H. S. Fu

Formation of dipolarization fronts after current sheet thinning

Dipolarization front (DF)—a sharp boundary separating hot tenuous plasmas from cold dense plasmas—is a key structure responsible for particle acceleration and energy transport in the magnetotail. How such a structure is formed has been unclear so far. Two possible mechanisms suggested in previous studies are magnetic reconnection and spontaneous formation. Both of them require current sheet thinning as a prerequisite. However, observational evidence of the DF formation associated with current sheet thinning has not been reported. In this study, we present such an observation, showing the DF formation after current sheet thinning. We estimate the half thickness of the current sheet to be ∼1000 km and the rate of current sheet thinning as ∼38 km/s. We find that the DF is likely formed at XGSM ≈ −20 RE. During the current sheet thinning, the plasma becomes cold and dense; during DF formation, many magnetic islands are produced. Although current sheet thinning and DF formation have been individually analyzed in the previous studies, this study, for the first time, links the two transient processes in the magnetotail.Dipolarization front (DF)—a sharp boundary separating hot tenuous plasmas from cold dense plasmas—is a key structure responsible for particle acceleration and energy transport in the magnetotail. How such a structure is formed has been unclear so far. Two possible mechanisms suggested in previous studies are magnetic reconnection and spontaneous formation. Both of them require current sheet thinning as a prerequisite. However, observational evidence of the DF formation associated with current sheet thinning has not been reported. In this study, we present such an observation, showing the DF formation after current sheet thinning. We estimate the half thickness of the current sheet to be ∼1000 km and the rate of current sheet thinning as ∼38 km/s. We find that the DF is likely formed at XGSM ≈ −20 RE. During the current sheet thinning, the plasma becomes cold and dense; during DF formation, many magnetic islands are produced. Although current sheet thinning and DF formation have been individually analyzed ...

Electron jet detected by MMS at dipolarization front: Electron jet detected by MMS at dipolarization front

Using MMS high-resolution measurements, we present the first observation of fast electron jet (V-e similar to 2,000 km/s) at a dipolarization front (DF) in the magnetotail plasma sheet. This jet, w ...

Solar wind compressible turbulence near proton scales: Cluster observations

The solar wind compressible turbulence attracts more attention recently due to its possible role in plasma heating. Using the plasma density and magnetic field measured simultaneously by the Cluster C1 probe, we statistically investigate the wave characteristics of the proton-scale compressible turbulence. In most cases, the density and magnetic field strength fluctuations almost show no positive correlation, suggesting the absence of fast mode waves. Moreover, the magnetic compressibility Cb as measured by the level of magnetic fluctuations parallel to the background field, is enhanced continuously around proton scales and is consistent with kinetic Alfven wave (KAW) prediction. Interestingly, kinetic slow mode waves (KSW) are identified in a few cases through large values of Cb and plasma compressibility Cp, together with the the anti-correlation between n and B. We suggest that both KAW and KSW can account for the compressible fluctuations energy, while their relative proportions under certain plasma c...