Sidhartha,
I think that the "aereal waters" of the Rig Veda description, that flow downwards, could be ethereal flows from celestial realms higher up towards the Pole Star, and that solidify into physical water when they reach the physical realm.
In the Vedic literatures, we read of celestial beings that appear through fire which has been made "soft" like the light of the Moon and which doesn't burn; and this is attributed to exposure to the mantras/frequencies that were vibrated through the threads that the brahmin chanters wore. The celestial being would walk out of the fire and his ethereal body would essentially solidify upon exposed to the Earthly atmosphere. But the physical bodies of the celstials and their celestial neurological systems apparently maintained their superior development from the celestial realms. And they would copulate with warrior caste women to also produce superior human warriors, but not quite the same as them. This is exactly what Plato explained; that the celesttial Poseidon came and improved the bloodlines, but after generations of dilution, common human qualities made their appearance again, and the Atlantean kings became sinful.
Anyway, the celestial/ethereal waters could solidify upon entering the Earth's atmosphere or the hollow earth environment.
If there are magnetic ropes that connect even Saturn - which is very, very far off - with The Sun, then there can be particle flows that originate from way up above us, in the direction of the Pole Star, and that reach the Earth.
And from the Rig Veda statement, it seems that the celestial, ethereal flow turns into water. Remember, from the subtle elements come the grosser, physical elements: from ether comes air then fire then water then finally earth/physical matter. The ethereal flows pass through air, so why wouldn't they take on the nature of air? When the celestial warriors that have been called upon pass through the fire and step out into the physical realm, their bodies take on physical qualities. So the celestial flows should pass to a physical airy state, then to a fiery state. We already know that higher frequency particles, such as gamma, burn when they pass through the Earth's physical realm. But then they should follow the sequence and pass into a watery state.
I think that, although all possibilities must be considered, we should try to justify the frank statements of the Vedas. It is just that, at the moment, our knowledge of particle physics suffers from severe paucity. And then nobody can imagine how a celestial river can flow through space.
Cheers!