The Global Positioning System constellation as a space weather monitor: Comparison of electron measurements with Van Allen Probes data

Morley, S.; Sullivan, J. P.; Henderson, M. G.; Blake, J. B.; Baker, D. N.

doi:10.1002/2015sw001339

Cited by 56 publications

(122 citation statements)

References 70 publications

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“…Clearly, with the broader swath of data from 4.2 ≲L ≲ 7.0, one can observe a vast array of outer belt properties including many flux enhancement events and electron losses that only are hinted at in Figure a. (Using L = 4.2 as the cutoff in Figure b was chosen to correspond to the L range that regularly is explored by the Global Positioning Satellite system that carries Los Alamos National Laboratory particle dosimeter detectors (Morley et al, ) on board many of the operational constellation's satellites). While sampling at L ≳ 4.2 reveals much more of the “iceberg” than seen in Figure a, there are many features at the core of the outer zone (3≲ L ≲4.5) that are not well discerned in the partial outer belt view afforded in Figure b.…”

Section: Data Sources and Analysis Methodsmentioning

confidence: 99%

Comparison of Van Allen Probes Energetic Electron Data With Corresponding GOES‐15 Measurements: 2012–2018

Baker

Zhao

et al. 2019

JGR Space Physics

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Electron fluxes (especially at energies E > 0.8 and 2 MeV) have been measured for many years by sensors on board the Geostationary Operational Environmental Satellite (GOES). These long-term data (nominally at L~6.6) have become a mainstay for monitoring the Earth's radiation environment. We have carried out a study directly comparing the comprehensive radiation belt particle measurements from the National Aeronautics and Space Administration dual-spacecraft Van Allen Probes (Radiation Belt Storm Probes) sensor systems with selected GOES operational data. The Van Allen Probes have measured the properties of radiation belt electrons virtually continuously from September 2012 to 2018. We make statistical comparisons of Van Allen Probes electron data near L = 6 with concurrent daily averages of equivalent GOES-15 flux values. We also compare Van Allen Probes data at various other L values and at a much broader range of particle energies with the more limited baseline GOES-15 values. These comparisons inform us about the relative calibrations between the scientific and operational systems and also allow us to assess how well GOES data correlate with radiation belt behavior well away from the geostationary orbit location. We find that GOES daily average flux values can be a factor of 100 (or more) below the corresponding Van Allen Probes daily averaged fluxes at L = 6.0. This is due to the fact that GOES at stationary orbit often has excursions over large ranges of L space during a given day and strong radial gradients exist in this region of the magnetosphere. These results indicate that it is crucial to augment geosynchronous GOES observations with observations in the core of the outer belt (L ≲5.0).

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Section: Data Sources and Analysis Methodsmentioning

confidence: 99%

Comparison of Van Allen Probes Energetic Electron Data With Corresponding GOES‐15 Measurements: 2012–2018

Baker

Zhao

et al. 2019

JGR Space Physics

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“…The fluxes calculated by using different methods or from different satellites are compared by calculating the quartiles ( Q 1 , Q 2 , and Q 3 ) of the flux ratios [ Morley et al ., ] at fixed energies:

n normalt normalh quartile = Q_{n} ((), \frac{x_{A}}{x_{B}})

where n = 1, 2, or 3 corresponding to 25%, 50%, and 75%; x is the differential flux at some energy or the integral flux above some energy; and “A” and “B” indicate different satellites or different products of the same inputs.…”

Section: Methods For Calculation Of Integral Fluxmentioning

confidence: 99%

Validation of the effect of cross‐calibrated GOES solar proton effective energies on derived integral fluxes by comparison with STEREO observations

et al. 2017

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The derivation of integral fluxes from instrument coincidence rates requires accurate knowledge of their effective energies. Recent cross calibrations of GOES with the high‐energy‐resolution Interplanetary Monitoring Platform (IMP) 8 Goddard Medium Energy Experiment (GME) (Sandberg et al., Geophys. Res. Lett, 41, 4435, 2014a) gave significantly lower effective energies than those currently used by the NOAA Space Weather Prediction Center to calculate solar proton integral fluxes from GOES rates. This implies systematically lower integral fluxes than currently produced. This paper quantifies the differences between the current and the cross‐calibrated GOES integral fluxes and validates the latter. Care is taken to rule out the spectral resolution of the measurements or different integration algorithms as major contributors to differences in the magnitudes of the derived integral fluxes. The lower effective energies are validated by comparison with the independent, high‐resolution observations by the STEREO Low‐Energy Telescope (LET) and High‐Energy Telescope (HET) during the December 2006 solar proton events. The current GOES product is similar to the >10 MeV integral fluxes recalculated by using the Sandberg et al. [] effective energies but is substantially greater at higher energies. (The median ratios of the current to the recalculated fluxes are 1.1 at >10 MeV, 1.7 at >30 MeV, 2.1 at >60 MeV, and 2.9 at >100 MeV.) By virtue of this validation, the cross‐calibrated GOES integral fluxes should be considered more accurate than the current NOAA product. The results of this study also demonstrate good consistency between the two long‐term IMP 8 GME and STEREO LET and HET solar proton data sets.

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“…GPS satellites have near‐circular orbits at an altitude of 20,200 km, with a 12‐hr period and an inclination of 55 ∘ . They are equipped with a Combined X‐ray Dosimeter measuring electron fluxes in 11 successive energy channels over ∼0.14–6 MeV, the final fluxes being recalculated using a sophisticated spectrum fitting procedure after proper subtraction of proton counts (e.g., see Morley et al, , and references therein). We shall first examine separately the occurrence of flux enhancement as a function of different indices in section 2 and then use in section 3 superposed epoch analyses to reveal the most pertinent parameters in the hours leading to flux increases.…”

Section: Introductionmentioning

confidence: 99%

Electron Flux Enhancements at L = 4.2 Observed by Global Positioning System Satellites: Relationship With Solar Wind and Geomagnetic Activity

et al. 2018

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Determining solar wind and geomagnetic activity parameters most favorable to strong electron flux enhancements is an important step toward forecasting radiation belt dynamics. Using electron flux measurements from Global Positioning System satellites at L = 4.2 in 2009–2016, we seek statistical relationships between flux enhancements at different energies and solar wind dynamic pressure Pdyn, AE, and Kp, from hundreds of events inside and outside the plasmasphere. Most ≥1‐MeV electron flux enhancements occur during nonstorm (or weak storm) times. Flux enhancements of 4‐MeV electrons outside the plasmasphere occur during periods of low Pdyn and high AE. We perform superposed epoch analyses of Global Positioning System electron fluxes, along with solar wind and geomagnetic indices, 40‐keV electron flux, ultralow frequency (ULF) wave index from Geostationary Operational Environmental Satellite, and chorus wave intensity from the Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms mission. We demonstrate that 4‐MeV electron flux enhancements outside the plasmasphere start when the interplanetary magnetic field (Bz) reaches a minimum and develop during periods of low Pdyn, high AE, low but increasing Dst, moderate ULF wave index, and intense chorus waves. Flux enhancements at 100 keV occur under conditions with higher Pdyn, higher ULF wave index, and elevated 40‐keV electron flux at L = 6.6. Moreover, electron flux enhancements take much more time to develop at higher energies. This suggests that 100‐keV flux enhancements are dominated by injections, while MeV electron energization is predominantly induced by chorus waves with further amplification by inward transport.

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The Global Positioning System constellation as a space weather monitor: Comparison of electron measurements with Van Allen Probes data

Cited by 56 publications

References 70 publications

Comparison of Van Allen Probes Energetic Electron Data With Corresponding GOES‐15 Measurements: 2012–2018

Comparison of Van Allen Probes Energetic Electron Data With Corresponding GOES‐15 Measurements: 2012–2018

Validation of the effect of cross‐calibrated GOES solar proton effective energies on derived integral fluxes by comparison with STEREO observations

Electron Flux Enhancements at L = 4.2 Observed by Global Positioning System Satellites: Relationship With Solar Wind and Geomagnetic Activity

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