The solar wind plasma density control of night-time auroral particle precipitation

Abstract. DMSP F6 and F7 spacecraft observations of the average electron and ion energy, and energy fluxes in different night-time precipitation regions for the whole of 1986 were used to examine the precipitation features associated with solar wind density changes. It was found that during magnetic quietness |AL|<100nT), the enhancement of average ion fluxes was observed at least two times, along with the solar wind plasma density increase from 2 to 24cm^–3. More pronounced was the ion flux enhancement that occurred in the b2i–b4s and b4s–b5 regions, which are approximately corresponding to the statistical auroral oval and map to the magnetospheric plasma sheet tailward of the isotropy boundary. The average ion energy decrease of about 2–4kev was registered simultaneously with this ion flux enhancement. The results verify the occurrence of effective penetration of the solar wind plasma into the magnetospheric tail plasma sheet.

Key words. Ionosphere (auroral ionosphere, particle precipitation) – Magnetospheric physics (solar windmagnetosphere interaction)