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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present a 3-D ideal MHD simulation of magnetospheric accretion onto anon-rotating star. The accretion process unfolds with intricate 3-D structuresdriven by various mechanisms. First, the disc develops filaments at themagnetospheric truncation radius ($R_T$) due to magnetic interchangeinstability. These filaments penetrate deep into the magnetosphere, formmultiple accretion columns, and eventually impact the star at $\sim$30$^o$ fromthe poles at nearly the free-fall speed. Over 50% (90%) of accretion occurs onjust 5% (20%) of the stellar surface. Second, the disc region outside $R_T$develops large-scale magnetically dominated bubbles, again due to magneticinterchange instability. These bubbles orbit at a sub-Keplerian speed,persisting for a few orbits while leading to asymmetric mass ejection. The discoutflow is overall weak because of mostly closed field lines. Third,magnetically-supported surface accretion regions appear above the disc,resembling a magnetized disc threaded by net vertical fields, a departure fromtraditional magnetospheric accretion models. Stellar fields are efficientlytransported into the disc region due to above instabilities, contrasting withthe ``X-wind'' model. The accretion rate onto the star remains relativelysteady with a 23% standard deviation. The periodogram reveals variabilityoccurring at around 0.2 times the Keplerian frequency at $R_T$, linked to thelarge-scale magnetic bubbles. The ratio of the spin-up torque to$\dot{M}(GM_*R_T)^{1/2}$ is around 0.8. Finally, after scaling the simulation,we investigate planet migration in the inner protoplanetary disc. The discdriven migration is slow in the MHD turbulent disc beyond $R_T$, whileaerodynamic drag plays a significant role in migration within $R_T$.

A Global 3-D Simulation of Magnetospheric Accretion: I. Magnetically Disrupted Disks and Surface Accretion