Spacecraft Potential
Cluster spacecraft potential in IDFS
"EFW Potential" is actually the probe-spacecraft potential, measuring the potential difference along the wire booms. There is typically a "contact potential" difference between the boon tip and the adjacent plasma, and also there may be a potential difference between the more distance plasma and the plasma at the boom tip. In dense plasmas (solar wind, magnetosheath) it may be sufficient to add 1V to the EFW potential to find the true spacecraft potential. In more rarefied plasmas, a further correction may be needed. See for example Cully et al., JGR, doi:10.1029/2007JA012269, 2007.
There are several virtuals representing Cluster spacecraft potential in IDFS:
EFW probe-spacecraft potential at 4 sec (spin averaged) resolution, produced for the Cluster Active Archive (CAA) by the EFW PI team at IRFU, Sweden. These should be regarded as definitive, but as with CSDS, may show data gaps where poor quality data has been removed. CAA quality flags are not carried across to IDFS (tbc).
Best for science (but not "true spacecraft potential" as noted above).
EFW probe-spacecraft potential at 0.2 sec high time resolution, produced for the Cluster Active Archive (CAA) by the EFW PI team at IRFU, Sweden. These should be regarded as definitive, but as with CSDS, may show data gaps where poor quality data has been removed. CAA quality flags are not carried across to IDFS (tbc)
Best for science (but not "true spacecraft potential" as noted above).
EFW probe-spacecraft potential at 4 sec resolution from the Cluster Science Data System (CSDS) Prime Parameters, produced by the EFW PI team at IRFU, Sweden. If the EFW team are not confident about the potential data, they remove it leaving a data gap. This might happen for example if the probe bias settings are incorrect.
Now generally superceded by CAA data, see below
EFW probe-spacecraft potential at 4 sec (spin averaged) resolution, produced by the EFW CoI team at UCB, USA. Less care is taken over validation of these data, so they are usually available before other sources, but they should be treated with caution due to the lack of validation.
Only for preliminary studies if nothing else is available.
(True) spacecraft potential estimated by an algorithm which analyses PEACE energy spectra, operating onboard in the PEACE DPU. The data is transmitted as part of the PEACE CORE data. This has not been examined in detail but is not expecte dto be reliable in all plasma environments.
Not recommended for science at the time of writing.
(True) spacecraft potential estimated by algorithms which analyse PEACE energy spectra, during ground analysis of transmitted PEACE distributions. Studies by Lin Gilbert, Andrew Lahiff and Branislav Mihaljcic (with Andrew Fazakerley) may have contributed data here at various times, but any data should be regarded as experimental, and at the time of writing only a few tens of ntervals are in the IDFS database.
Not recommended for science at the time of writing.
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By I. Rozum and Andrew Fazakerley
Last updated on
03-Aug-2010
by Andrew
Fazakerley