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Full-Text Articles in Physical Sciences and Mathematics
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 …
Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore
Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore
Publications
We have estimated the ionospheric location, area, and travel time of quasi-periodic oscillations originating from the magnetospheric flanks. This was accomplished by utilizing global and local MHD models and Tsyganenko semi-empirical magnetic field model on multiple published and four new cases believed to be caused by the Kelvin– Helmholtz Instability. Finally, we used auroral, magnetometer, and radar instruments to observe the ionospheric signatures. The ionospheric magnetic latitude determined using global MHD and Tsyganenko models ranged from 58.3–80.2 degrees in the Northern Hemisphere and −59.6 degrees to −83.4 degrees in the Southern Hemisphere. The ionospheric magnetic local time ranged between 5.0–13.8 …
3-D Mesoscale Mhd Simulations Of Magnetospheric Cusp-Like Configurations: Cusp Diamagnetic Cavities And Boundary Structure, E. Adamson, A. Otto, K. Nykyri
3-D Mesoscale Mhd Simulations Of Magnetospheric Cusp-Like Configurations: Cusp Diamagnetic Cavities And Boundary Structure, E. Adamson, A. Otto, K. Nykyri
Publications
We present results from mesoscale simulations of the magnetospheric cusp region for both strongly northward and strongly southward interplanetary magnetic field (IMF). Simulation results indicate an extended region of depressed magnetic field and strongly enhanced plasma B which exhibits a strong dependence on IMF orientation. These structures correspond to the Cusp Diamagnetic Cavities (CDC’s). The typical features of these CDC’s are generally well reproduced by the simulation. The inner boundaries between the CDC and the magnetosphere are gradual transitions which form a clear funnel shape, regardless of IMF orientation. The outer CDC/magnetosheath boundary exhibits a clear indentation in both the …
3-D Mesoscale Mhd Simulations Of A Cusp-Like Magnetic Configuration: Method And First Results, E. Adamson, A. Otto, K. Nykyri
3-D Mesoscale Mhd Simulations Of A Cusp-Like Magnetic Configuration: Method And First Results, E. Adamson, A. Otto, K. Nykyri
Publications
We present a local mesoscale model of the magnetospheric cusp region with high resolution (up to 300 km). We discuss the construction and implementation of the initial configuration and give a detailed description of the numerical simulation. An overview of simulation results for the case of strongly northward interplanetary magnetic field (IMF) is then presented and compared with data from Cluster 2 spacecraft from 14 February 2003. Results show a cusp diamagnetic cavity (CDC) with depth normal to the magnetospheric boundary on the order of 1–2Re and a much larger extent of ~5–9Re tangential to the boundary, bounded by a …
Cluster Observations Of Reconnection Due To The Kelvin-Helmholtz Instability At The Dawnside Magnetospheric Flank, K. Nykyri, A. Otto, B. Lavraud, C. Mouikis, L. M. Kistler, A. Balogh, H. Rème
Cluster Observations Of Reconnection Due To The Kelvin-Helmholtz Instability At The Dawnside Magnetospheric Flank, K. Nykyri, A. Otto, B. Lavraud, C. Mouikis, L. M. Kistler, A. Balogh, H. Rème
Publications
On 3 July 2001, the four Cluster satellites traversed along the dawnside magnetospheric flank and observed large variations in all plasma parameters. The estimated magnetopause boundary normals were oscillating in the z-direction and the normal component of the magnetic field showed systematic ~2–3 min bipolar variations for 1 h when the IMF had a small positive bz-component and a Parker-spiral orientation in the x, y-plane. Brief ~33 s intervals with excellent deHoffman Teller frames were observed satisfying the Wal´en relation. Detailed comparisons with 2- D MHD simulations indicate that Cluster encountered rotational discontinuities generated by Kelvin-Helmholtz instability. We estimate a …
Origin Of The Turbulent Spectra In The High-Altitude Cusp: Cluster Spacecraft Observations, K. Nykyri, B. Grison, P. J. Cargill, B. Lavraud, E. Lucek, I. Dandouras, A. Balogh, N. Cornilleau-Wehrlin, H. Reme
Origin Of The Turbulent Spectra In The High-Altitude Cusp: Cluster Spacecraft Observations, K. Nykyri, B. Grison, P. J. Cargill, B. Lavraud, E. Lucek, I. Dandouras, A. Balogh, N. Cornilleau-Wehrlin, H. Reme
Publications
High-resolution magnetic field data from Cluster Flux GateMagnetometer (FGM) and the Spatio-Temporal Analysis of Field Fluctuations (STAFF) instruments are used to study turbulent magnetic field fluctuations during the highaltitude cusp crossing on 17 March 2001. Despite the quiet solar wind conditions, the cusp was filled with magnetic field turbulence whose power correlates with the field-aligned ion plasma flux. The magnetic field wave spectra shows power law behavior with both double and single slopes with break in the spectra usually occurring in the vicinity of the local ion cyclotron frequency. Strong peaks in the wave power close to local ion cyclotron …
Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al.
Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al.
Publications
The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs) seen both at Cluster and TC-1, which appear to lie north and …
Cluster Observations Of Magnetic Field Fluctuations In The High-Altitude Cusp, K. Nykyri, P. J. Cargill, E. Lucek, T. Horbury, B. Lavraud, A. Balogh, M. W. Dunlop, Et Al.
Cluster Observations Of Magnetic Field Fluctuations In The High-Altitude Cusp, K. Nykyri, P. J. Cargill, E. Lucek, T. Horbury, B. Lavraud, A. Balogh, M. W. Dunlop, Et Al.
Publications
High-resolution (22 vector/s) magnetic field data from Cluster FGM instrument are presented for the highaltitude cusp crossing on 17 March 2001. Despite the quiet solar wind conditions, the cusp was filled with magnetic field turbulence for much of the crossing. Large-scale fluctuations show some correlation between spacecraft but the higher frequency fluctuations show no correlation, indicating that the length scales of these waves are smaller than the spacecraft separation (500 km). In many intervals, there are clear peaks in the wave power around the ion cyclotron frequency (~1 Hz), and there is some evidence for waves at the first harmonic …
Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras
Cluster Encounters With The High Altitude Cusp: Boundary Structure And Magnetic Field Depletions, P. J. Cargill, M. W. Dunlop, B. Lavraud, R. C. Elphic, D. L. Holland, K. Nykyri, A. Balogh, I. Dandouras
Publications
Data from the four spacecraft Cluster mission during a high altitude cusp crossing on 13 February 2001 are presented. The spacecraft configuration has one leading spacecraft, with the three trailing spacecraft lying in a plane that corresponds roughly to the nominal magnetopause surface. The typical spacecraft separation is approximately 600 km. The encounter occurs under conditions of strong and steady southward Interplanetary Magnetic Field (IMF). The cusp is identified as a seven-minute long depression in the magnetic field, associated with ion heating and a high abundance of He+. Cusp entry involves passage through a magnetopause boundary that has undergone very …
Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto
Influence Of The Hall Term On Kh Instability And Reconnection Inside Kh Vortices, K. Nykyri, A. Otto
Publications
The Kelvin-Helmholtz instability (KHI) in its nonlinear stage can develop small-scale filamentary field and current structures at the flank boundaries of the magnetosphere. It has been shown previously with MHD simulations that magnetic reconnection can occur inside these narrow current layers, resulting in plasma transport from the solar wind into the magnetosphere. During periods of northward IMF, this transport is sufficient to generate a cold, dense plasma sheet on time scales consistent with satellite observations. However, when the length scales of these narrow current layers approach the ion inertia scale, the MHD approximation is not valid anymore and the Hall …