500 million miles away
The KiNET-X experiment might also help scientists understand a curious aurora process at our solar system's largest planet
(Inaudible) copies, we will be picking up the count at 00:34 (universal time, which is 8:34 p.m. Eastern time). Should we be planning to hold at T minus 3 minutes?
Only under my orders. Otherwise, we’ll roll.
JUPITER, THE LARGEST PLANET in our solar system, has 95 moons recognized by the International Astronomical Union.
One is of particular interest to scientists such as Delamere because of its powerful relationship to its parent planet.
Its name is Io, and it figures into the KiNET-X mission.
Color images acquired on September 7, 1996 have been merged with higher resolution images acquired on November 6, 1996 by the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. NASA/JPL/University of Arizona photo
“There's so much we don't understand about the Io-Jupiter interaction,” Delamere said. “When we can understand the Io-Jupiter interaction, which to me is the simplest auroral problem in the heliosphere, we can really start to make progress on more general auroral phenomena, even in our terrestrial magnetosphere.”
KiNET-X could lead to a better understanding of that planet-moon duo an average of 484 million miles from Earth.
“Energy transfer is the most fundamental problem in auroral physics,” Delamere said. “The Io-Jupiter interaction, in my opinion, is the simplest place to start, because we know the kind of the energy input and because we understand all the properties of the plasma interaction.”
“KiNET-X is probably more similar to the way that Jupiter interacts with Io,” he said. “You can think of Io and its atmosphere as the barium cloud released in our experiment, and Jupiter's inner magnetosphere being Earth's ambient atmosphere.”
Io, only slightly larger than Earth’s moon, is a generator of intense plasma and the source of a strong electric current known as the Io flux tube, which is a major supply line for creation of Jupiter’s aurora.
The Io flux tube facilitates the transfer of electromagnetic energy and particles from the moon to Jupiter’s polar regions through Alfvén waves, which oscillate through the parallel magnetic and electric fields.
It’s the same with Earth’s aurora, though our planet’s aurora energy comes solely from the sun.
Io also produces a plasma ring that encircles Jupiter in Io’s orbit like a doughnut and comes from the moon’s ejection of neutrally charged volcanic material, which becomes ionized. That ionization occurs primarily through electron impact, a process in which an atom or molecule loses one or more electrons after being struck by a high-energy, fast-moving free electron.
A NASA drawing illustrates how flows of electrons steered by Jupiter's magnetic field connect three of Jupiter's large moons with the upper atmosphere near Jupiter's north and south poles. The currents stimulate ultraviolet aurora glows in Jupiter's upper atmosphere. Observations with NASA's Hubble Space Telescope, coordinated with the late 2000 flyby of Jupiter by NASA's Cassini spacecraft, captured those auroral footprints for the moons Io (left), Europa (right) and Ganymede (center). In the illustration, Jupiter's magnetic field lines are presented in blue, the moons' orbital paths around Jupiter in yellow. Pink loops from each of the moons to Jupiter's poles depict the flux tubes that are the paths of powerful electric currents.
The plasma ring, known as the Io plasma torus, is constantly losing particles through a variety of processes. Some of those ionized particles get drawn to Jupiter’s poles to create the aurora, joining material supplied through the Io flux tube.
“We don't exactly understand how that transport from Io happens,” Delamere said. “It's that transport problem that produces Jupiter's aurora that's analogous to Earth’s.”
Although the plasma torus continually loses particles, it is kept stable by a replenishment from the moon. Io is the solar system’s most volcanically active body.
One of the most striking aspects of Io’s influence on Jupiter is the distinct bright spot, called a footprint, it leaves in Jupiter’s auroras due to the moon's interaction with the planet's magnetic field. Two other Jovian moons, Europa and Ganymede, create footprints that are not nearly as luminous as Io’s.
“If our moon did that we'd have bright aurora that would sweep periodically through our skies that are magnetically connected to the moon,” Delamere said. “But our moon is far, far out there, and it doesn't have active volcanoes on it like Io producing all of this very dense neutral gas that gets ionized.”
