"""
Common solar physics coordinate systems.
This submodule implements various solar physics coordinate frames for use with
the `astropy.coordinates` module.
"""
import os
import re
import traceback
import numpy as np
import astropy.units as u
from astropy.constants import R_earth
from astropy.coordinates import Attribute, ConvertError, Latitude, Longitude, QuantityAttribute
from astropy.coordinates.baseframe import BaseCoordinateFrame, RepresentationMapping
from astropy.coordinates.representation import (
CartesianDifferential,
CartesianRepresentation,
CylindricalRepresentation,
SphericalDifferential,
SphericalRepresentation,
UnitSphericalRepresentation,
)
from astropy.time import Time
from astropy.utils.data import download_file
from sunpy import log
from sunpy.sun.constants import radius as _RSUN
from sunpy.time.time import _variables_for_parse_time_docstring
from sunpy.util.decorators import add_common_docstring, deprecated, sunpycontextmanager
from sunpy.util.exceptions import warn_user
from .frameattributes import ObserverCoordinateAttribute, TimeFrameAttributeSunPy
_J2000 = Time('J2000.0', scale='tt')
__all__ = ['SunPyBaseCoordinateFrame', 'BaseHeliographic', 'BaseMagnetic',
'HeliographicStonyhurst', 'HeliographicCarrington',
'Heliocentric', 'Helioprojective',
'HeliocentricEarthEcliptic', 'GeocentricSolarEcliptic',
'HeliocentricInertial', 'GeocentricEarthEquatorial',
'Geomagnetic', 'SolarMagnetic', 'GeocentricSolarMagnetospheric']
def _frame_parameters():
"""
Returns formatting dictionary to use with add_common_docstring to populate frame docstrings
"""
ret = {}
# Each text block is missing the first indent because it already exists in the frame docstring
ret['data'] = ("data : `~astropy.coordinates.BaseRepresentation` or ``None``\n"
" A representation object or ``None`` to have no data\n"
" (or use the coordinate component arguments, see below).")
ret['common'] = (f"obstime : {_variables_for_parse_time_docstring()['parse_time_types']}\n"
" The time of the observation. This is used to determine the\n"
" position of solar-system bodies (e.g., the Sun and the Earth) as\n"
" needed to define the origin and orientation of the frame.\n"
" representation_type : `~astropy.coordinates.BaseRepresentation`, str, optional\n"
" A representation class or string name of a representation class.\n"
" This may change the valid coordinate component arguments from the\n"
" defaults (see above). For example, passing\n"
" ``representation_type='cartesian'`` will make the frame expect\n"
" Cartesian coordinate component arguments (typically, ``x``, ``y``,\n"
" and ``z``).\n"
" copy : bool, optional\n"
" If `True` (default), make copies of the input coordinate arrays.")
ret['lonlat'] = ("lon : `~astropy.coordinates.Angle` or `~astropy.units.Quantity`, optional\n"
" The longitude coordinate for this object (``lat`` must also be\n"
" given and ``data`` must be ``None``).\n"
" Not needed if ``data`` is given.\n"
" lat : `~astropy.coordinates.Angle` or `~astropy.units.Quantity`, optional\n"
" The latitude coordinate for this object (``lon`` must also be\n"
" given and ``data`` must be ``None``).\n"
" Not needed if ``data`` is given.")
ret['radius'] = ("radius : `~astropy.units.Quantity`, optional\n"
" The radial distance coordinate from Sun center for this object.\n"
" Defaults to the radius of the Sun. Not needed if ``data`` is given.")
ret['distance_sun'] = ("distance : `~astropy.units.Quantity`, optional\n"
" The distance coordinate from Sun center for this object.\n"
" Not needed if ``data`` is given.")
ret['distance_earth'] = ("distance : `~astropy.units.Quantity`, optional\n"
" The distance coordinate from Earth center for this object.\n"
" Not needed if ``data`` is given.")
ret['xyz'] = ("x : `~astropy.units.Quantity`, optional\n"
" X-axis coordinate for this object. Not needed if ``data`` is given.\n"
" y : `~astropy.units.Quantity`, optional\n"
" Y-axis coordinate for this object. Not needed if ``data`` is given.\n"
" z : `~astropy.units.Quantity`, optional\n"
" Z-axis coordinate for this object. Not needed if ``data`` is given.")
ret['observer'] = ("observer : `~sunpy.coordinates.frames.HeliographicStonyhurst`, str\n"
" The location of the observer. If a string is provided,\n"
" it must be a solar system body that can be parsed by\n"
" `~sunpy.coordinates.ephemeris.get_body_heliographic_stonyhurst`\n"
" at the time ``obstime``. Defaults to Earth center.")
ret['rsun'] = ("rsun : `~astropy.units.Quantity`\n"
" The radius of the Sun in length units. Used to convert a 2D\n"
" coordinate (i.e., no ``radius`` component) to a 3D coordinate by\n"
" assuming that the coordinate is on the surface of the Sun. Defaults\n"
" to the photospheric radius as defined in `sunpy.sun.constants`.")
ret['equinox'] = (f"equinox : {_variables_for_parse_time_docstring()['parse_time_types']}\n"
" The date for the mean vernal equinox.\n"
" Defaults to the J2000.0 equinox.")
ret['magnetic_model'] = ("magnetic_model : `str`\n"
" The IGRF model to use for determining the orientation of\n"
" Earth's magnetic dipole pole. The supported options are\n"
" ``'igrf13'`` (default), ``'igrf12'``, ``'igrf11'``, and\n"
" ``'igrf10'``.")
ret['igrf_reference'] = ("* `International Geomagnetic Reference Field (IGRF) "
"<https://www.ngdc.noaa.gov/IAGA/vmod/igrf.html>`__")
return ret
[docs]
class SunPyBaseCoordinateFrame(BaseCoordinateFrame):
"""
Base class for sunpy coordinate frames.
This class is not intended to be used directly and has no transformations defined.
* Defines the frame attribute ``obstime`` for observation time.
* Defines a default wrap angle of 180 degrees for longitude in spherical coordinates,
which can be overridden via the class variable ``_wrap_angle``.
* Inject a nice way of representing the object which the coordinate represents.
"""
obstime = TimeFrameAttributeSunPy()
default_representation = SphericalRepresentation
default_differential = SphericalDifferential
frame_specific_representation_info = {
SphericalDifferential: [RepresentationMapping('d_lon', 'd_lon', u.arcsec/u.s),
RepresentationMapping('d_lat', 'd_lat', u.arcsec/u.s),
RepresentationMapping('d_distance', 'd_distance', u.km/u.s)],
}
_wrap_angle = 180*u.deg # for longitude in spherical coordinates
def __init__(self, *args, **kwargs):
self.object_name = None
# If wrap_longitude=False is passed in, do not impose a specific wrap angle for the frame
if not kwargs.pop('wrap_longitude', True):
self._wrap_angle = None
# If obstime is not provided but observer has an obstime, use that as the obstime
if 'obstime' not in kwargs and 'observer' in kwargs and getattr(kwargs['observer'], 'obstime', None) is not None:
kwargs['obstime'] = kwargs['observer'].obstime
super().__init__(*args, **kwargs)
# If obstime is specified, treat the default observer (None) as explicitly set
if self.obstime is not None and self.is_frame_attr_default('observer'):
self._attr_names_with_defaults.remove('observer')
return
[docs]
def represent_as(self, base, s='base', in_frame_units=False):
data = super().represent_as(base, s, in_frame_units=in_frame_units)
# If a frame wrap angle is set, use that wrap angle for any spherical representations.
if self._wrap_angle is not None and \
isinstance(data, UnitSphericalRepresentation | SphericalRepresentation):
data.lon.wrap_angle = self._wrap_angle
return data
def __str__(self):
# We override this here so that when you print a SkyCoord it shows the
# observer as the string and not the whole massive coordinate.
if getattr(self, "object_name", None):
return f"<{self.__class__.__name__} Coordinate for '{self.object_name}'>"
else:
return super().__str__()
@property
def _is_2d(self):
return (self._data is not None and self._data.norm().unit is u.one
and u.allclose(self._data.norm(), 1*u.one))
[docs]
class BaseHeliographic(SunPyBaseCoordinateFrame):
"""
Base class for HeliographicCarrington (HGC) and HeliographicStonyhurst (HGS) frames.
This class is not intended to be used directly and has no transformations defined.
"""
frame_specific_representation_info = {
SphericalRepresentation: [RepresentationMapping('lon', 'lon', u.deg),
RepresentationMapping('lat', 'lat', u.deg),
RepresentationMapping('distance', 'radius', None)],
SphericalDifferential: [RepresentationMapping('d_lon', 'd_lon', u.arcsec/u.s),
RepresentationMapping('d_lat', 'd_lat', u.arcsec/u.s),
RepresentationMapping('d_distance', 'd_radius', u.km/u.s)],
}
rsun = QuantityAttribute(default=_RSUN, unit=u.km)
[docs]
def make_3d(self):
"""
Returns a fully 3D coordinate based on this coordinate.
If this coordinate is only 2D (i.e., no ``radius`` component) or is a
unit vector (i.e., the norm of the coordinate is unity), a new
coordinate is created that corresponds to the surface of the Sun.
That is, the 3D coordinate will retain the ``lon`` and ``lat``, and
``radius`` will be set to the frame's ``rsun`` frame attribute.
If this coordinate is already fully 3D, it is directly returned, even
if it does not lie on the surface of the Sun.
Returns
-------
frame : `~sunpy.coordinates.frames.BaseHeliographic`
The fully 3D coordinate
"""
if self._is_2d:
return self.realize_frame(self._data * self.rsun)
# The coordinate is already 3D
return self
[docs]
@add_common_docstring(**_frame_parameters())
class HeliographicStonyhurst(BaseHeliographic):
"""
A coordinate or frame in the Stonyhurst Heliographic (HGS) system.
- The origin is the center of the Sun.
- The Z-axis (+90 degrees latitude) is aligned with the Sun's north pole.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the projection of
the Sun-Earth line onto the Sun's equatorial plane.
This system is also know as the Heliocentric Earth Equatorial (HEEQ) system when
represented using Cartesian components.
A new instance can be created using the following signatures
(note that if supplied, ``obstime`` and ``representation_type`` must be
keyword arguments)::
HeliographicStonyhurst(lon, lat, obstime=obstime)
HeliographicStonyhurst(lon, lat, radius, obstime=obstime)
HeliographicStonyhurst(x, y, z, representation_type='cartesian', obstime=obstime)
Parameters
----------
{data}
{lonlat}
{radius}
{rsun}
{common}
Examples
--------
>>> from astropy.coordinates import SkyCoord
>>> import sunpy.coordinates
>>> import astropy.units as u
>>> sc = SkyCoord(1*u.deg, 1*u.deg, 2*u.km,
... frame="heliographic_stonyhurst",
... obstime="2010/01/01T00:00:45")
>>> sc
<SkyCoord (HeliographicStonyhurst: obstime=2010-01-01T00:00:45.000, rsun=695700.0 km): (lon, lat, radius) in (deg, deg, km)
(1., 1., 2.)>
>>> sc.frame
<HeliographicStonyhurst Coordinate (obstime=2010-01-01T00:00:45.000, rsun=695700.0 km): (lon, lat, radius) in (deg, deg, km)
(1., 1., 2.)>
>>> sc = SkyCoord(HeliographicStonyhurst(-10*u.deg, 2*u.deg))
>>> sc
<SkyCoord (HeliographicStonyhurst: obstime=None, rsun=695700.0 km): (lon, lat) in deg
(-10., 2.)>
>>> sc = SkyCoord(CartesianRepresentation(0*u.km, 45*u.km, 2*u.km),
... obstime="2011/01/05T00:00:50",
... frame="heliographic_stonyhurst")
>>> sc
<SkyCoord (HeliographicStonyhurst: obstime=2011-01-05T00:00:50.000, rsun=695700.0 km): (lon, lat, radius) in (deg, deg, km)
(90., 2.54480438, 45.04442252)>
"""
name = "heliographic_stonyhurst"
def _apply_diffrot(self, duration, rotation_model):
oldrepr = self.spherical
from sunpy.sun.models import differential_rotation
log.debug(f"Applying {duration} of solar rotation")
newlon = oldrepr.lon + differential_rotation(duration,
oldrepr.lat,
model=rotation_model,
frame_time='sidereal')
newrepr = SphericalRepresentation(newlon, oldrepr.lat, oldrepr.distance)
return self.realize_frame(newrepr)
[docs]
@add_common_docstring(**_frame_parameters())
class HeliographicCarrington(BaseHeliographic):
"""
A coordinate or frame in the Carrington Heliographic (HGC) system.
- The origin is the center of the Sun.
- The Z-axis (+90 degrees latitude) is aligned with the Sun's north pole.
- The X-axis and Y-axis rotate with a period of 25.38 days.
This system differs from Stonyhurst Heliographic (HGS) in its definition of longitude. This
longitude is an "apparent" longitude because it takes into account the time it takes for light
to travel from the Sun's surface to the observer (see :ref:`sunpy-topic-guide-coordinates-carrington`).
Thus, the observer needs to be specified to be able to transform to any other coordinate frame.
A new instance can be created using the following signatures
(note that if supplied, ``obstime`` and ``observer`` must be a keyword argument)::
HeliographicCarrington(lon, lat, obstime=obstime, observer=observer)
HeliographicCarrington(lon, lat, radius, obstime=obstime, observer=observer)
If you want to define the location in HGC such that the observer for the coordinate frame is
the same as that location (e.g., the location of an observatory in its corresponding HGC
frame), use ``observer='self'``::
HeliographicCarrington(lon, lat, radius, obstime=obstime, observer='self')
Parameters
----------
{data}
{lonlat}
{radius}
{observer}
{rsun}
{common}
Examples
--------
>>> from astropy.coordinates import SkyCoord
>>> import sunpy.coordinates
>>> import astropy.units as u
>>> sc = SkyCoord(1*u.deg, 2*u.deg, 3*u.km,
... frame="heliographic_carrington",
... observer="earth",
... obstime="2010/01/01T00:00:30")
>>> sc
<SkyCoord (HeliographicCarrington: obstime=2010-01-01T00:00:30.000, rsun=695700.0 km, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (lon, lat, radius) in (deg, deg, km)
(1., 2., 3.)>
>>> sc = SkyCoord([1,2,3]*u.deg, [4,5,6]*u.deg, [5,6,7]*u.km,
... obstime="2010/01/01T00:00:45",
... observer="self",
... frame="heliographic_carrington")
>>> sc
<SkyCoord (HeliographicCarrington: obstime=2010-01-01T00:00:45.000, rsun=695700.0 km, observer=self): (lon, lat, radius) in (deg, deg, km)
[(1., 4., 5.), (2., 5., 6.), (3., 6., 7.)]>
>>> sc = SkyCoord(CartesianRepresentation(0*u.km, 45*u.km, 2*u.km),
... obstime="2011/01/05T00:00:50",
... frame="heliographic_carrington")
>>> sc
<SkyCoord (HeliographicCarrington: obstime=2011-01-05T00:00:50.000, rsun=695700.0 km, observer=None): (lon, lat, radius) in (deg, deg, km)
(90., 2.54480438, 45.04442252)>
"""
name = "heliographic_carrington"
_wrap_angle = 360*u.deg
observer = ObserverCoordinateAttribute(HeliographicStonyhurst)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
if not isinstance(self.observer, BaseCoordinateFrame) and self.observer == 'self' and self._is_2d:
raise ValueError("Full 3D coordinate (including radius) must be specified "
"when observer='self'.")
[docs]
@add_common_docstring(**_frame_parameters())
class Heliocentric(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Heliocentric system, which is observer-based.
- The origin is the center of the Sun.
- The Z-axis is aligned with the Sun-observer line.
- The Y-axis is aligned with the component of the vector to the Sun's north pole that is
perpendicular to the Z-axis.
This frame defaults to a Cartesian component representation, which is known as Heliocentric
Cartesian (HCC). This frame can also be represented using cylindrical components, where
where ``rho`` is the impact parameter and ``psi`` is the position angle.
``psi`` is measured relative to the west limb, rather than solar north, so is shifted
by 90 degrees compared to the convention of the Heliocentric Radial (HCR) system.
A new instance can be created using the following signatures
(note that if supplied, ``obstime``, ``observer``, and ``representation_type`` must be
keyword arguments)::
Heliocentric(x, y, z, obstime=obstime, observer=observer)
Heliocentric(rho, psi, z, representation_type='cylindrical', obstime=obstime, observer=observer)
Parameters
----------
{data}
{xyz}
{observer}
{common}
Examples
--------
>>> from astropy.coordinates import SkyCoord, CartesianRepresentation
>>> import sunpy.coordinates
>>> import astropy.units as u
>>> sc = SkyCoord(CartesianRepresentation(10*u.km, 1*u.km, 2*u.km),
... obstime="2011/01/05T00:00:50", observer="earth", frame="heliocentric")
>>> sc
<SkyCoord (Heliocentric: obstime=2011-01-05T00:00:50.000, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (x, y, z) in km
(10., 1., 2.)>
>>> sc = SkyCoord([1,2]*u.km, [3,4]*u.m, [5,6]*u.cm,
... obstime="2011/01/01T00:00:54", observer="earth", frame="heliocentric")
>>> sc
<SkyCoord (Heliocentric: obstime=2011-01-01T00:00:54.000, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (x, y, z) in (km, m, cm)
[(1., 3., 5.), (2., 4., 6.)]>
>>> sc = SkyCoord(CylindricalRepresentation(10*u.km, 60*u.deg, 10*u.km),
... obstime="2011/01/05T00:00:50", observer="earth", frame="heliocentric")
>>> sc
<SkyCoord (Heliocentric: obstime=2011-01-05T00:00:50.000, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (x, y, z) in km
(5., 8.66025404, 10.)>
"""
default_representation = CartesianRepresentation
default_differential = CartesianDifferential
frame_specific_representation_info = {
CylindricalRepresentation: [RepresentationMapping('phi', 'psi', u.deg)]
}
observer = ObserverCoordinateAttribute(HeliographicStonyhurst)
[docs]
def represent_as(self, base, s='base', in_frame_units=False):
data = super().represent_as(base, s, in_frame_units=in_frame_units)
# For cylindrical representations, wrap the `psi` component (natively `phi`) at 360 deg
if isinstance(data, CylindricalRepresentation):
data.phi.wrap_at(360*u.deg, inplace=True)
return data
[docs]
@add_common_docstring(**_frame_parameters())
class Helioprojective(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Helioprojective Cartesian (HPC) system, which is observer-based.
- The origin is the location of the observer.
- ``Tx`` (aka "theta_x") is the angle relative to the plane containing the Sun-observer line
and the Sun's rotation axis, with positive values in the direction of the Sun's west limb.
- ``Ty`` (aka "theta_y") is the angle relative to the Sun's equatorial plane, with positive
values in the direction of the Sun's north pole.
- ``distance`` is the Sun-observer distance.
This system is frequently used in a projective form without ``distance`` specified. For
observations looking very close to the center of the Sun, where the small-angle approximation
is appropriate, ``Tx`` and ``Ty`` can be approximated as Cartesian components.
A new instance can be created using the following signatures
(note that if supplied, ``obstime`` and ``observer`` must be keyword arguments)::
Helioprojective(Tx, Ty, obstime=obstime, observer=observer)
Helioprojective(Tx, Ty, distance, obstime=obstime, observer=observer)
Parameters
----------
{data}
Tx : `~astropy.coordinates.Angle` or `~astropy.units.Quantity`
The theta_x coordinate for this object. Not needed if ``data`` is given.
Ty : `~astropy.coordinates.Angle` or `~astropy.units.Quantity`
The theta_y coordinate for this object. Not needed if ``data`` is given.
distance : `~astropy.units.Quantity`
The distance coordinate from the observer for this object.
Not needed if ``data`` is given.
{observer}
{rsun}
{common}
Examples
--------
>>> from astropy.coordinates import SkyCoord
>>> import sunpy.coordinates
>>> import astropy.units as u
>>> sc = SkyCoord(0*u.deg, 0*u.deg, 5*u.km,
... obstime="2010/01/01T00:00:00", observer="earth", frame="helioprojective")
>>> sc
<SkyCoord (Helioprojective: obstime=2010-01-01T00:00:00.000, rsun=695700.0 km, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (Tx, Ty, distance) in (arcsec, arcsec, km)
(0., 0., 5.)>
>>> sc = SkyCoord(0*u.deg, 0*u.deg,
... obstime="2010/01/01T00:00:00", observer="earth", frame="helioprojective")
>>> sc
<SkyCoord (Helioprojective: obstime=2010-01-01T00:00:00.000, rsun=695700.0 km, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (Tx, Ty) in arcsec
(0., 0.)>
>>> sc = SkyCoord(CartesianRepresentation(1*u.AU, 1e5*u.km, -2e5*u.km),
... obstime="2011/01/05T00:00:50", observer="earth", frame="helioprojective")
>>> sc
<SkyCoord (Helioprojective: obstime=2011-01-05T00:00:50.000, rsun=695700.0 km, observer=<HeliographicStonyhurst Coordinate for 'earth'>): (Tx, Ty, distance) in (arcsec, arcsec, AU)
(137.87948623, -275.75878762, 1.00000112)>
"""
frame_specific_representation_info = {
SphericalRepresentation: [RepresentationMapping('lon', 'Tx', u.arcsec),
RepresentationMapping('lat', 'Ty', u.arcsec),
RepresentationMapping('distance', 'distance', None)],
SphericalDifferential: [RepresentationMapping('d_lon', 'd_Tx', u.arcsec/u.s),
RepresentationMapping('d_lat', 'd_Ty', u.arcsec/u.s),
RepresentationMapping('d_distance', 'd_distance', u.km/u.s)],
UnitSphericalRepresentation: [RepresentationMapping('lon', 'Tx', u.arcsec),
RepresentationMapping('lat', 'Ty', u.arcsec)],
}
rsun = QuantityAttribute(default=_RSUN, unit=u.km)
observer = ObserverCoordinateAttribute(HeliographicStonyhurst)
@property
def angular_radius(self):
"""
Angular radius of the Sun as seen by the observer.
The ``rsun`` frame attribute is the radius of the Sun in length units.
The tangent vector from the observer to the edge of the Sun forms a
right-angle triangle with the radius of the Sun as the far side and the
Sun-observer distance as the hypotenuse. Thus, the sine of the angular
radius of the Sun is ratio of these two distances.
"""
from sunpy.coordinates.sun import _angular_radius # avoiding a circular import
if not isinstance(self.observer, HeliographicStonyhurst):
if self.observer is None:
raise ValueError("The observer must be defined, not `None`.")
raise ValueError("The observer must be fully defined by specifying `obstime`.")
return _angular_radius(self.rsun, self.observer.radius)
[docs]
def make_3d(self):
"""
This method calculates the third coordinate of the Helioprojective
frame. It assumes that the coordinate point is on the surface of the Sun.
If a point in the frame is off limb then NaN will be returned.
Returns
-------
new_frame : `~sunpy.coordinates.frames.Helioprojective`
A new frame instance with all the attributes of the original but
now with a third coordinate.
"""
# Skip if we already are 3D
if not self._is_2d:
return self
if not isinstance(self.observer, BaseCoordinateFrame):
raise ConvertError("Cannot calculate distance to the Sun "
f"for observer '{self.observer}' "
"without `obstime` being specified.")
rep = self.represent_as(UnitSphericalRepresentation)
lat, lon = rep.lat, rep.lon
# Check for the use of floats with lower precision than the native Python float
if not set([lon.dtype.type, lat.dtype.type]).issubset([float, np.float64, np.longdouble]):
warn_user("The Helioprojective component values appear to be lower "
"precision than the native Python float: "
f"Tx is {lon.dtype.name}, and Ty is {lat.dtype.name}. "
"To minimize precision loss, you may want to cast the values to "
"`float` or `numpy.float64` via the NumPy method `.astype()`.")
# Calculate the distance to the surface of the Sun using the law of cosines
cos_alpha = np.cos(lat) * np.cos(lon)
c = self.observer.radius**2 - self.rsun**2
b = -2 * self.observer.radius * cos_alpha
# Ignore sqrt of NaNs
with np.errstate(invalid='ignore'):
d = ((-1*b) - np.sqrt(b**2 - 4*c)) / 2 # use the "near" solution
if self._assumed_screen:
d_screen = self._assumed_screen.calculate_distance(self)
d = np.fmin(d, d_screen) if self._assumed_screen.only_off_disk else d_screen
# This warning can be triggered in specific draw calls when plt.show() is called
# we can not easily prevent this, so we check the specific function is being called
# within the stack trace.
stack_trace = traceback.format_stack()
matching_string = 'wcsaxes.*(_draw_grid|_update_ticks)'
bypass = any([re.search(matching_string, string) for string in stack_trace])
if not bypass and np.all(np.isnan(d)) and np.any(np.isfinite(cos_alpha)):
warn_user("The conversion of these 2D helioprojective coordinates to 3D is all NaNs "
"because off-disk coordinates need an additional assumption to be mapped to "
"calculate distance from the observer. Consider using the context manager "
"`SphericalScreen()`.")
return self.realize_frame(SphericalRepresentation(lon=lon,
lat=lat,
distance=d))
[docs]
@u.quantity_input
def is_visible(self, *, tolerance: u.m = 1*u.m):
"""
Returns whether the coordinate is on the visible side of the Sun.
A coordinate is visible if it can been seen from the observer (the ``observer``
frame attribute) assuming that the Sun is an opaque sphere with a fixed radius
(the ``rsun`` frame attribute). The visible side of the Sun is always smaller
than a full hemisphere.
Parameters
----------
tolerance : `~astropy.units.Quantity`
The depth below the surface of the Sun that should be treated as
transparent.
Notes
-----
If the coordinate is 2D, it is automatically deemed visible. A 2D coordinate
describes a look direction from the observer, who would simply see whatever is
in "front", and thus cannot correspond to a point hidden from the observer.
The ``tolerance`` parameter accommodates situations where the limitations of
numerical precision would falsely conclude that a coordinate is not visible.
For example, a coordinate that is expressly created to be on the solar surface
may be calculated to be slightly below the surface, and hence not visible if
there is no tolerance. However, a consequence of the ``tolerance`` parameter
is that a coordinate that is formally on the far side of the Sun but is
extremely close to the solar limb can be evaluated as visible. With the
default ``tolerance`` value of 1 meter, a coordinate on the surface of the Sun
can be up to 11 arcseconds of heliographic longitude past the solar limb and
still be evaluated as visible.
Examples
--------
>>> import numpy as np
>>> import astropy.units as u
>>> from astropy.coordinates import SkyCoord
>>> from sunpy.coordinates import HeliographicStonyhurst, Helioprojective
>>> hpc_frame = Helioprojective(observer='earth', obstime='2023-08-03')
>>> in_front = SkyCoord(0*u.arcsec, 0*u.arcsec, 0.5*u.AU, frame=hpc_frame)
>>> print(in_front.is_visible())
True
>>> behind = SkyCoord(0*u.arcsec, 0*u.arcsec, 1.5*u.AU, frame=hpc_frame)
>>> print(behind.is_visible())
False
>>> hgs_array = SkyCoord(np.arange(-180, 180, 60)*u.deg, [0]*6*u.deg,
... frame='heliographic_stonyhurst', obstime='2023-08-03')
>>> print(hgs_array)
<SkyCoord (HeliographicStonyhurst: obstime=2023-08-03T00:00:00.000, rsun=695700.0 km): (lon, lat) in deg
[(-180., 0.), (-120., 0.), ( -60., 0.), ( 0., 0.), ( 60., 0.),
( 120., 0.)]>
>>> print(hgs_array.transform_to(hpc_frame).is_visible())
[False False True True True False]
"""
# If the coordinate is 2D, it must be visible
if self._is_2d:
return np.ones_like(self.data, dtype=bool)
# Use a slightly smaller solar radius to accommodate numerical precision
solar_radius = self.rsun - tolerance
data = self.cartesian
data_to_sun = self.observer.radius * CartesianRepresentation(1, 0, 0) - data
# When representing the helioprojective point as true Cartesian, the X value is the
# distance from the observer to the point in the sunward direction
is_behind_observer = data.x < 0
# When comparing heliocentric angles, we compare the sine values and hence avoid calling arcsin()
is_beyond_limb = np.sqrt(data.y **2 + data.z **2) / data.norm() > solar_radius / self.observer.radius
is_above_surface = data_to_sun.norm() >= solar_radius
is_on_near_side = data.dot(data_to_sun) >= 0
return is_behind_observer | is_beyond_limb | (is_on_near_side & is_above_surface)
_assumed_screen = None
[docs]
@classmethod
@sunpycontextmanager
@deprecated('6.0', alternative='sunpy.coordinates.screens.SphericalScreen')
def assume_spherical_screen(cls, center, only_off_disk=False, *, radius=None):
try:
old_assumed_screen = cls._assumed_screen # nominally None
from sunpy.coordinates import SphericalScreen
sph_screen = SphericalScreen(center, radius=radius, only_off_disk=only_off_disk)
cls._assumed_screen = sph_screen
yield
finally:
cls._assumed_screen = old_assumed_screen
[docs]
@add_common_docstring(**_frame_parameters())
class HeliocentricEarthEcliptic(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Heliocentric Earth Ecliptic (HEE) system.
- The origin is the center of the Sun.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the Sun-Earth line.
- The Z-axis (+90 degrees latitude) is aligned with the component perpendicular to the X-axis
of the mean ecliptic pole at the observation time.
Parameters
----------
{data}
{lonlat}
{distance_sun}
{common}
"""
[docs]
@add_common_docstring(**_frame_parameters())
class GeocentricSolarEcliptic(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Geocentric Solar Ecliptic (GSE) system.
- The origin is the center of the Earth.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the Earth-Sun line.
- The Z-axis (+90 degrees latitude) is aligned with the component perpendicular to the X-axis
of the mean ecliptic pole at the observation time.
Parameters
----------
{data}
{lonlat}
{distance_earth}
{common}
Notes
-----
Aberration due to Earth motion is not included.
"""
[docs]
@add_common_docstring(**_frame_parameters())
class HeliocentricInertial(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Heliocentric Inertial (HCI) system.
- The origin is the center of the Sun.
- The Z-axis (+90 degrees latitude) is aligned with the Sun's north pole.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the solar ascending
node on the ecliptic (mean J2000.0).
Parameters
----------
{data}
{lonlat}
{distance_sun}
{common}
Notes
-----
The solar ascending node on the ecliptic lies on the intersection of the solar equatorial
plane with the ecliptic plane, not on the intersection of the celestial equatorial plane with
the ecliptic plane.
"""
[docs]
@add_common_docstring(**_frame_parameters())
class GeocentricEarthEquatorial(SunPyBaseCoordinateFrame):
"""
A coordinate or frame in the Geocentric Earth Equatorial (GEI) system.
- The origin is the center of the Earth.
- The Z-axis (+90 degrees latitude) is aligned with the Earth's north pole.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the mean (not true)
vernal equinox.
Parameters
----------
{data}
{lonlat}
{distance_earth}
{equinox}
{common}
Notes
-----
Aberration due to Earth motion is not included.
"""
equinox = TimeFrameAttributeSunPy(default=_J2000)
[docs]
class BaseMagnetic(SunPyBaseCoordinateFrame):
"""
Base class for frames that rely on the Earth's magnetic model (MAG, SM, and GSM).
This class is not intended to be used directly and has no transformations defined.
"""
magnetic_model = Attribute(default='igrf13')
@property
def _igrf_file(self):
if not self.magnetic_model.startswith("igrf"):
raise ValueError
# First look if the file is bundled in package
local_file = os.path.join(os.path.dirname(__file__), "data",
f"{self.magnetic_model}coeffs.txt")
if os.path.exists(local_file):
return local_file
# Otherwise download the file and cache it
return download_file("https://www.ngdc.noaa.gov/IAGA/vmod/coeffs/"
f"{self.magnetic_model}coeffs.txt", cache=True)
@property
def _lowest_igrf_coeffs(self):
with open(self._igrf_file) as f:
while not (line := f.readline()).startswith('g/h'):
pass
years = list(map(float, line.split()[3:-1]))
g10s = list(map(float, f.readline().split()[3:]))
g11s = list(map(float, f.readline().split()[3:]))
h11s = list(map(float, f.readline().split()[3:]))
decimalyear = self.obstime.utc.decimalyear
if decimalyear < 1900.0:
raise ValueError
if decimalyear <= years[-1]:
# Use piecewise linear interpolation before the last year
g10 = np.interp(decimalyear, years, g10s[:-1])
g11 = np.interp(decimalyear, years, g11s[:-1])
h11 = np.interp(decimalyear, years, h11s[:-1])
else:
# Use secular variation beyond the last year
g10 = g10s[-2] + (decimalyear - years[-1]) * g10s[-1]
g11 = g11s[-2] + (decimalyear - years[-1]) * g11s[-1]
h11 = h11s[-2] + (decimalyear - years[-1]) * h11s[-1]
return g10, g11, h11
@add_common_docstring(**_frame_parameters())
@property
def dipole_lonlat(self):
"""
The geographic longitude/latitude of the Earth's magnetic north pole.
This position is calculated from the first three coefficients of the selected
IGRF model per Franz & Harper (2002). The small offset between dipole center
and Earth center is ignored.
References
----------
{igrf_reference}
"""
g10, g11, h11 = self._lowest_igrf_coeffs
# Intentionally use arctan() instead of arctan2() to get angles in specific quadrants
lon = (np.arctan(h11 / g11) << u.rad).to(u.deg)
lat = 90*u.deg - np.arctan((g11 * np.cos(lon) + h11 * np.sin(lon)) / g10)
return Longitude(lon, wrap_angle=180*u.deg), Latitude(lat)
@add_common_docstring(**_frame_parameters())
@property
def dipole_moment(self):
"""
The Earth's dipole moment.
The moment is calculated from the first three coefficients of the selected
IGRF model per Franz & Harper (2002).
References
----------
{igrf_reference}
"""
g10, g11, h11 = self._lowest_igrf_coeffs
moment = np.sqrt(g10**2 + g11**2 + h11**2) * R_earth**3
return moment
[docs]
@add_common_docstring(**_frame_parameters())
class Geomagnetic(BaseMagnetic):
"""
A coordinate or frame in the Geomagnetic (MAG) system.
- The origin is the center of the Earth.
- The Z-axis (+90 degrees latitude) is aligned with the Earth's magnetic north
pole.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the
component of the Earth's geographic north pole that is perpendicular to the
Z-axis.
Parameters
----------
{data}
{lonlat}
{distance_earth}
{magnetic_model}
{common}
Notes
-----
The position of Earth's magnetic north pole is calculated from the first three
coefficients of the selected IGRF model per Franz & Harper (2002). The small
offset between dipole center and Earth center is ignored.
References
----------
{igrf_reference}
"""
[docs]
@add_common_docstring(**_frame_parameters())
class SolarMagnetic(BaseMagnetic):
"""
A coordinate or frame in the Solar Magnetic (SM) system.
- The origin is the center of the Earth.
- The Z-axis (+90 degrees latitude) is aligned with the Earth's magnetic north
pole.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the
component of the Earth-Sun line that is perpendicular to the Z-axis.
Parameters
----------
{data}
{lonlat}
{distance_earth}
{magnetic_model}
{common}
Notes
-----
The position of Earth's magnetic north pole is calculated from the first three
coefficients of the selected IGRF model per Franz & Harper (2002). The small
offset between dipole center and Earth center is ignored.
References
----------
{igrf_reference}
"""
[docs]
@add_common_docstring(**_frame_parameters())
class GeocentricSolarMagnetospheric(BaseMagnetic):
"""
A coordinate or frame in the GeocentricSolarMagnetospheric (GSM) system.
- The origin is the center of the Earth.
- The X-axis (0 degrees longitude and 0 degrees latitude) is aligned with the
Earth-Sun line.
- The Z-axis (+90 degrees latitude) is aligned with the component of the Earth's
magnetic north pole that is perpendicular to the X-axis.
Parameters
----------
{data}
{lonlat}
{distance_earth}
{magnetic_model}
{common}
Notes
-----
The position of Earth's magnetic north pole is calculated from the first three
coefficients of the selected IGRF model per Franz & Harper (2002). The small
offset between dipole center and Earth center is ignored.
References
----------
{igrf_reference}
"""
