Observations of a new class of upstream waves with periods near 3 seconds

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Abstract
We have found a new class of ULF waves with periods near 3 s in the Earth's upstream region by examining the high time resolution magnetic field data from the ISEE spacecraft. These waves are observed in the part of the upstream region which is magnetically connected to the bow shock, but only when the solar wind plasma beta is high (greater than 1). The waves are always right‐handed, nearly circularly polarized in the spacecraft frame. The directions of the wave vectors are in the general direction of the average magnetic field, and the waves are convected downstream in the spacecraft frame. Our study of these waves has shown that they appear to be intrinsically left‐handed ion cyclotron waves in the plasma rest frame.