Secular shift of the auroral ovals: How fast do they actually move?

N. A. Tsyganenko

Abstract:

A surprisingly fast secular drift of the Northern geomagnetic dip pole during the last two decades has attracted much interest lately, in particular, evoking speculations about a possibility of a sweeping relocation of the auroral oval. This letter presents first results of a model investigation of this issue, based on an empirical representation of the distant magnetosphere combined with a series of internal geomagnetic field models for 12 epochs, covering the interval from 1965 through 2020. The secular drift of the Northern auroral oval was found to result in its net displacement over the 55-year period, commensurate with the concurrent shifts of the centered, eccentric, and corrected geomagnetic poles, all of them much smaller than the enormous spurt of the Northern dip pole. In the Southern Hemisphere, the shift of the auroral oval and of the poles over the same period is much weaker, revealing a remarkable interhemispheric asymmetry.

GRL, accepted February 28, published online March 4, 2019;

This work was supported by the Russian Foundation for Basic Research (RFBR) grant 17-05-00415.