# MIRACLE data analysis tools

##
4) 2D
magnetic field continuation to the ionosphere and separation into
internal and external
parts (SECS):

###
- Short description of the
analysis
method:

The full 2D set of IMAGE
magnetometers is used to derive 2D maps of
ionospheric equivalent currents (field upward continuation), and to
derive external and internal equivalent currents on the ground (field
separation).

Both techniques utilise 2D Spherical Elementary Current Systems (SECS),
see literature.

### - Input data requirements:

Full 2D set of IMAGE magnetometer
data (upward field continuation:
only horizontal components; field
separation: all three components; see MIRACLE
map for stations overview).
### - Output quantities:

2D maps of ionospheric
equivalent currents (upward
field continuation);

2D maps of external and internal equivalent currents on the ground (field separation).
### - Literature:

- Amm, O., Ionospheric elementary current systems in spherical
coordinates and their application,
*J. Geomagn. Geoelectr., 49*,
947, 1997.
- Amm, O., and Viljanen, A., Ionospheric disturbance magnetic
field
continuation from the ground to the ionosphere using spherical
elementary current systems,
*Earth, Planets and Space, 51*, 431,
1999.
- Pulkkinen, A., O. Amm, A. Viljanen, and BEAR Working Group,
Separation of the geomagnetic variation field on the ground into
external and internal parts using the spherical elementary current
system method,
*Earth Planets Space, 55*, 117, 2003.

###
- Example plots:

This is the input data:
A full 2D set of IMAGE network data on June 26, 1998, 0118 UT. For this
particular event, also data of the temporal BEAR magnetometer network
were available and have been included into the plots and analysis.

Left panel: horizontal
magnetic disturbance vector, rotated by 90 degrees clockwise

Right panel: vertical downward
magnetic disturbance component

- Result plots:

a) upward field
continuation:

This plot shows the resulting ionospheric equivalent currents on the
region marked by the red box in the input data plots:

b) field separation:

The plots below show the internal equivalent currents immediately below
the ground (upper panel), and the external equivalent currents
immediately above the ground (lower panel), on the full IMAGE and BEAR
network area.

Similarly, also the vertical downward magnetic disturbance
component on the ground can be separated into its external part (upper
panel below) and its internal part (lower panel below).

For further questions contact Olaf
Amm or Antti Pulkkinen.

Maintained by: Olaf
Amm

Latest update: 18.03.2004