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The Upper Atmosphere; Threshold of Space. INSTITUTION National Aeronautics and Space Administration, Washington, D.C

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The Upper Atmosphere; Threshold of Space. INSTITUTION National Aeronautics and Space Administration, Washington, D.C DOCUMENT RESUME ED 310 934 SE 050 880 AUTHOR Bird, John TITLE The Upper Atmosphere; Threshold of Space. INSTITUTION National Aeronautics and Space Administration, Washington, D.C. REPORT NO NASA-NP-105 PUB DATE 88 NOTE 40p.; Colored photographs and pages will not reproduce well. PUB TYPE Books (010) -- Reports - Descriptive (141) EDRS PRICE MF01/PCO2 Plus Postage. DESCRIPTORS *Earth Science; Satellites (Aerospace); *Science Materials; Scientific Personnel; *Scientific Research; Scientists; *Space Exploration; *Space Sciences ABSTRACT This booklet contains illustrations of the upper atmosphere, describes some recent discoveries, and suggests future research questions. It contains many color photographs. Sections include: (1) "Where Does Space Begin?";(2) "Importance of the Upper Atmosphere" (including neutral atmosphere, ionized regions, and balloon and investigations);(3) "Airglow"; (4) "Aurora"; (5) "Recent Discoveries" (those made by manned and unmanned spacecraft); (6) "Future Research" (describing spacelab missions, tethered satellite, the International Solar-Terrestrial Physics Program/Global Geospace Science Mission, and others); (7) "Unanswered Questions"; (8) "Conclusion"; and (9) "Sources" (listing general and technical materials). (YP) ****X********************************It********************************* * Reproductions supplied by EDRS are the best that can be made * from the original document. *************************************************x********************* e r 4, e, .* x Is a ) a .11 t A- 4 .., vr 4 1 Ar v 410 T U S DEPARTMENT OF EDUCATION Once of Educational Research ano impranement EDUCATIONAL. RESOURCES INFORMATION CENTER (ERIC) krnsdocument has been ,eproduced as ';' ,ece.sed from the person ol orgamzahon ohomatmg A 1.,.L... O Knor changes have been made to ,mpvove teproduehon dually '11111/1 Pants of view or opoxons stated .n this doctr ment do not necessaray represent offictal OERI poshon of poky if .1, 2 (41 oetar.twat's.%L. iT A 4 ,01 *V 41. 3 Table of 1 Where does space begin? Contents 3Importance of the upper atmosphere 3 Neutral atmosphere 3 Troposphere 5 Stratosphere 6 Mesosphere 6 Thermosphere 7 Exosphere 7 Weightlessness 8 Ionized regions 8 Ionosphere 9 Magnetosphere 10 Balloon and investigations 13 Airglow 13 What is it? 13 Spacecraft observations 15 Aurora 15 What is it? 16 How does it occur? 19 Recent discoveries 19 Spacecraft glow 20 Spacelab 1 21 Unmanned spacecraft 23 Future research 23 Spacelab missions 23 Earth Observation Mission-1 23 Space Plasma Lab 25Tethered satellite 25 International Solar-Terrestrial Physics Program/ Global Geospace Science Mission 28Other future programs 28 Space Station 28 Lidar 28 Long Duration Exposure Facility 30 Upper Atmosphere Research Satellite 30 Earth Radiation Budget Experiment 33 Unanswered questions 33 Conclusion 34 Sources 35 Acknowledgments 35 Photo credits 35The author 4 44.Pv. r - 11R , e are conscious of the weath- Even the thinnest part of our atmosphere Importance er, but largely unaware of the is important. Less than 0.1 percent ofour atmosphere above the clouds. atmosphere (by mass) is above 50 kilome- of the upper However, what happens in ters (31 mi), yet it occupies a volume much this higher atmosphere affects the atmo- larger than Earth. The Sun's rays mustcross atmosphere sphere below the clouds. Indeed, at the bot- this region before reaching us. Further, the tom of the atmosphere, we see only the end upper atmosphere is important to radio result of diverse processes extending from communications. Earth's surface to interplanetary space. Rather than being isolated and indepen- dent, these regions interact and intercon- Neutral Atmosphere nect. They form a chain from the surface of Earththrough the atmosphere and our Just where does the lower atmosphere end solar-terrestrial environmentto the Sun. and the upper atmosphere begin? For the Ultimately, all disturbances in this environ- human body, the upper atmosphere begins ment originate inside the Sun. These distur- a few kilometers above sea level; for a bances spread through the chain via solar spacecraft it could be considered to begin wind and radiation to influence our weath- at about 160 kilometers (99 mi). Without a er, our climate, and even our communica- generally accepted altitude to mark it, the tions. More importantly, the processes in upper atmosphere can best be understood this chain are finely tuned to a delicately by starting on the ground and moving balanced equilibrium compatible with life upward to examine it, layer by layer. Our on Earth. atmosphere is considered to be composed All regions of the atmosphere interact to of layers. We distinguish these layers by provide conditions essential to life and to temperature and by composition. Both protect life in many ways. The atmosphere methods are shown in the illustration on provides life's most fundamental needs for page 2. In the temperature classification survival: pressure, proper temperature, and system, each layer is characterized by its oxygen. Without them there would be no unique temperature variation, or gradient. life on Earth. Without the atmosphere,one Where do the layer names come from? side of our planet would be frozen; the Troposphere is from the Greek word tro- other would be cooked by solar radiation. pos meaning to turn, implying that this Fortunately, the atmosphere transmits just region is turning and creating weather as the right amount of sunlight and contains we know it. Stratosphere comes from the just the right mixture of oxygen, nitrogen, Latin word stratum, meaning layer. and carbon dioxide to sustain life. Mesosphere comes from the Greek word We are inescapably surrounded by the mesos, meaning middle. Tl:ermosphere atmosphere and its influences. Besides ful- comes from the Greek word therme, mean- filling our basic needs, how does theatmo- ing heat. Exosphere means external to the sphere influence us? It determines our cli- atmosphere. mate and weather, including hurricanes, flash floods, tornadoes, and lightning. It Troposphere also influences the flow of pollution, such In the lowest layer, or troposphere, the tem- as acid rain. Variations in weather may perature decreases the higher you go. You Earth as seen from a even influence our moods. may have noticed this if you have ever balloon at 37 km. Most of the atmosphere is been on a mountain. Some mountains below. remain snow-capped all year because of their elevation. The troposphere has many other impor- tant characteristics, including weight and pressure, that are essential for life. Although we are usually oblivious to the air that surrounds us, air exerts a pressure of about 101,000 pascals (14.7 psi). And 3 Concorde air has weight. In fact, a refrigerator con- We may acclimatize or adapt to the thin- tains roughly .45 kilograms (one pound) of ner air, but this involves living at succes- air. Why don't we feel the weight of the sively higher altitudes over a period of air? We do not feel the weight because we weeks. It is possible to live about 4.2 kilo- are surrounded by it, just as we do not feel meters (2.6 mi) as do some people in Tibet; the weight of the water in a swimming pool however, at this altitude, we are above vir- when we are in it. If we were not in the air tually all plant and animal life. Our bodies or the water, we could easily notice its are physiologically incompatible with this weight. How? Could you carry a swim- elevation. Without acclimatization or sup- ming pool? No, it has too much weight. plementary oxygen, it is hard to breathe, Similarly, if you were in a huge vacuum and night vision deteriorates. At 4.2 kilo- chamber you would find that a room-size meters (2.6 mi) these effects are immedi- box of air would be heavy. ately apparent, but the threshold level may Other basic conditions for lifeproper be as low as 1.6 kilometers (1 mi) for temperature and oxygenare also found in someone accustomed to sea level. the troposphere, but only near the surface. To climb higher into the sky, let's take a What happens as we go higher? commercial jet. We soon pass the height of From the iop of a mountain at roughly 5 the summit of Mt. Everest at 9 kilometers kilometers (3.1 mi), we can see clouds (5.6 mi) and continue up to a cruising alti- below. Small private aircraft usually fly tude of 10.6 kilometers (6.6 mi). From here below this altitude because their rate of we see a few thin wispy clouds around us climb reduces as the air becomes thinner. and puffy white cumulus clouds far below. At this altitude, whether we are in an If the aircraft were not pressurized and unpressurized aircraft or on a mountain, we equipped with its own oxygen supply, we need supplementary oxygen unless we would last a few minutes at most. Winds at return to lower altitudes within a few min- this height are strong, frequently exceeding utes. 161 kilometers (100 mi) per hour. Temperatures are also extreme: 50° C (-58°F) is typical. 4 tS Exosphere The Atmosphere Day Night 300_ _300 iiiiiiiiiiiiSolar radiation F2 peak 200_ y X UV 1R Radio _200 .1A E Region 100 E Thermosphere _100 90 -0 90 80_ Ionosphere _ 80 70 Mesosphere _ 70 60_ _ 60 50_ _ 50 40 _ 40 Stratosphere 30 _ 30 20 Troposphere _ 20 10_, _10 0 0 -90 106 105 104 103 102 Temperature, °C Electron density cm-3 At IIkilometers (6.8 mi), we reach the tern (12.4mi), we are above 90 percent of top of the troposphere. This dividing line is the atmosphere and the sky becomes a dark called the tropopause. The exact altitudes violet merging into black. At this height we delimiting the layers of the atmosphere begin to notice the curve of Earth. At 30 change with local air temperature and kilometers (18.6 mi), the extremely low depend on variables such as time of year.
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