Storm-time variation of the horizontal and vertical components of the geomagnetic fields and rate of induction at different latitudes

The paper presents the hourly mean variation of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction DH/DZ at different latitudes during magnetic storm of 20 March 2001 and 1 October 2001. The results of the analysis revealed that at high latitude stations greater than 60�, the reduction in DH component was noticed after the noon time while other stations less than 60� experienced reduction of H in the morning time during the geomagnetic storm. Large amplitude of DH and DZ were exhibited during the daytime over the equatorial zone, the amplitude decreases from mid latitudes to the dip equator during the nighttime. The daytime enhancement of DH at AAE, BAN and MBO suggest the presence of a strong eastward directed current which comes under the influence of electrojet. There were strong positive and negative correlations between ring current (DR) and horizontal component of the magnetic field DH. The effect of rate of induction is more significant at high latitudes than lower latitudes, during the geomagnetic storm. More enhancement in rate of induction occurred at nighttime than daytime. This result may be from other sources other than the ionosphere that is magnetospheric process significantly contributes toward the variation of induction. Keywords: Geomagnetic field; Geomagnetic storm; Electromagnetic induction; Ring current; Coronal mass ejectio

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

The largest geomagnetic disturbance caused by coronal mass ejection (CME) of solar cycle 24 recorded on both 17 March and 22 June 2015 with minimum Dst values of −223 and −195 nT respectively was investigated. This study examine the effect of coronal mass ejection (CME) on Earth geomagnetic field which include 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 at 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 an influence on time derivatives of geomagnetic field H, Z and electromagnetic induction at the African longitudes which might be associated with perturbations in electric fields and currents in the equatorial and low latitude magnetic field linked with the changes in magnetospheric convection.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author