Security arises from the fact that as a mirror, only receivers in the correct position will hear the transmitter, much as with a real mirror, what is seen in reflection depends upon one's position with respect to the mirror. The basic idea of such a system is that such an ion trail will act as a mirror for radio waves, which can be bounced off the trail. Meteor scatter has been used for experimental secure military battlefield communications systems. When radio waves are bounced off these trails, it is called meteor scatter communication. Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in a given region, and thus ionization trails can be found in the upper atmosphere more or less continuously. Such ionization trails can last up to 45 minutes at a time. These particles might affect climate, both by scattering electromagnetic radiation and by catalyzing chemical reactions in the upper atmosphere.ĭuring the entry of a meteoroid into the upper atmosphere, an ionization trail is created, where the molecules in the upper atmosphere are ionized by the passage of the meteor. Meteor dust particles left by falling meteoroids can persist in the atmosphere for up to several months. Molten terrestrial material "splashed" from such a crater can cool and solidify into an object known as a tektite. A meteor striking the Earth or other object may produce an impact crater. If a meteor survives its transit of the atmosphere to come to rest on the Earth's surface, the resulting object is called a meteorite. It will then become brightly visible due to the heat produced by the ram pressure. The meteor section of the British Astronomical Association on the other hand has a much stricter definition, requiring the meteor to be magnitude -5 or brighter.Ī meteor is a meteoroid that has entered the earth's atmosphere. The International Meteor Organisation defines fireballs as being meteors of magnitude -3 or brighter. Since the majority of meteors are from small sand-grain size meteoroid bodies, most visible signatures are caused by electron relaxation following the individual collisions between vaporized meteor atoms and atmospheric constituents.Ī very bright meteor may be called a fireball or bolide. Photo of a burst of meteors with extended exposure timeĪ meteor is the visible path of a meteoroid that enters the Earth's (or another body's) atmosphere, commonly called a shooting star or falling star.įor bodies with a size scale larger than the atmospheric mean free path (10 cm to several meters) the visibility is due to the heat produced by the ram pressure ( not friction, as is commonly assumed) of atmospheric entry.
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