Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
On The Dawn-Dusk Asymmetry Of The Kelvin-Helmholtz Instability Between 2007 And 2013, Z. W. Henry, K. Nykyri, T. W. Moore, A. P. Dimmock, X. Ma
On The Dawn-Dusk Asymmetry Of The Kelvin-Helmholtz Instability Between 2007 And 2013, Z. W. Henry, K. Nykyri, T. W. Moore, A. P. Dimmock, X. Ma
Publications
Using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS), a statistical study was performed to determine whether a dawn-dusk asymmetry exists in the occurrence rates of the Kelvin-Helmholtz (KH) instability during Parker-Spiral (PS) and Ortho-Parker-Spiral (OPS) orientations of the interplanetary magnetic field (IMF). It is determined from the data that there is a strong preference toward the dawn side during PS orientation, and although a preference to the dusk side during OPS is suggested, this requires further study for an unambiguous confirmation. The uncertainty in the OPS result is due to a low number of events …
Influence Of Velocity Fluctuations On The Kelvin-Helmholtz Instability And Its Associated Mass Transport, Katariina Nykyri, Xuanye Ma, Andrew Dimmock, Claire Foullon, Antonius Otto, Adnane Osmane
Influence Of Velocity Fluctuations On The Kelvin-Helmholtz Instability And Its Associated Mass Transport, Katariina Nykyri, Xuanye Ma, Andrew Dimmock, Claire Foullon, Antonius Otto, Adnane Osmane
Publications
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 …
Temperature Variations In The Dayside Magnetosheath And Their Dependence On Ion-Scale Magnetic Structures: Themis Statistics And Measurements By Mms, A. P. Dimmock, A. Osmane, T. I. Pulkkinen, K. Nykyri, E. Kilpua
Temperature Variations In The Dayside Magnetosheath And Their Dependence On Ion-Scale Magnetic Structures: Themis Statistics And Measurements By Mms, A. P. Dimmock, A. Osmane, T. I. Pulkkinen, K. Nykyri, E. Kilpua
Publications
The magnetosheath contains an array of waves, instabilities, and nonlinear magnetic structures which modify global plasma properties by means of various wave-particle interactions. The present work demonstrates that ion-scale magnetic field structures (∼0.2–0.5 Hz) observed in the dayside magnetosheath are statistically correlated to ion temperature changes on orders 10–20% of the background value. In addition, our statistical analysis implies that larger temperature changes are in equipartition to larger amplitude magnetic structures. This effect was more pronounced behind the quasi-parallel bow shock and during faster solar wind speeds. The study of two separate intervals suggests that this effect can result from …
The Dawn–Dusk Asymmetry Of Ion Density In The Dayside Magnetosheath And Its Annual Variability Measured By Themis, Andrew P. Dimmock, Tuija I. Pulkkinen, Adnane Osmane, Katariina Nykyri
The Dawn–Dusk Asymmetry Of Ion Density In The Dayside Magnetosheath And Its Annual Variability Measured By Themis, Andrew P. Dimmock, Tuija I. Pulkkinen, Adnane Osmane, Katariina Nykyri
Publications
The local and global plasma properties in the magnetosheath play a fundamental role in regulating solar wind–magnetosphere coupling processes. However, the magnetosheath is a complex region to characterise as it has been shown theoretically, observationally and through simulations that plasma properties are inhomogeneous, non-isotropic and asymmetric about the Sun-Earth line. To complicate matters, dawn–dusk asymmetries are sensitive to various changes in the upstream conditions on an array of timescales. The present paper focuses exclusively on dawn–dusk asymmetries, in particularly that of ion density. We present a statistical study using THEMIS data of the dawn–dusk asymmetry of ion density in the …
Solar Wind Energy Input To The Magnetosheath And At The Magnetopause, T. I. Pulkkinen, A. P. Dimmock, A. Osmane, K. Nykyri
Solar Wind Energy Input To The Magnetosheath And At The Magnetopause, T. I. Pulkkinen, A. P. Dimmock, A. Osmane, K. Nykyri
Publications
Using Time History of Events and Macroscale Interactions During Substorms observations, we show that the efficiency of the energy entry through the magnetopause as measured by the Poynting vector normal component depends on the combination of the solar wind speed and the southward component of the interplanetary magnetic field (IMF): Most efficient energy transfer occurs when the IMF BZ is only moderately negative, and the solar wind speed is high. This means that for the same level of solar wind driver parameters (electric field, epsilon, or other), different combinations of V and BZ will produce different driving at the magnetopause. …
A Statistical Study Of The Dawn-Dusk Asymmetry Of Ion Temperature Anistrophy And Mirror Mode Occurrence In The Terrestrial Dayside Magnetosheath Using Themis Data, A. P. Dimmock, A. Osmane, T. I. Pulkkinen, K. Nykyri
A Statistical Study Of The Dawn-Dusk Asymmetry Of Ion Temperature Anistrophy And Mirror Mode Occurrence In The Terrestrial Dayside Magnetosheath Using Themis Data, A. P. Dimmock, A. Osmane, T. I. Pulkkinen, K. Nykyri
Publications
We present a statistical study of ion temperature anisotropy and mirror mode activity in the Earth's dayside magnetosheath using 6 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations focusing on the quantification of dawn-dusk asymmetry as a function of upstream conditions and distance from the magnetopause. Our statistical data show a pronounced dusk favored asymmetry of T⊥/T∥ which drives a similar asymmetry of mirror mode activity. T⊥/T∥ decreases with increasing solar wind Alfvén Mach number, whereas mirror mode occurrence increases. In both cases, the relative asymmetry between the dawn and dusk flanks decrease with increasing …
A Statistical Study Into The Spatial Distribution And Dawn-Dusk Asymmetry Of Dayside Magnetosheath Ion Temperatures As A Function Of Upstream Solar Wind Conditions, A. P. Dimmock, K. Nykyri, H. Karimabadi, A. Osmane, T. I. Pulkkinen
A Statistical Study Into The Spatial Distribution And Dawn-Dusk Asymmetry Of Dayside Magnetosheath Ion Temperatures As A Function Of Upstream Solar Wind Conditions, A. P. Dimmock, K. Nykyri, H. Karimabadi, A. Osmane, T. I. Pulkkinen
Publications
The magnetosheath contains the shocked solar wind and behaves as a natural filter to the solar wind plasma before it reaches the magnetosphere. The redistribution of kinetic energy at the bow shock results in significant thermalization of the solar wind plasma, resulting in a magnetosheath temperature profile which is highly nonhomogeneous and nonisotropic and differs between the dawn and dusk flanks. The present study attempts to study the spatial distribution of magnetosheath ion temperature as a function of upstream solar wind conditions. We pay particular attention to the dawn/dusk asymmetry in which we attempt to quantify using experimental data collected …
A Statistical Study Of Magnetic Field Fluctuations In The Dayside Magnetosheath And Their Dependence On Upstream Solar Wind Conditions, A. P. Dimmock, K. Nykyri, T. I. Pulkkinen
A Statistical Study Of Magnetic Field Fluctuations In The Dayside Magnetosheath And Their Dependence On Upstream Solar Wind Conditions, A. P. Dimmock, K. Nykyri, T. I. Pulkkinen
Publications
The magnetosheath functions as a natural interface connecting the interplanetary and magnetospheric plasma. Since the magnetosheath houses the shocked solar wind, it is populated with abundant magnetic field turbulence which are generated both locally and externally. Although the steady state magnetosheath is to date relatively well understood, the same cannot be said of transient magnetic perturbations due to their kinetic nature and often complex and numerous generation mechanisms. The current manuscript presents a statistical study of magnetic field fluctuations in the dayside magnetosheath as a function of upstream solar wind conditions. We concentrate on the ambient higher-frequency fluctuations in the …
The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri
The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri
Publications
The magnetosheath operates as a natural filter between the solar wind and the magnetospheric plasma. As a result of this, the magnetosheath plays a crucial role in the plasma momentum and energy transport from the interplanetary medium into the magnetosphere. Statistical studies of the magnetosheath are difficult due to the dynamic nature of the terrestrial bow shock and the magnetopause. As a result of this, the spatial and temporal dependence of magnetosheath plasma properties under varying solar wind conditions is still not completely understood. We present a study of magnetosheath plasma properties using 5 years of THEMIS and OMNI data …
Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.
Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.
Publications
Previous works have emphasized the significant influence of the solar wind Alfvén Mach number (MA) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in the magnetosheath flow distribution and magnetopause shape as a function of solar wind MA and interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data in the magnetosheath during the period 2001–2010, using an appropriate spatial superposition procedure, to produce magnetosheath flow distributions as a function of location in themagnetosheath relative to the IMF and other parameters. The results demonstrate that enhanced flows in the magnetosheath are expected …