Empirically modeling ionospheric electron density variations using F107, E107 and MgII indices based on long-term incoherent scatter radar observations over Millstone Hill

Each of three solar flux indices, F107, E107, and MgII core-to-wing, has been tested as a solar activity proxy to model empirically electron density Ne measurements made by an incoherent scatter radar during the period of 1976-2001 over the height span of 1501000km at Millstone Hill. It is found that deviations of model values given by the three indices to the data are practically the same, regardless of altitude, local time, and season, indicating no significant improvements with introducing the newer indices E107 and MgII for empirically modeling long-term Ne data. The long-term behavior of the three indices are identical. This paper also discusses electron density responses to the solar flux index.