Earth's atmosphere could be turned into a giant dark-matter detector

I am not understanding how a massive dark matter object travelling though Earth's atmosphere is expected to create an ion trail we could detect. I thought the only interaction between our atmosphere and whatever dark matter is would be through gravitational effects. This article seems to assume what are basically electromagnetic effects.
 
The arxiv preprint says:
"DM with a large cross section will lose energy via elastic scattering with atmospheric nuclei as it passes through the atmosphere. ... The struck nuclei recoil at velocities comparable to the DM velocity, subsequently losing energy by ionizing atmospheric atoms."
 
The arxiv preprint says:
"DM with a large cross section will lose energy via elastic scattering with atmospheric nuclei as it passes through the atmosphere. ... The struck nuclei recoil at velocities comparable to the DM velocity, subsequently losing energy by ionizing atmospheric atoms."

The problem I am having with that is how would "elastic scattering" occur from something that the theory of dark matter says does not interact with the atoms in our atmosphere (or anything else) by any force other than gravity. Gravity is such a weak force, I do not see it grabbing the electrons away from their atoms/molecules to create any ionization. Much more likely (but still highly unlikely) seems to be that the dark matter would gravitationally attract both the electrons and the atomic nuclei by about the same amount relative to their masses, accelerating them together in the same direction. And, I would expect that movement to be too tiny to observe in an otherwise turbulent gas.

Yes I know the "stratosphere" is "non-turbulent", at least as compared to the troposphere below it, but there is still a lot more motion than I would expect from the gravitational effects of even a softball sized piece of dark matter going through it at orbital speeds.) Think about what the gravitational effect of a softball is, trying to pull atoms towards it. Do we see any higher density of our atmosphere around objects the size of softballs, sitting on a table in our laboratories? No, we don't. So how much effect could we expect on the molecules in some atmospheric gas that are expose to a lump of dark matter that is only nearby for the instant it takes to pass at something like 17,000 miles per hour? In fact, why would dark matter even orbit, instead of just flying by Earth on a hyperbolic trajectory at escape velocity? Because dark matter is not supposed to interact with anything that causes frictional loses, it is hard to see how it would ever slow down.

Of course, the "theory of dark matter" may have some things wrong, so I can understand not excluding looks for plausible observations. But, this article does not seem to make a plausible argument for the effects they intend to observe. And, they have been observing regular matter meteors with their methods for decades, now. So, if they have not found any dark matter by those methods, yet, what exactly do they plan to do differently to look for it?
 
Yes, as I posted, the Dark Matter Theory may not have the "no interaction except by gravity" idea wrong to some degree.

Thanks for the link. But, so far, it just shows that no dark matter interactions have been detected with regular matter, and are not well inferred for self interaction, either. So, the net effect is to show that the probability of interaction (e.g., the "cross section") must be pretty small (if not zero) for most of the candidates we have thought of, so far.
 

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