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- Title
Improving Neutral Density Predictions Using Exospheric Temperatures Calculated on a Geodesic, Polyhedral Grid.
- Authors
Weimer, D. R.; Mehta, P. M.; Tobiska, W. K.; Doornbos, E.; Mlynczak, M. G.; Drob, D. P.; Emmert, J. T.
- Abstract
A new model of exospheric temperatures has been developed, with the objective of predicting global values with greater spatial and temporal accuracy. From these temperatures, the neutral densities in the thermosphere can be calculated, through use of the Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar Extended (NRLMSISE‐00) model. The exospheric temperature model is derived from measurements of the neutral densities on several satellites. These data were sorted into triangular cells on a geodesic grid, based on location. Prediction equations are derived for each grid cell using least error fits. Several versions of the model equations have been tested, using parameters such as the date, time, solar radiation, and nitric oxide emissions, as measured with the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Accuracy is improved with the addition of the total Poynting flux flowing into the polar regions, from an empirical model that uses the solar wind velocity and interplanetary magnetic field. Given such inputs, the model can produce global maps of the exospheric temperature. These maps show variations in the polar regions that are strongly modulated by the time of day, due to the daily rotation of the magnetic poles. For convenience the new model is referred to with the acronym EXTEMPLAR (EXospheric TEMperatures on a PoLyhedrAl gRid). Neutral densities computed from the EXTEMPLAR‐NRLMSISE‐00 models combined are found to produce very good results when compared with measured values. Plain Language Summary: Variations in the density of the upper atmosphere have long been a problem for accurate determination of the drag on satellites and their orbital paths. Long‐ and short‐term fluctuations in solar radiation are one factor that influences this density; the energy dissipated by auroral electric fields and currents in the polar ionospheres also results in significant changes in the density of the neutral atoms at high altitudes, in the region known as the thermosphere. Some numerical models that calculate the density in the thermosphere rely on a prediction of the temperature at the top of the thermosphere, known as the exospheric temperature. A new method for forecasting these temperatures has been developed, based on satellite‐based measurements of the atmospheric density. Exospheric temperatures that were derived from these measurements were divided up into triangular grid cells that uniformly cover a sphere. The collected temperatures in each grid cell, along with their associated dates, times, and other measurements, were used to develop a predictive formula, which is unique to each cell. When combined together, global maps of the temperatures are obtained. This method is named using the acronym EXTEMPLAR, EXospheric TEMperatures on a PoLyhedrAl gRid. Key Points: High‐resolution model of exospheric temperatures developedWhen used with the NRLMSISE‐00 code, better predictions of neutral density can be obtainedDuring large geomagnetic storms, substantial increases in the exospheric temperatures occur in the polar regions
- Subjects
EXOSPHERE; NAVAL Research Laboratory (U.S.); SOLAR radiation; NITRIC oxide; PREDICTION models
- Publication
Space Weather: The International Journal of Research & Applications, 2020, Vol 18, Issue 1, pN.PAG
- ISSN
1539-4956
- Publication type
Article
- DOI
10.1029/2019SW002355