Measuring electric fields in space is essential for understanding how energy moves between the Sun and Earth. One of the most common tools used for this is called a double probe, which involves small sensors extended from a spacecraft. To make these measurements more accurate, scientists have developed techniques to control how the sensors interact with their surroundings, especially the plasma (charged gas) in space.

However, in recent space missions like Polar, and the Van Allen Probes, scientists noticed unexpected signals—strange oscillations—that seem to be caused by interactions between the sensor electronics and the surrounding plasma. Specifically, it appears that the guard surfaces (metal parts near the sensors that are electrically biased to help stabilize measurements) might be unintentionally creating resonances with the plasma, distorting the E field readings

To better understand this, we created a computer model that simulates how the sensors and guard surfaces behave in different space plasma environments. We also compared these results to real data from the Van Allen Probes and to lab experiments.

Our findings shed light on how these unwanted effects happen, and they could help engineers design better electric field instruments for future space missions—leading to more reliable measurements and better science.