Tag Archives: Astronomy

http://science.nasa.gov/science-news/science-at-nasa/2008/30oct_ftes/

Good morning readers.  I’m going to have to kick this around with Old Sol while I’m coaxing him up this morning.  Meanwhile, I’ll tell you it’s nice seeing something coming out of NASA occasionally a person could consider useful and exciting.

The whole 2008 business about the 8 minute cycling had completely escaped my notice until I came across this at http://spaceweather.com/this morning.

HIDDEN PORTALS IN EARTH’S MAGNETIC FIELD: A NASA-sponsored researcher at the University of Iowa has developed a way for spacecraft to hunt down hidden magnetic portals in the vicinity of Earth. These gateways link the magnetic field of our planet to that of the sun, setting the tage for stormy space weather. [video]

Then, a bit of searching turned up this:

Magnetic Portals Connect Earth to the Sun

 http://science.nasa.gov/science-news/science-at-nasa/2008/30oct_ftes/

“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 FTEs form: On the dayside of Earth (the side closest to the sun), Earth’s magnetic field presses against the sun’s magnetic field. 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. In December, FTEs roll over the north pole; in July they roll over the south pole.

Sibeck believes this is happening twice as often as previously thought. “I think there are two varieties of FTEs: active and passive.” 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: Why do the portals form every 8 minutes? How do magnetic fields inside the cylinder twist and coil? “We’re doing some heavy thinking about this at the Workshop,” says Sibeck.

If NASA’s going to be throwing money around like a drunken sailor it’s good to know sometimes it hits something worth knowing.  Even a blind hog finds an acorn now and then, I reckons.

Old Jules