We study energetic spectra of H+, He+, and O+ ion fluxes in the energy range ≥130 keV measured by Cluster/Research with Adaptive Particle Imaging Detectors (RAPID) instruments during 37 intervals of ...the tailward bulk flow propagation in the near‐Earth tail (at X ≤ −19 RE). In all events from our database, the plasmoid‐like magnetic structures with the superimposed low‐frequency magnetic and electric field fluctuations were observed along with the tailward bulk flows. The plasmoid‐like structures were associated with the enhancements of energetic ion fluxes and the hardening of energy spectra of H+ and He+ ion components in 80% of events and of O+ ion component in 64% of events. The hardening of energy spectra was more pronounced for heavy ions than for protons. The analysis of the magnetic structures and power spectral density (PSD) of the magnetic and electric field fluctuations from our database revealed the following factors favorable for the ion energization: (1) the spatial scale of a plasmoid should exceed the thermal gyroradius of a given ion component in the neutral plane inside the plasmoid; (2) the PSD of the magnetic fluctuations near the gyrofrequency of a particular ion component should exceed ~ 50.0 nT2/Hz for oxygen ions; while the energization of helium ions and protons takes place for much lower values of the PSD. The kinetic analysis of ion dynamics in the plasmoid‐like magnetic configuration similar to the observed one with the superimposed turbulence confirms the importance of ion resonant interactions with the low‐frequency electromagnetic fluctuations for ion energization inside plasmoids.
Key Points
Spectra of energetic H+, He+, O+ fluxes were studied tailward of X line
Strong ion acceleration occurs in turbulent region inside plasmoids
Ions are accelerated due to resonant interaction with EM fluctuations
Flapping of the current sheet (CS) associated with the propagation of high‐velocity bulk flows allowed to observe the super thin current sheet (STCS) in the magnetotail plasma sheet (PS). During the ...interval of interest, 111 crossings of the CS neutral plane were detected. In 95 crossings, the STCSs with a current density J ≥ 20 nA/m2 were observed. A half‐thickness (LSTCS) of the STCSs was about a few electron gyroradii or less. In a number of the STCSs the parameter of adiabaticity (κe) was <1.0 for suprathermal electron population (>1 keV). Our analysis has shown that the electric current in such STCSs is carried by unmagnetized electrons (κe < 1), and the stress balance is supported by the off‐diagonal terms of their pressure tensor. In this sense, the underlying physics of the formation of STCSs at electron scales by unmagnetized electrons is similar to the mechanism of ion‐scale thin CS formation by the quasi‐adiabatic ions. The low‐energy population of magnetized electrons is also crucially important since it keeps the STCS stable and allows their observation as a quasi‐stationary structure. We compare the observed half‐thickness of the STCS with that predicted by a new kinetic theory (λ) considering the coupling between ion‐scale TCS and electron‐scale STCS. We found a reasonable agreement between both values: LSTCS ∼ (0.3–1)λ. Further improvement in the theory taking into account the dynamics of unmagnetized electrons may provide better agreement with observations.
Key Points
Super thin current sheets (STCSs) with half‐thickness about few electron gyroradii or less are observed during high‐velocity bulk flows
In the STCSs, the current is carried by unmagnetized electrons and stress balance is supported by off‐diagonal terms of their pressure tensor
In the STCSs, the higher energy electrons carry the current, while the low‐energy electrons support the stability of the STCS
We use data from the 2013–2014 Cluster Inner Magnetosphere Campaign, with its uniquely small spacecraft separations (less than or equal to electron inertia length, λe), to study multiscale magnetic ...structures in 14 substorm‐related prolonged dipolarizations in the near‐Earth magnetotail. Three time scales of dipolarization are identified: (i) a prolonged growth of the BZ component with duration ≤20 min; (ii) BZ pulses with durations ≤1 min during the BZ growth; and (iii) strong magnetic field gradients with durations ≤2 s during the dipolarization growth. The values of these gradients observed at electron scales are several dozen times larger than the corresponding values of magnetic gradients simultaneously detected at ion scales. These nonlinear features in magnetic field gradients denote the formation of intense and localized (approximately a few λe) current structures during the dipolarization and substorm current wedge formation. These observations highlight the importance of electron scale processes in the formation of a 3‐D substorm current system.
Key Points
Multiscale current structure formed during dipolarization growth
Intense current structures are transiently (≤2 s) observed at the leading and trailing edges of BZ pulses during dipolarization growth
Spatial scales of the intense current structures are ~100–200 km ~(2.5–5.0)λe
Cyclization of hydroxy-substituted
gem
-chloronitroso compounds under the action of bases affords cyclic nitronates, namely, isoxazoline
N
-oxides and 5,6-dihydro-4
H
-1,2-oxazine
N
-oxides. The ...process is reversible,
viz.
, the chloronitroso compounds are regenerated upon the action of hydrogen chloride on the cyclization products. A method for the synthesis of cyclic nitronates from aldols using the title reaction was developed. The cyclization mechanism was studied and the kinetic parameters of the process were determined using UV—Vis and IR monitoring and the results of quantum chemical calculations.
In this work, we review the results of observations by the Cluster/Research with Adaptive Particle Imaging Detectors (RAPID) energetic charged particle detector (∼>40 keV–∼1 MeV). The origin of ...energetic ions in the region upstream of the Earth's bow shock is compared under different solar wind conditions. We give a brief overview of the acceleration mechanisms of charged particles in the plasma sheet. Effective acceleration is associated with (multiple) interaction(s) of charged particles with multiscale magnetic structures and/or electromagnetic fluctuations, which are the consequences of reconnection or other plasma instabilities. The necessity of such acceleration mechanisms to reproduce the distributions of energetic particles on closed magnetic field lines is discussed. We review empirical models describing the distributions of charged particles. Several aspects of the dynamics of energetic particles during substorms and their influence on the dynamics of magnetic storms are shown. We advise to consider including the energetic particles at >40 keV in calculations of the plasma temperature and pressure during these dynamic processes.
Plain Language Summary
A fundamental scientific question is how plasma in the universe is heated up and accelerated. Understanding acceleration at supernovae shocks, of cosmic jets or laboratory plasmas still has many open questions. Near‐Earth space environment is an excellent laboratory to investigate plasma dynamics and to reveal the fundamental laws it obeys. Energetic plasmas are also hazardous for space satellites and play a key role in space weather. It is, therefore, necessary to study the energization of space plasmas, their distribution and consequences on the magnetospheric dynamics. In situ observations in the near‐Earth space by the Cluster satellites and the energetic particle detector, Research with Adaptive Particle Imaging Detectors (RAPID), reveal new insights in plasma acceleration, unexpected features in its distributions, and effects on substorm and geomagnetic storm dynamics. These observations also help space weather applications to determine the level of energetic particle intensities.
Key Points
Energetic particles at energies >40 keV have to be considered for the plasma temperature and pressure calculations
Effective acceleration is due to interaction of charged particles with multiscale magnetic structures and/or electromagnetic fluctuations
Direction of Interplanetary Magnetic Field leads to ion distribution asymmetries between Northern and Southern hemispheres
Observations of two successive prolonged dipolarizations in the geomagnetic tail (at a distance of
X
~ –18.3
R
E
from the Earth, where
R
E
is the Earth’s radius) according to the data obtained by the ...MMS mission are presented and analyzed. Eight dipolarization fronts (DF) were identified during these dipolarizations, and their propagation velocities and spatial scale were determined. The DF propagation velocities were found to be in the range between 130 and 360 km/s. The spatial scale of quasi-isolated DFs in the direction of their propagation at the beginning of the first dipolarization was ~1ρ
i
(where ρ
i
is the ion gyroradius), while the spatial scale of DFs observed in the flux pile up region was ~5ρ
i
. Using methods of multi-spacecraft observation, densities of electric currents related to DFs were determined on a sub-ion scale. It is demonstrated that thin (
) intense electron current structures with amplitudes of current density varying from 10 to 60 nA/m
2
that form complex multi-scale three-dimensional configurations are observed simultaneously with the DFs.
In this work, electrophysical features of the hard ferroelectric material PKP-35 are studied in a wide temperature range. Research object is a solid solution of lead zirconate-titanate (PZT) modified ...with some additives prepared by the conventional solid-state sintering method. The temperature dependences of the dielectric permittivity and dielectric losses in weak fields at frequencies of 1, 10, and 1000 Hz are obtained. The dielectric hysteresis loops at different temperatures are studied, the material features are revealed, the scope of application is determined.
Abstract
Deformable mirror (DM) is an active element that can change the shape of the surface to compensate for wavefront aberrations. Historically, the development of DMs started from piezostack ...deformable mirrors (PDM) due to their large stroke, flexibility in actuators geometry, high resonant frequency. However, the cost of PDMs is comparatively high because of their labor-intensive process of manufacturing. In the article innovative design of PDM is presented. The assembling of unconventional PDMs was carried out using piezoceramic combs. This step should allow to decrease number of technological steps, increase spatial resolution of the mirror and thereby reduce the cost of final product.
The authors consider electrophysical and mechanical parameters of piezoceramic materials based on lead zirconate titanate. The data show that modules with multilayer actuators with cross-sectional ...areas of 4 × 4 mm, nominal displacements of up to 4.3 µm, and element capacitances of 12 nF are designed to create cartridge-type deformable mirrors.
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