* Magnetic Cloud Characteristics:
Sep 98 and Oct 98: Axes of flux rope highly inclined to the
ecliptic plane for both events. Sep 98 event successfully fit
to a S-N magnetic flux rope model by the WIND MFI team. Southward
Bz in the magnetic clouds for these events was comparable in both
magnitude and duration. However the Dst min for Sep 98 was ~-233
nT and that for the Oct 98 event was ~-139 nT. The difference
in the geoeffectiveness may be partially related to the large
differences in solar wind velocity for the two clouds.
* Shock Structures:
* Oct 98: traveled at ~400 km/s and was preceded by only a weak
shock
* Magnetosphere-Ionosphere Responses:
* A magnetic storm with minimum Dst of -139 nT occurred but with
an extremely long recovery phase.
* Highest solar wind density and dynamic pressure of the three
events. Magnetosheath encounter by the LANL geosynchronous spacecraft
near 4 UT on 19 Oct 98.
* Solar wind speeds following the IMC increased from 400 km/s
in the magnetic cloud to 600 km/s behind the cloud, possibly in
a high-speed stream. The IMF Bz was small following the magnetic
cloud and fluctuated from north to south repeatedly preventing
the Dst from recovering to pre-storm values.