World-wide changes in the geomagnetic field

Abstract

It is found that world‐wide changes in the geomagnetic field are not limited to ssc or si and are frequently observed. Not only an increase but also a decrease in horizontal intensity occurs on a world‐wide scale. The form of the change varies, depending both on local time and on latitude. The distribution of the magnitude, and the mode of propagation over the earth, of this phenomenon are studied, and they are found to show a pronounced similarity to those of ssc and si. This finding is consistent with the idea that there is a permanent interaction between the solar corpuscular stream and the geomagnetic field.

Sudden impulses at geosynchronous orbit and at ground

“…For previous reviews of the experimental and theoretical aspects of SI events the reader is referred to Matsushita (1962), Nishida and Jacobs (1962), Siscoe et al (1968), Nishida (1978), Smith et al (1986), Araki (1994), Tsunomura (1998). The aspects of the magnetospheric field representation T04 in terms of contributions from different current systems are extensively discussed in Tsyganenko and Sitnov (2005).…”

IMF-By dependence of transient ionospheric flow perturbation associated with sudden impulses: SuperDARN observations

“…Such geomagnetic variations are caused mainly by interplanetary shocks and tangential discontinuities propagating in the solar wind (Chao and Lepping 1974). Both stepwise increases and decreases of the geomagnetic field are often observed globally (Nishida and Jacobs 1962a;Nishida and Jacobs 1962b) and are referred to as positive sudden impulses (positive SIs) and negative sudden impulses (negative SIs), respectively. They are thought to correspond to global compressions or expansions of the magnetosphere induced by abrupt changes in the solar wind dynamic pressure (P SW ) (Wilken et al 1982;Tsurutani et al 1995).…”

Sudden Impulses in the Magnetosphere and at Ground

“…Additional contributions also come from the effects of the tail current (mostly in the nightside sector) and from those of the ring current (during more active magnetospheric conditions). The further development of field aligned currents (FAC) and ionospheric currents typically makes the SI manifestation at ground much more complex than in the magnetosphere: on the other hand, since earliest investigations (Matsushita, 1962;Nishida and Jacobs, 1962), it is well known that different transient waveforms are detected at different ground stations. Given their global simultaneous occurrence and clear onset time, SI provide a good opportunity for understanding the transient response of the magnetosphere and ionosphere to the SW variations.…”

“…For previous reviews of the experimental and theoretical aspects of SI events the reader is referred to Matsushita (1962), Nishida and Jacobs (1962), Siscoe et al (1968), Nishida (1978), Smith et al (1986), Araki (1994), Tsunomura (1998).…”