Origin of quasi-harmonic emission bands with fine structure in the dynamic spectra of high-frequency interpulses of the Crab pulsar

ABSTRACT We study the origin of quasi-harmonic emission bands with fine structure observed in the dynamic radiation spectra of high-frequency interpulses. The possible explanation of observed structure is based on the effect of double plasma resonance (DPR) at electron cyclotron harmonics realized in the magnetosphere of pulsar in a local radio emission source filled with non-relativistic plasma. The model of the source consists of neutral current sheet with a transverse magnetic field where plasma waves are generated due to DPR effect. It is shown that the emergence of emission bands and their frequency spacing are due to the inhomogeneity of the plasma and magnetic field along the current sheet, and their fine structure is due to the inhomogeneity of the current sheet in the direction orthogonal to it. Each quasi-harmonic emission band represents a system of elements of fine features of radiation that is generated by suprathermal electrons under DPR conditions. The observed upward drift of quasi-harmonic emission bands is due to the displacement of suprathermal electrons across the current sheet and an increase in the DPR frequencies with distance from the central plane of the layer.

PKU Energetic Particle Instrument

<p>The PKU energetic particle instrument (EPI) is designed to make measurements of the three-dimensional distribution of suprathermal electrons and ions with good time, energy and angular resolutions in the interplanetary space, respectively, at energies from 20 keV to 1 MeV and from 20 keV to 11 MeV.  The EPI consists of four dual-double-ended foil/magnet semi-conductor telescopes, which cleanly separate electrons in the energy range of 20–400 keV and ions from 20 keV–6 MeV. The output of front detectors is taken in anti-coincidence with center detectors, to achieve the low background. The magnet telescopes also employ the well-established dE/dx vs. total energy approach to determine the nuclear charge and mass of some ion species.</p>

Counterstreaming strahls and dropouts observed in pitch angle distributions of suprathermal electrons as possible signatures of local particle acceleration in the solar wind

<p>We present multi-spacecraft observations of pitch-angle distributions (PADs) of suprathermal electrons at ~1 AU which cannot be easily interpreted within the classical paradigm that all suprathermal electrons originate in the solar corona. We suggest that suprathermal electrons accelerated locally in the solar wind are mixed up with the well-known population of electrons of solar origin. Using PIC simulations, we show that key PAD features such as (i) heat flux dropouts and vertical PAD stripes encompassing reconnecting current sheets (RCSs), (ii) bi-directionality of strahls, and (iii) dramatically different PAD patterns observed in different energy channels can be explained by the behavior of electrons accelerated up to hundreds eV directly in the solar wind while thermal particles pass through local RCSs and/or dynamical 3D plasmoids (or 2D magnetic islands).</p>