A Search for Rotation Measure Flare Candidates in Repeating Fast Radio Bursts

Fast radio bursts (FRBs) are millisecond-duration extragalactic radio transients of unknown origin. Rotation measures (RMs) probe their local magnetoionic environments and provide important clues to their nature. While RM variability has been observed in several repeating FRBs, it is typically gradual or stochastic. Recently, observations of FRB 20220529A revealed an abrupt RM excursion followed by rapid recovery on weeklong timescales, termed an “RM flare,” suggesting a potentially distinct form of RM variability associated with localized magnetized plasma. In this work, we perform a systematic search for RM flare candidates in repeating FRBs with multi-epoch RM measurements. Using an iterative Gaussian smoothing method to estimate the baseline and a 3 σ significance threshold for candidate selection, we identify one tentative RM flare candidate in FRB 20121102A and one marginal signal in FRB 20240114A, in addition to the event in FRB 20220529A. Our results suggest that RM flares, if confirmed, may not be rare among repeating FRBs and point to highly dynamic magnetized environments local to the sources. Future high-cadence polarimetric observations, particularly following the discovery of RM excursions, will be essential for further evaluating these candidates and constraining their physical origin.