He said the outflow of electrons, while unanticipated, actually fit with observations from the Voyager flybys.
The magnetic field is also not as uniform as expected. “We find the spatial variations in the magnetic field that are intriguing,” Dr. Connerney said. “We see the field is stronger in magnitude than we expected in some places, much weaker than we expected in other places.”
The magnetic field is generated by the churning of electrically charged fluids at the core. On Earth, that comes from the convection of molten iron in the outer core. On Jupiter, the currents come from hydrogen, the planet’s prime constituent, which turns into a metallic fluid under crushing pressures.
For the magnetic field measurements, a glitch that has greatly slowed the pace of data gathering could turn out to be beneficial. A final engine burn last October was to put Juno in a 14-day orbit, but a pair of sluggish valves in the fuel system led mission managers to forgo that, and Juno remains in a 53-day orbit instead. The spacecraft is to make the same number of orbits and collect the same amount of data.
The longer mission means that Juno may be able to detect slow changes in the magnetic field. “That would be intriguing as well,” Dr. Connerney said.
The chaotic pattern of storms detected by Juno is also a surprise. Planetary scientists had wondered whether Jupiter would have a giant hexagonal pattern like that spotted on Saturn by NASA’s Cassini spacecraft.
On Wednesday, NASA released new images of Saturn’s north polar region, which has changed color in the last four years,…