Hi Stuart, You can extract the magnetic field angles using the method zeeman_magnetic_fieldCalc. This requires setting up a single 3D calculations and is basically just useful to verify that you have the same angles.
The angles are otherwise defined as in the 2014 paper. The figure in
question is attached. The explanation reads:
Geometry of the propagation, the local magnetic field and polarization
axes.
All vectors in the plot are of the same length.
Specifically,
$\hat{e}_v$ is the vertical polarization axis of the sensor,
$\hat{e}'_v$ is the vertical polarization axis along the magnetic field $
\hat{H}$ in the plane of the direction of propagation $\hat{R}$,
$\hat{e}_h$ is the horizontal polarization axis of the sensor,
$\hat{e}'_h$ is the horizontal polarization axis perpendicular to $\hat{H}$
in the plane of $\hat{R}$,
$\theta$ is the angle between $\hat{H}$ and $\hat{R}$, and
$\eta$ is the clockwise angle between $\hat{e}'_v$ and $\hat{e}_v$ (or
between $\hat{e}'_h$ and $\hat{e}_h$).
Note that $\hat{e}_v$, $\hat{e}'_v$, $\hat{e}_h$ and $\hat{e}'_h$ are
always in the plane of $\hat{R}$.
Also note that $\hat{e}'_v$, $\hat{R}$ and $\hat{H}$ are always in the
plane of $\hat{e}'_h$.
With hope,
//Richard
Den fre 29 aug. 2025 kl 23:03 skrev Patrick Eriksson via arts_users.mi <
[email protected]>:
> Stuart,
>
> As far as I know, you can not import data for theta and eta.
>
> The rule is that missing elements in pos and los are implied to be zero.
> That is, for a 1D case the sensor is at (lat,lon) = (0,0) looking north
> (az=0). With this I hope you can figure out how to set the values of
> rtp_mag to get the angles between LOS and magnetic field you want.
>
> Richard, correct me if I am wrong on some point!
>
> Bye,
> Patrick
>
>
> On 8/29/25 15:46, Stuart Fox via arts_users.mi wrote:
> > OFFICIAL
> >
> >
> > Hi ARTS team,
> >
> > I am trying to do some simple Zeeman calculations in the 50GHz oxygen
> > band. My intention is to use a simple 1D atmosphere, and define a manual
> > magnetic field in propmat_clearsky_agendaAuto. However, I can’t find a
> > definition for the meaning of angles theta and eta. How are these
> > defined in the 1D case, and how do they relate to the sensor line-of-
> > sight or propagation path direction?
> >
> > Thanks,
> >
> > Stuart
> >
> > Dr Stuart Fox Airborne Research Science Lead
> > *Met Office* FitzRoy Road Exeter Devon EX1 3PB United Kingdom
> > Tel: +44 (0)1392 885197 Fax: +44 (0)1392 885681
> > Email: [email protected] Website: www.metoffice.gov.uk
> >
> >
> > OFFICIAL
> >
>
>
geometry.pdf
Description: Adobe PDF document
