26 January 2001
Vol 291, Issue 5504

About The Cover

Cover image expansion

COVER Earth's ring current, detected by NASA's IMAGE satellite from above the north pole. The circle at the grid's center represents Earth, with representative geomagnetic field lines extending to geocentric distances of 4 and 8 Earth radii. The charge exchange between ring current ions and ambient neutral hydrogen creates energetic neutral atoms that can be used to produce global images of this magnetospheric current system. False color shows the intensity of the neutral atom flux (green, most intense; purple, least intense). See page 619 [Image processing: D. G. Mitchell and P. C. Brandt]