ESTIMATING THE BOW SHOCK NORMAL SPEED FROM SINGLE SPACECRAFT OBSERVATIONS OF MAGNETIC-WAVE ACTIVITY

We introduce a reliable method for estimating the speed of the quasi-p erpendicular bow shock from single spacecraft data. It is based on tim ing the passage of the foot and uses magnetic wave activity to detect the upstream boundary of the foot. The frequency range employed is bet ween 20 and 60 Hz as recorded by the AMPTE-IRM fluxgate magnetometer. This new technique has been applied to 33 bow shock crossings. The res ulting velocities are checked against results from the dual-spacecraft method and others employed in the past.