What is a magnetic flux rope and how does it differ from magnetic flux tubes? I am currently taking a course on solar physics and it appears the terminology in solar physics is either needlessly verbose or I am just missing something.  What is a flux rope and what is a flux tube?  How are they different?
I know this is a (very) basic question but there isn't a great deal of documentation from what I can tell.  Thanks in advance for any help!
P.S.  Is it fair to say that the differential rotation is the cause of all of the effects within solar physics ultimately?
E.g. the twisting of a magnetic loop ultimately leading to a CME.  Is this twisting from the differential rotation or from the influence of the current in the loop upon itself?  
 A: The difference lies in the topology of the magnetic field. While a flux tube involves, as honeste_vivere pointed out, a region in space with constant magnetic flux, a flux rope involved a twisted magnetic field line that contains (from Ampere's law) a flowing current.
In that sense, flux tubes are a theoretical concept used to study the transport of plasma within large structures such as magnetospheres, while flux ropes are more like physical entities that store magnetic energy that can, eventually, be released in the form of an eruption (although, as far as I know, the origin of CMEs is still debated).
A: A flux rope involves some twisting, and so has the nice physical interpretation of a current flowing along the magnetic field. The limiting case would be a flux tube with no twist within it; this is not very physical but looks like what we often see in solar images.
A: Flux tubes are isolated concentrations of magnetic field found in the solar convection zone. There have been various studies with untwisted magnetic flux tubes with not much success. For a flux tube to rise from the convection zone, thus leading to formation of sunspots, it requires that the flux tube is twisted. 
Flux ropes, on the other hand, are long outstretched series of magnetic field loops as observed on the solar corona.
