Assessment of the Generation of Traveling Ionospheric Disturbances by Solar Terminators

Abstract The generation of traveling ionospheric disturbances (TIDs) near solar terminators has been predicted, and several studies have reported the detection of TIDs associated with sunrise. However, there are also observations that do not show TID signatures at sunrise. We address this issue by investigating false TID detection at sunrise using total electron content (TEC) data from the global navigation satellite system (GNSS) network over the United States and plasma density measurements from the first Republic of China satellite (ROCSAT‐1). The TEC morphology near sunrise, characterized by a rapid TEC increase, creates significant deviations between observed and trend (or filtered) TEC values. The collective pattern of this difference (dTEC) appears as a negative dTEC band aligned with sunrise. While this feature can be interpreted as a signature of large‐scale TIDs (LSTIDs), it may also falsely suggest a high occurrence rate of medium‐scale TIDs (MSTIDs) when dTEC is used as a detection proxy. However, the negative dTEC band at sunrise is not indicative of LSTIDs because the rapid TEC transition at sunrise is caused by photoionization. This interpretation is supported by the detection of a similar dTEC band at sunrise in model outputs that contain no TID information. Furthermore, the distribution of electron density irregularities derived from ROCSAT‐1 showed no evidence of enhanced MSTID activity near sunrise. Therefore, false TID detections near sunrise in GNSS TEC data should not be overlooked.