Critical level of escape

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<div class="definition"><div class="short_definition">(<br/>''Also called'' exobase, critical level.) The level in the [[atmosphere]] at which  a [[particle]] moving rapidly upward will have a [[probability]] of 1/''e'' of colliding with another particle  on its way out of the atmosphere.</div><br/> <div class="paragraph">It is also the level at which the horizontal [[mean free path]] of an atmospheric particle equals  the [[scale height]] of the atmosphere. The critical level of escape is the base of the [[exosphere]]. The  height of the critical level, which can vary from 500 to 1000 km, is strongly dependent on the  [[temperature]] of the upper [[thermosphere]], and varies diurnally and with the level of [[solar activity]].  <br/>''See'' [[cone of escape]], [[fringe region]].</div><br/> </div>
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<div class="definition"><div class="short_definition">(''Also called'' exobase, critical level.) The level in the [[atmosphere]] at which  a [[particle]] moving rapidly upward will have a [[probability]] of 1/''e'' of colliding with another particle  on its way out of the atmosphere.</div><br/> <div class="paragraph">It is also the level at which the horizontal [[mean free path]] of an atmospheric particle equals  the [[scale height]] of the atmosphere. The critical level of escape is the base of the [[exosphere]]. The  height of the critical level, which can vary from 500 to 1000 km, is strongly dependent on the  [[temperature]] of the upper [[thermosphere]], and varies diurnally and with the level of [[solar activity]].  <br/>''See'' [[cone of escape]], [[fringe region]].</div><br/> </div>
 
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Latest revision as of 16:59, 20 February 2012


[edit] critical level of escape

(Also called exobase, critical level.) The level in the atmosphere at which a particle moving rapidly upward will have a probability of 1/e of colliding with another particle on its way out of the atmosphere.

It is also the level at which the horizontal mean free path of an atmospheric particle equals the scale height of the atmosphere. The critical level of escape is the base of the exosphere. The height of the critical level, which can vary from 500 to 1000 km, is strongly dependent on the temperature of the upper thermosphere, and varies diurnally and with the level of solar activity.
See cone of escape, fringe region.

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