Rocket-based vector magnetic measurement of an auroral birkeland current configuration
Casserly, Raymond Thomas
Cloutier, Paul A.
Master of Science
A rocket-borne experiment to study the currents associated with an auroral arc was conducted at Poker Flat, Alaska at 2122 LT on 24 February 1972. A vector magnetometer measured the magnetic field as the payload passed over an auroral band structure which had a visual intensity of > 4 kR. Changes in the magnitude and direction of the magnetic field along the trajectory were used to infer the configuration of a system of field-aligned (Birkeland) currents and auroral electrojets. The model current system consists of a pair of oppositely directed parallel sheet currents along the arc having current densities of ~27 MA/m and a north-south extent of approximately 9 km. Movement of the current sheets in range and azimuth prior to apogee is interpreted as being due to the presence of a large fold in the arc at that time. Two eastward electrojets each having a current magnitude of 3 to 4 x 1 amps are also inferred. One electrojet is located approximately in the center of the downward current sheet while the other is located just north of the upward current. Data from the onboard particle detectors showed that the net field-aligned current carried by precipitating electrons in the energy range .5-2 kev was ~5 MA/m in the northernmost sheet. However, there were no measured particles in that energy range that contributed to the downward sheet current inferred from the magnetometer data.