Foreshock Compressive Structures as the Cause of Magnetosheath Jets

Show simple item record

dc.contributor Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta fi
dc.contributor University of Helsinki, Faculty of Science en
dc.contributor Helsingfors universitet, Matematisk-naturvetenskapliga fakulteten sv
dc.contributor.author Suni, Jonas
dc.date.issued 2021
dc.identifier.uri URN:NBN:fi:hulib-202105212324
dc.identifier.uri http://hdl.handle.net/10138/330169
dc.description.abstract Magnetosheath jets are a class of structures in the Earth's magnetosheath usually defined by an enhancement of the dynamic pressure of the plasma. Magnetosheath jets have been observed by several different spacecraft over the past few decades, but their origin and formation mechanism have remained unclear. The aim of this thesis is to use data from a global simulation to investigate the origin of magnetosheath jets. We defined two different kinds of structures, magnetosheath jets and foreshock compressive structures (FCS), and collected a database of individual jets and FCSs from 4 Vlasiator global hybrid-Vlasov simulation runs, all of which simulate only the ecliptic plane. We then conducted a statistical analysis of the properties of jets and FCSs, and their occurrence rates as a function of the definition of the FCS criterion. Jets were separated into two categories: jets that form in contact with FCSs (FCS-jets), and those that do not (non-FCS-jets). We found that up to 75% of magnetosheath jets form in association with an FCS impacting the Earth's bow shock. We also found that FCS-jets penetrate deeper into the magnetosheath than non-FCS-jets. Finally, we found no conclusive explanation for the formation of non-FCS-jets. The properties of both jets and FCSs agree qualitatively and to some extent quantitatively with spacecraft observations and other simulations in the literature. The formation of jets from FCSs impacting the bow shock is similar to the proposed theory that jets are linked to Short Large-Amplitude Magnetic Structures (SLAMS). In the future, we will study magnetosheath jets and FCSs in polar plane simulation runs as well, and ultimately in full 3D simulation runs. If made possible by new simulations, the effects of electron kinetic effects on jets and FCSs will also be studied. Comparison studies with spacecraft observations of jet formation from FCSs will also be conducted, if and when such observations are found and become available. en
dc.language.iso eng
dc.publisher Helsingin yliopisto fi
dc.publisher University of Helsinki en
dc.publisher Helsingfors universitet sv
dc.subject Space physics
dc.subject Foreshock
dc.subject Bow shock
dc.subject Magnetosheath
dc.subject Magnetosheath jets
dc.subject Vlasiator
dc.title Foreshock Compressive Structures as the Cause of Magnetosheath Jets en
dc.type.ontasot pro gradu -tutkielmat fi
dc.type.ontasot master's thesis en
dc.type.ontasot pro gradu-avhandlingar sv
dct.identifier.urn URN:NBN:fi:hulib-202105212324
dc.subject.specialization Astrofysikaaliset tieteet fi
dc.subject.specialization Astrophysical Sciences en
dc.subject.specialization De astrofysikaliska vetenskaperna sv
dc.subject.degreeprogram Alkeishiukkasfysiikan ja astrofysikaalisten tieteiden maisteriohjelma fi
dc.subject.degreeprogram Master's Programme in Particle physics and Astrophysical Sciences en
dc.subject.degreeprogram Magisterprogrammet i elementarpartikelfysik och astrofysikaliska vetenskaper sv

Files in this item

Total number of downloads: Loading...

Files Size Format View
Suni_Jonas_thesis_2021.pdf 2.617Mb PDF View/Open

This item appears in the following Collection(s)

Show simple item record