A Comparative Study of Generalized & Classical Absorption Coefficients in D-Region at Udaipur

5-8A study or the ratio γ or the absorption coefficients (K)given by the Sen-Wyller (S-W) generalized theory and the Appleton-Hartree (A-H) classical theory has been made for the D-region for various working frequencies. An empirical relation for γ has been proposed as a function of height and working frequency, which would help one to compute the generalized absorption coefficients, simply multiplying the values of K calculated from the A-H theory by γ. It has been found that γ varies nearly from 1to 2.5 in the height range of 70-85 km and remains 2.5 for heights above 85 km. The total non-dedicative absorptions at various working frequencies have also been computed graphically

Variation of Apparent Ionospheric Height with Frequency & Observed Multiple Reflections

136-137A theoretical analysis of the effect of the apparent height gradient dh'/df in the ionosphere on the shape of the reflected pulse has been made. It has been shown that when the gradient dh'/df is high, the pulse would normally be split into two. It has been further shown that the observed four split echoes may be the result of such a gradient in the electron density in the ionosphere, when the working frequency is near the critical frequency of the region

Observed Diurnal & Frequency Variation of AI-Absorption at a Low Latitude Station & Some Ionospheric Parameters for the Lower Ionosphere

366-370An analysis is conducted on the extensive AI-technique measurements made on multi frequency ionospheric absorption at Udaipur (geogr.lat. 24'6°N; geogr. long. 73'7°E) during the period July 1974-June 1977 for five working frequencies in the range 2'3-4'1 MHz. It has been found from the analysis that the diurnal variation of absorption (L)at that latitude could be represented by the relation L = A + B cosn, The calculated overall mean values of cos index (n)for total and D-region absorption are 1'20 and 1'14, respectively. Analysis for the frequency variation of absorption at this place reveals that the frequency index (m) for D-region has a decreasing trend with cos and yields an overall mean value of 1'79, Dependence of absorption on solar activity has also been investigated. Some ionospheric parameters for the lower ionosphere have also been calculated like the effective recombination coefficient, etc

Effect of Interplanetary Magnetic Field on Apparent Drift Speed at Low Latitude Stations

201-202The effect of interplanetary magnetic field (IMF) on E and F region apparent drift speed at Udaipur (geomag. lat.. 14°33'N) and Ahmedabad (geomag. lat., 14°N) has been studied. It is found that the apparent drift in E- and F-region decreases with increasing value of IMF and the southward component (Bz). Correlation study between east-west component of drift speed and Bz. Component of IMF has also been made for summer (J-months) and winter (D-months), separately. It has been found that there is an increasing trend of eastward and decreasing trend of westward drift component With southward Bz

D-Region Model Study for Udaipur

97-99On the basis of a simplified ion-chemical scheme a D-region model is prepared. Multifrequency absorption results measured at Udaipur match with the electron density profile obtained from the scheme. The results are compared with positive ion and electron concentrations measured at the same solar zenith angle position over Thumba. The scheme used is slightly different from that of the existing ones in both negative and positive ion sides

Quiet nighttime D-region model ionization profiles

347-350An attempt has been made to obtain ion and electron density model profiles for quiet nighttime D-region using a simplified ion-chemical scheme with some modifications appropriate for nighttime conditions. Positive ion profiles for the nighttime show that the level of disappearance of cluster ions increases roughly by 5 km in nighttime, and density of NO+ at all the heights is higher than that of O. Negative ion profiles show the dominance of NO and NO and their hydrated cluster ions are compared with CO ions. Computed nighttime electron density in the present work has been compared with IRI and other theoretical models

D-region model ionization profiles during a weak solar flare and ionospheric absorption study at Udaipur

106-109An effort made to obtain ion and electron density model profiles for the D-region during a weak X-rays solar flare using a simplified ion-chemical scheme with some modifications appropriate to the flare time is described. The multi-frequency AI absorption results at Udaipur were found to match with computed absorption results using the derived electron density profile. Further, it has been found that the density of all the positive ions increases at the time of flare and the level of disappearance of water cluster ions during the flare time decreases roughly by 3 km

Dependence of Ionospheric Absorption at Udaipur on 10.7-cm Solar Flux

69-70The dependence of ionospheric absorption on solar activity during the period 1974-80at frequencies 2.3 and 2.5 MHz over Udaipur (24°35'N) has been studied. It has been found that the variation of noontime ionospheric absorption (A) with 10.7-cm solar flux may be represented in an exponential form rather than the linear one The advantage of the representation is that the observed saturation value of absorption is also accounted for