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Classifying Magnetosheath Jets Using MMS: Statistical Properties
Author(s) -
Raptis Savvas,
Karlsson Tomas,
Plaschke Ferdinand,
Kullen Anita,
Lindqvist PerArne
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja027754
Subject(s) - magnetosheath , physics , jet (fluid) , bow shock (aerodynamics) , perpendicular , astrophysics , computational physics , magnetohydrodynamics , plasma , shock (circulatory) , solar wind , mechanics , magnetopause , shock wave , geometry , nuclear physics , medicine , mathematics
Using Magnetospheric Multiscale (MMS) data, we find, classify, and analyze transient dynamic pressure enhancements in the magnetosheath (jets) from May 2015 to May 2019. A classification algorithm is presented, using in situ MMS data to classify jets ( N = 8 , 499 ) into different categories according to their associated angle between interplanetary magnetic field (IMF) and the bow shock normal vector ( θ B n ). Jets appearing for θ B n < 45 are referred to as quasi‐parallel, while jets appearing for θ B n > 45 as quasi‐perpendicular jets. Furthermore, we define those jets that occur at the boundaries between quasi‐parallel and quasi‐perpendicular magnetosheath as boundary jets. Finally, encapsulated jets are jet‐like structures with similar characteristics to quasi‐parallel jets while the surrounding plasma is of quasi‐perpendicular nature. We present the first statistical results of such a classification and provide comparative statistics for each class. Furthermore, we investigate correlations between jet quantities. Quasi‐parallel jets have the highest dynamic pressure while occurring more often than quasi‐perpendicular jets. The infrequent quasi‐perpendicular jets have a much smaller duration, velocity, and density and are therefore relatively weaker. We conclude that quasi‐parallel and boundary jets have similar properties and are unlikely to originate from different generation mechanisms. Regarding the encapsulated jets, we suggest that they are a special subset of quasi‐parallel jets originating from the flanks of the bow shock, for large IMF cone angles although a relation to flux transfer events (FTEs) and magnetospheric plasma is also possible. Our results support existing generation theories, such as the bow shock ripple and SLAMS‐associated mechanisms while indicating that other factors may contribute as well.