Printed in Great Britain. Pergamon Press plc INTERPLANETARY MAGNETIC FIELD CONTROL OF DAYSIDE AURORAL ACTIVITY AND THE TRANSFER OF MOMENTUM ACROSS THE DAYSIDE MAGNETOPAUSE

• Main Authors: M. Lockwood, P. E. Sandholt, S. W. H. Cowley, T. Oguti
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1989
• Subjects: EISCAT
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.694.7316; http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/1989/62_Lockwoodetal_1989.pdf

Abstract-The orientation of the Interplanetary Magnetic Field (&IF) during transient bursts of iono-spheric flow and aurora1 activity in the dayside aurora1 ionosphere is studied, using data from the EISCAT radar, meridian-scanning photometers, and an all-sky TV camera, in conjunction with simultaneous observations of the interplanetary medium by the IMP-8 satellite. It is found that the ionospheric flow and aurora1 burst events occur regularly (mean repetition period equal to 8.3 + 0.6 min) during an initial period of about 45 min when the IMF is continuously and strongly southward in GSM coordinates, consistent with previous observations of the occurrence of transient dayside aurora1 activity. However, in the subsequent 1.5 h, the IMF was predominantly northward, and only made brief excursions to a southward orientation. During this period, the mean intervai between events increased to 19.2i 1.7 min. If it is assumed that changes in the North-South component of the IMF are aligned with the IMF vector in the ecliptic plane, the deiays can be estimated between such a change impinging upon IMP-8 and the response in the cleft ionosphere within the radar field-of-view. It is found that, to within the accuracy of this computed lag, each transient ionospheric event during the period of predominantly northward IMF can be associated with a brief, isolated southward excursion of the IMF, as observed by IMP-8 From this limited period of data, we therefore suggest that transient momentum exchange between the magnetosheath and the iono-