GOES-16 and GOES-17 are the first of NOAA’s Geostationary Operational Environmental Satellite (GOES)-R series of satellites. Each GOES-R satellite has a magnetometer mounted on the end (outboard) and one part-way down a long boom (inboard). This paper demonstrates the relative accuracy and stability of the measurements on a daily and long-term basis. The GOES-16 and GOES-17 magnetic field observations from 2017 to 2020 have been compared to simultaneous magnetic field observations from each other and from the previous GOES-NOP series satellites (GOES-13, GOES-14 and GOES-15). These comparisons provide assessments of relative accuracy and stability. We use a field model to facilitate the inter-satellite comparisons at different longitudes. GOES-16 inboard and outboard magnetometers data suffer daily variations which cannot be explained by natural phenomena. Long-term averaged GOES-16 outboard (OB) data has daily variations of ± 3 nT which are stable within ± 1.5 nT. Long-term averaged GOES-17OB magnetometer data have minimal daily variations (less than ± 1 nT). Daily average of the difference between the GOES-16 outboard or GOES-17 outboard measurements and the measurements made by another GOES satellite are computed. The long-term averaged results show the GOES-16OB and GOES-17OB measurements have long-term stability (± 2 nT or less) and match measurements from magnetometers on other GOES within limits stated herein. The GOES-17OB operational offset (zero field value) was refined using the GOES-17 satellite rotated 180° about the Earth pointing axis (known as a yaw flip).

In this paper, we present a statistical validation of the DSCOVR solar wind data in the operational space weather archive. The DSCOVR observations of the interplanetary magnetic field (IMF), solar wind velocity, density, and temperature were hourly averaged and compared to measurements from NASA’s ACE and Wind spacecraft. Hourly averages, in general, show good correlations between the satellites for the IMF, solar wind velocity GSE vx-component, and density. During the period covered by this study (spanning from late July 2016, when DSCOVR went operational, to the end of 2020), the DSCOVR products show no clear evidence of permanent degradation. However, for plasma parameters there were periods of disagreement with ACE and Wind. The correlation coefficients (Pearson’s r) calculated over the entire study period were similar or the same between DSCOVR versus Wind and DSCOVR versus ACE. For comparisons between DSCOVR and Wind, the IMF Bx and By GSE r were 0.94 and 0.96, respectively, while r for the IMF GSE Bz-component was 0.88. For solar wind velocity, r was found to be 0.96 for the GSE vx-component, compared with 0.30 for vy and 0.33 for vz. For density, r was found to be 0.84. DSCOVR density observations tend to overestimate compared to Wind values when the solar wind densities are low (below ∼5 /cc), while agreement between the two spacecraft on IMF measurements tend to increase with decreasing spatial separation.

Simultaneous bursts of EMIC and longer-period ULF waves were observed by the GOES-16 magnetometer on the 11 January and the 7 September 2017. No correlation was found between the repeat times of EMIC wavepackets and Pc4 ULF wave periods. However, the repetition times visually correlated with variations in solar wind dynamic pressure (Pdyn). EMIC wavepackets are composed of short duration subpackets and when subpackets last >1/2 the ULF wave period, correlation with the ULF wave cycle was strong, R=0.6. On 11 Jan., observations suggest the Pc5 ULF waves were in-part directly driven by Pdyn. The observed Pc4-5 ULF waves were predominately poloidal. Assuming high azimuthal m-numbers, the observations as a whole imply that the simultaneous repeating EMIC and Pc4-5 wave bursts were formed by mode cross-coupling through a common wave generation free energy source of anisotropic ion distributions created by repetitive magnetospheric compressions driven by small Pdyn fluctuations.