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Thermosphere
The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the thermosphere thus constitutes the larger part of the ionosphere. Taking its name from the Greek θερμός (pronounced ''thermos'') meaning heat, the thermosphere begins at about 80 km (50 mi) above sea level. At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass (see turbosphere). Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation. Temperatures are highly dependent on solar activity, and can rise to or more. Radiation causes the atmospheric particles in this layer to become electrically charged, enabling radio waves to be refracted and thus be received beyond the horizon. In the exosphere, beginning at about 600 km (375&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention ( greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Tide
Atmospheric tides are global-scale periodic oscillations of the atmosphere. In many ways they are analogous to ocean tides. Atmospheric tides can be excited by: *The regular day–night cycle in the Sun's heating of the atmosphere (insolation) *The gravitational field pull of the Moon *Non-linear interactions between tides and planetary waves. *Large-scale latent heat release due to deep convection in the tropics. General characteristics The largest-amplitude atmospheric tides are mostly generated in the troposphere and stratosphere when the atmosphere is periodically heated, as water vapor and ozone absorb solar radiation during the day. These tides propagate away from the source regions and ascend into the mesosphere and thermosphere. Atmospheric tides can be measured as regular fluctuations in wind, temperature, density and pressure. Although atmospheric tides share much in common with ocean tides they have two key distinguishing features: # Atmospheric tides are primarily ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesosphere
The mesosphere (; ) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases. This characteristic is used to define its limits: it begins at the top of the stratosphere (sometimes called the stratopause), and ends at the mesopause, which is the coldest part of Earth's atmosphere, with temperatures below . The exact upper and lower boundaries of the mesosphere vary with latitude and with season (higher in winter and at the tropics, lower in summer and at the poles), but the lower boundary is usually located at altitudes from above sea level, and the upper boundary (the mesopause) is usually from . The stratosphere and mesosphere are sometimes collectively referred to as the "middle atmosphere", which spans altitudes approximately between above Earth's surface. The mesopause, at an altitude of , separates the mesosphere from the thermosphere—the second-outermost ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kármán Line
The Kármán line (or von Kármán line ) is an attempt to define a boundary between Earth's atmosphere and outer space, and offers a specific definition set by the Fédération aéronautique internationale (FAI), an international record-keeping body for aeronautics. Defining the edge of space is important for legal and regulatory purposes since aircraft and spacecraft fall under different jurisdictions and are subject to different treaties. International law does not define the edge of space, or the limit of national airspace. The FAI defines the Kármán line as space beginning above Earth's mean sea level. This number is well above the altitude reachable by a conventional airplane and is roughly where satellites, even on very eccentric trajectories, will decay before completing a single orbit. While experts disagree on exactly where the atmosphere ends and space begins, most regulatory agencies (including the United Nations) accept the FAI Kármán line definition or some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outer Space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is . The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Obser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesopause
The mesopause is the point of minimum temperature at the boundary between the mesosphere and the thermosphere atmospheric regions. Due to the lack of solar heating and very strong radiative cooling from carbon dioxide, the mesosphere is the coldest region on Earth with temperatures as low as -100 °C (-148 °F or 173 K). The altitude of the mesopause for many years was assumed to be at around 85 km (53 mi), but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact the mesopause consists of two minima - one at about 85 km and a stronger minimum at about 100 km (62 mi). Another feature is that the summer mesopause is cooler than the winter (sometimes referred to as the ''mesopause anomaly''). It is due to a summer-to-winter circulation giving rise to upwelling at the summer pole and downwelling at the winter pole. Air rising will expand and cool resulting in a cold summer mesopause and conversely downw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Layers-en
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. Most organisms use oxygen for respiration; lightning and bacteria perform nitrogen fixation to produce ammonia that is used to make nucleotides and amino acids; plants, algae, and cyanobacteria use carbon dioxide for photosynthesis. The layered composition of the atmosphere minimises the harmful effects of sunlight, ultraviolet radiation, the solar wind, and cosmic rays to protect organisms from genetic damage. The current compos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratosphere
The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air high in the sky and the cool layers of air in the low sky, close to the planetary surface of the Earth. The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet (UV) radiation by the ozone layer. The temperature inversion is in contrast to the troposphere, near the Earth's surface, where temperature decreases with altitude. Between the troposphere and stratosphere is the tropopause border that demarcates the beginning of the temperature inversion. Near the equator, the lower edge of the stratosphere is as high as , at midlatitudes around , and at the poles about . Temperatures range from an average of near the tropopause to an average of near the mesosphere. Stratospheric temperatures also vary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermopause
The thermopause is the atmospheric boundary of Earth's energy system, located at the top of the thermosphere. The temperature of the thermopause could range from nearly absolute zero to . Below this, the atmosphere is defined to be active on the insolation received, due to the increased presence of heavier gases such as monatomic oxygen. The solar constant is thus expressed at the thermopause. Beyond (above) this, the exosphere describes the thinnest remainder of atmospheric particles with large mean free path, mostly hydrogen and helium. As a lower boundary for the exosphere this boundary is also called the exobase. The exact altitude varies by the energy inputs of location, time of day, solar flux, season, etc. and can be between high at a given place and time because of these. A portion of the magnetosphere dips below this layer as well. Although these are all named layers of the atmosphere, the pressure is so negligible that the chiefly-used definitions of outer space are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a ''perfect'' vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure. The Latin term ''in vacuo'' is used to describe an object that is surrounded by a vacuum. The ''quality'' of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) using a kite-supported antenna for reception. The transmitting station in Poldhu, Cornwall, used a spark-gap transmitter to produce a signal with a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exosphere
The exosphere ( grc, ἔξω "outside, external, beyond", grc, σφαῖρα "sphere") is a thin, atmosphere-like volume surrounding a planet or natural satellite where molecules are gravitationally bound to that body, but where the density is so low that the molecules are essentially collisionless. In the case of bodies with substantial atmospheres, such as Earth's atmosphere, the exosphere is the uppermost layer, where the atmosphere thins out and merges with outer space. It is located directly above the thermosphere. Very little is known about it due to lack of research. Mercury, the Moon, Ceres, Europa, and Ganymede have surface boundary exospheres, which are exospheres without a denser atmosphere underneath. The Earth's exosphere is mostly hydrogen and helium, with some heavier atoms and molecules near the base. Surface boundary exosphere Mercury, Ceres and several large natural satellites, such as the Moon, Europa, and Ganymede, have exospheres without a den ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
