Abstract
AbstractFollowing the end of the Van Allen Probes mission, the Arase satellite offers a unique opportunity to continue in‐situ radiation belt and ring current particle measurements into the next solar cycle. In this study we compare spin‐averaged flux measurements from the MEPe, HEP‐L, HEP‐H, and XEP‐SSD instruments on Arase with those from the MagEIS and REPT instruments on the Van Allen Probes, calculating Pearson correlation coefficient and the mean ratio of fluxes at L* conjunctions between the spacecraft. Arase and Van Allen Probes measurements show a close agreement over a wide range of energies, observing a similar general evolution of electron flux, as well as average, peak, and minimum values. Measurements from the two missions agree especially well in the 3.6 = L* ≤ 4.4 range where Arase samples similar magnetic latitudes to Van Allen Probes. Arase tends to record higher flux for energies <670 keV with longer decay times after flux enhancements, particularly for L* < 3.6. Conversely, for energies >1.4 MeV, Arase flux measurements are generally lower than those of Van Allen Probes, especially for L* > 4.4. The correlation coefficient values show that the >1.4 MeV flux from both missions are well correlated, indicating a similar general evolution, although flux magnitudes differ. We perform a preliminary intercalibration between the two missions using the mean ratio of the fluxes as an energy‐ and L*‐ dependent intercalibration factor. The intercalibration factor improves agreement between the fluxes in the 0.58–1 MeV range.
Highlights
Following the discovery of Earth's Van Allen belts, numerous spacecraft have been launched to supply ongoing scientific investigation of the radiation belts with appropriate data (Li & Hudson, 2019)
We compared fluxes from Arase and RBSP at similar energies binned by L* and calculated the Pearson correlation coefficient for the energies and L* studied
We used the mean ratio between Arase and RBSP fluxes at the same L* and energy to improve agreement between Arase and RBSP fluxes, and assessed the performance of this intercalibration
Summary
Following the discovery of Earth's Van Allen belts, numerous spacecraft have been launched to supply ongoing scientific investigation of the radiation belts with appropriate data (Li & Hudson, 2019). This opens up the possibility of direct comparisons between Arase and other long-term missions in Earth's radiation belts and ring current at higher L, such as the Geostationary Operational Environmental Satellites (GOES: Davis, 2007), the Los Alamos National Laboratory geostationary satellites (LANL-GEO/GEO: Reeves et al, 1997), and the recently. The L coverage of Arase enables the data set to be used in a similar manner, for example, between the RBSP and GOES missions that have very few L* conjunctions due to RBSP being generally near the equator in an orbit that has its apogee inside the geostationary orbit (Baker et al, 2019) This principle can be extended to interplanetary missions on a heliospheric scale, as demonstrated in Roussos et al (2020). On-orbit statistical comparisons of spin-averaged data are be used to intercalibrate Arase to a wide range of satellite missions, and are a suitable a topic for future studies
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