A mechanism for the formation of lopsided galaxies

This paper is concerned with the origin and existence of lopsided galaxies. A mechanism based on the distribution of dispersion velocities is suggested for the long-term maintenance of the lopsidedness.     

Incoherent cerenkov radiation and its amplification via the landau instability

Quite often the VLF hiss powers recorded by space probes are some orders of magnitude greater than those predicted by the theory of incoherent Cerenkov radiation. In this note we suggest that the wavegrowth via the Landau instability might satisfactorily account for the disparity between the theory and experiment.     

Palaeomagnetism of Dhar traps and drift of the subcontinent during the Deccan volcanism

Summary. Palaeomagnetic investigations were carried out on nine lava flows around the Dhar region, which constitute the northern part of the Deccan traps. The stability of remanent magnetism of these specimens was analysed by an alternating magnetic field, thermal demagnetization and memory tests. Six flows exhibited characteristic components of magnetization, with a mean direction of D =143°, I =+46° ( K = 107.1, α₉₅=5.5°). This gives a VGP located at 29° N, 67° W (δ_p=4.5°, δ_m= 7.0°). The lower site with normal magnetization and the upper five sites with reverse magnetization indicate a geomagnetic field reversal during the initial phases of Deccan volcanism in the Early Tertiary period. A rapid northward migration of about 18° in latitude and a simultaneous anticlockwise rotation of 37° is calculated for the subcontinent.     

Anisotropy characteristics of low energy cosmic ray population of solar origin

Comparison of Explorer 34 observations on solar protons in the energy range 0.7–55 MeV with similar observations from other spacecrafts show that the large field aligned anisotropies which are observed during the rise time of a flare event change to an equilibrium anisotropy coming radially from the sunward direction due to the convective removal of the solar particles. At very late times during the decay (T 4 days) the anisotropy is observed to be from a direction 45° E of the satellite-Sun line which is interpreted as indicative of positive density gradient of solar cosmic ray population. The dependence of both types of equilibrium anisotropies on the energy and the velocity of the particles and on plasma velocity are shown to be in agreement with the theoretical predictions. The amplitude of the large field aligned anisotropies observed earlier in the event is found to be independent of the rise time of the event and to vary as (Vt)^–1.Interplanetary magnetic sector crossings during a flare event, cause abrupt changes in both the amplitude and phase of the non-equilibrium anisotropy whereas they have no significant effect on equilibrium anisotropy. The effect of azimuthal density gradients on the decay time constants of flare enhancements are also examined in an attempt to understand the complicated structures, often observed, in the time intensity profiles at low energies.Part of this work was done while the author was at the University of Texas as Dallas, U.S.A.Now at the National Academy of Sciences, Washington, D.C.     

Possibility of continuous monitoring of celestial X-ray sources through their ionization effects in the nocturnal D-region ionosphere

The electron production rates in the night-time D-region arising from the transit of strong celestial X-ray sources Sco X-1, Tau X-1 and Galactic Center are estimated and compared with the ambient electron production rates resulting from other known stable agencies. Using the experimentally measured values of the night-time electron densities, the number of additional electrons/cc expected from the passage of these sources is computed. For the 164 kHz transmission from Tashkent, received at Ahmedabad, the associated enhancement in the attenuation is calculated using the full wave admittance technique of Barron and Budden. Reasonable agreement is shown to exist between the calculated values of the attenuation and those of direct observations.     

Evidence for short term changes in the intensity and spectrum of hard X-rays from Cyg X-1

The paper presents experimental evidence for the existence of fast intensity fluctuations with time scales of the order of a minute in the X-ray emission from Cyg X-1 at energies greater than 29 keV. Spectral variations over time intervals of 20–25 min are also observed in the same energy range. Whereas, similar intensity and spectral fluctuations have been reported earlier at lower energies the observations presented here is the first evidence for the existence of similar fluctuations at high energies.     

Rare gases on the Earth and in meteorites

Analysis of abundance patterns of rare gases Ne²², Ar³⁶, Kr⁸⁴ and Xe¹³⁰ on Earth and in ordinary and carbonaceous chondrites is presented. A mechanism of chemical adsorption of rare gases at the planetesimal stage during their accretion is proposed to generate the abundance pattern of the heavy rare gases on the Earth. The calculated values for Xe and Kr agree well with the observed values whereas for Ar, the agreement is poor.     

Palaeomagnetic results from two basic volcanic formations in the western Himalayas and a Phanerozoic polar wandering curve for India

Summary. We present palaeomagnetic results from the Durgapipal and Rudraprayag formations, which are basic volcanic formations in the Lesser Himalayas of Uttar Pradesh State. NRM measurements and AF demagnetization stability tests were made on specimens cored from oriented block samples collected at representative sites. Mean stable remanent magnetic directions were used for calculating the Virtual Geomagnetic Pole (VGP) positions; where necessary tectonic corrections were applied.
The virtual geomagnetic north poles were found to be located at:

• (a). 

  Durgapipal (Permian): λ _p = 10° S, L_p = 42° W;
• (b). 

  Rudraprayag (Silurian-Devonian): λ _p = 30° S, L_p = 12° W.

A new, continuous Phanerozoic apparent polar wandering curve for the Indian subcontinent has been plotted from the available palaeomagnetic data and the VGP positions reported in this paper. As a result, the gap in the Indian palaeomagnetic data from the Lower Carboniferous to the Cambrian has been partially filled. The locations of the pole positions for the two formations on the Phanerozoic polar wandering curve for the Indian subcontinent, have been found to coincide with the stratigraphic ages assigned to them on the basis of rather limited geological and palaeontological evidence.
The Cambrian and Permian poles for the Salt Range in the NW Himalayas and the Permian pole for the Kumaon Himalayas are grouped along with the pole positions of contemporaneous formations of the Peninsular Shield. The palaeomagnetic data thus suggests that the two formations are autochthonous in nature.     

Diffuse X-ray background measurements in the energy range 2–18 keV

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.     

A relationship between solar activity and frequency of natural disasters in China

The relationship between the length of the solar cycle, a good indicator of long-term change in solar activity, and natural disasters (drought, flood, and strong earthquakes) in China during the last 108 years is analyzed. The results suggest that the length of solar cycle may be a useful indicator for drought/flood and strong earthquakes. When the solar activity strengthens, we see the length of the solar cycle shorten and more floods occur in South China and frequent strong earthquakes happen in the Tibetan Plateau,but the droughts in East China as well as the strong earthquakes in Taiwan and at the western boundary of China are very few. The opposite frequencies occur when the solar activity weakens. The current study indicates that the solar activity may play an important role in the climate extremes and behavior in the lithosphere.