Geoscience Reference
In-Depth Information
IEFy at ACE spacecraft
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Comparison of eastward electric fields at equator
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Eastward electric field and
D
H at Jicamarca
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Apr 17, 2002
UT (hrs)
Figure 3.26b
Direct comparison of the IEF and the equatorial electric field (using ISR
and the Anderson technique) after adjusting for the time delay from the ACE satellite
to the magnetopause. In the middle and bottom panels the dark line is the eastward
component over Jicamarca that corresponds to the dawn-to-dusk direction. The light line
in the middle panel is the dawn-to-dusk component of the IEF. In the lower panel the light
line is the predicted eastward field from
H
values. [Adapted from Kelley et al. (2003a).
Reproduced with permission of the American Geophysical Union.]
that vary in time with the wave period. Again, a time delay of many hours is
expected if the gravity wave source is in the auroral zone (see Fig. 3.30a, b and
associated text).
Very clear examples of both instantaneous and delayed equatorial perturba-
tions are illustrated in Fig. 3.28. In the upper two panels, the auroral AU and AL
magnetic fields are plotted for a 48 h period on August 8-10, 1972. Below, the
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