Ring current impoundment of the Io plasma torus Journal Article uri icon



  • A newly discovered feature in the Io plasma formation that may be described as a ramp separating a high‐density plasma ledge on its Jupiterward side from the lower‐density radially distended Io plasma disc on its anti‐Jupiterward side is observed to coincide with a marked inward decrease in the ring current population. The spatial congruency of the counter‐directed maximal gradients in both plasma bodies reveals a profound coupling between them. The existence of the ramp requires a local order‐of‐magnitude reduction in the diffusion coefficient that governs radial mass transport. We demonstrate that the diminished diffusive efficiency there is caused by strong pressure gradient inhibition of the interchange instability that underlies mass transport. The Io plasma torus, which is defined as the region of strong ultraviolet emissions, is identified as the plasma ledge. The plasma density in the ledge is high and, incidentally therefore, able to emit strongly because it is impounded against rapid, centrifugal expulsion by the inwardly directed pressure of the ring current at its inner edge.

publication date

  • September 30, 1981

has restriction

  • closed

Date in CU Experts

  • February 7, 2014 3:07 AM

Full Author List

  • Siscoe GL; Eviatar A; Thorne RM; Richardson JD; Bagenal F; Sullivan JD

author count

  • 6

Other Profiles

International Standard Serial Number (ISSN)

  • 0148-0227

Additional Document Info

start page

  • 8480

end page

  • 8484


  • 86


  • A10