by Dr. Tony Phillips
October 31, 2008
An artist's concept of Earth's magnetic field
connecting to the sun's - aka a
"flux transfer event" - with
a spacecraft on hand to measure
particles and fields.
During the time it takes you to read this article, something will
happen high overhead that until recently many scientists didn't
believe in. A magnetic portal will open, linking Earth to the sun 93
million miles away.
Tons of high-energy particles may flow through the
opening before it closes again, around the time you reach the end of
"It's called a flux transfer event or 'FTE',"
says space physicist David Sibeck of the Goddard Space Flight
Center. "Ten years ago I was pretty sure they didn't exist, but
now the evidence is incontrovertible."
Indeed, today David Sibeck is telling an
international assembly of space physicists at the 2008 Plasma
Workshop in Huntsville, Alabama, that FTEs are not just common, but
possibly twice as common as anyone had ever imagined.
Researchers have long known that the Earth and sun must be
Earth's magnetosphere (the magnetic
bubble that surrounds our planet) is filled with particles from the
sun that arrive via
the solar wind and penetrate the
planet's magnetic defenses.
They enter by following magnetic field lines that can
be traced from terra firma all the way back to the sun's atmosphere.
"We used to think the connection was permanent
and that solar wind could trickle into the near-Earth
environment anytime the wind was active," says Sibeck.
"We were wrong. The connections are not steady at
all. They are often brief, bursty and very dynamic."
Several speakers at the Workshop have outlined how
On the dayside of Earth (the side closest to the
sun), Earth's magnetic field presses against the sun's magnetic
Approximately every eight minutes, the two fields
briefly merge or "reconnect," forming a portal through which
particles can flow. The portal takes the form of a magnetic
cylinder about as wide as Earth.
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.
"They're real," says Sibeck.
Now that Cluster and THEMIS have directly sampled
FTEs, theorists can use those measurements to simulate FTEs in their
computers and predict how they might behave.
Space physicist Jimmy Raeder of the University
of New Hampshire presented one such simulation at the Workshop. He
told his colleagues that the cylindrical portals tend to form above
Earth's equator and then roll over Earth's winter pole:
Sibeck believes this is happening twice as often as
"I think there are two varieties of FTEs: active
Active FTEs are magnetic cylinders that allow
particles to flow through rather easily; they are important
conduits of energy for Earth's magnetosphere
Passive FTEs are magnetic cylinders that
offer more resistance; their internal structure does not
admit such an easy flow of particles and fields (for
experts: Active FTEs form at equatorial latitudes when the
IMF tips south; passive FTEs form at higher latitudes when
the IMF tips north)
Sibeck has calculated the properties of passive FTEs
and he is encouraging his colleagues to hunt for signs of them in
data from THEMIS and Cluster.
"Passive FTEs may not be very important, but
until we know more about them we can't be sure."
There are many unanswered questions:
"We're doing some heavy thinking about this at
the Workshop," says Sibeck.
Meanwhile, high above your head, a new portal is
opening, connecting your planet to the sun