HR: 0800h
AN: GP31A-0064    [Abstracts]
TI: The Response of the Geomagnetic Indices to the Variation of the Interplanetary Magnetic Field
AU: Park, Y
EM: yoonkyungpark@hanmail.net
AF: Kyungpook National University, 1370 Sankyuk-Dong, Buk-Gu, Daegu, 702-701 Korea, Republic of
AU: Moon, G
EM: gafemoon@hanmail.net
AF: Kyungpook National University, 1370 Sankyuk-Dong, Buk-Gu, Daegu, 702-701 Korea, Republic of
AU: * Ahn, B
EM: bhahn@knu.ac.kr
AF: Kyungpook National University, 1370 Sankyuk-Dong, Buk-Gu, Daegu, 702-701 Korea, Republic of
AB: An attempt is made to show how the geomagnetic indices, AU, AL and Dst, respond to the variation of the interplanetary magnetic field, more specifically, VBz. It is noted that the AL index shows a significantly high correlation with the VBz on an hourly basis. Considering that the auroral electrojet is the combined result of electric field and ionospheric conductivity enhancements, the intensification of these two quantities seem to occur concurrently on an hourly time scale as the interplanetary magnetic field turns southward. Thus, it is suggested that the AL index behaves more like a convection index rather than a substorm index. Contrary to general belief, the AU index does not seem to respond linearly to the IMF except during the summer season. The AU shows the maximum during summer while the AL shows it during winter for a given level of southward IMF. The solar EUV radiation during the summer season should be higher, thus enhancing the ionospheric conductivity. This is the reason why the AU shows the maximum during summer. On the other hand, the smaller AL value during summer could be explained by the fact that discrete aurorae are suppressed in sunlight (Newell et al., 1996), thus reducing the ionospheric conductivity. The relationship between the Dst index and the VBz is also examined. The Dst index shows a wide range of distribution for a given level of the VBz. As expected, it tends to become more negative, as the VBz gets intensified. The smallest possible magnetic storm in terms of the Dst for a given level of the VBz is given by approximately Dst(nT) ~ 15 VBz (mV/m) + 50. The significant scatter of the Dst index for a given level of the VBz suggests, however, that there is another factor contributing to the development of magnetic storms other than the convection, possibly magnetospheric substorms.
DE: 2134 Interplanetary magnetic fields
DE: 2407 Auroral ionosphere (2704)
DE: 2712 Electric fields (2411)
DE: 2721 Field-aligned currents and current systems (2409)
DE: 2788 Magnetic storms and substorms (7954)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005