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We demonstrate that the current helicity observed in solar active regionstraces the magnetic helicity of the large-scale dynamo generated field. We usean advanced 2D mean-field dynamo model with dynamo saturation based on theevolution of the magnetic helicity and algebraic quenching. For comparison, wealso studied a more basic 2D mean-field dynamo model with simple algebraicalpha quenching only. Using these numerical models we obtained butterflydiagrams both for the small-scale current helicity and also for the large-scalemagnetic helicity, and compared them with the butterfly diagram for the currenthelicity in active regions obtained from observations. This comparison showsthat the current helicity of active regions, as estimated by $-{\bf A \cdot B}$evaluated at the depth from which the active region arises, resembles theobservational data much better than the small-scale current helicity calculateddirectly from the helicity evolution equation. Here ${\bf B}$ and ${\bf A}$ arerespectively the dynamo generated mean magnetic field and its vector potential.A theoretical interpretation of these results is given.

Current helicity of active regions as a tracer of large-scale solar magnetic helicity