Evidence for ionosphere currents from rocket experiments near the geomagnetic equator

Abstract

Records of magnetic field as a function of altitude have been obtained from total‐field magnetometers mounted in two Aerobee sounding rockets which were fired from the seaplane tender USS Norton Sound in March 1949. The flights were made 60 miles apart at approximately 89° west longitude, 11° south latitude, or geomagnetic longitude 341°, geomagnetic latitude −1°. The first rocket, Aerobee Round A‐10, was fired on March 17 at 17h 20m 90th meridian time; Round A‐11 was fired on March 22 at 11h 20m 90th meridian time. In Aerobee A‐10 the field decreased between 20 and 105 km in accordance with the simple dipole field, while in Aerobee A‐11 a discontinuity of 4±0.5 milligauss was observed in the altitude range of 93 to 105 km. These results (1) establish experimentally the existence of a current system in the E‐region of the ionosphere which is responsible for the diurnal variation of the earth's magnetic field at sea level; and (2) lend strong support to the dynamo theory of the daily magnetic variation which was originally proposed by Balfour Stewart and Schuster.

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.…”

A latitude survey of the equatorial electrojet with rocket-borne magnetometers

“…Much information about the equatorial electrojet is already available from previous rocket flights (Singer, et al, 1951;Cahill, 1959 andCahill, 1965b) and from studies based on data from magnetic observatories and other knowledge. These include studies by Bartels and Johnston, 1950;Onwumechilli, 1959;Forbush and Casaverde, 1961;Rao and Raja Rao, 1963;and Sugiura and Cain, 1965.…”

Rocket Measurements of Mid-Latitude Sq Currents

“…The other two flights measured a current sheet with lower edge at 105km and upper edge at 123km, with the total current being in agreement with that expected from the ground observations. Ionospheric currents have been detected by rocket-borne magnetometers flown into the equatorjet (Singer et al, 1951;Cahill, 1959 a), the auroral electrojet (Meredith et al, 1961) and in the northern polar cap (Cahill,1959 b). Similar attempts to detect mid-latitude ionospheric currents have been generally unsuccessful until this year (Burrows and Hall, 1964) because of one or more of the following problems: uncertain knowledge of the reference magnetic field, rocket trajectory errors, low precision of the magnetic field measurement, the low current density in the mid-latitude ionosphere, and the relative insensitivity of total field magnetometers to the magnetic effects of horizontal sheet currents at high magnetic inclination.…”