Ion transport and loss in the Earth's quiet ring current: 2. Diffusion and magnetosphere‐ionosphere coupling

We have studied the transport and loss of H + , He + , and He ++ ions in the Earth's quiet time ring current (1‐300 keV/ e , 3‐7 R E , Kp <2+, | Dst |<11, 70°‐110° pitchangles, all LT) comparing the standard radial diffusion model developed for the higher‐energy radiation belt particles with measurements of the lower energy ring current ions in a previous paper (Sheldon and Hamilton, 1993). Large deviations of that model, which fit only 50% of the data to within a factor of 10, suggested that another transport mechanism is operating in the ring current. Here we derive a modified diffusion coefficient corrected for electric field effects on ring current energy ions that fit nearly 80% of the data to within a factor of 2. Thus we infer that electric field fluctuations from the low‐latitude to midlatitude ionosphere (ionospheric dynamo) dominate the ring current transport, rather than high‐latitude or solar wind fluctuations. Much of the remaining deviation may arise from convective electric field transport of the E <30 keV particles. Since convection effects cannot be correctly treated with this azimuthally symmetric model, we defer treatment of the lowest‐energy ions to a another paper. We give χ 2 contours for the best fit, showing the dependence of the fit upon the internal/external spectral power of the predicted electric and magnetic field fluctuations.