Incoherent scatter measurements ofEregion conductivities and currents in the auroral zone

Abstract

Data taken by the incoherent scatter radar facility at Chatanika, Alaska, have been used to investigate ionospheric conductivities and electrical currents. During quiet days the conductivities appear to vary in a way consistent with ionization arising from solar EUV radiation. At these times the ratio between the height-integrated Hall and Pedersen conductivities is close to 2. In the evening hours, enhancements in the northward electric field are found to precede small increases in the conductivities that, from analysis of electron density profiles, arise from precipitation of 3-10 X 106 el cm -•' s -• sr -• in the energy range 3-20 keV. Str9ng enhancements of the Hall conductivity relative to the Pedersen conductivity occur during negative bays when the electric field is in a southwestward direction. These enhancements are caused by a relatively strong flux of 1-3 X 10 ? el cm -•' s -• sr -• in the energy range 15-20 keV. The ionospheric currents calculated in the geomagnetic east-west direction are in good agreement with the H component measured by a nearby magnetometer; this result indicates that the current causing the ground level magnetic fluctuations is a broad horizontal sheet current. The north-south ionospheric current, however, consistently disagrees with the observed D component in a manner that cannot easily be explained unless currents parallel to the earth's magnetic field are present. The parallel currents needed in daytime, however, are directed opposite to the Sq p current system, often inferred to explain the quiet day variations in auroral zone magnetograms. Finally, it is found that the neutral wind is of considerable importance in driving currents during quiet days in the auroral zone. Often these wind-driven currents oppose the current driven by the static e, lectric field.The incoherent scatter radar at Chatanika, Alaska (L -5.6, 3_ = 65ø), has been used previously by Doupnik et al. [1972], Banks et al. [1973, 1974], and others to investigate the behavior of electric fields in the auroral zone ionosphere. More recently, a number of new experiments have been made, and improved methods have been developed for analyzing the radar data to determine the E region Hall and Pedersen currents. In this paper the earlier studies are continued in an attempt to obtain a more comprehensive view of the relationship between electric fields, particle precipitation, ionospheric currents, and magnetic perturbations in the auroral zone.The relationship between ionospheric currents and ground level magnetic perturbations has been studied several times by using chemical clouds and rockets. Rees [1971], for example, has obtained short-term data indicating orthogonality between the drift direction of ion clouds in the auroral zone F region and the magnetic perturbation vector observed at ground level. Such results agree well with the earlier barium cloud experiments by Haerendel et al. [1969], Haerendel and Liist [1970], Fbppl et al. [1968], and Wescott et al. [1969]. In contrast, in the polar cap, Wescott et al...

Creation of the substorm current wedge through the perturbation of the directly driven current system: a new model for substorm expansion

“…Based on the contention of Kamide and Vickrey (1983) that the westward electrojet is conductivity dominated in the midnight and morning sector, and the observations by Brekke et al (1974) and Opgenoorth et al (1994) that the ratio H / P increases to >2:1 during active times in those sectors, we effectively increased H / P in the morning hours while keeping the evening sector conductivity ratio almost unchanged.…”

A study of the Joule and Lorentz inputs in the production of atmospheric gravity waves in the upper thermosphere

“…(1). Magnetometer data was used to obtain the height-integrated current density j whilst Hall and Pedersen conductivity observations (Brekke et al, 1974) were used to calculate more precise values for the Cowling conductivity. A mean value for L/J of 2.37 was obtained for an electric ®eld of % 43 mV/m (Hunsucker, 1977); using the equations of Richmond and data from the same event, a value of L/J of 3.13 was obtained (Hunsucker, 1982).…”

Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone

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