scholarly journals Generic Magnetic Field Intensity Profiles of Interplanetary Coronal Mass Ejections at Mercury, Venus, and Earth From Superposed Epoch Analyses

2019 ◽  
Vol 124 (2) ◽  
pp. 812-836 ◽  
Author(s):  
Miho Janvier ◽  
Reka M. Winslow ◽  
Simon Good ◽  
Elise Bonhomme ◽  
Pascal Démoulin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Intensity ◽  
Coronal Mass Ejections ◽  
Magnetic Field Intensity ◽  
Interplanetary Coronal Mass Ejections

scholarly journals Selection effects in identifying magnetic clouds and the importance of the closest approach parameter

2010 ◽  
Vol 28 (8) ◽  
pp. 1539-1552 ◽  
Author(s):  
R. P. Lepping ◽  
C.-C. Wu
Keyword(s):  
Magnetic Field ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Radial Distance ◽  
Selection Effect ◽  
Magnetic Clouds ◽  
Intensity Change ◽  
Interplanetary Coronal Mass Ejections ◽  
Event Selection ◽  
The One

Abstract. This study is motivated by the unusually low number of magnetic clouds (MCs) that are strictly identified within interplanetary coronal mass ejections (ICMEs), as observed at 1 AU; this is usually estimated to be around 30% or lower. But a looser definition of MCs may significantly increase this percentage. Another motivation is the unexpected shape of the occurrence distribution of the observers' "closest approach distances" (measured from a MC's axis, and called CA) which drops off somewhat rapidly as |CA| (in % of MC radius) approaches 100%, based on earlier studies. We suggest, for various geometrical and physical reasons, that the |CA|-distribution should be somewhere between a uniform one and the one actually observed, and therefore the 30% estimate should be higher. So we ask, When there is a failure to identify a MC within an ICME, is it occasionally due to a large |CA| passage, making MC identification more difficult, i.e., is it due to an event selection effect? In attempting to answer this question we examine WIND data to obtain an accurate distribution of the number of MCs vs. |CA| distance, whether the event is ICME-related or not, where initially a large number of cases (N=98) are considered. This gives a frequence distribution that is far from uniform, confirming earlier studies. This along with the fact that there are many ICME identification-parameters that do not depend on |CA| suggest that, indeed an MC event selection effect may explain at least part of the low ratio of (No. MCs)/(No. ICMEs). We also show that there is an acceptable geometrical and physical consistency in the relationships for both average "normalized" magnetic field intensity change and field direction change vs. |CA| within a MC, suggesting that our estimates of |CA|, BO (magnetic field intensity on the axis), and choice of a proper "cloud coordinate" system (all needed in the analysis) are acceptably accurate. Therefore, the MC fitting model (Lepping et al., 1990) is adequate, on average, for our analysis. However, this selection effect is not likely to completely answer our original question, on the unexpected ratio of MCs to ICMEs, so we must look for other factors, such as peculiarities of CME birth conditions. As a by-product of this analysis, we determine that the first order structural effects within a MC due to its interaction with the solar wind, plus the MC's usual expansion at 1 AU (i.e., the non-force free components of the MC's field) are, on average, weakly dependent on radial distance from the MC's axis; that is, in the outer reaches of a typical MC the non-force free effects show up, but even there they are rather weak. Finally, we show that it is not likely that a MC's size distribution statistically controls the occurrence distribution of the estimated |CA|s.

scholarly journals Multi-point ground-based ULF magnetic field observations in Europe during seismic active periods in 2004 and 2005

2008 ◽  
Vol 8 (3) ◽  
pp. 501-507 ◽  
Author(s):  
G. Prattes ◽  
K. Schwingenschuh ◽  
H. U. Eichelberger ◽  
W. Magnes ◽  
M. Boudjada ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Intensity ◽  
Seismic Activity ◽  
Magnetic Field Intensity ◽  
Field Measurements ◽  
Fluxgate Magnetometer ◽  
Vertical Magnetic Field ◽  
Earthquake Epicenter ◽  
Electromagnetic Noise ◽  
Horizontal Magnetic Field

Abstract. We present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths crust considering an average electrical conductivity of <σ>=10−3 S/m and a certain distance of the observatory to the earthquake epicenter.

Numerical Investigations on Rotatry Micropolar Fluid in Hydromagnetics Permeated with Suspended Particles Saturating Porous Medium

2021 ◽  
pp. 57-69
Author(s):  
Pushap Lata Sharma ◽  
Sumit Gupta
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Suspended Particles ◽  
Rotation Parameter ◽  
Wave Number ◽  
Stationary Convection ◽  
Micropolar Fluids ◽  
Medium Permeability

This paper deals with the convection of micropolar fluids heated and soluted from below in the presence of suspended particles (fine dust) and uniform vertical rotation and uniform vertical magnetic field in a porous medium. Using the Boussinesq approximation, the linearized stability theory and normal mode analysis, the exact solutions are obtained for the case of two free boundaries. It is found that the presence of the suspended particles number density, the rotation parameter, stable solute, magnetic field intensity and medium permeability bring oscillatory modes which were non–existent in their absence. It is found that the presence of coupling between thermal and micropolar effects, rotation parameter, solute parameter and suspended particles may introduce overstability in the system. Graphs have been plotted by giving numerical values to the parameters accounting for rotation parameter , magnetic field solute parameter, the dynamic microrotation viscosity and coefficient of angular viscosity to depict the stability characteristics, for both the cases of stationary convection and overstability. It is found that Rayleigh number for the case of overstability and stationary convection increases with increase in rotation parameter, as well as with magnetic field intensity, solute parameter and decreases with increase in micropolar coefficients and medium permeability, for a fixed wave number, implying thereby the stabilizing effect of rotation parameter, magnetic field intensity ,solute parameter and destabilizing effect of micropolar coefficients and medium permeability on the thermosolutal convection of micropolar fluids.

Tunable amplified spontaneous emission based on liquid magnetically responsive photonic crystals

2019 ◽  
Vol 7 (13) ◽  
pp. 3740-3743 ◽  
Author(s):  
Ying Li ◽  
Yue Long ◽  
Guoqiang Yang ◽  
Chen-Ho Tung ◽  
Kai Song
Keyword(s):  
Magnetic Field ◽  
Photonic Crystals ◽  
Spontaneous Emission ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Amplified Spontaneous Emission ◽  
The Magnetic Field

The wavelength of amplified spontaneous emission based on liquid magnetically responsive photonic crystals can be tuned by simply changing the magnetic field intensity.

scholarly journals Rotating and propagating LIB stabilized by self-induced magnetic field

1984 ◽  
Vol 2 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Hiroyuki Murakami ◽  
Takayuki Aoki ◽  
Shigeo Kawata ◽  
Keishiro Niu
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Ion Beam ◽  
Axial Direction ◽  
Induced Magnetic Field ◽  
Tearing Instability ◽  
The Mean ◽  
Steady State Solutions

Rotating motion of a propagating LIB is analyzed in order to suppress the mixed mode of the Kelvin-Helmholtz instability, the tearing instability and the sausage instability by the action of a self-induced magnetic field in the axial direction. The beams are assumed to be charge-neutralized but not current-neutralized. The steady-state solutions of a propagating LIB with rotation are first obtained numerically. Through the dispersion relation with respect to the ikonal type of perturbations, which are added to the steady-state solutions, the growth rates of instabilities appearing in an LIB are obtained. It is concluded that if the mean rotating velocity of an LIB is comparable to the propagation velocity, in other words, if the induced magnetic field intensity in the axial direction is comparable to the magnetic field intensity in the azimuthal direction, the instability disappears in the propagating ion beam.

Sign in / Sign up

Export Citation Format

Share Document