Abstract
Measurements of sodium D-line emission from Io are reported which were made during synoptic patrols of the 1975 and 1974 apparitions. Corrected equivalent widths of the D lines are plotted against the satelliite's orbital phase reckoned from superior heliocentric conjunction, and quantitative results of selected patrol observations are provided. The results indicate that: (1) resonant scattering is most likely the dominant emission mechanism; (2) the mechanism which injects neutral sodium into the space immediately around Io underwent no major secular variation in the period between the two apparitions; (3) a less pronounced asymmetry between the peak emission rates at 90-deg and 270-deg orbital phases is present in the selected data; and (4) the measured D2/D1 intensity ratios are consistent with a value of 1.6 + or - 0.3, which corresponds to a value of the order of unity for the maximum optical depth possible for resonant scattering the D1 line center. It is suggested that an unexplained scatter of about 20% in the general emission levels is due to a variation in the ionization rate.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
