The stability of coronal loops: Finite-length and pressure-profile limits

Solar Physics - Vertically propagating traveling waves have been observed in the solar photosphere. These waves have a period of 278 ± 41 seconds and a vertical phase velocity of about 2 km...     

Daily variation of the geomagnetic field in equatorial region and sector boundary passage

The mean daily range in horizontal intensity at low latitudes shows a significant departure on the day of a sector boundary passage in relation to its magnitude on adjacent days with a measure of dependence on phase of the solar activity. It is shown that this arises because of a substantial difference, in the nature of the response to sector boundary passage, between the instantaneous maximum field and minimum field. From the fact that the responses at three stations spanning the latitudes near dip equator to that near the focus of Sq currents are almost identical, it is suggested that the cause of the observed feature is primarily disturbance and is essentially non-ionospheric. Differences in the nature of responses between pre-1957 and post-1957 periods reported earlier in the planetary indices or low latitude disturbance indices are shown to be true for the daily range, maximum and minimum fields at low latitudes.     

Mars surface properties observed by earth-based radar at 70-, 12.5-, and 3.8-cm wavelengths

A review of Mars radar data obtained through the 1973 opposition confirms that the surface of the planet has many diverse characteristics. Analysis of the quasi-specular echo component shows changes in apparent reflectivity of at least 5 to 1. If attributed entirely to variations in surface material, these correspond to dielectric constants between 1.6 and 4.0. Values of rms surface slope on 1- to 100-m scales range from as low as 0.5° in tablelands near Vlles Marineris to more than 3.0° (the upper limit for which these analysis techniques are appropriate) in certain other areas such as inside Coprates Chasma itself. There is weak correlation between the small-scale surface characteristics inferred from radar and those inferred from Mariner 9 images, geologic maps derived from those images, and other remote sensing data sets. Topography, a large-scale surface characteristic for which good correlation exists between radar and other data sets, was not considered in this study. A search for guidelines which would allow extrapolation of radar properties to new areas on the basis of those studied has been singularly unsuccessful. Data obtained during the 1973 opposition at Arecibo, Goldstone, and Haystack Observatories indicate that the scattering behavior of Mars varies little over the 70- to 3.8-cm wavelength range. Comparison of 1971 and 1973 Goldstone results shows no detectable variation with time.     

High spectral resolution ground-based observations of Venus in the 450- to 1250-cm−1 region

Ground-based observations of Venus were made with a 5-cm drive Michelson interferometer during December 1970 and December 1973. The thermal emission spectrum of the central portion of the apparent disk was recorded from 450–1250 cm^?1 with an apodized spectral resolution of 0.25 cm^?1. All statistically significant sharp line absorption features in the spectrum have been identified with gaseous CO₂. Comparison between the observed spectrum and a synthetic spectrum computed from a model atmosphere, assuming gaseous CO₂ and a sulfuric acid haze as opacity sources, indicates good agreement. A broad diffuse absorption feature associated with the sulfuric acid haze is evident in the 870- to 930 cm^?1 region. With the exception of the rotational lines of the 927-cm^?1 CO₂ band, the above feature appears as a continuum down to 0.25 cm^?1 resolution. In the 750- to 1250-cm^?1 range, the spectrum exhibits moderate thermal contrast with maximum brightness temperatures of 234–238°K occurring near 825 cm^?1. These temperatures are in general agreement with previous measurements.     

The absorption of energetic electrons by argon gas

The processes by which energetic electrons lose energy in a weakly ionized gas of argon are analysed and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization and heating efficiences are computed for energies up to 200 eV absorbed in a gas with fractional ionizations varying up to 10^?2.     

Ultraviolet observations with the space telescope Glazar

Byurakan Astrophysical Observatory; SKB Granit; Geneva Observatory; Flight Control Center. Translated from Astrofizika, Vol. 32, No. 1, p. 5–13, January–February, 1990.     

On the solar origin of the thermoluminescence profile of the GT14 core

The thermoluminescence (TL) profile of the GT14 Ionian Sea core has been recently analyzed in connection with other records of solar activity. Phenomenological similarities among the TL profile, the radiocarbon record in tree-rings and the variations of the mean anuual sunspot number R _z suggest a solar control of the TL signal. In this paper we consider new readings of the TL profile of the GT14 core which were obtained at different glow temperatures. While the main spectral peaks discussed in previous papers are observed in all readings, a few new significant periodic components may now be separated from the noise background. Among these, a strong 22 yr (Hale) cycle is evident, together with a periodicity of 28.5 yr which has already been detected in the spectrum of the sunspot number series. We finally test the temporal persistency of the main TL periodic components by using a cyclogram method and we explore the effects of background noise by considering the TL profile of bleached samples.     

Time-dependentX- andY-functions for an isotropically scattering neutron transport problem in a finite slab

Expressions for time-dependentX- andY-functions for a one-speed neutron transport problem in a finite slab have been derived using a technique combining invariant imbedding method and eigenfunction expansion method. The atmosphere has been considered to scatter isotropically.     

The far UV spectrum of the O4I(n)f star ζ Puppis

A detailed list of line identifications of the far UV spectrum of the O4I(n)f star Puppis (HD 66811) in the wavelength range 1168–1984 Å recorded on 16 April, 1981 with the International Ultraviolet Explorer (IUE) is presented. The detailed analysis of the radial velocities measured in the same wavelength range is also presented.     

Planetary nebula with a neutral envelope?

IUE ultraviolet spectral recording for a low excitating planetary nebula NGC 6369 is obtained. The very strong doublet 2800 Mgii in emission as well as not less strong absorption line 2852 Mgi are discovered in the spectrum of this nebula. It is shown that the resonance line 2852 Mgi may originate only in a neutral envelope, around the nebula, consisting of neutral hydrogen, neutral magnesium, and dust particles (Hi+Mgi). The importance of this absorption line as a powerful indicator of the discovery of neutral envelopes around the planetary nebulae is outlined.The possibility of the existence of one more envelope—transition zone—immediately contacting with the bright that is ionized part of nebula (Hii+Mgii) is also shown. The transition zone consists of neutral hydrogen, ionized magnesium, and dust particles (Hi+Mgii), main parameters of this zone are also obtained (Table IV).The temperature of the central star of this nebula is obtained for the first time:T _*=48000 K. Continuous background in the interval 2600–3000 Å is identified with Balmer continuum with electron temperatureT _e =12500 K.