Examining the specific entropy (density of adiabatic invariants) of the outer electron radiation belt

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Using temperature and number-density measurements of the energetic-electron population from multiple spacecraft in geosynchronous orbit, the specific entropy S = T/n{sup 2/3} of the outer electron radiation belt is calculated. Then 955,527 half-hour-long data intervals are statistically analyzed. Local-time and solar-cycle variations in S are examined. The median value of the specific entropy (2.8 x 10{sup 7} eVcm{sup 2}) is much larger than the specific entropy of other particle populations in and around the magnetosphere. The evolution of the specific entropy through high-speed-stream-driven geomagnetic storms and through magnetic-cloud-driven geomagnetic storms is studied using superposed-epoch analysis. For high-speed-stream-driven storms, systematic variations ... continued below

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Borovsky, Joseph E & Denton, Michael H January 1, 2008.

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Using temperature and number-density measurements of the energetic-electron population from multiple spacecraft in geosynchronous orbit, the specific entropy S = T/n{sup 2/3} of the outer electron radiation belt is calculated. Then 955,527 half-hour-long data intervals are statistically analyzed. Local-time and solar-cycle variations in S are examined. The median value of the specific entropy (2.8 x 10{sup 7} eVcm{sup 2}) is much larger than the specific entropy of other particle populations in and around the magnetosphere. The evolution of the specific entropy through high-speed-stream-driven geomagnetic storms and through magnetic-cloud-driven geomagnetic storms is studied using superposed-epoch analysis. For high-speed-stream-driven storms, systematic variations in the entropy associated with electron loss and gain and with radiation-belt heating are observed in the various storm phases. For magnetic-cloud-driven storms, multiple trigger choices for the data superpositions reveal the effects of interplanetary shock arrival, sheath driving, cloud driving, and recovery phase. The specific entropy S = T/n{sup 2/3} is algebraically expressed in terms of the first and second adiabatic invariants of the electrons: this allows a relativistic expression for S in terms of T and n to be derived. For the outer electron radiation belt at geosynchronous orbit, the relativistic corrections to the specific entropy expression are -15%.

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  • Journal Name: Journal of Geophysical Research

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  • Report No.: LA-UR-08-07879
  • Report No.: LA-UR-08-7879
  • Grant Number: AC52-06NA25396
  • Office of Scientific & Technical Information Report Number: 956639
  • Archival Resource Key: ark:/67531/metadc935537

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  • January 1, 2008

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  • Nov. 13, 2016, 7:26 p.m.

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  • Dec. 9, 2016, 11:29 p.m.

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Borovsky, Joseph E & Denton, Michael H. Examining the specific entropy (density of adiabatic invariants) of the outer electron radiation belt, article, January 1, 2008; [New Mexico]. (digital.library.unt.edu/ark:/67531/metadc935537/: accessed October 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.