Observation of the solar eclipse 1966 May 20 in the region between 3.2 cm to 2.7 m wavelength

The solar eclipse 1966 May 20 was observed at 3.2, 10, 15, 20, 54, 59 cm, 1.05, 1.34 and 2.7 m wavelength by the observatories of the Heinrich-Hertz-Institut. The meter-wavelength observations were superposed by a noise storm. The result shows a region of enhanced radiation from the plages near the central meridian at the short wavelengths. Consulting additionally the observations made at Kiel, NERA, and Ondejov in the region of about 1.2 m wavelength it is possible to localize the source of the noise storm.     

13mm低温制冷谱线接收系统和星际水分子观测研究

为了开拓短厘米波单天线星际分子的观测和研究,在乌鲁木齐天文站２５ｍ射电望远镜１３ｍｍ低温制冷接收机的基础上,配置了声表面波频谱仪和谱线数据采集系统,组成了１３ｍｍ低温致冷谱线接收机．接收机前端是一个工作在低温２０Ｋ的低噪声放大器,本振是２２ＧＨｚ的锁相源．接收机的平均噪声温度为５０Ｋ．后端是一个宽带的（４０ＭＨｚ）高分辨率（４０ｋＨｚ）的声表波频谱仪．利用这套系统观测了一批已知的水脉泽源,观测系统正常,结果合理．观测结果表明,乌鲁木齐天文站良好的站址和２５ｍ射电望远镜给厘米波段星际分子谱线观测提供了一个很好的条件．     

Type I noise storms and the structure of the extreme ultraviolet corona

The spatial fine structure of the solar corona as observed in the EUV line Fexv is compared with the occurrence of major type I metric noise storms. In all cases, strong changes in the loop structure of the corona are observed. On the disk, these coronal changes are correlated to the emergence of new magnetic flux in the vicinity of existing large active regions. The reverse is demonstrated: during noise storm free periods no coronal changes can be observed. Noise storms at the limb seem to originate in open field configurations over active regions. In all cases, reconnection of coronal magnetic fields over large distances are the cause of noise storms rather than changes of magnetic fields within an active region. Noise storms disappear or are weak at the limb because of foreground absorption in chains of active regions. The observed intensities of active region loops at the limb show that a density of 1.3 × 10⁹ cm^?3 which corresponds to a plasma frequency of 100 MHz can occur over a wide variety of altitudes because active region loops are not in hydrostatic equilibrium.     

Radio mapping of the heliospheric current sheet

Synoptic plots of solar radio noise storms in the interval 1973 to 1984 are described. The dividing line between opposite noise storm polarities appears to be a good representation of the heliospheric current sheet out to displacements in latitude of ～ ± 50° from the solar equator. This result is surprising, because noise storms are closely associated with closed magnetic field regions near sunspots. The possibility that noise storm polarity is determined by mode coupling high in the corona, where field lines are open, can be ruled out by the available evidence. This leads us to conclude that it is the clustering in longitude of active region complexes which determines the sector structure of the interplanetary magnetic field.     

Deka-keV X-ray emission associated with the onset of radio noise storms

Radio noise storms show that suprathermal electrons (a few tens of keV) are present in the vicinity of active regions during several hours or even a few days. Where and how these electrons are energized is not yet well known. A flare-like sudden energy release in the active region is in general observed at the onset of noise storms, either as a fully developed flare or, more often, as a soft X-ray brightening without conspicuous H signature. In order to investigate to what extent electrons energized in the active region contribute to the noise-storm emission in the overlying coronal structures, we combine radio imaging (Nançay radioheliograph) with X-ray spectral observations at photon energies of a few keV (GOES) and - for the first time - around 10 keV (WATCH/GRANAT). In two of four studied events the WATCH data show a significant excess of the deka-keV count rate above the expectation from an isothermal fit to the GOES fluxes. Although the electron population producing the deka-keV X-ray emission would be energetic enough to power the simultaneous radio noise storm, the much longer duration of the radio emission requires time-extended particle acceleration. The acceleration probably occurs in the corona overlying the X-ray emitting region, triggered by the processes which give rise to the X-ray brightenings.     

Radio mapping of the heliospheric current sheet

Synoptic plots of solar radio noise storms in the interval 1973 to 1984 are described. The dividing line between opposite noise storm polarities appears to be a good representation of the heliospheric current sheet out to displacements in latitude of ± 50° from the solar equator. This result is surprising, because noise storms are closely associated with closed magnetic field regions near sunspots. The possibility that noise storm polarity is determined by mode coupling high in the corona, where field lines are open, can be ruled out by the available evidence. This leads us to conclude that it is the clustering in longitude of active region complexes which determines the sector structure of the interplanetary magnetic field.     

The Temporal Phenomena of Black Hole Transient XTE J1650-500 in Its 2001-2002 Outburst

Using the data observed by Rossi X-ray Timing Explorer, a systematic study of temporal phenomena of the black-hole transient XTE J1650-500 in its 2001–2002 outburst is presented. By using the time lag in the Fourier frequency domain, three characteristic frequency ranges are analysed, namely the band limited noise, red noise, and QPOs (Quasi-Periodic Oscillations). The properties and evolution behaviours in these frequency ranges may be dominated by different accretion regions. It is commonly believed that the smaller timescale corresponds to the more inner region. The low-hard state and hard intermediate state are especially highlighted. The results of data analysis are discussed in the framework of Lense-Thirring precession. Results are in favor of the disturbance propagation model for explaining the observed time lags. Although the timing analysis in the frequency ranges of band-limited noise and red noise is carried out, and a possibly existed inflection point is found, the model to explain them is still not well established. More work is needed to understand the innermost accretion region.     

On the characteristics of the solar active regions responsible for the generation of type III radio bursts at hectometric frequencies in August 1968

The RAE (Radio Astronomy Explorer) satellite observed enormous numbers of type III radio bursts at hectometric wavelengths from 13 to 25 August in 1968. The drift rate of these bursts reached a maximum around the middle of 20 August. This means that the source responsible for these bursts gradually moved on the solar disk in association with the rotation of the sun. During this period, there were two large active sunspot groups, MacMath Nos. 9593 and 9597, which were located in the southern hemisphere and adjacent to each other. By examining the observational data on solar flares, type I noise storm activity and energetic electron flux increases, it is shown that the active region, MacMath No. 9597 is responsible for the generation of these type III radio bursts. The relation between type III bursts producing electron beams and type I noise activity is briefly discussed and a model of this active region is qualitatively described.NAS-NRC Associate with NASA.     

Very Large Array,SOHO, and RHESSI Observations of Magnetic Interactions and Particle Propagation across Large-Scale Coronal Loops

Very Large Array (VLA) observations at wavelengths of 20 and 91 cm have been combined with data from the SOHO and RHESSI solar missions to study the evolution of transequatorial loops connecting active regions on the solar surface. The radio observations provide information about the acceleration and propagation of energetic electrons in these large-scale coronal magnetic structures where energy release and transport take place. On one day, a long-lasting Type I noise storm at 91 cm was seen to intensify and shift position above the northern hemisphere region following an impulsive hard X-ray burst in the southern hemisphere footpoint region. VLA 20-cm observations as well as SOHO EIT EUV images showed evolving coronal plasma that appeared to move across the solar equator during this time period. This suggests that the transequatorial loop acted as a conduit for energetic particles or fields that may have triggered magnetic changes in the corona where the northern noise storm region was seen. On another day, a hard X-ray burst detected at the limb was accompanied by impulsive 20- and 91-cm burst emission along a loop connecting to an active region in the same hemisphere but about 5′ away, again suggesting particle propagation and remote flare triggering across interconnecting loops.     

Non-linear effects of VLF noise generation by electron beams in the polar magnetosphere

A theory of VLF noise excitation by electron beams in the polar magnetosphere is proposed. Two modes of excited oscillations are considered: waves with frequencies in the vicinity of the lower hybrid resonance (LHR) from about 50 to 1000 kHz and whistler-mode waves in the frequency range of several kHz.The spectral distribution and the level of turbulent noise, having been excited by means of two counterstreaming electron beams, are deduced in magnetized plasma at the LHR frequency. It is also shown that the growth of noise up to the quasistationary level oscillates with time. Energy density of oscillations at the LHR frequency in the region of the dayside polar cusp agrees with the experimental data.The processes of whistler excitation by electron beams are discussed. The growth rate of excitation of whistler-mode by electrostatic oscillations at the LHR frequency is calculated.     

Projection Effects on Physical Parameters Obtained from Solar Vector Magnetograms

1 INTRODUCTION Magnetic field plays an important role in solar activity. The stressing and subsequent partialrelaxation of magnetic fields in the active regions are generally accepted to be the energy sourceof solar flares. To quantitatively study the extent of stressed magnetic field as distinct from itspotential field, Hagyard et al. (1984) defined a magnetic shear angle膖he azimuth differencebetween the observed transverse magnetic field vector and the computed potential field vectorth…     

Microwave geodesy by interferometric radiometry

The aim of this paper is to establish a new method-first introduced by Soviet scientists in 1972 —for mapping the Earth in the microwave region passively using the interference pattern which results by correlating the signals from two radiometers which presumably can be mounted in two or more moving satellites. In such a procedure, the image is enhanced progressively by synthetic composition similar to that achieved by air-borne synthetic aperture radar. The only question left open by the Soviet originators is if the signal-to-backround ratio was sufficiently strong to think about implementing the system in more practical terms. By practical terms, I mean the construction of electronics to surmount instrumental noise and possible atmospheric interference. These two latter questions are not addressed at this stage of the analysis, but only the basic question of signal-to-backround. It appears that the signal-to-backround ratio can be reduced to a minimum level determined by the fringe spacing created which in turn is a function of satellite separation. It is shown that the signal-to-backround ratio becomes proportional to target area over resolution cell size and is enhanced by a mechanism of defocusing the interferometric radiometer. This reduction in the field of view suppresses background noise which surrounds the target within the foot-print size, to the enhancement of signal-to-background ratio. In addition, near field viewing in the Fresnel region permits the determination of cross range as well as range by measurement of the difference in the radii of curvature of the impinging wave front at the different vantage points of the two detectors. Thus near-field interferometric viewing permits two-dimensional range determination contrary to the usual astronomical applications which are far field and only one dimensional.     

Improving performance of zoom-in cosmological simulations using initial conditions with customized grids

We present a method for customizing the root grid of zoom-in initial conditions used for simulations of galaxy formation. Starting from the white noise used to seed the structures of an existing initial condition, we cut out a smaller region of interest and use this trimmed white noise cube to create a new root grid. This new root grid contains similar structures as the original, but allows for a smaller box volume and different grid resolution that can be tuned to best suit a given simulation code. To minimally disturb the zoom region, the dark matter particles and gas cells from the original zoom region are placed within the new root grid, with no modification other than a bulk velocity offset to match the systemic velocity of the corresponding region in the new root grid. We validate this method using a zoom-in initial condition containing a Local Group analog. We run collisionless simulations using the original and modified initial conditions, finding good agreement. The dark matter halo masses of the two most massive galaxies at $z=0$ match the original to within 15%. The times and masses of major mergers are reproduced well, as are the full dark matter accretion histories. While we do not reproduce specific satellite galaxies found in the original simulation, we obtain qualitative agreement in the distributions of the maximum circular velocity and the distance from the central galaxy. We also examine the runtime speedup provided by this method for full hydrodynamic simulations with the ART code. We find that reducing the root grid cell size improves performance, but the increased particle and cell numbers can negate some of the gain. We test several realizations, with our best runs achieving a speedup of nearly a factor of two.     

Quiet Sun and slowly varying component at meter and decameter wavelengths

Comparison of maps of the Sun obtained over the period June 29 to July 8, 1982 at 169 MHz with the Nançay Radioheliograph and at 73.8, 50, and 30.9 MHz with the Clark Lake Radioheliograph shows that the slowly varying component at meter and decameter wavelengths is not always thermal emission. During the period under study weak noise storm continua were the most frequent sources of slowly varying component at 169 and 73.8 MHz. Most filaments show no radio counterpart on the disk. A streamer has been detected on the disk from 169 to 30.9 MHz with an optimum observability at 50 MHz. The brightest source of the slowly varying component from 73.8 to 30.9 MHz for most of the period was located above an extended coronal hole in a region where a depression was observed at 169 MHz. In favorable cases, electron densities can be derived from the positions of noise storms and radio streamers; these are in agreement with previous K-corona eclipse observations.     

Fast quadratic power spectrum estimators and the E–B decomposition

We describe a fast, quadratic power spectrum estimator for cosmic microwave background polarization fields, based on heuristically-weighted correlation functions. The method can handle real-world effects such as inhomogeneous or correlated noise, and arbitrary sky cuts. A significant feature is that the electric and magnetic polarization powers are separated exactly in the mean, even for observations covering only a small region of the sky, and with a negligible increase in computational cost. The method is illustrated with simulations for a large-area survey, and a future, deep magnetic-polarization survey.     

The flares of April 1980

We discuss the spatial and temporal characteristics of X-ray flares occurring in the active region NOAA2372 from April 6 to 13, 1980. The flares are seen to extend in most cases across the whole active complex, involving several magnetic features. They originate in an intermediate bipole, between the two main sunspots of the active region, where high magnetic shear was detected. A rapid expansion is seen in some cases, in conjunction with the start of the impulsive hard X-ray bursts. We also detect, in the late phases of some of the events, a large soft X-ray structure overlying the whole active region, which also shows up as a noise storm region at metric wavelengths. These large loops cool by heat conduction but, in some cases, Hα condensations seem to appear, probably as a result of magnetic compression and a condensation mode of the thermal instability. The topological aspects of the field configuration are discussed, in the context of flare models invoking magnetic reconnection at the site of the primary energy release. In such a model, the intermediate bipole is the natural site of initial magnetic reconnection, particle acceleration and heating. In one particular case of a flare observed at the limb, we find possible evidence of particle acceleration in a neutral sheet at the boundary between two clearly defined magnetic structures.     

Possible link between solar decimeter-wave microbursts and noise storms

A statistical study of long-lived solar microbursts (MB) at decimeter-wave frequencies has been performed for the first time. The data are obtained with the radio telescope RATAN-600 and have the form of one-dimensional scans of intensity and circular polarization with a sensitivity of about 5–10 Jy. MB fluxes and polarization degrees lie in the 0.001–0.1 s.f.u. and 10% to 100% intervals, respectively, and individual pulses have durations of one to two seconds. Microbursts can be observed in the same active region over several days. MB are compared to noise storms (NS) at meter-wave frequencies. The analysis indicates that MB are NS manifestations at decimeter-wave frequencies. The possible cause of the significant difference between the radio fluxes of MB and NS is analyzed. It is shown within the framework of a unified model of the generation of MB and NS radio waves that unlike type I bursts MB are associated with the incoherent mechanism of the generation of Langmuir waves. MB emission is, by its nature, closer to the continuous emission of noise storms, but it is pulse-like because of the high rate of pitch-angular diffusion.     

Hidden broad line regions and anisotropy in AGN

We discuss the recent advances made in the search for hidden broad line regions in Seyfert and Narrow Line Radio Galaxies (NLRG) using both spectropolarimetry and infrared spectroscopy/spectropolarimetry. Two important results which support the Grand Unification Theory are presented. In the first of these we report that the famous Seyfert 1 NGC 4151 has a scattered component to its broad line region, and is most likely an object where we view obliquely into its occulting torus. In the second, we show high signal to noise observations of scattered broad lines in the NLRG of 3C 234.     

Structure of the atmosphere of the magnetic star hd21699

The temperature distribution with depth in the atmosphere of the magnetic star HD21699 is modelled for each observed rotational phase using Hδ line profiles obtained with a signal to noise ratio S/N = 1000. The observed temperature distributions were averaged within and outside the region of the magnetic spots. It appears that these average temperatures are equal to within the limits of error. This shows that the magnetic field does not affect the physical condition of the matter in the star and does not disturb its thermodynamic state.