The mission will launch in 2014 and consists of four identical satellites that will orbit in Earth’s magnetosphere where they will surround the portals and observe how they work. The portals that connect the Earth and sun create an uninterrupted path between the two. They are invisible and will open and close without warning. Some portals are short-lived while others are vast and sustained, according to NASA.. Its 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 didnt exist, but now the evidence is incontrovertible. Indeed, today 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 connected. Earths magnetosphere (the magnetic bubble that surrounds our planet) is filled with particles from the sun that arrive via the solar wind and penetrate the planets magnetic defenses. They enter by following magnetic field lines that can be traced from terra firma all the way back to the suns 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 FTEs form: On the dayside of Earth (the side closest to the sun), Earths magnetic field presses against the suns 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 Agencys fleet of four Cluster spacecraft and NASAs five THEMIS probes have flown through and surrounded these cylinders, measuring their dimensions and sensing the particles that shoot through. Theyre 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 Earths equator and then roll over Earths 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 Earths magnetosphere. Passive FTEs are magnetic cylinders that offer more resistance; their internal structure does not admit such an easy flow of particles and fields. 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 cant 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? Were doing some heavy thinking about this at the Workshop, says Sibeck.
Posted on: Sun, 15 Jun 2014 06:52:23 +0000
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