Mesosphere
The mesosphere (
The stratosphere and mesosphere are sometimes collectively referred to as the "middle atmosphere",[6] which spans altitudes approximately between 12 and 80 km (7.5 and 49.7 mi) above Earth's surface. The mesopause, at an altitude of 80–90 km (50–56 mi), separates the mesosphere from the thermosphere—the second-outermost layer of Earth's atmosphere. On Earth, the mesopause nearly co-incides with the turbopause, below which different chemical species are well-mixed due to turbulent eddies. Above this level the atmosphere becomes non-uniform because the scale heights of different chemical species differ according to their molecular masses.
The term near space is also sometimes used to refer to altitudes within the mesosphere. This term does not have a technical definition, but typically refers to the region roughly between the
Temperature
Within the mesosphere,
Dynamic features
The main most important features in this region are strong zonal (East-West) winds,
Noctilucent clouds are located in the mesosphere. The upper mesosphere is also the region of the ionosphere known as the D layer, which is only present during the day when some ionization occurs with nitric oxide being ionized by Lyman series-alpha hydrogen radiation. The ionization is so weak that when night falls, and the source of ionization is removed, the free electron and ion form back into a neutral molecule.
A 5 km (3.1 mi; 16,000 ft) deep sodium layer is located between 80–105 km (50–65 mi; 262,000–344,000 ft). Made of unbound, non-ionized atoms of sodium, the sodium layer radiates weakly to contribute to the airglow. The sodium has an average concentration of 400,000 atoms per cubic centimetre. This band is regularly replenished by sodium sublimating from incoming meteors. Astronomers have begun utilizing this sodium band to create "guide stars" as part of the adaptive optical correction process used to produce ultra-sharp ground-based observations.[10] Other metal layers, e.g. iron and potassium, exist in the upper mesosphere/lower thermosphere region as well.
Beginning in October 2018,[11] a distinct type of aurora has been identified, originating in the mesosphere. Often referred to as 'dunes' due to their resemblance to sandy ripples on a beach, the green undulating lights extend toward the equator. They have been identified as originating about 96 km (60 mi; 315,000 ft) above the surface. Since auroras are caused by ultra-high-speed solar particles interacting with atmospheric molecules, the green color of these dunes has tentatively been explained by the interaction of those solar particles with oxygen molecules. The dunes therefore occur where mesospheric oxygen is more concentrated.[12]
Millions of
Exploration
The mesosphere lies above altitude records for
On February 1, 2003, Space Shuttle Columbia broke up on reentry at about 62 km (39 mi) altitude, in the lower mesosphere, killing all seven crew members.
Phenomena in mesosphere and near space
- Airglow
- Atmospheric tides
- Ionosphere
- Meteors
- Noctilucent clouds
- Polar aurora
- Sprite (lightning)
- Upper atmospheric lightning(Transient luminous event)
See also
- Aeronomy
- Amateur radio high-altitude ballooning
- Geospace
- High altitude
References
- ^ "mesosphere". Dictionary.com Unabridged (Online). n.d.
- ^ "Middle atmosphere". www.antarctica.gov.au. Retrieved 17 June 2018.
- ISSN 0148-0227.
- ^ "The Mesosphere - overview". scied.ucar.edu. UCAR Center for Science Education. Retrieved 17 June 2018.
- ISSN 0094-8276.
- ^ "Middle Atmosphere Meteorology". atmos.washington.edu. University of Washington. Retrieved 19 December 2018.
- ^ Photochemistry of Ozone
- ^ Mesosphere (Wayback Machine Archive), Atmosphere, Climate & Environment Information ProgGFKDamme (UK Department for Environment, Food and Rural Affairs), archived from the original on 1 July 2010, retrieved 14 November 2011
- ^ "Martin Enderlein et al., ESO's Very Large Telescope sees four times first light, Laser Focus World, July 2016, pp. 22-24".
- ^ The "dunes" were first spotted by photographers in Finland and Sweden.
- ^ "Wu, Katherine J. A New Type of Aurora Ripples Across the Sky in Horizontal Green "Dunes". Smithsonian Magazine (29 January 2020)".
- ^ Leinert C.; Gruen E. (1990). "Interplanetary Dust". Physics and Chemistry in Space (R. Schwenn and E. Marsch eds.). Springer-Verlag. pp. 204-275
- ^ "Powered Aeroplanes World Records". Fédération Aéronautique Internationale. Archived from the original on 11 September 2016. Retrieved 31 August 2016.
- ^ "Research on Balloon to Float over 50 km Altitude". Institute of Space and Astronautical Science, JAXA. Retrieved 29 September 2011.
- ^ "IADC Space Debris Mitigation Guidelines" (PDF). Inter-Agency Space Debris Coordination Committee. 15 October 2002. Archived from the original (PDF) on 3 December 2013. Retrieved 31 August 2016.
- ^ "NASA Safety Standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris" (PDF). Office of Safety and Mission Assurance. 1 August 1995. Archived from the original (PDF) on 15 February 2013.
- ^ "100 km Altitude Boundary for Astronautics". Fédération Aéronautique Internationale.
- ^ "NASA Sounding Rocket Program Overview". NASA Sounding Rocket Program. NASA. 24 July 2006. Retrieved 10 October 2006.
- ^ "Reusable Rockets Set to Explore the 'Ignorosphere'". Discover Magazine. 1 September 2016. Retrieved 2 April 2018.
- ^ "Upper atmosphere may hold clues in Columbia mystery". 6 February 2003.