Rocket Measurements of Mid-Latitude Sq Currents

Abstract

Rubidium-vapor magnetometers were flown to altitudes near 150km over Wallops Island, Virginia in three Nike-Apache Rockets. One flight was made at a time when no ionospheric current was expected and none was encountered. 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.The present paper reports the results of a partial analysis of three rocket flights performed at Wallops Island, Virginia (38N, 75W) during June 1964. In this series, double gas cell rubidium-vapor magnetometers were flown in Nike-Apache rockets to altitudes near 150km. The flight magnetometer was designed specifically for use in small rockets. Its sensor is 51/2 in. long and weighs 9 oz; the total instrument weight is 4 lbs. The Rb-vapor magnetometer measures the absolute scalar intensity of the magnetic field by employing optical pumping to measure the Zeeman splitting of selected energy levels in rubidium. The Zeeman splitting is optically detected as light modulation at the Larmor frequency. f(cps)=466743.8B+K359.4B2 using Rb-85 where B is in gauss and K represents the fraction (K<1) of the second-order term that appears in a self-oscillating magnetometer when the field is reversed. By employing a double-cell magnetometer as is used here the factor K is made zero in the above relationship. The single or double gas cell magnetometer has null regions (regions of magnetic field direction relative to the magnetometer optical axis in which the signal-to-noise ratio is small) where measurements are not obtained. One null region is centered on the optical axis and has a half-angle of 100, the second null has a half-angle of 5 or less centered on the plane perpendicular to the optical axis.In each rocket the magnetometer was mounted with its optical axis inclined 45 to the rocket axis. In this orientation and with the rockets spin-stabilized at 5-6 rps null zones

Tests of electrodynamic consistency from daytime ionospheric drift observations

“…Figure 7 shows the current profiles for 1000 LT by using the (2, 4) mode. The westward current density component is compared with features (indicated by arrows) derived for the current from a magnetometer flown aboard a rocket at Wallops Island at the same local time [Davis et al, 1965]. The maximum current density, the altitude of maximum, and the width of the current sheet are in reasonable agreement with our calculations for the (2, 4) winds.…”

Rocket measurement ofSqionospheric currents over Kagoshima, Japan

“…On the other hand, on the ground the frequency of the telemeter signal was multiplied by a factor of 9, and we in- When the present results are compared with those obtained at Woomera [Burrows and Hall, 1965] and at Wallops Island [Davis et al, 1965], it must be important to notice that in the region of geomagnetic latitudes between 20 ø and 50 ø the altitude of the lower edge of the current sheet increases gradually with the geomagnetic latitude and the altitude of the upper edge of the current sheet increases more rapidly. It can be considered that the altitude of the lower edge is generally determined by the lower boundary of the electron density profile.…”

A Note on the Height of the Geomagnetic Sq Current

“…The experiments of Burrow and Hall (1965) and of Davis et al (1965) Fig. 2 indicates could resolve the above mentioned discrepancy.…”