We present results from SEPPCoN (Survey of Ensemble Physical Properties of Cometary Nuclei), a survey of 100 Jupiter-family comets (JFCs) using the Spitzer Space Telescope for mid-infrared measurements of thermal emission and several ground-based telescopes for visible-wavelength measurements of reflected sunlight. Our sample represents about 30%

We present the thermal-magnetic relation in a simple, isolated sunspot deduced from the inversion of 1.56 μm spectropolarimetric data. Due to the high Zeeman sensitivity of the g = 3, Fe I 1.5648 μm line, we can study this relationship in the entire sunspot. An inversion technique based on response functions is used to derive various parameters

Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been

Understanding the complicated non-linear thermal and magnetodynamic processes observed to continuously reshape the solar atmosphere requires the use of three-dimensional computer simulations and numerical experimentation. In this paper, a number of results from the recent generation of 3D numerical models of magnetic flux emergence from the topmost

A three-wavelength sun-photometer was designed and built. The attenuation of direct solar light, at wavelengths of 0.38 micrometers , 0.50 micrometers and 1.00 micrometers were measured. Silicon photodiodes and interference filters of 10 nm FWHM were used. Aerosols were characterized by angstrom's turbidity formula in terms of coefficients (alpha)

A ring-diagram analysis technique has been applied to a region of the Sun of about 15 deg^2 area close to the disk center at dates chosen for several solar rotations in 1996: April 5, May 1, May 28, June 27, July 23, August 20, August 21, and September 18. The horizontal velocity flows inferred directly beneath the solar surface have thus been