Collaborative Research: CEDAR--Optical Aeronomical Observations at Millstone Hill

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The investigators will upgrade and rebuild optical instruments at the Millstone Hill Observatory in Massachusetts. The instruments include a new patrol Fabry-Perot interferometer (FPI), an all-sky Doppler imager (ASDI), and a spectrometer. The observations will be used to systematically address a number of issues in mesospheric and thermospheric physics. Research will include the study of mid-latitude mesosphere and lower thermosphere (MLT) tides using the combined FPI mesospheric and thermospheric Doppler winds and all-sky images from hydroxyl and oxygen emissions and incoherent scatter radar observations. The semidiurnal tide usually has a large vertical wavelength so the combined observations will provide a large vertical altitude coverage during both the day and night, and will allow for a better characterization of the vertical tidal structure. Also, the all-sky imager at Millstone Hill will record the hydroxyl, sodium, and oxygen nightglow emissions for gravity wave activity and the investigators will use the FPI neutral winds from the same emissions to calculate the intrinsic gravity wave parameters. From the intrinsic parameters, they will deduce the propagation modes of the waves and several important wave parameters including quantitative measurements of vertical scale-sizes, estimates of the vertical fluxes of horizontal wave momentum and energy, and the amount of wave flux divergence between the airglow layers, the hydroxyl and oxygen layers, in particular. The FPI neutral wind and temperature measurements will be used to study the long-term trends in the mesosphere and thermosphere in connection with the solar cycles, and small-scale thermosphere temperature and neutral wind variations will be studied using the all sky Doppler imager. The regional cluster of optical instruments in conjunction with the Millstone Hill Incoherent Scatter radar will provide comprehensive coverage from the mesosphere to the thermosphere. They will provide a unique data set for studies of MLT dynamics and ionosphere/thermosphere interaction in the sub-auroral region. Multi-institute participation will foster more collaboration between different research groups. The Millstone Hill optical instruments will also be the test bed for the future distributed instrument projects.