Quiet Period Variation of Horizontal Component of Geomagnetic Field along 210° Magnetic Meridian during the Low Solar Activity Year of 2010

Abstract

This study presents a quantitative analysis of the quiet-time variation of the horizontal (H) component of the geomagnetic field along the 210° magnetic meridian (210° MM) during the solar minimum year of 2010. Diurnal Sq(H) variations at DAV and YAP exhibit the characteristic daytime maximum, nocturnal minimum, and peak value at local noon. The maximum Sq(H) amplitude was recorded during the March equinox, with DAV reaching 94.81nT at 11:00 LT and YAP recording 85.54nT at 12:00 LT. During the September equinox, DAV peaked at 92.78nT at 10:00 LT, while YAP magnitude was 76.42nT at 11:00 LT. Solstitial analysis showed that the December solstice Sq(H) at YAP peaked at 84.73nT, exceeding the June solstice peak of 52.19nT. DAV recorded Sq(H) magnitudes of 89.56nT and 66.01nT during the December and June solstices, respectively, reflecting enhanced solar zenith proximity and seasonal conductivity during Southern Hemisphere summer. The latitudinal comparison revealed that DAV exhibited consistently higher Sq(H) amplitudes than YAP, despite YAP being closer to the magnetic equator. This is attributed to longitudinal variation in EEJ strength and regional differences in ionospheric conductivity. EEJ strength showed clear daytime enhancement. The maximum EEJ strength was observed at DAV with a magnitude of 62.30 nT at 10:00 LT with a corresponding early morning counter electrojet (MCEJ) of -6.91nT at 06:00 LT during the September equinox. The maximum EEJ and CEJ values of 61.69nT at 12:00 LT and -14.52nT at 08:00 LT were observed at YAP during the December and June solstices, respectively. The observed Sq(H) and EEJ profiles confirm established equatorial electrodynamics like enhanced Sq(H) during equinoxes, reduced amplitude during solstices, and peak EEJ near local noon. The results reinforce the role of solar zenith position, ionospheric conductivity, and geomagnetic latitude in modulating low-latitude current systems during solar minimum conditions.