Determination of D-Region Electron Loss Rates and Electron Density Profiles from VLF Measurements During Solar Flare X-Ray Events

1974 ◽  
pp. 193-197 ◽  
Author(s):  
G. Bjøntegaard
Keyword(s):  
Solar Flare ◽  
Electron Density ◽  
Electron Loss ◽  
Density Profiles ◽  
X Ray ◽  
D Region ◽  
Electron Density Profiles ◽  
Loss Rates

scholarly journals Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

2008 ◽  
Vol 26 (8) ◽  
pp. 2311-2321 ◽  
Author(s):  
C.-F. Enell ◽  
P. T. Verronen ◽  
M. J. Beharrell ◽  
J. P. Vierinen ◽  
A. Kero ◽  
...  
Keyword(s):  
Solar Proton ◽  
Spectral Irradiance ◽  
Cluster Ions ◽  
Ion Chemistry ◽  
Density Profiles ◽  
X Ray ◽  
Noise Absorption ◽  
D Region ◽  
Electron Density Profiles ◽  
Cosmic Noise

Abstract. Two case studies of upper mesospheric and lower thermospheric (UMLT) high-latitude effects of solar X-ray flares are presented. Sodankylä Ion-neutral Chemistry Model (SIC) electron density profiles agree with D-region EISCAT and riometer observations, provided that the profiles of the most variable ionisable component, nitric oxide, are adjusted to compensate for NOx production during preceding geomagnetically active periods. For the M6-class flare of 27 April 2006, following a quiet period, the agreement with cosmic noise absorption observed by the Sodankylä riometers was within reasonable limits without adjustment of the [NO] profile. For the major (X17-class) event of 28 October 2003, following high auroral activity and solar proton events, the NO concentration had to be increased up to on the order of 108 cm−3 at the D-region minimum. Thus [NO] can in principle be measured by combining SIC with observations, if the solar spectral irradiance and particle precipitation are adequately known. As the two case events were short and modelled for high latitudes, the resulting neutral chemical changes are insignificant. However, changes in the model ion chemistry occur, including enhancements of water cluster ions.

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.

A direct method for determination of membrane electron density profiles on an absolute scale

Nature ◽  
1978 ◽  
Vol 276 (5687) ◽  
pp. 530-532 ◽  
Author(s):  
N. P. FRANKS ◽  
T. ARUNACHALAM ◽  
E. CASPI
Keyword(s):  
Electron Density ◽  
Direct Method ◽  
Density Profiles ◽  
Absolute Scale ◽  
Electron Density Profiles ◽  
A Direct Method

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.

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