Ephesians 2:2: Satan is the prince of the power of the air at this time and will be until he is defeated by CHRIST at His second coming. So yes, there are demons in the inter- dimensional part of our solar system.
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The ‘air’ is the first Heaven. Satan is in that Heaven (and it may extend across the entire solar system) but not the second Heaven and Third Heaven where the Throne Room of God is. When satan is cast down to the Earth, he will have been ejected ‘from heaven’, ejected from the first heaven.