Dynamics of particles in the vicinity of the heliospheric current sheet: observations versus theory Olga Khabarova Valentina Zharkova Gang Li [email protected]

Dynamics of particles in the vicinity of the heliospheric current sheet:

observations versus theory

Olga Khabarova Olga Khabarova Valentina Zharkova Valentina Zharkova Gang Li Gang Li

[email protected]

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. 11th European Space Weather Week. Recent Advances in Space Weather ScienceRecent Advances in Space Weather Science

• Behaviour of particles in a vicinity of reconnecting Behaviour of particles in a vicinity of reconnecting current sheets in the solar wind: current sheets in the solar wind:

- theoretical points of view; PIC-modelling - theoretical points of view; PIC-modelling

- observationsobservations

Theoretical aspects of particle acceleration due to Theoretical aspects of particle acceleration due to magnetic island dynamics in the solar windmagnetic island dynamics in the solar wind

• Combination of theoretical ideasCombination of theoretical ideas.. An application of a An application of a new paradigm to explanation of observations. new paradigm to explanation of observations.

Olga Khabarova Olga Khabarova Valentina Zharkova Valentina Zharkova Gang Li Gang Li

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

((Verboncouer & Gladd, 1995)Verboncouer & Gladd, 1995)

Vinflow 0.01 Valfven

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 protontransit protonbounced protonbounced proton

Trajectories of electrons and protons near the reconnecting current sheet.

midplain

midplain

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

2.223 MeV footpoints (ions) on opposite sides of the flaring loop arcade are displaced from the corresponding 0.2–0.3 MeV footpoints (electrons).

protonsprotons

electronselectrons

Zharkova, Khabarova, ApJ, 2012

HCSHCS

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 10-100 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)Z (GSE)Z (GSE)Z (GSE)

Y (GSE)Y (GSE)

X (GSE)X (GSE)

ZZ YY

XX(GSE)(GSE)

XX ZZ

YY

(model)(model)

observationsobservations

10-

6

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 (φB); d-f) spectrograms of the electron flux at the energies of370 eV, 84 eV and 27 eV, respectively, as a function of pitch angle.

340 eV340 eV

84 eV84 eV

27 eV27 eV


Density=100 cm-3

Bz0=10-8TBy=0.1Bz0

Bx=-0.02Bzo

Density=10 cm-3

Bz0=10-8TBy=0.01Bz0

Bx=-0.02Bzo

10 cm-3 Density=100 cm-3

Bz0=10-9TBy=0.01Bz0

Bx=-0.002Bzo

Density=10 cm-3

Bz0=10-9TBy=0.1Bz0

Bx=-0.02Bzo


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):Goldstein, Matthaeus & Ambrosiano (1986): the maximum energy the maximum energy achievable during the magnetic reconnection at the HCS should be achievable during the magnetic reconnection at the HCS should be ~100 ~100 keV.keV.

Zharkova & Khabarova (2012; 2014):Zharkova & Khabarova (2012; 2014): the maximum energy achievable the maximum energy achievable during the magnetic reconnection at the HCS may be during the magnetic reconnection at the HCS may be ~ MeV.~ MeV.

Theory: tearing instability of current Theory: tearing instability of current sheets leads to magnetic island sheets leads to magnetic island

formationformation

Drake et al, 1998, 1999, Drake et al, 1998, 1999, 2006, Daughton et al, 20112006, Daughton et al, 2011

Theory: magnetic island contraction Theory: magnetic island contraction and merging can accelerate particlesand merging can accelerate particles

Zank G.P., le Roux J.A., Webb G.M., Zank G.P., le Roux J.A., Webb G.M., Dosch A., & O. Khabarova. Dosch A., & O. Khabarova.

Particle acceleration via reconnection Particle acceleration via reconnection processes in the supersonic solar wind. processes in the supersonic solar wind. Astrophysical Journal, V.797, 2014Astrophysical Journal, V.797, 2014

The dominant charged particle energization processes are

1) the electric field induced by magnetic island merging,

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-scaleSmall-scale magnetic island formation magnetic island formation predominantly occurs near the HCSpredominantly occurs near the HCS

Cartwright, M. L., and M. B. Moldwin (2010), Cartwright, M. L., and M. B. Moldwin (2010), Heliospheric evolution of solar wind small-scale Heliospheric evolution of solar wind small-scale magnetic flux ropes. J. Geophys. Res., 115, A08102magnetic flux ropes. J. Geophys. Res., 115, A08102

Particles can be Particles can be accelerated at least to accelerated at least to keV energies at the keV energies at the HCS HCS and re-accelerated in and re-accelerated in dynamically changing dynamically changing magnetic islands near magnetic islands near the HCSthe 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 A specific form of the HCS (ripples on the HCS) is favorable for keeping the HCS) is favorable for keeping

magnetic islands and particle magnetic islands and particle acceleration to high energiesacceleration to high energies

ACE and WIND spacecraft ACE and WIND spacecraft were 150 Re apart. were 150 Re apart.

A clear magnetic field vector A clear magnetic field vector rotation is seen in magnetic rotation is seen in magnetic islands, that occurs islands, that occurs simultaneously with energetic simultaneously with energetic particle flux increasesparticle flux increases

AC

EA

CE

WIN

DW

IND

Khabarova, Zank, Li, le Roux, Webb, Dosch, submitted to ApJ

Particle acceleration associated with islands near the HCS (an after -CME event)Particle acceleration associated with islands near the HCS (an after -CME event)


Magnetic reconnectionMagnetic reconnection

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

Particle acceleration associated with islands near the HCS (a pre-CME event)Particle acceleration associated with islands near the HCS (a pre-CME event)


Particle acceleration associated with islands near the HCS (a pre-CME event)Particle acceleration associated with islands near the HCS (a pre-CME event)


• 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 (Olga Khabarova ([email protected]@izmiran.ru) )

Valentina Zharkova Valentina Zharkova

Gang Li Gang Li

Documents

Dynamics of particles in the vicinity of the heliospheric current sheet: observations versus theory Olga Khabarova Valentina Zharkova Gang Li [email protected]