Single-point <i>in situ</i> measurements of thermal ions during the KiNET-X ionospheric sounding rocket mission

The KINetic-scale Energy and momentum Transport eXperiment (KiNET-X) sounding rocket mission investigated energy and momentum transport in the ionosphere caused by the known input of two barium releases. Here we investigate (1) the coupling of the injected barium ion (Ba+) cloud to the ambient ionospheric plasma and (2) associated wave-particle interactions. This study uses the main payload platform's measurements of ambient ionospheric thermal ions (O+) and injected Ba+. The observations show ambient O+ heating following each release, coinciding with observed lower-hybrid waves and ion cyclotron oscillations. Comparisons to theoretical expectations reveal that ion cyclotron oscillations were the primary heating mechanism for both releases. The observed Ba+ density (nBa+) showed a differently shaped nBa+ profile for the two releases, and, for event 2, a precursor spike in nBa+. We developed an idealized model of each release cloud's Ba+ particles' trajectories under the Lorentz force to estimate nBa+ in the main payload's region. Comparison of our modeled nBa+ to that observed shows release 1's Ba+ was almost immediately trapped in gyro-motion about the geomagnetic field. However, release 2's model results indicated additional processes may have played a role in the observed Ba+ profile. Thus, we perform a sensitivity study of the impact of skidding and delayed ionization on the modeled output. As release 2 yielded about three times the barium of release 1, release 2's Ba+ mass growth rate was much larger than the rate of ambient Alfvénic plasma coupling to the injected Ba+ plasma, resulting in some features that can be attributed to skidding.