Day-time variations of the equivalent electron concentration in the non-sounded lower ionosphere |
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| Authors: | K B Serafimov |
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| Institution: | (1) Group for Space Physics at the Bulgarian Academy of Sciences, Moskovska 6, Sofia |
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| Abstract: | Summary Based on data on the lowest reflected frequencyf
min and on information on the lower and upper boundaries of the non-sounded lower ionosphere, an equivalent electron concentration for all concentrations below the correspondingf
min was determined. Day-time variations of the equivalent concentration are investigated, confirming that there is a cosine relation to the solar zenith angle. The power index of that relation has an outlined seasonal course with a maximum in April and October, while the absolute seasonal minimum is during the winter (the summer minimum is slightly outlined). The mean yearly values of the index are almost constant:n
N
 0.5 for solaractivity,I
1500 to 115.10–22 W Hz–1 m2. During higher activityn
N
changes correspondingly toI
1500 according to relation (12). The variations ofn
N
during high solar activity show that the altitude gradient and temperature gradient in the low ionosphere are becoming proportional toI
1500 when the solar x-ray radiation exceeds a certain level. The results obtained confirm the reliability of the method developed for employingf
min in aeronomic investigations. |
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| Keywords: | |
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