A primary characteristic of solar flares is the efficient acceleration of electrons to nonthermal deka-keV energies. While hard X-ray (HXR) observation of bremsstrahlung emission serves as the key diagnostic of these electrons. In this study, we investigate the time evolution of flare-accelerated electrons using the warm-target model.
The origin of Saturn’s rings is a long standing mystery in planetary science, for which the age of this system is a critical constraint. After having clarified what the age of the rings may mean, this article reviews several aspects of this question. We discuss the exposure age, which was recently found to be on the order a few 100 Myrs based on the rings’ composition and their bombardment rate by micrometeoroids.
It is common wisdom that collisionless shocks become non-planar and non-stationary at sufficiently high Mach numbers. Whatever the shock structure, the upstream and downstream fluxes of the mass, momentum and energy should be equal. At low Mach numbers, these conservation laws are satisfied when the shock front is planar and stationary. When this becomes impossible, inhomogeneity and time dependence, presumably in the form of rippling, develop.
Increasing interest in understanding the formation and dynamics of cool coronal condensations like solar prominences leads to complex magneto-hydrodynamical (MHD) simulations which assume a variety of physical processes responsible for energy balance. Formation of cool structures and their maintenance over the observed periods requires detailed treatment of heating/cooling processes of which the radiative ones are critically important.
Type III radio bursts are signatures of the fluxes of near-relativistic electrons ejected during solar flares. These bursts are frequently observed by spacecraft such as the Parker Solar Probe. It has been traditionally believed that these electron beams generate Langmuir waves through the two-stream instability, which are then converted into electromagnetic waves.
It is believed that the global atmospheric electrical circuit (GEC) could provide a possible link between the space environment and terrestrial weather. The electric charge from electrified clouds is uniformly distributed on the highly conductive, compared to the air below, ionospheric shell.
In a self-similar paradigm of structure formation, the thermal pressure of the hot intra-cluster gas follows a universal distribution, once the profile of each cluster is normalised based on the proper mass and redshift dependencies. The reconstruction of such a universal pressure profile requires an individual estimate of the mass of each cluster.
As the Sun moves through the local interstellar medium (LISM), it emits charged particles, creating the heliosphere occupied by the plasma of solar origin. Determining the structure of the heliosphere is a fundamental question that can be answered only by numerical simulations based on sophisticated theoretical models.
The fluid behavior of the solar wind is affected by the heat flux carried by the suprathermal electron populations, especially the electron strahl (or beam) that propagates along the magnetic field. In turn, the electron strahl cannot be stable, and in the absence of collisions, its properties are regulated mainly by self-generated instabilities.
Mars Express (MEX) is one of the most productive planetary missions of the European Space Agency (ESA). This low cost (∼150 M€) mission has been instrumental in shaping the planetary community in Europe and has contributed to paving the way for many subsequent ESA endeavours. During more than two decades, Mars Express has collected a wealth of data in all disciplines of Martian science.