Space Weather of the Heliosphere: Processes and Forecasts Proceedings IAU Symposium No. 335, 2017 C. Foullon & O.E. Malandraki, eds. c  International Astronomical Union 2018 doi:10.1017/S1743921318000443 Acceleration of Solar Wind Particles Passing through the 3D Heliospheric Current Sheet Valentina V. Zharkova Department of Mathematics, Physics and Electrical Engineering, University of Northumbria, Newcastle upon Tyne, NE1 8ST, UK email: valentina.zharkova@northumbria.ac.uk Abstract. Additional acceleration of protons and electrons passing through a 3D reconnecting current sheet (RCS) of the solar corona and heliosphere is investigated with PIC approach. The simulation confirms spatial separation of electrons and protons and generation of a polarisa- tion electric field induced by separated particles. In the heliospheric current sheet with a weak magnetic field there are two populations of particles: transit and bounced. The transit particles (both protons and electrons) are accelerated to high energies while the bounced electrons fail to reach the midplane. Instead they form an electron cloud of horseshoe or medallion types at some distance D from its midplane, which is larger for bigger guiding field magnitudes. These energetic electrons and protons appearing near the HCS boundaries can be a great danger for the satellites crossing the sector boundaries. Keywords. Sun: flares, plasmas, acceleration of particles, magnetic field 1. Introduction The interplanetary magnetic field (IMF) in the heliosphere is divided into two sectors of the open magnetic field lines with the opposite magnetic field polarities separated by the equatorial plane providing a magnetic field reversal known as the sector boundary (SB). The latter is considered to be the heliospheric current sheet (HCS), which gov- erns the magnetic field reversals from and toward the Sun along Parker  s spiral (see http://wso.stanford.edu/gifs/HCS.html). Simulations of particle trajectories were carried out by using a test particle approach in a 3D magnetic configuration with the guiding field emulating a simple case of magnetic reconnection for a constant reconnection electric field (Zharkova and Gordovskyy 2004) or for those enhanced near the magnetic X-nullpoint due to anomalous resistivity (Wood and Neukirch 2005). Zharkova and Gordovskyy (2004) and Zharkova and Agapitov (2009) showed that the trajectories of particles with the opposite charges (electrons or protons) can be either fully symmetric or strongly asymmetric towards the midplane of the RCS depending on the ratio between the magnetic field components. As a result, some fraction of the released magnetic energy is transformed into kinetic energy of accelerated particles. The energy spectra of these particles also depend on a magnetic field topology, electric field strength and the magnitude of a transverse magnetic field. Accelerated particles gain energies up to 100 keV for the electrons and up to a few tens MeV for the protons (Zharkova and Gordovskyy 2005; Wood and Neukirch 2005; Zharkova and Agapitov 2009). Recent study with particle-in-cell (PIC) of particle acceleration in the 3D heliospheric current sheet with low magnitudes of magnetic field relevant to the interplanetary mag- netic field at the Earth orbit (Zharkova and Khabarova 2012) allowed to provide the 54 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1743921318000443 Downloaded from https://www.cambridge.org/core. IP address: 18.210.27.112, on 12 Dec 2021 at 07:27:39, subject to the Cambridge Core terms of use, available at