Eta Carinae is a unique massive binary star system in our Galaxy, presenting some basic undetermined
parameters and open questions. Its 5.54 year periodicity in a very
eccentric orbit is observed in all wavelengths.
We identify the important physical processes that we expect to take
place at periastorn passage, and use these to explain observations.
In particular, we show that mass accretion onto the companion is
expected to occur, and might explain some basic observations.
For example, the accreted mass possesses enough angular momentum to
form a thick disk, or a belt, around the secondary, and shut down the
secondary wind for about ten weeks. After periastron the belt dissipates as
its mass is blown away by the reestablished secondary wind.
We also study the wind collision in detail, and come up with
straightforward explanations to some key observations, like Doppler
shifts, X-ray absorption, and the absorption of the He I 10830 lines.
