Electron Surfing Acceleration in Current Sheet of Flares

1
Electron Surfing Acceleration in Current Sheet of
Flares

• Wang De Yu Lu Quan Ming
• Purple Mountain Observatory, Nanjing
• University of Science and Technology in China,
  Hefei

2
(No Transcript)
3
Electron acceleration in the magnetic
reconnection of flare

• (a) Electric field and induced electric field
  acceleration.
• Litvinenko et al. (1993)
• (b) Shock wave acceleration.
• Somov et al (1997)
• (c) Turbulence acceleration
• Miller (1997)

4
Some electrostatic waves can be excited during
the magnetic reconnection

• It is found from three dimensional particle
  simulation that
• some perpendicular propagating electrostatic
  waves can be excited during the magnetic
  reconnection
• Two examples

5
Lower Hybrid Drift Wave
Horiuchi and Sato (1999)
6
Fourier Spectrum of Lower Hybrid Drift Wave
Horiuchi and Sato (1999)
7
Buneman Instability ( Langmuir Wave )
Drake et al. (2003)
8

• A test electron is initially deeply trapped in
  the potential of electrostatic wave.
• The perpendicular magnetic field Bz deflects the
  test electron across the wave front, which like
  surfer ( ?? ) cutting across the face of an ocean
  wave, thus prevented the electron outrunning the
  wave.

9
(No Transcript)
10
Sketch of perpendicular propagatingelectrostatic
wave in magnetic reconnection
11
(No Transcript)
12
Wave Frame
13
Analytical approximation solution
14
Vx
Vz
Vz
Vx
15
Particle simulation
Particle
Ggt0
16
Particle Simulation
17
S
S
Vx
S
For different E0
Vz
18
Discussion

• The surfing acceleration for different amplitude
  E0 of electrostatic wave is different. A larger
  E0 is provided with a deeper trapping potential,
  it makes an electron can be accelerated to higher
  energy.

(2) A growing surfing acceleration velocity curve
of Vx has a turning point S. That means
the test electron de- trap from the potential of
electrostatic wave at this point, and then, the
test electron cannot be accelerated continuously
in the current sheet by electrostatic wave.
(3) The limited surfing acceleration velocity and
acceleration time.
The first term in the right hand of above
equation is a trapping term, the second and
third term in the right hand are de-trapping
terms. When Fy --? 0, the turning point is an
equilibrium about trapping term and de-trapping
term.
(a) Longitudinal magnetic field By--? 0,
it is found Vz--?0, so that the third term in
above equation approaches to zero.
19

• (b) By lt 0, the second term and third term
  cancel each other in the above equation.
• Therefore, the electron will de-trap from wave
  potential at larger velocity Vx0, when a stronger
  longitudinal magnetic field By is superposed in
  the current sheet.

20
Particle simulation for different Bylt 0
21
Spectrum of electron surfing acceleration
22

• IV.
  Conclusion
• The electron can be rapidly accelerated by
  perpendicular propagating electrostatic waves
  during the collisionless magnetic reconnection.
• The electron can be effectively accelerated by
  perpendicular propagating electrostatic waves
  only in the case of G gt 0. The velocity of
  acceleration electron in the x direction is
  approximate to .
• The electron acceleration are limited by the de-
  trapping from the potential of electrostatic
  waves the electron escape from the boundary of
  reconnection sheet and nonlinear evolution of
  electrostatic waves.
• Therefore, the electron acceleration by
  perpendicular propagating electrostatic waves
  should be a short period acceleration processes
  during the early stage of collisionless magnetic
  reconnection.