Eruption of a helically twisted prominence

In this paper we analyze the eruption of a prominence, characterized by a helical-like structure and by a non-linear rising motion. We approximated the prominence as a cylindrical curved flux tube and estimated the behaviour of several geometrical parameters during the activation and the eruption phases. We determined that, at the onset of the activation, the number N of turns of a magnetic field line over the whole length of the prominence was 5.0, while the value of the ratio P/r ₀ between the pitch of the magnetic field lines and the prominence width was 0.45. These values are in good agreement with those predicted by the kink-mode instability. Moreover, we found a decrease of the total twist of one helical thread from 10 to 2 during the prominence eruption, indicating a relaxation of the magnetic field towards a less twisted configuration. We conclude that the prominence was initially destabilized by the kink-mode instability and, not succeeding in finding a new equilibrium configuration, it erupted.     

Взаимооействие Излучения Рентгеновскооо Истооника с АтмосФерой Нормальной Звезды в Тесных Двойных Системах

, . : , . , . . ( ) . . . HZ Her=Her X1, . . , . , ., hv 15–30 . , . Sco X1 .     

Комптоновское рассеяние в источниках с синхротронной реабсорбцией

, ( ). n =3–5, T _e =4T _b (1 + ), - ( ) ,T _b - . , . , . W _H , ,n =3, =1. n =3–5(E), (E) , , = 1 – (), |()| < 1, |(E)| < 1. 3 273.     

Evolution of helically twisted prominence structures of March 11, 1979

Helical structures are generally associated with many eruptive solar prominences. Thus, study of their evolution in the solar atmosphere assumes importance. We present a study of a flare-associated erupting prominence of March 11, 1979, with conspicuous helically twisted structure, observed in H line center. We have attempted to understand the role played by twisted force-free magnetic fields in this event. In the analysis, we have assumed that the helical structures visible in H outline the field lines in which prominence tubes are embedded. Untwisting of observed prominence tubes and later, formation of open prominence structures provide evidence of restructuring of the magnetic field configuration over the active region during the course of prominence eruption. Temporal evolution of the force-free parameter is obtained for two main prominence tubes observed to be intertwined in a rope-like structure. Axial electric currents associated with the prominence tubes are estimated to be of the order of 10¹¹ A which decreased with time. Correspondingly, it is estimated that the rate of energy release was 10²⁸ erg s^–1 during the prominence eruption.     

Holes in the Hα Eruptive Prominence Structure

The eruptive prominence observed on 27 May 1999 in H at Ondejov Observatory is analyzed using image-processing techniques. To understand the physical processes behind the prominence eruption, heated structures inside the cold H prominence material are sought. Two local minima of intensity (holes), the first above and the second below the erupting H prominence, have been found in the processed H images. A comparison of H images with the SOHO/EIT and Yohkoh/SXT images showed: (a) the cold H prominence is visible as a dark feature in the EIT images, (b) the upper local minimum of intensity in the H image corresponds to a hot structure seen in EIT, (c) the lower minimum corresponds to a hot loop observed by SXT. The physical significance of the H intensity minima and their relation to the hot structures observed by EIT and SXT is discussed. The time sequence of observed processes is in favor of the prominence eruption model with the destabilization of the loop spanning the prominence. For comparison with other events the velocities of selected parts of the eruptive prominence are determined.     

Determination of the total amount of hydrogen atoms in a quiescent prominence

A brief quantitative review of the determination of the chemical composition of the Sun and stars is given. The method of estimation of the total amount of hydrogen atoms in a prominence is considered.The values of relative abundances of some infrequent elements in the solar atmosphere are refined using metal emission lines in the spectrum of a quiescent prominence. The most probable values of relative abundances for itrium _Y1×10^–9, zirconium _Zr2×10^–9, and scandium _Sc3.8×10^–9 are derived.     

Effect of perturbations on the stability of triangular points. In the restricted problem of three bodies with variable mass

The effect of small perturbations and in the coriolis and the centrifugal forces respectively on the stability of the triangular points in the restricted problem of three bodies with variable mass has been studied. It is found that the range of stability of triangular points increases or decreases depending upon whether the perturbation point (, ) lies in one or the other of the two parts in which the (, ) plane is divided by the line J₈–J₉=0 where J₈ and J₉ depend upon , the constant due to the variation in mass governed by Jeans' law.     

Some calculations bearing on the heating and cooling of quiescent prominences

We discuss the evolution of pulses of heat both along and perpendicular to magnetic fields threading quiescent prominences. We show that while heating of prominence material can take place on a time scale of the order 10³ s (of the same order as the observed winking of H light from prominences and also of the same order as the dynamical Alfvén time scale across a prominence sheet) individual flux tubes are effectively thermally insulated from neighboring tubes, since the transverse (to the ambient supporting magnetic field) heat conduction time scale is of order 10⁴ yr. The exact solution to the one-dimensional parallel heat conduction problem is shown to differ significantly from the approximate solution reported by Ioshpa (1965). We also suggest that uneven heating of a quiescent prominence by the surrounding solar corona may be a contributory mechanism for surges and/or the observed winking phenomenon - both of which are recorded in many quiescent prominences. The signature of such a temperature pulse would be a sharp (10³ s) brightening of continuum radiation with a correlated decrease in the free-bound emission, followed by a slow (10⁴ s) recovery of both to their pre-heat pulse levels.     

Kink instability of solar coronal loops as the cause of solar flares

Solar coronal loops are observed to be remarkably stable structures. A magnetohydrodynamic stability analysis of a model loop by the energy method suggests that the main reason for stability is the fact that the ends of the loop are anchored in the dense photosphere. In addition to such line-tying, the effect of a radial pressure gradient is incorporated in the analysis.Two-ribbon flares follow the eruption of an active region filament, which may lie along a magnetic flux tube. It is suggested that the eruption is caused by the kink instability, which sets in when the amount of magnetic twist in the flux tube exceeds a critical value. This value depends on the aspect ratio of the loop, the ratio of the plasma to magnetic pressure and the detailed transverse magnetic structure. For a force-free field of uniform twist the critical twist is 3.3, and for other fields it is typically between 2 and 6. Occasionally active region loops may become unstable and give rise to small loop flares, which may also be a result of the kink instability.     

Некоторые асимптотические решения в ограниченной задаче трех тел

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Some asymptotic solutions in the restricted problem of three bodies by L. G. Lukjanov.

Some particular solutions of the plane restricted problem of three bodies in the form of Liapunov's series are obtained. These solutions asymptotically approach the Lagrange solutions. Convergence is proved.

     

Сопоставление модели карлсона с моделью сплошной среды

, (1962, 1963) . , (1) (2) .     

Some fundamental elements of universe mechanics

An essential part in the mechanics under study is taking into consideration the effect of motions of the Universe objects upon that of an individual one surrounded by them including those infinitely far from it. Only macro-objects of the Universe are meant here.

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Zusammenfassung Ein wesentlicher Bestandteil der Mechanik unter unserer Betrachtung ist die Berechnung des Einflusses auf die Bewegung eines individuellen Objektes von Bewegungen der Universum Objekte die es umringen einschließlich jene Objekte, die unendlich entfernt sind. Nur Makroobjekte des Weltalles sind in der Absicht dabei.

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Динамические равновесные плазменные конфигуации и физика магнитосферы

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Космическое черенковское излучение

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Околозвездные оБлака по данным 2800 Mgii

2800 Mgii (. 1). (N ⁺/N ₁1000) , , (N ⁺/N ₁10). , . —, , . — . : ; 0.002 1 , 0.1 ; () 100 ^–3; ; ; , 10 ; 10^–4 1 . 2800 Mgii .     

Формирование Универсальных и Диффузионных Участков Нелинйных Спектров Релятивистских Электронов В Пространственно Ограниченных Источниках

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Возможный механизм радиоизлучения пульсаров

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Структура и эволюция Сверхмассивных вращающихся магнитных политроп

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The structure of rotating magnetic polytropes is considered in Roche approximation. Investigation of the influence of poloidal as well as toroidal magnetic fields on the conditions of the beginning of matter outflow due to rotational instability is carried out. The influence of the turbulent convection and twisting of magnetic force-lines on the time of smoothing of differential rotation is considered. The estimate of the magneto-turbulence energy generated by differential rotation is presented. Both maximum possible energy output and duration of the quasi-statical evolution phase up to the appearance of hydrodynamic instability due to the effects of general relativity are calculated for supermassive magnetic polytropes of index three with uniform or differential rotation. The radius-mass relation is obtained for supermassive differentially-rotating magnetic polytropes referring to the longest part of the quasi-statistical evolution stage; some consequences are pointed out, including the period-luminosity relation.The evolution of the considered models of supermassive rotating magnetic polytropes with different character of rotation and different geometry of a magnetic field is discussed.The results obtained are summarized in the last section.

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English translation will appear in the next issue ofAstrophys. Space Sci.

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Receipt delayed by postal strike in Great Britain     

Метагалактические протоны сверхвысоких энергий

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Результаты и проблемы исследования синхротронной неустойчивости

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