Ionospheric systematic effects affecting phases for the same four stations of Fig. 5. From top to bottom in the first panel: RS106 (brown), RS508 (green), RS509 (purple), and CS302 (blue). From left to right: clock delays, first order ionospheric delay, and Faraday rotation. The CS has uniformly zero clock delays as its clock is the same as the reference station (CS002). RS508 and RS509 TEC values track each other as the two stations are relatively close by. The TEC unit (TECU) is defined as 10¹⁶ m⁻², which is the order of magnitude typically observed at zenith during the night. The clear correlation between dTEC and dRM (second and third panel) is because differential Faraday rotation is to a large extent caused by the difference in integrated TEC multiplied with the parallel magnetic field. The HBA equivalent is shown in Fig. A.5.