A Review of Studies of Geomagnetic Storms and Auroral/Magnetospheric Substorms Based on the Electric Current Approach

The progress of space physics is reviewed from my personal point of view, particularly how I have reached my present understanding of auroral substorms and geomagnetic storms from the time of the earliest days of space physics. This review is somewhat unique in two ways. First of all, instead of taking the magnetic field line approach (including magnetic reconnection), I have taken the electric current approach; it consists of power supply (dynamo), transmission (currents/circuits), and dissipation (auroral/magnetospheric substorms). This is the basic way to study electromagnetic phenomena and it is much more instructive in understanding the physics involved in the chain processes. Secondly, this is not a textbook-like review, but it is hoped that my humble experience may be useful to see how a new science of space physics has evolved with a number of controversies. On the other hand, it can be seen that the electric current approach is still in a very rudiment stage. Thus, new generations of researchers are most welcome in taking this new way of studying auroral/magnetospheric substorms and geomagnetic storms.

Relationship Between Geomagnetic Storms and Auroral/Magnetospheric Substorms: Early Studies

This paper describes a short story of how I learned in early days in space physics (1960–1970) that there are the direct and feed-back relationships between geomagnetic storms and auroral/magnetospheric substorms. In those days, both geomagnetic storms and auroral substorms were almost independent subjects. It is now understood that auroral substorms are directly related to the development of the ring current and thus of the main phase of geomagnetic storms. Further, we have begun to recognize that the growth of the ring current (caused by auroral/magnetospheric substorms) will change the internal structure of the magnetosphere, which in turn will change and could modify at least the intensity of auroral substorms. Thus, there are interesting feed-back processes between them. It is expected that this feed-back relationship between geomagnetic storms and auroral/magnetospheric substorms will become one of the major issues in magnetospheric physics in the future. In fact, an effort to understand this relationship will deepen our understanding of both geomagnetic storms and auroral/magnetospheric substorms. The progress in understanding the relationship between auroral substorms and geomagnetic storms is an example, in which it takes a long time to advance even one step. It is hoped that this paper will serve to learn the background in the development of space physics in the early days.

Analysis of the effects of auroral substorms on the data of ionosphere vertical sounding in the Arctic

The problem of diagnosing and predicting the characteristics of the polar ionosphere can be investigated by studying the effect of magnetospheric disturbances on the high-latitude ionosphere. Our task is to investigate the dependence of the variations in the electron concentration F of the ionosphere region at the subauroral stations of vertical sounding (VS) Sodankyla, Lovozero and Gorkovskaya on variations in the geomagnetic field. The data of AE and PC of geomagnetic indices were used during substorms in the winter of 2011–2012. For analysis, the epoch overlapping method was used. As a result, it was shown that the perturbation in the electromagnetic field is accompanied by a subsequent amplification of variations during the critical frequencies fоF2, and hence the electron concentration, auroral and subauroral ionosphere.We conclude that the geomagnetic indices AE and PC can serve as predictors of disturbances during the ionospheric parameter fоF2 of the high-latitude ionosphere in the winter season.An increase in the amplitude level of AE from 100 to 350 nT (and PC > 2) during the night hours of the winter season precedes an increase in the critical frequencies of the ionosphere F2 layer by an average of 30% of the median. An increase in the amplitude level of AE from 180 to 520 nT (and PC> 2) in the winter season in the afternoon precedes the positive or negative deviation of the critical frequencies of the ionosphere F2 layer from the median by a mean of 10%. The response of the high-latitude ionosphere of the F2 layer to variations in the AE and PC indices appears in the first hour after the maximum during geomagnetic indices, the delay of the maximum deviation from the median 1 hour at night and 3 hours in the afternoon at Lovozero station, at Sodankyla and Gorkovskaya is about 3 hours at night and weakly expressed during the day.I declare I have no competing interests.