Can be the ionosphere described as an elecro-magnetic field? I read that the ionosphere can be defined as plasma.


*

*it has its plasma frequency

*it has its Debye length

*it is overall neutral


As it is overall neutral it does not produce any electric field.

However, as far as I know, a force field is an area in which a particle is an object of force.
A signal (or an electron) that travels through the ionosphere changes its speed and trajectory and these changes are caused by the charged particles in the ionosphere, thus, the forces are of electro-magnetic nature.
Maybe I should ask: can be a plasma defined as a electro-magnetic field, and at which conditions?
 A: Let's make this answer a community wiki because I know I'm not going to end up giving it the full explanation it's due.
I'm going to go out on a limb and say no, a plasma can not be defined as an electromagnetic field (at least a conventional plasma cannot, a photon plasma might be able to. Maybe someone could speak about that). A plasma is a matter fluid. One could say that because the particles within the fluid are ionized, there are relatively stronger electromagnetic fields and forces in the locality of the plasma, but the fluid itself is not a field.
The ionosphere being neutral means it wouldn't produce an external electic field; it still could have internal electric fields. One could say that the ionosphere is a region of increased electromagnetic turbulence relative to the electromagnetic fields in adjacent regions. However, an EM field should be regarded more as a universally present medium through which photons (radiation & EM forces) travel, whereas the ionosphere and/or plasma is a locally defined object composed of matter with boundaries.
Short answer: the ionosphere or plasmas (plasmae?) in general are matter clouds that have electromagnetic fields/forces in them due to the higher density of charged particles; however, they would not be defined as EM fields.
I'll now ask that anyone able to change and/or improve this do so. And feel free to remove all my non-answer-relevant comments.
A: The ionopsphere supports an electromagnetic field - Schumann resonance - curiously coincident with human EEG bands (7.8, 14, 20, 26, 33, 39 and 45 Hz),
http://en.wikipedia.org/wiki/Schumann_resonances 
http://www.backyardastronomy.net/schumann_resonance.html 
