Dynamics of particles in the vicinity of the heliospheric current sheet: observations versus theory Olga Khabarova  Valentina Zharkova  Gang Li CSPAR, University of Alabama in Huntsville, USA Pushkov Institute of terrestrial magnetism and radiowave propagation (IZMIRAN), Russia University of Northumbria, Newcastle Upon Tyne, United Kingdom 11th European Space Weather Week. Recent Advances in Space Weather Science

Behaviour of particles in a vicinity of reconnecting current sheets in the solar wind: Behaviour of particles in a vicinity of reconnecting current sheets in the solar wind: - theoretical points of view; PIC-modelling - observations - observations  Theoretical aspects of particle acceleration due to magnetic island dynamics in the solar wind Combination of theoretical ideas. An application of a new paradigm to explanation of observations. Combination of theoretical ideas. An application of a new paradigm to explanation of observations. Olga Khabarova  Valentina Zharkova  Gang Li

Siversky, Zharkova, JPP, 2009; Zharkova,Gordovsky, ApJ, 2004; Zharkova,Agapitov, JPP, 2009

(Verboncouer & Gladd, 1995) V inflow  0.01 V alfven Drift electric field Siversky, Zharkova, JPP, 2009; Zharkova,Gordovsky, ApJ, 2004; Zharkova,Agapitov, JPP, 2009 In order to avoid numerical instabilities in the PIC code (Verboncoeur et al. 1995), the following constrains are to be satisfied Δt is the time step, Δξ is the grid step in any direction

Proton trajectories are shown in red, and electron trajectories are shown in blue. transit proton bounced proton Trajectories of electrons and protons near the reconnecting current sheet. midplain

Separation of opposite charged particles around the current sheet leads to the occurrence of a strong electric field

Siversky, T. V., & Zharkova, V. V. 2009, J.Plasma Phys., 75, 619

HXR and γR imaging Hurford et al., 2006 ApJ MeV footpoints (ions) on opposite sides of the flaring loop arcade are displaced from the corresponding 0.2–0.3 MeV footpoints (electrons).

protonselectrons Zharkova, Khabarova, ApJ, 2012 HCS

A regular structure of the heliospheric current sheet A 3D reconstructed velocity plot, from the viewpoint of a remote observer (STEL data).

The HCS is suggested to undergo a continuous reconnection process. The current sheet thickness is about a size of the proton gyroradius. The simulation region is made larger by a factor of to the both sides from the midplane. The background magnetic field is stationary during the whole simulation. Plasma particles in the PIC simulations are considered to generate their own electric and magnetic fields. Zharkova, Khabarova, Astrophysical Journal, 752, 1, 35 (2012) Z (GSE) Y (GSE) X (GSE) Z Y X (GSE) X Z Y (model) observations

 Zharkova, Khabarova, ApJ, 2012; Khabarova, Zastenker, SolPh 2011

Crossing of a thin sector boundary, the 3-second Wind SWE 3DP data: a) IMF magnitude; b) the in-ecliptic component of the IMF (Bx, GSE); c) azimuthal angle of the IMF (φ B ); d-f) spectrograms of the electron flux at the energies of 370 eV, 84 eV and 27 eV, respectively, as a function of pitch angle. 340 eV 84 eV 27 eV Zharkova, Khabarova, ApJ, 2012

Density=100 cm -3 B z0 =10 -8 T B y =0.1B z0 B x =-0.02B zo Density=10 cm -3 B z0 =10 -8 T B y =0.01B z0 B x =-0.02B zo 10 cm -3 Density=100 cm -3 B z0 =10 -9 T B y =0.01B z0 B x =-0.002B zo Density=10 cm -3 B z0 =10 -9 T B y =0.1B z0 B x =-0.02B zo Zharkova, Khabarova, ApJ, 2012

The results can solve the problem of mismatches between polarity reversal signatures in suprathermal electron pitch angle spectrograms and changes of azimuth angle of the magnetic field. Kahler, Lin (Geophys. Res. Lett., 1994); Crooker, Kahler, Larson, Lin (J. Geophys. Res., 2004) The main idea of the [Zharkova & Khabarova, ApJ (2012)] paper: small- and medium-scale features of the IMF and plasma characteristics observed near the HCS may be explained simultaneously only if magnetic reconnection was assumed to occur simultaneously and re-currently in many places on the HCS.

Acceleration of particles in current sheets due to magnetic reconnection (Zelenyi et al., 2013; Drake et al. 2010, 2013; Büchner et al, 2010; Lapenta 2012 etc.). Energization of particles up to MeV in the Earth’s magnetotail [Zelenyi, Lominadze & Taktakishvili (1990); Ashour-Abdalla et al. (2011) ], but it is still disputable for the HCS, because of some lack of observations. It is furthermore believed that there no particle acceleration in the keV- MeV range is associated with the magnetic reconnection exhausts in the solar wind, i.e. there is no significant local acceleration at the reconnecting HCS [Gosling et al. (2005)]. Goldstein, Matthaeus & Ambrosiano (1986): the maximum energy achievable during the magnetic reconnection at the HCS should be ~100 keV. Zharkova & Khabarova (2012; 2014): the maximum energy achievable during the magnetic reconnection at the HCS may be ~ MeV.

Theory: tearing instability of current sheets leads to magnetic island formation Drake et al, 1998, 1999, 2006, Daughton et al, 2011 Theory: magnetic island contraction and merging can accelerate particles Zank G.P., le Roux J.A., Webb G.M., Dosch A., & O. Khabarova. Particle acceleration via reconnection processes in the supersonic solar wind. Astrophysical Journal, V.797, 2014 The dominant charged particle energization processes are 1) 1)the electric field induced by magnetic island merging, 2) 2) magnetic island contraction. In both cases, the magnetic island topology ensures that charged particles are trapped in regions where they can experience repeated interactions with either the induced electric eld or contracting magnetic islands.

Small-scale magnetic island formation predominantly occurs near the HCS Cartwright, M. L., and M. B. Moldwin (2010), Heliospheric evolution of solar wind small-scale magnetic flux ropes. J. Geophys. Res., 115, A08102 Particles can be accelerated at least to keV energies at the HCS and re-accelerated in dynamically changing magnetic islands near the HCS

Small-scale magnetic islands in the solar wind and their role in particle acceleration. Part 1: Dynamics of magnetic islands near the heliospheric current sheet. Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ A specific form of the HCS (ripples on the HCS) is favorable for keeping magnetic islands and particle acceleration to high energies

ACE and WIND spacecraft were 150 Re apart. A clear magnetic field vector rotation is seen in magnetic islands, that occurs simultaneously with energetic particle flux increases ACE WIND Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ

Particle acceleration associated with islands near the HCS (an after -CME event) Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ

Magnetic reconnection a) at the leading edge of an ICME;b) behind the ICME

Particle acceleration associated with islands near the HCS (a pre-CME event) Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ

Particle acceleration associated with islands near the HCS (a pre-CME event) Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ

A magnetic reconnection is a re-currently ongoing process that takes place at the heliospheric current sheet (HCS). The separation of particles of the opposite sign during the magnetic reconnection at the HCS leads to strong particle acceleration The local energetic particle flux enhancements might be explained by particle energization occurring near the HCS during dynamical evolution of secondary current sheets and small-scale magnetic islands. These structures are supposed to trap and re-accelerate particles (initially accelerated at the HCS) up to MeV/nucleon. Effectiveness of this process depends on the topology of the HCS (ripples). Olga Khabarova Valentina Zharkova Gang Li Gang Li