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Models of solar irradiance variations: Current status
Solanki, Sami K.; Krivova, Natalie A.
Regular monitoring of solar irradiance has been carried out since 1978 to show that solar total and spectral irradiance varies at different time scales. Whereas variations on time scales of minutes to hours are due to solar oscillations and granulation, variations on longer time scales are driven by the evolution of the solar surface magnetic fiel…
Next generation UV coronagraph instrumentation for solar cycle-24
Kohl, John L.; Cranmer, Steven R.; Raymond, John C. +4 more
Ultraviolet coronagraph observations of the extended solar corona (defined here as 1.5 to 10 solar radii from Sun-center) have become a powerful tool for obtaining detailed empirical descriptions of coronal holes, streamers, and coronal mass ejections. The empirical models resulting from ultraviolet coronagraph observations provide the constraints…
UV diagnostics for the energy budget of flares and CMEs
Raymond, J. C.
Solar flares and coronal mass ejections convert large amounts of magnetic free energy into thermal, kinetic and potential energies, and into energy of non-thermal particles. The partitioning among these forms of energy is fundamental to both the physics of the eruptive events and the space weather consequences of the eruptions. This talk describes…
Oblique Propagation and Dissipation of Alfv&én Waves in Coronal Holes
Srivastava, A. K.; Dwivedi, B. N.
We investigate the effect of viscosity and magnetic diffusivity on the oblique propagation and dissipation of Alfvén waves with respect to the normal outward direction, making use of MHD equations, density, temperature and magnetic field structure in coronal holes and underlying magnetic funnels. We find reduction in the damping length scale, grou…
The Mass/Eccentricity Limit in Double Star Astronomy
Dommanget, J.
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular parameterX, bound to the areal constant. This appeared to have a real physical significance b…
The EUV Spectrum of Sunspot Plumes Observed by SUMER on SOHO
Dwivedi, B. N.; Curdt, W.; Feldman, U.
We present results from sunspot observations obtained by SUMER on SOHO. In sunspot plumes the EUV spectrum differs from the quiet Sun; continua are observed with different slopes and intensities; emission lines from molecular hydrogen and many unidentified species indicate unique plasma conditions above sunspots. Sunspot plumes are sites of system…
Stellar sources in the isogal inner galactic bulge field (l=0°,b= ‑ 1°)
Ganesh, S.; Omont, A.; Schultheis, M. +2 more
ISOGAL is a survey at 7 and 15 µm with ISOCAM of the inner galactic disk and bulge of our Galaxy. The survey covers ∼ 22 deg2 in selected areas of the centrall = ±30 degree of the inner Galaxy. In this paper, we report the study of a small ISOGAL field in the inner galactic bulge (l = 0°,b = ‑1°, area = 0.033deg2). Usin…
Electron Density and Temperature Measurements, and Abundance Anomalies in the Solar Atmosphere
Landi, Enrico; Dwivedi, Bhola N.; Mohan, Anita
Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance anomalies in the solar atmosphere. In particular, we present the behaviour of the solar FIP effect …
Ulysses Observations of Nonlinear Wave-wave Interactions in the Source Regions of Type III Solar Radio Bursts
MacDowall, R. J.; Thejappa, G.
The Ulysses Unified Radio and Plasma Wave Experiment (URAP) has observed Langmuir, ion-acoustic and associated solar type III radio emissions in the interplanetary medium. Bursts of 50–300 Hz (in the spacecraft frame) electric field signals, corresponding to long-wavelength ion-acoustic waves are often observed coincident in time with the most int…
The Spectroscopic Orbit of 6-DRACONIS
Reimers, D.; Griffin, R. F.; Eitter, J. J.
6 Dra has long been known to show small variations in radial velocity, and there is photometric and spectroscopic evidence that its spectrum is composite. We show, largely on the basis of a generous number of photoelectric radial velocities mainly obtained at Cambridge and Fick observatories, that the orbit is of mild eccentricity and has a period…