Some imagine that a comet is drawn by gravity of the Sun..this is only part of the momentum.
What is core to the momentum is Quantum particle jump...Negative Ions..Protons..
Here..the comet becomes Elecrtically active..which creates the *Jetting.
Comets can jet dramatically and change course...Marsden noted this.
Comets are tricky to ident...sometimes 50-80 data profiles must be complied to assay its course.
Recently..one comet was seen to be on a parabolic course...then the data pull showed it to be hyperbolic.
Shift
I was unaware that SOHO was down...its been effected before by Plasma burts from the Sun...They also shut it down I believe if its going to get fried!
Comet calculations are most difficult..ie the jetting which changes the comets direction.
Some cometary return calculations have been off by months and years..ie comets of short duration with known time windows.
Passing Jupiter and Saturn is thought to effect them..most probably true...as both Gas Giants heave a wopping amplitude of current off..
and as mention in another post..Comets become active near them....and begin to jet from the ellectrical interface.
Magnetic field lines are stronger at the central plain of the solar system.
A Comet on a hyperbolic course will speed up as it nears the central plain....then be reduced in acceleration as it crosses out of the central plain.