According to the Coilcraft MA5532-AE datasheet entitled RFID Transponder Coil https://www.coilcraft.com/en-us/product … hz/ma5532/, the transducer is described as “wound on a plastic base,” making it a multi-turn dipole. The overall coil diameter appears to be nor more than 3.5mm, which is much smaller than one half the wavelength (300m) of 500kHz (600m), making the MA5532-AE a short multi-turn loop dipole. The datasheet mentions that the MA5532-AE was developed for the austriamicrosystems AS3935 Franklin Lightning Sensor IC.
I conclude that the lightning detector antenna is directional. I expect the directional pattern to look something like this:
