Nonlinear growth of magnetic pulses in the upstream of Earth's bow shock

On 2 April 2002 the four Cluster spacecraft detected two large magnetic pulses in succession in the upstream edge of a density hole or hot flow anomaly upstream of Earth's bow shock. One developed into a nonlinear structure, while the other did not. The development of the pulses is related to the strong enhancement of current flowing in a very narrow regions. We reconstruct the current structure that could produce the nonlinear pulses. We also analyzed electron and ion data obtained from Cluster for those pulses, which shows that field-aligned electron beams might be responsible for the strong enhancement of the current. We will discuss how a particular wave selectively grows in the upstream region of Earth's bow shock.