Related papers: The Solar X-ray Corona
The high-speed solar wind is typically the simplest and least stochastic type of large-scale plasma flow in the heliosphere. For much of the solar cycle, it is connected magnetically to large polar coronal holes on the Sun's surface.…
Identifying the two physical mechanisms behind the production and sustenance of the quiescent solar corona and solar wind poses two of the outstanding problems in solar physics today. We present analysis of spectroscopic observations from…
It is shown that the description of the solar cycle that takes into account the odd zonal harmonic of the solar magnetic field allows us to deepen our knowledge of two important aspects of the solar activity. First, to clarify and expand…
Young stars show a variety of highly energetic phenomena, from accretion and outflow processes to hot coronal plasmas confined in their outer atmosphere, all regulated by the intense stellar magnetic fields. Many aspects on each of these…
The solar coronal heating problem refers to the question why the temperature of the Sun's corona is more than two orders of magnitude higher than that of its surface. Almost 70 years after the discovery, this puzzle is still one of the…
The Sun's corona, heated to temperatures exceeding one million Kelvin despite lying above the cooler photosphere, has puzzled astrophysicists since its discovery in the 1940s. Prevailing theories, based on acoustic and magnetohydrodynamic…
We report on the results of the Sun in Time multi-wavelength program (X-rays to the UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and…
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…
The heating of coronal loops is investigated to understand the observational consequences in terms of the thermodynamics and radiative losses from the Sun as well as the magnetized coronae of stars with an outer convective envelope. The…
The middle corona, the region roughly spanning heliocentric altitudes from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere.…
Hinode observations have provided a new view of outflows from the Sun. These have been focussed in particular on flows emanating from the edges of active regions. These flows are long lasting and seem to exist to some extent in every active…
The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible e.g. in…
Observations indicate that magnetic fields in rapidly rotating stars are very strong, on both small and large scales. What is the nature of the resulting corona? Here we seek to shed some light on this question. We use the results of an…
Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the…
Within the quiet Sun corona imaged at 1 MK, much of the field of view consists of diffuse emission that appears to lack the spatial structuring that is so evident in coronal loops or bright points. We seek to determine if these diffuse…
We study extreme-ultraviolet emission line spectra derived from three-dimensional magnetohydrodynamic models of structures in the corona. In order to investigate the effects of increased magnetic activity at photospheric levels in a…
Many questions have to be answered before understanding the relationship between the emerging magnetic flux through the solar surface and the extreme geoeffective events. Which threshold determines the onset of the eruption? What is the…
Magnetic fields in the solar corona are responsible for a wide range of phenomena. However, any direct measurements of the coronal magnetic fields are very difficult due to lack of suitable spectral lines, weak magnetic fields, and high…
Coronal loops generally trace magnetic lines of force in the upper solar atmosphere. Understanding the loop morphology and its temporal evolution has implications for coronal heating models that rely on plasma heating due to reconnection at…
The magnetic fields and dynamical processes in the solar polar regions play a crucial role in the solar magnetic cycle and in supplying mass and energy to the fast solar wind, ultimately being vital in controlling solar activities and…