Top items to consider when analyzing FPI Data - the checklist:
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Quality Flags <--
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heed the warnings!
Instrumentation Thresholds vs the target plasma distribution
Significant (>25%) cold plasma (<10eV) component
Significant (>25%) hot plasma (>30keV) component
Quasi-neutrality Check
Comparison of the FPI ion and electron density moments can give some indication as to how much of the underlying plasma distribution is represented in the separate FPI, HPCA, EIS, FEEPS data files.
In v2.0 and greater L2 files, FPI Ne and Ni are generally reliable. Exceptions include:
- periods for which the internally generated DES phototelectrons could not be completely removed;
- periods when the spacecraft potential is very high and the spacecraft potential correction needs individual work; and
- at very low DES densities, when the spurious photoelectron signal is removed, the resulting density value can be obviously nonphysical; do not use caution using the FPI density moments when the corresponding quality flag is 1. (Quality Flag bit 7). <-- this is a known limitation that will be addressed in the next software release.
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Internally generated photoelectons, unaffected by the spacecraft potential in the sun direction produce an effective cold electron component with density ~0.5-1 cm-3 and bulk velocity ~750 km/sec in the anti-sunward direction. This component varies with spacecraft spin phase. A model for this signal has been developed and the signal removed for the moment calculations as of software release v2.0. Please see the separate page for more detailed information. NOTE: These photoelectrons (internal and spacecraft) are not removed from the skymap data product as users need to be aware of this signal for their specific data interval and how its removal might affect analysis and interpretations.
Background Radiation
Error Flag Bit 13: significant (>=20%) penetrating radiation (DIS only)
Spin-periodicities – Velocity Offsets
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