Local time distribution of low and middle latitude ground magnetic disturbances at sawtooth injections of 18–19 April 2002

2005 ◽  
Vol 110 (A7) ◽  
Author(s):  
Kentarou Kitamura
Keyword(s):  
Local Time ◽  
Time Distribution ◽  
Middle Latitude ◽  
Ground Magnetic ◽  
Magnetic Disturbances

scholarly journals Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling

2004 ◽  
Vol 22 (10) ◽  
pp. 3537-3560 ◽  
Author(s):  
P. E. Sandholt ◽  
C. J. Farrugia ◽  
W. F. Denig
Keyword(s):  
Solar Wind ◽  
Local Time ◽  
High Latitude ◽  
Specific Activity ◽  
Moderate Intensity ◽  
Auroral Activity ◽  
Activity Intensity ◽  
Subsolar Point ◽  
Field Lines ◽  
Ground Magnetic

Abstract. In two case studies we elaborate on spatial and temporal structures of the dayside aurora within 08:00-16:00 magnetic local time (MLT) and discuss the relationship of this structure to solar wind-magnetosphere interconnection topology and the different stages of evolution of open field lines in the Dungey convection cycle. The detailed 2-D auroral morphology is obtained from continuous ground observations at Ny Ålesund (76° magnetic latitude (MLAT)), Svalbard during two days when the interplanetary magnetic field (IMF) is directed southeast (By>0; Bz<0). The auroral activity consists of the successive activations of the following forms: (i) latitudinally separated, sunward moving, arcs/bands of dayside boundary plasma sheet (BPS) origin, in the prenoon (08:00-11:00 MLT) and postnoon (12:00-16:00 MLT) sectors, within 70-75° MLAT, (ii) poleward moving auroral forms (PMAFs) emanating from the pre- and postnoon brightening events, and (iii) a specific activity appearing in the 07:00-10:00 MLT/75-80° MLAT during the prevailing IMF By>0 conditions. The pre- and postnoon activations are separated by a region of strongly attenuated auroral activity/intensity within the 11:00-12:00 MLT sector, often referred to as the midday gap aurora. The latter aurora is attributed to the presence of component reconnection at the subsolar magnetopause where the stagnant magnetosheath flow lead to field-aligned currents (FACs) which are of only moderate intensity. The much more active and intense aurorae in the prenoon (07:00-11:00 MLT) and postnoon (12:00-16:00 MLT) sectors originate in magnetopause reconnection events that are initiated well away from the subsolar point. The high-latitude auroral activity in the prenoon sector (feature iii) is found to be accompanied by a convection channel at the polar cap boundary. The associated ground magnetic deflection (DPY) is a Svalgaard-Mansurov effect. The convection channel is attributed to effective momentum transfer from the solar wind-magnetosphere dynamo in the high-latitude boundary layer (HBL), on the downstream side of the cusp.

scholarly journals The magnetic local time distribution of energetic electrons in the radiation belt region

2017 ◽  
Vol 122 (8) ◽  
pp. 8108-8123 ◽  
Author(s):  
Hayley J. Allison ◽  
Richard B. Horne ◽  
Sarah A. Glauert ◽  
Giulio Del Zanna
Keyword(s):  
Local Time ◽  
Time Distribution ◽  
Radiation Belt ◽  
Magnetic Local Time ◽  
Energetic Electrons

scholarly journals An encounter-based approach for restricted diffusion with a gradient drift

2021 ◽  
Author(s):  
Denis Grebenkov
Keyword(s):  
Local Time ◽  
Time Distribution ◽  
First Passage Time ◽  
Joint Probability ◽  
Passage Time ◽  
Restricted Diffusion ◽  
Distribution Boundary ◽  
External Forces ◽  
Gradient Drift ◽  
The Impact

Abstract We develop an encounter-based approach for describing restricted diffusion with a gradient drift towards a partially reactive boundary. For this purpose, we introduce an extension of the Dirichlet-to-Neumann operator and use its eigenbasis to derive a spectral decomposition for the full propagator, i.e., the joint probability density function for the particle position and its boundary local time. This is the central quantity that determines various characteristics of diffusion-influenced reactions such as conventional propagators, survival probability, first-passage time distribution, boundary local time distribution, and reaction rate. As an illustration, we investigate the impact of a constant drift onto the boundary local time for restricted diffusion on an interval. More generally, this approach accesses how external forces may influence the statistics of encounters of a diffusing particle with the reactive boundary.

scholarly journals The mechanism of mid-latitude Pi2 waves in the upper ionosphere as revealed by combined Doppler and magnetometer observations

2013 ◽  
Vol 31 (4) ◽  
pp. 689-695 ◽  
Author(s):  
V. A. Pilipenko ◽  
E. N. Fedorov ◽  
M. Teramoto ◽  
K. Yumoto
Keyword(s):  
Large Scale ◽  
Vertical Displacement ◽  
Alfven Wave ◽  
Doppler Velocity ◽  
Low Latitude ◽  
Radar Network ◽  
Compressional Mode ◽  
Ground Magnetic ◽  
Magnetic Disturbances ◽  
Upper Ionosphere

Abstract. The interpretation of simultaneous ionospheric Doppler sounding and ground magnetometer observations of low-latitude Pi2 waves is revised. We compare the theoretical estimates of the ionospheric Doppler velocity for the same amplitude of the ground magnetic disturbances produced by a large-scale compressional mode and an Alfvén mode. The plasma vertical displacement caused by the wave electric field is shown to be the dominating effect. Taking into account the correction of the previous paper, the observations of low-latitude Pi2 in the F layer ionosphere by Doppler sounding and SuperDARN (Super Dual Auroral Radar Network) radars give consistent results. We suggest that the Doppler response to Pi2 waves is produced by the Alfvén wave component, but not the fast-mode component, whereas the ground magnetic signal is composed from both Alfvén and fast magnetosonic modes.

scholarly journals Studies of medium scale travelling ionospheric disturbances using TIGER SuperDARN radar sea echo observations

2004 ◽  
Vol 22 (12) ◽  
pp. 4077-4088 ◽  
Author(s):  
L.-S. He ◽  
P. L. Dyson ◽  
M. L. Parkinson ◽  
W. Wan
Keyword(s):  
Local Time ◽  
Electric Fields ◽  
Early Morning ◽  
Propagation Direction ◽  
Ionospheric Disturbances ◽  
Medium Scale ◽  
Travelling Ionospheric Disturbances ◽  
Seasonal And Diurnal Variations ◽  
Northward Propagation ◽  
Magnetic Disturbances

Abstract. Seasonal and diurnal variations in the direction of propagation of medium-scale travelling ionospheric disturbances (MSTIDs) have been investigated by analyzing sea echo returns detected by the TIGER SuperDARN radar located in Tasmania (43.4° S, 147.2° E geographic; –54.6°Λ). A strong dependency on local time was found, as well as significant seasonal variations. Generally, the propagation direction has a northward (i.e. equatorward) component. In the early morning hours the direction of propagation is quite variable throughout the year. It then becomes predominantly northwest and changes to northeast around 09:00 LT. In late fall and winter it changes back to north/northwest around 15:00 LT. During the other seasons, northward propagation is very obvious near dawn and dusk, but no significant northward propagation is observed at noon. It is suggested that the variable propagation direction in the morning is related to irregular magnetic disturbances that occur at this local time. The changes in the MSTID propagation directions near dawn and dusk are generally consistent with changes in ionospheric electric fields occurring at these times and is consistent with dayside MSTIDs being generated by the Lorentz force. Key words. Ionosphere (ionospheric disturbances; wave propagation; ionospheric irregularities; signal processing)

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