Space Measurements of A Rocket-Released Turbulence (SMART) an Experiment to Study Turbulence

We describe a sounding rocket experiment, Space Measurements of A Rocket-Released Turbulence (SMART) , which will explore the role of the weak turbulence process known as nonlinear (NL) scattering in space plasmas. The experiment will seed electrostatic (ES) lower-hybrid (LH) waves in the ionosphere and make coordinated measurement of the scattered electromagnetic (EM) waves (e.g., whistlers) with both a sounding rocket in the ionosphere and remotely with a satellite in the magnetosphere. The effect of Very Low Frequency whistler turbulence is of particular importance to the dynamics in the inner magnetosphere and the radiation belts, but also has more global relevance, e.g. in solar wind.

The SMART is similar, but not identical to experiments conducted since the mid-1970s which generated high speed Barium (Ba) atoms using shape-charge explosion to accelerate Ba atoms to velocities of 8 - 10 km/s perpendicular to the Earth's magnetic field. In SMART, the Ba atoms photo-ionize forming a partial ring velocity distribution of Ba+ that is unstable and known to generate LH turbulence. Recent analysis indicate that weak turbulence processes, in particular the NL scattering of LH waves into EM whistlers, is critical but has not been characterized in the space environment. This critical feature will be tested in the proposed experiment. Previous Ba explosive releases measured large amplitude electric fields; indicate the generation of EM waves and, in one case, energetic particle precipitation. However, none of these experiments had sufficient measurements to separate the EM contribution to the electric field and confirm NL scattering.

Satellite measurements will detect the SMART-generated waves and their effects in the radiation belts. Possible satellites, for the targeted 2021 launch of SMART, are Arase/ERG, DSX, and Cassiope/ePOP. The SMART mission will lead to a better understanding of NL scattering to convert ES LH waves into EM whistlers, loss processes in the radiation belts, and their connection to weak turbulence. We will present recent modelling predicting LH electric fields, whistler propagation, and optical emissions from Ba and Ba+ expected during the experiment as well as describing the techniques to be used during the SMART mission.

This work was supported by Defense Advanced Research Projects Agency.