I think this is The Sunborn by Gregory Benford.
This is a novel rather than a story, but it sort of matches much of your description. In the book life is discovered on Pluto and magnetic beings inhabiting the Oort cloud. There is a galactic storm, or something like it, that will push the heliopause in to about Saturn's orbit and the magnetic beings can prevent this by feeding on the storm.
And as the mission had prepared, a further, ominous puzzle arose: the solar system's bow shock was moving. This "pause point" is the working front where the sun's outward wind of particles meets the interstellar plasma. This forms a surface much like the curve made by a ship powering across a lake, seen from above. Before, the nearest this bow shock had gotten to the sun was about one hundred astronomical units, a full hundred times farther than the Earth-sun distance. But now that fluttery front lay only a few AU beyond Pluto, now just a tad beyond 40 AU from the sun.
If the solar wind let that wall of molecular hydrogen behind the shock intrude into the inner solar system, Earth could be destroyed. Even approaching partway in, say into Saturn, would be very dangerous. That seemed unlikely to the specialists, but without an explanation of what was happening beyond Pluto, few found that comforting.
Looking at the comments in Worldbuilding I note there is reference to something called a sinew, and this would be:
Most Beings knew how to skirt the worst of it, skating the edge while absorbing magnetic whorls and digesting them into stronger fields within themselves. They valued the helicity above all, the twisted fields that carried the tight strands like rubber bands, that enabled a Being to confine itself. Sinew gave strength.