![]() ![]() While jets have been observed since 1998 ( Němeček et al., 1998), there are still several open questions regarding their origin, their morphology, and their exact generation mechanism ( Plaschke et al., 2018). ![]() When an enhancement higher than two times the background level is observed, a jet is registered to a list of events. In this work, we use the term “magnetosheath jet” or simply “jet” to describe an enhancement of the dynamic pressure above the background magnetosheath level, using a time-moving average window of ☑0 min for the dynamic pressure (e.g., Archer and Horbury, 2013 Gunell et al., 2014 Gutynska et al., 2015 Karlsson et al., 2015 Raptis et al., 2019). A phenomenon that is generated in the interaction of the solar wind with the bow shock is the so called “magnetosheath jet.” These jets are usually described as localized enhancements of dynamic pressure in the magnetosheath plasma and are attributed to a velocity or a density increase or in most cases an increase of both (e.g., Amata et al., 2011 Archer et al., 2012 Plaschke et al., 2018).įor magnetosheath jets, several terms and definitions are used in the literature ( Plaschke et al., 2018). This complexity arises mainly from the geometry of the bow shock and the rapid changes in the Interplanetary Magnetic Field (IMF). However, there are phenomena too complex to be precisely described by the current theoretical framework. The interaction between the solar wind and the Earth's bow shock can in principle be modeled through the Rankine–Hugoniot relations, assuming an 1D, time stationary shock ( Baumjohann and Treumann, 2012). Initially, the solar wind particles interact with the Earth's bow shock and are decelerated into subsonic velocities, moving into the magnetosheath region. The magnetosphere, surrounding the Earth, offers protection from plasma flows originating from the Sun traveling at supersonic speeds. As a result, even in the absence of certain upstream properties, such as the IMF direction, they are capable of accurately determining the jet class. The better performance of the neural networks likely is due to the fact that they use information from more solar wind quantities than the physics-based models. It is shown that neural networks are systematically outperforming the other methods by achieving a ~93% agreement with the initial dataset, while the rest of the methods achieve around 80%. To evaluate the results, a comparison with three physics-based modeling approaches is done. The initial database was compiled using MMS measurements in the magnetosheath (downstream) to identify and classify them as “quasi-parallel” or “quasi-perpendicular,” while the neural network uses only solar wind (upstream) measurements from the OMNIweb database. Using a pre-existing database of magnetosheath jets we train a neural network to distinguish between jets found downstream of a quasi-parallel bow shock ( θ B n 4 5 o). Magnetosheath jets are transient, localized dynamic pressure enhancements found downstream of the Earth's bow shock in the magnetosheath region. 2Space Applications & Research Consultancy (SPARC), Athens, Greece.1Division of Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden.Savvas Raptis 1 *, Sigiava Aminalragia-Giamini 2, Tomas Karlsson 1 and Martin Lindberg 1 ![]()
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