The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere
Measurements made by Voyager 2 during its flyby of Uranus in 1986 found warm stratospheric and hot thermospheric temperatures that cannot be explained by solar energy alone. This contributes to what is known as the “giant planet energy crisis”: there is a fundamental lack of understanding of the ene...
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2024-01-01
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| Online Access: | https://doi.org/10.3847/PSJ/ad7c4d |
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| author | William R. Saunders Michael J. Person Paul Withers Richard G. French Chanita Tubthong |
| author_facet | William R. Saunders Michael J. Person Paul Withers Richard G. French Chanita Tubthong |
| author_sort | William R. Saunders |
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| description | Measurements made by Voyager 2 during its flyby of Uranus in 1986 found warm stratospheric and hot thermospheric temperatures that cannot be explained by solar energy alone. This contributes to what is known as the “giant planet energy crisis”: there is a fundamental lack of understanding of the energy balance of giant planets in the solar system. Uranus, in particular, has the coldest stratosphere temperatures, the hottest thermospheric temperatures, and the weakest internal heat flux of all four giant planets. Moreover, the Voyager 2 temperature measurements are at odds with many contemporaneous Earth-based stellar occultations. In Paper I, we introduced two updated techniques for reanalyzing these 26 occultations—forward modeling and inversion—and demonstrated them on the 1977 Uranus occultation. This work (Paper II) presents the results of applying these techniques to 26 total Uranus stellar occultations, observed between 1977 and 1996. We find that the lower thermosphere of Uranus is much cooler than the Voyager 2 profiles but slightly warmer than the originally published occultations. We find that the stratosphere of Uranus is nearly isothermal and the stratosphere–thermosphere boundary is much higher in altitude than previously believed. Furthermore, we present a family of new, one-dimensional atmospheric models for Uranus fit to our results. The models suggest that there is a significant source of heat transport or dissipation away from the stratosphere, which we discuss as resulting from gravity-wave activity. We offer our models as new representative profiles and discuss how they improve the understanding of the energy balance of Uranus. |
| format | Article |
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| institution | Kabale University |
| issn | 2632-3338 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
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| series | The Planetary Science Journal |
| spelling | doaj-art-ec1cf9b75e1c4d9d8f3e0a0ae9314c472024-11-15T16:51:40ZengIOP PublishingThe Planetary Science Journal2632-33382024-01-0151124710.3847/PSJ/ad7c4dThe Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower ThermosphereWilliam R. Saunders0https://orcid.org/0000-0002-8737-742XMichael J. Person1https://orcid.org/0000-0003-0000-0572Paul Withers2https://orcid.org/0000-0003-3084-4581Richard G. French3https://orcid.org/0000-0002-9858-9532Chanita Tubthong4https://orcid.org/0000-0002-7907-2634NASA Langley Research Center , Hampton, VA 23666, USA ; william.r.saunders@nasa.gov; Analytical Mechanics Associates , Hampton, VA 23666, USADepartment of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology (MIT) , Cambridge, MA 02139-4307, USADepartment of Astronomy, Boston University , Boston, MA 02215, USA; Center for Space Physics, Boston University , Boston, MA 02215, USASpace Science Institute , Boulder, CO 80301, USA; Department of Astronomy, Wellesley College , Wellesley, MA 02481, USADepartment of Physics and Astronomy, Tufts University , Medford, MA 02155, USAMeasurements made by Voyager 2 during its flyby of Uranus in 1986 found warm stratospheric and hot thermospheric temperatures that cannot be explained by solar energy alone. This contributes to what is known as the “giant planet energy crisis”: there is a fundamental lack of understanding of the energy balance of giant planets in the solar system. Uranus, in particular, has the coldest stratosphere temperatures, the hottest thermospheric temperatures, and the weakest internal heat flux of all four giant planets. Moreover, the Voyager 2 temperature measurements are at odds with many contemporaneous Earth-based stellar occultations. In Paper I, we introduced two updated techniques for reanalyzing these 26 occultations—forward modeling and inversion—and demonstrated them on the 1977 Uranus occultation. This work (Paper II) presents the results of applying these techniques to 26 total Uranus stellar occultations, observed between 1977 and 1996. We find that the lower thermosphere of Uranus is much cooler than the Voyager 2 profiles but slightly warmer than the originally published occultations. We find that the stratosphere of Uranus is nearly isothermal and the stratosphere–thermosphere boundary is much higher in altitude than previously believed. Furthermore, we present a family of new, one-dimensional atmospheric models for Uranus fit to our results. The models suggest that there is a significant source of heat transport or dissipation away from the stratosphere, which we discuss as resulting from gravity-wave activity. We offer our models as new representative profiles and discuss how they improve the understanding of the energy balance of Uranus.https://doi.org/10.3847/PSJ/ad7c4dUranusStellar occultationPlanetary atmospheresStratosphereThermosphere |
| spellingShingle | William R. Saunders Michael J. Person Paul Withers Richard G. French Chanita Tubthong The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere The Planetary Science Journal Uranus Stellar occultation Planetary atmospheres Stratosphere Thermosphere |
| title | The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere |
| title_full | The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere |
| title_fullStr | The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere |
| title_full_unstemmed | The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere |
| title_short | The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere |
| title_sort | upper atmosphere of uranus from stellar occultations ii revised temperatures in the upper stratosphere and lower thermosphere |
| topic | Uranus Stellar occultation Planetary atmospheres Stratosphere Thermosphere |
| url | https://doi.org/10.3847/PSJ/ad7c4d |
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