English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The large-scale magnetic field in the Sun varies with a period ofapproximately 22 years, although the amplitude of the cycle is subject tolong-term modulation with recurrent phases of significantly reduced magneticactivity. It is believed that a hydromagnetic dynamo is responsible forproducing this large-scale field, although this dynamo process is not wellunderstood.  Within the framework of mean-field dynamo theory, our aim is to investigatehow competing mechanisms for poloidal field regeneration (namely a time delayedBabcock-Leighton surface alpha-effect and an interface-type alpha-effect), canlead to the modulation of magnetic activity in a deep-seated solar dynamomodel.  We solve the standard alpha-omega dynamo equations in one spatial dimension,including source terms corresponding to both of the the competing alpha-effectsin the evolution equation for the poloidal field. This system is solved usingtwo different methods. In addition to solving the one-dimensional partialdifferential equations directly, using numerical techniques, we also use alocal approximation to reduce the governing equations to a set of coupledordinary differential equations (ODEs), which are studied using a combinationof analytical and numerical methods.  In the ODE model, it is straightforward to find parameters such that a seriesof bifurcations can be identified as the time delay is increased, with thedynamo transitioning from periodic states to chaotic states via multiplyperiodic solutions. Similar transitions can be observed in the full model, withthe chaotically modulated solutions exhibiting solar-like behaviour.

Modulated cycles in an illustrative solar dynamo model with competing alpha effects