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Understanding electron kinetic processes is crucial for elucidating the energy conversion mechanisms in magnetic reconnection. Non‐Maxwellian electron distributions are strong indicators of kinetic‐scale processes near the electron diffusion region, yet they remain incompletely understood. Using in‐situ spacecraft data from 29 magnetopause reconnection events, we unambiguously identify a non‐Maxwellian capsule electron distribution near the electron diffusion region. This distribution comprises an elongated component parallel with the magnetic field at lower energies and a butterfly component (with peaks at pitch angles near 45°$45{}^{\\circ}$and 135°$135{}^{\\circ}$ ) at higher energies. We provide evidence that these distributions are partly linked to electron trapping and preferential heating along the direction of magnetic fields. The parallel electric potentials needed for the parallel heating may be linked to kinetic Alfvén waves. These capsule‐like electron distributions are also found to generate whistler emissions. Our results suggest that these kinetic processes are prevalent in magnetic reconnection. Plain Language Summary Understanding how electrons behave in space plasmas, especially during magnetic reconnection, is crucial. Using data from spacecraft, we studied electron behavior near this reconnection region and identified a unique pattern called a capsule distribution. This distribution combines two shapes: an elongated component at lower energies and a butterfly like component at higher energies. These distributions are closely linked to whistler wave emissions. Our research provides evidence that these capsule‐like distributions indicate electron trapping and heating by parallel electric fields. The parallel electric field and electric potentials may be related to kinetic Alfven waves. These kinetic processes, captured by emitted whistler waves, are prevalent near the diffusion region, offering deeper insights into electron heating during magnetic reconnection. Key Points Non‐Maxwellian capsule electron distributions near the electron diffusion region comprises an elongated component and a butterfly component Capsule‐like electron distributions generate whistler emissions in the presence of unusual temperature anisotropy T‖/T⊥<1$\\left({T}_{\\Vert }/{T}_{\\perp }< 1\\right)$Capsule electron distributions suggest electron trapping and preferential heating by parallel electric fields

In this paper, we have investigated linear and nonlinear propagation of kinetic Alfven waves in which the electrons have been assumed to follow generalized (r,q\\(r,q\\)) distribution. We have shown that (r,q\\(r,q\\)) distribution gives us most of the distributions observed in space plasmas. We have varied the flatness parameter r\\(r\\) and the tail parameter q\\(q\\) to explore the linear and nonlinear propagation characteristics of kinetic Alfven waves. We have also discussed the limiting cases. It has been shown that our results agree well with Fast and Freja observations of the nonlinear kinetic Alfven waves. An important feature of our study is the formation of rarefactive solitary structures. It has been shown that this result cannot be obtained with Maxwellian distribution and that it agrees well with the observations of Fast and Freja satellites.

In 1979, after plasma envelope exploration, Voyager 1 and 2 revealed that Jovian magnetosphere consists of an unusual mixture of ions like hydrogen, sulphur, oxygen etc., in similar proportions. The present study observed that the waves in Jovian magnetosphere propagate in whistler-mode, with some similarities to whistler-mode auroral hiss in the Earth’s magnetosphere. The dispersion relation has been deduced and calculated in detail for oblique propagating waves in presence of parallel AC electric field for bi-Maxwellian distribution function. Magnetic field model for different values of latitude at radial distance 17RJ\\(17 R_J\\) has been reported. By using the method of characteristic solution, relativistic growth rate has been calculated. Data provided by spacecrafts like Pioneer 10 and 11, Voyager 1 and 2, while exploring the magnetosphere of Jupiter, has been used to plot graphs of variation of growth rate for different values of various plasma parameters like temperature anisotropy, angle of wave propagation, AC frequency etc. The effect on growth rate by these plasma parameters is shown by graphs.

In space plasmas, particle distributions are often observed having high energy tails and are well fitted by kappa distribution function. However, in auroral region electrons are expected to be accelerated mainly along the magnetic field lines and one may expect Maxwellian behaviour in perpendicular direction. Therefore, in the present study propagation characteristics of electromagnetic electron cyclotron (EMEC) waves is studied by employing kappa-Maxwellian distribution function for energetic trapped electrons in auroral region. Real frequency and the growth rate expressions have been solved numerically for kappa-Maxwellian plasma and then analyzed by considering the effect of different plasma parameters for wide range of auroral altitudes. The numerical results obtained show that growth rate increases with the increase in ratio ωpe/Ωe, plasma beta, temperature anisotropy T⊥/T∥ and trapped electron drift speed but decreases when superthermal electron population increases.

Neutron stars (NSs) are thought to receive natal kicks at their formation in supernovae. In order to investigate the magnitude of these kicks, we analyze the proper motions and distance estimates—through either parallax or dispersion measures—of young isolated pulsars and infer their three-dimensional velocities relative to their local standard of rest. We find that the velocities based on parallax distances of pulsars younger than 10 Myr follow a lognormal distribution with μ = 5.60 ± 0.12 and σ = 0.68 ± 0.10, peaking at ∼150–200 km s−1, which we adopt as our fiducial kick distribution. Using a previously established method that infers kick magnitudes through the eccentricity of Galactic trajectories, we also estimate the kick velocities of older pulsars, which we find to be consistent with our fiducial kick distribution. A lognormal fit to all pulsars with ages below 40 Myr yields a more constraining (but possibly more prone to systematic errors) fit with μ = 5.67 ± 0.10 and σ = 0.59 ± 0.08, respectively. Moreover, (1) we resolve the tension between our results and the Maxwellian distribution found by Hobbs et al., which has a ∼50% higher median velocity, by showing that their analysis is missing a Jacobian needed to correct for its logarithmic histogram bin sizes, and (2) we argue that the bimodality found by others is not statistically significant and that previous results are consistent with our inferred kick distribution, effectively reconciling the literature on observed NS kicks.

AbstractFor accurate electron density diagnostics in the solar transition region, the principle of electron density diagnostics are discussed by lines from Si VIII ion for kappa and Maxwellian distributions By observed line ratio of the Si VIII 1440.50 to 1445.75 Å lines in quiet sun and active region, the electron density is discussed for any observed line ratio, and results are consistent with reported values in literature. The relationships between line ratio and electron density for the kappa and Maxwellian distributions are also discussed, in the case of lower and higher electron density limits, and results indicate that different distributions have no effect on relationships between the line ratio and the electron density at lower or higher electron density limit. This discussion is significant for accurate electron density diagnostics in the solar transition region, which will be important for study on coronal heating and acceleration of solar wind.

For accurate spectral diagnostics in the solar transition region, we discuss the electron energies for non-Maxwellian distributions both for and Druyvesteyn distributions. We analyze the difference between the κ and the Druyvesteyn distributions with the Maxwellian distribution and derive the expressions for the averaged collision strengths for the κ and the Druyvesteyn distributions. This discussion will be significant for spectral diagnostics of the electron density and temperature in the solar transition region.

A velocity dependent, kinetic model for line radiation is developed for continuum kinetic codes. It has been implemented in the full-f gyrokinetic code Gkeyll. The total radiation for a charge state is modeled as an advection in velocity space with a form of ∇v⋅(vν(v)f(v)), guaranteeing particle conservation. The velocity dependence (in the form of an effective frequency ν(v)) is found through fitting the energy loss of the operator, i.e. the second velocity moment, to the radiation data in the OpenADAS database. Therefore, each individual transition does not need to be evaluated every time step, significantly reducing the computational cost of including line radiation in a kinetic model. The dependence on velocity instead of the usual, temperature, allows the radiation to be computed from non-Maxwellian electron distribution functions: We benchmark the model against a collisional radiative model using isotropic non-Maxwellian distribution functions. A velocity dependent model of radiation can more accurately describe the radiation in the more kinetic regimes expected in reactor-scale devices. The velocity dependence qualitatively captures the quantum mechanical need for a minimum velocity before any radiation occurs.

The beam transport process plays a crucial role in the design and realization of negative-ion-based neutral beam injection (N-NBI) systems for thermonuclear fusion. In particular, space charge compensation (SCC), where positive ions generated by collisions between negative ions and background gas mitigate space charge effects, serves as a critical mechanism influencing beam divergence and envelope evolution. In this work, the SCC process in N-NBI systems and its impact on beam transport are investigated using a 3D simulation model based on a Vlasov beam-tracing algorithm. Systematic simulations show that SCC evolution and downstream beam optics are jointly controlled by background gas pressure and beam energy, with higher pressure and higher energy strengthening SCC and mitigating divergence and envelope growth downstream of the extraction system. A key physical observation is that collisionless phase mixing drives the transverse velocity distribution of secondary ions toward a Maxwellian distribution, enabling an effective transverse ion temperature that quantitatively correlates with SCC degree. The residual electric field leaking downstream of the extraction system locally weakens SCC over a finite extent, producing negligible beam optics impact for the ITER-relevant 1 MeV case at pressures of 5 × 10 − 3 Pa and 1 × 10 − 2 Pa , but non-negligible transport sensitivity at 200 keV under the same pressure range. These results provide new insight into the interplay between SCC, secondary-ion dynamics, and beam transport, with direct relevance to the modeling and optimization of high-energy NBI beamlines.

In recent years, a handful of “dark” binaries have been discovered with a nonluminous compact object. Astrometry and radial velocity measurements of the bright companion allow us to measure the post-supernova orbital elements of such a binary. In this paper, we develop a statistical formalism to use such measurements to infer the pre-supernova orbital elements, and the natal kick imparted by the supernova (SN). We apply this formalism to the recent discovery of an X-ray quiet binary with a black hole, VFTS 243, in the Large Magellanic Cloud. Assuming an isotropic, Maxwellian distribution on natal kicks and using broad agnostic mass priors, we find that kick velocity can be constrained to V k < 72 km s−1 at 90% confidence. We find that a Blaauw kick cannot be ruled out, and that at least about 0.6M ⊙ was lost during the supernova with 90% confidence. The pre-SN orbital separation is found to be robustly constrained to be around 0.3 au.