Analysis of an eastward electrojet by means of upward continuation of ground-based magnetometer data

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U. Mersmann
W. Baumjohann
F. Kuppers
K. Lange


On October 26, 1975, data from two parallel meridian chains of densely spaced magnetometers in Northern Scandinavia indicated the presence of an evening sector eastward electrojet which between 1606 and 1710 UT was two-dimensional. By separating the relevant components of the magnetic disturbance fields into internal and external parts, and by subsequent upward continuation (towards the source) of the external horizontal component, equivalent height-integrated ionospheric current densities were derived as a function of latitude and time. Whereas the demarcation line between the eastward and westward ionospheric electrojet currents remained stationary, the sharp southern border of the eastward electrojet moved towards the south with a speed of about 50 ms-1 , possibly indicating an earthward movement of the inner edge of the magnetospheric plasma sheet. The maximum eastward height-integrated current density was of the order of 0.5 Am-1 , the corresponding large-scale field-aligned current density has been estimated to have been of the order of 1.0 μAm-2 . After 1630 UT there was evidence for a superposed stationary small-scale structure (wavelength of the order of 250 km) in the eastward flow, which would imply a pair of local field-aligned current sheets possibly related to an auroral arc.

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Mersmann, U., Baumjohann, W., Kuppers, F., & Lange, K. (1978). Analysis of an eastward electrojet by means of upward continuation of ground-based magnetometer data. Journal of Geophysics, 45(1), 281-298. Retrieved from


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