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Goetz, C.

Publications and source records attributed to Goetz, C..

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Interplanetary Coronal Mass Ejection Observed at STEREO-A, Mars, Comet 67P/Churyumov-Gerasimenko, Saturn,and New Horizons En Route to Pluto: Comparison of Its Forbush Decreases at 1.4, 3.1, and 9.9 AU

We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44 h before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110-111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116deg, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

Witasse, O.↗
DOE OSTI2017

PLASMA ENVIRONMENT AROUND COMET 67P/CHURYUMOV–GERASIMENKO AT PERIHELION: MODEL COMPARISON WITH ROSETTA DATA

The plasma environment near comet 67P/Churyumov–Gerasimenko (67P/CG) is dynamically affected by various factors, including the incident solar wind and outgassing from the nucleus. The Rosetta spacecraft MAGnetometer (MAG) instrument observations near perihelion showed crossing events into a magnetic field-free region at about 170 km from the nucleus in 2015 July at 1.26 au from the Sun. At each crossing, the magnitude of the magnetic field dropped by more than 20 nT to near zero. We compared the Ion and Electron Sensor (IES) electron differential flux energy spectrum inside and outside the crossing boundaries. The IES observations show a modest but consistent drop in electron flux for energies between 40 eV and a few hundred eV at each cavity crossing event. This drop in the electron spectra might be due to the absence or attenuation of solar wind electrons inside the observed diamagnetic regions, which might or might not be a diamagnetic cavity. There is no apparent simple linear correlation between the electron count rate measured by the IES at different energies and the magnitude of the magnetic field, however; at all energies, the highest electron count rates are recorded at the highest magnetic field magnitudes. From model-data comparisons it seems that inside diamagnetic regions, pure coma photoelectrons are not sufficient to explain the observations and that a trapping mechanism and/or infused solar wind electrons are necessary to explain the observed electron fluxes.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1980

Quartz ball valve

A ball valve particularly suited for use in the handling of highly corrosive fluids is described. It is characterized by a valve housing formed of communicating segments of quartz tubing, a pair of communicating sockets disposed in coaxial alignment with selected segments of tubing for establishing a pair of inlet ports communicating with a common outlet port, a ball formed of quartz material supported for displacement between the sockets and configured to be received alternately thereby, and a valve actuator including a rod attached to the ball for selectively displacing the ball relative to each of the sockets for controlling fluid flow through the inlet ports.

Goetz, C.↗
NASA NTRS1979

Quartz ball value

Quartz ball valve consisting of two quartz joints sealed back-to-back and seated in quartz sockets perform at temperatures of up to 1,250 C and in corrosive chemical environments without contamination or degradation.

Goetz, C.↗