Related papers: Analysis of the solar coronal green line profiles …

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1AU by examining…

Previous work utilising NASA's High-resolution Coronal Imager (Hi-C 2.1) 17.2 nm observations revealed that, even at the increased spatial scales available in the data-set, there may be evidence for coronal structures that are still not…

One of the most important objectives of solar physics is the physical understanding of the solar atmosphere, the structure of which is also described in terms of the density (N) and temperature (T) distributions of the atmospheric matter.…

Measurements of the temperature and density structure of the solar corona provide critical constraints on theories of coronal heating. Unfortunately, the complexity of the solar atmosphere, observational uncertainties, and the limitations…

Waves are thought to play a significant role in the heating of the solar atmosphere and the acceleration of the wind. Among the many types of waves observed in the Sun, the so-called p-modes with a 3 mHz frequency peak dominate the lower…

The million degree plasma of the solar corona must be supplied by the underlying layers of the atmosphere. The mechanism and location of energy release, and the precise source of coronal plasma, remain unresolved. In earlier work we pursued…

A new source in solar corona scattering photospheric and chromospheric Fraunhofer spectral lines is detected below a height of one solar radius above solar limb, consisting of tenuous and cool neutral atoms and much fewer once ionized ions.…

Determining accurate velocity measurements from observations of the Sun is of vital importance to solar physicists who are studying the wave dynamics in the solar atmosphere. Weak chromospheric absorption lines, due to dynamic events in the…

Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of…

The formation of the observed core-halo feature in the solar wind electron velocity distribution function is a long-time puzzle. In this letter based on the current knowledge of nanoflares we show that the nanoflare-accelerated electron…

This paper reviews the current state of our understanding of high-speed solar wind acceleration in coronal holes. Observations by SOHO, coupled with interplanetary particle measurements going back several decades, have put strong…

Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift…

Quasi-periodic disturbances have been observed in the outer solar atmosphere for many years now. Although first interpreted as upflows (Schrijver et al. (1999)), they have been widely regarded as slow magnetoacoustic waves, due to observed…

A forward model is described in which we synthesize spectra from an ab-initio 3D MHD simulation of an outer stellar atmosphere, where the coronal heating is based on braiding of magnetic flux due to photospheric footpoint motions. We…

During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject…

On 12 March 1996 we obtained observations of the quiet Sun with the SUMER instrument. The observa- tions were sequences of 15-20 second exposures of ultraviolet emission line profiles and of the neighboring continua. These data contain…

This review is split into two parts: one on chromospheric line formation in answer to the frequent question "where is my line formed", and one presenting state-of-the-art imagery of the chromosphere. In the first part I specifically treat…

Solar flare electron acceleration is an efficient process, but its properties (mechanism, location) are not well constrained. Via hard X-ray (HXR) emission, we routinely observe energetic electrons at the Sun, and sometimes we detect…

The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random…

Solar radio spikes are short duration and narrow bandwidth fine structures in dynamic spectra observed from GHz to tens of MHz range. Their very short duration and narrow frequency bandwidth are indicative of sub-second small-scale energy…