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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Polar rain gradients and field-aligned polar cap potentials
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Polar rain gradients and field-aligned polar cap potentials

机译：极地雨梯度和field-aligned极地冰冠势

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ACE SWEPAM measurements of solar wind field-aligned electrons have been compared with simultaneous measurements of polar rain electrons precipitating over the polar cap and detected by DMSP spacecraft. Such comparisons allow investigation of cross-polar-cap gradients in the intensity of otherwise-steady polar rain. The generally good agreement of the distribution functions, f, from the two data sources confirms that direct entry of solar electrons along open field lines is indeed the cause of polar rain. The agreement between the data sets is typically best on the side of the polar cap with most intense polar rain but the DMSP f's in less intense regions can be brought into agreement with ACE measurements by shifting all energies by a fixed amounts that range from tens to several hundred eV. In most cases these shifts are positive which implies that field-aligned potentials of these amounts exist on polar cap field lines which tend to retard the entry of electrons and produce the observed gradients. These retarding potentials undoubtedly appear in order to prevent the entry of low-energy electrons and maintain charge quasi-neutrality that would otherwise be violated since most tailward flowing magnetosheath ions are unable to follow polar rain electrons down to the polar cap. In more limited regions near the boundary of the polar cap there is sometimes evidence for field-aligned potentials of the opposite sign that accelerate polar rain electrons. A solar electron burst is also studied and it is concluded that electrons from such bursts can enter the magnetotail and precipitate in the same manner as polar rain.
机译：ACE SWEPAM测量太阳风field-aligned电子相比同时测量极地雨电子沉淀在极地冰冠和探测到DMSP飞船。调查的cross-polar-cap梯度otherwise-steady极性强度降雨。一般的好协议分布两个数据源的功能,f,证实直接入口的太阳能电子沿着开放电场线的确是极地下雨的原因。数据集通常之间的协议最好的极冠多数强烈的极地雨少但DMSP f强烈的地区可以带进协议与ACE测量所有能量转移一个固定的数额,从十几个电动汽车。积极的这意味着field-aligned这些大量存在于极地冰冠的潜力电场线往往会阻碍的进入电子和观察到的梯度。毫无疑问出现在这些缓势为防止低能的条目电子和维持电荷准中立,否则将违反了因为大多数tailward磁鞘离子无法流动遵循极地雨电子极地帽。更多的有限区域的边界附近那里的极冠有时是证据field-aligned势相反的信号加速极地雨电子。电子破裂也研究它从这样的爆发可以得出结论,电子在相同的输入磁尾和沉淀极地雨。

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