A Science Strategy for Space Physics (1995) / Chapter Skim
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A Science Strategy for Space Physics: Chapter 4
A Science Strategy for Space Physics: Chapter 4
Pages 66-81
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From page 66... ...
drive many interacting physical and chemical processes in the middle and upper atmosphere, including global-scale winds, gravity waves and turbulence, photochemical reactions, the global electrical circuit, and radiative, REPORT MENU dynamical, and chemical transports of energy. The interplay between these inputs and the NOTICE processes that redistribute energy from the individual source regions throughout the layer MEMBERSHIP is not well understood.
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From page 67... ...
The middle atmosphere contains the ozone layer that shields the biosphere from solar ultraviolet radiation. Thus, changes in the amount of stratospheric ozone alter, the biosphere's exposure to this harmful radiation.
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From page 68... ...
What is the quantitative relationship between global, lower-stratospheric ozone depletion, radiative forcing of the Earth-atmosphere system, and climate change? What are the global climate impacts of the Antarctic ozone hole (which is expected to persevere well into the next century)
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From page 69... ...
Infrared radiation from the Earth's surface and lower atmosphere help determine the energy budget of the middle atmosphere. Many of the middle atmosphere constituents are introduced from below, either directly, or indirectly in the form of chemical precursors.
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From page 70... ...
Complex interactions among the energetics, chemistry, dynamics, and electrodynamics of the middle and upper atmospheres determine their structure and variability. The absorption of solar ultraviolet radiation by ozone, and the absorption and emission of infrared radiation by carbon dioxide, ozone, water vapor, and other species, depend on the distributions of those components, which in turn depend on chemical processes and atmospheric circulation.
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From page 71... ...
in the middle atmosphere (Figure 16)
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From page 72... ...
An adequate quantification of the roles of turbulence and gravity waves in heating and cooling these regions has not yet been achieved. The distribution of net atmospheric heating throughout the middle atmosphere is not well known.
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From page 73... ...
The recent visual confirmation of the occurrence of lightning discharges upward to altitudes greater than 60 km, coupling thunderstorm energy directly into the middle atmosphere, has dramatically underscored the paucity of knowledge in this area. These electrical discharges and other interesting observations of x-ray and gamma-ray bursts associated with active thunderstorm cells indicate that the direct upward electrical energy input into the ionosphere and thermosphere is much more important than previously thought.
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From page 74... ...
A major challenge to scientists studying the middle and upper atmospheres is to gain a comprehensive understanding of the relevant inputs and internal processes so that reliable models of these atmospheric regions can be developed that have useful operational and predictive capabilities. The following are some of the principal questions: What is the absolute solar spectral irradiance below 300 run, especially in the poorly determined region below 40 nm, and how does the irradiance vary on time scales of minutes to decades?
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From page 75... ...
to middle-atmospheric chemistry and dynamics and to ionospheric electrical phenomena? What are the generators, electric charge storage systems, and active and passive current paths that constitute the middle and upper atmospheric portions of the global electric circuit?
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From page 76... ...
Similarly, current knowledge of gravity wave fluxes, mesospheric tides and planetary waves, the temperature structure of the summer mesopause, and the structure and variability of the ionosphere and thermosphere is being advanced by application of ground-based techniques. Suborbital experiments are a key component of the current program.
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From page 77... ...
New algorithms are being developed that might allow consistent, well calibrated ozone profiles to be recovered from the NIMBUS and TIROS data, but those measurements will not give ozone profile information in the lower stratosphere. The SAGE instrument has given ozone profile measurements in this region, and the ILAS instrument on the Japanese ADEOS spacecraft should give similar information.
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From page 78... ...
The most ambitious planetary aeronomy observations in the cur-rent program are those planned for Saturn's satellite Titan as part of the Cassini mission. The European provided Huygens probe will obtain atmospheric profiles from the middle atmosphere down to the surface, while the main Cassini spacecraft will carry a mass spectrometer for the analysis of ions and neutral species each time the spacecraft dips through the upper atmosphere for orbit-changing gravity assists.
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From page 79... ...
These sources of data, though extremely useful for improving our understanding of this region, are restricted to fixed geographic locations and thus are insufficient to allow us to characterize the complex global behavior that involves distributed energy sources along with large-scale dynamics and both horizontal and vertical transport of energy. UARS has recently expanded this database by providing global observations of winds, temperatures, and some minor constituents over altitudes extending into the mesosphere.
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From page 80... ...
One method of achieving this goal would be the use of a swarm of microsatellites in polar orbits spaced in local time to obtain nearly instantaneous global patterns of key parameters. Another approach would be to expand the network of ground-based incoherent scatter and other radars.
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From page 81... ...
Important gaps in our knowledge of the dynamics of the upper atmospheres of Venus and Mars Could be filled by observations of upper atmospheric winds using instruments such as a Fabry-Perot or a Michelson interferometer on spacecraft orbiting the planet. The chemistry and physics of the upper martian atmosphere could be addressed by orbiting instruments such as neutral and ion mass spectrometers and Langmuir probes.
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