白克兰电流是沿着联结地球磁层的磁场线流进地球高纬度电离层的一股电流。在地球的磁层，这股电流由太阳风和行星际磁场以及体积庞大的电浆驱动着（由行星际磁场间接的驱动着它们的对流）。白克兰电流的强度与磁层中的活动一起变化（例如在副暴期间）。在朝上的电流片（电子向下流动）中小尺度的扰动加速磁层中的电子，当它们抵达大气层的上层，就会创造出极光（南极光和北极光）。在高纬度的点离层（或极光带），白克兰电流经由在该区电离层垂直于磁场线的极光电喷接通。两对白克兰电流在场匹配电流片中成对的出现，一对由正午处通过黄昏侧延伸到子夜处，另一对从正午区经由黎明侧也延伸到子夜区。在极光带高纬度这一侧的电流片称为第一区，低纬度那一侧的电流片称为第二区。

A Birkeland current is a set of currents that flow along geomagnetic field lines connecting the Earth’s magnetosphere to the Earth's high latitude ionosphere. In the Earth’s magnetosphere, the currents are driven by the solar wind and interplanetary magnetic field and by bulk motions of plasma through the magnetosphere (convection indirectly driven by the interplanetary environment). The strength of the Birkeland currents changes with activity in the magnetosphere (e.g. during substorms). Small scale variations in the upward current sheets (downward flowing electrons) accelerate magnetospheric electrons which, when they reach the upper atmosphere, create the Auroras Borealis and Australis. In the high latitude ionosphere (or auroral zones), the Birkeland currents close through the region of the auroral electrojet, which flows perpendicular to the local magnetic field in the ionosphere. The Birkeland currents occur in two pairs of field-aligned current sheets. One pair extends from noon through the dusk sector to the midnight sector. The other pair extends from noon through the dawn sector to the midnight sector. The sheet on the high latitude side of the auroral zone is referred to as the Region 1 current sheet and the sheet on the low latitude side is referred to as the Region 2 current sheet.