As the comet accelerates toward the Sun electrons begin to be stripped from the nucleus like a "cold-cathode". It develops a visible glow discharge and Birkeland current tail. These electrical effects we call a comet. At some point, more powerful arcs strike on the comet nucleus and give rise to "cathode-jets" which move about and burn circular craters. The electrical discharges to a cometary cathode will follow the magnetic field lines in the vicinity of the comet. So it will be interesting to compare the jet directions with the solar wind field direction which, because it spirals out from the Sun, does not coincide with the comet-Sun line. There is no "shock wave" to be understood in the usual sense. A charged body in the plasma of space will form a sheath to protect itself from its electrical environment. The boundary of the comet's coma defines the virtual anode region of a plasma glow discharge. Electrons are accelerated outward and positive ions inward across the sheath. Strong X-rays are generated where these particles recombine.
At the Electric Universe website are articles on how the Suns Plasma emmisions effect the Earths magnetic field.
A comet on approach..perihelion and outleg causes the Sun to throw off Plasma's..which lace the inner planets and effect their fields..if they have one.