Some simple tools for modelling MHD wave harmonics in an arbitrary magnetic field geometry.
Project description
MHDWaveHarmonics
Some simple tools for modelling MHD wave harmonics in an arbitrary magnetic field geometry.
Installation
Install using pip3
:
pip3 install MHDWaveHarmonics user
The installation will require the following packages:
numpy
scipy
matplotlib
PyGeopack
FieldTracing
all of which will be installed automatically. For modelling waves in
Mercury's magnetosphere you will also require the KT17
model.
Usage
1. GetFieldLine
The GetFieldLine
function will trace a model field, returning a
TraceField
object alongside a numpy.ndarray
, s
, which contains the
distance along the traced field line and optionally h
if the
polarization is specified:
import MHDWaveHarmonics as wh T,s = wh.GetFieldLine(pos,Date=None,ut=None,Model='KT17',Delta=None,Polarization='none',**kwargs) T,s,h = wh.GetFieldLine(pos,Date=None,ut=None,Model='KT17',Delta=None,Polarization='poloidal',**kwargs)
where h
is provided using a second trace if the Polarization
parameter
is set to 'poloidal'
, 'toroidal'
or a float
corresponding to an
angle in degrees anticlockwise from the poloidal direction (the outward
pointing normal direction of the field line). Use wh.GetFieldLine?
to find out more about this procedure from its docstring.
2. SolveWave
This procedure will attempt to solve the wave equation along an arbitrary
magnetic field trace such as that provided by GetFieldLine
:
yr = wh.SolveWave(f,x,B,R=None,Va=None,halpha=None,Params=None,InPlanet=None,Method='Simple',Unscale=True) yr,yi,phase = SolveWave(f,x,B,R=None,Va=None,halpha=None,Params=None,InPlanet=None,Method='Complex',Unscale=True)
where yr
is the real part of the scaled field displacement, ξ/h_{α} , yi
is the imaginary part, and phase
is a continuous measure of the waves
phase along the trace. See the docstring for more information.
3. FindHarmonics
This will attempt to solve the wave equation in order to find a number of harmonics which would be allowed to exist:
freq,success,niter = wh.FindHarmonics(T,s,Params,halpha=None,Harmonics=[1,2,3],x0=None,df=1.0,Method='Complex')
where freq
is an array of allowed frequencies, success
is a Boolean
array denoting whether each fit was successful or not and niter
is an
array containing the number of iterations reqquired for each fit.
4. CalcFieldLineVa
This will calculate the Alfven speed at each point along the trace:
va = CalcFieldLineVa(T,s,Params,halpha=None)
or at the midpoint between each pair of consecutive steps along the trace:
vamid = CalcFieldLineVaMid(T,s,Params,halpha=None)
5. PlotHarmonics
This will produce a plot of the allowed toroidal and poloidal harmonics on a field line given an initial position for the trace and a plasma mass density profile along the field.
PlotHarmonics(pos,Params,nh=3,df=1.0,Rp=1.0,Colours=None,Method='Complex',**kwargs)
6. FitPlasmaToHarmonic
Attempts to fit a power law or the Sandhu et al model plasma mass density profile to a given field trace.
p_eq = FitPlasmaToHarmonic(T,s,halpha,f,Params,Harm=1,df=1.0,Method='Complex')
7. FitPlasma
This tries to fit the plasma mass density profile to a set of observed frequencies (with their assumed harmonic numbers) along a field trace.
params = FitPlasma(T,s,halpha,freqs,harms,Params0,df=1.0,Method='Complex',ParamFit=None)
8. GetSandhuParams
Calculates the parameters for the Sandhu et al electron density and average ion mass models.
ne0,alpha,a,beta,mav0 = GetSandhuParams(mlt,L)
9. PlotFieldLineDensity
Plots the modelled density along a field line given a position in which to start a field trace and a set of plasma profile parameters.
PlotFieldLineDensity(pos,Params,fig=None,maps=[1,1,0,0],Overplot=False,**kwargs)
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