scholarly journals Polar observations of transverse magnetic pulsations initiated at substorm onset in the high-latitude plasma sheet

2003 ◽  
Vol 108 (A7) ◽  
Author(s):  
P. K. Toivanen
Keyword(s):  
High Latitude ◽  
Plasma Sheet ◽  
Transverse Magnetic ◽  
Substorm Onset ◽  
Magnetic Pulsations

Relation of solar wind parameters to high-latitude magnetic pulsations

2006 ◽  
Vol 12 (1) ◽  
pp. 80-84
Author(s):  
S.N. Samsonov ◽  
◽  
I.Ya. Plotnikov ◽  
D.Y. Sibeck ◽  
Yu. Watermann ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Magnetic Pulsations ◽  
Solar Wind Parameters

scholarly journals <i>Letter to the Editor</i> Why do ultra-low-frequency MHD oscillations with a discrete spectrum exist in the magnetosphere?

2005 ◽  
Vol 23 (3) ◽  
pp. 1075-1079 ◽  
Author(s):  
A. S. Leonovich ◽  
V. A. Mazur
Keyword(s):  
Discrete Spectrum ◽  
Observational Data ◽  
High Latitude ◽  
Plasma Sheet ◽  
Low Frequency ◽  
Magnetosonic Wave ◽  
Letter To The Editor ◽  
Morning Sector ◽  
Good Agreement

Abstract. A new concept of the global magnetospheric resonator is suggested for fast magnetosonic waves in which the role of the resonator is played by the near-Earth part of the plasma sheet. It is shown that the magnetosonic wave is confined in this region of the magnetosphere within its boundaries. The representative value of the resonator's eigenfrequency estimated at f~1MHz is in good agreement with observational data of ultra-low-frequency MHD oscillations of the magnetosphere with a discrete spectrum (f~0.8, 1.3, 1.9, 2.6...MHz). The theory explains the ground-based localization of the oscillations observed in the midnight-morning sector of the high-latitude magnetosphere.

scholarly journals Solar wind control of plasma number density in the near-Earth plasma sheet: three-dimensional structure

2008 ◽  
Vol 26 (12) ◽  
pp. 4031-4049 ◽  
Author(s):  
D. Nagata ◽  
S. Machida ◽  
S. Ohtani ◽  
Y. Saito ◽  
T. Mukai
Keyword(s):  
Solar Wind ◽  
Density Dependence ◽  
High Latitude ◽  
Plasma Sheet ◽  
Strong Dependence ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Lower Latitude ◽  
Number Density ◽  
Three Dimensional Structure

Abstract. The plasma number density in the near-Earth plasma sheet depends on the solar wind number density and the north-south component of interplanetary magnetic field (IMF Bz) with time lag and duration of several hours. We examined the three-dimensional structure of such dependences by fitting observations of plasma sheet and solar wind to an empirical model equation. Analyses were conducted separately for northward and southward IMF conditions. Effects of solar wind speed and IMF orientation were also examined by further subdivision of the dataset. Based on obtained results, we discuss (i) the relative contribution of the ionosphere and solar wind to plasma sheet mass supply, (ii) the entry mechanisms for magnetosheath particles, and (iii) the plasma transport in the plasma sheet. We found that solar wind number density dependence is weaker and IMF Bz dependence is stronger for faster solar wind with southward IMF, which suggests the contribution of ionospheric particles. Further from the Earth, different interplanetary conditions result in different structures of solar wind dependence, which indicate different solar wind entry mechanisms: (1) southward IMF results in a strong dependence on solar wind number density in the flank high-latitude region, (2) slow solar wind with northward IMF leads to lower-latitude peaks of solar wind number density dependence in the flank region, (3) fast solar wind with northward IMF results in a strong dependence on solar wind number density at the down-tail dusk flank equator, and (4) solar wind number density dependence is stronger in the downstream of quasi-parallel bow shock. These features are attributable to (1) low-latitude dayside reconnection entry, (2) high-latitude dayside reconnection entry, (3) entry due to decay of Kelvin-Helmholtz vortices, and (4) diffusive entry mediated by kinetic Alfven waves, respectively. Effect of IMF Bz and its time lags show plasma sheet reconfiguration associated with enhanced convective transport under southward IMF. Duration of IMF Bz effect under northward IMF is interpreted in terms of turbulent diffusive transport.

scholarly journals Recirculation of plasma sheet particles into the high-latitude boundary layer

1998 ◽  
Vol 103 (A11) ◽  
pp. 26521-26532 ◽  
Author(s):  
D. C. Delcourt ◽  
J.-A. Sauvaud
Keyword(s):  
Boundary Layer ◽  
High Latitude ◽  
Plasma Sheet

A new particle population near the high-latitude plasma sheet

2001 ◽  
Vol 106 (A12) ◽  
pp. 29669-29682 ◽  
Author(s):  
M. Wilber ◽  
Q. Li ◽  
R. M. Winglee ◽  
G. K. Parks ◽  
M. McCarthy ◽  
...  
Keyword(s):  
High Latitude ◽  
Plasma Sheet ◽  
Particle Population

scholarly journals Statistical study of high-latitude plasma flow during magnetospheric substorms

2004 ◽  
Vol 22 (10) ◽  
pp. 3607-3624 ◽  
Author(s):  
G. Provan ◽  
M. Lester ◽  
S. B. Mende ◽  
S. E. Milan
Keyword(s):  
Plasma Flow ◽  
Growth Phase ◽  
High Latitude ◽  
Large Scale ◽  
Flow Region ◽  
Substorm Onset ◽  
Return Flow ◽  
Polar Cap ◽  
Magnetospheric Substorms ◽  
Superposed Epoch Analysis

Abstract. We have utilised the near-global imaging capabilities of the Northern Hemisphere SuperDARN radars, to perform a statistical superposed epoch analysis of high-latitude plasma flows during magnetospheric substorms. The study involved 67 substorms, identified using the IMAGE FUV space-borne auroral imager. A substorm co-ordinate system was developed, centred on the magnetic local time and magnetic latitude of substorm onset determined from the auroral images. The plasma flow vectors from all 67 intervals were combined, creating global statistical plasma flow patterns and backscatter occurrence statistics during the substorm growth and expansion phases. The commencement of the substorm growth phase was clearly observed in the radar data 18-20min before substorm onset, with an increase in the anti-sunward component of the plasma velocity flowing across dawn sector of the polar cap and a peak in the dawn-to-dusk transpolar voltage. Nightside backscatter moved to lower latitudes as the growth phase progressed. At substorm onset a flow suppression region was observed on the nightside, with fast flows surrounding the suppressed flow region. The dawn-to-dusk transpolar voltage increased from ~40kV just before substorm onset to ~75kV 12min after onset. The low-latitude return flow started to increase at substorm onset and continued to increase until 8min after onset. The velocity flowing across the polar-cap peaked 12-14min after onset. This increase in the flux of the polar cap and the excitation of large-scale plasma flow occurred even though the IMF Bz component was increasing (becoming less negative) during most of this time. This study is the first to statistically prove that nightside reconnection creates magnetic flux and excites high-latitude plasma flow in a similar way to dayside reconnection and that dayside and nightside reconnection, are two separate time-dependent processes.

scholarly journals Correlation between ground-based observations of substorm signatures and magnetotail dynamics

2005 ◽  
Vol 23 (3) ◽  
pp. 997-1011 ◽  
Author(s):  
E. Borälv ◽  
H. J. Opgenoorth ◽  
K. Kauristie ◽  
M. Lester ◽  
J.-M. Bosqued ◽  
...  
Keyword(s):  
Solar Wind ◽  
Event Study ◽  
Plasma Sheet ◽  
Sheet Thickness ◽  
Substorm Onset ◽  
Boundary Motion ◽  
Thickness Variations ◽  
Magnetotail Dynamics

Abstract. We present a substorm event study using the four Cluster spacecraft in combination with ground-based instruments, in order to perform simultaneous observations in the ionosphere and magnetotail. We show good correlation between substorm signatures on the ground and in the magnetotail, even though data from the northern-ground and southern-tail hemispheres are compared. During this event ground-based magnetometers show a substorm onset over Scandinavia in the pre-midnight sector. Within 1.5h the onset and three intensifications are apparent in the magnetograms. For all the substorm signatures seen on the ground, corresponding plasma sheet boundary motion is visible at Cluster, located at a downtail distance of 18.5 RE. As a result of the substorm onset and intensifications, Cluster moves in and out between the southern plasma sheet and lobe. Due to the lack of an apparent solar wind driver and the good correlation between substorm signatures on the ground, we conclude the substorm itself is the driver for these plasma sheet dynamics. We show that in the scales of Cluster inter-spacecraft distances (~0.5 RE) the inferred plasma sheet motion is often directed in both Ygsm- and Zgsm-directions, and discuss this finding in the context of previous studies of tail flapping and plasma sheet thickness variations.

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