Daily variations of geomagnetic HD and Z-field at equatorial latitudes

Abstract

With the establishment of the new geomagnetic field observations in the Ocean Hemisphere Network Project (OHP) in Japan, minutes values of geomagnetic components, H D and Z have been recorded. The hourly mean values were used to study the variations in these three components at these new equatorial electrojet regions. The results of the analysis carried out revealed that the amplitude of d H has diurnal variation which peaks during the day at about local noon in all the three equatorial electrojet regions. This diurnal variation in H with Sq (H ) enhancement in all the three regions are attributed to the enhanced dynamo action at these regions. Diurnal variation as observed in D indicates that the equatorial electrojet current system has both east-west and north-south components. The pronounced magnitude of Z variation as observed in Kiritimati is attributed mainly to sea induction. Also some abnormal features were observed on 23rd of January at Huancayo, in the components. Seasonal variations with more pronounced equinoctial maximum were observed in H than in Z . D component showed no consistent seasonal variation in all the regions. The equinoctial maximum is due to enhanced equatorial electron density at equinox. More research work, if carried out in these new regions will be useful in making more new contributions to the field of the dynamics of the equatorial electrojet region.

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

“…It is widely known that EEJ strength shows semiannual variation with a minimum during solstice periods (Tarpley, 1973;Okeke and Hamano, 2000;Chandra et al, 2000). This semiannual variation of EEJ strength is apparent irrespective of solar activity, with weaker EEJ strength during low solar activity periods.…”

Reply to “Comments on the paper entitled ‘Daily variations of geomagnetic H, D and Z-fields at equatorial latitudes by F. N. Okeke and Y. Hamano’ ”

“…Even though the ratio Z / H is approximately 0.63 as Rastogi quoted from Doumouya et al (1998) and approximately 0.75 in Okeke and Hamano (2000), the fact remains that the pronounced variation was observed.…”

“…It is not correct to rule out the possibility that the pronounced variation of Z observed in Kiritimati could be due to sea induction. See page 242 of Okeke and Hamano (2000) for detailed explanation.…”

Non-linear analysis of geomagnetic time series from Etna volcano

“…2 are shown the power spectra of simple differences and cleaned differences between DGL and PDN stations. The analysis of the simple differences power spectra clearly shows prominent peaks centered around diurnal components at the period of 8, 12 and 24 h. Although these variations are the most regular of the all geomagnetic changes, they tend not to repeat exactly itself but relevant differences could be noted from day to day (Okeke and Hamano, 2000). The dayto-day variability is thought to arise from the variations of the solar and geomagnetic activity.…”