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 version 6.1. 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. (1990)

snodgrass : Use values from Snodgrass et. al. (1983)

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.

References