The calculation of moment uncertainties from velocity distribution functions with random errors

Gershman, D. J.; Dorelli, J.; Viñas, A. F.; Pollock, C. J.

doi:10.1002/2014ja020775

Cited by 43 publications

(47 citation statements)

References 30 publications

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“…This is confirmed in Figure as the electron velocity moment deviates from 1.0 earlier than density or temperature. The spin tone, however, is corrected for and removed via ground processing for FPI data, mitigating this problem(Gershman et al, ). The three figures together (Figure ) show that the ion data can be compressed down to about 1,000 bytes while preserving the integrated mean, although the error rises rapidly at this point.…”

Section: Results In Varying Plasma Regimementioning

confidence: 99%

Wavelet Compression Performance of MMS/FPI Plasma Count Data with Plasma Environment

Barrie

Smith

Elkington

et al. 2019

Earth and Space Science

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The Fast Plasma Investigation (Pollock et al., , https://doi.org/10.1007/s11214-016-0245-4; FPI) onboard the Magnetospheric Multiscale mission (Burch, Moore, et al., , https://doi.org/10.1007/s11214-015-0164-9; MMS) uses a discrete wavelet transform and bit plane encoder (DWT/BPE; Winterrowd et al., , https://doi.org/10.1109/AERO.2010.5446664) for data compression. This is the first plasma spectrometer suite to use this method of compression and thus serves as a benchmark for future plasma spectrometers. Flight data from MMS confirm viability of this compression algorithm in large areas of the magnetosphere. Because much of the FPI data were compressed losslessly on orbit, this flight data can be used as seed data to investigate performance of the DWT/BPE‐based compression at increased rates of compression. In this study, data from several representative regions of the magnetosphere have been compressed to increasingly small sizes and the resulting error was analyzed. Wavelet‐based compression is shown to be effective in all regions of the magnetosphere and solar wind for plasma count data, with performance varying with local environment. Specifically, plasma distributions that are characterized by low temperature and/or low density are compressed better leading to excellent performance in plasma regions such as solar wind and the magnetosheath. In general, ion data are compressed better than electron data, primarily due to a higher drift velocity of ions relative to their thermal speed and lower count rates. DWT/BPE compression can therefore be recommended for future instruments measuring count data in Earth's magnetosphere and in solar wind.

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Section: Results In Varying Plasma Regimementioning

confidence: 99%

Wavelet Compression Performance of MMS/FPI Plasma Count Data with Plasma Environment

Barrie

Smith

Elkington

et al. 2019

Earth and Space Science

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show abstract

“…This example thus illustrates the importance of this correction for cold ions as well, with obvious implications regarding the study of magnetic reconnection at Earth's magnetopause when cold plasmapheric ions are entrained into the reconnection line and in turn reduce the reconnection rate [ Borovsky and Denton , ]. This correction is also being implemented for moment calculations on MMS, with the very nice addition of statistical error estimates following the method of Gershman et al [].…”

Section: Discussionmentioning

confidence: 99%

Correcting moments of in situ particle distribution functions for spacecraft electrostatic charging

Lavraud

Larson

2016

JGR Space Physics

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We first introduce previous works on spacecraft electrostatic charging and its effects on particle measurements and the calculation of moments from three‐dimensional distribution functions. We illustrate the fact that the lack of use, or misuse, of Liouville's theorem may lead to misinterpretations and inappropriate corrections to those effects. We emphasize in particular that its appropriate use naturally accounts for what is often called the “sheath focusing effect” in moment calculation. In the case of a “perfect” particle detector we show that there exists a trivial and essentially exact formulation for the calculation of moments of particle distribution functions that accounts for the spacecraft potential and that is particularly useful for onboard moment calculations. The main limitations, but that are not specific to this formulation, are inaccuracies in angle information (from blurring of acceptance angles at low energies or spacecraft‐skimming trajectory effects) and those arising from the detector properties (resolution, cutoffs, photoelectrons, etc.). We discuss this correction in the context of previous works and remind that it primarily affects low‐energy measurements and for populations whose temperature is comparable to the potential. Based on spacecraft observations, we show that this correction is most needed for regimes such as that of solar wind electrons but also for cold ions as often observed, for instance, in the magnetosphere near the Earth's magnetopause.

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“…These uncertainties are based entirely on Poisson statistics, i.e. the counting statistics (Gershman et al 2015a(Gershman et al , 2015b.…”

Section: Fpi Level-2 Data Descriptionmentioning

confidence: 99%

Fast Plasma Investigation for Magnetospheric Multiscale

Pollock¹,

Moore²,

Jacques³

et al. 2016

Space Sci Rev

1,122

1,093

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The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic fieldof-view deflection, the eight spectrometers for each species together provide 4pi-sr field-ofview with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory's Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.

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The calculation of moment uncertainties from velocity distribution functions with random errors

Cited by 43 publications

References 30 publications

Wavelet Compression Performance of MMS/FPI Plasma Count Data with Plasma Environment

Wavelet Compression Performance of MMS/FPI Plasma Count Data with Plasma Environment

Correcting moments of in situ particle distribution functions for spacecraft electrostatic charging

Fast Plasma Investigation for Magnetospheric Multiscale

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