scholarly journals Inner magnetospheric plasma pressure distribution and its local time asymmetry

2003 ◽  
Vol 30 (16) ◽  
Author(s):  
A. T. Y. Lui
Keyword(s):  
Pressure Distribution ◽  
Local Time ◽  
Plasma Pressure ◽  
Magnetospheric Plasma ◽  
Time Asymmetry

Local time asymmetry in the characteristics of Pc5 magnetic pulsations

1983 ◽  
Vol 31 (4) ◽  
pp. 459-471 ◽  
Author(s):  
Kiyohumi Yumoto ◽  
Takao Saito ◽  
Tohru Sakurai
Keyword(s):  
Local Time ◽  
Time Asymmetry ◽  
Magnetic Pulsations

scholarly journals The dayside magnetopause location during radial interplanetary magnetic field periods: Cluster observation and model comparison

2015 ◽  
Vol 33 (4) ◽  
pp. 437-448 ◽  
Author(s):  
T. Huang ◽  
H. Wang ◽  
J.-H. Shue ◽  
L. Cai ◽  
G. Pi
Keyword(s):  
Local Time ◽  
Model Comparison ◽  
Dynamic Pressure ◽  
Cone Angle ◽  
Observation Model ◽  
Time Asymmetry ◽  
Dayside Magnetopause ◽  
Previous Hypothesis ◽  
Time Variations ◽  
The Imf

Abstract. The present work has investigated the midlatitudinal magnetopause locations under radial interplanetary field (RIMF) conditions. Among 262 (256) earthward (sunward) RIMF events from years of 2001 to 2009, Cluster satellites have crossed the magnetopause 22(12) times, with 10 (7) events occurring at midlatitudes. The observed midlatitudinal magnetopause positions are compared with two empirical magnetopause models (Shue et al., 1998; Boardsen et al., 2000) (hereafter referred to as the Shue98 model and the Boardsen00 model). The observation–model differences exhibit local time asymmetry. For earthward RIMF cases, the Shue98 model underestimates the magnetopause positions in the postnoon sector, while it overestimates the magnetopause positions in the dawn and dusk sectors. The Boardsen00 model generally underestimates the magnetopause after 6 MLT (magnetic local time), with larger deviations in the postnoon sector as compared to those in the prenoon. For sunward RIMF cases, the selected events are mainly clustered around the dawn and dusk sectors. The comparison with the Shue98 model indicates contractions in the dawn and expansions in the dusk sector, while the comparison with Boardsen00 indicates general expansions, with larger expansions in the later local time sectors. The local time variations in the differences between observations and the Shue98 and the Boardsen00 models indicate that the real magnetopause could be asymmetrically shaped during radial IMF periods, which should be considered by magnetopause models. The observation–model differences in the magnetopause positions (Δ RMP) during RIMF periods correlate well with the solar wind dynamic pressure, with larger Δ RMP for larger Pd. The southern magnetopause expands further outward relative to the model prediction when the dipole tilt angle is more negative (local summer in the Southern Hemisphere). For earthward RIMF cases, the generally good correlations between Δ RMP and the IMF cone angle are consistent with the previous hypothesis (Dušík et al., 2010) that, with more radial IMF, the subsolar magnetopause will expand further outward, owever, this is not the case for the comparison with Boardsen00 during sunward IMF periods, as it shows less dependence on the IMF cone angle.

scholarly journals Thermospheric Neutral Winds as the Cause of Drift Shell Distortion in Earth’s Inner Radiation Belt

2021 ◽  
Vol 8 ◽  
Author(s):  
Solène Lejosne ◽  
Mariangel Fedrizzi ◽  
Naomi Maruyama ◽  
Richard S. Selesnick
Keyword(s):  
Electric Field ◽  
Local Time ◽  
Large Scale ◽  
Radiation Belt ◽  
Energetic Electron ◽  
Recent Analysis ◽  
Quiet Time ◽  
Time Asymmetry ◽  
Electron Intensity

Recent analysis of energetic electron measurements from the Magnetic Electron Ion Spectrometer instruments onboard the Van Allen Probes showed a local time variation of the equatorial electron intensity in the Earth’s inner radiation belt. The local time asymmetry was interpreted as evidence of drift shell distortion by a large-scale electric field. It was also demonstrated that the inclusion of a simple dawn-to-dusk electric field model improved the agreement between observations and theoretical expectations. Yet, exactly what drives this electric field was left unexplained. We combine in-situ field and particle observations, together with a physics-based coupled model, the Rice Convection Model (RCM) Coupled Thermosphere-Ionosphere-Plasmasphere-electrodynamics (CTIPe), to revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt. The study is based on the dawn-dusk difference in equatorial electron intensity measured at L = 1.30 during the first 60 days of the year 2014. Analysis of measured equatorial electron intensity in the 150–400 keV energy range, in-situ DC electric field measurements and wind dynamo modeling outputs provide consistent estimates of the order of 6–8 kV for the average dawn-to-dusk electric potential variation. This suggests that the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across Earth’s magnetic field lines - the quiet time ionospheric wind dynamo - are the main drivers of the drift shell distortion in the Earth’s inner radiation belt.

scholarly journals Controlling of merging electric field and IMF magnitude on storm-time changes in thermospheric mass density

2013 ◽  
Vol 31 (1) ◽  
pp. 15-30 ◽  
Author(s):  
Y. L. Zhou ◽  
S. Y. Ma ◽  
R. S. Liu ◽  
H. Luehr ◽  
E. Doornbos
Keyword(s):  
Local Time ◽  
Delay Time ◽  
Mass Density ◽  
Correlation Coefficients ◽  
Control Factor ◽  
Time Asymmetry ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Magnetic Field Magnitude ◽  
Time Changes

Abstract. The controls of merging electrical field, Em, and IMF (interplanetary magnetic field) magnitude, B, on the storm-time changes in upper thermospheric mass density are statistically investigated using GRACE accelerometer observations and the OMNI data of solar wind and IMF for 35 great storms during 2002–2006. It reveals the following: (1) The correlation coefficients between the air mass density changes and the parameters of Em and B are generally larger at lower latitudes than at higher latitudes, and larger in noon and midnight sectors than in dawn and dusk. (2) The most likely delay time (MLDT) of mass density changes in respect to Em is about 1.5 h (4.5 h) at high (low) latitudes, having no distinct local time dependence, while it is 6 h at middle latitudes in all the local time sectors except for noon, which is longer than at low latitudes. A similar fact of longer delay time at mid-latitude is also seen for B. The MLDTs for B at various latitudes are all local time dependent distinctly with shorter delay time in noon/midnight sector and larger in dawn/dusk. Despite of widely spread of the delay time, IMF B exhibits still larger correlation coefficients with mass density changes among the interplanetary parameters. (3) The linear control factor of B on the density changes increases for large B, in contrast to somewhat saturation trend for larger Em. (4) The influence of B and Em on the mass densities shows different behavior for different types of storms. The influence intensity of Em is much stronger for CIR-driven than for CME-driven storm, while it is not so distinct for B. On the local time asymmetry of the influence, both Em and B have largest influence at noon sector for CME-driven storms, while an obviously larger intensification of the influence is found in dawn/dusk sector during CIR storms, especially for parameter Em.

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