The penetration of convection electric fields to the latitude of Millstone Hill (Λ=56°)

Abstract

Incoherent scatter observations of E and F region drifts over Millstone Hill (Λ=56°) were made routinely from May 1976 to November 1977 at monthly intervals. Some 667 hours of data gathered over this 19‐month period has been analyzed to yield the F region polarization electric field in the magnetic south and magnetic east directions. In an effort to determine what part of the observed fields can be attributed to the penetration of auroral convection fields to the latitude of Millstone, these data have been used to construct an analytical model of these two field components having a time of day and Kp dependence (Wand, this issue). To guide the interpretation, mean convection fields also were constructed for Λ=60°, 65°, 70° and 75°, using data gathered between May 1978 and December 1978 from a separate series of experiments (Evans et al., 1979, 1980). The results suggest that, under quiet magnetic conditions, there is no significant penetration of the magnetospheric electric field to the latitude of Millstone at any time of day except possibly for the southward component of the field at night. During magnetically disturbed periods the incremental fields observed over Millstone exhibit all the gross characteristics associated with convection fields seen at higher latitudes. The results also indicate an eastward rotation of the convection pattern of about 4 hours in local time in going from quiet or moderate conditions (Kp ∼ 2+) at Λ=65° to disturbed conditions (Kp=5) at Λ=56°.