Effect of volcanic debris on stratospheric ion conductivity

The reduction is reported of stratospheric ion conductivities in the altitude range of 20 to 27 km attributable to the aerosols injected into the stratosphere by the eruption of volcano Nevado Del Ruiz on November 13, 1985. Three balloon experiments were conducted from Hyderabad, India (17.5 N, 78.6 E) carrying a Langmuir probe payload for measuring stratospheric ion conductivities. The first flight took place about 9 months before the volcanic eruption, the second 3 weeks after the eruption and the third about a year later. Lidar observations from Japan, Hawaii and Europe reported detection of aerosol layers in the 18 to 25 km altitude range attributable to the Nevado Del Ruiz volcanic eruption. A comparison of the conductivity profiles shows that the reduction of ion conductivities is: 57.3 percent at 20 km and 31 percent at 25 km. A year after the eruption, conductivities at all heights tended to recover

Results of rocket measurements of D-region ionization over Thumba in MAP

Under MAP, two rockets were launched from Thumba (8.5 N, 76.8 E) around 1030 hrs Lt with identical payloads on 7 and 10 March 1986 for D region studies. Positive ion densities were measured by spherical probe and Gerdien condenser and electron densities were measured by Langmuir probe and propagation experiments. In both flights a valley in ionization height profile was noticed around 83 km. The density of ionization at this altitude was about 4 x 10(2) cu cm. A detailed positive ion-chemical scheme was used to reproduce the measured ionization height profiles. The density of NO needed to reproduce the valley in ionization at 83 km came around 5 x 10(5) cu cm. A photochemical treatment without diffusion process was found inadequate to explain this value of NO. Calculations showed that the value of vertical eddy diffusion needed to reproduce the value of NO was around 10(6)sq cm/s. Interestingly, the same value of eddy diffusion coefficient was obtained when derived in the manner described by Thrane and his coworkers using only the positive ion current data of spherical probes

Twenty-Five Years of Satellite Beacon Studies in India

136-151A comprehensive review of the highlights of the satellite beacon research in India during the past 25 years is presented

Study of the Lower Ionosphere Using a Rocket-borne Riometer

87-98Y. V. Somayajulu and A. P. Mitra (Scient. Rep. No. 29, Radio Science Division, National Physical Laboratory, New Delhi, 1966) proposed a rocket-borne riometer technique to derive the electron density profile by measuring the changes in cosmic noise absorption in the lower ionosphere. Using this principle a rocket-borne riometer was flown on a Nike-Apache rocket (ISRO 30.01) on 2 January, 1970 at 1212 hrs LT. Two additional experiments have been included in the same payload to measure electron density, viz. a propagation experiment and a Langmuir probe. The principle and feasibility of the new technique are described and the instrumentation and the design considerations are discussed. The flight performance and data analysis are Presented. It is found that the changes in cosmic noise absorption with altitude are consistent with the absorption changes measured by the propagation experiment in the 60-80 km altitude region. Above 85 km altitude the large electron densities cause impedance changes of the riometer antenna. The antenna detuning is utilized to estimate the electron densities in this region. Thus the flight demonstrates the scientific and technical feasibility of riometer experiment for lower ionospheric studies. The measurement accuracy is better when the D-region absorption is high, as during solar flare or PCA, etc

Rocket Measurements of D-Region Electron Densities at the Equator

81-83The D-region electron density profiles at the equator measured by rocket techniques are summarized. It is noted that these profiles are consistent with the current concepts of the ionizing sources and loss mechanisms which control the equilibrium electron densities in the D-region. However, there appease to be some discrepancy regarding the cosmic ray contribution, the actual values observed below 70 km. being somewhat higher than the expected values

Rocket Measurement of Molecular Oxygen Density in the Altitude Range 70-90 km at the Geomagnetic Equator

173-176Three instrumented rockets were flown from Thumba on 19 March 1970for measuring the concentration of molecular oxygen using absorption photometry technique. From the rocket data, the molecular oxygen density profiles were derived in the altitude range of 70-90 km. The density value derived from noon time and afternoon flights are found to be consistently lower than those given by standard atmospheric models by about 20%. These values can be made consistent with Groves’s model if the Lyman-alpha absorption cross-section of molecular oxygen is reduced by about 10% from the assumed value of 1 X 10-20 cm2. A comparison of the molecular oxygen density values for the three flights shows a possible diurnal variation with early morning value being the highest and the afternoon values the lowest

Balloon-borne Langmuir Probe Measurement of Stratospheric Ions in Low Latitudes

176-179A balloon carrying a Langmuir probe payload for measuring the positive and negative ion densities in the stratosphere was flown around midnight IST on 23 Mar 1982 from the National Balloon Facility at Hydrabad, a low latitude station. The Langmuir probe with a guard ring arrangement is given a symmetrical probe voltage of triangular waveform with amplitude ± 4.2 V and with a repetition frequency of 0.28 Hz. The balloon reached a ceiling altitude of 33km and data were taken from 15km up to the ceiling altitude. The altitude profiles of the ion density show a peak around 18km with densities decreasing with altitude. The results are discussed in terms of cosmic ray production and ion chemistry. The structures in the positive ion density profile are interpreted in terms of the presence of aerosol layers

On the Determination of Initial Polarization of Signals Transmitted by Geostationary Satellites

28-30Expressions for determining the initial polarization and ellipticity, as seen from the receiver end, of signals transmitted by geostationary satellite for different signal polarizations in the satellite-based coordinate system have been presented and discussed