Sheath capacitance observed by impedance probes onboard sounding rockets: Its application to ionospheric plasma diagnostics

Ion sheath which is formed around an electrode significantly affects the impedance of the probe immersed in a plasma. The sheath capacitances obtained from impedance probe measurements were examined for application to plasma diagnoses. We compared analytical calculations of the sheath capacitance with measurements from impedance probes onboard ionospheric sounding rockets. The S-520-23 sounding rocket experiment, which was carried out in mid-latitude, demonstrated that the observed sheath capacitances agreed well with those of the calculations. We concluded that the sheath capacitance measurements allow for estimation of the electron temperature and the electron density of a Maxwellian plasma. On the other hand, the sheath capacitances obtained from the S-310-35 rocket experiment in the auroral ionosphere showed lower values than expected. Auroral particles precipitations should modify the probe potential.