Soft solar X-rays and solar activity

Soft X-radiation between 8–12 Å was found to be emitted from the Sun at the time of four optically-identified major systems of loop prominences. The peak emission rates and time-integrated X-ray energies are very similar for three of the events while the fourth appeared to emit X-rays only weakly. The data are not consistent with a compression-condensation model for the loops, and support the fast-proton injection model. Proton injection may take place on a long time scale.     

Polarization measurements of solar type III radio bursts at 25.3 MHz

We report the results of 1966, 1968, and 1969 polarization measurements of solar type III radio noise bursts made by recording the output of two orthogonally polarized receiving channels and subsequent digital processing of selected data. The processed data yield total intensity, degree of polarization, ellipticity, and polarization ellipse orientation at 1 second intervals. The measurements are made in a 100 Hz bandwith to minimize the influence of the propagating medium on the measurements. The mean degree of polarization was found to be about 65% in contrast to previous studies which indicated that type III events were more weakly polarized. By assuming that type III bursts are flare related we study the polarization characteristics of type III bursts as a function of the solar longitude of the related flares. The relation between type III event polarization characteristics and flare importance is also investigated. The significance of polarization measurements in studies of solar radio events is pointed out and suggestions for further theoretical research are given.     

The effect of a poloidal magnetic field on the radial and non-radial oscillations of a gaseous mass

The oscillations of a polytrope with infinite electric conductivity containing a weak internal poloidal magnetic field which is continuous with an external dipole field are examined with the aid of a variational equation. The corrections to the fundamental characteristic frequencies of the radial and non-radiall=2 pulsation modes are calculated. The magnetic field removes a degeneracy which occurs between these two modes and the resulting frequency splitting is evaluated. The relevance of the results to the known magnetic stars is briefly discussed.     

Three years statistics of simple 3 solar bursts

A plasmoid may be ejected during a flare and condensed by a radiative instability. The spectral shape of the mean fluxes of Simple 3 (or long-enduring) solar events is interpreted in terms of a thermal emission from this transient condensation in the higher levels of the solar atmosphere. This condensation is thick enough to block the radiation from the underlying S-component. This explanation fits the observed polarization changes, as well as the thermal character of the bursts time profiles. A clue for solar activity forecasting as well as for detailed studies of active sources is indicated.     

High resolution interferometric observations of Venus at three radio wavelengths

We present new 6.0 and 21.1 cm interferometric observations of Venus. When combined with our previous 3.12 cm work they provide s self-consistent set of high-resolution observations at three wavelengths covering a range in which the opacity of the Venus atmosphere varies by a factor of 50. Model calculations indicate that a model atmosphere of CO₂ in adiabatic equilibrium containing uniformly mixed gaseous absorbers surrounding a dielectric sphere cannot simultaneously and adequately predict the radio interferometric measurements at all wavelengths together with the radar and radio occultation measurements.     

On the interpretation of the “inverse phase effect” for CO2 equivalent widths on Venus

Computations of the equivalent widths of absorption lines as a function of planetary phase angle are made for a homogeneous cloud with particles having the properties (shape, refractive index, and size distribution) deduced from polarimetry of Venus. The computed equivalent widths show an “inverse phase effect” comparable to that which is observed for CO₂ lines on Venus. This result verifies a recent suggestion of Regas et al. that the existence of an inverse phase effect does not by itself imply the presence of multiple layers of scattering particles in the atmosphere of Venus.     

Upper atmospheric temperatures from Doppler line widths—V. Auroral electron energy spectra and fluxes deduced from the 5577 and 6300 Å atomic oxygen emissions

This is a report upon further data obtained from the auroral OI 5577 Å emission with a Wide Angle Michelson Interferometer (WAMI), and upon our first observations made with it on the 6300 Å emission. The method used for converting emission intensities and temperatures to auroral electron fluxes and energy spectra is described. Data for the 5577 Å emission are presented for the (lack of) heating in auroral forms, vertical temperature profiles in aurora, electron flux and energy spectrum variations in pulsating aurora, and a ‘cold’ subvisual auroral arc. Data from the OI 6300 Å emission are presented for the diurnal variation of exospheric temperature and for the thermalization of $\text{O}\text{(}{}^1\text{D)}$ in the F-region.     

Theoretical ion densities in the lower ionosphere

We have solved the coupled momentum and continuity equations for NO⁺, O₂⁺, and O⁺ions in the E- and F-regions of the ionosphere. This theoretical model has enabled us to examine the relative importance of various processes that affect molecular ion densities. We find that transport processes are not important during the day; the molecular ions are in chemical equilibrium at all altitudes. At night, however, both diffusion and vertical drifts induced by winds or electric fields are important in determining molecular ion densities below about 200 km. Molecular ion densities are insensitive to the O⁺ density distribution and so are little affected by decay of the nocturnal F-region or by processes, such as a protonospheric flux, that retard this decay. The O⁺ density profile, on the other hand, is insensitive to molecular ion densities, although the O⁺ diffusion equation is formally coupled to molecular ion densities by the polarization electrostatic field. Nitric oxide plays an important role in determining the NO⁺ to O₂⁺ ratio in the E-region, particularly at night. Nocturnal sources of ionization are required to maintain the E-region through the night. Vertical velocities induced by expansion and contraction of the neutral atmosphere are too small to affect ion densities at any altitude.     

Equivalent width of interstellar molecular lines

We have made an analysis of the observed equivalent widths of the lines of Lyman and Werner bands by Smith. The H₂ column densities of 3×10¹⁹ to 10²⁰ and the excitation temperature of 80 to 150 K satisfy the observations. This temperature refers to the kinetic temperature. We have also discussed the importance of getting the excitation temperature from lines of H₂ and other heteronuclear diatomic molecules for the same star and from different regions of space.