From 339daa8b276c52755eb635acf5771652a422a088 Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Thu, 4 Jan 2018 22:37:17 +0800
Subject: clusters/halo: refactor tau_acceleration() to help RadioHaloAM
Change "tau_acceleration" from a attribute to a method with the time
parameter, and then simplify "fp_diffusion()" method.
---
fg21sim/extragalactic/clusters/halo.py | 62 +++++++++++++++++++++-------------
fg21sim/extragalactic/clusters/main.py | 2 +-
2 files changed, 39 insertions(+), 25 deletions(-)
diff --git a/fg21sim/extragalactic/clusters/halo.py b/fg21sim/extragalactic/clusters/halo.py
index 1481899..f8902a3 100644
--- a/fg21sim/extragalactic/clusters/halo.py
+++ b/fg21sim/extragalactic/clusters/halo.py
@@ -285,9 +285,7 @@ class RadioHalo:
z = COSMO.redshift(t)
return helper.kT_cluster(mass=mass, z=z, configs=self.configs)
- @property
- @lru_cache()
- def tau_acceleration(self):
+ def tau_acceleration(self, t=None):
"""
Calculate the electron acceleration timescale due to turbulent
waves, which describes the turbulent acceleration efficiency.
@@ -310,13 +308,37 @@ class RadioHalo:
τ_acc = p^2 / (4*D_pp)
= (η_e * c_s^3 * L) / (16π * ζ * <v_turb^2>^2)
- Unit: [Gyr]
+ NOTE
+ ----
+ Considering that the turbulence acceleration is a 2nd-order Fermi
+ process, it has only an effective acceleration time ~<1 Gyr.
+ Therefore, only during the period that strong turbulence persists
+ in the ICM that the turbulence could effectively accelerate the
+ relativistic electrons.
+
+ Parameters
+ ----------
+ t : float, optional
+ The cosmic time when to determine the acceleration timescale.
+ Default: ``self.age_obs``
+
+ Returns
+ -------
+ tau : float
+ The acceleration timescale at the requested time.
+ Return ``np.inf`` if no active turbulence at that time.
+ Unit: [Gyr]
- Reference
- ---------
+ References
+ ----------
* Ref.[pinzke2017],Eq.(37)
* Ref.[miniati2015],Eq.(29)
"""
+ if t is None:
+ t = self.age_begin
+ if t > self.age_begin + self.time_turbulence:
+ return np.inf
+
R_vir = helper.radius_virial(mass=self.M_main, z=self.z_merger)
L = self.f_lturb * R_vir # [kpc]
cs = helper.speed_sound(self.kT_main()) # [km/s]
@@ -500,14 +522,6 @@ class RadioHalo:
which is described by the ``tau_acc`` acceleration timescale
parameter.
- NOTE
- ----
- Considering that the turbulence acceleration is a 2nd-order Fermi
- process, it has only an effective acceleration time ~<1 Gyr.
- Therefore, only during the period that strong turbulence persists
- in the ICM that the turbulence could effectively accelerate the
- relativistic electrons.
-
WARNING
-------
A zero diffusion coefficient may lead to unstable/wrong results,
@@ -545,12 +559,12 @@ class RadioHalo:
# Maximum acceleration timescale when no turbulence acceleration
# NOTE: see the above WARNING!
tau_max = 10.0 # [Gyr]
- if (t < self.age_begin) or (t > self.age_begin+self.time_turbulence):
- # NO active turbulence acceleration
+ if t < self.age_begin:
+ # To derive the initial electron spectrum
tau_acc = tau_max
else:
- # Turbulence acceleration
- tau_acc = self.tau_acceleration # [Gyr]
+ # Turbulence acceleration and beyond
+ tau_acc = self.tau_acceleration(t=t)
# Impose the maximum acceleration timescale
if tau_acc > tau_max:
tau_acc = tau_max
@@ -577,12 +591,12 @@ class RadioHalo:
"""
if t < self.age_begin:
# To derive the initial electron spectrum
- advection = (abs(self._loss_ion(gamma, self.age_begin)) +
- abs(self._loss_rad(gamma, self.age_begin)))
+ advection = (abs(self._loss_ionization(gamma, self.age_begin)) +
+ abs(self._loss_radiation(gamma, self.age_begin)))
else:
# Turbulence acceleration and beyond
- advection = (abs(self._loss_ion(gamma, t)) +
- abs(self._loss_rad(gamma, t)) -
+ advection = (abs(self._loss_ionization(gamma, t)) +
+ abs(self._loss_radiation(gamma, t)) -
(self.fp_diffusion(gamma, t) * 2 / gamma))
return advection
@@ -677,7 +691,7 @@ class RadioHalo:
v2_turb = v2_vir * (self.eta_turb / fmass) * (self.M_sub / mass)
return np.sqrt(v2_turb)
- def _loss_ion(self, gamma, t):
+ def _loss_ionization(self, gamma, t):
"""
Energy loss through ionization and Coulomb collisions.
@@ -706,7 +720,7 @@ class RadioHalo:
loss = -3.79e4 * n_th * (1 + np.log(gamma/n_th) / 75)
return loss
- def _loss_rad(self, gamma, t):
+ def _loss_radiation(self, gamma, t):
"""
Energy loss via synchrotron emission and inverse Compton
scattering off the CMB photons.
diff --git a/fg21sim/extragalactic/clusters/main.py b/fg21sim/extragalactic/clusters/main.py
index b2ed530..c677f92 100644
--- a/fg21sim/extragalactic/clusters/main.py
+++ b/fg21sim/extragalactic/clusters/main.py
@@ -280,7 +280,7 @@ class GalaxyClusters:
("Rhalo_angular", halo.angular_radius), # [arcsec]
("volume", halo.volume), # [kpc^3]
("Mach_turb", halo.mach_turbulence), # turbulence Mach number
- ("tau_acc", halo.tau_acceleration), # [Gyr]
+ ("tau_acc", halo.tau_acceleration()), # [Gyr]
("Ke", halo.injection_rate), # [cm^-3 Gyr^-1]
("gamma", halo.gamma), # Lorentz factors
("n_e", n_e), # [cm^-3]
--
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