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