During a dayside magnetopause crossing, the Magnetospheric Multiscale (MMS) mission observed a series of magnetic depletions in the total magnetic field, mainly due to the fluctuation of the component normal to the magnetopause. These fluctuations are adjacent to signatures suggesting that the MMS is at, or close to (<d_i), a magnetic reconnection electron diffusion region (EDR). The temporal and spatial scales of the fluctuations are too short for the ions to be affected. In this paper we investigate the origin of these fluctuations, finding that they can develop from temporal variations of the reconnection rate at the nearby EDR. Indeed asymmetric reconnecting current sheets, and the nearby regions, are subject to multiple different instabilities, and may be affected by waves and turbulence activity. Here we suggest such oscillations in the normal component of the magnetic field can be interpreted either as i) electron‐scale structures, forming due to changes in the outflow speed and the corresponding changes in the angle between the separatrices, causing magnetic field to pile up or ii) electron vortices generated by enhanced sheared electron outflows, driving electron‐scale Kelvin–Helmholtz instability.

中文翻译：

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靠近电子扩散区的电子尺度磁涨落的起因

在一天的磁层顶穿越过程中，磁层多尺度（MMS）观测到了总磁场中的一系列磁损耗，这主要归因于垂直于磁层顶的成分的波动。这些波动与签名相邻，表明MMS等于或接近（< d _i），是一个磁重连接电子扩散区（EDR）。波动的时间和空间尺度太短，无法影响离子。在本文中，我们调查了这些波动的起因，发现它们可能是由于附近EDR的重新连接速率的时间变化而产生的。实际上，不对称的重新连接电流板和附近区域会受到多种不同的不稳定因素的影响，并且可能会受到波浪和湍流活动的影响。在这里，我们建议磁场的法向分量中的这种振荡可以解释为：i）电子尺度结构，由于流出速度的变化和分离线之间的角度的相应变化而形成，从而导致磁场堆积或ii）增强的剪切电子流产生的电子涡流，