A Simulation Study on the Variation of Thermospheric O/N2 With Solar Activity

The ratio of number density of atomic oxygen (O) to that of molecular nitrogen (N2) in the thermosphere (O/N2) on the constant pressure surface, which has complex temporal and spatial characteristics, is widely regarded as an important parameter connecting the terrestrial thermosphere and daytime ionosphere. Previous studies demonstrated that the thermospheric O/N2 increases with increasing solar activity, and the changes in O/N2 with solar activity show significant difference between winter and summer hemispheres. However, the root causes, which are responsible for the solar activity variation of O/N2, are not fully understood. In this study, the contributions of various physical and chemical processes on the response of O/N2 to the solar radiation change were quantitatively investigated through a series of controlled simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model. The simulation results suggested that the chemical processes lead to the increase of thermospheric O/N2 over the globe with increasing solar activity. The increase of O/N2 with solar activity is dominated by the enrichment of O abundance and the loss of N2 abundance in the lower and upper thermosphere, respectively. Moreover, the simulation results suggested that the stronger hemispheric asymmetry is attributed to the stronger thermospheric circulation, which changes the vertical advection of O/N2 through both direct and indirect effects.

[1]  X. Dou,et al.  Does the Peak Response of the Ionospheric F2 Region Plasma Lag the Peak of 27‐Day Solar Flux Variation by Multiple Days? , 2018, Journal of Geophysical Research: Space Physics.

[2]  X. Dou,et al.  Solar cycle variations of thermospheric O/N2 longitudinal pattern from TIMED/GUVI , 2017 .

[3]  E. Sutton.  Interhemispheric transport of light neutral species in the thermosphere , 2016 .

[4]  W. Wan,et al.  A numerical study of the interhemispheric asymmetry of the equatorial ionization anomaly in solstice at solar minimum , 2016 .

[5]  X. Dou,et al.  Can atomic oxygen production explain the ionospheric annual asymmetry? , 2016 .

[6]  S. Solomon,et al.  Solar cycle variations of thermospheric composition at the solstices , 2016 .

[7]  A. Burns,et al.  Explaining solar cycle effects on composition as it relates to the winter anomaly , 2015 .

[8]  S. Solomon,et al.  The winter helium bulge revisited , 2014 .

[9]  S. Solomon,et al.  Thermospheric Density: An Overview of Temporal and Spatial Variations , 2012 .

[10]  J. Russell,et al.  Zonal-mean global teleconnection from 15 to 110 km derived from SABER and WACCM , 2012 .

[11]  A. Burns,et al.  Wind and temperature effects on thermosphere mass density response to the November 2004 geomagnetic storm , 2010 .

[12]  Larry J. Paxton,et al.  O/N2 changes during 1–4 October 2002 storms: IMAGE SI‐13 and TIMED/GUVI observations , 2004 .

[13]  Jeffrey M. Forbes,et al.  Migrating and nonmigrating semidiurnal tides in the upper atmosphere excited by tropospheric latent heat release: MIGRATING AND NONMIGRATING SEMIDIURNAL TIDES , 2003 .

[14]  Jeffrey M. Forbes,et al.  Migrating and nonmigrating diurnal tides in the middle and upper atmosphere excited by tropospheric latent heat release , 2002 .

[15]  H. Rishbeth,et al.  Annual and semiannual variations in the ionospheric F2-layer: II. Physical discussion , 2000 .

[16]  H. Rishbeth,et al.  Semiannual and annual variations in the height of the ionospheric F2-peak , 2000 .

[17]  H. Rishbeth,et al.  Vertical circulation and thermospheric composition: a modelling study , 1999 .

[18]  Henry Rishbeth,et al.  How the thermospheric circulation affects the ionospheric F2-layer , 1998 .

[19]  Raymond G. Roble,et al.  A thermosphere/ionosphere general circulation model with coupled electrodynamics , 1992 .

[20]  T. Killeen,et al.  Processes responsible for the compositional structure of the thermosphere , 1989 .

[21]  T. Fuller‐Rowell,et al.  Diffusive equilibrium and vertical motion in the thermosphere during a severe magnetic storm : A computational study , 1987 .

[22]  Raymond G. Roble,et al.  On the global mean structure of the thermosphere , 1987 .

[23]  H. Rishbeth.  On the F2-layer continuity equation , 1986 .

[24]  R. W. Spiro,et al.  A model of the high‐latitude ionospheric convection pattern , 1982 .

[25]  Raymond G. Roble,et al.  A three‐dimensional general circulation model of the thermosphere , 1981 .

[26]  N. Spencer,et al.  Some properties of upper atmosphere dynamics , 1978 .

[27]  P. Hays,et al.  Thermospheric wind effects on the distribution of helium and argon in the Earth's upper atmosphere , 1973 .

[28]  G. King.  The Dissociation of Oxygen and High Level Circulation in the Atmosphere , 1964 .

[29]  R. Duncan.  F REGION SEASONAL AND MAGNETIC-STORM BEHAVIOUR. , 1969 .