Magnetic instability of coronal arcades as the origin of two-ribbon flares

The generally accepted scenario for the events leading up to a two-ribbon flare is that a magnetic arcade (supporting a plage filament) responds to the slow photospheric motions of its footpoints by evolving passively through a series of (largely) force-free equilibria. At some critical amount of shear the configuration becomes unstable and erupts outwards. Subsequently, the field closes back down in the manner modelled by Kopp and Pneuman (1976); but the main problem has been to explain the eruptive instability.The present paper analyses the magnetohydrodynamic stability of several possible arcade configurations, including the dominant stabilizing effect of line-tying at the photospheric footpoints. One low-lying force-free structure is found to be stable regardless of the shear; also some of the arcades that lie on the upper branch of the equilibrium curves are shown to be stable. However, another force-free configuration appears more likely to represent the preflare structure. It consists of a large flux tube, anchored at its ends and surrounded by an arcade, so that the field transverse to the arcade axis contains a magnetic island. Such a configuration is found to become unstable when either the length of the structure, the twist of the flux tube, or the height of the island becomes too great; the higher the tube is situated, the smaller is the twist required for instability.     

Non-topological solitons as the possible origin of intrinsic extragalactic redshifts

The eleven-year sunspot cycles are considered to represent one of the solar activities. The daily observations of the sunspots in the KAAU Solar Observatory (KAAUSO) have been utilised to reduce a period of the present solar cycle, using Fourier technique. The highest peak in the amplitude spectrum was for a frequency of 0.00029 day^–1, for which the maximum occurred mid 1990.     

On possible cosmic origin of the 11-year solar cycle

In order to test Dicke??s idea of a clock hidden inside the Sun and determine the initial phase of the solar cycle, the epochs of the extrema of the Wolf numbers observed over the past 400 years are examined. It is shown that extrema that obey the period P _W equaled 11.07(4) years retain the initial phase, which cannot be explained in terms of local physics and concepts of the past century regarding the mechanism of the solar cycle based on the theory of a magnetic dynamo and the phenomenological model of the Babcock-Leighton cycle. It is suggested that the cycle has a cosmic (cosmological) origin. This is clearly indicated by the correlation of the cycle period with a holographic time-scale of the Universe, (a ₀ R ³)^1/4/c ?? 11.0(4) years, where a ₀ and R are the radii of the first Bohr orbit of a hydrogen atom and the observable Universe, respectively, and c is the speed of light. It is noted that there are other strict holographic relations that include a ₀, R, P _W , the wavelength of the microwave background radiation (with a temperature of 2.7 K), and a period of the global solar pulsations equal to 9600.6 s. The true physical nature of the governing mechanism for the 11-year cycle can perhaps only be understood based on modern concepts about the nonlocality of our world, which follows from Bell??s theorem, which is grounded on the achievements of quantum mechanics at the turn of the 20th and 21st centuries, as well as using a model of a holographic Universe free of c.     

The nature and possible origin of lava-like material within cheniér crater

This paper considers the origin of certain tongues of lava-like material in Cheniér Crater, a meteorite crater located about 63 km northeast of the major crater, Tsiolkovsky, on the lunar far side. The author contends that the tongues originated from subsurface movement of magma generated as a result of the meteorite impact which created Tsiolkovsky Crater. The impact produced lines of weakness which were further enhanced by the impact forming Cheniér. Magma then moved from Tsiolkovsky through the zones of weakness to Cheniér Crater, extruding on the surface to form the first stringer. Following the extrusion, magnetic movement stopped and a cap formed over the vent. Enough heat was left in place under Cheniér, however, to cause crustal melting and consequently the extrusion of a second and possible third lava-like stringer before the magma chamber under Cheniér cooled and a cap over the vents permanently formed. Confirmation of the theory depends upon whether magma can move through weak zones in the lunar subsurface. Indications of this possibility have been suggested in findings dealing with the floors of Tycho and Aristarchus craters and in a study of the effects of artificial cratering.     

Oscillation structure of gamma-ray bursts and their possible origin

It is hypothesized that thermonuclear burning of the matter from the envelope of a massive compact star accreting onto a hot neutron star produced by spherically symmetric collapse of a stellar iron core can proceed in oscillation mode (much as is the case during thermal explosions of carbon-oxygen cores in lower mass stars). Local density oscillations near the neutron-star surface can generate shock waves; in these shocks, the electron-positron plasma is stratified from the remaining matter, and shells of an expanding relativistic fireball with an oscillation time scale in cosmological gamma-ray bursts (GRBs) of ～10^?2 s are formed. It is pointed out that the GRB progenitors can be nonrotating massive Wolf-Rayet (WR) stars whose collapse, according to observational data, can proceed without any substantial envelope ejection.     

Comparison of the structures of meteor streams of cometary and possible asteroidal origin

The structures of the meteor streams of cometary origin—Draconids, Ursids, Perseids, and Lyrids—and the streams presumably connected with asteroids—Taurids and α-Capricornids—are compared. The comparative analysis was performed by the mass distribution of meteoroids in the stream and the activity profile for the meteors with the maximum recorded stellar magnitude +3 ^m and brighter. Visual observations of 1987–2008 from the database of the International Meteor Organization (IMO) and earlier sources were considered. It has been shown that the structures of the meteor streams of cometary and, presumably, asteroidal origin differ somewhat by the activity profile and the mass distribution of meteoroids in the cross-section of a stream along the Earth’s orbit.     

Cyclotron wave instability in the corona and origin of solar radio emission with fine structure

The longitudinal waves (Bernstein modes and plasma waves near the hybrid frequency) in a mixture of equilibrium coronal plasma and a small group of energetic electrons are investigated. The energetic electrons have a nonequilibrium momentum distribution inherent in trapped particles. The frequency dependence of the cyclotron instability increments is studied. Attention is paid to a significant role of the relativistic effects for the cyclotron instability of longitudinal waves. For sufficiently large velocity of nonequilibrium electrons the increments are shown to increase when the hybrid frequency coincides with one of the gyrofrequency harmonics (double plasma resonance). The results obtained are used in Parts II and III to explain tadpoles and zebra-pattern in solar radio bursts.     

Angular momentum of binary asteroids: Implications for their possible origin

We describe in this work a thorough study of the physical and orbital characteristics of extensively observed main-belt and trojan binaries, mainly taken from the LAOSA (Large Adaptive Optics Survey of Asteroids [Marchis, F., Baek, M., Berthier, J., Descamps, P., Hestroffer, D., Kaasalainen, M., Vachier, F., 2006c. In: Workshop on Spacecraft Reconnaissance of Asteroid and Comet Interiors. Abstract #3042]) database, along with a selection of bifurcated objects. Dimensionless quantities, such as the specific angular momentum and the scaled primary spin rate, are computed and discussed for each system. They suggest that these asteroidal systems might be the outcome of rotational fission or mass shedding of a parent body presumably subjected to an external torque. One of the most striking features of separated binaries composed of a large primary (Rp>100 km) with a much smaller secondary (Rs<20 km) is that they all have total angular momentum of ∼0.27. This value is quite close to the Maclaurin-Jacobi bifurcation (0.308) of a spinning fluid body. Alternatively, contact binaries and tidally locked double asteroids, made of components of similar size, have an angular momentum larger than 0.48. They compare successfully with the fission equilibrium sequence of a rotating fluid mass. In conclusion, we find that total angular momentum is a useful proxy to assess the internal structure of such systems.     

A pulsating regime of stream instability and the origin of ‘rain’ type radio bursts

An interpretation is suggested for the rain type radio bursts on the basis of a pulsating regime of the stream instability. This regime may occur in ejected stabilized ion streams trapped in the region in which the magnetic field of the corona has a typical bipolar structure.     

Numerical simulation of a possible origin of the positive radial metallicity gradient of the thick disk

We analyze the radial and vertical metallicity and [α/Fe] gradients of the disk stars of a disk galaxy simulated in a fully cosmological setting with the chemodynamical galaxy evolution code GCD+. We study how the radial abundance gradients vary as a function of height above the plane and find that the metallicity([α/Fe]) gradient becomes more positive(negative) with increasing height, changing sign around1.5 kpc above the plane. At the largest vertical height(2 |z| 3 kpc), our simulated galaxy shows a positive radial metallicity gradient. We find that the positive metallicity gradient is caused by the age-metallicity and age-velocity dispersion relation, where younger stars have higher metallicity and lower velocity dispersion. Due to the agevelocity dispersion relation, a greater fraction of younger stars reaches |z| 2 kpc at the outer region, because of the lower gravitational restoring force of the disk, i.e.flaring. As a result, the fraction of younger stars with higher metallicity due to the age-metallicity relation becomes higher at the outer radii, which makes the median metallicity higher at the outer radii. Combining this result with the recently observed age-metallicity and age-velocity dispersion relation for the Milky Way thick disk stars suggested by Haywood et al., we argue that the observed(small) positive radial metallicity gradient at large heights of the Milky Way disk stars can be explained by flaring of the younger thick and/or thin disk stars.     

The origin of the Big-Bang

Within the framework of FLRW cosmology withk=+1 a singularity free model of the Universe is proposed which readily accounts for the origin of the Big-Bang and for the preponderance of matter over anti-matter. It is also free from the problems of accounting for the observed large-scale homogeneity and isotropy of the Universe as well as from the problems of horizon and flatness. It is pointed out that the collapsing universe might have acted as an ultra-high energy particle accelerator. In the collapsing phase of the Universe, when the interparticle distances10^–16 cm, the electromagnetic and weak interactions might have unified into electroweak interaction and as the collapse proceeded further the entire matter in the Universe might have been converted into quark-gluon plasma permeated by leptons. The gravitational energy released during the collapse might have been locked in this plasma. Ass approached 10^–28 cm, grand unification of electroweak and strong interactions might have occurred. It is also suggested that, with further collapse, whens<10^–33 cm super-symmetry (SUSY)—i.e., the unification of all the four interactions (viz., electromagnetic, weak, strong, and gravitational) might have occurred. During this process gravitinos, the supersymmetric partners of graviton might have been produced. As a result of the exchange of a pair of virtual gravitinos between two particles an ultra-strong repulsive force between them might have been generated. Due to this ultra-strong repulsive interaction between particles the motion of the Universe might have been reversed, i.e., the Universe might have started expanding. During expansion, whens10^–28 cm, SUSY might have broken down spontaneously toSU ₅ and gravity. Ass increased from 10^–28 to 10^–16 cm, the gravitational energy locked in the quark-gluon plasma might have been released with a gigantic explosion, the so-called Big-Bang. It is estimated here that during this Big-Bang more than 10⁸² GeV of energy might have been released. Whens10^–16 cm,SU ₅ might have broken down spontaneously toSU ₃ andU ₁. Expansion beyond this stage might have occurred in the manner described by the standard cosmology. It is further suggested that in due course of time expansion will be followed by contraction and the cycle of contraction-expansion-contraction will be repeated ad infinitum.     

The Kelvin-Helmholtz instability on the magnetopause

Conditions for the development of Kelvin-Helmholtz (K-H) waves on the magnetopause have been known for more than 15 years; more recently, spacecraft observations have stimulated further examination of the properties of K-H waves. For amagnetopause with no boundary layer, two different modes of surface waves have been identified and their properties have been investigated for various assumed orientations of magnetic field and flow velocity vectors. The power radiated into the magnetosphere from the velocity shear at the boundary has been estimated. Other calculations have focused on the consequences of finite thickness boundary layers, both uniform and non-uniform. The boundary layer is found to modify the wave modes present at the magnetopause and to yield a criterion for the wavelength of the fastest growing surface waves. The paper concludes by questioning the extent to which the inferences from boundary layer models are model dependent and identifies areas where further work is needed or anticipated.     

Comets and asteroids in the Taurid complex: Remarks on a possible common origin

A supposition about the common origin of some cometary and asteroidal members of the Taurid complex is analyzed on the basis of their orbital evolution. It is shown that moments, in which the longitudes of perihelion of comet P/Encke, object (2201) Oljato and six other near-Earth asteroids amount to the value of longitude of perihelion of comet 1967 II Rudnicki, are close to the moment of previous perihelion passage of this long-period comet. Although the conjecture about the membership of comet Rudnicki in the Taurid complex is controversial one, nevertheless the presented results seem to be interesting in itself, and yield a contribution in favour of the hypothesis of the breakup of a giant comet some 10⁴ – 10⁵ years ago in the inner Solar System.     

A general relativistic effect in quasi-spherical objects as the possible origin of relativistic jets

Based on recently reported results, we present arguments indicating that sign changes in proper acceleration of test particles on the symmetry axis and close to the r=2M surface of quasi-spherical objects—related to the quadrupole moment of the source—might be at the origin of relativistic jets of quasars and micro-quasars.     

The origin of the Flora family

Evidence is presented indicating that the Flora family is of common origin. The distribution of proper elements and physical properties of Flora-family asteroids are compared with those of families believed to have formed from the catastrophic disruption of parent bodies. Differences in these orbital and physical properties suggest that the creation of the Flora family was more complex. Available evidence concerning the Flora family, together with recent models for the collisional evolution of the asteroids, suggests that this family may have originated from a binary or multiple asteroid. A mechanism in which the Flora family may have been produced by the disruption of a former major satellite of 8 Flora is presented and compared with other possible modes of formation.