Like giant,
cosmic chutes between the Earth and sun, magnetic portals open up every eight
minutes or so to connect our planet with its host star.
Once the
portals open, loads of high-energy
particles can travel the 93 million miles (150 million km) through the
conduit during its brief opening, space scientists say.
Called a
flux transfer event, or FTE, such cosmic connections not only exist but are
possibly twice as common as anyone ever imagined, according to space scientists
who attended the 2008 Plasma Workshop in Huntsville, Ala., last week.
"Ten
years ago I was pretty sure they didn't exist, but now the evidence is
incontrovertible," said David Sibeck, an astrophysicist at the Goddard
Space Flight Center in Maryland.
Dynamic
bursts
Researchers
have long known that the Earth and sun must be connected. For instance,
particles from the sun are constantly whisked away via the solar wind and often
follow magnetic field lines that connect the sun's
atmosphere with terra firma. The field lines allow particles to penetrate Earth's
magnetosphere, the magnetic bubble that surrounds our planet.
"We
used to think the connection was permanent and that solar wind could trickle
into the near-Earth environment anytime the wind was active," Sibeck said.
"We were wrong. The connections are not steady at all. They are often
brief, bursty and very dynamic."
Several
speakers at the workshop outlined the formation of a flux transfer event. One
idea is that on the side of Earth facing the sun, our magnetic field presses against the sun's magnetic field. And about every eight minutes, the two fields briefly reconnect,
forming a portal through which particles can flow. The portal takes the form of
a magnetic cylinder about as wide as Earth.
Sibeck said
to think of the FTE as a giant rolling pin that lies flat along the boundary
between the Earth's and sun's magnetic fields. (He noted the rolling pin would
have to be malleable so it could pierce through both magnetic fields while
lying flat.)
"These
FTEs kind of look like roller pins, and they form as little blob roller pins at
the tip of the magnetosphere facing the sun," Sibeck told SPACE.com.
"They can't decide which way they're going to slide around the Earth, so they
grow there into big roller pins and then they take off and sort of spirally
roll along [Earth's magnetosphere] like you're pounding out dough."
More than
one FTE can form at once, he said, and they stay open for about 15 to 20
minutes.
More to
learn
In order to
measure such FTEs, spacecraft must not only catch them forming but also be on
either end of the magnetic structures (either lengthwise or widthwise). In
fact, the European Space Agency's fleet of four Cluster spacecraft and NASA's
five THEMIS
probes have flown through and surrounded these cylinders, measuring their
dimensions and sensing the particles that shoot through, Sibeck said. While
these measurements have nailed down the width of an FTE, the length is still
uncertain though one measurement put it at up to five Earth radii. One Earth
radius is about 4,000 miles (6,400 kilometers).
Astrophysicist
Jimmy Raeder of the University of New Hampshire used those measurements to
develop computer simulations of the portals. He found the cylindrical portals
tend to form above Earth's equator and then in December, the FTEs would roll over
the North Pole. In July, they roll over the South Pole.
Sibeck thinks
the events occur twice as often as previously thought, proposing two types of
flux transfer events — active and passive.
When the
magnetic cylinders are active, they allow particles to flow through rather
easily, forming important conduits of energy for Earth's magnetosphere, Sibeck
said. When passive, the cylinders have more resistance to transiting particles.
The internal structure of a passive cylinder makes it tougher for particles and
magnetic fields to flow through. Sibeck has calculated the properties of passive
FTEs and hopes he and his colleagues will hunt for signs of them in data
collected with THEMIS and Cluster.
The space
scientists at the workshop still want to figure out why the portals form every
eight minutes and how magnetic fields inside the cylinders twist and coil.
advertisement
