Sheet / PSBL
Caution level: ExtremeThis
is the most difficult region for double-probe electric field experiments.
It is not clear whether the EFW DC electric field data is ever "good"
(in ths sense that it agrees with EDI or CIS).
The magnetic field is often in
the spin plane, and the plasma is very cold and tenuous. Electrostatic
wakes are a serious problem due to cold
ion temperatures and higher flow velocities.
|Frequency of Occurence
|Ease of detection
|Data Loss Severity
|Wide electrostatic wake
Examples of good EFW data in the lobes
period from July to October, 2001 was examined. Periods where Cluster
was clearly in the lobes were identified from the quicklook plots (main criteria
was the absense of ions). All such periods where EDI had "good" data
were compared to EFW. No period showed convincing agreement between
EDI and EFW.
It is clearly possible that "good" periods exist. If you know of such an interval, please contact the PI team.
Problem: Wide Electrostatic Wakes.
|Examples of the problem
|2001-10-10 1100 C3
This example shows large DC fields not seen by EDI or CIS. The data is still sinusoidal over the spin.
Description of the plotted quantities.
2001-08-01 2110 C3
This example shows how ASPOC reduces the spurious fields seen in the lobes.
Even after ASPOC turns on, however, ageement is still poor.
2001-09-22 1000 C3
This example shows a large disagreement between EFW and CIS/EDI (which agree
well; note that the line giving EDI Ex is almost completely obscured by the
CIS data) over 2 hours.
|Description of the problem
|The data shows major differences when compared to EDI or CIS.
|How can it be detected?
can only be detected by comparisons with EDI or CIS data. Unfortunately,
both of these instruments also encounter difficulties in the lobes.
|How can it be corrected?
|It seems unlikely that this can be corrected.
|Why does it occur?
|It seems likely that this is related
to the electrostatic wakes seen in the polar cap region. However, the
data is still sinusoidal; no wake can be seen. It is believed that
this is because the booms remain inside the wake at all times.
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last modified on 28-Nov-2002