On the nature of the apparent response of the vorticity area index to the solar magnetic field

The apparent response of the vorticity area index to the solar magnetic field is confined to tropospheric regions of intense circulation. Discussions and calculations that include larger volumes of the troposphere would not be expected to show a significant Sun-weather effect. Analysis of the effect in time intervals outside the original 1963–73 is also discussed. An assessment of this Sun-weather effect at the present time is given.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

The spectrum of diffuse cosmic X-rays in the 20–125 keV range

Diffuse cosmic X-rays in the energy range 20–125 keV were measured in four balloon flights from Hyderabad, India during 1968–70 using almost identical X-ray telescopes mounted on oriented platforms. The results from these flights show that the spectrum of the diffuse cosmic X-rays can be represented by the form dN/dE=29E ^–2.1±0.3 photons/(cm² sr s keV) in 20–125 keV interval after corrections for photoelectric absorption and Compton scattering effects in the atmosphere. The best fit spectrum of all published results in the energy interval 20–200 keV can be represented by the form dN/dE=36E ^–2.1±0.1 photons/(cm² sr s keV) after similar corrections are effected, and there is no need for a change of spectral index in this energy interval. The intensity at 20 keV obtained from the above spectrum agrees well with that given by the spectral form dN/dE=10E ^–1.7±0.1 photons/(cm² sr s keV) in the energy interval 1–20 keV in several rocket experiments. Therefore it is concluded that if there is a break in the spectrum, it occurs between 10 and 20 keV with a change of spectral index by about 0.5, or the index is continuously changing from 1.7±0.1 to 2.1±0.1 in 10–20 keV interval. The implications of the results are briefly discussed.     

The effect of gradient and curvature drifts on Forbush decreases

The average profile of Forbush decreases, produced by eastern-, central- and western-region solar flares is obtained separately by superposed epoch analysis for the periods 1966–1969 (qA < 0) and 1971–1979 (qA > 0). It is observed that the recovery of an average Forbush decrease from the maximum depression level is faster for the situation qA > 0 than for the situation qA < 0. This is in accordance with expectations from the drift theory. It is also observed that the drift effect is more pronounced for western-flare Forbush decreases which, of course, have a smaller magnitude compared to eastern- and central-flare Forbush decreases.The average profiles of simple and complex type Forbush decreases are also obtained separately for three periods 1965–1979, 1971–1979, and 1981–1987. It is found that the average profiles of simple and complex type Forbush decreases observed during the period 1965–1969 and 1971– 1979 are quite in agreement with drift theory. The anomalous behavior of average Forbush-decrease profiles during the period 1981–1987, especially in simple type Forbush decreases, is also explained by a drift current sheet tilt model.     

Turbulence in the troposphere of Venus: Refined characteristics and new estimates

Based on spaceborne experimental data, characteristics of turbulence are calculated for the Venusian troposphere under conditions corresponding to the planet-averaged flux of solar radiation, which is equal to its value at a solar zenith angle of 66°. Additionally, given experimental data on radiation fluxes and their numerical calculations, turbulence characteristics were calculated for a solar zenith angle of 45°. The turbulence pattern is significantly different for small and large solar zenith angles. At large solar zenith angles, there exist an anomalous downward turbulent heat flux above 7–10 km and a normal upward flux at lower heights. At small zenith angles, the turbulent flux is normal throughout the entire troposphere. The dissipation of turbulent energy contributes significantly to the atmospheric heating in a wide range of altitudes. The spectrum of the time and space scales of dissipative processes in the troposphere is very wide and changes with height.Translated from Astronomicheskii Vestnik, Vol. 39, No. 1, 2005, pp. 38–50.Original Russian Text Copyright © 2005 by Izakov.     

Climate changes and recent glacier behaviour in the Chilean Lake District

Atmospheric temperatures measured at the Chilean Lake District (38°–42°S) showed contrasting trends during the second half of the 20th century. The surface cooling detected at several meteorological stations ranged from − 0.014 to − 0.021 °C a^− 1, whilst upper troposphere (850–300 gpm) records at radiosonde of Puerto Montt (41°26′S/73°07′W) revealed warming between 0.019 and 0.031 °C a^− 1. Regional rainfall data collected from 1961 to 2000 showed the overall decrease with a maximum rate of − 15 mm a^− 2 at Valdivia st. (39°38′S/73°05′W). These ongoing climatic changes, especially the precipitation reduction, seem to be related to El Niño–Southern Oscillation (ENSO) phenomena which has been more frequent after 1976. Glaciers within the Chilean Lake District have significantly retreated during recent decades, in an apparent out-of-phase response to the regional surface cooling. Moreover, very little is known about upper troposphere changes and how they can enhance the glacier responses. In order to analyse their behaviour in the context of the observed climate changes, Casa Pangue glacier (41°08′S/71°52′W) has been selected and studied by comparing Digital Elevation Models (DEMs) computed at three different dates throughout the last four decades. This approach allowed the determination of ice elevation changes between 1961 and 1998, yielding a mean thinning rate of − 2.3 ± 0.6 m a^− 1. Strikingly, when ice thinning is computed for the period between 1981 and 1998, the resulting rate is 50% higher (− 3.6 ± 0.6 m a^− 1). This enhanced trend and the related area loss and frontal retreat suggests that Casa Pangue might currently be suffering negative mass balances in response to the upper troposphere warming and decreased precipitation of the last 25–30 yr, as well as debris cover would not prevent the glacier from a fast reaction to climate forcing. Most of recent glaciological studies regarding Andean glaciers have concentrated on low altitude changes, namely frontal variations, however, in order to better understand the regional glacier changes, new data are necessary, especially from the accumulation areas.     

A dynamical mechanism through which variations in solar ultraviolet radiation can influence tropospheric climate

Variations in solar UV radiation can lead to changes in the mean temperature and wind distributions in the stratosphere and, through modification of the ozone photochemistry, to changes in the damping rate of temperature perturbations about the mean. Such changes can influence the stratospheric propagation characteristics of planetary waves generated in the troposphere, leading to changes in the steady state interference pattern of these waves at all levels. In particular, the poleward heat transfer by the planetary waves in the troposphere can be strongly modified, thus providing a mechanism whereby solar cycle variations in ultraviolet radiation can influence climate.The dynamics of the mechanism are presented in a simple form and the literature on the subject is reviewed.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

Evolution of an active region and associated Hα arch structures

We have studied the early stages of development of two adjacent active regions observed at the center and the wings of H for six days. From the growth of spots and arch structures we found that periods of slow flux emergence were followed by periods of vigorous flux emergence. We observed arch filaments covering an appreciable range of sizes (from a length of about 27 000 km and a height of 2000–3000 km to a length of 45 000 km and a height of about 15 000 km). Individual arch filaments within the same arcade sometimes have different inclinations of their planes with respect to the vertical. We observed isolated cases of arches crossing each other at an angle of 45°. During their early stages arch filament systems are short and they expand at a rate of about 0.8 km s^–1. The rate of growth of arch filament systems is faster when the orientation of the flux tubes is nearly parallel to the equator. Our observations suggest that the early part of the evolution of individual arch filaments in a grown system is not visible; however, in a few cases we observed arch filaments appearing as dark features near one footpoint and expanding towards the other, with a mean velocity of about 30 km s^–1.     

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.     

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.     

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.     

The properties of molecular clouds with high redshifts (z=2–3)

This paper deals with molecular clouds discovered in the absorption spectra (z=2–3) of distant quasars. It is argued that these clouds belong to the gaseous subsystems of young galaxies. We estimate the gas concentration to ben<10⁴ cm^–3 in the cloud observed in the direction of the quasar PHL957. It is shown that this cloud is exposed to ultraviolet radiation. The UV-energy flux does not exceed the value typical for our Galaxy by an order of magnitude (F2×10^–6 ergs cm^–2 s^–1 Å^–1 at =2000 Å). The mechanisms maintaining the thermal balance in this cloud are discussed.     

Cs studies of dense cores in regions of high mass star formation: a survey of southern molecular masers

We searched for the CSJ = 2 – 1 emission towards 29 southern H₂O and H₂O/OH masers and 1 OH maser with the SEST radio telescope. We detected and mapped 24 CS emitting regions probably associated with 27 H₂O masers. The C³⁴SJ = 2 – 1 and COJ = 1 – 0 lines were also observed at the grid positions closest to the CS peaks. Four cores were mapped in the CSJ = 5 – 4 and C³⁴SJ = 2 – 1 lines.     

A search for solar neutrons during solar flares

The upper limit on the solar neutron flux from 1–20 MeV has been measured, by a neutron detector on the OGO-6 satellite, to be less than 5 × 10^–2 n cm^–2 s^–1 at the 95% confidence level for several flares including two flares of importance 3B and a solar proton event of importance 3B. The measurements are consistent with the models proposed by Lingenfelter (1969) and by Lingenfelter and Ramaty (1967) for solar neutron production during solar flares. The implied upper limit on the flux of 2.2 MeV solar gamma rays is about the same as the 2.2 MeV flux observed by Chupp et al. (1973).     

Energy spectrum and time variations of hard X-rays from Cyg X-1

Experimental results on the intensity, energy spectrum and time variations in hard X-ray emission from Cyg X-1 based on a balloon observation made on 1971, April 6 from Hyderabad (India) are described. The average energy spectrum of Cyg X-1 in the 22–154 keV interval on 1971 April 6 is best represented by a power law dN/dE=(5.41±1.53)E ^{–(1.92±0.10)} photons cm^–2s^–1 keV^–1 which is in very good agreement with the spectrum of Cyg X-1 derived from an earlier observation made by us on 1969 April 16 in the 25–151 keV band and given by dN/dE=(3.54±2.44)E ^{–(1.89±0.22)} photons cm^–2s^–1 keV^–1. A thermal bremsstrahlung spectrum fails to give a good fit over the entire energy range for both the observations. Comparison with the observations of other investigators shows that almost all balloon experiments consistently give a spectrum of E ^–2, while below 20 keV the spectrum varies fromE ^–1.7 toE ^–5. There is some indication of a break in the Cyg X-1 spectrum around 20 keV. Spectral analysis of data in different time intervals for the 1971 April 6 flight demonstrates that while the source intensity varies over time scales of a few minutes, there is no appreciable variation in the spectral slope. Analysis of various hard X-ray observations for long term variations shows that over a period of about a week the intensity of Cyg X-1 varies upto a factor of four. The binary model proposed by Dolan is examined and the difficulties in explaining the observed features of Cyg X-1 by this model are pointed out.     

The Hypothesis of Additional Acceleration in the Motion of Comet Harrington–Abell from Jupiter

By processing 494 observations of Comet Harrington–Abell, we obtained a unified system of elements that includes its turn around the Sun during which it closely approached Jupiter to a minimum distance of 0.037 AU in 1974. A study of the cometary orbit before and after the approach showed that, probably, at the approach of the comet to Jupiter, apart from the well-known gravitational perturbations, its motion was affected by an additional force. An improvement of the cometary orbit by assuming that an additional acceleration inversely proportional to the square of the distance to Jupiter exists in its motion yielded the following values: (4.57 ± 0.42) × 10^–10 and (–7.20 ± 0.42) × 10^–10 AU day^–2 for the radial and transversal acceleration components, respectively. As a plausible explanation of the changes in the cometary orbit, we additionally considered a model based on the hypothesis of partial disintegration of the cometary nucleus. The parameter that characterizes the instant displacement of the center of inertia along the jovicentric radius vector was estimated to be –1.83 ± 0.75 km. Based on a unified numerical theory of cometary motion, we determined the nongravitational parameters using Marsden's model for two periods: A ₁ = (11.68 ± 1.74) × 10^–10 AU day^–2, A ₂ = (0.53 ± 0.0357) × 10^–10 AU day^–2 for 1975–1999 and A ₁ = (5.92 ± 5.86) × 10^–10 AU day^–2, A ₂ = (0.08 ± 0.028) × 10^–10 AU day^–2 for 1955–1969, under the assumption that the nongravitational acceleration changed at the approach of the comet to Jupiter.     

Large-scale active coronal phenomena in Yohkoh SXT images

We have found several occurrences of slowly rising giant arches inYohkoh images. These are similar to the giant post-flare arches previously discovered by SMM instruments in the 80s. However, we see them now with 3–5 times better spatial resolution and can recognize well their loop-like structure. As a rule, these arches followeruptive flares with gradual soft X-ray bursts, and rise with speeds of 1.1–2.4 km s^–1 which keep constant for >5 to 24 hours, reaching altitudes up to 250 000 km above the solar limb. These arches differ from post-flare loop systems by their (much higher) altitudes, (much longer) lifetimes, and (constant) speed of growth. One event appears to be a rise of a transequatorial interconnecting loop.In the event of 21–22 February 1992 one can see both the loop system, rising with a gradually decreasing speed to an altitude of 120 000 km, and the arch, emerging from behind the loops and continuing to rise with a constant speed for many more hours up to 240 000 km above the solar limb. In the event of 2–3 November 1991 three subsequent rising large-scale coronal systems can be recognized: first a fast one with speed increasing with altitude and ceasing to be visible at about 300 000 km. This most probably shows the X-ray signature of a coronal mass ejection (CME). A second one, with gradually decreasing speed, might represent very high rising flare loops. A third one continues to rise slowly with a constant speed up to 230 000 km (and up to 285 000 km after the speed begins to decay), and this is the giant arch. This event, including an arch revival on November 4–5, is very similar to rising giant arches observed by the SMM on 6–7 November 1980. Other events of this kind were observed on 27–28 April 1992, 15 March 1993, and 4–6 November 1993, all seen above the solar limb, where it is much easier to identify them.The temperature in the brightest part of the arch of 2–3 November 1991 was increasing with its altitude, from 2 to 4 × 10⁶ K, which seems to be an effect of slower cooling at lower densities. Under an assumption of line-of-sight thickness of 50 000 km, the emission measure indicates densities from 1.1 × 10¹⁰ cm^–3 at an altitude of 150 000 km to 1.0 × 10⁹ cm^–3 at 245 000 km 11.5 hours later. It appears that the arch is composed of plasma of widely different temperatures, and that hot plasma rises faster than the cool component. Thus the whole arch expands upward, and its density gradient increases with time, which explains whyYohkoh images show only the lowest and coolest parts of the expanding structure. The whole arch may represent an energy in excess of 10³¹ erg, and more if conduction contributes to the arch cooling.We suggest that the rise of the arch is initiated by a CME which removes the magnetic field and plasma in the upper corona, and the coronal structures remaining below this cavity begin to expand into the vacuum left behind the CME. However, we are unable to explain why the speed of rise stays constant for so many hours.     

A comparison study between the newly-born ion effect and the thermal effect on the whistlers in the ionosphere

We have considered an ionospheric plasma model that includes the thermal effect along with the newly born ionic effect and derived a group travel time for the low-frequency whistlers with a view to employing it as a diagnostic tool in the ionosphere. The mathematical development shows that the thermal effect contribution varies with ( _i – )_–7/2 whereas that of the newly born ionic effect varies with _i – )_–5/2. Both the effects are discussed separately. It is concluded that the effects are reasonably countable in the ionosphere. The investigations finally conclude that both the effects should be taken into the whistler waves, otherwise the method might cause a discrepancy in the results, which could affect their accuracy.     

A study of non-thermal radio emission features using fine spectral BAO and high-sensitivity RATAN observations of a solar active region

Based on spectral observations of active region NOAA 8545 on 19 May 1999, we describe the processes responsible for non-thermal long-lasting radio emission and for narrow-band non-drifting bursts observed at the same time. Non-thermal long-lasting radio emission consisted of two components: short-duration (1–2 s) microbursts with fluxes about 0.001 s.f.u. and continuum emission with growing spectrum in the range of 1000–2000 MHz. Energetic electrons continuously existed in the active region for more than 2.2 hours. The nature and parameters of microbursts were discussed by Bogod, Mercier, and Yasnov (2001). Here we consider the continuum source nature. It is shown that the model, taking into account the cyclotron loss-cone instability of hot electrons and the generation of plasma waves at the upper hybrid frequency, may explain the observed continuum source parameters. For the narrow-band non-drifting bursts we consider two models: the first taking into account an excitation of weak shock waves across the magnetic field and the second with an excitation of the upper hybrid waves under the double plasma resonance. Continuum source parameters are close to the last model. Our estimations for the magnetic field strength are as follows: H=120–126 G, which is valid for the region where the electron density of background plasmas n=(1.4–1.9) ×10⁹ cm^–3; H=180–190 G for the region where n=(3.0–4.3) ×10⁹ cm^–3; H=290 G for the region where n _e=2.5×10¹⁰ cm^–3; and H=350 G for the region where n _e=3.5×10¹⁰ cm^–3. The speed of the fast electrons is about 0.10–0.14 c.     

Some requirements of a colliding comet source of gamma ray bursts

Colliding comets in the Solar System may be an important source of gamma ray bursts. The spherical gamma ray comet cloud required by the results of the Venera Satellites (Mazets and Golenetskii, 1987) and the BATSE detector on the Compton Satellite (Meeganet al., 1992a, b) is neither the Oort Cloud nor the Kuiper Belt. To satisfy observations ofN(>P _max) vsP _max for the maximum gamma ray fluxes,P _max > 10^–5 erg cm^–2 s^–1 (about 30 bursts yr^–1), the comet density,n, should increase asn a ¹ from about 40 to 100 AU wherea is the comet heliocentric distance. The turnover above 100 AU requiresn a ^–1/2 to 200 AU to fit the Venera results andn a ^1/4 to 400 AU to fit the BATSE data. Then the masses of comets in the 3 regions are from: 40–100 AU, about 9 earth masses,m _E; 100–200 AU about 25m _E; and 100–400 AU, about 900m _E. The flux of 10^–5 erg cm^–2 s^–1 corresponds to a luminosity at 100 AU of 3 × 10²⁶ erg s^–1. Two colliding spherical comets at a distance of 100 AU, each with nucleus of radiusR of 5 km, density of 0.5 g cm^–3 and Keplerian velocity 3 km s^–1 have a combined kinetic energy of 3 × 10²⁸ erg, a factor of about 100 greater than required by the burst maximum fluxes that last for one second. Betatron acceleration in the compressed magnetic fields between the colliding comets could accelerate electrons to energies sufficient to produce the observed high energy gamma rays. Many of the additional observed features of gamma ray bursts can be explained by the solar comet collision source.     

Identification of some diffuse interstellar features

Twenty-eight of the thirty-nine diffuse interstellar bands identified by Herbig (1975) are shown to constitute three vibronic systems with origins at 14 321, 15 153, and 15 343 cm^–1 (vac). Structure within these three systems arises from the excitation of vibrational modes withv ₁=275 cm^–1,v ₂=445.5 cm^–1, andv ₃=793 cm^–1. The electronic origins at 14 321 and 15 343 cm^–1 correspond to narrow lines observed in the spectrum of Cr³⁺ ions at cubic sites in MgO solids while the 15 153 cm^–1 origin arises in Mn⁴⁺ : MgO. Hence, many of the diffuse bands in the visible likely are due to small MgO particles containing these ions. This observation is compatible with recent experimental data showing broad bands at 160 nm and 220 nm from finely divided MgO solids that match features in the interstellar extinction curve.