Lifetime models
The tau provides lifetime models.
- Models:
Lifetime within the loss cone (quarter of bounce period in dipole field)
Additional models are grouped into packages that correspond to specific wave-particle interaction, like chorus or hiss.
- Packages:
chorus : Lifetime models due to interaction with chorus waves
hiss : Lifetime models due to interaction with hiss waves
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Calculate the characteristic lifetime (tau_lc) of a charged particle in a dipolar magnetic field. |
Functions
- rbamlib.models.tau.tau_lc(L, al, en, planet='Earth', m=9.1e-28, al_lc=None, nan_flag=False)
Calculate the characteristic lifetime (tau_lc) of a charged particle in a dipolar magnetic field.
This lifetime is defined only for particles with equatorial pitch angle strictly inside the loss cone (α < α_lc). For α ≥ α_lc, the function returns NaN.
- Parameters:
L (float or ndarray) – L-shell parameter (dimensionless).
al (float or ndarray) – Equatorial pitch angle of the particle, in radians.
en (float or ndarray) – Kinetic energy of the particle, in MeV.
planet (str, optional, Default = 'Earth'.) – Name of the planet.
m (float, optional) – Particle mass, in grams. Default is electrons.
al_lc (float or ndarray, optional) – Equatorial loss-cone angle α_lc (radians). If not provided, it is computed with
rbamlib.models.dip.al_lc().nan_flag (boolean) – If set to True the output will be np.nan outside of the loss cone. Otherwise the output is np.inf.
- Returns:
Characteristic lifetime (tau_lc) in seconds. Returns Inf (or NaN) for al ≥ al_lc.
- Return type:
float or ndarray
Notes
The lifetime is calculates as quarter of the the bounce period:
\[\tau_{lc} = \frac{T_{bounce}}{4},\]where \(T_{bounce}\) is computed by
rbamlib.motion.bounce.T_bounce(). This approximation follows Schulz and Lanzerotti [1974] and accounts for relativistic effects.
Specific wave-particle interaction