Low-energy plasma in Neptune's magnetosphere



Plasma data from the region of Neptune's magnetosphere between L=6.5 and L= 13.5 are analyzed. Selecting only spectra where both light and heavy ions are present, we derive density and temperature profiles under the assumption that the ions are H+ and N+. These results are used to calculate the total flux shell content (for a shell of unit width in L), N, of each km in this region. Values of N derived from inbound and outbound data are similar, indicating the plasma distribution functions are isotropic. Average values of NL2 are 3×1032 for H+ and 1×1032 for N+. Profiles of NL2 for both H+ and N+ increase outwards, suggesting that Triton is the probable source of both these components. Evidence is presented for significant inbound-outbound asymmetries in the plasma morphology.