Why does the magnetotail reconnection have significantly varying
strength of fluctuation?
Abstract
Magnetic reconnection in the Earth’s magnetosphere is usually manifested
as a turbulent state in which the large amplitude fluctuations disrupt
the main reconnection layer, while it occasionally shows a clear
structured reconnection layer with weak fluctuations, i.e., a laminar
state. To understand why the fluctuation strength varies significantly
among reconnection in the Earth’s magnetotail, we have examined tens of
reconnection events in the Earth’s magnetotail observed by the
Magnetospheric Multi-Scale (MMS) mission. We primarily examine the
correlation between fluctuation strength in reconnection, quantified by
dBrec and dErec, and reconnection inflow conditions and upstream solar
wind conditions. The fluctuation strength (dBrec, dErec) for these
reconnections ranges from 0.7 to 10 nT and 0.8 to 30 mV/m, respectively.
Our analysis unveils significant correlations between inflow conditions
including Alfven speed VA,in, , magnetic disturbances dBin and electric
field disturbances dEin with (dBrec, dErec). Fluctuation strength also
shows good correlations with interplanetary magnetic field (IMF) cone
angle and solar wind dynamic pressure, whereas it has an unclear
relationship with substorm and storm activities. We suggest that inflow
reconnection conditions act as the principal catalysts for turbulence
during reconnection.