A study of rocket measurements of ionospheric currents-II. Ionospheric currents outside the dip equatorial zone

Abstract

SUMMARY This second part of the series has studied ionospheric currents outside the dip equatorial zone in the three groups of: high‐latitude currents beyond 70° latitude (Group 6), daytime currents within 35° to 70° dip latitude (Group 5), and daytime currents within 7° to 35° dip latitude (Group 4). Ionospheric currents have been found and measured with rockets in all three groups, and their directions are in conformity with expectations from geomagnetic variations: eastwards equatorward of the Sq focus (Group 4), westwards between the Sq focus and high latitudes (Group 5), and complex in the higher and polar latitudes (Group 6). Of great interest is the discovery that the currents occur in the two eastward layers in Group 4 but only in one layer in Groups 5 and 6. The altitude of peak current is 105 ± 8 km and 123 ± 8 km for the two layers of Group 4 respectively, 112 ± 3 km in Group 5 and about 120 km in Group 6. The peak current density is about 1.5 A km‐2 and 1 A km‐2 for layers 1 and 2 respectively in Group 4 and difficult to determine in Groups 5 and 6. The altitude extent of the current layers decreases towards the Sq focus. On average the altitude extent is 19 ± 7 km and 15 ± 8 km for layers 1 and 2 of Group 4 respectively, 17 ± 3 km in Group 5 and is difficult to determine in Group 6. The two peaks of current density in Group 4 did not appear to correlate with peaks of electron density measured with the same rocket. However, the upper current peak occurred near the peak of Pedersen conductivity.

Equivalent current systems for the annual and semiannual Sq variations observed along the 210°MM CPMN stations

“…The northern vortex is in a counterclockwise direction and the southern one is in a clockwise direction [e.g., Richmond , 1998]. In situ observations by rockets have confirmed the existence of ionospheric currents [e.g., Onwumechili , 1992]. As for satellite observation, Turner et al [2007] detected S q variations in total magnetic intensity data, which is also consistent with ground measurements.…”