[en] We present an MHD model for the galactic center lobes (GCL) by using an axisymmetric 2.5-dimensional MHD simulation. According to our model, GCL is a low-energy jet emanating from the H_II gas disk extending beyond r ∼ 100 pc from the galactic center. The model is based on the 'sweeping-magnetic-twist' mechanism developed by the authors for the production of cosmic jets, where the gas in the surface layer of the contracting disk is lifted up by the J x B force in the relaxing magnetic twist, which is generated by the interaction of the rotation of the contracting disk with the poloidal magnetic field. We incorporate the realistic gravitational potential suitable for the galactic center region, in which the rotational velocities are approximately constant for r = 20 - 100 pc. The difference between the models with this realistic potential and those with the potential due to a point mass is examined in detail. On the basis of the numerical results, we present a scenario for the formation of the GCL. (author)

[en] The interaction of a bipolar molecular flow with interstellar condensations is examined (using the sweeping-magnetic-twist model) by performing 2.5-dimensional MHD numerical simulations. A torsional Alfven wave propagating with a hollow cylindrical bipolar flow interacts with the condensation, and the magnetic twist accumulates in the region between the flow and the condensation, since the Alfven velocity in the condensation is smaller than that in the ambient medium. The stored magnetic twist increases with time, causing various nonlinear effects, such as a pinching of the gas in the near-axis region, or an upward-acceleration of the gas in the condensation. Two cases for the condensation configuration are examined: spherical shape and ring-like shape. In the spherical case, the condensation, itself, is squeezed by the pinch effect. In the ring-shaped case, the hot gas near the axis is pinched and flow is generated along the axis due to an enhanced gas pressure resulting from the pinch. The velocity of the hot flow is comparable to that of the original cold bipolar flow. The results in the ring-shaped case may explain the observed characteristics in the velocity field around the blob observed in the L1551 flow, supporting the interpretation (Uchida et al. 1987; AAA 44.131.270) that the mass in the dense blob lying in the L1551 flow did not come from the source of the flow, but pre-existed there in the molecular cloud. (author)

[en] We present a nonsteady magnetodynamic mechanism for the formation of astrophysical jets in a magnetized accretion disk system. The dynamical processes in the contraction of a rotating disk, which is penetrated by a magnetic field parallel to the rotation axis, are investigated by using axially symmetric 2.5-dimensional MHD numerical simulations. As the rotating disk contracts, it pulls the magnetic field towards the center as well as to the azimuthal direction, producing a helically twisted magnetic field, and as the magnetic twist is accumulated and begins to relax along the poloidal field, the gas in the surface layers of the disk is pushed out to the polar directions by the J x B force with the relaxing magnetic twist. It is shown that the accelerated gas is collimated by the magnetic field and forms a supersonic bipolar jet which has a hollow cylindrical shell structure with helical motion in it. A considerable fraction of the gravitational potential energy released in the contraction of the disk is transformed to the kinetic energy of the jet through the action of the magnetic field. Also, angular momentum is carried away from the disk by the magnetic torque especially in the phase of the jet formation, and this allows the disk to keep contracting towards the gravitating center and can continue the ejection of the jet. (author)

[en] The accretion of magnetized nebular mass to a young star after the formation may take a form in which the accreted magnetized mass is first buffered by the stellar magnetic field, and then leaks into the stellar field region through magnetic reconnection at the magnetically neutral ring formed in the equatorial plane. The nebular mass is condensed in the buffering process, and the potential energy of this condensed mass is converted into the kinetic energy in the infall after the leakage. A high temperature region is produced when the infalling material crashes at the stellar surface and a shock produced in the crash propagates back upwards along the tail of the infalling material. The strength of the shock increases rapidly as the shock propagates into the tail of the inflow which has a large gradient in density, and the material in the tail is blown off by the shock along the magnetic field. The rate of mass loss in this mechanism, in which the flow is bent towards the polar directions by the effect of the magnetic field, can be as high as 10^-8 Msub(solar mass)yr^-1, and this, together with the morphology, suggests that the present mechanism may explain the relation of Herbig-Haro objects and/or of bipolar nebulae observed in millimetric CO lines to young stars. (author)

[en] Oscillations observed in sunspot umbras are interpreted as a vertical motion in the atmosphere induced by a standing Alfven wave trapped in the region between the overstable layer under the photosphere and the chromosphere-corona transition layer. The Alfven wave motion is considered to be excited by the overstable convection occurring at the bottom of the abovementioned oscillating layer, and waves with special frequencies are selected as eigen-mode waves standing in the ''cavity,'' while other waves which are out of phase with themselves after reflections will disappear. It is shown by solving the eigen-value problem that the fundamental eigen frequency falls in a range around 0.04 rad s^-1 (corresponding to 140-180 s) for the condition in the umbra of a typical spot, and also that the eigen frequencies do not depend greatly on the circumstantial physical or geometric parameters of the model atmosphere, such as the temperature in the layer, or the height of the transition layer, etc. The eigen frequencies, however, depend on the Alfven velocity at the base of the oscillating layer (or at the top of the overstable layer), but the latter quantity, which represents the stiffness of the magnetic tube of force against the overturning motion, takes roughly a common value for different sunspots according to SAVAGE's (1969) stability analysis of the umbral atmosphere against thermal convection, and thus gives a comparatively narrow range of resonant frequencies. In addition to the selection mechanism for oscillations of 140-180-s period, some other aspects of the oscillation, such as the relation to the running penumbral waves, are discussed. (auth.)

[en] Although radiotherapy has proven of great therapeutic value in the treatment of malignant tumors, it should also be borne in mind that radiation has a serious potential risk of giving rise to a secondary malignancy. We recently experienced 2 cases each of carcinoma and sarcoma arising in the irradiated areas long after radiation therapy for malignant tumors. In these 4 cases, 2 males and 2 females, the primary neoplastic diseases were squamous cell carcinoma, epidermoid carcinoma, carcinoma of unknown pathology and malignant lymphoma, and the secondary tumors were epidermoid carcinoma, squamous cell carcinoma, osteosarcoma and chondrosarcoma, respectively. The sites of occurrence of these malignancies were invariably in the maxillary region; the mean latent period was 15 years, aside from an infantile case with a latent period of 5 years. In view of the primary diseases being malignant tumors the following criteria were set up for the diagnosis of radiation-induced malignancies: (1) the site of occurrence is within the confines of a previously irradiated area, (2) the latent period is prolonged and (3) the malignancy occurs as a double tumor. Therapy was primarily by operation. The prognosis was exceedingly ominous, the average survival time being 22 months. This was probably and mainly because of rapidity of tumor growth. Thus, the secondary tumors had already spread back to inward by the time they were first discovered. This should be kept in mind during a long-term follow-up of patients receiving radiotherapy for malignancy. (author)

[en] It has been found from ¹³CO observations using the Nagoya 4-m telescope that the blue- and redshifted contours (e.g., V_LSR ± 0.5 kms^-1) in the ρ Oph streamer (north) are systematically separated from each other, with blue on the north-west side and red on the south-east side of the curved axis of the streamer, respectively. Our interpretation is that the streamer is spinning around its axis. We propose a picture in which the streamer is a 'drain' through which the angular momentum is carried away from a massive cloud of active star formation by the magnetic twist. This draining allows the star-formation process in the massive cloud to occur with an enhanced rate. (author)

[en] The detailed structure and velocity field in the L1551 CO bipolar flows were observed by using the 45-m millimetric-wave telescope at Nobeyama. The observations were made in January and April of 1985 and supplemented in January of 1986 in the 115 GHz ¹²CO J = 1 - 0 line with spatial and spectral resolutions of 18 ench and 250 kHz (0.65 km s^-1 in velocity), respectively. It was revealed as the result that the bipolar flow lobes have a clear hollow cylindrical structure and that both lobes are likely to be spinning with a velocity of 1 - 2 km s^-1 in the same direction as that of the disklike object claimed by Kaifu et al. (1984; AAA 37.131.128) in the CS 49-GHz line. The longitudinal velocity of the flow increases with distance along the axis up to 0.15 pc from IRS-5, the central object. These characteristics coincide well with those predicted by the magnetodynamic theory proposed by Uchida and Shibata (1985; AAA 40.131.174), and indicate the essential importance of the magnetic field in producing such flows. It is also suggested that the angular momentum loss due to the magnetodynamic process is important in the star formation itself. (author)