Formation of Alfvénic resonance layers in magnetic reconnection. Issue 4 (18th April 2016)

• Record Type: Journal Article
• Authors: Li, L. J.; Tian, L. P.; Ma, Z. W.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 4(2016:Apr.)
• Page Start: 3170
• Page End: 3180
• Publication Date: 2016-04-18
• Subjects: magnetic reconnection -- Alfvénic resonance -- MHD -- shear flow; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022373
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: In the framework of two‐dimensional incompressible MHD, we investigate the formation of Alfvénic resonance layers with different super‐Alfvénic shear flows. It is found that Alfvénic resonance layers are formed in the inflow region for the cases with the shear flow thickness larger than the current sheet thickness. The Alfvénic layers exist at where the flow velocity is equal to the local Alfvén speed and slowly drift away from the current sheet region as a magnetic island develops. The ratio ( D ) between the separation of the Alfvénic resonance layers and the current sheet thickness plays a crucial role on magnetic reconnection. It is found that D ~ 3 is a critical value, which is about the saturated size of a magnetic island in magnetic reconnection without super‐Alfvénic shear flow. For D < 3, the super‐Alfvénic shear flow shows mainly a suppressing effect on magnetic reconnection and the peaked reconnection rate drops below the rate without a super‐Alfvénic shear flow. When D > 3, the boosting effect of Kelvin‐Helmholtz instability surpasses the suppressing effect by Alfvénic resonance and the peaked reconnection rate is larger than that without a super‐Alfvénic shear flow. For D ~ 5, the super‐Alfvénic shear flow gives rise to a strongest boosting effect on magnetic reconnection. Possible applications are briefly discussed. Key Points: Alfvén resonance layers are generated by super‐Alfvénic shear flow with flow shear thickness larger than the current sheet thickness The ration D of the separation distance and the current sheet thickness layers plays a crucial role on dynamics of magnetic reconnection There are two critical values of D: Flows with D~3 and ~5 show the strongest boosting and suppressing effects on reconnection, respectively