Passage to a Ringed World - NASA's History Office
Passage to a Ringed World - NASA's History Office
Passage to a Ringed World - NASA's History Office
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An artist’s rendition<br />
of Saturn’s<br />
immense magne<strong>to</strong>sphere.<br />
Ω is the S<br />
planet’s rotation<br />
axis, closely<br />
aligned with the<br />
magnetic axis. [Image<br />
courtesy of<br />
Los Alamos National<br />
Labora<strong>to</strong>ry]<br />
CHAPTER 6<br />
Saturn, its moons and its awesome rings sit inside an<br />
enormous cavity in the solar wind created by the planet’s<br />
strong magnetic field. This “sphere of influence” of Saturn’s<br />
magnetic field — called a magne<strong>to</strong>sphere — resembles<br />
a similar magnetic bubble surrounding Earth.<br />
Inside the Magne<strong>to</strong>sphere<br />
Inside Saturn’s vast magne<strong>to</strong>spheric<br />
bubble is a mixture of particles, including<br />
electrons, various species<br />
of ions and neutral a<strong>to</strong>ms and molecules,<br />
several populations of very energetic<br />
charged particles (like those in<br />
Earth’s Van Allen Belts) and charged<br />
dust grains. The charged particles<br />
and dust grains all interact with both<br />
the steady and the fluctuating electric<br />
Solar Wind<br />
Solar Wind<br />
Fast Neutrals<br />
Pickup Ions<br />
A Sphere of Influence<br />
Bow Shock<br />
Aurora<br />
Ring Current<br />
H + , He ++<br />
and magnetic fields present throughout<br />
the magne<strong>to</strong>sphere.<br />
These ionized gases contain charged<br />
particles (electrons and ions) such as<br />
occur in the solar wind and planetary<br />
magne<strong>to</strong>spheres and are called plasmas.<br />
The steady fields can cause<br />
organized motions of the charged<br />
particles, creating large currents in<br />
the plasma.<br />
Cusp Polar Wind<br />
SKR<br />
H + , He ++<br />
Aurora<br />
Ω S<br />
Titan Tail<br />
Titan Neutral<br />
Torus<br />
Magne<strong>to</strong>sheath<br />
H + , He ++<br />
H + + + , H , H3<br />
2<br />
Magne<strong>to</strong>pause<br />
The region is not at all spherical; rather, the supersonic<br />
solar wind, flowing at 300–1000 kilometers per second<br />
against Saturn’s magnetic field, compresses the magne<strong>to</strong>sphere<br />
on the side facing the Sun and draws it out in<strong>to</strong> a<br />
long magne<strong>to</strong>tail in the direction away from the Sun.<br />
H + + + , H , H3<br />
2<br />
Planetary Ions<br />
Plasma Sheet<br />
Plasma behavior is more complex<br />
than that of neutral gases because,<br />
unlike neutral particles, the charged<br />
particles interact with each other<br />
electromagnetically as well as with<br />
any electric and magnetic fields<br />
present. The plasma’s fluctuating<br />
fields (including wave fields) can<br />
“scatter” the charged particles in<br />
a manner similar <strong>to</strong> collisions in a<br />
neutral gas and cause a mixing of<br />
all the magne<strong>to</strong>spheric components.<br />
A SPHERE OF INFLUENCE 67