A Circuit Model for the Interaction of an RF Impedance Probe with Ionospheric Plasmas in the E-Layer and F-Layer Ionosphere Regions

We analyze Sweeping Impedance Probe (SIP) measurements which were made by the payload of the STORMS sounding rocket, launched from Wallops Island, Virginia, in 2007. The objective of the STORMS mission was to establish whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. Using a fluid formulation for the impedance of the plasma, we modify the interaction by introducing a sheath capacitance and additional conductivity elements in order to fit circuit models against the data obtained at different altitudes. From these measurements, we will be able to infer both the absolute electron density and the electron neutral collision frequencies throughout the flight trajectory. The models have to be altered as the payload moves through different ionospheric layers because the sheath capacitance and parallel conductivities become prominent depending on the local properties of the ionosphere around the probe structure. Our model is found to robustly and consistently fit to the data, accounting for all the observations over both the upleg and downleg of the payload trajectory.