The turbulent foreshock region upstream of the quasi-parallel bow shock is dominated by waves and reflected particles that interact with each other and create a large number of different foreshock transients. The structures with the enhanced magnetic field (Short Large Amplitude Magnetic Structures, SLAMS) and density spikes named plasmoids are frequently observed. They are one of the suggested sources of transient flux enhancements (TFE) or jets in the magnetosheath. Using measurements of the Magnetospheric Multiscale Spacecraft (MMS) and OMNI solar wind database between the 2015 and 2018 years, we have found that there is a category of events exhibiting both magnetic field and density enhancements simultaneously and we introduce the term “mixed structures” for them. Consequently, we divided our set of observations into three groups of events and present their comparative statistical analysis in the subsolar foreshock. Based on our results and previous research, we discuss the properties, possible origin and occurrence rates these events under different upstream conditions and their possible relation to the jet and plasmoid formation in the magnetosheath.

The bow shock current (BSC) plays an important role in supplying the magnetosphere with solar wind energy, in particular during times of low solar wind magnetosonic Mach numbers. Since the magnetic pile-up in the magnetosheath has to be maintained, the BSC cannot close locally, but must instead connect to magnetospheric current systems. However, the details of this closure remain poorly understood. For east-west interplanetary magnetic field (IMF) it has been hypothesised that the BSC partly closes to the high-latitude ionosphere, as field-aligned currents (FACs) on open field lines, but there is still no statistical evidence of this. In order to investigate this hypothesis, we use nine years of Defence Meteorological Satellite Program (DMSP) data to construct normalised FAC maps of the northern hemisphere polar cap. We sort them according to different IMF clock angles, IMF magnitudes and magnetosonic Mach numbers. By separating opposite polarity FACs, we show that, on average, a unipolar FAC exists in the dayside polar cap when the IMF By ≠ 0, regardless of the sign of the IMF Bz. This current flows out of (into) the ionosphere in the northern hemisphere for IMF By > 0 (< 0) and is thus of the correct polarity to connect to the north-south component of the BSC. Moreover, it is strongest when the BSC flows predominantly in the north-south direction. These results constitute the first statistical evidence in support of at least a partial closure of the BSC to the ionosphere during non-zero IMF By.

Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from 0.1RE to 5.0RE (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on Graphics Processing Units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.

Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from 0.1 RE to 5.0 RE (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on Graphics Processing Units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.

Plasma structures with enhanced dynamic pressure, density or speed are often observed in Earth’s magnetosheath. We present a statistical study of these structures, known as jets and fast plasmoids, in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks. Using measurements from the four Magnetospheric Multiscale (MMS) spacecraft and OMNI solar wind data from 2015–2017, we present observations of jets during different upstream conditions and in the wide range distances from the bow shock. Jets observed downstream of the quasi-parallel bow shock are seen to propagate deeper and faster into the magnetosheath and on towards the magnetopause. We estimate the shape of the structures by treating the leading edge as a shock surface, and the result is that the jets are elongated in the direction of propagation but also that they expand more quickly in the perpendicular direction as they propagate through the magnetosheath.