Speaker
Description
First Name: Ruihui
Last Name: Wang
Affiliation: Beihang University
All Authors: Jie Jiang, Yukun Luo
Abstract: The solar polar magnetic field, a key science objective of the SO/PHI instrument, plays a central role in the solar cycle and solar dynamo processes. The Surface Flux Transport (SFT) model serves as the standard framework for understanding the evolution of the solar surface magnetic field, including the polar field. We will present the first successful continuous simulation of the solar surface magnetic field since 2010, reproducing the evolution of the axial dipole strength, the polar field in the 60°–75° latitude range, and the magnetic butterfly diagram. This achievement is made possible by two key advances. First, we identify active regions from SOHO/MDI and SDO/HMI synoptic magnetograms and assimilate them into the SFT model as flux sources. To avoid contamination from non-newly emerged flux, we remove over-decayed ARs, unipolar regions, and repeated detections of long-lived ARs. These carefully identified ARs are compiled into an open-access database, ARISE. Second, we develop a new SFT code using a spectral method, which inherently ensures that the magnetic field remains divergence-free on the surface. This is particularly important for studying the polar field. Our simulations reproduce the observed magnetic spectra at large spatial scales (spherical harmonic degrees l≤ 60). In addition, we constrained a new meridional flow profile by comparing simulated and HMI-observed mean fields in the 60°–75° latitude range. This profile demonstrates excellent performance in reproducing the observed surface magnetic evolution.