Local-time asymmetries in the Venus thermosphere

Our current understanding of the global structure and dynamics of the Venus thermosphere is embodied in models such as the Venus Thermospheric General Circulation Model (VTGCM) and empirical composition models such as VIRA and VTS3. We have completed an analysis of ultraviolet images of Venus at 130 nm acquired by the Pioneer Venus Orbiter Ultraviolet Spectrometer (PVOUVS). We have examined 97 images spanning the 10-year period between 1980 and 1990, and have developed a technique for global radiative transfer modeling with which we create synthetic models of each image analyzed. We have developed a hypothesis for understanding the persistent local-time asymmetry observed as a signature of vertically propagating internal gravity waves interacting with the thermospheric SS-AS circulation. This hypothesis is presented

Solar cycle variability of Mars dayside exospheric temperatures: Model evaluation of underlying thermal balances

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95086/1/grl25450.pd

Four Martian years of nightside upper thermospheric mass densities derived from electron reflectometry: Method extension and comparison with GCM simulations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95498/1/jgre2766.pd

Mars ultraviolet dayglow variability: SPICAM observations and comparison with airglow model

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95472/1/jgre2751.pd

Processes of equatorial thermal structure at Jupiter: An analysis of the Galileo temperature profile with a three‐dimensional model

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94956/1/jgre1925.pd

Structural and Compositional Changes in the Upper Atmosphere Related to the PEDE‐2018 Dust Event on Mars as Observed by MAVEN NGIMS

The onset of the planet encircling dust event (PEDE‐2018) started around 1 June 2018 as observed by Mars Reconnaissance Orbiter/Mars Color Imager, peaking around 7–10 July and persisting through mid‐October 2018. After the onset of the event, the upper atmosphere underwent significant changes in density and thermal structures. Mars Atmosphere and Volatile Evolution‐Neutral Gas and Ion Mass Spectrometer (MAVEN NGIMS) had a good opportunity to observe these changes from the first detection in the upper atmosphere and throughout the duration of the PEDE. The compositional changes included increased density at a constant altitude for CO2 and Ar, while the O decreased from the peak throughout the decay of the bulk of the PEDE.Plain Language SummaryFrom June through October 2018 Mars experienced a planet encircling dust event (PEDE‐2018), a fairly rare event last observed in 2007. The dust storm grew from a local event to cover the entire planet and was opaque enough that so little sunlight reached the surface that the solar‐powered opportunity rover ceased operations and all attempts to re‐establish contact with it were unsuccessful. Meanwhile, the orbiter Mars Atmosphere and Volatile Evolution (MAVEN) was able to observe changes in the upper atmosphere in the composition as a result of this globally extensive PEDE. MAVEN observed increases in both the CO2 and Ar while also observing an unexpected reduction in the O densities.Key PointsMAVEN/NGIMS observed increased of CO2 and Ar densities observed in the upper atmosphere corresponding to the peak of the dust eventUnexpected decrease in O densities in the upper atmosphere (160–250 km) was simultaneously observedComparisons between model and data results show good agreement with scale height and temperatures, further M‐GITM model revisions needed to capture circulation effectsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154472/1/grl59716_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154472/2/grl59716.pd

Characterization of middle‐atmosphere polar warming at Mars

We characterize middle‐atmosphere polar warming (PW) using nearly three Martian years of temperature observations by the Mars Climate Sounder. We report the observed structure of PW and share hypotheses as to possible explanations, which have yet to be tested with global dynamical models. In the data, PW manifested between p  = 15 Pa and p  = 4.8×10 –3  Pa. The latitude where PW maximized shifted poleward with decreasing pressure. The nightside magnitude was larger than the dayside magnitude. The maximum nightside magnitudes ranged from 22 to 67 K. As expected, the annual maximum magnitude in the north occurred during late‐local fall to middle‐local winter. In the south it occurred during late‐local winter. Also as expected, the maximum magnitude near MY 28's southern winter solstice was smaller than that at that same year's northern winter solstice, when a global dust storm was occurring. Unexpectedly, the maximum magnitude at southern winter solstice was comparable to that at northern winter solstice for both MY 29 and MY 30, years that did not experience global dust storms but certainly experienced greater dust loading during L s  = 270° than L s  = 90°. Another unexpected result was a hemispheric asymmetry in PW magnitude during most of the observed equinoxes. This paper also provides tables of (1) averaged temperatures as a function of latitude, pressure, and season, and (2) the maximum polar warming features as a function of pressure and season. These tables can be used to validate GCM calculations of middle‐atmosphere temperatures and constrain calculations of unobserved winds. Key Points Polar warming is characterized based on nearly three MYs of MCS temperatures Average temperatures are provided for validation of modeled temperatures Polar warming characteristics are provided for constraint of modeled windsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97505/1/jgre20016.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/97505/2/SPICAM_temperatures_v_latitude.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/97505/3/PolarWarming_CrossSections_Dayside.pd

Application of Acclerometer Data to Atmospheric Modeling During Mars Aerobraking Operations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77186/1/AIAA-28472-302.pd

Processes of Equatorial Thermal Structure: An Analysis of Galileo Temperature Profile with 3-D Model

The Jupiter Thermosphere General Circulation Model (JTGCM) calculates the global dynamical structure of Jupiter's thermosphere self-consistently with its global thermal structure and composition. The main heat source that drives the thermospheric flow is high-latitude Joule heating. A secondary source of heating is the auroral process of particle precipitation. Global simulations of Jovian thermospheric dynamics indicate strong neutral outflows from the auroral ovals with velocities up to approximately 2 kilometers per second and subsequent convergence and downwelling at the Jovian equator. Such circulation is shown to be an important process for transporting significant amounts of auroral energy to equatorial latitudes and for regulating the global heat budget in a manner consistent with the high thermospheric temperatures observed by the Galileo probe. Adiabatic compression of the neutral atmosphere resulting from downward motion is an important source of equatorial heating (less than 0.06 microbar). The adiabatic heating continues to dominate between 0.06 and 0.2 microbar, but with an addition of comparable heating due to horizontal advection induced by the meridional flow. Thermal conduction plays an important role in transporting heat down to lower altitudes (greater than 0.2microbar) where it is balanced by the cooling associated with the wind transport processes. Interestingly, we find that radiative cooling caused by H3(+), CH4, and C2H2 emissions does not play a significant role in interpreting the Galileo temperature profile

Incorporation of a gravity wave momentum deposition parameterization into the Venus Thermosphere General Circulation Model (VTGCM)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96657/1/jgre20038.pd