Lisa Marie Blush

Escape of O+ through the distant tail plasma sheet

[1] In February 2007, the STEREO-B spacecraft encountered the magnetosheath, plasma sheet and plasma sheet boundary layer from about 200 R E to 300 R E downtail. This time period was during solar minimum, and there was no storm activity during this month. Using data from the PLASTIC instrument, we find that even during quiet times, O + is a constant feature of the deep magnetotail, with an O + density of about 15% of the O + density in the near-earth plasma sheet for similar conditions. The tailward flux of the O + is similar to the flux of O + beams that have been observed in the lobe/mantle region of the deep tail. The total outflow rate of the O + down the plasma sheet is 1.1 × 10 24 ions/s, which is 10% of the total outflow rate of 1 × 10 25 ions/s, and of the same order as the estimated loss from dayside transport.

Kinetic temperatures of iron ions in the solar wind observed with STEREO/PLASTIC

STEREO/PLASTIC provides detailed information on the three‐dimensional velocity distributions of solar wind iron ions with a time resolution of 5 minutes. In general the distributions at 1 AU contain complicated structures showing persistence over several records, i.e., over intervals of up to 30 minutes, but no clear correlation of the properties of these distributions with the direction of the ambient magnetic field is evident. We have performed a statistical analysis using nearly 9000 observations. Iron ions follow the same trends as protons, alpha particles, and electrons: The ratio T⊥/T‖ seems to be limited by the ion cyclotron instability, whereas T‖/T⊥ is bounded by the firehose instability.