solar#

discovery.solar.theta_impact(psr)[source]#

From enterprise_extensions: use the attributes of an Enterprise Pulsar object to calculate the solar impact angle. Returns solar impact angle (rad), distance to Earth (R_earth), impact distance (b), perpendicular distance (z_earth).

discovery.solar.make_solardm(psr)[source]#

From enterprise_extensions: calculate DM due to 1/r^2 solar wind density model.

discovery.solar.dm_solar(n_earth, theta, r_earth)[source]#

Calculate dispersion measure from a 1/r^2 solar wind density model.

This function computes the integrated column density of free electrons along the line of sight through the solar wind, assuming a spherically symmetric 1/r^2 density profile. The calculation uses different approximations depending on the solar elongation angle to avoid numerical issues.

Parameters:

  • n_earth (float or ndarray) – Solar wind proton/electron density at Earth’s orbit (cm^-3).

  • theta (float or ndarray) – Solar elongation angle between the Sun and the line of sight to the pulsar (radians). theta = 0 corresponds to the Sun directly in the line of sight, theta = pi/2 is at right angles.

  • r_earth (float or ndarray) – Distance from Earth to Sun (light seconds).

Returns:

Dispersion measure contribution from solar wind (pc cm^-3).

Return type:

float or ndarray

Notes

For small elongation angles (pi - theta < 1e-5), the function uses a close approach approximation to avoid numerical instabilities. Otherwise, it uses the full integral formula from the 1/r^2 density model.

References

[1]

You, X. P., Hobbs, G., Coles, W. A., et al. 2007, MNRAS, 378, 493 “Dispersion measure variations and their effect on precision pulsar timing” https://doi.org/10.1111/j.1365-2966.2007.11617.x

discovery.solar.fourierbasis_solar_dm(psr, components, T=None)[source]#

Construct a Fourier design matrix for solar wind dispersion measure variations.

Parameters:

  • psr (pulsar.Pulsar) – Discovery Pulsar object containing TOAs, frequencies, and solar system ephemeris information.

  • components (int) – Number of Fourier components to include in the model.

  • T (float, optional) – Total timespan of the data in seconds. If None, will be computed from the pulsar’s TOAs.

Returns:

  • f (ndarray) – Sampling frequencies for the Fourier components (Hz).

  • df (float) – Frequency spacing between components (Hz).

  • F (ndarray) – Solar wind DM-variation Fourier design matrix with shape (n_toas, 2*components), where each TOA is weighted by the frequency-dependent solar wind DM delays.

Notes

This function is adapted from enterprise_extensions. The design matrix is constructed by first obtaining a standard Fourier basis, then scaling each TOA by the solar wind DM signature computed from the 1/r^2 solar wind density model.

Examples

Create a Gaussian process model for solar wind DM variations using a powerlaw prior:

>>> from discovery import solar, signals
>>> # Create a solar wind DM GP with 30 Fourier components
>>> gp = signals.makegp_fourier(
...     psr,
...     signals.powerlaw,
...     components=30,
...     fourierbasis=solar.fourierbasis_solar_dm,
...     name='solar_wind_dm'
... )
discovery.solar.makegp_timedomain_solar_dm(psr, covariance, dt=1.0, common=[], name='timedomain_sw_gp')[source]#

Construct a time-domain Gaussian process for solar wind dispersion measure variations.

This function builds a GP model for solar wind-induced DM variations by combining a covariance function in the time domain with a model for the solar wind geometry. The TOAs are quantized into time bins, and the GP is constructed using the time separations between bins weighted by the solar wind DM signature.

Parameters:

  • psr (pulsar.Pulsar) – Discovery Pulsar object containing TOAs, frequencies, and solar system ephemeris information.

  • covariance (callable) – Function that returns the time domain autocorrelation for a given separation (tau). Must have signature covariance(tau, *params) where tau is the time separation array.

  • dt (float, optional) – Time bin width in seconds for quantizing TOAs. Default is 1.0.

  • common (list, optional) – List of parameter names that should be treated as common (shared) across pulsars rather than pulsar-specific. Default is [].

  • name (str, optional) – Base name for the GP parameters. Used as prefix for parameter naming. Default is ‘timedomain_sw_gp’.

Returns:

A matrix.VariableGP object containing the noise covariance matrix (as a NoiseMatrix2D_var) and the design matrix (Umat) that maps the GP to the TOA residuals via solar wind DM delays. See matrix.VariableGP for details.

Return type:

matrix.VariableGP

Notes

The design matrix Umat maps the low-rank GP (evaluated at quantized TOAs) to the full TOA residuals, scaled by the frequency-dependent solar wind DM signature.