VECTOR MEASUREMENT OF THE MID-LATITUDE SQ IONOSPHERIC CURRENT SYSTEM

This paper reports the results of two flights of vector magnetometer systems designed to measure the magnitude and direction of the ionospheric current system responsible for the solar quiet daily geomagnetic variation. The measurements were obtained from cesium vapor magnetometers with bias coils flown aboard sounding rockets from Wallops Island, Virginia. Instrumental difficulties on both flights limited the resolution of measurement, but the data indicated that current sheets were penetrated on both flights. These current sheets were observed to be thinner and more intense than those measured by previous investigators, and were confined to the lower edge of the altitude range over which currents have usually been observed. The unusual altitude profiles on both flights and an anomalously large current magnitude with a fluctuating direction observed on the second flight are attributed to localized enhancement of ionospheric electron concentration in sporadic E layers observed in ionograms taken during the flights. Because of disturbed ionospheric conditions and unknown boundary effects due to horizontal localization of the sporadic E layer, it is difficult to evaluate the validity of theoretical conductivity models. However, calculations of the conductivity profile required by the current position and intensity indicate that the observed current structure requires electron concentration enhancement compatible with that experimentally observed in sporadic E layers. Previous theoretical work also predicts a localized enhancement of the Sq current confined to the horizontal extent of the sporadic E layer, although such a large enhancement as was observed is not easily explainable.

[1]  N. Maynard.  Measurements of ionospheric currents off the coast of Peru , 1967 .

[2]  J. D. Stolarik,et al.  A latitude survey of the equatorial electrojet with rocket-borne magnetometers , 1967 .

[3]  E. Schmerling.  Advances in ionospheric physics in the rocket and satellite era. , 1966 .

[4]  D. Hunten,et al.  Quenching of metastable states of atomic and molecular oxygen and nitrogen , 1966 .

[5]  R. A. Wagner,et al.  On the equatorial electrojet , 1966 .

[6]  J. Cain,et al.  A model equatorial electrojet , 1966 .

[7]  D. Winch.  THE Sq OVERHEAD CURRENT SYSTEM APPROXIMATION , 1966 .

[8]  L. J. Cahill,et al.  Preliminary results of measurements of Sq currents and the equatorial electrojet near Peru , 1965 .

[9]  L. J. Cahill,et al.  Measurement of the equatorial electrojet over India , 1965 .

[10]  J. D. Stolarik,et al.  Rocket measurements of S sub q currents at midlatitude. , 1965 .

[11]  A. Onwumechilli,et al.  Seasonal studies of the equatorial electrojet during low solar activity , 1965 .

[12]  S. Matsushita.  Global presentation of the external Sq and L current systems , 1965 .

[13]  S. Akasofu,et al.  Dynamo action in the ionosphere and motions of the magnetospheric plasma: I. Symmetric dynamo action , 1965 .

[14]  Sadami Matsushita,et al.  On the Geomagnetic Solar Quiet Daily Variation Field , 1965 .

[15]  L. J. Cahill,et al.  PRELIMINARY RESULTS OF MEASUREMENTS OF THE EQUATORIAL ELECTROJET OVER INDIA , 1965 .

[16]  H. Maéda.  Electric fields in the magnetosphere associated with daily geomagnetic variations and their effects on trapped particles , 1964 .

[17]  J. Fejer.  ATMOSPHERIC TIDES AND ASSOCIATED MAGNETIC EFFECTS , 1964 .

[18]  E. Wescott,et al.  The Sq variation at geomagnetically conjugate areas , 1963 .

[19]  D. Fairfield.  Ionosphere current patterns in high latitudes , 1963 .

[20]  S. T. Butler,et al.  The solar semidiurnal atmospheric oscillation , 1961 .

[21]  B. Shuman,et al.  Rocket measurements of the magnetic field above New Mexico , 1961 .

[22]  M. Hasegawa.  On the position of the focus of the geomagnetic Sq current system , 1960 .

[23]  L. J. Cahill,et al.  Detection of an electrical current in the ionosphere above Greenland , 1959 .

[24]  L. J. Cahill.  Investigation of the equatorial electrojet by rocket magnetometer , 1959 .

[25]  J. D. Stolarik,et al.  The Earth's magnetic field above WSPG, New Mexico, from rocket measurements , 1958 .

[26]  S. Chapman.  The electrical conductivity of the ionosphere: A review , 1956 .

[27]  K. F. Wasserfall.  Diurnal Sq‐variation and overhead current‐system, July 1933 , 1953 .

[28]  D. F. Martyn,et al.  Conductivity of the Ionosphere , 1952, Nature.

[29]  S. Singer,et al.  Evidence for Ionosphere Currents from Rocket Experiments Near the Geomagnetic Equator , 1951 .

[30]  S. Singer,et al.  Measurement of the Earth's Magnetic Field at High Altitudes at White Sands, New Mexico , 1950 .

[31]  A. Schuster.  The Diurnal Variation of Terrestrial Magnetism , 1907, Nature.

[32]  H. Kamiyama.  HEIGHT PROFILE IN THE Sq CURRENT IN THE MIDLATITUDE IONOSPHERE. , 1966 .

[33]  J. Virginia Lincoln,et al.  Geomagnetic and solar data , 1966 .

[34]  K. G. Ivanov.  THE INFLUENCE OF A LOCAL INCREASE OF CONDUCTIVITY OF THE IONOSPHERE ON Sq VARIATION OF THE EARTH'S MAGNETIC FIELD , 1963 .

[35]  S. Matsushita.  Interrelations of Sporadic E and Ionospheric Currents , 1962 .

[36]  A. J. Zmuda.  Some characteristics of the upper‐air magnetic field and ionospheric currents , 1960 .

[37]  J. Fejer.  Semidiurnal currents and electron drifts in the ionosphere , 1954 .

[38]  S. Chapman.  I. The solar and lunar diurnal variations of terrestrial magnetism , 1919 .