MIRACLE data analysis tools

6) Combined analysis of multi-satellite FAC data and ionospheric electric field data using the method of characteristics ("FAC-based" method of characteristics):

- Short description of the analysis method:

The "FAC-based" method of characteristics combines spatial data of the ionospheric electric field (as obtained by coherent scatter radars like STARE or SuperDARN) with field-aligned current (FAC) estimates from a fleet of satellites (like CLUSTER II), mapped down to the ionosphere, to calculate 2D distributions of the true (not equivalent) ionospheric currents and the ionospheric conductances. The primary output of the method is the Hall conductance, from which together with the inputs, the actual (not equivalent) ionospheric currents and the Pedersen conductance can be calculated. The "FAC-based" method of charactistics needs an estimate of the Hall to Pedersen conductance ratio, which can be assessed from the level of ground magnetic disturbance, supported by all-sky camera or satellite data if available.

For more details: see Literature (below)

- Input data requirements:

Spatial input data of the ionospheric electric field, and of the field-aligned currents (FACs) as measured by the satellites, mapped down to the ionosphere.
To obtain 2D FAC distributions from the satellites, it is of advantage if the ionospheric situation to be studied can be assumed stationary for the time that either: Then, FAC data of different timesteps can be reduced to a reference timestep, with respect to the velocity of the ionospheric feature and/or of the satellites' footpoints, to obtain a more complete 2D FAC distribution.

- Output quantities:

Spatial distributions of Hall- and Pedersen conductances, and the true (not equivalent) ionospheric currents.

- Literature:

- Example plots for a modeled case of a dark plasma vortex:

To illustrate the method, we use a model of a dark plasma vortex that moves eastward over the MIRACLE field of view with a velocity of 4 km/s. We assume that the vortex is stationary for the 2 minutes that it needs to pass over the central MIRACLE field of view. The model of the plasma vortex comprises the main results of a real event study of such an ionospheric feature that was recently conducted by Kosch et al. (JGR 105, 24889, 2000).

This is the input data: FAC distribution that CLUSTER II would observe during the 2 minutes when the vortex passes eastward over the MIRACLE array. The FAC data of the different timesteps is reduced to a central reference timestep with respect to the vortex's velocity (upper panel). The footpoints and conjugate magnetic field lines of the CLUSTER II satellites at the reference timestep are shown in the lower panel, for a typical pass over the central MIRACLE field of view.


Ionospheric electric field, as it would be observed by the STARE radar:

Output: 1.) True (not equivalent) ionospheric currents obtained by the "FAC-based" method of characteristics:

2.) Hall conductance distribution

and 3.) Pedersen conductance distribution:

For further questions and proposals of events to be analysed, contact Olaf Amm.

Maintained by: Olaf Amm
Latest update: 18.03.2004