Latitude dependence of auroral frequency in relation to solar — Terrestrial and interplanetary parameters

The auroral frequency of occurrences (A) for the 20th solar cycle and for the geomagnetic latitudes 54–63 N has been investigated in relation to sunspot numbers (R _z), number of flares (F), the solar wind streams derived from the coronal holes (H) and the geomagnetic index (A _p). The relationship between A and the other indices were found to be strongly latitude dependent. At around 57–58 N, a drastic change in this relationship occurs, and an attempt is made qualitatively to evaluate this latitudinal variation.     

Estimates of the number of sunspot groups: Application to the activity cycle 1960–1970

It was verified that the total number of sunspot groups at certain region on the solar surface for a certain activity cycle can be estimated quite accurately by using the Markov chain approximation method on the total number of spot groups observed on the same region at an earlier activity cycle. Application has been carried out on the observed sunspots on three northern longitude intervals (40–50, 80–90, and 130–140) during the activity cycle 1950–1960 and 1960–1970. The total number of spot groups in these regions for the activity cycle 1960–1970 has been estimated from the observational data of the cycle 1950–1960. A good correlation between the observed and estimated number of spot groups for the activity cycle 1960–1970 has been noted.     

Mass and orbit estimation of Planet X via a family of comets

The crucial assumption of this paper is, that the observed clustering of aphelion distances of intermediate-period comets in the 70–90 AU range is due to the influence of a tenth planet, called Planet X. We contribute to the search for Planet X a new and extended evaluation of a family of comets assumed to be Planet X's family of comets.By averaging the aphelion distances of comets that belong to a transplutonic family of comets, we get Planet X's semi-major axis a _x = (83.0 ± 5.3) AU. The comets' orbits also yield the upper limit of the planet's orbital eccentricity e _x - 0.019. If this planet played an important part in sending quasi-periodic comet showers to the inner solar system, we can calculate its orbital inclination i _x = 46 .1 ± 3 .6. By distributing all planets' masses into the heliocentric, torus-like zones, in which they were formed, we get the density distribution of the primordial solar nebula. Extrapolating this distribution we find the mass of the planet M _x = (5.1_–2.4 ^+3.6 M _Earth. A few plausible assumptions (e.g. Uranus and Neptune perturbations being caused by Planet X) lead to Planet X's actual location with declination and eccliptic longitude being = 57 ± 17 and = 54 ± 34 , respectively (1989.5 position). In addition, we give Planet X's apparent brightness dependent on its unknown albedo. All those properties and predictions are more or less in agreement with earlier work on Planet X.     

A laboratory experiment with relevance to the survival of micro-organisms entering a planetary atmosphere

A culture of E.coli was initially subjected to brief exposures to heat for durations of 30–60 s, starting with a temperature of 270 C. A stepwise increase of this temperature from 270 C–750 C and a sequential culturing led to the emergence of a strain of this bacterium with a much higher resistance to flash heating than the original culture possessed. This behaviour would have an important relevance to the survival of micro-organisms upon entering a planetary atmosphere.     

The limits of possible values of inclination of Mercury's equator

The method of estimation of the limits, containing the equator inclination of a celestial body, had been developed. In this method it is necessary to know the orbital elements and the mass of a celestial body. Another condition is that the axial rotation of a body should be in the resonance with its orbital motion. It has been found that the equator inclinations should have the values between 1 .7 and 2 .6 for Mercury and between 1 .0 and 1 .8 for the Moon. It also has been found that largest harmonics in Mercury's physical libration are the harmonics sin( – 3g), cos( – 3g), sin g and sin 2.     

New results on the strato-mesospheric cooling of the Northern Hemisphere (1969–1978)

Rocketsonde — derived temperature trends within the Northern hemisphere are examined for the stratosphere and lower mesosphere for the period 1969–1978. The rocketsonde records presented here are homogeneous because of are mostly based on the Datasonde system. It appears that stratospheric and lower mesospheric temperature fluctuations in some cases, are about one order of magnitude larger than observed by previous workers. The main features for the temperature trends throughout the decade 1969–1978 are notably: (a) 15 C cooling at 60 km, (b) 5.5 C at 50 km, (c) 5 C at 40 km, (d) 4 C at 30 km, and (e) 3.5 C at 20 km.     

Insolation changes on pluto caused by orbital element variations

In this paper, we compare changes in the insolation at Pluto, corresponding to three epochs during the dynamical history of the planet: t = – 1, 0 and 0.5, where t is the time in millions of years A.D. The two extreme values of t coincide respectively with a maximum (126 ) and a minimum (102 ) value of the obliquity (). The other orbital elements i.e. the eccentricity (e) and the longitude of the perihelion ( _p ) which affect solar radiation and which are apt to significant periodic changes are also calculated for the times under consideration. In a series of figures, the combined influence of the evolving dynamic parameters on the daily insolation and on the mean (summer, winter, annual) daily insolation is illustrated.     

Structure of the martian north polar cap and vernal hood system at L s 61‡–66‡ of the 1995 apparition

The boundary and internal structure of the north polar deposits and polar hood vernal remnant on Mars have been mapped at L _s 61–66 on the hemisphere centered on longitude = 0, using images obtained in Feb–Mar 1995 with the Swedish Vacuum Solar Telescope on La Palma. On red light images, several internal rifts, including the historically well documented Rima Tenuis and Rima Hyperborea, as well as an internal, long absent, annular rift were mapped. The ground cap was asymmetric with a mean boundary at 72 N for = 270, increasing to 77 N at = 90. Images in green light showed the locations of high opacity hood clouds, including an extensive outflow to 67 N at 100. The state of the cap and hood is compared with the findings of previous studies and the historical significance of the annular rift structure is discussed. It is concluded, based on the structure of the deposited laminae, that the north polar climate was nearly, or possibly slightly milder than, normal at the northern hemisphere spring season studied.     

Effects of the Sector Structure of the Interplanetary Magnetic Field on Galactic Cosmic Ray Anisotropy

We study the effects of the sector structure of the interplanetary magnetic field (IMF) on the Galactic cosmic ray (GCR) anisotropy at solar minimum by using Global Network neutron monitor data. The hourly neutron monitor data for 1976 were averaged for the positive (+) and negative (–) IMF sectors (+ and – correspond to the antisolar and solar directions of magnetic field lines, respectively) and then processed by the global survey method. We found that the magnitude of the GCR anisotropy vector is larger in the positive IMF sector and that the phase shifts toward early hours. The derived GCR components A _r, A , and A for the different + and – sectors are then used to calculate the angle ( 46°) between the IMF lines and the Sun–Earth line, the solar wind velocity U ( 420 km/s), the ratio of the perpendicular (K ) and parallel (K _||) diffusion coefficients K /K _|| = ( 0.33), and other parameters that characterize the GCR modulation in interplanetary space.     

Cometary collisions and the dark material on Iapetus

Iapetus (S8) is unique in our solar system in that the albedo of its leading hemisphere is only 0.05 while that of the trailing side is 0.5. Several existing hypotheses are examined and found inadequate. Photometric studies of the dark side are compared to comet nuclei and class D asteroids. It is hypothesized that in the last 10⁶–10⁸ yrs the leading side suffered a high-velocity collision with a cometary body of mass 10¹³–10¹⁵ kg and traveling at a speed of 20 km s^–1. About 5–16% of the excavated material was ejected into space, where the vaporized ices dissipated while the dark carbonaceous/silicate material was reaccreted on the leading side. The collision, although not sufficient to break Iapetus' tidal lock, resulted in a period of oscillation of about 5 yr. Until tidal friction reasserted a lock, the oscillation gave rise to the longitude effect, viz., the observed fact that the dark material covers more than 220 of longitude but only 110 of latitude.     

Information limit optimisation techniques applied to recent photometry of Pluto

An algebraic approach originally intended for the heuristic modelling of the maculation effects of chromospherically active stars has been used to model the rotational modulation of Pluto's light. Two dark spots (30.0 ± 0.8 and 16.4 ± 1.4 in radius, at longitudes 3.4 ± 3.2 and 138.0 ± 5.2 degrees, and respective latitudes –35 and –16 ) were found to model the 1982.2 data of Binzel and Mulholland (1983) best. These parameters are in reasonable agreement with the other published models of Pluto's surface for the data, however this model can not be well reconciled with older data sets. A possible solution is dynamic behaviour of the dark features themselves, increasing in radius as perihelion is approached. We stress a minimum in the introduction of ad hoc surface feature hypothesis in this treatment.     

Possible contribution of a solar transient to enhanced scintillation of a quasar

Observations of the quasar 2314 + 038 were carried out during 16–21 December, 1985 at a solar elongation () around 85 , when the plasma tail of comet Halley swept in front of it. These observations have shown a two-fold increase in scintillation index (m) as compared to the expected levels of scintillation for the source, computed using the well-known RKH model. Spacecraft data and the geomagnetic indices available during the period show that a shock-front had reached the earth on the 18 December, the day when maximum increase in scintillation was recorded. The possible contribution of such a shock-front to the enhancement has been shown to be not greater than 15 percent. Hence, the major contribution to the enhancement came from the plasma tail of a comet.     

Imaging Fabry-Pérot observations of [OI] 6300 Å emission in the coma of Halley's comet 1982i

The observation of [OI] 6300 » emission in the coma of Halley's comet 1982i, using the imaging Fabry-Pérot spectrometer, was carried out from Gurushikhar (2439N, 7243E, 1700m altitude), Mt. Abu, India on March 15, 1986 (R = 0.90 AU, = 0.96 AU). The analysis of the interferogram show the absence of the differential velocity of neutral oxygen above 5 km s^–1.     

What we have learned about the Martian magnetic field

The evidence is presented for the existence of the magnetic field of the planet Mars and for the effectiveness of the dipolar part of the field as an obstacle to the solar wind at the most frequent parameters of the latter. The dipolar magnetic moment of Mars is (1.5–2.20 × 10²² G cm³. The dipole axis makes an angle i15 with the rotation axis of the panel. The magnetic north pole of Mars is located in its southern hemisphere.In terms of the precession dynamo model, the magnetic fields of the Earth and Mars are similar. This indicates that the Martian magnetic field is associated with the present-day dynamo-process in the Martian liquid core.     

The first Byurakan Spectral Sky Survey. Stars of later spectral classes. V. The zone +65°⩽δ⩽+69°

We give the fifth list of red stars of the First Byurakan Spectral Sky Survey. The objects are located in the zone 5^h 18^h 30^m and +65 +69. The list contains the data on 18 new objects, one of which is a star of class R. We also give the first determination of the spectral class of 11 variable objects, for four of which we give the spectrograms in the range of wavelengths 4700–6700å.Translated fromAstrofizika, Vol. 37, No. 4, 1994.     

Observations of energetic X-rays and solar cosmic rays associated with the 23 May 1967 solar flare event

On 23 May 1967 energetic (10–50 keV) solar flare X-rays were observed by the OGO-III ion chamber during the period 1808–2100 UT. The time-intensity profile for the X-ray event showed three distinct peaks at 1810, 1841 and 1942 UT. The second peak, which is equivalent to 2.9 × 10^–3 ergs cm^–2sec^–1 above 20 keV, is the largest X-ray burst observed so far by the OGO-I and OGO-III ion chambers. The soft (2–12 Å) X-ray observations reported by Van Allen (1968) also show similar peaks, roughly proportional in magnitude to the energetic X-ray peaks. However, the intensity of energetic X-rays peaked in each case 5–10 min earlier than the soft X-ray intensity indicating a relatively hard photon energy spectrum near the peak of the energetic X-ray emission. The corresponding time-intensity profile for the solar radio emission also showed three peaks in the microwave region nearly coincident with the energetic X-ray peaks. The third radio peak was relatively rich in the metric emission. Beyond this peak both the energetic X-rays and the microwave emission decayed with a time constant of 8 min while the corresponding time constant for the soft X-rays was 43 min. In view of the earlier findings about the energetic X-rays it is indicated that the 23 May solar X-ray event was similar to those observed earlier. During the 23 May event the integral energy flux spectrum at the time of peak intensity is found to be consistent with the form e ^–E/E ₀, E ₀ being about 3.4 and 3.7 keV for the peaks at 1841 and 1942 UT, respectively. Assumption of a similar spectrum during the decay phase indicates that the spectral index E ₀ decreased nearly exponentially with time.The OGO-III ion chamber, which is also sensitive to protons 12 MeV, observed a solar particle event starting at 2100 UT on 23 May. It could not be determined uniquely which of the two principal X-ray peaks was associated with the particle event, and in fact both may have contributed. The particle intensity reached its maximum value at 1003 UT on 25 May 1967. The equivalent peak radiation dosage was 24 R/hour behind the 0.22 g cm^–2 thick aluminum wall of the chamber. This peak radiation dosage was considerably smaller than the maximum dosage (60 R/hour) during the 2 September 1966 solar particle event, the largest event observed so far by the OGO-I and OGO-III satellites. The temporal relationship between the solar X-ray and particle events on 23 May 1967 was similar to that observed in the solar flare events on 7 July 1966, 28 August 1966 and 27 February 1967.     

Damping constant and turbulence in the solar atmosphere

In the region of the formation of weak and medium-strong lines, the microturbulence increases with height (V _ver=0.7–0.9 km s^-1, V _hor= 1.1–1.5 km s^-1), the macroturbulence decreases (V _ver=1.6–1.4 km s^-1, V _hor= 2.4–1.5 km s^-1), and the total velocity field (vertical component) is depth-independent (1.7 km s^-1). The empirical damping constants for Fe, Ti, Cr, Ni lines are equal 1.3₆, 1.7₆, 1.6₆, 1.6₆, respectively. The correlation length (the Kubo-Anderson process has been used) in the solar photosphere is 520–550 km.     

The thermal state of the Venusian mantle

Assuming that the surface topography of the Ovda and Thetis plateaus, and that of the saddle region between Thetis and Atla plateaus, is due to surface subsidence of oceanic-type thermal boundary layers, we calculated the temperature at 200 km beneath the plateaus to be about 1600 C, and that beneath the saddle region to be about 1400–1500 C. The total subsidence of Ovda plateau in the last 3/4 of its existence, i.e. between 200 km and 800 km off the postulated ridge axis, suggests that the plateau is probably a young feature, less than 40 m.y. old. The spreading plate models imply a half-spreading rate of 2.3–5.3 cm/yr for the plateaus and 2–2.8 cm/yr for the saddle region.     

YO molecule in the sun

Vibrational transition probabilities, namely Franck—Condon factors and -centroids have been evaluated by an approximate analytical method for the (A–X), (A–X), and (A–X) system of YO molecule. Morse potential energy curves forX ²⁺,A ²₂,A²₂, andA²₂, states of YO have been constructed using the latest spectroscopic data. The value of -centroids for the band have been found to decrease linearly with the corresponding wavelengths. We show results for two new transitions of (A–X) and (A–X) and five new bands of (A–X) of YO in the umbral spectrum of the Sun.     

CH3CN J = 8 − 7 and CS J = 3 − 2 emission in orion KL

The data of the line series CH₃CN 8(K) – 7(K) K = 0 – 7 and line CS J = 3 – 2 were taken simultaneously. At beam size of 16 the emissions of CH₃CN and CS have a common center position located near IRc2 with deviations -8 and 5. The observed data show that in Orion KL core the integrated intensities of the two species have double peaks separated by a space of 14. The 2-dimension Gaussian fitting plots (FWHM) are ellipses ofD _maj = 26 andD _min = 22 for CH₃CN 8(K) – 7(K) K = 3 – 6 andD_maj = 39 D_min = 31 for CS J = 3 – 2 at a distance about 450 pc. Towards the multiple line emission region of CH₃CN 8(K) – 7(K) K = 3 – 6, using a simplified very large velocity gradient model to solve the statistical equilibrium and radiative transfer equations, we find to fit the observed results, the optimum physical parameters and kinetic temperatureT _k 120 K, densityn(H _a) 1.2 × 10⁵ cm^–3, velocity gradientV _gr 92 km s^–1 pc^–1 and the local abundance of CH₃CNF _ab 3 × 10^–8. However towards the region of single line emission of CS J = 3 – 2 we have to use LTE and the optical thin approximation on the assumption ofT _k= 120 K to obtain the lower limits of column density and then, an averaged abundance of CS of 6 × 10^–8.