Particle acceleration in 3D single current sheets formed in the solar corona and heliosphere: PIC approach

Acceleration of protons and electrons in a reconnecting current sheet (RCS) is investigated with the test particle and particle-in-cell (PIG) approaches in a 3D magnetic topology. PIG simulations confirm a spatial separation of electrons and protons with respect to the midplane depending on the guiding field. Simulation reveals that the separation occurs in magnetic topologies with strong guiding fields and lasts as long as the particles are kept dragged into a current sheet. This separation produces a polarisation electric field induced by the plasma feedback to a presence of accelerated particles, which shape can change from symmetric towards the midplane (for weak guiding field) to fully asymmetric (for strong guiding field). Particles are found accelerated at a midplane of any current sheets present in the heliosphere to the energies up to hundred keV for electrons and hundred MeV for protons. The maximum energy gained by particles during their motion inside the current sheet is defined by its magnetic field topology (the ratio of magnetic field components), the side and location from the X-nullpoint, where the particles enter a current sheet. In strong magnetic fields of the solar corona with weaker guiding fields, electrons are found circulating about the midplane to large distances where proton are getting accelerated, creating about the current sheet midplane clouds of high energy electrons, which can be the source of hard X-ray emission in the coronal sources of flares. These electrons are ejected into the same footpoint as protons after the latter reach the energy sufficicent to break from a current sheet. In a weaker magnetic field of the heliosphere the bounced electrons with lower energies cannot reach the midplane turning instead at some distance D before the current sheet midplane by 180 degrees from their initial motion. Also the beams of accelerated transit and bounced particles are found to generate turbulent electric fields in a form of Langmuir waves (electrons) or ion-acoustic waves (protons)

Stationary and impulsive injection of electron beams in converging magnetic field

In this work we study time-dependent precipitation of an electron beam injected into a flaring atmosphere with a converging magnetic field by considering collisional and Ohmic losses with anisotropic scattering and pitch angle diffusion. Two injection regimes are investigated: short impulse and stationary injection. The effects of converging magnetic fields with different spatial profiles are compared and the energy deposition produced by the precipitating electrons at different depths and regimes is calculated. The time dependent Fokker-Planck equation for electron distribution in depth, energy and pitch angle was solved numerically by using the summary approximation method. It was found that steady state injection is established for beam electrons at 0.07-0.2 seconds after the injection onset depending on the initial beam parameters. Energy deposition by a stationary beam is strongly dependent on a self-induced electric field but less on a magnetic field convergence. Energy depositions by short electron impulses are found to be insensitive to the self-induced electric field but are strongly affected by a magnetic convergence. Short beam impulses are shown to produce sharp asymmetric hard X-ray bursts within a millisecond timescale often observed in solar flares.Comment: 14 pages, 15 figures, Astronomy and Astrophysics (accepted

Attitudes toward the health of men that regularly occupy in a trainer hall.

It is accepted to consider that by motivation for people that practice in a trainer hall is an improvement of health and original appearance. The aim of this research was to determine whether there is training by part of forming of positive attitude toward the health of men-sportsmen-amateurs that occupy in a trainer hall. In research took part 100 men that engage in the power training in one of three trainer halls of Warsaw. Investigational divided by two groups: 50 persons that occupy in a trainer hall more than one year, but no more than 3 years (group A) and 50 persons that practice more than 3 (group B). It is well-proven that training positively influences on the emotional state of men. It was discovered at the same time, that than greater experience of sportsman-amateur, the considerably more often he used additions (including by a stimulant). There was no medical control in both groups. Positive influence of the power training shows that they can be the important element of prophylaxis and physiotherapy

Particle acceleration in a reconnecting current sheet: PIC simulation

The acceleration of protons and electrons in a reconnecting current sheet (RCS) is simulated with a particle-in-cell (PIC) 2D3V code for the proton-to-electron mass ratio of 100. The electro-magnetic configuration forming the RCS incorporates all three components of the magnetic field (including the guiding field) and a drifted electric field. PIC simulations reveal that there is a polarisation electric field that appears during acceleration owing to a separation of electrons from protons towards the midplane of the RCS. If the plasma density is low, the polarisation field is weak and the particle trajectories in the PIC simulations are similar to those in the test particle (TP) approach. For the higher plasma density the polarisation field is stronger and it affects the trajectories of protons by increasing their orbits during acceleration. This field also leads to a less asymmetrical abundances of ejected protons towards the midplane in comparison with the TP approach. For a given magnetic topology electrons in PIC simulations are ejected to the same semispace as protons, contrary to the TP results. This happens because the polarisation field extends far beyond the thickness of a current sheet. This field decelerates the electrons, which are initially ejected into the semispace opposite to the protons, returns them back to the RCS, and, eventually, leads to the electron ejection into the same semispace as protons. Energy distribution of the ejected electrons is rather wide and single-peak, contrary to the two-peak narrow-energy distribution obtained in the TP approach. In the case of a strong guiding field, the mean energy of the ejected electrons is found to be smaller than it is predicted analytically and by the TP simulations.Comment: 12 pages, 11 figures, J. Plasma Physics (accepted

Interaction of the modulated electron beam with inhomogeneous plasma: plasma density profile deformation and langmuir waves excitation

Nonlinear deformation of the initially linear plasma density profile due to the modulated electron beam is studied via computer simulation. In the initial time period the field slaves to the instantaneous profile of the plasma density. Langmuir waves excitation is suppressed by the density profile deformation. The character of the plasma density profile deformation for the late time period depends significantly on the plasma properties. Particularly, for plasma with hot electrons quasi-periodic generation of ion-acoustic pulses takes place in the vicinity of the initial point of plasma resonance.За допомогою комп’ютерного моделювання досліджується нелінійна деформація первісно лінійного профілю концентрації плазми модульованим електронним пучком. В початкові моменти часу поле підлаштовується під миттєві розподіли густини плазми. Збудження ленгмюрівських хвиль обмежується деформацією профілю концентрації. Характер деформації профілю концентрації плазми істотно залежить від параметрів плазми. Зокрема, для плазми з гарячими електронами поблизу первісної точки плазмового резонансу має місце квазіперіодична генерація іонно-акустичних імпульсів.С помощью компьютерного моделирования исследуется нелинейная деформация первоначально линейного профиля концентрации плазмы модулированным электронным пучком. В начальные моменты времени поле подстраивается под мгновенное распределение концентрации плазмы. Возбуждение ленгмюровских волн ограничивается деформацией профиля концентрации. Характер деформации профиля концентрации плазмы существенно зависит от параметров плазмы. В частности, для плазмы с горячими электронами в окрестности первоначальной точки плазменного резонанса имеет место квазипериодическая генерация ионно-акустических импульсов

Plasma dynamics in the vicinity of the local plasma resonance point excited by pumping electric field or modulated electron beam

Excitation of the HF electric field in the local plasma resonance region (LPRR) of inhomogeneous plasma by pumping electric field or modulated electron beam results to appearance of the ponderomotive force that presses plasma out of this region. Density cavity is formed in the LPRR due to this field. Further dynamics in this region depends on the plasma properties. For plasma with hot electrons ion-acoustic pulses run away from the cavity. At the local density maximum the new peak of electric field is excited. It results to the formation of new density cavity, etc. For isothermal plasma the density jump is formedВозбуждение высокочастотного электрического поля в области локального плазменного резонанса (ОЛПР) неоднородной плазмы электрическим полем накачки или модулированным электронным пучком приводит к появлению пондеромоторной силы, выдавливающей плазму из этой области. Под действием этого поля в ОЛПР формируется ямка плотности. Последующая динамика в этой области зависит от свойств плазмы. Для плазмы с горячими электронами ионно-акустические импульсы разбегаются от ямки плотности. На локальном максимуме концентрации возбуждается новый всплеск электрического поля, приводящий к формированию новой ямки плотности, и т.д. В изотермической плазме формируется скачок плотности.Збудження високочастотного електричного поля в області локального плазмового резонансу (ОЛПР) неоднорідної плазми електричним полем накачування або модульованим електронним пучком приводить до появи пондеромоторної сили, яка витискає плазму з цієї області. Під дією цього поля в ОЛПР формується ямка густини. Подальша динаміка в цій області залежить від властивостей плазми. Для плазми з гарячими електронами іонно-акустичні імпульси розбігаються від ямки густини. На локальному максимумі концентрації збуджується новий сплеск електричного поля, що приводить до формування нової ямки густини, і т.д. В ізотермічній плазмі формується стрибок густини

Parallel electric field generation by Alfven wave turbulence

{This work aims to investigate the spectral structure of the parallel electric field generated by strong anisotropic and balanced Alfvenic turbulence in relation with the problem of electron acceleration from the thermal population in solar flare plasma conditions.} {We consider anisotropic Alfvenic fluctuations in the presence of a strong background magnetic field. Exploiting this anisotropy, a set of reduced equations governing non-linear, two-fluid plasma dynamics is derived. The low-$\beta$ limit of this model is used to follow the turbulent cascade of the energy resulting from the non-linear interaction between kinetic Alfven waves, from the large magnetohydrodynamics (MHD) scales with $k_{\perp}\rho_{s}\ll 1$ down to the small "kinetic" scales with $k_{\perp}\rho_{s} \gg 1$, $\rho_{s}$ being the ion sound gyroradius.} {Scaling relations are obtained for the magnitude of the turbulent electromagnetic fluctuations, as a function of $k_{\perp}$ and $k_{\parallel}$, showing that the electric field develops a component parallel to the magnetic field at large MHD scales.} {The spectrum we derive for the parallel electric field fluctuations can be effectively used to model stochastic resonant acceleration and heating of electrons by Alfven waves in solar flare plasma conditions

Kinetic modeling of particle acceleration in a solar null point reconnection region

The primary focus of this paper is on the particle acceleration mechanism in solar coronal three-dimensional reconnection null-point regions. Starting from a potential field extrapolation of a Solar and Heliospheric Observatory (SOHO) magnetogram taken on 2002 November 16, we first performed magnetohydrodynamics (MHD) simulations with horizontal motions observed by SOHO applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan-plane of the null-point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms in the simulated pre-flare phase, featuring a power-law index of about -1.78. This work provides a first step towards bridging the gap between macroscopic scales on the order of hundreds of Mm and kinetic scales on the order of cm in the solar corona, and explains how to achieve such a cross-scale coupling by utilizing either physical modifications or (equivalent) modifications of the constants of nature. With their exceptionally high resolution - up to 135 billion particles and 3.5 billion grid cells of size 17.5 km - these simulations offer a new opportunity to study particle acceleration in solar-like settings.Comment: 18 pages, 12 figure