Geoscience Reference
In-Depth Information
18-19 January 1984
500
AU
0
AL
2
500
10
IMF
Bz
0
210
Jicamarca
1
0
21
00
08
16
00
UT
08
16
00
Figure 3.22 Auroral zone and interplanetarymagnetic field data alongwith zonal electric
field measurements over Jicamarca, Peru, for a 48 h period. Local midnight occurs at 5 UT
at Jicamarca. [After Fejer et al. (1990). Reproduced with permission of Terra Scientific
Publishing Co.]
a number of data gaps. One of these data gaps occurred during the first isolated
substorm, and we ignore this period for the moment. The IMF turned southward
at 1700 UT on January 18 and remained southward until about 0100 UT on
January 19. During this time two substorms occurred in the auroral oval. At
Jicamarca, which was in the postnoon sector, the period 1900-2300 UT was
characterized by a westward perturbation from the quiet-time field. This period
corresponds to the time between the two substorms. The period 0700-1200UT
on January 19 also fell between two substorms but was characterized by an east-
ward perturbation of the Jicamarca electric field measurement (postmidnight
sector). Notice that there was almost exactly 12 h between these events, which
means that the Jicamarca data were taken on the opposite side of the system
when viewed in a magnetospheric or solar wind reference frame. The burst of
eastward perturbation field at 1000-1200 UT on January 18 is now seen to be
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