Multi-Spacecraft Observations of Fluctuations Occurring Along the Dusk Flank Magnetopause, and Testing the Connection to an Observed Ionospheric Bead

During 2018 November 06, 11:30—18:00 UT, the MMS constellation, the Cluster set of spacecraft, and the Geotail spacecraft were all situated near the dusk flank magnetopause. Large scale fluctuations were observed by the available and operating science instruments at these various spacecraft (i.e., magnetic field, plasma moment, and energy flux measurements). Similar fluctuations were not observed by upstream solar wind monitors, suggesting that the waves were initiated at the magnetopause. A localized emission ‘bead’ from the post-noon ionosphere was also observed from low Earth orbit. The nature and relation of the fluctuations observed at all of these spacecraft at the magnetosphere boundary and the connection to the post-noon high-latitude ionosphere are investigated in this study

Dual storage and release of molecular oxygen in comet 67P/Churyumov-Gerasimenko

All data processed as described above are included in the Article and Supplementary Information. The ROSINA/DFMS spectra used to derive count rates are available in the NASA Planetary DataSystem (https://pds-smallbodies.astro.umd.edu/data_sb/missions/rosetta/index.shtml) and ESA Planetary Science Archive (https://archives.esac.esa.int/psa/#!Table%20View/Rosetta=mission). Source data are provided with this paper.International audienceOne of the biggest surprises of the Rosetta mission was the detection of O-2 in the coma of 67P/Churyumov-Gerasimenko in remarkably high abundances. The measured levels of O-2 in the coma are generally assumed to reflect the overall abundance and chemical origin of cometary O-2 in the nucleus. Along with its strong association with H2O and weak association with CO and CO2, these measurements led to the consensus that the source and release of cometary O-2 are linked to H2O. We analysed ROSINA observations and found a previously unrecognized change in the correlations of O-2 with H2O, CO2 and CO that contradicts the prevailing notion that the release of O-2 is linked to H2O at all times. These findings can be explained by the presence of two distinct reservoirs of O-2: a pristine source in the deeper nucleus layers dating back to before nucleus formation, and an H2O-trapped secondary reservoir formed during the thermal evolution of the nucleus. These results imply that O-2 must have been incorporated into the nucleus in a solid and distinct phase during accretion in significantly lower abundances than previously assumed. Seasonal changes in the correlation between O-2 and H2O in comet 67P's coma are indicative of two reservoirs of molecular oxygen in the nucleus, a deeper primordial one and a surficial one, suggesting that the observed high abundance of O-2 and its association with H2O are not reflective of the original accretion source