Impulse response of geomagnetic indices to interplanetary magnetic field.

Abstract

The impulse response of the geomagnetic indices (Dst, AL, AU and AE) to the interplanetary magnetic field southward component (IMF Bz) is calculated on the assumption that the magnetosphere acts as a linear system. Hourly data for 300 days are used in this analysis. The main results obtained are as follows: (1) Using interplanetary data, a fairly large portion of geomagnetic disturbances may be predicted with the assumption of a linear system. (2) The response of the Dst index and the AL index develops at two steps or has an oscillating property with a period of several hours. (3) The response of the AU index is rather different from that of the other indices. These results may suggest that the disturbances represented by the Dst and AL indices have a common origin associated with the interplanetary magnetic or electric field, whereas those indicated by the AU index have an origin somewhat different from it.

Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field

“…This time scale was also found in studies correlating the geomagnetic AL index with the solar wind motional electric field vB s (Iyemori et al, 1979;Bargatze et al, 1985;Blanchard and McPherron, 1995), where v is the solar wind velocity, and B s = −B z for southward IMF and is, otherwise, zero. A second characteristic time scale with approximately a 60 min delay emerged from these studies as well, which was suggested as the delayed unloading response of the geomagnetic tail.…”

Solar Wind-Magnetosphere Interaction during the Possible Encounter of Comet Halley's Tail in 1910 Inferred from Mid-Latitude Geomagnetic Field Disturbances.

“…The peak of it is at zero time lag. The efficiency, of prediction (see IYEMORI et al, 1979) is 0.57 for H-asymmetry and 0.55 for D-asymmetry in this case. The period when the encounter is expected is shown by a box with thick line.…”

“…To separate the compressional effect from the ring current effect in the symmetric part, we applied a linear prediction filter technique (IYEMORI et al, 1979;IYEMORI and MAEDA, 1980;MCPHERRON et al, 1986). That is, we calculated an impulse response function of the symmetric part (Dst) to the asymmetric part by using the data from April to June, 1910.…”

Fractal Analysis of InterMagnet Observatories Data

“…Several techniques have been applied for prediction of geomagnetic disturbances. We cite, for example, the technique of neural networks for prediction of magnetic storms (Iyemori et al, 1979; Kamide et al, 1998;Gleisner et al, 1996).…”