Effects of Energetic Particles on Minor Constituents of the Middle Atmosphere

Abstract

Both energetic protons and electrons can produce odd nitrogen compounds, NO_y (N, NO, NO₂, NO₃, N₂O₅, HNO₃, HNO₄, ClONO₂), through interactions with the background atmosphere. The long lifetime of the NO_y family (up to several months in the middle atmosphere) as well as the NO_y species' significant influence on stratospheric ozone abundance make the charged particle increases of NO_y important. Galactic cosmic rays produce NO_y in the lower stratosphere, solar protons produce NO_y in the middle and upper stratosphere as well as the mesosphere, and relativistic electrons produce NO_y in the upper stratosphere and mesosphere, each affecting the NO_y middle atmosphere budget directly. Production of NO_y constituents by solar protons has been associated with an observed polar ozone depletion during and after the August 1972 solar proton event and a polar NO increase after the July 1982 solar proton event. Auroral electron and photoelectron production of NO_x (N, NO, NO₂) in the thermosphere and its subsequent transport downwards to the polar mesosphere and upper stratosphere is an important component of the NO_y budget in the middle atmosphere in the wintertime at high latitudes, e.g., the NO₂ enhancements measured by the limb infrared monitor of the stratosphere (LIMS) in the polar lower mesosphere and upper stratosphere during the winter of 1978-79 are thought to be caused by downward transport of NO_x.