Our solar system is situated (by chance) in a smaller spiral arm, called the Local or Orion Arm, sometimes labelled "0". This small or intermediate arm connects the more substantial next inner arm and the next outer arm. The next inner arm, sometimes labelled "-I", is called the Sagittarius or Sagittarius-Carina Arm, the next outer arm, labelled "+I", is the Perseus Arm. Since our solar system is located in the Orion arm, it will leave this arm in about two hundred million years. It takes the solar system about 225-250 million years to complete one orbit and so is thought to have completed about 20-25 orbits during its lifetime or .0008 orbit since the origin of man. The orbital speed of the solar system is 217 km/s. http://hypertextbook.com/facts/2002/StacyLeong.shtml Would the Sun in particular experience any annomalies with relation to it's proximity when moving towards these arms?
Like a cloud very close up there is actually very little in the Orion arm when you get down to our level. But at a distance: http://www.atlasoftheuniverse.com/5000lys.html The arms distort over time because the parts move at different speeds, even allowing for their distance from the centre.
