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A three-dimensional view of the Earth's magnetosphere 〔James L. Green氏による。NASAのSpace Science Education Outreachの中の『The Magnetosphere』から〕 磁気圏のようす。左手から太陽風〔太陽から放出されるプラズマ(電子や陽子など)〕が照射されているが、地球大気と地磁気によるバリアーが形成されている。地球の地軸方向(ほぼ地理学的な北極と南極付近)はバリアーが弱く、侵入したプラズマと大気の反応による発光現象がおこり、これはオーロラと呼ばれる。 |
Figure 7b-1: Vertical change in average global atmospheric temperature. Variations in the way temperature changes with height indicates the atmosphere is composed of a number of different layers (labeled above). These variations are due to changes in the chemical and physical characteristics of the atmosphere with altitude. 〔Michael Pidwirny氏によるPhysicalGeography.netの『FUNDAMENTALS OF PHYSICAL GEOGRAPHY』の『CHAPTER 7: Introduction to the Atmosphere』の『(b). The Layered Atmosphere』から〕 大気の温度構造。高度に対して温度は下降と上昇を繰り返しているが、その変わり目を境界として、地表から対流圏・成層圏・中間圏・熱圏と名づけられている。それらの境界は、地表から対流圏界面・成層圏界面・中間圏界面と呼ばれる。成層圏界面付近の温度上昇は、太陽紫外線によるオゾンの生成と分解に伴う発生熱による。なお、オゾン層は高度20〜30km付近に存在する。また、熱圏の温度上昇は、大気を構成するさまざまなガス分子の太陽紫外線による電離反応に伴う発生熱による。 |
Figure Q1-2. Atmospheric ozone. Ozone is present throughout the lower atmosphere. Most ozone resides in the stratospheric “ozone layer” above Earth’s surface. Increases in ozone occur near the surface as a result of pollution from human activities. 〔NOAA Aeronomy Laboratoryの『International Ozone-Layer Assessments』の『WMO/UNEP Scientific Assessment of Ozone Depletion: 2002』の『Twenty Questions and Answers About the Ozone Layer』の『I OZONE IN OUR ATMOSPHERE』の中の『Q1: What is ozone and where is it in the atmosphere?』から〕 成層圏にはオゾン濃度の高い層が存在し、オゾン層と呼ばれる。上空ほど大気圧(濃度)が低くなるため、オゾンのすべてをもし地表に集めたらわずか3mm程度にしかならない。オゾン(O3)の生成には、酸素分子(O2)と太陽紫外線が必要なため、両者の条件が適する高度に多い。 |
Figure Q2-1. Stratospheric ozone production. Ozone is naturally produced in the stratosphere in a two-step process. In the first step, ultraviolet sunlight breaks apart an oxygen molecule to form two separate oxygen atoms. In the second step, these atoms then undergo a binding collision with other oxygen molecules to form two ozone molecules. In the overall process, three oxygen molecules react to form two ozone molecules. 〔NOAA Aeronomy Laboratoryの『International Ozone-Layer Assessments』の『WMO/UNEP Scientific Assessment of Ozone Depletion: 2002』の『Twenty Questions and Answers About the Ozone Layer』の『I OZONE IN OUR ATMOSPHERE』の中の『Q2: How is ozone formed in the atmosphere?』から〕 酸素分子から太陽紫外線のはたらきでオゾン(分子)が生成する反応式。これは、自然の作用である。 |
参考 |
Figure Q9-1. Ozone destruction Cycle 1. The destruction of ozone in Cycle 1 involves two separate chemical reactions. The net or overall reaction is that of atomic oxygen with ozone, forming two oxygen molecules. The cycle can be considered to begin with either ClO or Cl. When starting with ClO, the first reaction is ClO with O to form Cl. Cl then reacts with (and thereby destroys) ozone and reforms ClO. The cycle then begins again with another reaction of ClO with O. Because Cl or ClO is reformed each time an ozone molecule is destroyed, chlorine is considered a catalyst for ozone destruction. Atomic oxygen (O) is formed when ultraviolet sunlight reacts with ozone and oxygen molecules. Cycle 1 is most important in the stratosphere at tropical and middle latitudes where ultraviolet sunlight is most intense. 〔NOAA Aeronomy Laboratoryの『International Ozone-Layer Assessments』の『WMO/UNEP Scientific Assessment of Ozone Depletion: 2002』の『Twenty Questions and Answers About the Ozone Layer』の『II THE OZONE DEPLETION PROCESS』の中の『Q9: What are the chlorine and bromine reactions that destroy stratospheric ozone?』から〕 生成したオゾンを破壊する反応のひとつである塩素サイクル。これも、自然の作用であるが、人間がつくったフロンから生成した塩素がオゾン層を破壊するという環境問題によって注目されている。 |
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Figure Q11-2. Arctic and Antarctic ozone distribution. The stratospheric ozone layer resides between about 10 and 50 kilometers (6 to 31 miles) above Earth’s surface over the globe. Long-term observations of the ozone layer from small balloons allow the winter Antarctic and Arctic regions to be compared. In the Antarctic at the South Pole, halogen gases have destroyed ozone in the ozone layer beginning in the 1980s. Before that period, the ozone layer was clearly present as shown here using average ozone values from balloon observations made between 1962 and 1971. In more recent years, as shown here for 2 October 2001, ozone is destroyed completely between 14 and 20 kilometers (8 to 12 miles) in the Antarctic in spring. Average October values in the ozone layer now are reduced by 90% from pre-1980 values. The Arctic ozone layer is still present in spring as shown by the average March profile obtained over Finland between 1988 and 1997. However, March Arctic ozone values in some years are often below normal average values as shown here for 30 March 1996. In such years, winter minimum temperatures are generally below PSC formation temperatures for long periods. (Ozone abundances are shown here with the unit “milli-Pascals” (mPa), which is a measure of absolute pressure (100 million mPa = atmospheric sea-level pressure).) 〔NOAA Aeronomy Laboratoryの『International Ozone-Layer Assessments』の『WMO/UNEP Scientific Assessment of Ozone Depletion: 2002』の『Twenty Questions and Answers About the Ozone Layer』の『III STRATOSPHERIC OZONE DEPLETION』の中の『Q11: How severe is the depletion of the Antarctic ozone layer?』から〕 南極と北極上空のオゾン層が破壊されていることを示す観測データ。フロンが犯人であるが、両極とくに南極で破壊が著しいのは極域成層圏雲が重要な役割をしていると考えられている。 |
A model of the auroral oval as seen from space overlaid on top of a visible image of Earth. The false-color reds indicate the brightest aurora and blue the dimmest. The brightest aurora is found at midnight. 〔NASAの『Mission Sections』の『Themis』の『Auroras』の中の『Substorm History--How did the theory for global substorms come about?』から〕 |