It used to be called the "ether". This is a name that satisfied the curiosity of folk that believed there must be a physical medium (of some form) that allows radio waves to propagate.
Radio waves inherently propagate thru space as does light (also a radio wave) and this propagation is determined by the physical properties of free space. Those physical properties are: -
- Permittivity of free space at 8.8541878176 × 10−12 farads/metre
- Permeability of free space at 1.2566370614 × 10−6 henries/metre
Air slightly modifies these physical quantities by a fraction as it happens.
If you took these two units and multiplied them together, then took the square root you'd get this number: 3.335641 × 10-9.
If you then inverted this number you'd get a velocity: -
299,792,458 metres per second - that happens to be the speed of light.
The "ether" is what light and conventional radio waves travel thru and comprises "stuff" that was probably created in the big bang and happens to have, what we call, permeability and permittivity. It's beautiful.
Which parameter of air is enabling current to propagate through it?
Current doesn't pass thru air to form a radio (electromagnetic wave) - fields pass thru the air/vacuum/medium that are called the E-field and the H-field.
how electromagnetic wave move from one air atom to another?
They don't rely on atoms or molecules or matter - they are slowed down and reflected/distorted by matter - EM waves (if they had an opinion) would want a vacuum.