The antisymmetric factor method for magnetic reduction to the pole at low latitudes

• A new method for magnetic reduction to the pole at low latitudes is presented.
• The method is based on modification of the RTP factor in a wavenumber domain.
• It has the advantages of few control parameters, fast and stable RTP.
• It is applicable to RTP of large-scale magnetic data.
• Tests on the synthetic and real data show that the method is robust and effective.

We analyze the characteristics of the wavenumber-domain factor for magnetic reduction to the pole (RTP) at low latitudes, and then propose a new wavenumber-domain method for RTP at low latitudes, herein called the antisymmetric factor method, based on modification of the RTP factor. The method applies the antisymmetric factor in a given scope of directions centered along the magnetic declination to suppress amplification of the RTP factor, stabilizing the RTP. Meanwhile it utilizes the routine RTP factor in other directions to preserve the effective RTP features. The test on the synthetic data demonstrates that the method is robust and effective. Finally, we use the new method, as well as a variable magnetic inclinations algorithm, to perform RTP on the real data of total magnetic intensity anomalies in the South China Sea, and obtain the reliable RTP anomalies.