Abstract
Abstract. Day-to-day fluctuations of the daily range of the geomagnetic field H at the equatorial electrojet stations Ancon (ANC, 77.0° W) and Sao Luis (SLZ, 44.2° W) are described for the period January–June 1993. The H field started increasing between midnight and sunrise, reaching a peak shortly before noon. The daily range of H was maximum during March and April and minimum during June. Regardless of the month, the range in H was significantly larger at ANC than at SLZ. The 27-day running mean of the range of H varied from 80 nT to 125 nT at SLZ and from 105 nT to 180 nT at ANC. The day-to-day values of the range of H showed very faithful variations at the two stations. The deviations of the daily range of H from its 27-day running mean values showed good correlation between the two stations. Some large storm-time effects were seen at both stations. The correlation was still significant, when data were corrected for Dst index values. It is suggested that the range in H at the two electrojet stations, separated by more than 2000 km, are affected by some common sources other than the ring current, which need to be identified. Spectral analysis of the range of H shows remarkable similarity at the two stations, with a dominant period of 15 days at both stations.
Highlights
The daily variations of the Earth’s magnetic field at the ground stations were suggested by Stewart (1882) as due to the movement of the conducting upper atmosphere across the vertical component of the Earth’s magnetic field arising due to the solar heating of the atmosphere. Chapman (1919) suggested that the regular tidal movement of the at-mosphere across the Earth’s magnetic field generates a regular pattern of electric field in the upper atmosphere, which causes currents that produce regular magnetic field variations at the ground
During any of the months, the daily range in H was larger at ANC than at SLZ
As expected of an equatorial station, the daily range in H at any of the stations was largest in the equinoctial months of March and lowest during the local winter month of June
Summary
The daily variations of the Earth’s magnetic field at the ground stations were suggested by Stewart (1882) as due to the movement of the conducting upper atmosphere across the vertical component of the Earth’s magnetic field arising due to the solar heating of the atmosphere. Chapman (1919) suggested that the regular tidal movement of the at-mosphere across the Earth’s magnetic field generates a regular pattern of electric field in the upper atmosphere, which causes currents that produce regular magnetic field variations at the ground. Day-to-day variations of the daily ranges of H at ANC and SLZ for the period January to June 1993. Significant correlation (.65) is seen in day-to-day variations of the daily range in H at the two stations that are separated by a distance over 2000 km.
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