Fluctuations of Current onto Flat Probes of the ZOND–ZARYAD Instrument Mounted on the MIR Orbital Complex

Flat probes of the ZOND–ZARYAD instrument, which operated on the MIR orbital complex (OC), form a counterprobe (reference surface) configuration in which the alternating component of the net probe current is measured. There is no potential difference between the spacecraft (SC) body and the probes; that is, the probes are at the floating potential (FP). By measuring the alternating component of the probe current, one cannot estimate the FP value, but we can observe small-scale FP dynamics of a single probe in the OC near-surface region and estimate the fluctuations of currents flowing onto the SC. The alternating component of the current on the probes in the OC near-surface region varies in a wide range depending on ionospheric plasma parameters, the probe orientation with respect to the velocity vector, the magnetic field vector, and the direction to the Sun in the illuminated part of the orbit. In addition to the amplitude dynamics, the frequency dynamics of the alternating component of the current onto the probes is observed.     

The analysis of measurements of quasi-stationary electrical fields in the near-surface zone of the <Emphasis Type="Italic">Mir</Emphasis> orbital complex

The quasi-stationary electrical fields have been measured in the near-surface zone of the Kvant module of the Mir orbital complex using vibration-type sensors of the Zond-Zaryad instrument. The analysis of measurements has shown that, depending on the spacecraft’s surface section shape (an octagon), four areas of the electrical fields configuration (and of the plasma component density) were revealed in the spacecraft vicinity: a ram with angular extension of about 120° (±60°), two side areas with angular extension of about 60° each, and a wake with angular extension of about 120° (±60°). The electrical field in the ram has a small absolute value. In the side areas, the electrical field can have either a negative or positive value, and it is smaller in magnitude than that in the ram. The electrical field in the wake has a three-petal structure (and an even more complicated structure is also possible): the negative value of the field (with angular extension of about 45°), the positive value of the field (with angular extension of about 30°), and, again, the negative value of the field (with angular extension of about 45°). Absolute value of the field in the wake is at least an order of magnitude higher than that in the ram and on the side surfaces.