scholarly journals Statistical analysis of earthward flow bursts in the inner plasma sheet during substorms

2009 ◽  
Vol 114 (A7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Y. D. Ma ◽  
J. B. Cao ◽  
R. Nakamura ◽  
T. L. Zhang ◽  
H. Reme ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Plasma Sheet ◽  
Earthward Flow

scholarly journals A statistical analysis of Pi2‐band waves in the plasma sheet and their relation to magnetospheric drivers

2015 ◽  
Vol 120 (8) ◽  
pp. 6167-6175 ◽  
Author(s):  
G. Q. Wang ◽  
Y. S. Ge ◽  
T. L. Zhang ◽  
R. Nakamura ◽  
M. Volwerk ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Plasma Sheet

MMS/Cluster joint measurements at the vicinity of the plasma sheet boundary layer

2020 ◽  
Author(s):  
Olivier Le Contel ◽  
Alessandro Retino ◽  
Alexandra Alexandrova ◽  
Thomas Chust ◽  
Konrad Steinvall ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Cold Plasma ◽  
Large Scale ◽  
Plasma Sheet Boundary Layer ◽  
Electrostatic Waves ◽  
Hot Plasma ◽  
Short Period ◽  
Generation Mechanisms ◽  
Earthward Flow

<p>On 28th of August 2018 at 5:30 UT, MMS and Cluster were located in the magnetotail at about 16 earth radii (RE). They both suddenly crossed plasma interfaces. Located in the post midnight sector, Cluster transitioned from a cold plasma sheet to a hot plasma sheet whereas MMS, located at 4 RE duskward of Cluster, transitioned from a similar cold plasma sheet to the lobe region via a very short period in a hot plasma sheet. At 05:50 UT MMS returned to a hot plasma sheet and detected a quasi-parallel earthward flow ~ 400 km/s and increased energetic ion and electron fluxes. We use measurements from both missions during this conjunction to describe the possible macroscale evolution of the magnetotail as well as some associated kinetic processes. In particular, we analyze fast and slow non linear electrostatic waves propagating tailward which are detected in the so called electron boundary layer as well as in the hot plasma sheet. We discuss their possible generation mechanisms and link with the large scale evolution of the magnetotail. Finally, we investigate possible effects related to the dawn-dusk asymmetry of the magnetotail.</p>

scholarly journals ISEE-3 observations of a viscously-driven plasma sheet: magnetosheath mass and/or momentum transfer?

2002 ◽  
Vol 20 (5) ◽  
pp. 619-628 ◽  
Author(s):  
R. T. Mist ◽  
C. J. Owen
Keyword(s):  
Statistical Analysis ◽  
Momentum Transfer ◽  
Boundary Layers ◽  
Plasma Sheet ◽  
Momentum Flux ◽  
Driving Mechanism ◽  
Plasma Convection ◽  
Helmholtz Instability ◽  
Slow Flows ◽  
Field Lines

Abstract. A statistical analysis of data from the ISEE-3 distant tail campaign is presented. We investigate the mechanism driving slow, tailward flows observed in the plasma sheet. The possibility that these slow flows are driven by mass and/or momentum transfer across the distant tail magnetopause is explored. We establish that 40% of these flows could be driven by the transfer of approximately 4% of the magnetosheath momentum flux into the magnetotail. Current understanding of the Kelvin-Helmholtz instability suggests that this figure is consistent with the amount of momentum flux transfer produced by this mechanism. We also consider the possibility that these flows are solely driven by transferring magnetosheath plasma across the magnetopause. We find that there is sufficient mass observed on these field lines for this to be the sole driving mechanism for only 27% of the observed slow flows.Key words. Magnetospheric physics (magnetotail boundary layers; plasma convection; plasma sheet)

scholarly journals Origin of some anisotropic tailward flows in the plasma sheet

2002 ◽  
Vol 20 (10) ◽  
pp. 1559-1575 ◽  
Author(s):  
J. A. Wanliss ◽  
R. D. Sydora ◽  
G. Rostoker ◽  
R. Rankin
Keyword(s):  
Plasma Sheet ◽  
Ion Beam ◽  
Particle Model ◽  
Ion Distributions ◽  
Central Plasma ◽  
Nonadiabatic Effects ◽  
Equatorial Current ◽  
Central Plasma Sheet ◽  
Velocity Moments ◽  
Earthward Flow

Abstract. We use a test particle model to explore anisotropy and fast flows in the central plasma sheet (CPS) that are a consequence of plasma sheet boundary layer (PSBL) ion beam dynamics. Ion distributions and flows (velocity moments) in the CPS and equatorial current sheet (CS) are compared and we find that mirroring of initially earthward beams from the PSBL, and their subsequent convection to the CS region, results in strong anisotropy throughout the CPS. At higher latitudes, velocity moments are field-aligned and feature earthward flow. Deeper in the CPS, velocity moments yield flows in the anti-earthward direction. There is no clear distinction between the PSBL and CPS, since velocity distributions with large streaming components occur throughout the model CPS, but in the CS region they are anisotropic and nongyrotropic. In the CS region velocity moments can feature anti-earthward cross field flows. These tailward flows (> 400 km/s) are observed in the CS region between X = - 20 to - 30 RE due to nonadiabatic effects. Model results suggest that fast tailward plasma flows can be obtained without necessarily appealing to magnetotail processes associated with dynamic geomagnetic activity.Key words. Magnetospheric physics (magnetospheric con-figuration and dynamics) – Space plasma physics (charge particle motion and acceleration; numerical simulation studies)

scholarly journals Longitudinal development of a substorm brightening arc

2009 ◽  
Vol 27 (5) ◽  
pp. 1935-1940 ◽  
Author(s):  
K. Shiokawa ◽  
A. Ieda ◽  
A. Nakajima ◽  
K. Sakaguchi ◽  
R. Nomura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
Substorm Onset ◽  
Pressure Increase ◽  
Longitudinal Development ◽  
Magnetic Latitude ◽  
Longitudinal Extension ◽  
Earthward Flow

Abstract. We present simultaneous THEMIS-ground observations of longitudinal (eastward) extension of a substorm initial-brightening arc at Gillam (magnetic latitude: 65.6°) at 08:13 UT on 10 January 2008. The speed of the eastward arc extension was ~2.7 km/s. The extension took place very close to the footprints of the longitudinally separated THEMIS E and D satellites at ~12 RE. The THEMIS satellites observed field dipolarization, weak earthward flow, and pressure increase, which propagated eastward from E to D at a speed of ~50 km/s. The THEMIS A satellite, located at 1.6 RE earthward of THEMIS E, observed fluctuating magnetic field during and after the dipolarization. The THEMIS E/D observations suggest that the longitudinal extension of the brightening arc at substorm onset is caused by earthward flow braking processes which produce field dipolarization and pressure increase propagating in longitude in the near-earth plasma sheet.

scholarly journals Plasma sheet fast flows and auroral dynamics during substorm: a case study

2002 ◽  
Vol 20 (3) ◽  
pp. 341-347 ◽  
Author(s):  
N. L. Borodkova ◽  
A. G. Yahnin ◽  
K. Liou ◽  
J.-A. Sauvaud ◽  
A. O. Fedorov ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Neutral Line ◽  
Filamentary Structure ◽  
Storms And Substorms ◽  
Flow Directions ◽  
Auroral Phenomena ◽  
Fast Flow ◽  
The Relationship ◽  
Earthward Flow

Abstract. Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL). It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region) is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs), described by Angelopolous et al. (1992). These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i) tailward/earthward flows were superimposed on a very strong duskward flow, and (ii) wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms)

scholarly journals Azimuthal flow bursts in the inner plasma sheet and possible connection with SAPS and plasma sheet earthward flow bursts

2015 ◽  
Vol 120 (6) ◽  
pp. 5009-5021 ◽  
Author(s):  
L. R. Lyons ◽  
Y. Nishimura ◽  
B. Gallardo‐Lacourt ◽  
M. J. Nicolls ◽  
S. Chen ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Earthward Flow

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Quantitative parallel EELS spectrum imaging developed as a new tool in AEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1202-1203
Author(s):  
Gianluigi Botton ◽  
Gilles L'espérance
Keyword(s):  
Statistical Analysis ◽  
Spatial Resolution ◽  
Personal Computer ◽  
Systematic Study ◽  
Present Author ◽  
Chemical Elements ◽  
Detection Limits ◽  
Research Groups ◽  
Quantitative Performance ◽  
Spectrum Imaging

As interest for parallel EELS spectrum imaging grows in laboratories equipped with commercial spectrometers, different approaches were used in recent years by a few research groups in the development of the technique of spectrum imaging as reported in the literature. Either by controlling, with a personal computer both the microsope and the spectrometer or using more powerful workstations interfaced to conventional multichannel analysers with commercially available programs to control the microscope and the spectrometer, spectrum images can now be obtained. Work on the limits of the technique, in terms of the quantitative performance was reported, however, by the present author where a systematic study of artifacts detection limits, statistical errors as a function of desired spatial resolution and range of chemical elements to be studied in a map was carried out The aim of the present paper is to show an application of quantitative parallel EELS spectrum imaging where statistical analysis is performed at each pixel and interpretation is carried out using criteria established from the statistical analysis and variations in composition are analyzed with the help of information retreived from t/γ maps so that artifacts are avoided.

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