Listed are all scientific papers resulting from an ISSI activity written or co-authored by ISSI Team members, Working Group members, Workshop participants, visitors or staff members.
Remote brightening (RB) is compact brightening at footpoints of magnetic loops, which are remotely connecting to and confining an eruption in the solar atmosphere. Here, we report on observations of an RB resulting from an EUV jet with a speed of about 90 km s−1. The loops connecting the RB and the jet have an apparent length of about 59 Mm. Intriguingly, the RB exhibits at least two episodes of brightenings, as characterized by two peaks in its lightcurve.
We present the first X-ray polarization measurements of GX 339–4. IXPE observed this source twice during its 2023–2024 outburst, once in the soft-intermediate state and again during a soft state. The observation taken during the intermediate state shows a significant (4σ) polarization degree PX = 1.3% ± 0.3% and polarization angle θX = −74° ± 7° only in the 3–8 keV band.
Accurate atomic models for astrophysical plasma can be very complex, requiring thousands of states. However, for a variety of applications such as large-scale forward models of the Stokes parameters of a spectral line in the solar corona, it is necessary to build much reduced atomic models. We present two examples of such models, focused on the two near-infrared Fe xiii lines observed on the ground at 10 750 and 10 801 Å.
Anthropogenic greenhouse gas emissions significantly impact the middle and upper atmosphere. They cause cooling and thermal shrinking and affect the atmospheric structure. Atmospheric contraction results in changes in key atmospheric features, such as the stratopause height or the peak ionospheric electron density, and also results in reduced thermosphere density.
Tidal interactions play a key role in the dynamics and evolution of icy worlds. The intense tectonic activity of Europa and the eruption activity on Enceladus are clear examples of the manifestation of tidal deformation and associated dissipation. While tidal heating has long been recognized as a major driver in the activity of these icy worlds, the mechanism controlling how tidal forces deform the different internal layers and produce heat by tidal friction still remains poorly constrained.
In situ observations of the solar wind have shown that the electron velocity distribution function (VDF) consists of a quasi-Maxwellian core, comprising most of the electron population, and two sparser components: the halo, which are suprathermal and quasi-isotropic electrons, and an escaping beam population, the strahl.
Cool ($approx 10^4$ K), dense material permeates the hot ($approx 10^6$ K), tenuous solar corona in form of coronal condensations, for example prominences and coronal rain. As the solar atmosphere evolves, turbulence can drive mixing between the condensations and the surrounding corona, with the mixing layer exhibiting an enhancement in emission from intermediate temperature ($approx 10^5$ K) spectral lines, which is often attributed to turbulent heating within the mixing layer.
Metasomatism refers to the process during which a pre-existing rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluids which invade the protolith. It changes chemical compositions of minerals, promotes their dissolution and precipitation of new minerals.
We present the first numerical simulations of a thin accretion disk around a Reissner–Nordström (RN) naked singularity (NkS; a charged point mass). The gravity of the RN NkS is modeled with a pseudo-Newtonian potential that reproduces exactly the radial dependence of the RN Keplerian orbital frequency; in particular, orbital angular velocity vanishes at the zero gravity radius and has a maximum at 4/3 of that radius.
An instability criterion in the magnetohydrodynamics (MHD) with the open boundary of a magnetic field is proposed in this paper. We use a series of linear force-free extrapolation fields, in which the normal part of the magnetic field is fixed, to obtain the linear fitting coefficient called relative alpha by using the cojoined value of magnetic free energy and magnetic flux at the open boundary (EfΦ2) and the square of relative magnetic helicity ( HR2 ).
