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An Overview of the Impact of Energetic Particle Precipitation on the Mesosphere and StratosphereEnergetic precipitating particles (EPPs) can cause significant constituent changes in the polar mesosphere and stratosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The HO, increases can lead to ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx,-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. The HOx,-caused ozone depletion has been observed during several solar proton events (SPEs) in the past 40 years. HOx enhancements due to SPEs were confirmed by observations in the past solar cycle. A number of modeling studies have been undertaken over this time period that show predictions of enhanced HO, accompanied by decreased ozone due to energetic particles. The NO, family has a longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone promptly, if produced in the stratosphere, or subsequently, if produced in the 1ow.er thermosphere or mesosphere and transported to the stratosphere. NOx enhancements due to auroral electrons, medium and high energy electrons, relativistic electron precipitation (REP) events, and SPEs have been measured and/or modeled for decades Only a small number of SPEs (less than 10) in each solar cycle have sufficient flux of high energy protons (greater than 30 MeV) to produce a significant amount of NOx directly in the stratosphere to cause a measurable ozone destruction. Very high energy electrons (greater than 1500 keV) during REP events can also produce NOx directly in the stratosphere, however, the frequency and intensity of these electrons is uncertain. Indirect stratospheric EPP effects result when NO, is produced in the mesosphere and lower thermosphere and transported to the stratosphere during the late fall or winter. Such EPP-produced NOx may last up to months beyond its initial production. This EPP-produced mesospheric and lower thermospheric NOx primarily results from auroral electrons (approx. 1- 30 keV), medium- and high-energy electrons (approx. 30-1500 keV), and medium energy protons (approx. 1-30 MeV). The EPP-caused direct and indirect effects on the stratosphere are important in the polar regions during particular years, especially near solar maximum. This talk will attempt to provide an overview of several of the EPP-related important processes and their impact on the mesosphere and stratosphere. Much progress has been made in this field in the past several years and it is anticipated that other workshop participants will address aspects of this topic in their presentations.
Document ID
20080023256
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Jackman, Charles H.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
May 28, 2008
Subject Category
Earth Resources And Remote Sensing
Meeting Information
Meeting: 1st International High-Energy Particle Precipitation in the Atmosphere (HEPPA) Workshop 2008/Finnish Meteorological Institute
Location: Helsinki
Country: Finland
Start Date: May 28, 2008
End Date: May 31, 2008
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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