Relations between the dawn minimum in the equatorial radius of the plasmapause andDst, Kp, and localKat Byrd Station

The equatorial geocentric distance to the plasmapause is known to be sensitive to the level of worldwide magnetic activity, decreasing during periods of increasing magnetic disturbance [Carpenter, 1963, 1966; Taylor et al., 1965]. The purpose of the present note is to clarify this relationship by providing statistics relating the plasmapause position to three different magnetic indices, Dst, Kp, and local K Sit Byrd Station in the auroral zone. Dst, reported on an hourly basis by Sugiura and Hendricks [1966], is based upon observations at a series of stations near the magnetic equator and provides a measure of ring current activity. The well-known 3-hour Kp planetary index draws upon observations in the latitude range 48–63°. Byrd Station, used for local K, lies in the southern auroral zone at about 71°S geomagnetic (L ∼ 7). Eights Station, which with Byrd provided the whistler information on plasmapause position, is located at about 64°S geomagnetic (L ∼ 4), and is about 1 hour ahead of Byrd in magnetic local time.