Eruptive prominences of 1980 april 27 observed during STIP interval — X

Observations and analyses of two similar eruptive prominences on the north-east limb observed on 1980 April 27 at 0231 and 0517 UT, which are associated with the Boulder active region No. 2416 are presented. Both the eruptive prominences gave rise to white-light coronal transients as observed by C/P experiment of High Altitude Observatory on the Solar Maximum Mission. Type II and moving type IV radio bursts are reported in association with the first Hα eruptive prominence at 0231 UT. Both the Hα eruptive prominences showed pulse activity with a quasi-periodicity of about 2–4 min. We estimate a magnetic field in the eruptive prominence of about 100 G and a build-up rate ∼ 10²⁶ ergs^-1. The high build-up rate indicates that the shearing of the photospheric magnetic field, which fed the energy into the filament, was rapid. It is proposed that fast-moving Hα features must have initiated the observed coronal transients. From Hα, type II and coronal-transient observations, we estimate a magnetic field of 2.8 G at 1.9R⊙ from the disc centre, which agrees well with the earlier results.     

Morphological characters of the two-ribbon flare of 1981 May 13 and their explanation

We give a summary of the morphology of the two-ribbon flare of 1981 May 13. One striking feature is that the Ha flare began at about 0338' UT and the double-ribbon structure was formed about 0346, $\text{before}$ the impulsive phase of the radio 3 cm burst at 04 11 UT. The 3 cm radio burst flux beginning at 03 33 UT showed only slow, stepwise increases lasting half an hour until the impulsive phase and this type of increase is usually regarded to be a typical thermal process. Each step in the radio flux corresponded to a variation in the Ha flare, showing that the radio and Hα emissions during this period came from the same thermal source. In this paper, we explain this behaviour in terms of Hyder's model: we think that the magnetic trough supporting the solar prominence rose for some reason, causing the prominence matter (the dark filaments) to fall along the magnetic lines and to hit the chromosphere and trigger off the flare. We give rough estimates of the energy density, the height of prominence and the infall matter at the different radio increments. We also give a qualitative explanation for the appearances of the single-peak structure in the radio burst at 0411 and the covering of the sunspot shortly after at 04 13 and propose several possible mechanisms.     

A comprehensive analysis of the loop prominence of 1981 April 27

We make comprehensive analysis of morphological tracings and positional measurements of Hα images, white-light sunspot photographs and chromosphere velocity field, obtained at Yunnan Observatory, and hard X-ray images obtained by the Hinotori satellite, of the loop prominence of 1981 April 27. It seems likely that the observed loop is the projection of a post-flare loop system, and the associated flare occurred on the rear side of the solar disk. A two-ribbon flare such as in the Kopp-Pneuman model can satisfactorily explain all the observed features. The occurrence of such a flare seems likely from the evidence given by the data.     

Studies on post-flare loop prominence of 1981 April 27

By use of the H observations of the Astrophysical Observatory in Catania, Italy and the Purple Mountain Observatory in Nanking, China as well as hard X-ray and gamma-ray burst data from the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS), a major eruptive loop prominence was studied during the limb solar flare event of 1981 April 27.Our preliminary analysis shows that there seems to exist a second abrupt energy release for this event, almost 20 min after the end of the impulsive phase of the flare. This energy release is probably associated with the rapidity in upward motion or activation of the loop prominence.A possible candidate for such a process could be the reconnection of the old magnetic field with a newly emerging magnetic field.A theoretical gross estimate for the energy release and particle acceleration has also been made in this work. It appears that the proposed model for charged particle acceleration is very efficient.     

An explanation of the dimensions of penumbral filaments

Unstable pertubation modes exist in the magnetic field of penumbral electric current and I think the penumbral filaments are formed from the development of such modes. Under the short wave approximation the non-adiabatic dispersion equation is solved in the radial and transverse directions of the sunspot. From the condition of instability the length and width of the penumbral filament can be evaluated and it is found that the filament mode is static in the direction of the length and is non-moving in the direction of the width, that the penumbral filaments are a feature of the sunspot magnetic flow under gravity and that the presence of the filaments implies the existence of a twisted magnetic field.     

An explanation for the solar neutrino problem

A new mechanism of thermonuclear reaction is briefly introduced. It shows that a certain amount of thermonuclear reaction can take place in dense, low-temperature (T < 1 × 10⁵ K) plasmas. At a super-high temperature, it is in agreement with the old thermonuclear reaction mechanism first presented by Gamow and Bethe. As most regions in the Sun are at moderate and low temperature, a sufficient amount of fusion energy is generated therein. Therefore the solar central temperature in standard models must be decreased to about 13.8 × 10⁶ K. That would make the flux of high-energy neutrinos conform with the observational results.     

Optical counterpart of the radio event accompanying the 3B flare of 13 May 1981

Excepting intermittent type III activity, all the radio events over the frequency range 8–8000 MHz accompanying the initial stage of the 3B flare of 13 May, 1981 had their onset in a 2-min interval immediately preceding the peak of an impulsive Hα brightening (kernel) well away from the main flare. This kernel is identified as one footpoint of a loop of magnetic flux whose other end terminated in a transient brightening in an adjacent active region.     

An explanation of the discretization of redshifts of quasars

Published in Astrofizika, Vol. 38, No. 4, pp. 700–702, October–December, 1995.     

An explanation of the persistence of the Great Red Spot of Jupiter

An argument is given basing the persistence of the Great Red Spot of Jupiter on compensation of the natural decay of vorticity by collision with a portion of the vortices shed by the South boundary of the South Tropical Zone. The latter are deviated northward by Coriolis acceleration. The GRS itself is regarded as a Rankine vortex with a central depression revealing the coloration of a layer below.     

An explanation about the flat radio spectrum for Mrk 421

It is well known that a fiat radio spectrum is a common property in the spectral energy distribution of blazars.Although one-zone leptonic models are generally ...     

An explanation for time dependent variability of the solar dust ring

There are several observations showing an enhancement of infrared emission and optical polarization at a distance of 4R , (R is the angular radius of the Sun) implying a ring of dust in near-ecliptic orbit about the Sun; but there is an almost equal number of observations, which do not show any such enhancement. We plotted the observational results for the detection and the non-detection of the circum-solar dust on a diagram for the variation of the sun-spot number with time, and found that its detection and non-detection occurred near the solar minimum and maximum phases, respectively. We present the possibility that this phenomena is caused by an additional process, i.e., the Lorentz force acting on a charged dust particle. Since, at the maximum phase a dust particle in a near-solar region acquires a higher positive potential, and the solar magnetic field is very strong, the Lorentz force becomes dominant and can affect the orbit of the dust particle.     

Simultaneous radio and white light observations of the 1984 June 27 coronal mass ejection event

We present the two-dimensional imaging observations of radio bursts in the frequency range 25–50 MHz made with the Clark Lake multifrequency radioheliograph during a coronal mass ejection event (CME) observed on 1984, June 27 by the SMM Coronagraph/Polarimeter and Mauna Loa K-coronameter. The event was spatially and temporally associated with precursors in the form of meter-decameter type III bursts, soft X-ray emission and a H flare spray. The observed type IV emission in association with the CME (and the H spray) could be interpreted as gyrosynchrotron emission from a plasmoid containing a magnetic field of 2.5 G and nonthermal electrons with a number density of 10⁵ cm^–3 and energy 350 keV.On leave from Indian Institute of Astrophysics, Kodaikanal, India.     

An explanation for the light curve of Jupiter's and Saturn's satellites

Several satellites of Jupiter and Saturn show an asymmetric reflectance between the leading hemisphere (which is generally brighter for the inner satellites of both systems) and the trailing one (which is brighter for the outer satellites Callisto and Iapetus). In order to seek a unified explantation of these observational data we assume that, during the final phase of the satellite accumulation process, the surfaces were subjected to a heavy meteoroidal bombardment by the residual bodies in the circumplanetary protosatellite swarms. With suitable hypotheses about the orbital elements of these bodies, the resulting collision rate is anisotropic in an opposite way for inner and outer satellites, with a difference between the two hemispheres of the order of 10–20% for all satellites except Iapetus (for which the anisotropy is larger). We conclude that the model can qualitatively account for the observed effect, even if it is difficult to propose a detailed mechanism for changing the albedo properties of the satellite surfaces by means of meteoroidal collisions.     

Positional measurements on the eruptive loop prominence of 27 April 1981 and comparison with the X-ray sources

Using the Hα observational data from Yunnan Observatory, we have made position measurements on the eruptive loop prominence of 27 April 1981, and have compared the results with the positions of X-ray sources obtained by the hard X-ray telescope (SXT) on board the HINOTORI satellite. From the results of measurement and comparison, it is suggested that 1) The two mounds A and C at 0830 UT are extensions of two ribbons in the flare near the limb, which started before 0758 UT. 2) The central positions of two X-ray sources at 0756 UT are just situated at the top of the mound A and the mound C, respectively. The Hα footpoint corresponding to the main source of X-rays was behind the solar limb. The second source of X-rays corresponds to C₁ and C₂. 3) The X-ray sources were probably located near the footpoints of loops.     

Closed loop model of turbulent acceleration for the gradual phase of the radio burst of 1981 April 27

We propose a closed loop model of turbulent stochastic acceleration for the gradual phase of the radio burst of 1981 April 27. It can explain the various observed features in the spectrum, the rather long time of rise, the absence of X-ray bursts below 56 keV and of any detectable proton events.     

A possible explanation of reversed magnetic field features observed in NOAA AR 7321

Observations of reversed-polarity features in the chromosphere as well as in the photosphere in the form of magnetic gulfs or islands of opposite polarity have been reported recently. In this paper, we present a possible explanation for the appearance of reversed-polarity features observed in the chromospheric magnetograms of the NOAA AR 7321 observed during October 25–27, 1992. It is suggested that the large-scale reversed-polarity features may occur due to the twisting of the smaller-scale magnetic flux tubes in the layer between the photosphere and the chromosphere.     

An explanation for the soft X-ray excess in active galactic nuclei

We present a large sample of type 1 active galactic nuclei (AGN) spectra taken with XMM–Newton , and fit them with both the conventional model (a power law and blackbody) and the relativistically blurred photoionized disc reflection model of Ross & Fabian. We find that the disc reflection model is a better fit. The disc reflection model successfully reproduces the continuum shape, including the soft excess, of all the sources. The model also reproduces many features that would conventionally be interpreted as absorption edges. We are able to use the model to infer the properties of the sources, specifically that the majority of black holes in the sample are strongly rotating, and that there is a deficit in sources with an inclination >70°. We conclude that the disc reflection model is an important tool in the study of AGN X-ray spectra.     

An explanation for 13 consecutive day activities of Mrk 421

It is surprising to find an instance of migration in the peak positions of synchrotron spectral energy distribution components during the activity epochs of Markarian 421(Mrk 421),accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands.A geometric interpretation and standard shock or stochastic acceleration models of blazar emission have difficulty reproducing these observed behaviors.The present paper introduces a linear acceleration by integrating the reconnection electric field into the particle transport model for the observed behaviors of Mrk 421.We note that strong evidence for evolution in characteristic of multi-wavelength spectral energy distribution including shifting the peak frequency,accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands provides an important electrostatic acceleration diagnostic in a blazar jet.Assuming suitable model parameters,we apply the results of the simulation to the 13-day flaring event in March 2010 of Mrk 421,concentrating on the evolution of multiwavelength spectral energy distribution characteristic by shifting the peak frequency.It is clear that the ratio of the electric field and magnetic field strength plays an important role in temporal evolution of the peak frequency of synchrotron spectral energy distribution component.We suggest it is reasonable that the electrostatic acceleration is responsible for the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak frequency.Based on the model results,we assert that the peak frequency of the synchrotron spectral energy distribution component may signify a temporary characteristic of blazars,rather than a permanent one.     

An absorption event in the X-ray light curve of NGC 3227

We have monitored the Seyfert galaxy NGC 3227 with the Rossi X-ray Timing Explorer ( RXTE ) since 1999 January. During late 2000 and early 2001 we observed an unusual hardening of the 2–10 keV X-ray spectrum which lasted several months. The spectral hardening was not accompanied by any correlated variation in flux above 8 keV. We therefore interpret the spectral change as transient absorption by a gas cloud of column density 2.6 × 10²³ cm⁻² crossing the line of sight to the X-ray source. A spectrum obtained by XMM–Newton during an early phase of the hard-spectrum event confirms the obscuration model and shows that the absorbing cloud is only weakly ionized. The XMM–Newton spectrum also shows that ∼10 per cent of the X-ray flux is not obscured, but this unabsorbed component is not significantly variable and may be scattered radiation from a large-scale scattering medium. Applying the spectral constraints on the cloud ionization parameter and assuming that the cloud follows a Keplerian orbit, we constrain the location of the cloud to be   R ∼ 10–100  light-days from the central X-ray source, and its density to be   n _H∼ 10⁸ cm⁻³  , implying that we have witnessed the eclipse of the X-ray source by a broad line region cloud.