The interplanetary origins and the main-phase development of moderate geomagnetic storms (1978-1979) / A origem interplanetária e o desenvolvimento da fase principal das tempestades geomagnéticas moderadas (1978-1979)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

Geomagnetic storms are related to the ring current, which is driven by energy injection primarily during energetic solar wind-magnetosphere coupling due to reconnection at the magnetopause. This work identified the interplanetary origins of moderate geomagnetic storms (-100 nT < DstMíN < -50 nT) and analysed the coupling processes during the storm main phase. For this purpose the interplanetary magnetic field, solar-wind temperature, density and velocity data, obtained by the ISEE-3 satellite, were used together with the equatorial-Dst and auroral-AE geomagnetic indices, provided by the World Data Center, for the interval August/1978-December/1979. 78 moderate storms were identified, in which 40 storm events (Dst beginning at ~ O nT) were selected. Related to these well defined events the following interplanetary origins were found: coronal mass ejections phenomena - CME (40% related to interplanetary shocks; 22,5% to single streams; 17,5% to streams interactions; 10% to non-compressive density enhancement) and non-CME phenomena (7,5% related to Alfven-like waves and 2,5% to no-identified feature). 47% of CME-phenomena .occurred near the heliospheric current sheet. Regarding the main-phase development all energy coupling functions showed a similar behaviour, that is, the south component of the interplanetary magnetic field (in the magnetospheric coordinate frame) controls basically this coupling. The best linear fits were given by Ey electric field-like and E electric power-like functions. However the complexities in these coupling relations point to other simultaneous energy transfer processes such as non-proportional transference, viscous transference and "unloading" process.

ASSUNTO(S)

tempestades geomagnéticas magnestosfera

ACESSO AO ARTIGO

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