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...

Auroral zone E region neutral winds have been derived from simultaneous measurements of ion drift velocities at different altitudes by the incoherent scatter radar facility at Chatanika, Alaska (L = 5.6, Λ = 65°). The wind derived for quiet and moderately disturbed days shows a consistent pattern during the daytime and appears to be that expected from a day‐night pressure asymmetry. In the nighttime, however, the winds are much more variable, apparently responding to the momentum transfer and heating effects of ion drag when sizable electric fields and electron densities are present.

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Experiments conducted with the Chatanika, Alaska, incoherent scatter radar observed the ionospheric convection pattern equatorward of the noontime cleft. There plasma transport is characterized by low‐speed convergence toward a meridian centered somewhat before noon and rotation of the flow into a poleward direction at higher latitudes. For undisturbed conditions there is only weak convection at noon at these latitudes, but the eastward electric field reaches a maximum of 15 mV/m 2–4 hours before and after noon at latitudes between 70°Λ and 74°Λ. During active conditions at the peak of the solar cycle the ionospheric cleft was located within the Chatanika field of view on several occasions. A longitudinally narrow region of rapid poleward convection near noon was not observed; rather, poleward flow occurred over a 3–4 hour spread of local time. For disturbed conditions, the prenoon and postnoon regions of plasma entry into the polar cap were enhanced, and an eastward electric field of 25 mV/m was seen across the 2 hours of local time around noon. High‐density F region plasma was observed convecting poleward through the cleft from a source at lower latitudes in the afternoon sector. Such plasma, seen at very high latitudes within the polar cap, serves as a tracer of the convection pattern away from the cleft.

The latitudinal distributions of convection electric fields, height-integrated Hall (ZH) and Pedersen (Zp)conductivities, and horizontal currents in the auroral ionosphere have been measured with the Chatanika incoherent scatter radar for the range of invariant latitudes 63o-68 ø . Approximately 60 hours of data were obtained for three geomagnetically disturbed days: January 18, May 16, and May 17, 1974. During this observation period the general electric field properties, as functions of latitude and time, were as follows:(1) Strong electric fields in the range 50-100 mV/m were typically directed northward in the afternoonevening sector and southward in the morning sector; (2) the electric field strength tended to increase with increasing latitude, with latitudinal scale lengths of 1 ø-3ø. (3) In several instances a reversal of the electric field direction occurred at the highest latitudes probed, corresponding to antisunward plasma convection near the boundary of the polar cap. (4) The Harang discontinuity in the electric field was seen in the midnight sector (2200-0100 MLT) as a complex rotation of the electric field vector counterclockwise from northward through westward to southward, beginning at the highest latitudes, as the radar moved in local time through the Harang discontinuity. The Harang discontinuity region was often slanted in local time and latitude from the northwest to the southeast. Strong westward electric fields were seen dividing regions of northward and southward electric fields on the western and eastern sides, respectively, of the discontinuity. Association of the electric fields with the conductivities showed that (5) those early evening sector electric fields which were embedded within diffuse auroral precipitation associated with conductivities Zp = 8-12 mhos and ZH = 16-24 mhos tended to have less latitudinal and temporal structure than did midnight-morning sector electric fields embedded within active and highly structured precipitation and conductivities Zp = 10-16 mhos and Zn= 20-60 mhos and that (6) the local time transition between the diffuse precipitation-conductivity zone in the evening sector and the harder, active precipitation-conductivity zone in the midnight-morning sector coincided with the Harang discontinuity in the electric field. Association of the electric fields with interplanetary magnetic field (IMF) and AE index data showed that (7) during periods of southward IMF and increased AE activity the observed electric field strengths were enhanced, and in several instances, reversals of the electric field direction occurred at the highest latitudes. These data imply that during such periods a latitudinal belt of strong electric fields, associated with the auroral oval, expanded into the region probed by the radar and that the reversals of the electric field occurred near the poleward edge of this belt (i.e., the boundary of the polar cap). Comparison of the electric fields with optical auroral data from DMSP and all-sky photographs showed that: (8) near a westward trav...