scholarly journals Geomagnetic field H, Z, and electromagnetic induction features of coronal mass ejections in association with geomagnetic storm at African longitudes

2018 ◽  
Vol 96 (6) ◽  
pp. 654-663
Author(s):  
E.O. Falayi ◽  
J.O. Adepitan ◽  
O.A. Oyebanjo
Keyword(s):  
Electric Fields ◽  
Geomagnetic Field ◽  
Electromagnetic Induction ◽  
Geomagnetic Disturbance ◽  
Wavelet Spectrum ◽  
Magnetospheric Convection ◽  
Cycle 24 ◽  
Electric Fields And Currents ◽  
Minimum Disturbance ◽  
Derivatives Of

The largest geomagnetic disturbance caused by a coronal mass ejection (CME) of solar cycle 24 recorded on both 17 March and 22 June 2015 with minimum disturbance storm time values of −223 and −195 nT, respectively, was investigated. This study examines the effect of CME on Earth’s geomagnetic field, which includes the time derivatives of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction ΔZ/ΔH at African longitudes (AAE, MBO, HBK, HER, and TAM). The results demonstrated enhancement of dH/dt and dZ/dt in the daytime over the equatorial zone (AAE and MBO) and mid-latitudes (TAM, HER, and HBK) on 17 March 2015. Nighttime enhancement was observed on 22 June 2015 over the equatorial zones and mid-latitudes. Wavelet spectrum approach is used to investigate ΔZ/ΔH variation observed at AAE, MBO, HBK, HER, and TAM. The CME may have influence on time derivatives of geomagnetic field H, Z, and electromagnetic induction at the African longitudes, which may be associated with perturbations in electric fields and currents in the equatorial and low-latitude magnetic field linked with the changes in magnetospheric convection.

Response of ionospheric disturbance dynamo and electromagnetic induction during geomagnetic storm

2015 ◽  
Vol 93 (10) ◽  
pp. 1156-1163 ◽  
Author(s):  
E.O. Falayi ◽  
A.B. Rabiu ◽  
O.S. Bolaji ◽  
R.S. Fayose
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Electric Fields ◽  
Geomagnetic Field ◽  
Electromagnetic Induction ◽  
Geomagnetic Storms ◽  
Ionospheric Disturbance ◽  
Solar Wind Speed ◽  
Magnetospheric Convection ◽  
The Difference

During geomagnetic storms, the direct penetration of magnetospheric convection electric field and the ionospheric disturbance dynamo (IDD) take place in the ionosphere. In this paper, we studied variability of IDD and electromagnetic induction (EMI) at different latitudinal sectors during the geomagnetic storms on 7 and 8 September 2002 and 20 and 21 November 2003 with high solar wind speed due to coronal mass ejection. This investigation employs geomagnetic field components (H and Z), the geomagnetic indices (Dst, AL, and AU), solar wind speed (Vx), and interplanetary magnetic field (Bz). It was observed that the H component of geomagnetic field decreases across latitudes, and varies with Vx, Bz, Dst, AL, and AU indices throughout the difference phases of the storm. Our result demonstrated the dominance of the IDD during the nighttime compared to the daytime. This implies that neutral dynamic wind is greater at night than during the day. Higher ratio ΔZ/ΔH is observed at nighttime because of the reduction on the E region conductivity, which allowed F region electric fields to dominate.

The Southern Hemisphere Auroral Radar Experiment (SHARE)

1994 ◽  
Vol 6 (1) ◽  
pp. 123-124 ◽  
Author(s):  
J. R. Dudeney ◽  
K. B. Baker ◽  
P. H. Stoker ◽  
A. D. M. Walker
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Geomagnetic Field ◽  
Ionospheric Plasma ◽  
Dynamic Responses ◽  
Space Environment ◽  
Near Earth Space ◽  
Energy Flows ◽  
Powerful Means ◽  
Electric Fields And Currents

The near Earth space environment (known as Geospace) is dominated by the interaction between the solar wind and the geomagnetic field, which creates the magnetosphere. Considerable energy flows from the solar wind into the magnetosphere and ends up in the Earth's upper atmosphere (the thermosphere and ionosphere). The coupling of the geomagnetic field with that of the solar wind (known as the interplanetary magnetic field, or IMF) produces a variety of electro-dynamic responses with signatures such as electric fields and currents in the polar ionospheres. These produce, inter alia, motion of the ionospheric plasma (at altitudes between 100 and 1000kms) which can be monitored from the ground using radar techniques. Analysis of such plasma motion provides a very powerful means of investigating the nature of the interactions taking place at the boundaries between the magnetosphere and the solar wind. To do this effectively requires simultaneous measurements over as large an area (in latitude and longitude) as possible.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

Computational assessment of effects of electric fields and currents in tokamak edge plasmas

1995 ◽  
Vol 220-222 ◽  
pp. 982-986 ◽  
Author(s):  
M. Baelmans ◽  
D. Reiter ◽  
R.R. Weynants ◽  
R. Schneider
Keyword(s):  
Electric Fields ◽  
Tokamak Edge ◽  
Edge Plasmas ◽  
Electric Fields And Currents

scholarly journals Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

2002 ◽  
Vol 20 (12) ◽  
pp. 1977-1985 ◽  
Author(s):  
R. Sridharan ◽  
C. V. Devasia ◽  
N. Jyoti ◽  
Diwakar Tiwari ◽  
K. S. Viswanathan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Solar Eclipse ◽  
Equatorial Ionosphere ◽  
Hf Radar ◽  
F Region ◽  
Large Enhancement ◽  
Temporal Structures ◽  
E Region ◽  
Field Lines ◽  
Electric Fields And Currents

Abstract. The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i) the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii) significant increase in h' F immediately following the eclipse and (iii) distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F) rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

scholarly journals Regional estimation of electric fields and currents in the polar ionosphere

1995 ◽  
Vol 22 (3) ◽  
pp. 283-286 ◽  
Author(s):  
Mariko Sato ◽  
Y. Kamide ◽  
A. D. Richmond ◽  
A. Brekke ◽  
S. Nozawa
Keyword(s):  
Electric Fields ◽  
Polar Ionosphere ◽  
Regional Estimation ◽  
Electric Fields And Currents
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