Seasonal asymmetry in the broadband ELF electric fields observed by the FAST satellite

► Seasonal asymmetry in the BB ELF electric fields is demonstrated by FAST data. ► Seasonal effect is present in both Alfvénic turbulent E-fields and electrostatic noise. ► Seasonal asymmetry in the Alfvénic turbulence can be explained in quasi-static models. ► Electrostatic noise excited by E-fields of Alfvénic turbulence is season dependent.