Can an EMP be caused by a meteor? I am no scientist, but I'm doing some research about asteroids and their ability to cause an electromagnetic pulse (EMP) through their impact. I found these very helpful lines on this site:

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*What size asteroid would cause a nuclear explosion?

The fireball and the blast wave are caused by the meteorite's kinetic energy being converted to heat. This converts the meteorite and some of the surrounding rocks in the Earth to a gas, but its initial density is the same as what it was before the impact. From the gas law you can see that this means that the pressure must be extremely high. This causes the gas to expand very fast, giving rise to the blast wave and the fireball. The electromagnetic pulse is caused by the extremely high temperatures of the fireball"

followed by a detailed explanation of how this works.
But so far I did not find something similar on the internet, some publication or scientific article that does explain and prove that — and under which conditions — an EMP can be caused by a meteor's impact.
I would be very grateful for any kind of hint.
 A: Not likely.
As far as we know, the nuclear EMP happens because of high-energy photons (gamma rays) interact with atmosphere molecules, creating high-energy charged particles, that in turn interact with the Earth's magnetic field.
A meteor has no (known to me) means to emmit intense gamma rays. Their emission is more or less thermal and the temperature of the trace is related to the speed the body enters the atmosphere. These speeds are in the order of magnitude of the solar system's orbital speeds, i.e. few tens of km/s at most. In temperature units it is few thousands or tens of thousands K with corresponding maximum at or near the visible range. Some UV is present, X-rays or gamma rays are out of question.
That's why it cannot create EMP by the same mechanism.
The mechanism suggested by @niels nielsen in his answer can create an EMP of order of magnitude of a lightning. Still an impressive feat, but only that much.
A: The electromagnetic pulse produced by nuclear explosions has several components Wikipedia: Nuclear electromagnetic pulse. The E1 and E2 parts are produced by gamma rays which will not be produced by a meteor. However, plasma from a meteor explosion may distort geomagnetic field lines, producing an effect like the slow E3 component.
A: From the top to the bottom of the atmosphere, there is a voltage gradient of about 100 volts per meter. The penetration of the atmosphere by a meteor heats the air through which it is passing to incandescence, thereby ionizing it and rendering it electrically conductive. The conductivity of the meteor trail short-circuits the voltage difference between the upper layers of the atmosphere and the lower layers, allowing the very sudden flow of electrical current between them, creating the EMP.
