Evolution of the Solar Flare Energetic Electrons in the Inhomogeneous Inner Heliosphere

Solar flare accelerated electrons escaping into the interplanetary space and seen as type III solar radio bursts are often detected near the Earth. Using numerical simulations we consider the evolution of energetic electron spectrum in the inner heliosphere and near the Earth. The role of Langmuir wave generation, heliospheric plasma density fluctuations, and expansion of magnetic field lines on the electron peak flux and fluence spectra is studied to predict the electron properties as could be observed by Solar Orbiter and Solar Probe Plus. Considering various energy loss mechanisms we show that the substantial part of the initial energetic electron energy is lost via wave–plasma processes due to plasma inhomogeneity. For the parameters adopted, the results show that the electron spectrum changes mostly at the distances before ～?20 R _⊙. Further into the heliosphere, the electron flux spectrum of electrons forms a broken power law relatively similar to what is observed at 1 AU.     

Coronal and Interplanetary Structures Associated with Type III Bursts

This paper pursues former studies of the coronal structures that are associated with radio type III bursts by taking advantage of the new capabilities of STEREO/SECCHI. The data analysis has been performed for 02 and 03 June 2007. During these two days several type III bursts, which were detected in the corona and in the interplanetary medium, occurred during the observing time of the Nançay radioheliograph. Electron beams accelerated in the same active region and producing type III emissions almost at the same time, can propagate in different well defined coronal structures below 15 R_⊙. Then, these structures become imbedded in the same plasma sheet which can be tracked up to 0.25 AU. Inhomogeneities travel along these structures; their velocities measured between 15 and 35 R_⊙ are typical of those of a slow solar wind. Comparison with PFSS magnetic field extrapolation shows that its connection with the IP magnetic field is different from what is suggested by the present observations. These results are consistent with those obtained in the IP medium formerly by Buttighoffer (Astron. Astrophys. 335, 295, 1998) who identified by in situ measurements at 1 AU and beyond, the sites where Langmuir waves, associated with local type III emissions, are excited.     

Reproducible characteristics of the solar wind acceleration

In experiments that were regularly carried out in 1999–2002 with Pushchino radio telescopes (Russian Academy of Sciences), the study of the radial dependence of the scattering of radio emission from compact natural sources was extended to regions of circumsolar plasma farther from the Sun. Based on a large body of data, we show that, apart from the standard transonic acceleration region located at distances of 10–40 R_⊙ from the Sun, there is a region of repeated acceleration at distances of 34–60 R_⊙ attributable to the equality between the solar wind velocity and the Alfvénic velocity. The repetition in the trans-Alfvénic region of the characteristic features of the radial stream structure observed in the transonic region (the existence of a precursor, a narrow region of reduced scattering that precedes a wide region of enhanced scattering) suggests that the main characteristic features of the resonant acceleration of solar wind streams are preserved up to distances of the order of 60 R_⊙.     

OSO-7 results on coronal emission near 304 Å

The spectral composition and spatial distribution of equatorial coronal emission near 304 Å is examined. Spectral scans indicate that the predominant line is from Si xi. Comparisons of observations with calculations of intensity changes with altitude indicate that collisional excitation is important near the Sun but that photoexcitation becomes dominant beyond about 1.3 R _⊙ from the solar center. Observed and calculated intensities are in approximate agreement for abundances and electron densities that are within the range of observed values.     

A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun’s Subsurface, Surface, Corona, and Sunspot Groups

Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985?–?2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94R_⊙,0.95R_⊙,…,1.0R_⊙ measured by the Global Oscillation Network Group (GONG) during the period 1995?–?2010, ii) the data on the soft-X-ray corona determined from Yohkoh/SXT full-disk images for the years 1992?–?2001, iii) the data on small bright coronal structures (SBCS) that were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998?–?2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986?–?2007. A large portion (up to ≈?30^° latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94R_⊙ and 0.98R_⊙. The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging behind that of the equatorial-rotation rate determined from the GONG measurements by one to two years. The amplitude of the GONG measurements is very small. The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data. The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (>?|3^°|?day^?1) of the sunspot groups. Implications of these results are pointed out.     

The Sub-surface Structure of a Large Sample of Active Regions

We employ ring-diagram analysis to study the sub-surface thermal structure of active regions. We present results using a large number of active regions over the course of Solar Cycle 23. We present both traditional inversions of ring-diagram frequency differences, with a total sample size of 264, and a statistical study using Principal Component Analysis. We confirm earlier results on smaller samples that sound speed and adiabatic index are changed below regions of strong magnetic field. We find that sound speed is decreased in the region between approximately r=0.99?R _⊙ and r=0.995?R _⊙ (depths of 3 Mm to 7 Mm) and increased in the region between r=0.97?R _⊙ and r=0.985?R _⊙ (depths of 11 Mm to 21 Mm). The adiabatic index [Γ₁] is enhanced in the same deeper layers where sound-speed enhancement is seen. A weak decrease in adiabatic index is seen in the shallower layers in many active regions. We find that the magnitudes of these perturbations depend on the strength of the surface magnetic field, but we find a great deal of scatter in this relation, implying that other factors may be relevant.     

A solar wind model with the power spectrum of Alfvénic fluctuations

A new solar wind model has been developed by including in the model the Alfvénic fluctuation power spectrum equation proposed by Tu et al. (1984). The basic assumptions of the model are as follows: (1) for heliocentric distances r > 10 R _⊙, the radial variation of the power spectrum of Alfvénic fluctuations is controlled by the spectrum equation (1), (2) for heliocentric distances r < 10 R _⊙, the radial variation of the fluctuation amplitude is determined by the Alfvén wave WKB solution, (3) no energy cascades from the low-frequency boundary of the Alfvénic fluctuation power spectrum into the fluctuation frequency range, and the energy which cascades from the high-energy boundary of the spectrum into the higher frequency range is transported to heat of the solar wind flow. Some solutions of this model which, on one hand, describe the major properties of the Alfvénic fluctuations and the high-speed flow observed by Helios in the space range between 0.3–1 AU and, on the other hand, are consistent with the observational constraints at the coronal base have been obtained under the following conditions: (1) the spectrum index of the fluctuations is near to -1 for almost the whole frequency range at 10 R _⊙, (2) the particle flux density at 1 AU is not greater than 3 × 10⁸ cm^?2 s^?1, (3) the solution is for spherically-symmetric flow geometry or the solution passes through the outermost of the three critical points of the rapidly diverging flow geometry with f _max = 7. Some solutions passing through the innermost critical point of the rapidly diverging flow geometry with f _max = 7 have been found, however, with too low pressure at the coronal base to compare with the observational constraints. Heat addition or other kind of momentum addition for r < 10 R _⊙ is required to modify this model to yield better agreement with observations. A cascade energy flux function which leads to Kolmogorov power law in the high-frequency range of Alfvénic fluctuations is presented in Appendix A. More detailed discussions about the characteristics, the boundary conditions and the solution of the spectrum equation (1) are given in Appendix B.     

On the radii of Ap and Am stars

The radii of several Ap and Am stars have been compared with those of the normal A stars of the Main Sequence. Though the brighter Ap stars have a little larger radii than the Main-Sequence stars, they may not be much different from those of the slightly evolved normal A stars. The Am stars have radii with which they appear to be merging with those of the cooler A stars of the Main Sequence. The Ap stars have radii predominantly in the range of 1.8 to 3.4R _⊙, while the Am stars are mainly concentrated between 1.8 and 2.2R _⊙.     

Close binary system GO Cyg

In this study, we present long term photometric variations of the close binary system GO Cyg. Modelling of the system shows that the primary is filling Roche lobe and the secondary of the system is almost filling its Roche lobe. The physical parameters of the system are M₁ = 3.0 ± 0.2M_⊙, M₂ = 1.3 ± 0.1M_⊙, R₁ = 2.50 ± 0.12R_⊙, R₂ = 1.75 ± 0.09R_⊙, L₁ = 64 ± 9L_⊙, L₂ = 4.9 ± 0.7L_⊙, and a = 5.5 ± 0.3R_⊙. Our results show that GO Cyg is the most massive system near contact binary (NCB). Analysis of times of the minima shows a sinusoidal variation with a period of 92.3 ± 0.5 yr due to a third body whose mass is less than 2.3M_⊙. Finally a period variation rate of −1.4 × 10⁻⁹ d/yr has been determined using all available light curves.     

Analysis of EUV limb-brightening observations from ATM

Limb-brightening curves for EUV resonance lines of O vi and Mg x have been constructed from spectroheliograms (5″ resolution) of quiet limb regions observed with the Harvard experiment on Skylab. The observations are interpreted with a simple model for the transition layer and the corona. A comparison of theoretical and observed limb-brightening curves indicates that the lower boundary of the corona, where T _e= 10⁶K, is at a height of about 8000 km in typical quiet areas. For 1.01 R _⊙?r1.25 R _⊙, the corona can be represented by a homogeneous model in hydrostatic equilibrium with a temperature of 10₆K for 1.01 R _⊙?r<1.1 R _⊙ and 1.1 × 10₆K for r?1.1 R _⊙. The model for the transition layer is inhomogeneous, with the temperature gradient a factor of 3 shallower in the network than in the intranetwork regions. It appears that spicules should be included in the model in order to account for the penetration into the corona of cool (T _e<10⁶K) EUV-emitting material to heights up to 20000 km above the limb.     

Frequency Fine Structures of Type III Bursts Due to Localized Medium-Scale Density Structures Along Paths of Type III Beams

Predictions from large-scale kinetic simulations are presented for the effects on coronal type III bursts of localized, medium-scale, enhanced density structures superposed on the coronal background along the paths of type III beams. The simulations show that these density structures can produce pronounced frequency fine structures in type III spectra. Flux intensifications and reductions of f _p and 2f _p emission relative to those for the unperturbed background corona occur at frequencies corresponding to the density structures, where f _p is the local electron plasma frequency. Frequency fine structures that are intense, slowly drifting, and narrowband, and thus resemble the characteristics of stria bursts, are predicted for the 2f _p emission. The 2f _p results are consistent with the qualitative proposal of Takakura and Yousef (Solar Phys. 40, 421, 1975) for the interpretation of stria/type IIIb bursts. However, the predicted f _p emission is much weaker than the 2f _p emission and generally below observable levels, and the predicted frequency fine structures do not always show stria characteristics. The predictions are thus inconsistent with the qualitative suggestion of Takakura and Yousef and the interpretations of many observers that stria bursts occur more often in f _p than in 2f _p emission. The significant discrepancies for f _p emission between our numerical calculations and the qualitative proposition of Takakura and Yousef (1975) are mainly caused by: i) differences in the detailed emission processes, ii) neglect of scattering of f _p emission off small-scale density fluctuations by Takakura and Yousef (1975), and iii) other simplifications made in both works. Possible improvements to the simulations are discussed, including improvements to the emission processes and the coronal and beam conditions (e.g., beam speed), in order to produce realistic stria/type IIIb bursts in f _p emission.     

A model for Type-IV emission in the solar burst of June 9, 1959 at decametric wavelengths

A major radio burst at decametric frequencies at 1638 UT on June 9, 1959 is apparently a Type-IV continuum burst of the kind that drifts from high to low frequencies. We present observations of flux variations and East-West positions of the emission at both 18 and 38 MHz. The burst moves outward at a speed of about 4700 km·sec^?1 at each frequency to a height of about 3 R _⊙ from the sun's center and then returns to the sun. This behavior is not simultaneous at 18 MHz and 38 MHz; the outward moving phase of 18 MHz emission occurs during the return phase of 38 MHz. We suspect that a solitary Alfvén wave or shock traverses the outer corona at the time of this burst. Relativistic electrons created low in the solar atmosphere travel freely along radial lines of force up to the coronal-streamer heights of the Type-IV burst. Upon encountering the shock, the electrons emit locally intense synchrotron emission, and pass through the shock on out into interplanetary space. This model appears to be consistent with other shock front phenomena in interplanetary space and the corona. Finally, the Razin effect (Boischot and Clavelier, 1967) suggests that low-frequency cut-offs in Type-IV bursts ought to be quite constant in frequency, and not higher than between 0.4 to 4 MHz.     

Gauribidanur Low-Frequency Solar Spectrograph

A new radio spectrograph, dedicated to observe the Sun, has been recently commissioned by the Indian Institute of Astrophysics (IIA) at the Gauribidanur Radio Observatory, about 100 km North of Bangalore. The instrument, called the Gauribidanur Low-frequency Solar Spectrograph (GLOSS), operates in the frequency range≈40?–?440 MHz. Radio emission in this frequency range originates close to the Sun, typically in the radial distance range r≈1.1?–?2.0 R_⊙. This article describes the characteristics of the GLOSS and the first results.     

Oscillations of coronal loops and second pulsations of solar radio emission

The dispersion properties of the sausage eigenmodes of oscillations in a thin magnetic flux tube are numerically analyzed in terms of ideal magnetohydrodynamics (MHD). The period of the modes accompanied by the emission of MHD waves into the surrounding medium, which leads to acoustic damping of oscillations, is determined by the radius of the tube, not by its length. The dissipation of the sausage oscillations in comparatively high (?0.7R _⊙) and tenuous (?6 × 10⁸ cm^?3) coronal loops is considered. Their Q factor has bound found to be determined by the acoustic damping mechanism. The ratio of the plasma densities outside and inside the loop and the characteristic height of the emission source have been estimated by assuming the quasi-periodic pulsations of meter-wavelength radio emission to be related to the sausage oscillations.     

Determination of coronal magnetic fields from 10 to 26R ⊙ using the density compression ratios of CME-driven shocks

Recently, the estimation of coronal magnetic field using new methods, such as standoff distance method or density compression ratio method has been reported. In the present work, we utilized the density compression ratio of CME-driven shocks for 10 events at 29 different locations in the upper solar corona (10–26R _⊙) and determined the coronal magnetic field for two different adiabatic indices (γ=4/3 and 5/3). In addition, radial dependence of shock parameters in the corona is studied. It is found that the magnetic field estimated in the above range agree with the general trend. In addition, we obtained a radial profile of magnetic field [B(R)=623R ^?1.4] in the entire upper corona (3–30R _⊙) by combining the magnetic field estimated by Kim et al. (Astrophys. J. 746:118, 2012) in the range 3–15R _⊙ and that estimated in the present study in the range (10–26R _⊙). The power-law indices are nearly in agreement with recent results of CME-driven shocks reported in the literature. The results are discussed with the comparison of newly reported coronal magnetic field values obtained by different techniques and found that the power-law relation closely follow the literature values.     

HBHA 4705-03: A new cataclysmic variable

Results of photometric and spectroscopic studies for the new eclipsing cataclysmic variable star HBHA 4705-03 with an orbital period of 0.1718 days are presented. Its spectrum exhibits hydrogen and helium emission lines. The Doppler maps constructed from hydrogen lines and the He II λ 4686 line show that the regions near the inner Lagrangian point are the main source of emission in these lines, while the maps constructed from He I lines suggest the presence of an accretion disk around the primary. The masses of the components (M _WD = 0.54 ± 0.10M _⊙ andM _RD = 0.45 ± 0.05 M _⊙) and the orbital inclination of the system (i = 71.8° ± 0.7°) have been determined from observational data using well-known relations for close binaries and cataclysmic variable stars.     

Spectrographic study of the eclipsing binary system SZ Camelopardalis

Thirteen high-dispersion spectrographs of the eclipsing binary star SZ Cam have been studied with a view of determining more accurate information on: (i) the spectral type and luminosity classifications, (ii) absolute parameters for the component stars, (iii) the stellar environment of SZ Cam. The main results in these categories are as follows: (i) O9.5 Vnk, (ii)m _g=19±2M _⊙,m _s=6.5±1M _⊙;r _g=9.7±3.6R _⊙,r _s=4.8±1.7R _⊙;T _e～30000 K,T _e～23000 K; (iii) there is a local concentration of absorbing material which may reach a density of 2M _⊙ pc^?3, and the distance of the star is found to be 600±150 pc. The determined overluminosity of the secondary star and the local concentration of absorbing material are two topics which provide the basis for a discussion section.     

Absolute parameters of eclipsing binaries in Southern Hemisphere sky – II: QY Tel

This paper presents the first analysis of spectroscopic and photometric observations of the neglected southern eclipsing binary star, QY Tel. Spectroscopic observations were carried out at the South African Astronomical Observatory in 2013. New radial velocity curves from this study and V light curves from the All Sky Automated Survey were solved simultaneously using modern light and radial velocity curve synthesis methods. The final model describes QY Tel as a detached binary star where both component stars fill at least half of their Roche limiting lobes. The masses and radii were found to be 1.32 (± 0.06) M_⊙, 1.74 (± 0.15) R_⊙ and 1.44 (± 0.09) M_⊙, 2.70 (± 0.16) R_⊙ for the primary and secondary components of the system, respectively. The distance to QY Tel was calculated as 365 (± 40) pc, taking into account interstellar extinction. The evolution case of QY Tel is also examined. Both components of the system are evolved main-sequence stars with an age of approximately 3.2  Gy, when compared to Geneva theoretical evolution models.     

First photometric study of the W UMa system GSC 1042-2191

We present new photometric observations covering eight minima times for the eclipsing binary GSC 1042-2191. The light curves in $\mathit{BVRI}$ colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M₁= 1.26 ± 0.06 M_⊙, M₂ = 0.18 ± 0.06 M_⊙, R₁ = 1.54 ± 0.20 R_⊙, R₂ = 0.69 ± 0.01 R_⊙, ${\mathit{L}}_1$ =3.30 ± 0.30 L_⊙ and ${\mathit{L}}_2$ = 0.59 ± 0.20 L_⊙) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M_⊙, this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left.     

Continuum spectrum of the star Θ1 Ori C

Published photoelectric measurements over a wide wavelength range (0.36–18 µm) are used to study the continuum spectrum of the star Θ¹ Ori C. The model that assumes the following three radiation sources is consistent with observations: (1) a zero-age main-sequence O7 star (object 1) of mass M ₁=20M _⊙, radius R ₁=7.4R _⊙, effective temperature T ₂=37 000 K, and absolute bolometric magnitude $M\mathop {bol}\limits^1 = - 7\mathop .\limits^m 7$ ; (2) object 2 with M ₂=15M _⊙, R ₂=16.2R _⊙, T ₂=4000 K, and $M\mathop {bol}\limits^2 = - 5\mathop .\limits^m 1$ ; and (3) object 3 with R ₃10 700 R _⊙, T ₃=190 K, and $M\mathop {bol}\limits^3 = - 0\mathop .\limits^m 6$ . The visual absorption toward the system is $A_V = 0\mathop .\limits^m 95$ and obeys a normal law. The nature of objects 2 and 3 has not been elucidated. It can only be assumed that object 2 is a companion of the primary star, its spectral type is K7, and it is in the stage of gravitational contraction. Object 3 can be a cocoon star and a member of the system, but can also be a dust envelope surrounding the system as a whole.