New dynamo pattern revealed by solar helical magnetic fields

TL;DR

This study reports the first direct measurement of the mirror asymmetry in solar magnetic fields, revealing new patterns in solar helicity that challenge existing dynamo theories and enhance understanding of magnetic field generation.

Contribution

The paper provides the first observational evidence of persistent hemispheric helicity patterns and their brief inversions, offering new insights into solar and stellar dynamo mechanisms.

Findings

Hemispheric helicity patterns propagate equatorward.

Helicity sign remains consistent across cycles, with brief inversions.

Results challenge existing dynamo models and suggest new theoretical considerations.

Abstract

Previously unobservable mirror asymmetry of the solar magnetic field -- a key ingredient of the dynamo mechanism which is believed to drive the 11-year activity cycle -- has now been measured. This was achieved through systematic monitoring of solar active regions carried out for more than 20 years at observatories in Mees, Huairou, and Mitaka. In this paper we report on detailed analysis of vector magnetic field data, obtained at Huairou Solar Observing Station in China. Electric current helicity (the product of current and magnetic field component in the same direction) was estimated from the data and a latitude-time plot of solar helicity during the last two solar cycles has been produced. We find that like sunspots helicity patterns propagate equatorwards but unlike sunspot polarity helicity in each solar hemisphere does not change sign from cycle to cycle - confirming the theory. There are, however, two significant time-latitudinal domains in each cycle when the sign does briefly invert. Our findings shed new light on stellar and planetary dynamos and has yet to be included in the theory.