Influence of velocity fluctuations on the Kelvin-Helmholtz instability and its associated mass transport
Journal of Geophysical Research: Space Physics
American Geophysical Union (AGU) / Wiley
© 2017. American Geophysical Union. All Rights Reserved.
Reason for embargo
Kelvin-Helmholtz instability (KHI) and associated magnetic reconnection and diffusion processes provide plasma transport from solar wind into the magnetosphere. The efficiency of this transport depends on the magnetosheath and magnetospheric plasma and field properties at the vicinity of the magnetopause. Our recent statistical study using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft indicates that the amplitude of the magnetosheath velocity fluctuations perpendicular to the magnetopause can be substantial. We have performed a series of local macroscale 2.5-dimensional magnetohydrodynamic simulations of the KHI during strongly northward interplanetary magnetic field and with the initial plasma parameters typical to the dayside magnetopause by perturbing the initial equilibrium with time-dependent perpendicular velocity field fluctuations. The effect of the single-mode and multimode seed spectrums at different frequencies and amplitudes is studied. The plasma transport in Kelvin-Helmholtz vortices is quantified. The results show that when large-amplitude, low-frequency seed velocity fluctuations exist in the magnetosheath, the resulting KH waves grow faster, get larger in size, and can transport more plasma through magnetic boundary, resulting in diffusion coefficient of the order 109 m2/s. The relevance of these findings to the solar wind-magnetosphere coupling is discussed.
K.N. thanks T. I. Pulkkinen for supporting her visit to Aalto University, Finland, during K.N.'s sabbatical leave from ERAU. K.N. thanks A. Streltsov for comments and E. Kilpua for helpful editorial and literature suggestions, on early version of the manuscript. The initial code development work of K.N., performed during December 2013 to August 2014, was funded by the Academy of Finland through grant 267073/2013. A. Osmane and A. Dimmock were funded through 267073/2013A. Dimmock is also funded through the Academy of Finland grant 288472. Subsequent simulation work, testing of different boundary conditions and resolutions, plasma transport, and random phase analysis of K.N., was supported by the NSF GEM grant 1502774 and NASA grant NNX16AF89G. K.N. and C.F. acknowledge the support by the International Space Science Institute (ISSI) Team on Flow-Driven Instabilities of the Sun-Earth System.
This is the final version of the article. Available from AGU via the DOI in this record.
Published online 19 September 2017