MIRACLE data analysis tools
analysis of ground magnetic and ionospheric electric field data using
method of characteristics ("JEQ-based" method of characteristics):
- Short description of the
The "JEQ-based" method of
in an spatial inversion method of ground-based data of the magnetic
disturbance and the ionospheric electric field, to obtain distributions
of ionospheric conductances and currents. In contrast to the previously
used "trial and error" modeling (i.e., guesses of the desired
quantities are gradually improved until the measured quantities
from these models fit the real measurements to a given degree of
this method is a forward one, i.e., the desired quantities are
by solving a differential equation whose coefficients are determined by
the measurements. The primary output of the method is the Hall
from which together with the inputs, the ionospheric currents and
currents (FACs) can be calculated. While other methods ("trial and
KRM, AMIE) need guesses or statistical inputs for both Hall and
conductances separately, the method of charactistics only needs an
of the Hall to Pedersen conductance ratio. This can be assessed from
level of ground magnetic disturbance, supported by all-sky camera or
data if available.
For more details: see
- Input data requirements:
Since the method provides spatial
distributions, also spatial input data of the ground magnetic and
electric field is required. This means:
Furthermore, for small analysis
like it is the case here, the uniqueness of the results will depend on
the electric field structure (coarse rule: the more divergences of E
are in the analysis area, the better).
The method can only be
the area where both input data sets exist, i.e., northern Fennoscandia
(see MIRACLE map).
Good backscatter from both
must be available to obtain electric field vectors for all or most of
common field of view of the radar; this is of particular importance in
the southern part of the STARE common field of view, where the
are located (most restrictive requirement)
All IMAGE stations must be
(typically 3-6 months after the event).
- Output quantities:
Spatial distributions of
conductances, currents and field-aligned currents.
Amm, O., Direct determination
local ionospheric Hall conductance distribution from two- dimensional
and magnetic field data: Application of the method using models of
ionospheric electrodynamic situations, J. Geophys. Res., 100,
Amm, O., Method of
in spherical geometry applied to a Harang discontinuity situation, Ann.
Geophys., 16, 413, 1998.
Amm, O., P. Janhunen, H.J.
T.I. Pulkkinen, and A. Viljanen, Ionospheric shear flow situations
by the MIRACLE network, and the concept of Harang Discontinuity,
to AGU monograph on Magnetospheric Current Systems, Geophysical
Monograph 118, 227, 2000.
Inhester, B., J.
Segatz, and M. Kürschner, Direct determination of the local
Hall conductance distribution from two-dimensional electric and
field data, J. Geophys. Res., 97, 4073, 1992.
This is the input
data: STARE electric field (thin vectors)
and IMAGE by 90 degrees clockwise rotated ground magnetic field
vectors (thick vectors). The event is a shear flow situation observed
August 27, 1998, 2330 UT.
- Example plots:
Hall conductance distribution
obtained by the method of characteristics:
Actual (not equivalent) horizontal
With the results, much of
analysis can be done, as suitable for the respective study. Among
Hall and Pedersen currents, FACs associated with them, curl-free and
parts of current systems, etc. can be calculated. The example below
the FACs due to Sigma_P * div E
for the situation as above:
And here are the FACs
due to (grad Sigma_P) * E:
For further questions and
of events to be analysed, contact Olaf
Maintained by: Olaf
Latest update: 10. 5. 1999