H 2O + Production Rates of Comets Austin 1990 V and P/Halley 1986 III

Abstract

We obtained high-spectral-resolution scans of H 2O + emissions from Comet Austin 1990 V using the Wisconsin dual-etalon Fabry-Perot spectrometer at the McMath-Pierce solar telescope on Kitt Peak. The 10.5 diameter field of view on the sky was centered on the comet head. From the Doppler shifts of the emissions, we determined the outflow velocities of the cometary plasma. Adopting a simple model of the ion distribution within the field of view, we determine a lower limit φ H 2O + to the flux of H 2O + ions away from the nucleus for each night of observations. We apply a similar analysis to our previous observations of H 2O + emissions from Comet P/Halley 1986 III. Comparing φ H 2O + with the water production rate Q H 2O , we find that the average ratio φ H 2O + / Q H 2O is 1.2 × 10 -3 for Comet Halley (solar minimum) and 2.6 × 10 -3 for Comet Austin (solar maximum); these values are significantly smaller than theoretical values of the relative H 2O + production rate Q H 2O+ / Q H 2O .