Influence of the curvature of geomagnetic field lines on the trapping criterion for Low-Frequency electromagnetic waves entrapped into wave ducts with increased electron density in the Earth’s magnetosphere

2008 ◽  
Vol 53 (5) ◽  
pp. 529-534 ◽  
Author(s):  
A. V. Moshkov
Keyword(s):  
Electron Density ◽  
Geomagnetic Field ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Earth’S Magnetosphere ◽  
Earth's Magnetosphere ◽  
Field Lines

Microinstabilities excited by energetic ring current protons

2003 ◽  
Vol 69 (5) ◽  
pp. 383-395
Author(s):  
S. MOOLLA ◽  
R. BHARUTHRAM
Keyword(s):  
Electromagnetic Waves ◽  
Ring Current ◽  
Low Frequency ◽  
Plasma Parameters ◽  
Earth’S Magnetosphere ◽  
Mode 2 ◽  
Resonant Instability ◽  
Earth's Magnetosphere ◽  
Current Region ◽  
Field Lines

It is well known that energetic protons having a ring-type, anisotropic velocity distribution can generate low-frequency electromagnetic waves, propagating nearly transverse to the geomagnetic field lines, in the ring current region of the Earth's magnetosphere by exciting mode 1 and mode 2 non-resonant instabilities and a resonant instability. In this paper, detailed investigations of the resonant and non-resonant instabilities are conducted as a function of plasma parameters such as ring speeds, electron temperatures, magnetic field strength and wave propagation directions. Our analysis is for parameters corresponding to the ring current region of the Earth's magnetosphere.

scholarly journals Detection of a plasmaspheric wind in the Earth's magnetosphere by the Cluster spacecraft

2013 ◽  
Vol 31 (7) ◽  
pp. 1143-1153 ◽  
Author(s):  
I. Dandouras
Keyword(s):  
Geomagnetic Field ◽  
Direct Detection ◽  
Substantial Contribution ◽  
Earth’S Magnetosphere ◽  
The Past ◽  
Astrophysical Objects ◽  
Earth's Magnetosphere ◽  
Additional Mode ◽  
Electric Field Change ◽  
Field Lines

Abstract. Plumes, forming at the plasmapause and released outwards, constitute a well-established mode for plasmaspheric material release to the Earth's magnetosphere. They are associated to active periods and the related electric field change. In 1992, Lemaire and Shunk proposed the existence of an additional mode for plasmaspheric material release to the Earth's magnetosphere: a plasmaspheric wind, steadily transporting cold plasmaspheric plasma outwards across the geomagnetic field lines, even during prolonged periods of quiet geomagnetic conditions. This has been proposed on a theoretical basis. Direct detection of this wind has, however, eluded observation in the past. Analysis of ion measurements, acquired in the outer plasmasphere by the CIS experiment onboard the four Cluster spacecraft, provide now an experimental confirmation of the plasmaspheric wind. This wind has been systematically detected in the outer plasmasphere during quiet and moderately active conditions, and calculations show that it could provide a substantial contribution to the magnetospheric plasma populations outside the Earth's plasmasphere. Similar winds should also exist on other planets, or astrophysical objects, quickly rotating and having an atmosphere and a magnetic field.

scholarly journals Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

2016 ◽  
Vol 34 (4) ◽  
pp. 473-484 ◽  
Author(s):  
Jinlei Zheng ◽  
Qiang Hu ◽  
Gary M. Webb ◽  
James F. McKenzie
Keyword(s):  
Magnetic Field ◽  
Amplitude Ratio ◽  
Low Frequency ◽  
Alfven Wave ◽  
Earth’S Magnetosphere ◽  
Background Magnetic Field ◽  
Earth's Magnetosphere ◽  
Klein Gordon ◽  
Field Lines ◽  
Hydromagnetic Waves

Abstract. Hydromagnetic waves, especially those of frequencies in the range of a few millihertz to a few hertz observed in the Earth's magnetosphere, are categorized as ultra low-frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach to examining the toroidal standing Aflvén waves in a background magnetic field by recasting the wave equation into a Klein–Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigenfrequency is greater than a critical frequency and a decaying type otherwise. We apply the approach to a compressed-dipole magnetic field model of the inner magnetosphere and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidal-mode standing Alfvén waves along field lines. In particular, we present a quantitative comparison with a recent spacecraft observation of a poloidal standing Alfvén wave in the Earth's magnetosphere. Our analysis based on the KG equation yields consistent results which agree with the spacecraft measurements of the wave period and the amplitude ratio between the magnetic field and electric field perturbations.

scholarly journals The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes

2006 ◽  
Vol 24 (11) ◽  
pp. 2901-2909 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
B. Isham ◽  
T. Hagfors ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Small Scale ◽  
Direction Parallel ◽  
Model Calculations ◽  
Amplitude Fluctuations ◽  
Field Lines ◽  
Experimental Values ◽  
Magnetic Zenith

Abstract. Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers it has been stressed that in the polar ionosphere the thermal self-focusing on striations during ionospheric modification is the main mechanism resulting in the formation of large-scale (hundreds of meters to kilometers) nonlinear structures aligned along the geomagnetic field (magnetic zenith effect). It has also been claimed that the maximum effects caused by small-scale (tens of meters) irregularities detected in satellite signals are also observed in the direction parallel to the magnetic field. Contrary to those studies, the present paper shows that the maximum in amplitude scintillations does not correspond strictly to the magnetic zenith direction because high latitude drifts typically cause a considerable anisotropy of small-scale irregularities in a plane perpendicular to the geomagnetic field resulting in a deviation of the amplitude-scintillation peak relative to the minimum angle between the line-of-sight to the satellite and direction of the geomagnetic field lines. The variance of the logarithmic relative amplitude fluctuations is considered here, which is a useful quantity in such studies. The experimental values of the variance are compared with model calculations and good agreement has been found. It is also shown from the experimental data that in most of the satellite passes a variance maximum occurs at a minimum in the phase fluctuations indicating that the artificial excitation of large-scale irregularities is minimum when the excitation of small-scale irregularities is maximum.

scholarly journals Electron dynamics during substorm dipolarization in Mercury's magnetosphere

2005 ◽  
Vol 23 (10) ◽  
pp. 3389-3398 ◽  
Author(s):  
D. C. Delcourt ◽  
K. Seki ◽  
N. Terada ◽  
Y. Miyoshi
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Expansion Phase ◽  
Earth’S Magnetosphere ◽  
High Energy Electrons ◽  
Earth's Magnetosphere ◽  
Magnetic Field Model ◽  
Particle Simulations ◽  
Field Lines ◽  
The Magnetic Field

Abstract. We examine the nonlinear dynamics of electrons during the expansion phase of substorms at Mercury using test particle simulations. A simple model of magnetic field line dipolarization is designed by rescaling a magnetic field model of the Earth's magnetosphere. The results of the simulations demonstrate that electrons may be subjected to significant energization on the time scale (several seconds) of the magnetic field reconfiguration. In a similar manner to ions in the near-Earth's magnetosphere, it is shown that low-energy (up to several tens of eV) electrons may not conserve the second adiabatic invariant during dipolarization, which leads to clusters of bouncing particles in the innermost magnetotail. On the other hand, it is found that, because of the stretching of the magnetic field lines, high-energy electrons (several keVs and above) do not behave adiabatically and possibly experience meandering (Speiser-type) motion around the midplane. We show that dipolarization of the magnetic field lines may be responsible for significant, though transient, (a few seconds) precipitation of energetic (several keVs) electrons onto the planet's surface. Prominent injections of energetic trapped electrons toward the planet are also obtained as a result of dipolarization. These injections, however, do not exhibit short-lived temporal modulations, as observed by Mariner-10, which thus appear to follow from a different mechanism than a simple convection surge.

scholarly journals The Relaxation of Reconnected Open Magnetic Field Lines in the Earth’s Magnetosphere

2020 ◽  
Vol 900 (1) ◽  
pp. 52
Author(s):  
Jiaying Xu ◽  
Xiaojun Xu ◽  
Jing Wang ◽  
Yudong Ye ◽  
Qing Chang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Earth’S Magnetosphere ◽  
Earth's Magnetosphere ◽  
Field Lines ◽  
Open Magnetic Field

scholarly journals Features of the impact of the solar wind diamagnetic structure on Earth’s magnetosphere

2017 ◽  
Vol 3 (4) ◽  
pp. 47-62 ◽  
Author(s):  
Владимир Пархомов ◽  
Vladimir Parhomov ◽  
Наталия Бородкова ◽  
Natalia Borodkova ◽  
Виктор Еселевич ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
High Speed ◽  
Geostationary Satellite ◽  
The West ◽  
Earth’S Magnetosphere ◽  
Capture Region ◽  
Earth's Magnetosphere ◽  
The Impact

In Earth’s orbit on June 28, 1999, there was a diamagnetic structure (DS) representing a filament with a uniquely high speed (about 900 km/s). We show that the filament is a part of the specific sporadic solar wind (SW) stream, which is characterized as a small interplanetary transient. We report the results of studies on the interaction between such a fast filament (DS) and Earth’s magnetosphere. Around noon hours at daytime cusp latitudes, we recorded a powerful aurora in the UV band (shockaurora), which rapidly spread to the west and east. Ground-based observations of geomagnetic field variations, auroral absorption, and auroras on the midnight meridian have shown the development of a powerful substorm-like disturbance (SLD) (AE~1000 nT), whose origin is associated with the impact of the SW diamagnetic structure on the magnetosphere. The geostationary satellite GOES-8, which was in the midnight sector of the outer quasi-capture region during SLD, recorded variations of the Bz and Bx geomagnetic field components corresponding to the dipolarization process.

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