[yt-svn] commit/yt: ngoldbaum: Fixing the way magnetic fields are handled in the FLASH frontend. This explicitly corrects for the user's choice of coordinate system. Adding some useful universal fields that depend on magnetic quantities. Fixing a minor typo in the chombo frontend. Closes #429

[Bitbucket]

1 new commit in yt:


https://bitbucket.org/yt_analysis/yt/changeset/de5451397981/
changeset:   de5451397981
branch:      yt
user:        ngoldbaum
date:        2012-10-02 01:39:33
summary:     Fixing the way magnetic fields are handled in the FLASH frontend.  This explicitly corrects for the user's choice of coordinate system.  Adding some useful universal fields that depend on magnetic quantities.  Fixing a minor typo in the chombo frontend.  Closes #429
affected #:  3 files

diff -r e56c3f9dca02e663bddc24fdd04a30bff793788b -r de5451397981bca072e120ea53540e571ff56669 yt/data_objects/universal_fields.py
--- a/yt/data_objects/universal_fields.py
+++ b/yt/data_objects/universal_fields.py
@@ -994,12 +994,37 @@
     units of Gauss. If you use MKS, make sure to write your own
     MagneticEnergy field to deal with non-unitary \mu_0.
     """
-    return (data["Bx"]**2 + data["By"]**2 + data["Bz"]**2)/2.
+    return (data["Bx"]**2 + data["By"]**2 + data["Bz"]**2)/(8*np.pi)
 add_field("MagneticEnergy",function=_MagneticEnergy,
-          units=r"",
-          validators = [ValidateDataField("Bx"),
-                        ValidateDataField("By"),
-                        ValidateDataField("Bz")])
+          units=r"\rm{ergs}\/\rm{cm}^{-3}",
+          display_name=r"\rm{Magnetic}\/\rm{Energy}")
+
+def _BMagnitude(field,data):
+    """This assumes that your front end has provided Bx, By, Bz in
+    units of Gauss. If you use MKS, make sure to write your own
+    MagneticEnergy field to deal with non-unitary \mu_0.
+    """
+    return np.sqrt((data["Bx"]**2 + data["By"]**2 + data["Bz"]**2))
+add_field("BMagnitude",
+          function=_BMagnitude,
+          display_name=r"|B|", units="\rm{Gauss}")
+
+def _PlasmaBeta(field,data):
+    """This assumes that your front end has provided Bx, By, Bz in
+    units of Gauss. If you use MKS, make sure to write your own
+    MagneticEnergy field to deal with non-unitary \mu_0.
+    """
+    return data['Pressure']/data['MagneticEnergy']
+add_field("PlasmaBeta",
+          function=_PlasmaBeta,
+          display_name=r"\rm{Plasma}\/\beta", units="")
+
+def _MagneticPressure(field,data):
+    return data['MagneticEnergy']
+add_field("MagneticPressure",
+          function=_MagneticPressure,
+          display_name=r"\rm{Magnetic}\/\rm{Energy}",
+          units="\rm{ergs}\/\rm{cm}^{-3}")
 
 def _VorticitySquared(field, data):
     mylog.debug("Generating vorticity on %s", data)


diff -r e56c3f9dca02e663bddc24fdd04a30bff793788b -r de5451397981bca072e120ea53540e571ff56669 yt/frontends/chombo/fields.py
--- a/yt/frontends/chombo/fields.py
+++ b/yt/frontends/chombo/fields.py
@@ -101,17 +101,17 @@
 def _Bx(field,data):
     return data["X-magnfield"]
 add_field("Bx", function=_Bx, take_log=False,
-          units=r"\rm{Gauss}", display_name=r"B")
+          units=r"\rm{Gauss}", display_name=r"B_x")
 
 def _By(field,data):
     return data["Y-magnfield"]
 add_field("By", function=_By, take_log=False,
-          units=r"\rm{Gauss}", display_name=r"B")
+          units=r"\rm{Gauss}", display_name=r"B_y")
 
 def _Bz(field,data):
     return data["Z-magnfield"]
 add_field("Bz", function=_Bz, take_log=False,
-          units=r"\rm{Gauss}", display_name=r"B")
+          units=r"\rm{Gauss}", display_name=r"B_z")
 
 def _MagneticEnergy(field,data):
     return (data["X-magnfield"]**2 +


diff -r e56c3f9dca02e663bddc24fdd04a30bff793788b -r de5451397981bca072e120ea53540e571ff56669 yt/frontends/flash/fields.py
--- a/yt/frontends/flash/fields.py
+++ b/yt/frontends/flash/fields.py
@@ -23,6 +23,7 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
+import numpy as np
 from yt.data_objects.field_info_container import \
     FieldInfoContainer, \
     NullFunc, \
@@ -254,3 +255,43 @@
 
 add_field("GasEnergy", function=_GasEnergy, 
           units=r"\rm{ergs}/\rm{g}")
+
+# See http://flash.uchicago.edu/pipermail/flash-users/2012-October/001180.html
+# along with the attachment to that e-mail for details
+def GetMagRescalingFactor(pf):
+    if pf['unitsystem'].lower() == "cgs":
+         factor = 1
+    if pf['unitsystem'].lower() == "si":
+         factor = np.sqrt(4*np.pi/1e7)
+    if pf['unitsystem'].lower() == "none":
+         factor = np.sqrt(4*np.pi)
+    else:
+        raise RuntimeError("Runtime parameter unitsystem with"
+                           "value %s is unrecognized" % pf['unitsystem'])
+    return factor
+
+def _Bx(fields, data):
+    factor = GetMagRescalingFactor(data.pf)
+    return data['magx']*factor
+add_field("Bx", function=_Bx, take_log=False,
+          units=r"\rm{Gauss}", display_name=r"B_x")
+
+def _By(fields, data):
+    factor = GetMagRescalingFactor(data.pf)
+    return data['magy']*factor
+add_field("By", function=_By, take_log=False,
+          units=r"\rm{Gauss}", display_name=r"B_y")
+
+def _Bz(fields, data):
+    factor = GetMagRescalingFactor(data.pf)
+    return data['magz']*factor
+add_field("Bz", function=_Bz, take_log=False,
+          units=r"\rm{Gauss}", display_name=r"B_z")
+
+def _DivB(fields, data):
+    factor = GetMagRescalingFactor(data.pf)
+    return data['divb']*factor
+add_field("DivB", function=_DivB, take_log=False,
+          units=r"\rm{Gauss}\/\rm{cm}^{-1}")
+
+

Repository URL: https://bitbucket.org/yt_analysis/yt/

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