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Bougher, S. W.
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- Creator:
- Jenkins, G. J. and Bougher, S. W.
- Description:
- In early 2019, the Mars Atmosphere and Volatile Evolution (MAVEN) mission underwent an ~2-month aerobraking campaign, during which time the spacecraft periapsis altitude was lowered from its nominal altitude range of 140-160 km to as low as ~123 km. Excluding spacecraft walk-in/out maneuvers, accelerometer measurements were made along 272 orbits with coverage spanning Ls 340-3°, latitudes ~5-54°S, longitudes 0-360°, and Local Solar Time (LST) ~22-17 hours. In this study, we perform a diagnostic analysis of the full aerobraking data set by fitting 4-harmonic waves to mass densities. We then study the variations of these waves as a function of latitude with an emphasis on those observed previously in Mars’ thermosphere by MAVEN and other missions. Additionally, we utilize data collected during the same time period from the Mars Reconnaissance Orbiter’s Mars Climate Sounder to study the vertical propagation of waves originating from the middle atmosphere. Key results indicate that normalized wave amplitudes decrease with latitude, and this is consistent with the latitudinal structure of a diurnal Kelvin mode. We also observe that waves imprinted from the middle atmosphere show normalized amplitude growth with increasing altitude. A complete summary of data sets, analysis methodology, and scientific results is given. The purpose of this study is to add to the body of knowledge surrounding Martian atmospheric wave features and to provide further constraints for future numerical modeling and subsequent tidal mode identification.
- Keyword:
- MAVEN, Mars Thermosphere, Accelerometer Data Set, Global Data Set, and Wave Analysis of Tides
- Citation to related publication:
- Jenkins, G. A., Bougher, S. W., Lugo, R., Tolson, R. H., Zurek, R. W., Baird, D., Steele, L., Kass, D., Withers, P. (2023), MAVEN Accelerometer Observations of Thermospheric Densities during Aerobraking and Deep Dip 2: Wave Features and Connections to Upward Propagating Thermal Tides, Journal of Geophysical Research: Planets, xx, xx.
- Discipline:
- Science
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- Creator:
- Bougher, S. W. and Parkinson, C. D.
- Description:
- Understanding the state and composition of an exoplanetary atmosphere depends upon several parameters such as heating, cooling, mixing and reactions between constituent chemical species. Only a few types of atmospheric species can be detected remotely spectroscopically and only if their abundance is large enough to be detectable. In this initial study, we model the atmosphere of a Venus-like planet orbiting the M-type star GJ 436 to determine the global neutral temperature structure, winds, and energy balance as the radial distance of the planet from the star decreases.
- Keyword:
- Venus-like exoplanet, upper atmospheres , and heat balances
- Citation to related publication:
- C. D. Parkinson, S. W. Bougher, F. P. Mills, R. Hu, G. Gronoff, J. Li, A. Brecht, D. Adams, and Y. L. Yung. Venus as an Exoplanet: I. An Initial Exploration of the 3-D Energy Balance for a CO2 Exoplanetary Atmosphere Around an M-Dwarf Star, J. Geophysical Research, X, (2022). doi:....
- Discipline:
- Science
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Dynamical Heating in the Martian Thermosphere: Temperatures, Winds and Thermal Balances using M-GITM
- Creator:
- Bougher, S. W. and Pilinski, M. D.
- Description:
- The NASA MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft, which is currently in orbit around Mars, has been taking systematic measurements of the densities and deriving temperatures in the upper atmosphere of Mars (between about 140 to 240 km above the surface) since late 2014. Wind measurement campaigns have also been conducted once per month for 5-10 orbits since 2016. These densities, temperatures and winds change with time (e.g. solar cycle, season, local time) and location, and sometimes fluctuate quickly. Global dust storm events are also known to significantly impact these density, temperature and wind fields in the Mars thermosphere. For the current project, in-situ measured winds and corresponding argon density derived temperatures are combined to trace the circulation patterns and investigate their convergence and divergence locations and impacts throughout the Mars thermosphere. M-GITM computed thermal balance terms are subsequently extracted to investigate the processes required to maintain the temperature distribution around the planet. For this work, Mars Year #33 (MY33) Neutral Gas and Ion Mass Spectrometer (NGIMS) measurements have been obtained by the MAVEN team for this purpose (see these representative works: (Bougher et al., 2017; Stone et al., 2018; Benna et al., 2019). These temperature and wind fields are compared to simulations from a computer model of the Mars atmosphere called M-GITM (Mars Global Ionosphere-Thermosphere Model), developed at U. of Michigan. Since the global circulation plays a role in the structure, variability, and evolution of the atmosphere, understanding the processes that drive the winds in the upper atmosphere of Mars also provides the needed context for understanding temperature distributions and underlying thermal balances throughout the atmosphere. Three dimensional M-GITM simulations for three of the four Mars cardinal seasons (Ls = 0, 90, 270) for MY33 were conducted for detailed comparisons with NGIMS temperature and wind distributions (Pilinski et al. 2022). Corresponding M-GITM datacubes used to extract these temperatures (plus winds) along the trajectory of each orbit path between 140 and 240 km, are provided in this Deep Blue Data archive. A single README file is included that details the contents of each datacube file. In addition, this general README file summarizes the inputs and outputs of each M-GITM simulation interval used for this study. Finally, a basic version of the M-GITM code can be found on Github at https:/github.com/dpawlows/MGITM.
- Keyword:
- MAVEN, Mars thermosphere, global dynamics, and heat balances owing to winds
- Citation to related publication:
- Pilinski, M. D., K. J. Roeten, S. W. Bougher and M. Benna, Dynamical Heating in the Martian Thermosphere, Journal Geophysical Res., XXX, (forthcoming - 2022). doi: .....
- Discipline:
- Science