Small-Scale Irregularities Within Polarization Jet/SAID During Geomagnetic Activity.

We study the spatial structure of a polarization jet/Sub-Auroral Ion Drift (PJ/SAID) based on data from the NorSat-1 and Swarm satellites during a geomagnetic storm. Observations of plasma parameters inside the PJ/SAID are obtained with NorSat-1 using a system of Langmuir probes with a nominal sampling rate of up to 1 kHz, which allowed measurements with such a high temporal resolution for the first time. A comparative analysis of plasma parameters and electron density spectra inside PJ according to the data from both satellites is presented. Our results show that fluctuations of plasma parameters inside the PJ increase at all scales with increasing geomagnetic activity. Small-scale irregularities in the PJ are measured in situ down to hundreds of meters. The role of large-scale effects in the PJ increases in comparison with the small-scale ones during high geomagnetic activity. The PJ consists of structures ∼0.2° latitude in size within which small-scale irregularities are present.