuck open during a storm," says Harald Frey of the University of
California, Berkeley, lead author of a paper on this research published
Dec. 4 in Nature. "The house deflects most of the storm, but the couch
is ruined. Similarly, our magnetic shield takes the brunt of space
storms, but some energy slips through its cracks, sometimes enough to
cause problems with satellites, radio communication, and power systems."
"The
new knowledge that the cracks are open for long periods can be
incorporated into our space weather forecasting computer models to more
accurately predict how our space weather is influenced by violent events
on the Sun," adds Tai Phan, also of UC Berkeley, co-author of the
Nature paper.
The solar wind is a fast-moving stream of electrically
charged particles (electrons and ions) blown constantly from the Sun.
The wind can get gusty during violent solar events, like coronal mass
ejections (CMEs), which can shoot a billion tons of electrified gas into
space at millions of miles per hour.
Earth's magnetosphere
generally does a good job of deflecting the particles and snarled
magnetic fields carried by CMEs. Even so, space storms and their vivid
effects, like auroras which light up the sky over the polar regions with
more than a hundred million watts of power, have long indicated that
the shield was not impenetrable.
In
1961, Jim Dungey of the Imperial College, United Kingdom, predicted
that cracks might form in the magnetic shield when the solar wind
contained a magnetic field that was oriented in the opposite direction
to a portion of the Earth's field. In these regions, the two magnetic
fields would interconnect through a process known as "magnetic
reconnection," forming a crack in the shield through which the
electrically charged particles of the solar wind could flow.
Left:
An artist's rendition of magnetic reconnection. The amber-brown lines
denote lines of magnetic force. The bright spot is where
oppositely-directed fields are making contact and "reconnecting."
In
1979, Goetz Paschmann of the Max Planck Institute for Extraterrestrial
Physics in Germany detected the cracks using the International Sun Earth
Explorer (ISEE) spacecraft. However, since this spacecraft only briefly
passed through the cracks during its orbit, it was unknown if the
cracks were temporary features or if they were stable for long periods.
In
the new observations, the Imager for Magnetopause to Aurora Global
Exploration (IMAGE) satellite revealed an area almost the size of
California in the arctic upper atmosphere where a 75-megawatt "proton
aurora" flared for hours. A proton aurora is a form of Northern Lights
caused by heavy solar ions striking Earth's upper atmosphere,
causing it to emit ultraviolet light--invisible to the human eye but
detectable by the Far Ultraviolet Imager on IMAGE. While this aurora was
being recorded by IMAGE, the 4-satellite Cluster constellation flew far
above IMAGE, directly through the crack, and detected solar wind ions
streaming through it.
Below: An artist's rendition of the four Cluster satellites near
a stream of solar ions pouring in through a crack in the magnetosphere. [
more]
This
stream of solar wind ions bombarded our atmosphere in precisely the
same region where IMAGE saw the proton aurora. The fact that IMAGE was
able to view the proton aurora for more than 9 hours implies that the
crack remained continuously open. Researchers estimate that the crack
was twice the size of Earth at the boundary of our magnetic
shield--about 38,000 miles (60,000 km) above the planet's surface. Since
the magnetic field converges as it enters the Earth in the polar
regions, the crack narrowed to about the size of California down near
the upper atmosphere.
Fortunately, these cracks don't expose
Earth's surface to the solar wind. Our atmosphere protects us, even when
our magnetic field doesn't. The effects of solar storms are felt mainly
in the high upper atmosphere and the region of space around Earth where
satellites orbit.
Stay tuned later this week for a follow-up
story from Science@NASA about how magnetic cracks have lately sparked
beautiful auroras--a phenomenon of the upper atmosphere--in some
unexpected places.
more information
IMAGE was launched March 25, 2000, to provide a global view of the space around Earth influenced by the Earth's magnetic field. The
Cluster satellites, built by ESA, and launched July 16, 2000, are making a three-dimensional map of the Earth's magnetic field.
Click here for images, movies and more information.
The Sun Goes Haywire -- (Science@NASA)
Solar maximum is years past, yet the sun has been remarkably active lately. Is the sunspot cycle broken?
Solar
Superstorm -- (Science@NASA) Scientists are beginning
to understand a historic solar storm in 1859.
SpaceWeather.com -- current information about solar activity
and auroras
NOAA
Space Environment Center
-- the US government's official source of space weather data and forecasts
THE END
end quote from:
Dec 3, 2003 - California-sized cracks in our planet's magnetic field can remain ... Although many people don't know it exists, the magnetosphere is familiar.
begin quote:
Earth's Magnetic Shielding Has Been "Severely Compromised" -
It May Be In Danger!
1 November, 2012
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MessageToEagle.com - How long can we rely on the Earth's magnetosphere and its protection from the worst?
Russian space experts warn that our Earth’s magnetic shielding has been "severely compromised" and according to NASA scientists,
"the event began with little warning when a gentle gust of solar wind delivered a bundle of magnetic fields from the
Sun to Earth.
Like an octopus wrapping its tentacles around a big clam, solar magnetic fields draped themselves
around the [Earth’s] magnetosphere and cracked it open."
We have always believed that we are safe but that's not true!
The Earth's magnetosphere is leaking, the solar wind penetrates deeper. We are not entirely safe because weakened
field could leave our planet vulnerable to solar winds.
Click on image to enlarge
Southward Interplanetary Magnetic Field (IMF) Orientations Enable Solar Wind Energy to Enter
the Earth’s Magnetosphere. Credits: NASA
Earth is enveloped in a protective magnetic envelope called the magnetosphere. This can change
shape in response to the sun's effects, causing various types of space weather at Earth.
Earth's magnetic field is our planet's first line of defense - a shield - against the bombardment of the solar wind. This
stream of plasma is launched by the Sun and travels across the Solar System, carrying its own magnetic field with it.
Depending on how the solar wind's interplanetary magnetic field - IMF - is aligned with Earth's magnetic field, different
phenomena can arise in Earth's immediate environment.
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Cluster satellites, which have spent several years passing in and out of Earth's magnetic field, discovered that our
magnetic bubble is not uniform.
It allows solar wind to penetrate a wider range than previously thought. Our planet's protective magnetic bubble
lets the solar wind in under a wider range of conditions than previously believed.
How long the Earth's magnetosphere is able to protect us from the Sun's dangerous activities?
"The solar wind can enter the magnetosphere at different locations and under different magnetic field conditions
that we hadn't known about before," says co-author Melvyn Goldstein, also from Goddard Space Flight Center.
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In other words, bombardment of charged particles emitted by the solar wind and cosmic rays can surprise us and
badly affect our life on Earth.
In 2006, huge, 40 000 km swirls of plasma along the boundary of the magnetosphere - the magnetopause - could allow the
solar wind to enter, even when Earth's magnetic field and the interplanetary magnetic field (IMF) are aligned.
Kelvin-Helmholtz Wave Clouds Over Birmingham, Alabama – Dec 16, 2011 - the result of shearing winds up at cloud level.
These giant vortices are driven by a process known as the Kelvin-Helmholtz (KH) effect, which can occur anywhere
in nature when two adjacent flows slip past each other at different speeds.
Examples include waves whipped up by wind sliding across the surface of the ocean, or in atmospheric clouds.
Analysis of data gathered by Cluster satellites show that KH waves can also occur at a wider range of
magnetopause locations and when the IMF is arranged in a number of other configurations, providing a mechanism
for the continuous transport of the solar wind into Earth's magnetosphere.
"We found that when the interplanetary magnetic field is westward or
eastward, magnetopause boundary layers at
higher latitude become most subject to KH instabilities, regions quite
distant from previous observations of these
waves," said Kyoung-Joo Hwang of NASA's Goddard Space Flight Center and
lead author of the paper published in the Journal of Geophysical
Research.
"In fact, it's very hard to imagine a situation where solar wind plasma could not leak into the magnetosphere,
since it is not a perfect magnetic bubble."
"That suggests there is a 'sieve-like' property of the magnetopause in allowing the solar wind to continuously
flow into the magnetosphere."
Click on image to enlarge
When Earth’s magnetic field and the interplanetary magnetic field are aligned, for example in a northward orientation
as indicated by the white arrow in this graphic, Kelvin–Helmholtz waves are generated at low (equatorial) latitudes.
Credits: AOES Medialab
Recently, scientists discovered two large leaks in Earth's magnetosphere, the region around our planet that
shields us from severe solar storms. These leaks, found in an unexpected location, let in solar particles
in faster than expected and the whole interaction works in a manner that is completely the opposite of what
scientists had thought.
Also, scientists working with THEMIS data,
observed that Earth's magnetic field, which shields our planet from
particles streaming outward from the Sun,
develops two holes that allow the largest leaks, according to
researchers sponsored by NASA and the National Science Foundation.
Our magnetic field, on which we rely so much, is a leaky shield and the number of particles breaching this shield
depends on the orientation of the sun's magnetic field, NASA scientists say.
Click on image to enlarge
When the interplanetary magnetic field, indicated by the white arrow,
is oriented westward (dawnward) or in the opposite, eastward (duskward)
direction, magnetopause boundary layers at higher latitude become most
subject to Kelvin–Helmholtz instabilities.
Credits: AOES Medialab
It had been thought that when the sun's magnetic field is aligned with that of the Earth, the door is shut and
that few if any solar particles enter Earth's magnetic shield. The door was thought to open up when the solar
magnetic field direction points opposite to Earth's field, leading to more solar particles inside the shield.
"The discovery overturns a long-standing belief about how and when most of the solar particles penetrate Earth's
magnetic field, and could be used to predict when solar storms will be severe," according to Vassilis Angelopoulos
of the University of California, Los Angeles, Principal Investigator for NASA's THEMIS mission.
Artist's rendition of Earth's magnetosphere. Credits:http://sec.gsfc.nasa.gov
This discovery means that magnetic storms during the next solar cycle
maximum (~2012) could be stronger than the storms of the previous cycle.
"Twenty times more solar particles cross the Earth's leaky magnetic shield when the sun's magnetic field is aligned
with that of the Earth compared to when the two magnetic fields are oppositely directed," said Marit Oieroset of the
University of California, Berkeley, lead author of one of two papers on this research, published May 2008 in Geophysical
Research Letters.
Researchers have long suspected that this "closed door" entry mechanism might exist, but didn't know how important it was.
"It's as if people knew there was a crack in a levee, but they did not know how much flooding it caused," said Oieroset.
"We've found if the door is closed, the sun tears down a wall. The crack is huge – about four times wider than Earth
and more then seven Earth diameters long," said Wenhui Li of the University of New Hampshire, Durham, N.H.
end quote from:
www.messagetoeagle.com/magnetospherehowlong.php
Nov 1, 2012 - ... wrapping its tentacles around a big clam, solar magnetic fields draped themselves around the [Earth's] magnetosphere and cracked it open.".
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