Rate of erosion of dayside magnetic flux based on a quantitative study of the dependence of polar cusp latitude on the interplanetary magnetic field
Article first published online: 7 DEC 2012
Copyright 1973 by the American Geophysical Union.
Volume 8, Issue 11, pages 955–961, November 1973
How to Cite
1973), Rate of erosion of dayside magnetic flux based on a quantitative study of the dependence of polar cusp latitude on the interplanetary magnetic field, Radio Sci., 8(11), 955–961, doi:10.1029/RS008i011p00955.(
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Received: 6 AUG 1973
By considering only those periods when the delay time from the interplanetary observing position to the magnetosphere is less than about 5 min, it is found that irrespective of substorm activity: (a) the 45-min average value of interplanetary Bz predicts the latitudes of the poleward and equatorward boundaries of polar cusp electron precipitation with rms errors of 1.34° and 1.16° respectively; (b) both boundaries move equatorward by about 5° as Bz varies from 0 to −6γ, the cusp remaining about 4° wide; (c) the amount of flux added to the polar cap is about 9.2% of the total southward flux impingent on the magnetosphere in the previous 45 min; and (d) as Bz becomes more positive, the equatorward boundary moves only slightly more poleward (½° between Bz = 2γ and Bz = 6γ), while the poleward boundary moves significantly toward higher latitudes, resulting in a cusp approximately 7° wide for Bz = 6γ. This dependence of the width of the cusp on positive Bz suggests that reconnection between the IMF (interplanetary magnetic field) and open geomagnetic field lines (which are southward near the dayside magnetopause) is facilitated when the IMF is northward, allowing deeper penetration of magnetosheath plasma into the high latitude magnetosphere.