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Karlheinz J. Trattner

Publications and source records attributed to Karlheinz J. Trattner.

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

The Complexity of the Day-Side X-Line During Southward Interplanetary Magnetic Field

High-resolution global magnetohydrodynamics (MHD) simulations include both meso- and global-scale processes occurring at the magnetopause, which interact to determine the time-dependent orientation of the day-side x-line (DXL). This study demonstrates that the global orientation of the DXL in GAMERA global MHD simulations varies on a time scale of minutes during steady southward interplanetary magnetic field conditions. This behavior manifests in observational data when reconnection outflows indicate that the direction to the x-line is opposite to the prediction from a steady-state model of the reconnection location. Because steady-state models of the DXL do not capture dynamics that are independent of solar wind variations, particularly surface waves and flux transfer events, they represent a time-averaged state of the system.

Brandon Burkholder↗
NASA NTRS2022

Dual Storage and Release of Molecular Oxygen in Comet 67p/Churyumov–Gerasimenko

One of the biggest surprises of the Rosetta mission was the detection of O2 in the coma of 67P/Churyumov–Gerasimenko in remarkably high abundances. The measured levels of O2 in the coma are generally assumed to reflect the overall abundance and chemical origin of cometary O2 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 O2 are linked to H2O. We analysed ROSINA observations and found a previously unrecognized change in the correlations of O2 with H2O, CO2 and CO that contradicts the prevailing notion that the release of O2 is linked to H2O at all times. These findings can be explained by the presence of two distinct reservoirs of O2: 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 O2 must have been incorporated into the nucleus in a solid and distinct phase during accretion in significantly lower abundances than previously assumed.

Adrienn Luspay-kuti↗
NASA NTRS2019

Comparison of Neutral Outgassing of Comet 67P/Churyumov-Gerasimenko Inbound and Outbound Beyond 3 Au From ROSINA/DFMS

Context. Pre-equinox measurements of comet 67P/Churyumov-Gerasimenko with the mass spectrometer ROSINA/DFMS on board the Rosetta spacecraft revealed a strongly heterogeneous coma. The abundances of major and various minor volatile species were found to depend on the latitude and longitude of the nadir point of the spacecraft. The observed time variability of coma species remained consistent for about three months up to equinox. The chemical variability could be generally interpreted in terms of surface temperature and seasonal effects superposed on some kind of chemical heterogeneity of the nucleus. Aims. We compare here pre-equinox (inbound) ROSINA/DFMS measurements from 2014 to measurements taken after the outbound equinox in 2016, both at heliocentric distances larger than 3 AU. For a direct comparison we limit our observations to the southern hemisphere. Methods. We report the similarities and differences in the concentrations and time variability of neutral species under similar insolation conditions (heliocentric distance and season) pre- and post-equinox, and interpret them in light of the previously published observations. In addition, we extend both the pre- and post-equinox analysis by comparing species concentrations with a mixture of CO2 and H2O. Results. Our results show significant changes in the abundances of neutral species in the coma from pre- to post-equinox that are indicative of seasonally driven nucleus heterogeneity. Conclusions. The observed pre- and post-equinox patterns can generally be explained by the strong erosion in the southern hemisphere that moves volatile-rich layers near the surface.

comets↗