Magnetic field draping at the low-latitude magnetopause

1991 ◽  
Vol 96 (A9) ◽  
pp. 15779-15787 ◽  
Author(s):  
R. L. Richard ◽  
W. Lotko
Keyword(s):  
Magnetic Field ◽  
Low Latitude

scholarly journals The Earth's passage of the April 11, 1997 coronal ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions

1999 ◽  
Vol 17 (10) ◽  
pp. 1245-1250 ◽  
Author(s):  
S. Lepidi ◽  
P. Francia ◽  
U. Villante ◽  
A. Meloni ◽  
A. J. Lazarus ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Field ◽  
Field Conditions ◽  
Mhd Waves ◽  
Low Latitude ◽  
Terra Nova Bay ◽  
Field Fluctuations ◽  
Terra Nova

Abstract. An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay) and a low latitude (L'Aquila, Italy) station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz) and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetosphere interactions)

scholarly journals LION: A dynamic computer model for the low-latitude ionosphere

2007 ◽  
Vol 25 (11) ◽  
pp. 2371-2392 ◽  
Author(s):  
J. A. Bittencourt ◽  
V. G. Pillat ◽  
P. R. Fagundes ◽  
Y. Sahai ◽  
A. A. Pimenta
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Computer Model ◽  
Transport Processes ◽  
Time Dependent ◽  
Low Latitude ◽  
Radiation Chemical ◽  
Neutral Winds ◽  
Plasma Drifts ◽  
Low Latitude Ionosphere

Abstract. A realistic fully time-dependent computer model, denominated LION (Low-latitude Ionospheric) model, that simulates the dynamic behavior of the low-latitude ionosphere is presented. The time evolution and spatial distribution of the ionospheric particle densities and velocities are computed by numerically solving the time-dependent, coupled, nonlinear system of continuity and momentum equations for the ions O+, O2+, NO+, N2+ and N+, taking into account photoionization of the atmospheric species by the solar extreme ultraviolet radiation, chemical and ionic production and loss reactions, and plasma transport processes, including the ionospheric effects of thermospheric neutral winds, plasma diffusion and electromagnetic E×B plasma drifts. The Earth's magnetic field is represented by a tilted centered magnetic dipole. This set of coupled nonlinear equations is solved along a given magnetic field line in a Lagrangian frame of reference moving vertically, in the magnetic meridian plane, with the electromagnetic E×B plasma drift velocity. The spatial and time distribution of the thermospheric neutral wind velocities and the pattern of the electromagnetic drifts are taken as known quantities, given through specified analytical or empirical models. The model simulation results are presented in the form of computer-generated color maps and reproduce the typical ionization distribution and time evolution normally observed in the low-latitude ionosphere, including details of the equatorial Appleton anomaly dynamics. The specific effects on the ionosphere due to changes in the thermospheric neutral winds and the electromagnetic plasma drifts can be investigated using different wind and drift models, including the important longitudinal effects associated with magnetic declination dependence and latitudinal separation between geographic and geomagnetic equators. The model runs in a normal personal computer (PC) and generates color maps illustrating the typical behavior of the low-latitude ionosphere for a given longitudinal region, for different seasons, geophysical conditions and solar activity, at each instant of time, showing the time evolution of the low-latitude ionosphere, between about 20° north and south of the magnetic equator. This paper presents a detailed description of the mathematical model and illustrative computer results.

Recent observations of the heliospheric magnetic field at Ulysses: Return to low latitude

2000 ◽  
Vol 26 (5) ◽  
pp. 823-832 ◽  
Author(s):  
E.J. Smith ◽  
A. Balogh ◽  
R.F. Forsyth ◽  
B.T. Tsurutani ◽  
R.P. Lepping
Keyword(s):  
Magnetic Field ◽  
Low Latitude ◽  
Heliospheric Magnetic Field

scholarly journals Region-1 field aligned currents in experiments on laser-produced plasma interacting with magnetic dipole

2010 ◽  
Vol 6 (S274) ◽  
pp. 40-43
Author(s):  
I. F. Shaikhislamov ◽  
Yu. P. Zakharov ◽  
V. G. Posukh ◽  
E. L. Boyarintsev ◽  
A. V. Melekhov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Solar Wind ◽  
Experimental Evidence ◽  
Magnetic Dipole ◽  
Present Report ◽  
Low Latitude ◽  
The Earth ◽  
Field Aligned Current ◽  
Low Latitude Boundary Layer

AbstractIn previous experiments by the authors a generation of intense field aligned current (FAC) system on Terrella poles was observed. In the present report a question of these currents origin in a low latitude boundary layer of magnetosphere is investigated. Experimental evidence of such a link was obtained by measurements of magnetic field generated by tangential sheared drag. Results suggest that compressional and Alfven waves are responsible for FAC generation. The study is most relevant to FAC generation in the Earth and Hermean magnetospheres following pressure jumps in Solar Wind.

scholarly journals Modification of conductivity due to acceleration of the ionospheric medium

2008 ◽  
Vol 26 (8) ◽  
pp. 2111-2130 ◽  
Author(s):  
V. V. Denisenko ◽  
H. K. Biernat ◽  
A. V. Mezentsev ◽  
V. A. Shaidurov ◽  
S. S. Zamay
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Electric Current ◽  
Magnetic Field Line ◽  
Conducting Layer ◽  
Low Latitude ◽  
Ionosphere Model ◽  
Zero Current ◽  
Night Side ◽  
Low Latitude Ionosphere

Abstract. A quantitative division of the ionosphere into dynamo and motor regions is performed on the base of empirical models of space distributions of ionospheric parameters. Pedersen and Hall conductivities are modified to represent an impact of acceleration of the medium because of Ampére's force. It is shown that the currents in the F2 layer are greatly reduced for processes of a few hours duration. This reduction is in particular important for the night-side low-latitude ionosphere. The International Reference Ionosphere model is used to analyze the effect quantitatively. This model gives a second high conducting layer in the night-side low-latitude ionosphere that reduces the electric field and equatorial electrojets, but intensifies night-side currents during the short-term events. These currents occupy regions which are much wider than those of equatorial electrojets. It is demonstrated that the parameter σd=σP+σHΣH/ΣP that involves the integral Pedersen and Hall conductances ΣP, ΣH ought to be used instead of the local Cowling conductivity σC in calculations of the electric current density in the equatorial ionosphere. We may note that Gurevich et al. (1976) derived a parameter similar to σd for more general conditions as those which we discuss in this paper; a more detailed description of this point is given in Sect. 6. Both, σd and σC, appear when a magnetic field line is near a nonconducting domain which means zero current through the boundary of this domain. The main difference between σd and σC is that σd definition includes the possibility for the electric current to flow along a magnetic field line in order to close all currents which go to this line from neighboring ones. The local Cowling conductivity σC corresponds to the current closure at each point of a magnetic field line. It is adequate only for a magnetic field line with constant local conductivity at the whole line when field-aligned currents do not exist because of symmetry, but σC=σd in this case. So, there is no reason to use the local Cowling conductivity while the Cowling conductance ΣC=ΣP+ΣH2/ΣP is a useful and well defined parameter.

scholarly journals Analysis of Geomagnetic Storms Using Wavelet Transforms

2017 ◽  
Vol 4 (1) ◽  
pp. 119 ◽  
Author(s):  
B. Adhikari ◽  
R. Khatiwada ◽  
N. P. Chapagain
Keyword(s):  
Magnetic Field ◽  
Wavelet Analysis ◽  
Interplanetary Magnetic Field ◽  
High Frequency ◽  
Wavelet Transforms ◽  
Geomagnetic Storms ◽  
Wavelet Coefficient ◽  
Low Latitude ◽  
Statistical Tool ◽  
Sheath Region

<p class="Default">Geomagnetic storms are recognized as a worldwide decrease of the horizontal component of the Earth’s magnetic field measured at middle- and low-latitude magnetometers. The variations in the geomagnetic field during geomagnetic storms can be reproduced by changes in the interplanetary magnetic field and the solar wind velocity. Wavelet analysis, a useful statistical tool for analyzing variability has been used for this study. Wavelet transforms seem to be suited to analyze short-lived high-frequency phenomena such as discontinuities (shocks) in signals and transient structures. Wavelet analysis employed in the present work helps to decompose the time series of scales of interplanetary magnetic field (IMF-Bz) into different scales. To identify geomagnetic storms, the equatorial index, SYM-H has been used. The increase of wavelet coefficient amplitudes of the IMF-Bz is well correlated with the arrival of the shock and sheath region</p><p><strong>Journal of Nepal Physical Society</strong><em><br /></em>Volume 4, Issue 1, February 2017: 119-124</p>

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