Measurements of ionospheric currents off the coast of Peru

Abstract

Four Nike‐Apache sounding rockets were launched off the coast of Peru, two near the magnetic dip equator and two to the north of the dip equator. Measurements were made of the magnetic field (for current density determination) with a proton magnetometer and of electron number density (proportional to conductivity) with a DC Langmuir probe. One of the dip equator flights (UNH 65‐4) was launched at the time of maximum negative effect of the lunar current system. The shape of the electrojet current profile is similar to that over India but with greater intensity. It appears that the lunar current system is most likely a modulation of the solar correlated currents. North of the dip equator the low‐latitude Sq currents were found to exist in two layers centered at 100 and 120 km in altitude. A reverse current, which may be a partial return current from the electrojet, was observed to the north of the electrojet at the altitude of the maximum intensity of the electrojet.

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…Later, he estimated the conductivity of the atmosphere that is required to explain Sq variations and attributed this conductivity to the ionization of the atmosphere caused by the solar radiation (Schuster 1908). The existence of the ionospheric currents was later confirmed experimentally by sounding rockets (e.g., Singer et al 1951;Cahill 1959;Davis et al 1967;Maynard 1967;Yabuzaki and Ogawa 1974;Pfaff et al 1997). It is now well established that electric currents of the order of several μA/m 2 flow on the dayside of the E-region ionosphere, in the altitude range of 90-150 km.…”

Equatorial electrojet at African longitudes: first results from magnetic measurements

“…Rocket experiments have been used to provide estimates of the current density along vertical pro®les (Maynard and Cahill, 1965;Maynard, 1967;Sampath and Sastry, 1979), which happened to be very similar. For example, Sampath and Sastry (1979) observed a maximum of the current density at the altitude of 106 km with a vertical half width of 12 km.…”

A correlation between measured E-region current and geomagnetic daily variation at equatorial latitude.

“…This fact leads to the further complication of separating the field into its planetary and its incremental parts before being able to interpret properly, not only the external but also the internal contributions (e.g., FORBUSH and CASAVERDE, 1961;ONwUMECHILLI, 1967).…”

“…DUHAU and ROMANELLI (1979) analyzed data from the Peruvian dip equator and found that: a) the usual hypothesis that the horizontal component of the planetary internal field is a fraction of 0.4 of the planetary external part (e.g., ONWUMECHILLI, 1967, andFORBUSH andCASAVERDE, 1961) could be inadequate for the studied zone, where the fraction appears to be as large as 0.7; b) currents flowing at F-region heights seem to contribute appreciably to the planetary field at the ground: c) as FORBUSH andCASAVERDE (1961), DAVIS et al (1967), and SHUMAN (1970) concluded, at these latitudes the equatorial electrojet induces within the earth a current that contributes significantly to the geomagnetic daily variations.…”