Extreme ultraviolet spectra of solar active regions and their analysis

Extreme ultraviolet spectra of several active regions are presented and analyzed. Spectral intensities of 3 active regions observed with the NRL Skylab XUV spectroheliograph (170–630 Å) are derived. From this data density sensitive line ratios of Mg viii, Si x, S xii, Fe ix, Fe x, Fe xi, Fe xii, Fe xiii, Fe xiv, and Fe xv are examined and typically yield, to within a factor of 2, electron pressures of 1 dyne cm^–2 (n _e T = 6 × 10¹⁵ cm^–3 K). The differential emission measure of the brightest 35 × 35 portion of an active region is obtained between 1.4 × 10⁴ K and 5 × 10⁶ K from HCO OSO-VI XUV (280–1370 Å) spectra published by Dupree et al. (1973). Stigmatic EUV spectra (1170–1710 Å) obtained by the NRL High Resolution Telescope and Spectrograph (HRTS) are also presented. Doppler velocities as a function of position along the slit are derived in an active region plage and sunspot. The velocities are based on an absolute wavelength scale derived from neutral chromospheric lines and are accurate to ±2 km s^–1. Downflows at 10⁵ K are found throughout the plage with typical velocities of 10 km s^–1. In the sunspot, downflows are typically 5 to 20 km s^–1 over the umbra and zero over the penumbra. In addition localized 90 and 150 km s^–1 downflows are found in the umbra in the same 1 × 1 resolution elements which contain the lower velocity downflows. Spectral intensities and velocities in a typical plage 1 resolution element are derived. The velocities are greatest ( 10 km s^–1) at 10⁵ K with lower velocities at higher and lower temperatures. The differential emission measure between 1.3 × 10⁴ K and 2 × 10⁶ K is derived and is found to be comparable to that derived from the OSO-VI data. An electron pressure of 1.4 dynes cm^–2 (n _e T = 1.0 × 10¹⁶ cm^–3 K) is determined from pressure sensitive line ratios of Si iii, O iv, and N iv. From the data presented it is shown that convection plays a major role in determining the structure and dynamics of the active region transition zone and corona.     

The masers of E-type methanol in orion KL and SGR B2

Using a simplified model the statistical equilibrium and radiative transfer equations of E-type-CH₃OH are solved for Orion KL and SgrB2. According to our calculation results and the observation data taken by Matsakiset al. (1980) and Morimotoet al. (1985a, b), the physical conditions of both sources are estimated. In theJ ₂-J ₁ E methanol maser region of Orion KL, the density, kinetic temperature, dust temperature, and the fractional abundance are 0.8–2×10⁶ cm^–3, 150, 30–90 K, 0.8–8×10^–6. In the 4_–1-3₀ E and 5_–1-4₀ E methanol maser region of Sgr B2 the correspondance physical conditions above are 10⁴ cm³, 45, 23 K, and 7×10^–7, respectively.     

Soft x-ray emitting regions in the solar corona

The soft X-ray emission of the solar corona is investigated by comparison of the signals of several broad band photometers carried on the Solrad 9 satellite, and sensitive to the region 0.5–20 Å. Temperature from 1.5 × 10⁶ to 25 × 10⁶ K have been measured with emission measure N _e ² dV ranging between 10⁵⁰ cm^–3 to 10⁴⁷ cm^–3.By means of the observational data and assuming magnetic confinement and hydrostatic equilibrium, the model of an active region is investigated. For temperatures larger than 10⁷K the emission is due to flare activity and two sets of emission measure are observed which appear to be related to the evolution of flares.     

A possible interpretation of the optical spectrum for BL Lac-type objects

On the basis of Sobolev's method, the population of 30 levels of hydrogen atom is determined allowing for the radiative and collision processes of the heating and ionization of the medium with velocity gradient gradv=10^–9–10^–11s^–1, electron temperatureT _e=10⁴ K-2×10⁴ K and electron densityN _e=10¹⁰ cm^–3–10¹¹ cm^–3. The central source radiation is characterized by a power spectrum with spectral indices varying from 0 to 2. A region of possible physical conditions is found where the thermal diffuse radiation of the envelope exceeds the emission in the Balmer H line.     

An expanding circumstellar cloud of Zeta Aurigae

Strong absorption satellite lines of CaI 6572 were found on spectrograms taken on three successive days just after the fourth contact of the 1971–72 eclipse of Zeta Aurigae. The radial velocities of the satellite lines are –88 km s^–1, –74 km s^–1, and –180 km^–1, respectively, relative to the K-type primary star (K4 Ib). These absorptions should be due to a circumstellar cloud in which the column density of neutral calcium atoms is 1×10¹⁷ cm^–2 and the turbulent velocities come to 20–50 km s^–1. It is suggested that the cloud may be formed by the rocket-effect of the Lyman quanta of the B-type component (B6 V). We estimate the density in the cloud to be 2×10¹¹ atoms cm^–3 fors=10R _K and 2×10¹⁰ atoms cm^–3 fors=10² R _K, wheres denotes the distance of the cloud from the K star andR _K the K star's radius. The mass loss rate of the K-type component is also estimated to be about 10^–7 M yr^–1, assuming that the expansion of the K star occurs isotropically.     

Power spectra of the interplanetary magnetic field

Power spectra based on Pioneer 6 interplanetary magnetic field data in early 1966 exhibit a frequency dependence of f ^–2 in the range 2.8 × 10^–4 to 1.6 × 10^–2 cps for periods of both quiet and disturbed field conditions. Both the shape and power levels of these spectra are found to be due to the presence of directional discontinuities in the microstructure (< 0.01 AU) of the interplanetary magnetic field. Power spectra at lower frequencies, in the range of 2.3 × 10^–6 to 1.4 × 10^–4 cps, reflect the field macrostructure (> 0.1 AU) and exhibit a frequency dependence roughly between f ^–1 and f ^–3/2. The results are related to theories of galactic cosmic-ray modulation and are found to be consistent with recent observations of the modulation.     

Radio emission of the NGC 1499 nebula at decametric wavelengths

Observations of the ionized hydrogen region NGC 1499 have been carried out with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20 and 25 MHz. The half-power resolution of the instrument to zenith is 28×34 at 25 MHz. The average volume density of the non-thermal radio emission between the Sun and the nebula (1.75×10^–40 W m^–3 Hz^–1 ster^–1 at 25 MHz), the electron temperature of the HII nebula (T _e =4400 K), the measure of emission (ME=1500 cm^–6 pc) and other parameters have been obtained. Maps of brightness distribution over the source are presented for each observation frequency. The results are compared with previously obtained data.     

An empirically derived lunar gravity field

The heat-flow experiment is one of the Apollo Lunar Surface Experiment Package (ALSEP) instruments that was emplaced on the lunar surface on Apollo 15. This experiment is designed to make temperature and thermal property measurements in the lunar subsurface so as to determine the rate of heat loss from the lunar interior through the surface. About 45 days (1 1/2 lunations) of data has been analyzed in a preliminary way. This analysis indicates that the vertical heat flow through the regolith at one probe site is 3.3 × 10^–6 W/cm² (±15%). This value is approximately one-half the Earth's average heat flow. Further analysis of data over several lunations is required to demonstrate that this value is representative of the heat flow at the Hadley Rille site. The mean subsurface temperature at a depth of 1 m is approximately 252.4K at one probe site and 250.7K at the other. These temperatures are approximately 35K above the mean surface temperature and indicate that conductivity in the surficial layer of the Moon is highly temperature dependent. Between 1 and 1.5m, the rate of temperature increase as a function of depth is 1.75K/m (±2%) at the probe 1 site. In situ measurements indicate that the thermal conductivity of the regolith increases with depth. Thermal-conductivity values between 1.4 × 10^–4 and 2.5 × 10^–4 W/cm K were determined; these values are a factor of 7 to 10 greater than the values of the surface conductivity. If the observed heat flow at Hadley Base is representative of the moonwide rate of heat loss (an assumption which is not fully justified at this time), it would imply that overall radioactive heat production in the Moon is greater than in classes of meteorites that have formed the basis of Earth and Moon bulk composition models in the past.Lamont-Doherty Geological Observatory Contribution Number 1800.     

Observations of the Rosette nebula NGC 2237 at decametric wavelengths

The results of observations of the Rosette emission nebula NGC 2237 with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20.0 and 25.0 MHz are given in the shape of contours of constant brightness temperature. The half-power beamwidth of the telescope to zenith at 25.0 MHz was 28×38. Density weighted mean values for the non-thermal radio emissivity between the Sun and the source (7.9×10^–41 W m^–3 Hz^–1 ster^–1 at 25.0 MHz) and the ratio of the intensity of emissivity generated before the area and the intensity of galactic radio emissivity appearing beyond the area equal to 1.3 have been obtained. The electron temperatureT _e=3600 K, the optical depth (about ten at 25 MHz), the measure of emission (ME=3500 cm^–6 pc), the electron densityN _e=8 cm^–3 and the nebular mass 16.6×10⁺³ M have been determined. A comparison with other observation results has been made.     

Coronal survey in X-rays of O vii and Ne ix

We report some results of a rocket experiment flown on 29 April, 1971. A survey of the solar corona was carried out with a pair of collimated Bragg spectrometers to study the resonance, intersystem and forbidden line emission from the helium-like ions O vii (22 Å) and Ne ix (13 Å). In the direction of dispersion the collimator provided a field of view of 1.7. Also, the continuum radiation near 3 Å was monitored by a collimated proportional counter within a view angle of 4.2. The observed X-ray emission came from the general corona, seven plage regions, and one dynamic feature- the late stage of a small flare. From the intensity of the O vii and Ne ix resonance lines the electron temperature and emission measure of the individual emitting regions are derived on the basis of two models, one (a) in which the region is assumed to be isothermal and another (b) in which the emission measure decreases exponentially with increasing temperature. The latter model, which is the most adequate of the two, yields for the electron temperature of the time-varying feature 2–3 × 10⁶ K, for the other active regions 1.5–2.5 × 10⁶ K, and for the general corona 1.3–1.7 × 10⁶ K. The Ne ix emitting regions are about 1.5 times as hot as the O vii regions. The emission measure ranges from 0.4–2.3 × 10⁴⁸ cm^–3 for all active regions and is about 2 × 10⁴⁹ cm^–3 for one hemisphere of the general corona above 10⁶ K. From an analysis of the ratio, R, of the forbidden and intersystem lines of O vii we conclude that none of the regions producing these lines at the time of the rocket flight had electron densities exceeding about 3 × 10⁹ cm^–3. Our data demonstrate a dependence of R upon temperature in agreement with the theory of Blumenthal et al. (1971). The wavelengths for the intersystem, the 1s ²2s ² S ^e–1s2p2s ² P ⁰ satellite, and the forbidden transition show in the case of Ne ix improved agreement with predictions. The observed strength of the satellite lines for both O vii and Ne ix agrees with the predictions of Gabriel's (1972) theory, which attributes their formation to dielectronic recombination.We are saddened to report the death of A. J. Meyerott on 13 November, 1971.     

The coronal and transition region temperature structure of a solar active region

Using measurements of EUV and X-ray spectral lines we derive the differential emission measure vs electron temperature T from the transition region to the corona of an active region (10⁵ T <5 × 10⁶ K). The total emission measure and radiative losses are of order 3 × 10⁴⁸ cm^–3 and 4 × 10²⁶ ergss^–1 respectively. The emission measure at T > 10⁶ K (i.e. that mainly responsible for the X-ray emission) is about 75% of the total. We also examine the use of Mg x 625 Å as an indicator of coronal electron density. A set of theoretical energy balance models of coronal loops in which the loop divergence is a variable parameter is presented and compared with the observations. Particular attention is given to the limitations inherent in any such comparison.     

The synthesis of26Al during combined hydrogen and helium-burning reactions

We have studied the synthesis of²⁶Al during combined hydrogen and helium-burning processes in high temperature and density conditions. The possible sites for these processes are believed to be the neutron star surfaces where the density ranges from =10⁴–10⁷ g cm^–3 and temperature range from 10⁸–8×10⁸ K. The screening effect which leads to an enhancement of nuclear reaction rates is taken into account whenever necessary. A detailed calculation of the abundances of²⁶Al and²⁷Al isotopes is presented here. Finite amounts of²⁶Al is found to be produced atT=2×10⁸ K and =10⁸ g cm^–3 due to these combined reactions. This situation is likely to be realized during the -ray burst events on neutron star surface. The amount of material processed in the burst sources is very little compared to the amount of material processed in Novae or Supernovae. Thus it is suggested that rather than contributing to the overall amount of²⁶Al, -ray bursts are likely to contribute more significantly to the inhomogeneity of²⁶Al distribution in interstellar medium.     

On the accelerations of the Moon and Sun,the constant of gravitation,and the origin of mountains

In a previous paper Lyttleton (1976) has shown that the apparent secular accelerations of the Sun and Moon, as given by de Sitter, can be largely explained if the Earth is contracting at the rate required by the phase-change hypothesis for the nature of the core. More reliable values for these accelerations have since become available which warrant a redetermination of the various effects concerned on the basis of constantG, and this is first carried out in the present paper. The lunar tidal couple, which is the same whetherG is changing or not, is found to be (4.74±0.38)×10²³ cgs, about three-quarters that yielded by the de Sitter values, while within the theory the Moon would take correspondingly longer to reach close proximity to the Earth at about 1.5×10⁹ years ago.The more accurate values of the accelerations enable examination to be made of the effects that a decreasingG would have, and it is shown that a valueG/G=–3×10^–11 yr^–1 can be weakly satisfied compared with the close agreement found on the basis of constantG, while a value as large numerically asG/G=–6×10^–11 yr^–1 seems to be definitely ruled out. On the iron-core model, an intrinsic positive component of acceleration of the angular velocity cannot be reconciled at all with the secular accelerations even for constantG, and far less so ifG is decreasing at a rate suggested by any recent cosmological theory.ItG=0, the amount of contraction available for mountain-building would correspond to a reduction of surface area of about 49×10⁶ km² and a volume to be redistributed of 160×10⁹ km³ if the time of collapse were 2.5×10⁹ years ago. For earlier times, the values are only slightly reduced. IfG/G=–3×10^–11 yr^–1, the corresponding values are 44×10⁶ km² and 138×10⁹ km³ for collapse at –2.5×10⁹ yr, and not importantly smaller at 38×10⁶ km² and 122×10⁹ km³ for collapse at –4.5×10⁹ yr. Any of these values would suffice to account in order of magnitude for all the eras of mountain-building. An intense brief period of mountain-building on an immense scale would result from the Ramsey-collapse at whatever time past it may have occurred.     

Estimation of an upper limit for the solar neutron emission during large flares

Solar neutron emission during large flares is investigated by using neutron monitor data from the mountain stations Chacaltaya (Bolivia), Mina Aguilar (Argentine), Pic-du-Midi (France) and Jungfraujoch (Switzerland). Registrations from such days on which large flares appeared around the local noon time of the monitor station are superimposed with the time of the optical flare as reference point.No positive evidence for a solar neutron emission was found with this method, However, by using an extrapolation of the neutron transport functions given by Alsmiller and Boughner a rough estimation of mean upper limits for the solar neutron flux is possible. The flux limits are compared with Lingenfelter's model calculations.From the Chacaltaya measurements it follows: N ₀2.8 × 10^{–3 N} cm^–2 s^–1 per proton flare, E > 50 MeV, if P0 = 125 MV N ₀1.4 × 10^{–2 N} cm^–2 s^–1 per proton flare, E > 50 MeV, if P ₀ = 60 MV and from Pic-du-Midi measurements: N ₀6.7 × 10^{–3 N} cm^–2 s^–1 per proton flare, E > 50 MeV, if P ₀ = 125 MV N ₀4 × 10^{–2 N} cm^–2 s^–1 per proton flare, E > 50 MeV, if P ₀ = 60 MV P ₀ = characteristic rigidity of the producing proton spectrum on the Sun.The flux limits estimated for some special proton flares are consistent with Lingenfelter's predictions for the acceleration phase but are too small for the slowing down phase. Therefore it is believed that Lingenfelter's assumption of isotropic proton emission from the flare region is not fulfilled.     

Primary production and microbial activity in the euphotic zone of Lake Baikal (Southern Basin) during late winter

Three years of regular weekly/biweekly monitoring of seasonal changes in temperature, transparency, chlorophyll a (CHL) and bacteria [erythrosine-stained microscopic counts and cultivable colony forming units (CFUs)] at the vertical profile in the South basin of Lake Baikal (51°54′195″N, 105°04′235″E, depth 800 m) were evaluated. In more detail, the structure and function of phytoplankton and the microbial loop in the euphotic layer at the same site were investigated during the late-winter–early-spring period under the ice. The depth of euphotic zone (up to 1% of surface irradiation) was 35 to 40 m. Primary production was measured three times a week with the ¹⁴C method in 2, 10, 20, 30 and 40 m. Maximum production was found in 10 m, with lower values towards the surface (light inhibition) and towards the lower layers. The total production in cells larger than 1 μm in the column (0–40 m) was 204–240 mg C d⁻¹ m⁻², 30–40% of it being in cells 1–3 μm (mostly picocyanobacteria), which represented roughly 9% of the total chlorophyll a (estimated from pigment analyses). A major part of phytoplankton biomass was formed by diatoms (Synedra acus Hust., Asterionella formosa Hass. and Stephanodiscus meyerii Genkal & Popovskaya). Total production (including extracellular, dissolved organic matter) was 235–387 mg C day⁻¹ m⁻², and the exudates were readily used by bacteria (particles 0.2–1 μm). This part amounted to 1–5% of cellular production in 2 to 20 m and 11–77% of cellular production in 20–40 m, i.e., in light-limited layers. From 0 to 30 m, chlorophyll a concentration was 0.8 to 1.3 μg l⁻¹, wherefrom it decreased rapidly to 0.1 μg l⁻¹ towards the depth of 40 m. Bacteria (DAPI-stained microscopic counts) reached 0.5–1.4×10⁶ ml⁻¹; their cell volumes measured via image analysis were small (average 0.05 μm⁻³), often not well countable when erythrosine stain was used. Bacterial biomasses were in the range of 6–21 μg C l⁻¹. Numbers of colony forming units (CFUs) on nutrient fish-agar were c. 3–4 orders lower than DAPI counts. The amounts of heterotrophic protists were low, whereby flagellates reached 6 to 87 ml⁻¹ and ciliates, 0.2–1.2 ml⁻¹ (mostly Oligotrichida). Bacterial production was measured in the same depths as primary production using ³H-thymidine (Thy) and ¹⁴C-leucine (Leu) uptake. Consistently, bacterial abundances, biomasses, thymidine and leucine production were higher by 30–50% in layers 2, 10 and 20 m compared with that in the deeper 30 and 40 m, where cellular primary production was negligible. Leucine uptake in the deeper layers was even three times lower than in the upper ones. From the comparison of primary and bacterial production, bacteria roughly use 20–40% of primary production during 24 h in the layers 2 to 20 m.     

The application of a non-static spherically-symmetric metric to clusters of galaxies

An approximate metric is found which represents a sphere of matter embedded in a background of dust. The use of this metric in conjunction with the Friedmann equations gives values of for the three possible values ofk as +6×10^–36 (k=+1), +3×10^–35 (k=0), +10^–36 (k=–1). These values depend on data regarding clusters of galaxies, and are probably accurate to within an order of magnitude given the correctness of the assumptions on which their derivation rests.     

Luminosity function for galaxies and cosmology

Formulae for two classical cosmological tests,N(z) andN(m) are obtained with the luminosity function taken into account. From the testN(m) and Jarvis and Tyson observational data, characteristic absolute magnitude of galaxiesM ^*=–20.05 and mean extragalactic absorptionA=4×10^–4 mag Mpc^–1 have been found.     

Large-Scale Structure of the Atmosphere of the Quiet Sun,Coronal Holes,and Plages as Deduced by Tomography Study

We present here the results of emission tomography studies, based on a new differential deconvolution method (DDM) of Laplace transform inversion, which we use for reconstruction of the coronal emission measure distributions in the quiet Sun, coronal holes and plage areas. Two methods are explored. The first method is based on the deconvolution of radioemission brightness spectra in a wide wavelength range (1 mm–100 cm) for temperature profile reconstructions from the corona to the deeper chromosphere. The second method uses radio brightness measurements in the cm–dm range to give a coronal column emission measure (EM).Our results are based on RATAN-600 observations in the range 2.0–32 cm supplemented by the data of other observatories during the period near minimum solar activity. This study gives results that agree with known estimates of the coronal EM values, but reveals the absence of any measurable quantities of EM in the transition temperature region 3 × 10⁴ –10⁵ K for all studied large-scale structures. The chromospheric temperature structure (T _e = 20,000–5800 K) is quite similar for all objects with extremely low-temperature gradients at deep layers.Some refraction effects were detected in the decimeter range for all Types of large-scale structures, which suggests the presence of dense and compact loops (up to N _e =(1–3)× 10⁹ cm^-3 number density) for the quiet-Sun coronal regions with temperature T _e > 5× 10^-5 K.     

On the figure of the planet Mercury

The figure of Mercury is estimated in terms of an isostatic form of equilibrium which tends to be controlled by the situation near perihelion passage at the 32 resonance spin rate. The ratios of the principal moments of inertia for Mercury are: (1)(C–A)/C7×10^–5; (2)(C–B)/C5×10^–5 and (3)(B–A)/C2×10^–5. The thermal effect on Mercury's figure during solidification forces Mercury's rotation to be trapped in the 32 resonance lock as its spin rate is being slowed by tidal effects. It is shown that the process of trapping of Mercury has been naturally affected by the instantaneous solidification of Mercury into a shape with two thermal bulges, and that the two permanent thermal bulges stabilize the planet's rotation.     

Mass transfer in TV Cassiopeiae

The period variations of TV Cassiopeiae between 1901 and 1977 are discussed in the light of the period change model proposed by Biermann and Hall. During each period decrease 4.0×10^–6 M of mass is transferred from the secondary star to the primary. The average observable mass transfer rate is found to be 4.3×10^–7 M yr^–1. This average rate corresponds to the thermal time-scale of the mass-losing star.