Date of Award
Thesis - Open Access
Master of Science in Engineering Physics
Dr. Edwin J. Mierkiewicz
First Committee Member
Dr. Theodore von Hippel
Second Committee Member
Dr. Bereket Berhane
I apply high resolution spectroscopy to investigate the lunar exosphere by measuring sodium and potassium spectral line profiles to determine spatial and temporal variations in exospheric effective temperatures and velocities. Observations were made from the National Solar Observatory (MMP) at Kitt Peak, Arizona from November 2013 to May 2014, with the exception of March 2014. Data collection was centered of full moon and spanned several nights with lunar phase angle coverage ranging from 65.6° (waxing) to 78.7° (waning). Observations were concurrent with the NASA LADEE mission science and instrument testing phases. We used a dial etalon Fabry-Perot spectrometer with a resolving power of 180,000 (1.7 km s-1) to measure the line widths and radial velocity shifts to the sodium D2 (5889.9506 Å) and potassium D1 (7698.9646 Å) emission lines. The instrument's three arcmin field of view (~336 km) was positioned at several locations off the lunar limb in each of the four cardinal directions. Only data taken up to 28 seconds in time are presented ad discussed in this thesis.
The sodium line widths were mostly symmetric for both waxing and waning phase angles, with line widths being approximately constant at phase angles larger than 40°. The line widths, and thus line width derived effective temperatures, were largest during magnetotial passage (phase angle 0 - 40°). The line widths outside of the magnetotial (phase angle > 40°) were 1.5 -2.0km s-1 (~ 1100 - 1500 K) while the line widths during full Moon (phase angle ~ 6°) increased to ~ 4 km s-1 (~ 8000 K). The selenographic east limb was hotter than the selecographic west limb, resulting from either location of the role plasma sheet ions play in priming the lunar surface. While line width derived temperatures are indicative of an energetic source such as PSD, the large line widths during full Moon could be due to an observed red shift in velocities due to looking down the extended sodium tail.
Observed potassium line widths are much higher (~ 50%) during waxing phase than waning phase at the phase angles >40°. The Potassium temperatures pre-magnetotial passages are ~ 1000K and post-magnetotial passage are ~ 2000K. Potassium is not detected during full Moon period. The potassium relative intensities for the equatorial regions are similar. The brightest observed limb region was off the Aristarchus crater, which is located near the KREEP region.
Scholarly Commons Citation
Kuruppuaratchi, Dona Chathuni P., "The Lunar Exosphere: Spatial and Temporal Variations of Sodium and Potassium Emissions from November 2013 to May 2014" (2015). PhD Dissertations and Master's Theses. 222.