From 0a3555701177f7cb6e802317ba67516d5d865fd5 Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Fri, 21 Jul 2017 23:52:24 +0800
Subject: clusters/main.py: Add "_magnetic_field()" method

Also update the configurations

Signed-off-by: Aaron LI <aly@aaronly.me>
---
 fg21sim/configs/20-extragalactic.conf.spec | 15 +++++++-------
 fg21sim/extragalactic/clusters/main.py     | 33 ++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/fg21sim/configs/20-extragalactic.conf.spec b/fg21sim/configs/20-extragalactic.conf.spec
index 0f797a8..b8af33b 100644
--- a/fg21sim/configs/20-extragalactic.conf.spec
+++ b/fg21sim/configs/20-extragalactic.conf.spec
@@ -43,6 +43,13 @@
 
   # The fraction that a cluster hosts a radio halo
   halo_fraction = float(default=None, min=0.0, max=1.0)
+  # Magnetic field scaling relation for clusters
+  # Reference: Cassano et al. 2012, A&A, 548, A100, Eq.(1)
+  #
+  # The mean magnetic field assumed
+  b_mean = float(default=1.9, min=0.1, max=10)
+  # The index of the scaling relation
+  b_index = float(default=1.5, min=0.0, max=3.0)
 
   # Resolution for simulating each cluster templates, which are finally
   # mapped to the all-sky HEALPix map if used.
@@ -73,14 +80,6 @@
   # XXX: currently only support a constant radius of halos
   radius = float(default=500.0, min=100.0)
 
-  # Magnetic field scaling relation for clusters
-  # Reference: Cassano et al. 2012, A&A, 548, A100, Eq.(1)
-  #
-  # The mean magnetic field assumed
-  b_mean = float(default=1.9, min=0.1, max=10)
-  # The index of the scaling relation
-  b_index = float(default=1.5, min=0.0, max=3.0)
-
   # Fraction of the turbulence energy in the form of magneto-sonic waves.
   eta_t = float(default=0.3, min=0.0, max=1.0)
 
diff --git a/fg21sim/extragalactic/clusters/main.py b/fg21sim/extragalactic/clusters/main.py
index b7c2d03..b6c1022 100644
--- a/fg21sim/extragalactic/clusters/main.py
+++ b/fg21sim/extragalactic/clusters/main.py
@@ -9,6 +9,12 @@ NOTE
 ----
 There are other types of extended radio emissions not considered
 yet, e.g., mini-halos, roundish radio relics, etc.
+
+References
+----------
+.. [cassano2012]
+   Cassano et al. 2012, A&A, 548, A100
+   http://adsabs.harvard.edu/abs/2012A%26A...548A.100C
 """
 
 import logging
@@ -57,6 +63,8 @@ class GalaxyClusters:
         self.merger_mass_min = self.configs.getn(comp+"/merger_mass_min")
         self.ratio_major = self.configs.getn(comp+"/ratio_major")
         self.tau_merger = self.configs.getn(comp+"/tau_merger")
+        self.b_mean = self.configs.getn(comp+"/b_mean")
+        self.b_index = self.configs.getn(comp+"/b_index")
 
         self.filename_pattern = self.configs.getn("output/filename_pattern")
         self.use_float = self.configs.getn("output/use_float")
@@ -204,6 +212,31 @@ class GalaxyClusters:
         logger.info("%d (%.1f%%) clusters have recent major mergers." %
                     (num_major, 100*num_major/num))
 
+    def _magnetic_field(self, mass):
+        """
+        Calculate the mean magnetic field strength according to the
+        scaling relation between magnetic field and cluster mass.
+
+        Parameters
+        ----------
+        mass : float
+            Cluster mass
+            Unit: [Msun]
+
+        Returns
+        -------
+        B : float
+            The mean magnetic field strength
+            Unit: [uG]
+
+        References
+        ----------
+        Ref.[cassano2012],Eq.(1)
+        """
+        M_mean = 1.6e15  # [Msun]
+        B = self.b_mean * (mass/M_mean) ** self.b_index
+        return B
+
     def preprocess(self):
         """
         Perform the preparation procedures for the later simulations.
-- 
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