Transition probabilities in highly ionized p2 and p4 configurations

Line strengths of magnetic dipole and electric quadrupole transitions in the configurations 2p2, 2p4, 3p2 and 3p4 are calculated using interpolated values of spin-orbit interaction parameters and unperturbed energies of the levels. Probabilities of the important ground state transitions are tabulated in the four isoelectronic sequences through the following net charges: 17(2p2), 13(2p4), 15(3p2), 13(3p4).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31969/1/0000011.pd

Large amplitude oscillatory motion along a solar filament

Large amplitude oscillations of solar filaments is a phenomenon known for more than half a century. Recently, a new mode of oscillations, characterized by periodical plasma motions along the filament axis, was discovered. We analyze such an event, recorded on 23 January 2002 in Big Bear Solar Observatory H$\alpha$ filtergrams, in order to infer the triggering mechanism and the nature of the restoring force. Motion along the filament axis of a distinct buldge-like feature was traced, to quantify the kinematics of the oscillatory motion. The data were fitted by a damped sine function, to estimate the basic parameters of the oscillations. In order to identify the triggering mechanism, morphological changes in the vicinity of the filament were analyzed. The observed oscillations of the plasma along the filament was characterized by an initial displacement of 24 Mm, initial velocity amplitude of 51 km/s, period of 50 min, and damping time of 115 min. We interpret the trigger in terms of poloidal magnetic flux injection by magnetic reconnection at one of the filament legs. The restoring force is caused by the magnetic pressure gradient along the filament axis. The period of oscillations, derived from the linearized equation of motion (harmonic oscillator) can be expressed as $P=\pi\sqrt{2}L/v_{A\phi}\approx4.4L/v_{A\phi}$, where $v_{A\phi} =B_{\phi0}/\sqrt{\mu_0\rho}$ represents the Alfv\'en speed based on the equilibrium poloidal field $B_{\phi0}$. Combination of our measurements with some previous observations of the same kind of oscillations shows a good agreement with the proposed interpretation.Comment: Astron. Astrophys., 2007, in pres

SOHO/SUMER Observations of Prominence Oscillation Before Eruption

Coronal mass ejections (CMEs), as a large-scale eruptive phenomenon, often reveal some precursors in the initiation phase, e.g., X-ray brightening, filament darkening, etc, which are useful for CME modeling and space weather forecast. With the SOHO/SUMER spectroscopic observations of the 2000 September 26 event, we propose another precursor for CME eruptions, namely, long-time prominence oscillations. The prominence oscillation-and-eruption event was observed by ground-based H$\alpha$ telescopes and space-borne white-light, EUV imaging and spectroscopic instruments. In particular, the SUMER slit was observing the prominence in a sit-and-stare mode. The observations indicate that a siphon flow was moving from the proximity of the prominence to a site at a projected distance of 270$''$, which was followed by repetitive H$\alpha$ surges and continual prominence oscillations. The oscillation lasted 4 hours before the prominence erupted as a blob-like CME. The analysis of the multiwavelength data indicates that the whole series of processes fits well into the emerging flux trigger mechanism for CMEs. In this mechanism, emerging magnetic flux drives a siphon flow due to increased gas pressure where the background polarity emerges. It also drives H$\alpha$ surges through magnetic reconnection where the opposite polarity emerges. The magnetic reconnection triggers the prominence oscillations, as well as its loss of equilibrium, which finally leads to the eruption of the prominence. It is also found that the reconnection between the emerging flux and the pre-existing magnetic loop proceeds in an intermittent, probably quasi-periodic, way.Comment: 14 pages, 8 figures, submitted for publication in A&

Near-Limb Zeeman and Hanle Diagnostics

"Weak" magnetic-field diagnostics in faint objects near the bright solar disk are discussed in terms of the level of non-object signatures, in particular, of the stray light in telescopes. Calculated dependencies of the stray light caused by diffraction at the 0.5-, 1.6-, and 4-meter entrance aperture are presented. The requirements for micro-roughness of refractive and reflective primary optics are compared. Several methods for reducing the stray light (the Lyot coronagraphic technique, multiple stages of apodizing in the focal and exit pupil planes, apodizing in the entrance aperture plane with a special mask), and reducing the random and systematic errors are noted. An acceptable level of stray light in telescopes is estimated for the V-profile recording with a signal-to-noise ratio greater than three. Prospects for the limb chromosphere magnetic measurements are indicated.Comment: 11 pages, 3 figure

The Metaphor of Circle: Stanislavski, Phenomenology of Roundness and High Yoga

Stanislavski’s Eastern influence and his persistent fascination with Yoga is an established area of research. Stanislavski has two major yogic influences in the System: Hatha Yoga and Raja Yoga. The first is about training the body through postures, movements, stances and breathing exercises to make it active, relaxed and energetic. The second includes a range of exclusive practices on concentration and visualization that are an integral part of the actor’s creativity. However, in the current research, there is a clear lack of a comprehensive practical method that informs Stanislavski’s use of yogic practice in the System: what specific yogic exercises were used and what synergies were developed in the training? Scholars have, so far, only explored Stanislavski’s literary legacy of his encounter with yoga, identifying the Sanskrit terms appeared in his writings such as prana for breathing and the Indian anecdotes he used when answering the questions of his students. Focusing on the metaphor of the circle, the phenomenology of roundness and the Deleuzian notions of ‘the invisible forces of sensations’ and ‘the body becomes an event itself’, the present study, for the first time, offers useful insights into the fundamental principles of yoga and their methods of practice as a way of developing a new training to understand the significance of Stanislavski in the 21st century

Historical Sunspot Observations: A Review

Early observations of sunspot were realised by the naked eye. Possible utilization of these records for studying the long-term change in the Sun is discussed here. Other historical sunspot observations with camera obscuras are also discussed. Moreover, the best record of the behaviour of the Sun exists for the last four centuries thanks to the observations of sunspots with telescope. These observations should allow us to know the number, position, and area of sunspots as well as some relevant episodes (Maunder Minimum, optical flares, etc.). Rudolf Wolf developed the first reconstruction of solar activity in the 19th century. The next reconstruction was made by Hoyt and Schatten in 1998 by improving the database and using a new methodological approach. Here some mistakes, pending tasks and minor improvements are discussed.Comment: 19 pages, 6 figures, to be published in Adv. Space Re

Dissipative instabilities in a partially ionised prominence plasma slab: II. The effect of compressibility

This present study deals with the dissipative instability that appears in a compressible partially ionised plasma slab embedded in a uniform magnetic field, modelling the state of the plasma in solar prominences. In the partially ionised plasma, the dominant dissipative effect is the Cowling resistivity. The regions outside the slab (modelling the solar corona) are fully ionised, and the dominant mechanism of dissipation is viscosity. Analytical solutions to the extended magnetohydrodynamic (MHD) equations are found inside and outside of the slab and solutions are matched at the boundaries of the slab. The dispersion relation is derived and solutions are found analytically in the slender slab limit, while the conditions necessary for the appearance of the instability is investigated numerically for the entire parameter space. Our study is focussed on the effect of the compressibility on the generation and evolution of instabilities. We find that compressibility reduces the threshold of the equilibrium flow, where waves can be unstable, to a level that is comparable to the internal cusp speed, which is of the same order of flow speeds that are currently observed in solar prominences. Our study addresses only the slow waves, as these are the most likely perturbations to become unstable, however the time-scales of the instability are found to be rather large ranging from $10^5$-$10^7$ seconds. It is determined that the instability threshold is further influenced by the concentration of neutrals and the strength of the viscosity of the corona. Interestingly, these two latter aspects have opposite effects. Our numerical analysis shows that the interplay between the equilibrium flow, neutrals and dispersion can change considerably the nature of waves. Despite employing a simple model, our study confirms the necessity of consideration of neutrals when discussing the stability of prominences under solar conditions

Soft solar X-rays and solar activity

Minor Hα activity, consisting of small brightenings and small, surgelike spikes, was observed to take place above an active center at the solar limb in good time-association with small fluctuations in the soft X-ray background flux, suggesting that even small dynamical events seen optically are associated with coronal heating. The ratio of Hα flux to soft X-ray flux in some of the surges was approximately the same as the ratio already established for flares. The total energy dissipated by the events in a 24-hour period is estimated; it is approximately equivalent to that released by one flare of imp 1 per day.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43719/1/11207_2004_Article_BF00155785.pd

Soft solar X-rays and solar activity

Soft solar X-rays in the wavelength interval 8–12 Å were observed from OSO III. The totality of the observations that were made between 9 March, 1967, and 18 May, 1968, is summarized graphically and compared to the course of solar activity as observed at other wavelengths, with particular emphasis upon visible activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43715/1/11207_2004_Article_BF00146064.pd

Decay time of type III solar bursts observed at kilometric wavelengths

Type III bursts were observed between 3.5 MHz and 50 kHz by the University of Michigan radio astronomy experiment aboard the OGO-5 satellite.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43731/1/11207_2004_Article_BF00156186.pd