Geopack08 wrapper for Python
Project description
PyGeopack
A Python wrapper for Geopack-2008. This includes the T89, T96, T01 and TS05 (or is it TS04? I don't know...) magnetic field models for Earth's magnetosphere. See https://ccmc.gsfc.nasa.gov/modelweb/magnetos/tsygan.html and http://geo.phys.spbu.ru/~tsyganenko/modeling.html for more information.
Requirements
The following Python packages will be installed automatically:
- numpy
- PyFileIO
- RecarrayTools
- DateTimeTools
The following packages will also be required for running the
PyGeopack.UpdateParameters()
routine:
- kpindex
- pyomnidata
Installation
Firstly a few environment variables need setting up: $KPDATA_PATH
,
$OMNIDATA_PATH
and $GEOPACK_PATH
, which will point to the Kp index
data, the omni data and the Geopack data, respectively. This can be done
by including the following in your ~/.bashrc
file, or by running it in
the terminal before starting Python:
export KPDATA_PATH=/path/to/kp
export OMNIDATA_PATH=/path/to/omni
export GEOPACK_PATH=/path/to/geopack/data
where both of those directories must be writable by the current user, unless the data already exist in them.
Then simply install using pip3:
pip3 install PyGeopack --user
or by downloading the latest release on GitHub and running:
pip3 install PyGeopack-0.1.0-py3-none-any.whl --user
NOTE: You should uninstall any previous versions before installing this. If you had a version installed before 0.0.12 - you will need to remove the old shared object files - they are likely to be contained somewhere like (depending on the Python version used):
~/.local/lib/python3.6/site-packages/PyGeopack/
It's best just to remove everyting within that folder!
Post-install
After installation, the PyGeopack module will attempt to locate the
OMNI data required for the models. If these data exist already in
$GEOPACK_PATH
then it will load into memory. If they don't exist, then
the user will be shown a warning - the next section explains how to fix
this.
Usage
There are three main uses for this Python package:
- Calculating the model magnetic field at any given point in space.
- Tracing along the magnetic field.
- Coordinate conversions.
Before doing any of the above, it's recommended that you grab the up to
date omni parameters - the UpdateParameters
routine will download and
update the Kp index and OMNI parameters, then calculate the G and W
parameters required for the models:
import PyGeopack as gp
gp.UpdateParameters(SkipWParameters=True)
The SkipWParameters
keyword (set to True
by default) can be used to
skip the lengthy process of calculating the six W parameters for the
TS05 magnetic field model - if True
then these will be filled with
zeros. Apparently they aren't all that important anyway. The code
included in this module can calculate them and is Tsyganenko's own code,
but it produces different numbers to those given in the files on
Tsyganenko's website! No idea why, so use them with caution!
1. Calculating the model field.
To calculate the model field, use the ModelField
function:
Bx,By,Bz = gp.ModelField(x,y,z,Date,ut,Model='T96',CoordIn='GSM',CoordOut='GSM',**kwargs)
Where x
, y
and z
are the position(s) you wish to find the magnetic
field at in RE - these can be either scalars or
numpy.ndarray
s. Date
is the date as an integer, in the format
yyyymmdd. ut
is the time in hours, i.e. ut = hours + mins/60 + secs/3600
.
Model
can be set to one of four strings currently: 'T89'
, 'T96'
(default), 'T01'
or 'TS05'
, more information about the models will
be discussed further down in this document. CoordIn
and CoordOut
denote the input and output coordinate systems, respectively, and can be
set to one of the three following options: 'GSM'
(default), 'GSE'
or
'SM'
. **kwargs
are discussed in detail in the "Model Parameters"
section. Bx
, By
and Bz
are the three components of the magnetic
field model in nT for each of the input coordinates.
2. Tracing the magnetic field
Trace along the magnetic field from 1 or more starting positions in the
magnetosphere x
, y
and z
using the TraceField
object:
T = gp.TraceField(x,y,z,Date,ut,Model='T96',CoordIn='GSM',CoordOut='GSM',
alt=100.0,MaxLen=1000,DSMax=1.0,FlattenSingleTraces=True,Verbose=True,**kwargs)
x
, y
and z
can either be scalars, or arrays of coordinates in
RE.
Date
can either be a single date, for all traces, or an array of dates
(one for each trace) where each is an integer in the format yyyymmhh.
ut
is the time in hours (i.e. ut = hours + mins/60
) and can either
be a single value for all traces, or an array with a time for each trace.
Model
denotes the field model being used - 'T89'
, 'T96'
(default),
'T01'
or 'TS05'
.
CoordIn
and CoordOut
denote the input and output coordinate systems,
respectively, and can be set to one of the three following options:
'GSM'
(default), 'GSE'
or 'SM'
.
alt
is the altitude in km atwhich the trace will be terminated
(alt = 100.0
by default).
MaxLen
is the maximum number of steps for the traces (default is 1000).
DSMax
is the maximum step length in RE (default 1.0).
FlattenSingleTraces
if set to True
will flatten the 2D arrays stored
in the TraceField
object if only a single trace is performed.
Verbose
is True
will output the tracing progress to the terminal.
**kwargs
will be discussed in the "Model Parameters" section.
The TraceField
object, T
in the above code snippet, contains the
following arrays:
x |
x coordinate along the field trace(s) |
y |
y coordinate along the field trace(s) |
z |
z coordinate along the field trace(s) |
Bx |
x component of the magnetic field along the trace(s) |
By |
y component of the magnetic field along the trace(s) |
Bz |
z component of the magnetic field along the trace(s) |
nstep |
number of steps along the trace(s) |
GlatN |
Geographic latitude of the northern footprint(s) |
GlatS |
Geographic latitude of the southern footprint(s) |
MlatN |
Magnetic latitude of the northern footprint(s) |
MlatS |
Magnetic latitude of the southern footprint(s) |
GlonN |
Geographic longitude of the northern footprint(s) |
GlonS |
Geographic longitude of the southern footprint(s) |
MlonN |
Magnetic longitude of the northern footprint(s) |
MlonS |
Magnetic longitude of the southern footprint(s) |
GltN |
Geographic local time of the northern footprint(s) |
GltS |
Geographic local time of the southern footprint(s) |
MltN |
Magnetic local time of the northern footprint(s) |
MltS |
Magnetic local time of the southern footprint(s) |
Lshell |
L-shell of the field line(s) at the equator |
MltE |
Magnetic local time of the equatorial footprint(s) |
FlLen |
Field line length in planetary radii |
R |
R = sqrt(x**2 + y**2 + z**2) |
3. Coordinate conversion
This module contains the following Cartesian coordinate conversion routines:
x1,y1,z1 = gp.GSEtoGSM(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.GSEtoMAG(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.GSEtoSM(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.GSMtoGSE(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.GSMtoSM(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.MAGtoGSE(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.SMtoGSE(x0,y0,z0,Date,ut)
x1,y1,z1 = gp.SMtoGSM(x0,y0,z0,Date,ut)
where x0
, y0
and z0
are either scalars or arrays of positions to
be transformed. Date
is an integer in the format yyyymmdd and ut
is
the time in hours (i.e. ut = hours + minutes/60.0
). x1
, y1
and
z1
are the transformed coordinates.
Also included are the following routines:
MLon,MLat = gp.GEOtoMAG(Lat,Lon,Date,ut)
Lon,Lat = gp.MAGtoGEO(MLat,MLon,Date,ut)
which convert between geographic ( Lat
and Lon
) and magnetic ( MLat
and MLon
) latitude and longitudes.
And for converting between magnetic longitude (MLon
) and magnetic
local time (MLT
):
MLT = gp.MLONtoMLT(MLon,Date,ut)
MLon = gp.MLTtoMLON(MLT,Date,ut)
Descriptions of the coordinate systems:
Name | Description | x | y | z |
---|---|---|---|---|
GSE - Geocentric Solar Ecliptic | fixed | Towards the Sun | Opposite to Earth's orbit | Perpendicular to the ecliptic plane |
GSM - Geocentric Solar Magnetospheric | fixed | Towards the Sun | Projection of the dipole axis in the Y-Z GSE plane | |
SM - Solar Magnetic | fixed | In the plane containing the Earth-Sum line and the dipole axis | Along the dipole axis | |
MAG - Geomagnetic | rotating | Through intersection of magnetic equator and geographic meridian 90 degrees east of the meridian containing the dipole axis | Along the dipole axis | |
GEO - Geographic | rotating | Through intersection of equator and Greenwich meridian | Along Earth's rotation axis |
NOTE: By "fixed", I mean that they do not rotate with the Earth's spin, they are not really fixed.
Model Parameters
In this section, the parameters and relevant **kwargs
are discussed
for each model. If **kwargs
aren't used, then the relevant parameters
are found autmoatically for the date and time provided when using the
models. Individual parameters amy be altered without affecting the
others - if only a single parameter is changed, then the others are
still automatically calculated. The **kwargs
accepted by ModelField
and TraceField
are:
Keyword | Data Type | Description |
---|---|---|
iopt |
scalar integer | iopt=Kp+1 (iopt=7 for Kp>=6) |
parmod |
10-element float array | Elements 0 - 3 are Pdyn, SymH, IMF By and IMF Bz, respectively. Elements 4 - 9 depend on the model |
tilt |
scalar float | The dipole tilt angle in radians |
Vx |
scalar float | x component of solar wind velocity |
Vy |
scalar float | y component of solar wind velocity |
Vz |
scalar float | z component of solar wind velocity |
Kp |
scalar integer | Kp index |
Pdyn |
scalar float | Dynamic pressure in nPa |
SymH |
scalar float | SymH in nT |
By |
scalar float | IMF y component in nT |
Bz |
scalar float | IMF z component in nT |
All models can be affected by the Vx
, Vy
, and Vz
parameters as
these are used to aberrate the coordinates into the GSW frame, where
GSW is equivalent to GSM in the situation where Vy=0
and Vz=0
.
tilt
is calculated automatically for all models based on the date,
time and the IGRF magnetic field model.
T89
The only parameter used here is iopt
which can be controlled with
either setting iopt
or Kp
keywords to an integer. Valid values for
iopt
are integers in the range 1-7, if Kp
is set, then iopt
is
set automatically equal to Kp+1
. For Kp
>=6 iopt=7
.
T96
The first four elements of the parmod
array are used for this model
where parmod[0]
is the dynamic pressure, parmod[1]
is the SymH,
parmod[2]
is the y component of the interplanetary magnetic field
(IMF) and parmod[3]
is the z component of the IMF. All other elements
of this array are ignored. The entire parmod
array can be set using
the parmod
keyword, otherwise individual elements can be edited using
the Pdyn
, SymH
, By
and Bz
keywords, where other unchanged
parameters will be calculated automatically.
T01
This model uses the first six elements of the parmod
array, where the
first four are set in exactly the same way as in the T96 model.
parmod[4]
and parmod[5]
correspond to the G1 and G2 parameters
calculated in Tsyganenko, 2002b. These can, I believe, be set to 0.
TS05
This model uses all of the parmod
array, where the first four are as
in the T96 model. The last 6 elements are the W1-W6 parameters described
in Tsyganenko and Sitnov, 2005.
References
- N.A. Tsyganenko, A Magnetospheric Magnetic Field Model with a Warped Tail Current Sheet, Planet. Space Sci. 37, 5-20, 1989.
- N.A. Tsyganenko, Modeling the Earth's Magnetospheric Magnetic Field Confined Within a Realistic Magnetopause, J.Geophys.Res., 100, 5599-5612, 1995.
- N.A. Tsyganenko and D.P. Stern, Modeling the Global Magnetic Field of the Large-Scale Birkeland Current Systems, J. Geophys.Res., 101, 27187-27198, 1996.
- N.A. Tsyganenko, A model of the near magnetosphere with a dawn-dusk asymmetry - 1. Mathematical Structure, J. Geophys.Res., 107, A8, 10.1029/2001JA000219, 2002.
- N.A. Tsyganenko, A model of the near magnetosphere with a dawn-dusk asymmetry - 2. Parameterization and fitting to observations, J. Geophys.Res., 107, A7, 10.1029/2001JA000220, 2002.
- N.A. Tsyganenko and M. I. Sitnov, Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms, J. Geophys.Res., 110, A3, 10.1029/2004JA010798, 2005.
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