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The ability to morph electrostatic plasma turbulence into electromagnetic has promising applications, including the possibility of actively influencing the near‐Earth plasma state, aka the space weather. This dual (electrostatic/electromagnetic) nature is a fundamental property of plasma turbulence, which has not been well explored but could explain many phenomena including the formation of a resonant cavity that can amplify the turbulence energy. The upcoming Space Measurement of A Rocket‐Released Turbulence (SMART) mission is designed to understand the evolution of plasma turbulence and the nonlocal consequences of its dual nature. This includes the flow of energy into all possible wavelengths, as well as the transport of energy over a large geographical volume. The resulting energy redistribution in both waves and particles in an extended geographical volume creates a unique electromagnetic environment, which is important for space weather. SMART is an active experiment to study the evolution of turbulence in the natural plasma environmentFast neutral barium beam injection in ionosphere will produce lower hybrid waves to pump turbulenceNonlinear conversion of lower hybrid to whistler waves and escape to radiation belts to be monitored

The stability of a quasi‐static near‐Earth dipolarization front (DF) is investigated with a two‐dimensional electromagnetic particle‐in‐cell model. Strongly localized ambipolar electric fields self‐consistently generate a highly sheared dawnward E→×B→electron drift on the kinetic scale in the DF. Electromagnetic particle‐in‐cell simulations based on the observed DF thickness and gradients of plasma/magnetic field parameters reveal that the DF is susceptible to the kinetic electron‐ion hybrid (EIH) instability driven by the strong velocity inhomogeneity. The excited waves show a broadband spectrum in the lower hybrid (LH) frequency range, which has been often observed at DFs. The wavelength is comparable to the shear scale length, and the growth rate is also in the LH frequency range, which are consistent with the EIH theory. As a result of the LH wave emissions, the velocity shear is relaxed, and the DF is broadened. When the plasma beta increases, the wave mode shifts to longer wavelengths with reduced growth rates and enhanced magnetic fluctuations although the wave power is mostly in the electrostatic regime. This study highlights the role of velocity inhomogeneity in the dynamics of DF which has been long neglected. The EIH instability is suggested to be an important mechanism for the wave emissions and steady‐state structure at the DF. Magnetotail DF contains a substantial velocity shear in the tangential electron driftThe sheared flow is susceptible to the EIH instability and can broaden the DF by emitting broadband LH wavesThe EIH emissions become more electromagnetic as plasma beta increases

Dipolarization fronts are typically observed with a density gradient of scale size comparable to an ion gyroradius, which naturally results in an ambipolar electric field in the direction of the gradient. Prevailing models ignore this ambipolar electric field, the separation of ion and electron scale physics, and consequent non‐Maxwellian plasma distributions with strong spatial gradients in velocity, all of which we investigate in this paper. We examine two dipolarization front events observed by the Magnetospheric Multiscale mission (one with low plasma beta, one with high plasma beta), develop a rigorous kinetic equilibrium for dipolarization fronts, analyze the linear stability, and explore the nonlinear evolution and observable signatures with kinetic simulations. There are two major drivers of instability in the lower‐hybrid frequency range: the density gradient (lower‐hybrid drift instability) and the velocity shear (electron‐ion hybrid instability). We argue the electron‐ion hybrid mode is dominant, and consequently a dipolarization front approaches a steady or saturated state through the emission of waves that relax the velocity shear. A key aspect of these shear‐driven waves is a broadband frequency spectrum that is consistent with satellite observation. An ambipolar electric field arises due to global compression when the scale is comparable to the ion gyroradiusThis electric field leads to velocity shear that provides energy for broadband emissionsThe velocity shear‐driven electron‐ion hybrid instability primarily balances the compression

We develop a Bayesian spectral analysis technique that calculates the probability distribution functions of a superposition of wave modes each described by a linear growth rate, a frequency, and a chirp rate. The Bayesian framework has a number of advantages, including (1) reducing the parameter space by integrating over the amplitude and phase of the wave, (2) incorporating the data from each channel to determine the model parameters such as frequency which leads to high‐resolution results in frequency and time, (3) the ability to consider the superposition of waves where the wave parameters are closely spaced, (4) the ability to directly calculate the expectation value of wave parameters without resorting to ensemble averages, and (5) the ability to calculate error bars on model parameters. We examine one rising‐tone chorus element in detail from a disturbed time on 14 November 2012 using burst mode waveform data of the three components of the electric and magnetic field from the EMFISIS instrument on board NASA's Van Allen Probes. The results demonstrate that subelements are likely composed of almost linear waves that are nearly parallel propagating with continuously changing wave parameters such as frequency and wave vector. Between subelements the wave parameters of the dominant mode undergoes a discrete change in frequency and wave vector. Near the boundary of subelements multiple waves are observed such that the evolution of the waves is reminiscent of wave‐wave processes such as parametric decay or nonlinear induced scattering by particles. These nonlinear processes may affect the saturation of the whistler mode chorus instability. A Bayesian spectral technique for multichannel waveform data is developed and applied to chorus wavesChorus subelements are shown to be composed of mostly linear cold plasma wavesBetween chorus subelements, the frequency exhibits a discrete change

Releasing diffuse artificial clouds into the space environment using a rocket or spacecraft can modify the natural plasma state. This uses space itself as a laboratory for studying plasma phenomena that cannot be reproduced on the ground. The Space Measurement of A Rocket‐released Turbulence (SMART) mission will inject a beam of barium neutral vapor into the ionosphere and perpendicular to the Earth's magnetic field. Barium atoms will be photoionized, forming an ion ring distribution that is unstable to lower hybrid waves. Large amplitude lower hybrid waves nonlinearly scatter to whistler and magnetosonic waves that can propagate out to the magnetosphere. This paper details the theory, modeling, and simulation we used to design this release experiment to optimize the energy in the plasma waves under a variety of constraints. A product of this analysis is quantitative predictions for some in situ and remote measurements. Hydrocode simulations of barium vapourization and acceleration via shaped charge provide the initial state of the neutral beam. We optimize the apogee, orientation, and position of the payload and instruments. Cloud dynamics are simulated with a direct simulation Monte Carlo technique, which includes photoionization with metastable barium states, collisions with the neutral background atmosphere, optical line emission, gravity, and electromagnetic forces. We predict the plasma density measured by the instrument payload and the remotely measured optical intensity. We also examine how the plasma wave growth differs at the measurement location compared to the bulk of the barium cloud. A variety of models and simulations are combined to optimize plasma wave energy in a neutral beam injection experimentModeling provides quantitative predictions of measurements (e.g., plasma density, beam velocity, total barium produced, optical intensity)We discuss the many details that arose between concept and implementation of the experiment, and how these affected mission design A variety of models and simulations are combined to optimize plasma wave energy in a neutral beam injection experiment Modeling provides quantitative predictions of measurements (e.g., plasma density, beam velocity, total barium produced, optical intensity) We discuss the many details that arose between concept and implementation of the experiment, and how these affected mission design

The Space Measurement of A Rocket‐released Turbulence mission will demonstrate the production and evolution of turbulence in the space environment via a cascade of plasma physics processes. A sounding rocket will inject neutral barium atoms into the upper ionosphere at high speed across the magnetic field. The barium atoms photoionize, and the magnetic field confines them, leading to an ion ring distribution in velocity space that is unstable to electrostatic lower hybrid waves. Nonlinear induced scattering of lower hybrid waves produces electromagnetic magnetosonic and whistler waves that rapidly escape the source region and propagate into the radiation belts. In this paper, we present models and simulations of early time parts of this cascade until the lower hybrid waves are generated. We study the neutral atom injection, expansion, and ionization analytically and computationally. In a realistic scenario, the velocity distribution function is found to be nongyrotropic instead of a perfect ring in the plane perpendicular to the magnetic field. Using these results, we examine a representative region of the barium cloud and perform particle‐in‐cell simulations of the excitation of the lower hybrid waves. Of particular interest is the energy extracted from the kinetic energy of the barium ions, as this will ultimately affect the amplitude of the electromagnetic waves in the radiation belts. We find that for velocity distribution functions that deviate from an ideal ring distribution, the energy extracted from the fast barium ions increases. SMART experiment will produce turbulence and study evolution on macroscopic scale in natural plasmaNeutral beam injection produces nongyrotropic and anisotropic helical ion distribution functionsWave energy extracted from these unstable ion population increases with nongyrotropy