The "ring of fire" seen by satellite cameras around the polar caps (picture below) is probably created by electrons leaking from the tail's plasma sheet, whose magnetic field lines form a somewhat imperfect trap. ... One possible explanation involves the close association between auroral arcs and electric currents which flow along field lines between the ionosphere and distant space ( Birkeland currents ). ... That produces an extra resistance to the flow of current. ...

... Jupiter's big moon Ganymede is not only the size of a planet -- it sounds like one too, as heard in audio recordings made from data returned by NASA's Galileo spacecraft released today. ... Characterized by a soaring whistle and hissing static, Ganymede's song reveals that the Solar System's largest moon is also the only one known to possess a planet-like, self-generated magnetic cocoon called a magnetosphere , which shields the moon from the magnetic influence of its giant parent body, Jupiter. ...

... Spacecraft . 29a. Satellite looking up . ... 29e. Explorers of distant space . Space Index . ... Many "down-looking" satellites also carry out local observations, among them Polar, Viking, Freja and satellites of the GOES and DMSP series. ... Other explorers of the distant magnetosphere have included the three ISEE spacecraft (International Sun-Earth Explorers), Polar in an elliptical polar orbit with cameras observing the polar aurora, and Image observing energetic neutral atoms. ...

Cosmic Research, Vol. 42, No. 5, 2004, pp. 435­488. Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 5, 2004, pp. 453­508. Original Russian Text Copyright © 2004 by Veselovsky, Panasyuk, Avdyushin, Bazilevskaya, Belov, Bogachev, Bogod, Bogomolov, Bothmer, Boyarchuk, Vashenyuk, Vlasov, Gnezdilov, Gorgutsa, Grechnev, Denisov, Dmitriev, Dryer, Yermolaev, Eroshenko, Zherebtsov, Zhitnik, Zhukov, Zastenker, Zelenyi, Zeldovich, Ivanov-Kholodnyi, Ignat'ev, Ishkov, Kolomiytsev, Krasheninnikov, Kudela,