As a plasma-based force field would simply feel really really hot and consuming end up burning anybody who touched it, a cold plasma-based force field would seem to be more in order. For convenience, cold plasma is when "where the temperature of the individual constituents is different from each other. Electrons are at higher temperature (more than 10,000K) and neutral atoms are at room temperature." So ignoring the engineering difficulties and energy requirements, the cold plasma forcefield wors by restraining a large volume of cold plasma, which might under other circumstances be a solid, possibly but not necessarily(it seems like it would be more effective if it was gas as it would contain more repulsive energy) under room temperature, by a higher power magnetic field, eg as much energy/power/electricity as it requires, and so presuming this is the case, ignoring any engineering difficulties What would it feel like to the touch and how would it behave?
Don't keep your hand in the gas
I assume that you're citing this: Summary
Your "forcefield" consists of a gas cloud, contained in a small area. It's a plasma because you've dissociated one or more electrons from each atom, which are now moving fairly freely.
The plasma itself will feel like a gas cloud like any other, since its atoms are at roughly room temperature. The electrons are at 20000K, and are probably prone to causing chemical reactions. This is indicated in the link, under "sterilisation".
The actual force-field in this scenario seems to be provided by your hypothetical containment unit.
To make this a barrier (as most force-fields are), you will need a pressure difference. This is more a function of your hypothetical containment unit, and is a question of mass-displacement causing a difference in pressure on either side of (say) your hand. So it will feel much like putting your hand on water, with the pressure scaled up appropriately. You will also feel heating from the free electrons transferring energy to your hand.
Under my assumptions about the containment device not affecting the toucher, the question you have asked is "What would pressurised nitrogen feel like to the touch?", plus a certain warmth.
Its ouch time.
- An acid burns by donating ions to its surroundings. These ions will try to share or rip electrons of(f) other materials.
- plasma is a substance so hot the electrons leave the atoms turning them into ions.
- as long as the plasma cannot reabsorb its electrons as it cools down it functions like a battery, storing its electrons until they have a way out.
So here's what will happen to the poor person who sticks his hand into the forcefield containing the plasma:
ions will happily try to bond with your hand like an acid. As you break the containment and complete a cirquit to the earth, all electrons in the plasma will force their way through your body to the ground causing electrical burns and possibly death if enough plasma is present.
If someone discovers your originally hot cold plasma, which is highly conductive, they would likely try to offer you a nobel prize for physics and revolutionize the world of electrics.