def calculateLons(initial_submap, curr_submap, Coords):
"""
Calculates where the coordinates should be given a time difference between current and initial
Coords is the Coord = {"lon":(lon0,lonf), "lat":(lat0,latf)} object
"""
import astropy.units as u
from astropy.coordinates import SkyCoord
from sunpy.coordinates import RotatedSunFrame
# Subtract Time of current map to previous map
dinit = initial_submap.date
dcurr = curr_submap.date
dt = dcurr - dinit
startlon0, startlonF = Coords["lon"][0], Coords["lon"][1]
dlon = startlonF - startlon0
startlat0, startlatF = Coords["lat"][0], Coords["lat"][1]
start_coord = SkyCoord(
startlon0,
Coords["lat"][0],
frame="heliographic_stonyhurst",
obstime=dinit,
)
rotated_coord = RotatedSunFrame(base=start_coord, duration=dt.to(
u.second)).transform_to(start_coord.frame)
rotlon0 = rotated_coord.lon
rotlonF = rotated_coord.lon + dlon
rotCoords = {
"lon": (rotlon0, rotlonF),
"lat": (startlat0, startlatF),
} # Latitude is constant
return rotCoords
sidereal_period = 360 * u.deg / sidereal_rotation_rate
print(sidereal_period)
##############################################################################
# We use `~sunpy.coordinates.metaframes.RotatedSunFrame` to rotate the
# meridian by one sidereal period using each of the available
# differential-rotation models. See
# :func:`~sunpy.physics.differential_rotation.diff_rot` for details on each
# model.
rotated_meridian = {}
for model in ['howard', 'snodgrass', 'allen', 'rigid']:
rotated_meridian[model] = SkyCoord(
RotatedSunFrame(base=meridian,
duration=sidereal_period,
rotation_model=model))
##############################################################################
# Finally, we plot the differentially rotated meridians over the map, using
# :meth:`~sunpy.map.GenericMap.draw_quadrangle` to conveniently draw a line
# of constant longitude in the original frame between two endpoints. (One
# could instead use :meth:`astropy.visualization.wcsaxes.WCSAxes.plot_coord`,
# but then ``meridian`` would need to consist of a sequence of many points
# spanning all latitudes between the two poles to render as desired.)
# Note that the "rigid" model appears as the meridian again as expected for a
# rotation of exactly one sidereal period.
plt.figure()
aiamap.plot(clip_interval=(0.5, 99.9) * u.percent)
############################################################################## # First, load an AIA observation and define a coordinate in its coordinate # frame (here, helioprojective Cartesian). The appropriate rate of rotation # is determined from the heliographic latitude of the coordinate. aiamap = sunpy.map.Map(AIA_171_IMAGE) point = SkyCoord(187 * u.arcsec, 283 * u.arcsec, frame=aiamap.coordinate_frame) ############################################################################## # We can differentially rotate this coordinate by using # `~sunpy.coordinates.metaframes.RotatedSunFrame` with an array of observation # times. Let's define a daily cadence for +/- five days. durations = np.concatenate([range(-5, 0), range(1, 6)]) * u.day diffrot_point = RotatedSunFrame(base=point, duration=durations) ############################################################################## # To see what this coordinate looks like in "real" helioprojective # Cartesian coordinates, we can transform it back to the original frame. # Since these coordinates are represented in the original frame, they will not # account for the changing position of the observer over this same time range. transformed_diffrot_point = diffrot_point.transform_to(aiamap.coordinate_frame) print(transformed_diffrot_point) ############################################################################## # Let's plot the original coordinate and the differentially rotated # coordinates on top of the AIA observation. fig = plt.figure()
##############################################################################
# Let's define the output frame to be five days in the future for an observer
# at Earth (i.e., about five degrees offset in heliographic longitude compared
# to the location of AIA in the original observation).
out_time = in_time + 5 * u.day
out_frame = Helioprojective(observer='earth', obstime=out_time)
##############################################################################
# For the reprojection, the definition of the target frame can be
# counter-intuitive. We will be transforming from the original frame to the
# `~sunpy.coordinates.metaframes.RotatedSunFrame` version of the output frame
# with ``rotated_time`` set to the time of the original frame.
rot_frame = RotatedSunFrame(base=out_frame, rotated_time=in_time)
print(rot_frame)
##############################################################################
# Construct a WCS object for the output map with the target
# ``RotatedSunHelioprojective`` frame specified instead of the regular
# `~sunpy.coordinates.frames.Helioprojective` frame.
# If one has an actual ``Map`` object at the desired output
# time (e.g., the actual AIA observation at the output time), one can use the
# WCS object from that ``Map`` object (e.g., ``mymap.wcs``) instead of
# constructing a custom WCS.
out_shape = aiamap.data.shape
out_center = SkyCoord(0 * u.arcsec, 0 * u.arcsec, frame=out_frame)
header = sunpy.map.make_fitswcs_header(out_shape,
out_center,
aiamap = sunpy.map.Map(AIA_171_IMAGE)
fig = plt.figure()
ax = plt.subplot(projection=aiamap)
aiamap.plot(clip_interval=(1., 99.95) * u.percent)
##############################################################################
# Lines of constant longitude prior to differential rotation
# sphinx_gallery_defer_figures
overlay1 = ax.get_coords_overlay('heliographic_stonyhurst')
overlay1[0].set_ticks(spacing=15. * u.deg)
overlay1[1].set_ticks(spacing=90. * u.deg)
overlay1.grid(ls='-', color='white')
##############################################################################
# Differentially rotating the lines of constant longitude by 27 days
# Be aware that the differentially rotated lines are plotted in the
# original coordinate frame, so it doesn't account for any motion of the
# observer over 27 days.
rs_hgs = RotatedSunFrame(base=HeliographicStonyhurst(obstime=aiamap.date),
duration=27 * u.day)
overlay2 = ax.get_coords_overlay(rs_hgs)
overlay2[0].set_ticks(spacing=15. * u.deg)
overlay2[1].set_ticks(spacing=90. * u.deg)
overlay2.grid(ls='-', color='blue')
plt.show()