Astronomy reading
Magnetic tension and the growth of a disk disturbance
Start with magnetic tension carrying angular momentum outward. Derive the local channel equations, test mesh and time errors, then inspect the saved fields. The final guide follows a published nonideal simulation study beyond the linear model.
L1 · Concept
Who carries angular momentum through an accretion disk?
Magnetic tension can carry angular momentum outward and draw energy from differential rotation. Follow the feedback in a small growing channel.
L2 · Derivation and worked examples
Four real fields in a rotating patch of a disk
Define coordinates and magnetic velocity units, then derive the four real linear equations from one sine and cosine field pattern.
L2 · Derivation and worked examples
Predict the growth, then follow its energy
Derive the channel growth rate, separate velocity and magnetic stresses, and compare energy gain with shear work in one saved field.
L2 · Derivation and worked examples
Why a vertical mesh changes a linear channel
Derive the centered mesh derivative, read actual spatial errors, and distinguish sampled perturbation fields from their four observed amplitudes.
L2 · Method guide
Checking growth, transport and shear work
Separate spatial and temporal errors, compare stage-stress work with field energy, and identify what the channel divergence check tests.
L3 · Method guide
Check an MRI calculation from its saved fields
Inspect saved MRI channel fields, recover stress and shear work, and separate spatial from temporal error.
L4 · Method guide
Read beyond linear MRI growth
Read a Hall and ambipolar MRI figure, then compare net flux and pressure-normalized transport with linear growth.