The magnetopause is a magnetosphere boundary layer created through the dynamic pressure balance between the solar wind's kinetic pressure and Earth's magnetic field. The solar wind causes distortions in the magnetosphere's magnetic field topology supported by a current sheet first proposed by Chapman and Ferraro (1931), often termed the Chapman-Ferraro (CF) current, which runs in a dawn-to-dusk direction around the magnetopause (Ganushkina et al., 2018). This current structure is believed to be generated through pressure gradients at the magnetopause boundary layer where, as explained in Hasegawa (2012), the magnetosheath plasma has a higher plasma density, while the magnetosphere will have a higher ion temperature. The resulting changes in plasma density and temperature across the magnetopause lead to gradients that generate ion and electron diamagnetic currents running perpendicular to the magnetic field (Ganushkina et al., 2018).Because of the magnetopause's important role in magnetic reconnection and the resulting transfer of plasma and energy into the magnetosphere it has been the focus of numerous studies (
This article provides a concise review of the main physical structures and processes involved in space weather’s interconnected systems, emphasizing the critical roles played by magnetic topology and connectivity. The review covers solar drivers of space weather activity, the heliospheric environment, and the magnetospheric response, and is intended to address a growing cross-disciplinary audience interested in applied aspects of modern space weather research and forecasting. The review paper includes fundamental facts about the structure of space weather subsystems and special attention is paid to extreme space weather events associated with major solar flares, large coronal mass ejections, solar energetic particle events, and intense geomagnetic perturbations and their ionospheric footprints. This paper aims to be a first step towards understanding the magnetically connected space weather system for individuals new to the field of space weather who are interested in the basics of the space weather system and how it affects our daily lives.
The solar wind is a continuous outflow of charged particles from the Sun’s atmosphere into the solar system. At Earth, the solar wind’s outward pressure is balanced by the Earth’s magnetic field in a boundary layer known as the magnetopause. Plasma density and temperature differences across the boundary layer generate the Chapman-Ferraro current which supports the magnetopause. Along the dayside magnetopause, magnetic reconnection can occur in electron diffusion regions (EDRs) embedded into the larger ion diffusion regions (IDRs). These diffusion regions form when opposing magnetic field lines in the solar wind and Earth’s magnetic field merge, releasing magnetic energy into the surrounding plasma. While previous studies have given us a general understanding of the structure of these diffusion regions, we still do not have a good grasp of how they are statistically differentiated from the non-diffusion region magnetopause. By investigating 251 magnetopause crossings from NASA’s Magnetospheric Multiscale (MMS) Mission, we demonstrate that EDR magnetopause crossings show current densities an order of magnitude higher than non-EDR magnetopause crossings - crossings that either passed through the reconnection exhausts or through the non-reconnecting magnetopause. Significant current signatures parallel to the local magnetic field in EDR crossings are also identified, which is in contrast to the dominantly perpendicular current found in the non-EDR magnetopause. Additionally, we show that the ion velocity along the magnetopause is highly correlated with a crossing’s location, indicating the presence of magnetosheath flows inside the magnetopause current sheet.
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