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We present Magnetospheric Multiscale observations showing large numbers of slow electron holes with speeds clustered near the local minimum of double-humped velocity distribution functions of background ions. Theoretical computations show that slow electron holes can avoid the acceleration that otherwise prevents their remaining slow only under these same circumstances. Although the origin of the slow electron holes is still elusive, the agreement between observation and theory about the conditions for their existence is remarkable.

Slow electron holes, that are electrostatic solitary waves propagating with velocities comparable to the ion thermal velocity, can contribute to plasma heating and provide an anomalous resistivity in various space plasma systems. In addition, the analysis of electron holes allows revealing instabilities operating on time scales not resolved by plasma instruments. We present experimental analysis of more than 100 slow electron holes in the Earth’s bow shock and more than 1000 slow electron holes in the Earth’s nightside magnetosphere. We show that in both regions, the electron holes have similar parameters. The spatial scales are in the range from 1 to 10 Debye lengths, amplitudes of the electrostatic potential are typically below 0.1 of local electron temperature, velocities in the plasma rest frame are of the order of local ion-acoustic velocity. We show that in both regions the electron holes are most likely produced by Buneman-type instabilities. We develop theoretical models of the electron holes and compare them to MMS observations. The lifetime and the transverse instability of the electron holes are discussed.This work was supported by the Russian Scientific Foundation, Project No. 19–12-00313

Here we briefly review possible indirect effects of dark matter (DM) of the Universe. It includes effects in cosmic rays (CR): first of all, the positron excess at $\sim$ 500 GeV and possible electron-positron excess at 1-1.5 TeV. We tell that the main and least model-dependent constraint on such possible interpretation of CR effects goes from gamma-ray background. Even ordinary $e^+e^-$ mode of DM decay or annihilation produces prompt photons (FSR) so much that leads to contradiction with data on cosmic gamma-rays. We present our attempts to possibly avoid gamma-ray constraint. They concern peculiarities of both space distribution of DM and their physics. The latter involves complications of decay/annihilation modes of DM, modifications of Lagrangian of DM-ordinary matter interaction, and inclusion of mode with identical fermions in final state. In this way, no possibilities to suppress were found except, possibly, mode with identical fermions. While the case of spatial distribution variation allows achieving consistency between different data. Also we consider stable form of dark matter which can interact with baryons. We show which constraint such DM candidate can get from damping effect in plasma during large scale structure formation in comparison with other existing constraints., 20 pages, 14 figures

The direct measurements of the cosmic electron-positron spectrum around 1 TeV made by DAMPE have induced many theoretical speculations about possible excesses in the data above the standard astrophysical predictions that might have the dark matter (DM) origin. These attempts mainly fall into two categories: i) DM annihilation (or decay) in the Galactic halo producing the broad spectrum excess; ii) DM annihilation in the nearby compact subhalo producing the sharp peak at 1.4 TeV. We investigate the gamma-ray emission accompanying $e^+e^-$ production in DM annihilation, as well as various theoretical means to suppress the prompt radiation, such as specific interaction vertices or multi-cascade modes, and conclude that these attempts are in tension with various gamma-ray observations. We show that the DM explanations of the broad spectrum excess tend to contradict the diffuse isotropic gamma-ray background (IGRB), measured by Fermi-LAT, while the nearby subhalo scenario is constrained by nonobservation in the surveys, performed by Fermi-LAT, MAGIC and HESS. We also briefly review other types of gamma-ray constraints, which seem to rule out the DM interpretations of the DAMPE broad spectrum excess as well., Comment: 25 pages, 8 figures

We report a design solution for a highly reliable, low-noise and extremely efficient cryogenically cooled transmit/receive unit for a large antenna system meant for radio-astronomical observations and deep-space communications in the X band. We describe our design solution and the results of a series of laboratory and antenna tests carried out in order to investigate the properties of the cryogenically cooled low-noise amplifier developed. The transmit/receive unit designed for deep-space communications (Mars missions, radio observatories located at Lagrangian point L2, etc.) was used in practice for communication with live satellites including “Radioastron” observatory, which moves in a highly elliptical orbit.

The CP conserving Zγγ and ZZγ couplings in the SM and MSSM models at loop level were investigated. For the both models, the coupling parameters h 3 Z , h 3 γ , f 5 γ were estimated for the energy ranges, accessible at the LHC. Extension of the considered energy range up to 14 TeV leads to a possibility to constrain theories by using experimental limits on anomalous couplings from the LHC experiments. It was found that in order to constrain the parameters of the MSSM model, a measurement accuracy of the order of 10−7 is required.

Current sheets with strong transverse (cross field) currents are commonly observed in planetary magnetospheres and serve as a natural energy source for magnetic reconnection. As the most investigated current sheet, the current sheet in the Earth's magnetotail forms in a high-β plasma, with hot ions dominantly contributing to the diamagnetic currents. Spacecraft observations have shown, however, that a superthin electron dominated current sheet can be embedded in the Earth's magnetotail current sheet. In this paper, we develop a model of such superthin current sheets with strong currents produced by anisotropic electrons. We also compare the model with spacecraft observations, which shows reasonable agreement in spatial profiles and magnitudes of the current density. The spatial scale (thickness) of the superthin current sheet is controlled by the equatorial magnetic field component, whereas the current density magnitude is controlled by the electron fire-hose parameter at the equator. Although the current density peak within the superthin current sheet can significantly exceed the background (embedding) current density, the magnetic field magnitude at the superthin current sheet boundary does not exceed 10% of the total magnetic field magnitude. These superthin current sheets are sub-ion (or even electron-scale) structures, which are not sufficiently large/intense to perturb ion dynamics. We discuss applications of the proposed model for the analysis of plasma instabilities in superthin electron-dominated current sheets.

In this proceedings we study possibility of final state radiation (FSR) in the process of dark matter (DM) decay/annihilation. Two possibilities are considered independently: one-cascade annihilation through intermediate particle (a), and parameterized interaction vertex. The mass of a and vertex parameters are used to try to suppression FSR. Suppression is necessary to avoid limit from cosmic gamma-radiation preventing DM explanation of positron anomaly in CR. Finally, it may seem that a little suppression can be reached by fine-tuning the mass of a, and vertex parameters do not help to do it in the considered cases.

A method is proposed for mathematically modeling the hydrodynamic and electromagnetic processes that take place in different electromagnetic velocity meters designed for use on liquids.