R. R. Fisher

Coronagraphic observations of an enhanced coronal region: I, Fexii and Nixv emission line data

Nine coronal emission lines representing five stages of Fe ionization and one stage of Ni were observed in an enhanced coronal region. The data from these observations are presented along with a density model of the enhanced region obtained from the FeXIII and NiXV emission line ratios as a function of position angle. The electron densities obtained from FeXIII lines range from Ne = 108 to 109 cm−3, and are slightly lower for NiXV line data. Estimates of the variation of temperature over the enhanced region are inferred from the observed line intensities.

On the distribution of material as a function of temperature in the post-flare loop system of 12 August 1970

Observations of the post-flare loop system formed after the east limb proton flare of 12 August 1970 include (a) sets of filtergrams from which photographic subtractions have been constructed and (b) spectra from which a distribution of electron density as a function of temperature for three coronal regions are derived. The filtergrams show no indications of radial velocities in excess of 80 km/s. The spectra indicate an increase in density at the tops of the loops with most of the material at a relatively cool temperature: Nε ≃ 6.0 × 1010, T = 3 × 105K. The distribution functions obtained for areas just above and just below loops indicate a lower electron density and the presence of material at high temperatures, Nε≃ 2.0 × 1010 and T ≃ 2.6 × 106K (above the loops) and Te > > 4.4 × 106K for material below the loops.

P-I-N Diode Detectors for Astronomical Photometry

The incident quantum efficiency eta(i)(lambda) and apparent noise input power (ANEP) were measured for two P-I-N photodiodes. Typical values at lambda8000 A are 0.68 x 10(-15) W and 3.3 x 10(-15) W, respectively. Several potential uses of this kind of detector for astronomical photometry and spectrometry are considered.

H

An Hα solar prominence with the characteristics of a spray was ejected in association with a bright limb flare. Knots of material were observed to a distance of more than one solar radius above the west limb of the Sun. The optical event was followed by 80 MHz emission from a type IV source which was observed moving out through several solar radii.Coronagraph observations have been used to determine the trajectories and velocities of the knots in directions perpendicular to the line of sight. After some early deceleration velocities increase to 300–500 km/sec and slowly decline with variations depending on the initial direction of outflow. We suggest that the magnetic field over the spot group is deformed by the energy of the mass motions of material fragments, some of which then continue to move outward from the Sun.

alpha

Ratios of emission line intensities are used to calculate the variation of temperature and the variation of electron density as a function of ion class for differing paths through a coronal enhancement. The data indicate (a) a peak mean electron density of 2.3 × 109 cm−3, (b) a temperature maximum greater than 2.3 × 106 K, and (c) the non-coincidence of the peak temperature and peak mean electron density. The latter demonstrates the invalidity of the assumption of symmetric models for coronal enhancements.The abundance of Ni was found to be equal to 0.045 that of Fe from the line ratio I(λ 6702)/ /I(λ 7059) and a density model based on the variation of the ratio I(λ 8024)/I(λ 6702).

CORONAGRAPH OBSERVATIONS OF A FLARE SPRAY, MARCH 1, 1969.

Monochromatic observations of a double coronal enhancement were obtained on 3 March and 17 March 1970. These data are used, along with the assumption of cylindrical symmetry, to calculate the emittance of the Fexiv 5303 Å lines as a function of height. These estimates are then used to find the electron density and the density of ions in the 2P3/2 level of the ground state as a function of height above the limb.

CORONAGRAPHIC OBSERVATIONS OF AN ENHANCED CORONAL REGION. II. TEMPERATURE AND DENSITY STRUCTURE THROUGH THE ENHANCED REGION.

Measured values for the total intensity of the continuum and the ratio of integrated intensities I(λ 5694)/I/(λ5446) are used to estimate the fraction of electrons along the line of sight contributing to the excitation of Caxv. This estimate of electron density along with an estimate of the dimension of the emitting region are used to find a value of the abundance of Ca in the solar corona. The estimated abundance is logNCa/NH = -4.35.

Green line observations of the March 1970 coronal enhancements

Characteristics of a solid Fabry-Perot interferometer used as a monochromator at the Mees Solar Observatory are described, and a test exposure of the green (λ 5303) corona over a small active region is discussed.

On the abundance of calcium in the solar corona

An isophotal map of a small coronal loop, obtained from a coronagraph observation through a solid Fabry-Perot interferometer, is used to estimate the variation of emission per unit volume and the pressure gradient at the top and sides of the loop. The magnitude of the magnetic field necessary to maintain the estimated pressure gradients is found to be ¦H2¦ = 30 G2.

On the use of a solid Fabry-Perot interferometer for coronal photography

A method is presented for subtracting two sequential images by a video technique. This procedure is applied to detect both rotational line-of-sight effects, and velocity fields around an active region (McMath plage No. 10181). The standard deviation of a velocity measurement was found to be ± 0.4 km/sec. This method appears to offer some advantages compared with the photographic subtraction process.