An Etymological Dictionary of Astronomy and Astrophysics
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Any of short-lived (generally lasting less than 24 hours) radial features that periodically appear over the outer half of → Saturn's → B ring, when the ring tilt angle is small. These features revolve at the same rate as the planet's → magnetic field and maintain their shape over much of the course of their existence even though they extend tens of thousands of kilometers across the rings. It is believed that the tiny particles that make up these spokes are electrically charged and temporarily "frozen" into the planet's magnetic field (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ radial; → spoke.

In Saturn's rings, changing structures in the radial direction. It is thought that gravitational forces alone cannot account for the spoke structure, and it has been proposed that electrostatic repulsion between ring particles may play a role.

M.E.; O.E. spaca "spoke," related to spicing "large nail," from P.Gmc. *spaikon (cf. O.S. speca, O.Fris. spake, Du. spaak, O.H.G. speicha, Ger. speiche "spoke").

Parré "a rod that extends from the hub of a wheel to support or brace the rim."