An optimal method for determining the time of the minimum of the 23rd solar cycle,July 2008

The time of the minimum of the solar cycle is usually determined by the minimum of the average monthly sunspot number smoothed over 13 months, i.e., with a large time delay, not earlier than eight months after the event. A new optimal method which allows one to establish the time of the minimum of the cycle as early as four months after the event is proposed. In the new method, the indicator of the time of a cycle minimum is the time of reaching the minimum level of average monthly values of the solar constant after which four succeeding values of this constant are larger than the pre-ceding minimum level. It is shown that the minimum of the past 23rd solar cycle took place in July, and the new 24th cycle started in August 2008.     

Ambartsumian’s paradigm for the activity of galactic nuclei and the evolution of galaxies

Ambartsumian’s paradigm for the creation of galaxies owing to the decay of denser matter is examined. The roots of this concept can be found in the very earliest papers of Ambartsumian on quantum fields and the structure of atomic nuclei. In the early 1930’s his papers contained new ideas regarding the ejection by one physical object of another which had not originally existed inside the first. The basic observational data which served as the basis for the final formulation of the new concept are described. Special attention is devoted to those objects and phenomena, which, upon further study, have confirmed the validity of Ambartsumian’s reasoning and arguments. It is noted that the discovery of Hubble expansion’s acceleration of the universe opened up new possibilities for the interpretation of activity phenomena in terms of Ambartsumian’s concept. The further extension of this concept is discussed and it is suggested that the major result of this approach should be the proof of the existence of galaxies of all ages within a finite volume of space.     

Unusual Solar Radio Burst Observed at Decameter Wavelengths

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s^?1) at frequencies higher than 22 MHz and negative (100 kHz?s^?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈10³ s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.     

Current-driven Alfvén waves in dusty magnetospheric plasmas

It is shown that the sheared flow of electrons and ions in the presence of heavy stationary dust gives rise to unstable Alfvén waves. The coupling of newly studied low frequency electrostatic current-driven mode with the electromagnetic Alfvén and drift waves is investigated. The instability conditions and the growth rates of both inertial and kinetic Alfvén waves are estimated. The theoretical model is applied to the night side boundary regions of Jupiter’s magnetosphere which contain positive dust. The growth rates increase with increase in sheared flow speed. In the nonlinear regime, both inertial and kinetic Alfvén waves form dipolar vortices whose speed and amplitude depend upon the magnitude of the zero-order current.     

Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events

During the rising phase of Solar Cycle 24 tremendous activity occurred on the Sun with rapid and compact emergence of magnetic flux leading to bursts of flares (C to M and even X-class). We investigate the violent events occurring in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed in November 2010 with instruments onboard the Solar Dynamics Observatory and from Earth. Within one day the total magnetic flux increased by 70 % with the emergence of new groups of bipoles in AR 11123. From all the events on 11 November, we study, in particular, the ones starting at around 07:16 UT in GOES soft X-ray data and the brightenings preceding them. A magnetic-field topological analysis indicates the presence of null points, associated separatrices, and quasi-separatrix layers (QSLs) where magnetic reconnection is prone to occur. The presence of null points is confirmed by a linear and a non-linear force-free magnetic-field model. Their locations and general characteristics are similar in both modelling approaches, which supports their robustness. However, in order to explain the full extension of the analysed event brightenings, which are not restricted to the photospheric traces of the null separatrices, we compute the locations of QSLs. Based on this more complete topological analysis, we propose a scenario to explain the origin of a low-energy event preceding a filament eruption, which is accompanied by a two-ribbon flare, and a consecutive confined flare in AR 11123. The results of our topology computation can also explain the locations of flare ribbons in two other events, one preceding and one following the ones at 07:16 UT. Finally, this study provides further examples where flare-ribbon locations can be explained when compared to QSLs and only, partially, when using separatrices.     

Generalized second law of thermodynamics with corrected entropy in tachyon cosmology

This work is to study the generalized second law (GSL) of thermodynamics in tachyon cosmology where the tachyon field is coupled to the matter Lagrangian while the boundary of universe is assumed to be a dynamical apparent horizon. The two logarithmic and power law corrected entropy on the apparent horizon is also discussed and the conditions for validity of GSL in both scenarios are investigated by using observational data of Sne Ia. In comparison to other research works, since the model is constrained by observational data, the conditions obtained for the dimensionless constant parameter, α in both logarithmic and power law entropy correction of GSL are (physically) meaningful and realistic. The model also predicts an accelerating universe with no phantom crossing in the past or future.     

Modulational instability of dust ion acoustic waves in dusty plasmas with superthermal electrons

The propagation of dust ion acoustic waves is studied in plasmas composed of superthermal distributed electrons and stationary dust particles. The nonlinear Schrödinger equation is derived using the reductive perturbation technique and the modulational instability of dust ion acoustic waves is analyzed. Parametric investigations indicate that the presence of superthermal distributed electrons significantly modify the modulational instability and its growth rate. The effect of particle relative density on the wave characters is also investigated.     

First observation of CO at 345 GHz in the atmosphere of Saturn with the JCMT: New constraints on its origin

We have performed the first observation of the CO(3-2) spectral line in the atmosphere of Saturn with the James Clerk Maxwell Telescope. We have used a transport model of the atmosphere of Saturn to constrain the origin of the observed CO. The CO line is best-fit when the CO is located at pressures less than (15±2) mbar with a mixing ratio of (2.5±0.6)×10^-8 implying an external origin. By modeling the transport in Saturn’s atmosphere, we find that a cometary impact origin with an impact 200-350 years ago is more likely than continuous deposition by interplanetary dust particles (IDP) or local sources (rings/satellites). This result would confirm that comet impacts are relatively frequent and efficient providers of CO to the atmospheres of the outer planets. However, a diffuse and/or local source cannot be rejected, because we did not account for photochemistry of oxygen compounds. Finally, we have derived an upper limit of ∼1×10^-9 on the tropospheric CO mixing ratio.     

Temperature-dependent photoabsorption cross-sections of cyanoacetylene and diacetylene in the mid- and vacuum-UV: Application to Titan's atmosphere

Cyanoacetylene (HC₃N) and diacetylene (C₄H₂) play an important role in the photochemistry of Titan's atmosphere, in part because of their strong absorption between 110 and 180 nm. Accurate photoabsorption cross-sections at temperatures representative of Titan's atmosphere are required to interprete Cassini observations and to calculate photolysis rates used in photochemical models. Using synchrotron radiation as a tunable vacuum ultraviolet (VUV) light source, we have measured absolute photoabsorption cross-sections of C₄H₂ and HC₃N with a spectral resolution of 0.05 nm in the region between 80 and 225 nm and at different temperatures between 173 and 295 K. The measured cross-sections are used to model transmission spectra of Titan atmosphere in the VUV.