TY  - JOUR
JF  - Geophysical Research Letters
AV  - public
UR  - http://dx.doi.org/10.1029/2006GL028146
N1  - Copyright 2006 by the American Geophysical Union
KW  - X-ray-emission
KW  -  B-ring
KW  -  Runaway Electrons
KW  -  Sprites
KW  -  System
KW  -  Discharge
KW  -  Plasma
N2  - Spokes are near-linear markings sometimes visible on Saturn's rings. They are widely accepted as being electrostatically-levitated sheets of similar to 0.6 micron-radius charged grains. Previously-suggested causes of the grains' charging do not agree with all spoke characteristics, which include their rapid generation, localized formation primarily in Saturn's midnight-dawn sector, the seasonality of their apparitions, and, crucially, their morphologies. We contend that spokes are caused by lightning-induced electron beams striking the rings, at locations magnetically-connected to thunderstorms. This view is supported by a semi-quantitative spoke morphology simulation. Spokes' formation locations are further controlled by Saturn's ionospheric density, which reaches a near-dawn minimum where electron beams can most easily propagate to the rings. The beams may generate observed X-ray emission, supply particles to Saturn's radiation belts, and over time will modify the rings' constituents. Finally, we report Cassini MIMI instrument observations of an electron burst which displays some characteristics expected of a lightning-induced event.
PB  - AMER GEOPHYSICAL UNION
SN  - 0094-8276
Y1  - 2006/11/09/
IS  - 21
ID  - discovery9651
TI  - Formation of Saturn's ring spokes by lightning-induced electron beams
A1  - Jones, GH
A1  - Krupp, N
A1  - Kruger, H
A1  - Roussos, E
A1  - Ip, WH
A1  - Mitchell, DG
A1  - Krimigis, SM
A1  - Woch, J
A1  - Lagg, A
A1  - Franz, M
A1  - Dougherty, MK
A1  - Arridge, CS
A1  - McAndrews, HJ
VL  - 33
ER  -