S. Hirose

Production of wiggled structure of AGN radio jets in the sweeping magnetic twist mechanism

Abstract We investigate the ‘wiggled structure’ of AGN radio jets by performing 3-dimensional magnetohydrodynamic (MHD) simulations based on the ‘Sweeping Magnetic-Twist’ model. The correlation between the wiggled structures of AGN radio jets and tails and the distribution of magnetic field in them suggests that the magnetic field plays an essential role, not only in the emission of synchrotron radiation, but also in the dynamics of the production of the AGN-jets–lobes systems (core, jets, tails, lobes, and hotspots) themselves. In order to produce such a systematic magnetic configuration, a supply of a huge amount of energy, in an organized form, is necessary. We think that the supply of this energy must come from AGN core. The most natural means of carrying this energy is in the form of the Poynting flux of torsional Alfven wave train (TAWT) produced in the interaction of the rotating accretion disk and the large scale magnetic field brought into it by the gravitational contraction. The propagation of the TAWT can produce a slender jet shape by the sweeping pinch effect from the initial large scale magnetic field. Further, wiggles of the jet can be produced by the MHD processes due to the TAWT. Our numerical results reveal that the structure of the magnetic jet can be distorted due to the helical kink instability. This results in the formation of wiggled structures in the jets as the TAWT encounters a domain of reduced Alfven velocity (either towards the boundary of the ‘cavity’ from which the mass contracted to the central core, or encounting smaller and denser clouds in the domain). The toroidal component of the field accumulates due to the lowered Alfven velocity, and produces a strongly pinched region, as well as the deformation of the jet into a writhed structure. The condition for this to occur corresponds to the Kruskal–Shafranov criterion of the linear case. If the intrinsic relationship between the wiggled structure of the jet shape and the magnetic field in the jets and tails as proposed in this paper is confirmed, it will influence the understandings of the AGN jets in a vital way. Such a systematic magnetic structure in the remote part of the jets and tails cannot be explained in most of the jet models except for the sweeping magnetic-twist model on which the present paper is based.

A Quadruple Magnetic Source Model for Arcade Flares and X-Ray Arcade Formations outside Active Regions. II. Dark Filament Eruption and the Associated Arcade Flare

A 2.5-dimensional MHD simulation based on the quadruple magnetic source model (Uchida et al.) was performed to deal with a dark filament eruption and the associated arcade flare. The numerical results are summarized as follows:

Observations Of Flares And Active Regions From Yohkoh, and Magnetodynamic Models Explaining Them

We discuss here some of the new aspects about solar flares and active regions found by the Solar X-ray Satellite Yohkoh, by taking advantage of the wider dynamic range and higher cadence observations with higher spatial resolution compared with the previous satellites. Those new aspects have lead us to new ways of understandings, with contradictions to the previous views about flares and active regions that are widely conceived for a long time. We give some models that explain those newly revealed observational results.

Triaxial deformation in 10Be

The triaxial deformation in 10 Be is investigated using a microscopic a1a1n1n model. The states of two valence neutrons are classified based on the molecular-orbit ~MO! model, and the p orbit is introduced about the axis connecting the two a clusters for the description of the rotational bands. There appear two rotational bands comprised mainly of K p 50 1 and K p 52 1 , respectively, at low excitation energy, where the two valence neutrons occupy K p 53/2 2 or K p 51/2 2 orbits. The triaxiality and the K mixing are discussed in connection to the molecular structure, particularly to the spin-orbit splitting. The extent of the triaxial deformation is evaluated in terms of the electromagnetic transition matrix elements ~Davydov-Filippov model, Q-invariant model! and density distribution in the intrinsic frame. The obtained values turned out to be g515°‐20°.

Relativistic Mean Field Models and Nucleon-Nucleon Interactions

We investigate the connection between relativistic mean field models and the bare nucleon-nucleon interaction by using a realistic interaction in the nuclear medium. Starting from a nonrelativistic bare potential and by employing a G-matrix formalism we derive an effective interaction in the nuclear medium that depends on its density. We show that its medium- and long-range components can be described to a good extent by an effective density-dependent one-boson-exchange (OBE) potential. For a good fit of the OBE to the G-matrix potential the following degrees of freedom have been found to be necessary: an isoscalar scalar S (σ-meson), an isoscalar vector V (ω-meson), an isovector scalar TS (δmeson), an isovector vector TV (ρ-meson), and an isovector pseudoscalar PS (π-meson) Yukawa field. This allows us to extract the mass and the coupling strength of the various mesons at different densities of nuclear matter. In such a way, we investigate the densitydependence of these parameters and the influence of many-body and multi-scattering effects. We find that with increasing density of the nuclear medium mσ is constant to a good approximation, mδ decreases quite strongly, while mω and mρ decrease rather weakly. The coupling strengths of the fields also show a rather weak decreasing tendency. Furthermore it turns out that the extracted values of the meson fields masses and couplings are rather consistent with the parameters of effective mesons of recent RMF phenomenologies. Finally, we find that the tensor force of the bare nucleon-nucleon interaction is essential to explain the dominance of the σ-field for the attraction. This makes RMF models more consistent with ab initio calculations.

Magnetodynamic Formation Of Jets In Accretion Process Of Magnetized Mass Onto The Central Gravitator — Cases Of Forming Stars And Active Galactic Nuclei

A magnetodynamic model to deal with the acceleration and collimation of jets as a part of the global process of gravitational contraction of the magnetized gas to the central gravitator is discussed. We first review its application to the star forming jet case with several observational supporting evidence. Then, a justification will be given for the extension of this to the AGN jet case, despite of the difference in orders of magnitudes in the scales as well as in the physical parameters. The results of actual application of this magnetodynamic mechanism to the AGN case will be presented together with the discussions for the origin of the radio lobes and hotspots, and we show that this mechanism can explain the enhancement of accretion and the formation of the jet + lobe system consistently with the genetic consideration of the system.

The Exotic Clustering and Nucleon-Nucleon Correlations in Light Neutron-Rich Nuclei

Fig. 1. Schematic diagram of Be. Using two α+α+2n model, we theoretically investigate the structure of 10Be. The motion of two valence neutrons is described based on MolecularOrbit model and we discuss triaxial deformation of 10Be. 1) An α-α core is an axial symmetric system. When two valence neutrons occupy time-reversal orbit with each other, the system is still axial symmetric. However, when the correlation of two valence neutrons becomes more important and they form di-neutron, the charge distribution of this system deviate from axial symmetric shape due to the recoil effect (see Fig. 1). We study this effect by a microscopic model.

HOMOLOGOUS FLARE SERIES OF FEBRUARY 1992

We describe the series of flares of 21-February-1992, 24-February-1992 and 27-February-1992, which we consider to be a homologous flare series observed with Yohkoh SXT. If the events are homologous, similar features will be seen from different perspectives during the series. Thus, we use the time scale normalized by the total duration for each flare obtained from the GOES data and define flare phases to compare the corresponding features in the series of events. From this analysis, along with the corresponding Kit Peak magnetograms and Mitaka Hα data, we examine the corresponding features seen from different angles, and discuss their three-dimensional structures.

Several Problems with Classical “Reclosing of Opened-up Simple Arcade” Models for Arcade Flares and Arcade Formation Events

Many researchers usually have the so-called classical models by Sturrock and others in mind when they describe the arcade flaring processes. Several new findings derived from the Yohkoh-SXT observations, however, seem to support anti-standard quadruple source model proposed by Uchida (1980).

3-D structure of arcade type flares deduced from soft x-ray observations of a homologous flare series

Abstract There occurred three flares in active region NOAA 7070 over seven days in February 1992. One of them was seen at the east limb of the Sun, and the others were seen on disk. After confirming the homology among these flares, we used them to derive the 3-D coronal structure by making use of the images at some common phases, but seen along three different lines of sight by Yohkoh/SXT. We found some new characteristic features: The so-called “cusped arcade” turned out to be different from the “flare arcade” as widely conceived. Rather it is a thin “elongated arch” seen with a shallow oblique angle. Four magnetic sources participate in these flares in an essential way. An X-ray “blob” with a heated surface (rising dark filament) was pulled out by the expansion of high loops, which connect the top of the preflare cusp back to the photosphere on both sides, in the preflare phase of February 21. This opposite to the X-ray “blob” pulling the surrounding loops open as assumed in the “classical” flare models.