Examples#

This example gallery using the best practices and illustrates functionality throughout asilib. These are complete examples that are also included in the asilib/examples/ directory on GitHub.

Fisheye Lens View of an Arc#

A bright auroral arc that was analyzed by Imajo et al. 2021 “Active auroral arc powered by accelerated electrons from very high altitudes”

A fisheye lens view of an auroral arc. 
from datetime import datetime

import matplotlib.pyplot as plt

import asilib.asi

location_code = 'RANK'
time = datetime(2017, 9, 15, 2, 34, 0)

asi = asilib.asi.themis(location_code, time=time)
ax, im = asi.plot_fisheye()
plt.colorbar(im)
ax.axis('off')
plt.show()

STEVE projected onto a map#

Maps an image of STEVE (the thin band). Reproduced from http://themis.igpp.ucla.edu/nuggets/nuggets_2018/Gallardo-Lacourt/fig2.jpg

STEVE mapped onto a map. 
from datetime import datetime

import matplotlib.pyplot as plt

import asilib.asi
import asilib.map

ax = asilib.map.create_map(lon_bounds=(-127, -100), lat_bounds=(45, 65))

asi = asilib.asi.themis('ATHA', time=datetime(2010, 4, 5, 6, 7, 0), alt=110)
asi.plot_map(ax=ax)
plt.tight_layout()
plt.show()

Auroral arc projected onto a map#

The first breakup of an auroral arc during a substorm analyzed by Donovan et al. 2008 “Simultaneous THEMIS in situ and auroral observations of a small substorm”

A breakup of an auroral arc projected onto a map of North America. 
from datetime import datetime

import matplotlib.pyplot as plt

import asilib
import asilib.map
import asilib.asi

time = datetime(2007, 3, 13, 5, 8, 45)
location_codes = ['FSIM', 'ATHA', 'TPAS', 'SNKQ']
map_alt = 110
min_elevation = 2

ax = asilib.map.create_simple_map(lon_bounds=(-140, -60), lat_bounds=(40, 82))

_imagers = []

for location_code in location_codes:
    _imagers.append(asilib.asi.themis(location_code, time=time, alt=map_alt))

asis = asilib.Imagers(_imagers)
asis.plot_map(ax=ax, overlap=False, min_elevation=min_elevation)

ax.set_title('Donovan et al. 2008 | First breakup of an auroral arc')
plt.show()

A keogram of STEVE#

A keogram with a STEVE event that moved towards the equator. This event was analyzed in Gallardo-Lacourt et al. 2018 “A statistical analysis of STEVE”

A keogram of STEVE. 
import matplotlib.pyplot as plt

import asilib.asi

location_code = 'LUCK'
time_range = ['2017-09-27T07', '2017-09-27T09']
map_alt_km = 230

fig, ax = plt.subplots(figsize=(8, 6))
asi = asilib.asi.rego(location_code, time_range=time_range, alt=map_alt_km)
ax, p = asi.plot_keogram(ax=ax, color_bounds=(300, 800), aacgm=True)
plt.colorbar(p, label='Intensity')
ax.set_xlabel('UTC')
ax.set_ylabel(f'Magnetic Latitude [deg]\nEmission altitude={map_alt_km} km')
plt.tight_layout()
plt.show()

Keogram of a field line resonance#

A field line resonance studied in: Gillies, D. M., Knudsen, D., Rankin, R., Milan, S., & Donovan, E. (2018). A statistical survey of the 630.0-nm optical signature of periodic auroral arcs resulting from magnetospheric field line resonances. Geophysical Research Letters, 45(10), 4648-4655.

A keogram of a field line resonance. 
import matplotlib.pyplot as plt

import asilib.asi

location_code = 'GILL'
time_range = ['2015-02-02T10', '2015-02-02T11']

asi = asilib.asi.rego(location_code, time_range=time_range, alt=230)
ax, p = asi.plot_keogram(color_map='Greys_r')
plt.xlabel('Time')
plt.ylabel('Geographic Latitude [deg]')
plt.colorbar(p)
plt.tight_layout()
plt.show()

Fisheye Movie#

from datetime import datetime

import asilib.asi

location_code = 'FSMI'
time_range = (datetime(2015, 3, 26, 6, 7), datetime(2015, 3, 26, 6, 30))
asi = asilib.asi.themis(location_code, time_range=time_range)
asi.animate_fisheye()

print(f'Animation saved in {asilib.config["ASI_DATA_DIR"] / "animations" / asi.animation_name}')

Map movie#

from datetime import datetime

import asilib.asi
import asilib.map

time_range = (datetime(2015, 3, 26, 6, 7), datetime(2015, 3, 26, 6, 12))
location_code = 'FSMI'

asi = asilib.asi.themis(location_code, time_range=time_range, alt=110)

lat_bounds = (asi.meta['lat'] - 7, asi.meta['lat'] + 7)
lon_bounds = (asi.meta['lon'] - 20, asi.meta['lon'] + 20)
ax = asilib.map.create_map(lon_bounds=lon_bounds, lat_bounds=lat_bounds)

asi.animate_map(ax=ax)

print(f'Animation saved in {asilib.config["ASI_DATA_DIR"] / "animations" / asi.animation_name}')

Animate Mosaic#

import asilib
import asilib.asi

time_range = ('2021-11-04T06:55', '2021-11-04T07:05')
asis = asilib.Imagers(
    [asilib.asi.trex_rgb(location_code, time_range=time_range)
    for location_code in ['LUCK', 'PINA', 'GILL', 'RABB']]
    )
asis.animate_map(lon_bounds=(-115, -85), lat_bounds=(43, 63), overwrite=True)

ASI-satellite conjunction movie#

A comprehensive example that maps a hypothetical satellite track to an image and calculates the mean ASI intensity in a 20x20 km box around the satellite’s 100 km altitude footprint.

from datetime import datetime

import numpy as np
import matplotlib.pyplot as plt

import asilib
import asilib.asi


# ASI parameters
location_code = 'RANK'
alt=110  # km
time_range = (datetime(2017, 9, 15, 2, 32, 0), datetime(2017, 9, 15, 2, 35, 0))

fig, ax = plt.subplots(
    3, 1, figsize=(7, 10), gridspec_kw={'height_ratios': [4, 1, 1]}, constrained_layout=True
)

asi = asilib.asi.themis(location_code, time_range=time_range, alt=alt)

# Create the fake satellite track coordinates: latitude, longitude, altitude (LLA).
# This is a north-south satellite track oriented to the east of the THEMIS/RANK
# imager.
n = int((time_range[1] - time_range[0]).total_seconds() / 3)  # 3 second cadence.
lats = np.linspace(asi.meta["lat"] + 5, asi.meta["lat"] - 5, n)
lons = (asi.meta["lon"] - 0.5) * np.ones(n)
alts = alt * np.ones(n)  # Altitude needs to be the same as the skymap.
sat_lla = np.array([lats, lons, alts]).T
# Normally the satellite time stamps are not the same as the ASI.
# You may need to call Conjunction.interp_sat() to find the LLA coordinates
# at the ASI timestamps.
sat_time = asi.data.time

conjunction_obj = asilib.Conjunction(asi, (sat_time, sat_lla))

# Map the satellite track to the imager's azimuth and elevation coordinates and
# image pixels. NOTE: the mapping is not along the magnetic field lines! You need
# to install IRBEM and then use conjunction.lla_footprint() before
# calling conjunction_obj.map_azel.
sat_azel, sat_azel_pixels = conjunction_obj.map_azel()

# Calculate the auroral intensity near the satellite and mean intensity within a 10x10 km area.
nearest_pixel_intensity = conjunction_obj.intensity(box=None)
area_intensity = conjunction_obj.intensity(box=(10, 10))
area_mask = conjunction_obj.equal_area(box=(10,10))

# Need to change masked NaNs to 0s so we can plot the rectangular area contours.
area_mask[np.where(np.isnan(area_mask))] = 0

# Initiate the animation generator function.
gen = asi.animate_fisheye_gen(
    ax=ax[0], azel_contours=True, overwrite=True, cardinal_directions='NE'
)

for i, (time, image, _, im) in enumerate(gen):
    # Plot the entire satellite track, its current location, and a 20x20 km box
    # around its location.
    ax[0].plot(sat_azel_pixels[:, 0], sat_azel_pixels[:, 1], 'red')
    ax[0].scatter(sat_azel_pixels[i, 0], sat_azel_pixels[i, 1], c='red', marker='o', s=50)
    ax[0].contour(area_mask[i, :, :], levels=[0.99], colors=['yellow'])

    if 'vline1' in locals():
        vline1.remove()  # noqa: F821
        vline2.remove()  # noqa: F821
        text_obj.remove()  # noqa: F821
    else:
        # Plot the ASI intensity along the satellite path
        ax[1].plot(sat_time, nearest_pixel_intensity)
        ax[2].plot(sat_time, area_intensity)
    vline1 = ax[1].axvline(time, c='b')
    vline2 = ax[2].axvline(time, c='b')

    # Annotate the location_code and satellite info in the top-left corner.
    location_code_str = (
        f'THEMIS/{location_code} '
        f'LLA=({asi.meta["lat"]:.2f}, '
        f'{asi.meta["lon"]:.2f}, {asi.meta["alt"]:.2f})'
    )
    satellite_str = f'Satellite LLA=({sat_lla[i, 0]:.2f}, {sat_lla[i, 1]:.2f}, {sat_lla[i, 2]:.2f})'
    text_obj = ax[0].text(
        0,
        1,
        location_code_str + '\n' + satellite_str,
        va='top',
        transform=ax[0].transAxes,
        color='red',
    )
    ax[1].set(ylabel='ASI intensity\nnearest pixel [counts]')
    ax[2].set(xlabel='Time', ylabel='ASI intensity\n10x10 km area [counts]')

print(f'Animation saved in {asilib.config["ASI_DATA_DIR"] / "animations" / asi.animation_name}')