diff_rot#

sunpy.physics.differential_rotation.diff_rot(
duration: Unit('s'),
latitude: Unit('deg'),
rot_type='howard',
frame_time='sidereal',
)[source]#

Deprecated since version 6.0: The diff_rot function is deprecated and may be removed in a future version. Use sunpy.sun.models.differential_rotation instead.

This function computes the change in longitude over days in degrees.

Parameters:
  • duration (Quantity) – Number of seconds to rotate over.

  • latitude (Quantity) – heliographic coordinate latitude in Degrees.

  • rot_type (str) – The differential rotation model to use.

    One of:

    howard : Use values from Howard et al. [HHF90]
    snodgrass : Use values from Snodgrass [Sno83]
    allen : Use values from Allen’s Astrophysical Quantities, and simpler equation.
    rigid : Use values from sidereal_rotation_rate.
  • frame_time (str) – One of : 'sidereal' or 'synodic'. Choose ‘type of day’ time reference frame.

Returns:

longitude_delta (Quantity) – The change in longitude over days (units=degrees)

Notes

The rotation rate at a heliographic latitude \(\theta\) is given by

\[A + B \sin^{2} \left (\theta \right ) + C \sin^{4} \left ( \theta \right )\]

where \(A, B, C\) are constants that depend on the model:

Model

A

B

C

Unit

howard

2.894

-0.428

-0.370

microrad/s

snodgrass

2.851

-0.343

-0.474

microrad/s

allen

14.44

-3.0

0

deg/day

rigid

14.1844

0

0

deg/day

1 microrad/s is approximately 4.95 deg/day. See also the comparisons in Beck [Bec00].