Kristina A. Lynch

The Kinetic-scale Energy and momentum Transport eXperiment (KiNET-X) sounding rocket explored the coupling of injected barium ions (Ba+) to the ambient ionospheric plasma at two altitudes by releasing two canisters of barium neutrals, each forming an ionized cloud. KiNET-X had instruments on the main payload and on two small deployed subpayloads (Bobs) to measure the Ba+ density (nBa+). The main payload observed nBa+ at a nearly fixed pitch angle to the local geomagnetic field (B→), whereas the Bobs scanned a range of pitch angles. A simple model based on tracing each cloud's particles agreed with the main payload's observed nBa+ profile from the first release; however, for the second release, non-ideal “skidding” motion was required to capture features of the observed nBa+ profile. This paper is a companion to Moses et al. [Phys. Plasmas 32, 042109 (2025)] that analyzes the Bobs' nBa+ profiles. Comparison between the Bobs' measured and modeled nBa+ profiles indicate that pitch angle scattering occurred in each release. Non-idealized pitch angle distributions may arise in the Ba+ clouds from the presence of electric fields parallel to B→ or wave–particle pitch angle diffusion. Pitch angle scattering processes can be proxied in our model by increasing the field-of-view for the density calculation. These different model configurations capture different portions of the measured subpayloads' density and pitch angle profiles. There is perhaps a combination of skidding and scattering that is not easily represented in our model.

Discrete auroral arc systems, despite many symmetries, are three‐dimensional in nature, encapsulating latitude and longitude variations in precipitation and field‐aligned currents combined with important altitude variations in conductivities, hence closure currents. This study presents data‐driven, 3‐D numerical simulations of these processes based on a coordinated campaign of heterogeneous measurements collected from the Poker Flat Research Range during a sequence of Swarm spacecraft overpasses. These measurements include field‐aligned current, global‐scale convection flow, and auroral emissions, which are used to create top‐boundary drivers for auroral arc simulations. Six conjunctions between the spacecraft, all‐sky imagers, and radars are investigated and their measurements are used to simulate auroral arcs through multiple iterations per conjunction event. We look at different estimates of the background convection flow, assumptions about the energy distributions of electron precipitation, and along‐arc structures in field‐aligned current, and see what effect they have on current closure and Joule heating in auroral arc systems. Across the six conjunction events, 11 comparisons of auroral arc systems are presented, covering a catalog of 17 simulations in total. These comparisons allow us to look at the sensitivity of auroral arc systems to input parameters and envelop the simulations in a qualitative confidence interval. Our results suggest that discrete aurorae should be studied in three dimensions to fully understand field‐aligned current closure and, by extension, Magnetosphere‐Ionosphere‐Thermosphere coupling. Additionally, our results demonstrate that both large‐scale convection flows and specifics about the energy distributions of auroral precipitation can significantly affect current closure and Joule heating in auroral arc systems.

The Kinetic-Scale Energy and Momentum Transport Experiment was an ionospheric barium release active plasma experiment designed to investigate the non-ideal momentum coupling between the injected ion cloud and the ambient plasma. It is the first of its kind to feature high-resolution ground-based observations along with multi-point, multi-instrument in situ measurements. We describe a portion of the experimental data and make use of global hybrid and test particle simulations to contextualize and analyze the data. In particular, we seek to measure and understand the non-ideal momentum coupling between an injected ion cloud and the ambient plasma. We find that the simulations and the experiment are in general agreement, and we find substantial evidence of non-ideal physical processes in the in situ data. However, in the optical data, we are not able to distinguish non-ideal momentum coupling from other processes that may delay or slow ionization.

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.

Active plasma experiments can be used to strongly perturb the space plasma environment. During the early phase of a chemical release (e.g., few to several seconds), the injected plasma cloud can excite a variety of waves rather than acting as “inert” tracer particles. It is during this early phase of the release that fundamental plasma processes can be studied. For example, the Trigger [Holmgren et al., J. Geophys. Res. 85, 5043 (1980)] and recent KINetic-scale Energy and momentum Transport eXperiment (KiNET-X) missions were both designed to study processes related to auroral electron energization. Early experiments relied primarily on ground-based optics to diagnose the plasma interaction. Advances in optical sensors have dramatically improved imaging capability of both the ion and neutral components of the injected cloud; therefore, optics remain an important part of these types of experiments. However, advances in plasma (fields and particles) instruments have enabled a new generation of possible experiments from the sounding rocket platform. In this article, we discuss previous sounding rocket (and orbital) active experiments, the related science objectives, and an overview of select results from the KiNET-X rocket mission. Specifically, KiNET-X produced an Alfvénic perturbation, a variety of high frequency waves, energized thermal electrons, and produced a field-aligned electron beam of ∼ 200 eV. The electron energization indicates non-ideal coupling of the injected barium cloud with the ambient ionospheric plasma.

Data products relating to auroral arc systems are often sparse and distributed while ionospheric simulations generally require spatially continuous maps as boundary conditions at the topside ionosphere. Fortunately, all‐sky auroral imagery can provide information to fill in the gaps. This paper describes three methods for creating electrostatic plasma convection maps from multi‐spectral imagery combined with plasma flow data tracks from heterogeneous sources. These methods are tailored to discrete arc structures with coherent morphologies. The first method, “reconstruction,” builds the electric potential map (from which the flow field is derived) out of numerous arc‐like ridges that are then optimized against the plasma flow data. This method is designed for data from localized swarms of spacecraft distributed in both latitude and longitude. The second method, “replication,” uses a 1D across‐arc flow data track and replicates these data along a determined primary and secondary arc boundary while simultaneously scaling and rotating to keep the flow direction parallel to the arc and the flow shear localized at the arc boundaries. The third, “weighted replication,” performs a replication on two data tracks and calculates a weighted average between them, where the weighting is based on data track proximity. This paper shows the use of these boundary conditions in driving and assessing 3D auroral ionospheric, multi‐fluid simulations.

We made observations of magnetic field variations in association with pulsating auroras with the magneto‐impedance sensor magnetometer (MIM) carried by the Loss through Auroral Microburst Pulsations (LAMP) sounding rocket that was launched at 11:27:30 UT on 5 March 2022 from Poker Flat Research Range, Alaska. At an altitude of 200–250 km, MIM detected clear enhancements of the magnetic field by 15–25 nT in both the northward and westward components. From simultaneous observations with the ground all‐sky camera, we found that the footprint of LAMP at the 100 km altitude was located near the center of a pulsating auroral patch. The auroral patch had a dimension of ∼90 km in latitude and ∼25 km in longitude, and its major axis was inclined toward northwest. These observations were compared with results of a simple model calculation, in which local electron precipitation into the thin‐layer ionosphere causes an elliptical auroral patch. The conductivity within the patch is enhanced in the background electric field and as a result, the magnetic field variations are induced around the auroral patch. The model calculation results can explain the MIM observations if the electric field points toward southeast and one of the model parameters is adjusted. We conclude that the pulsating auroral patch in this event was associated with a one‐pair field‐aligned current that consists of downward (upward) currents at the poleward (equatorward) edge of the patch. This current structure is maintained even if the auroral patch is latitudinally elongated.

We have identified for the first time an energy‐time dispersion of precipitating electron flux in a pulsating aurora patch, ranging from 6.7 to 580 keV, through simultaneous in‐situ observations of sub‐relativistic electrons of microburst precipitations and lower‐energy electrons using the Loss through Auroral Microburst Pulsation sounding rocket launched from the Poker Flat Research Range in Alaska. Our observations reveal that precipitating electrons with energies of 180–320 keV were observed first, followed by 250–580 keV electrons 0–30 ms later, and finally, after 500–1,000 ms, 6.7–14.6 keV electrons were observed. The identified energy‐time dispersion is consistent with the theoretical estimation that the relativistic electron microbursts are a high‐energy tail of pulsating aurora electrons, which are caused by chorus waves propagating along the field line.

Whitepaper #351 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: planetary ionospheres / upper atmospheres; space-based missions/projects.

Whitepaper #052 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research; infrastructure/workforce/other programmatic. Additional topics: other basic research; space-based missions/projects; research tools and infrastructure.