Transient phenomena in the energetic behind-the-limb solar flare of september 29, 1989

The powerful cosmic ray flare of Sept. 29, 1989 occurred behind the limb and was observed over a wide spectral range. The analysis of optical, radio, and other relevant data suggest two phases of energy release. After an impulsive phase a prolonged post eruption energy release occurred in an extended region of the corona following the eruption of a large coronal mass ejection (CME). This phase is responsible for numerous coronal and interplanetary phenomena including the ground-level increase of cosmic rays.     

Effect of perturbed potentials on the non-linear stability of libration pointL 4 in the restricted problem

The non-linear stability of the libration pointL ₄ in the restricted problem has been studied when there are perturbations in the potentials between the bodies. It is seen that the pointL ₄ is stable for all mass ratios in the range of linear stability except for three mass ratios depending upon the perturbing functions. The theory is applied to the following four cases:

Evolution of helically twisted prominence structures of March 11, 1979

Helical structures are generally associated with many eruptive solar prominences. Thus, study of their evolution in the solar atmosphere assumes importance. We present a study of a flare-associated erupting prominence of March 11, 1979, with conspicuous helically twisted structure, observed in H line center. We have attempted to understand the role played by twisted force-free magnetic fields in this event. In the analysis, we have assumed that the helical structures visible in H outline the field lines in which prominence tubes are embedded. Untwisting of observed prominence tubes and later, formation of open prominence structures provide evidence of restructuring of the magnetic field configuration over the active region during the course of prominence eruption. Temporal evolution of the force-free parameter is obtained for two main prominence tubes observed to be intertwined in a rope-like structure. Axial electric currents associated with the prominence tubes are estimated to be of the order of 10¹¹ A which decreased with time. Correspondingly, it is estimated that the rate of energy release was 10²⁸ erg s^–1 during the prominence eruption.     

Refinement of the synthetic hydroxyapatite cell parameters

High-precision, computer-refined values of the cell parameters of calcium hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂, have been determined with an X-ray diffractometer, internally standardized by means of sodium chloride. The results obtained are as follows: a ₀=9.4192 Å c ₀/a ₀=0.731 c ₀=6.8867 Å volume=529.2 ų The apatite work was supported by a research grant DE-02105 from the United States Department of Health, Education, and Welfare. I am very grateful to Dr. W. R. Liebenberg, Dr. S. A. Hiemstra and Dr. H. V. R. von Rahden of National Institute for Metallurgy, South Africa for their valuable help and interest and Prof. Nelson Fuson and Prof. James R. Lawson for advice and discussion.     

Observations of sunspot umbral velocity oscillations

Sunspot umbral molecular lines have been used to look for the oscillatory velocities in the umbra. Power spectrum analysis showed conspicuous power for periods in the range between 448 and 310 s. The maximum peak-to-peak amplitude of the umbral oscillatory velocity component is observed to be in the order of 0.5 km s^–1.Visiting Astronomer, Solar Division, Kitt Peak National ObservatoryOperated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

The Non-Linear Stability of L4 in the Restricted Three-Body Problem when the Bigger Primary is a Triaxial Rigid Body

The non-linear stability of L ₄ in the restricted three-body problem has been studied when the bigger primary is a triaxial rigid body with its equatorial plane coincident with the plane of motion. It is found that L ₄ is stable in the range of linear stability except for three mass ratios:

Variation of solar irradiance and mode frequencies during Maunder minimum

Using the sunspot numbers reported during the Maunder minimum and the empirical relations between the mode frequencies and solar activity indices, the variations in the total solar irradiance and 10.7 cm radio flux for the period 1645 to 1715 is estimated. We find that the total solar irradiance and radio flux during the Maunder minimum decreased by 0.19% and 52% respectively, as compared to the values for solar cycle 22. This revised version was published online in July 2006 with corrections to the Cover Date.     

Existence and Stability of L4,5 In The Relativistic Restricted Three-Body Problem

The existence and stability of triangular libration points in the relativistic restricted three-body problem has been studied. It is found that L_4,5 are unstable in the whole range 0 ≤ μ ≤ 1/2 in contrast to the classical restricted three-body problem where they are stable for 0 < μ < μ₀, where μ is the mass parameter and μ₀ = 0.03852.... This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of perturbations in coriolis and centrifugal forces on the nonlinear stability of equilibrium points in the restricted problem of three bodies

Celestial Mechanics and Dynamical Astronomy - The non-linear stability of the equilibrium points in the restricted problem has been studied when small perturbations ε and ε′ are...     

The reduction of the solar velocity field into its oscillatory and slowly-varying components

Spectroheliogram movies of the solar velocity field have been made in the 4924 line of Feii with a time resolution of 20 sec/frame and a spatial resolution in the range 1–2 sec of arc. A conventional doppler movie has been used to generate two additional movies which show the slowly-varying and oscillatory components of the velocity field separately. A basic result is the simplicity of the field patterns into which the relatively complex velocity field can be decomposed.Operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation.Visiting Astronomer, Solar Division.