Bursty emission of whistler waves in association with plasmoid collision

4Citations
Citations of this article
8Readers
Mendeley users who have this article in their library.

Abstract

A new mechanism to generate whistler waves in the course of collisionless magnetic reconnection is proposed. It is found that intense whistler emissions occur in association with plasmoid collisions. The key processes are strong perpendicular heating of the electrons through a secondary magnetic reconnection during plasmoid collision and the subsequent compression of the ambient magnetic field, leading to whistler instability due to the electron temperature anisotropy. The emissions have a bursty nature, completing in a short time within the ion timescales, as has often been observed in the Earth's magnetosphere. The whistler waves can accelerate the electrons in the parallel direction, contributing to the generation of high-energy electrons. The present study suggests that the bursty emission of whistler waves could be an indicator of plasmoid collisions and the associated particle energization during collisionless magnetic reconnection.

Figures

  • Figure 1. Time evolution of the main reconnection exhaust. (a–c) Two-dimensional snapshots of the out-of-plane electron bulk velocity at (a) tωci = 90, (b) 106, and (c) 114. (d–f) Localized profiles at tωci = 106 for (d) Vez, (e) Te⊥/Te‖, and (f) Ey + (Vi×B)y . (g–i) The same profiles as in (d–f) but in a different area at tωci = 114. The black solid curves (a–c) and gray solid curves (d–i) represent the magnetic field lines, and the gray dashed boxes in (b) and (c) indicate the areas shown in (d–f) and (g–i), respectively. The black dashed curves in (f) and (i) are the field lines traced at each time step from (x,z)= (0,−18.5), a point far away from the areas in (f) and (i).
  • Figure 2. Properties of the electromagnetic waves propagating along the field lines. (a) Time evolution of Ey + (Vi×B)y along the field line traced from (x,z)= (0,−18.5) at each time step. The vertical axis is the field-aligned coordinate with l = 0 at the Equator point where Bx = 0 is satisfied. (b) Fourier amplitude calculated along the field line and averaged over k‖λ∗e > 0.5 at each time step, where λ∗e is the local electron inertia length. (c) The wave spectrum (color contour) of Ey + (Vi×B)y in the ωr − k‖ space for the area indicated by the black dashed box in (a). The theoretical curves of the dispersion relation Eq. (1) for the whistler instability driven by the electron temperature anisotropy are superposed by a solid curve for ωr , the real frequency, and by a dashed curve for γ , the growth rate.
  • Figure 3. Schematic diagram showing the generation mechanism of a bursty emission of whistler waves in association with plasmoid collision. (a) When plasmoid collision occurs in the downstream edge of the main reconnection exhaust, a secondary reconnection takes place. The electron outflow jets (sky blue arrows) are generated in the z direction, leading to the perpendicular heating (red filled circles) of the electrons in the regions downstream of the secondary x-line. (b) As the plasmoid merging proceeds, the perpendicularly heated electrons move to the edge of the larger plasmoid (current sheet) and are compressed due to the magnetic tension force. As a result, the electrons become strongly magnetized so that a favorable condition for the whistler emission (blue arrows) is produced.
  • Figure 4. Reduced distribution functions of the electrons in (a) parallel and (b) perpendicular directions. The distribution functions are averaged over the field line (−50≤ l/λi ≤ 0) traced from (x,z)= (0,−18.5) at tωci = 106 (green curves), 114 (red curves), and 120 (blue curves). The dashed curves indicate the distribution function of the initial background (lobe) electrons.

References Powered by Scopus

Rapid magnetic reconnection in the earth's magnetosphere mediated by whistler waves

268Citations
N/AReaders
Get full text

Observation of energetic electrons within magnetic islands

236Citations
N/AReaders
Get full text

Quasi-perpendicular shocks: Length scale of the cross-shock potential, shock reformation, and implication for shock surfing

148Citations
N/AReaders
Get full text

Cited by Powered by Scopus

Collisionless Magnetic Reconnection and Waves: Progress Review

64Citations
N/AReaders
Get full text

Observations of Flux Ropes With Strong Energy Dissipation in the Magnetotail

38Citations
N/AReaders
Get full text

Observations of whistler waves in two sequential flux ropes at the magnetopause

12Citations
N/AReaders
Get full text

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Cite

CITATION STYLE

APA

Fujimoto, K. (2017). Bursty emission of whistler waves in association with plasmoid collision. Annales Geophysicae, 35(4), 885–892. https://doi.org/10.5194/angeo-35-885-2017

Readers over time

‘17‘18‘20‘2101234

Readers' Seniority

Tooltip

PhD / Post grad / Masters / Doc 3

75%

Professor / Associate Prof. 1

25%

Readers' Discipline

Tooltip

Physics and Astronomy 4

100%

Save time finding and organizing research with Mendeley

Sign up for free
0