DIURNAL AND SEASONAL VARIATIONS IN D-REGION ELECTRON DENSITIES DERIVED FROM OBSERVATIONS OF CROSS MODULATION

1963 ◽  
Vol 41 (2) ◽  
pp. 271-285 ◽  
Author(s):  
R. E. Barrington ◽  
E. V. Thrane ◽  
B. Bjelland
Keyword(s):  
Electron Density ◽  
Average Density ◽  
Density Profiles ◽  
Lyman Alpha ◽  
Cross Modulation ◽  
Rapid Changes ◽  
Theoretical Predictions ◽  
D Region ◽  
Average Electron ◽  
Electron Density Profiles

Pulsed cross modulation, arising in the region from 60 to 80 km, has been observed during undisturbed days in the spring, summer, and fall of 1960. The manner in which these observations were obtained and the uncertainties associated with the electron-density profiles determined from them are discussed.Average electron-density profiles for each hour of quiet spring days have been deduced. These show that the most rapid changes in electron density occur within one hour of ground sunrise and sunset. Around sunrise a rather uniform layer of about 100 electrons/cc is created almost simultaneously throughout the entire region from 60 to 80 km. As the day progresses, the average electron density between 70 and 80 km changes by a factor of about 10, while the average density between 60 and 70 km changes by only a factor of 2.These features of the D region are discussed in the light of theoretical predictions which assume that cosmic rays and solar Lyman-alpha radiation account for the normal ionization in this region.

scholarly journals Electron density profiles in the quiet lower ionosphere based on the results of modeling and experimental data

2012 ◽  
Vol 30 (9) ◽  
pp. 1345-1360 ◽  
Author(s):  
V. Barabash ◽  
A. Osepian ◽  
P. Dalin ◽  
S. Kirkwood
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Lower Ionosphere ◽  
Ionization Rate ◽  
Number Density ◽  
Density Profiles ◽  
Oxide Concentration ◽  
D Region ◽  
Nitric Oxide Concentration ◽  
Electron Density Profiles

Abstract. The theoretical PGI (Polar Geophysical Institute) model for the quiet lower ionosphere has been applied for computing the ionization rate and electron density profiles in the summer and winter D-region at solar zenith angles less than 80° and larger than 99° under steady state conditions. In order to minimize possible errors in estimation of ionization rates provided by solar electromagnetic radiation and to obtain the most exact values of electron density, each wavelength range of the solar spectrum has been divided into several intervals and the relations between the solar radiation intensity at these wavelengths and the solar activity index F10.7 have been incorporated into the model. Influence of minor neutral species (NO, H2O, O, O3) concentrations on the electron number density at different altitudes of the sunlit quiet D-region has been examined. The results demonstrate that at altitudes above 70 km, the modeled electron density is most sensitive to variations of nitric oxide concentration. Changes of water vapor concentration in the whole altitude range of the mesosphere influence the electron density only in the narrow height interval 73–85 km. The effect of the change of atomic oxygen and ozone concentration is the least significant and takes place only below 70 km. Model responses to changes of the solar zenith angle, solar activity (low–high) and season (summer–winter) have been considered. Modeled electron density profiles have been evaluated by comparison with experimental profiles available from the rocket measurements for the same conditions. It is demonstrated that the theoretical model for the quiet lower ionosphere is quite effective in describing variations in ionization rate, electron number density and effective recombination coefficient as functions of solar zenith angle, solar activity and season. The model may be used for solving inverse tasks, in particular, for estimations of nitric oxide concentration in the mesosphere.

D-region electron density profiles during auroras

1964 ◽  
Vol 69 (13) ◽  
pp. 2857-2860 ◽  
Author(s):  
G. M. Lerfald ◽  
C. G. Little ◽  
R. Parthasarathy
Keyword(s):  
Electron Density ◽  
Density Profiles ◽  
D Region ◽  
Electron Density Profiles

scholarly journals The influence of ozone concentration on the lower ionosphere – modelling and measurements during the 29–30 October 2003 solar proton event

2009 ◽  
Vol 27 (2) ◽  
pp. 577-589 ◽  
Author(s):  
A. Osepian ◽  
S. Kirkwood ◽  
P. Dalin
Keyword(s):  
Electron Density ◽  
Ozone Concentration ◽  
Negative Ions ◽  
Solar Proton ◽  
Proton Event ◽  
Ion Chemistry ◽  
Density Profiles ◽  
Proton Fluxes ◽  
D Region ◽  
Electron Density Profiles

Abstract. A numerical model of D-region ion chemistry is used to study the influence of the ozone concentration in the mesosphere on ion-composition and electron density during solar proton events (SPE). We find a strong sensitivity in the lower part of the D-region, where negative ions play a major role in the ionization balance. We have chosen the strong SPE on 29–30 October 2003 when very intense proton fluxes with a hard energetic spectrum were observed. Deep penetration into the atmosphere by the proton fluxes and strong ionisation allows us to use measurements of electron density, made by the EISCAT 224 MHz radar, starting from as low as 55 km. We compare the electron density profiles with model results to determine which ozone concentration profiles are the most appropriate for mesospheric altitudes under SPE conditions. We show that, during daytime, an ozone profile corresponding to depletion by a factor of 2 compared to minimum model concentrations for quiet conditions (Rodrigo et al., 1986), is needed to give model electron density profiles consistent with observations. Simple incorporation of minor neutral constituent profiles (NO, O and O3) appropriate for SPE conditions into ion-chemistry models will allow more accurate modeling of electron and ion densities during such events, without the need to apply a complete chemical model calculating all neutral species.

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