We discuss models for coronal abundance anomalies observed in the coronae of the sun and other late-type stars following a scenario first introduced by Schwadron, Fisk & Zurbuchen of the interaction of waves at loop footpoints with the partially neutral gas. Instead of considering wave heating of ions in this location, we explore the effects on the upper chromospheric plasma of the wave pondero...

We use two different models to study the evolution of the coronal magnetic field which results from a simple photospheric field evolution. The first, the Minimum Current Corona (MCC), is a self-consistent model for quasi-static evolution which yields an analytic expression approximating the net coronal currents and the free magnetic energy stored by them. For the second model calculation, the n...

We show, theoretically and via MHD simulations, how a short burst of reconnection localized in three dimensions on a one-dimensional current sheet creates a pair of reconnected flux tubes. We focus on the post-reconnection evolution of these flux tubes, studying their velocities and shapes. We find that slow-mode shocks propagate along these reconnected flux tubes, releasing magnetic energy as ...

Through reduction of a huge data set spanning 2010-2017, we compare mean global changes in temperature, emission measure (EM), and underlying photospheric magnetic field of the solar corona over most of the last activity cycle. The quiet coronal mean temperature rises from 1.4 to 1.8 MK, whereas EM increases by almost a factor of 50% from solar minimum to maximum. An increased high-temperature ...

A major problem in astrophysical plasma physics is to explain how the outer atmosphere, the corona, ofthe sun is heated to temperatures of millions of degrees Kelvin. It is accepted that the heating mechanism is magnetic, with the energy source being turbulent motions below the solar surface. Two classes of theory are proposed, according to the timescale of the driving motions in relation to th...

Recent observations with TRACE reveal that the time delay between the appearance of a cooling loop in different EUV temperature filters is proportional to the loop length, ∆t12 ∝ L. We model this cooling delay in terms of radiative loss and confirm this linear relationship theoretically. We derive an expression that can be used to constrain the coronal iron enhancement αFe = Acor Fe /A Ph Fe re...

We report on 3.6 cm VLA and VLBA observations of YZ CMi and AD Leo, two nearby dMe stars. We resolve YZ CMi and can fit a circular symmetrical gaussian component of FWHP of 0.98 ±0.2 mas, corresponding to an extent of the corona above the photosphere of 1.77 × 1010 ± 8.8 × 109 cm or 0.7 ±0.3 R? (R? refers to the photospheric radius). We obtain an estimate of the brightness temperature of 7.3 × ...

We have investigated the relationship between magnetic activity and coronal structures using soft X-ray data from the Yohkoh soft X-ray telescope and magnetic field data from the Kitt Peak Solar Observatory for the period of 1991–2001 and EUV data from the Solar and Heliospheric Observatory EUV Imaging Telescope for 1996–2001. The data are reduced to Carrington synoptic maps, which reveal two t...

Simulation of stellar atmospheres, such as that our own sun, is a common task in CGI for scientific visualization, movies and games. A fibrous volumetric texture visually dominant feature the solar corona---the plasma extends from surface into space. These coronal fibers can be modeled magnetic filaments whose shape governed by magnetohydrostatic equation. The provide Lagrangian curve represent...

We introduce two different generalizations of relative helicity which may be applied to a portion of the coronal volume. Such a quantity is generally referred to as the self-helicity of the field occupying the sub-volume. Each definition is a natural application of the traditional relative helicity but relative to a different reference field. One of the generalizations, which we term additive s...