Phase sorting wave‐particle correlator

Wave‐particle correlations, particularly of Langmuir waves and electrons, have been the subject of significant interest extending back to the 1970s. Often, these correlations have been simply observing modulation of the electrons at the plasma frequency with no phase resolution. The first phase‐resolving correlators were developed at UC Berkeley in the late 1980s and reported by Ergun in the early 1990s. A design is presented which further improves on phase resolution in correlations of Langmuir waves and electrons with phase resolution of 22.5°. In this technique, a phase‐locked loop (PLL) is used to lock onto the wave and subdivide the phase. Electrons are sorted on‐the‐fly as they arrive into the phase bins. Discussed are details of accurate timing, testing, and calibration of this system as well as results from rocket flights in which statistically significant phase correlations have been observed. Key Points Wave‐particle interactions are an essential part of space plasma physics Using a phase‐locked loop (PLL) technique, good phase resolution can be achieved for higher‐frequency waves in the auroral ionosphere Two rocket flights have demonstrated the success of the technique