Space Physics

Sep 2, 2024 | academic.oup.com | Space Physics

Geological evidence on Mars suggests that the red planet once hosted a dense atmosphere that supported the existence of surface oceans (e.g. Carr & Waenke 1992; di Achille & Hynek 2010). However, as time has passed, much of the Martian atmosphere appears to have escaped to space (e.g. Lillis et al. 2015).

Mar 8, 2024 | academic.oup.com | Space Physics

Throughout the Rosetta mission, cold electrons ( 3 × 1027s−1). However, the cold population was identified at low outgassing (Q < 1026s−1), when the inner coma was not expected to be collisional. We examine cooling of electrons at a weakly outgassing comet, using a 3D collisional model of electrons at a comet. Electron paths are extended by trapping in an ambipolar electric field and by gyration around magnetic field lines.

Mar 5, 2024 | agupubs.onlinelibrary.wiley.com | Finnish Museum |Space Physics |Joonas Uusitalo |Kseniia Golubenko

1 Introduction The assumption of geographically coherent atmospheric 14C concentrations forms the basis for the radiocarbon dating method. Although this assumption is considered generally true, there is an ongoing discussion regarding the potential existence of zonal gradients or regional offsets in the measured concentrations. For example, the Northern/Southern Hemisphere 14C offset is well known (Hogg et al., 2002; McCormac et al., 1998).

Feb 2, 2024 | academic.oup.com | Space Physics

We examine dissipation and energy conversion in weakly collisional plasma turbulence, employing in situ observations from the Magnetospheric Multiscale (MMS) mission and kinetic Particle-in-Cell (PIC) simulations of proton-electron plasma. A previous result indicated the presence of viscous-like and resistive-like scaling of average energy conversion rates—analogous to scalings characteristic of collisional systems.

Dec 22, 2023 | academic.oup.com | Academia Sinica |Space Physics

We investigate the linear axisymmetric viscous overstability in dense planetary rings with typical values of the dynamical optical depth τ ≳ 0.5. We develop a granular flow model which accounts for the particulate nature of a planetary ring subjected to dissipative particle collisions. The model captures the dynamical evolution of the disc’s vertical thickness, temperature, and effects related to a finite volume filling factor of the ring fluid.