Eu acho que isso é The Sunborn por Gregory Benford .
Este é um romance em vez de uma história, mas corresponde muito à sua descrição. No livro, a vida é descoberta em Plutão e seres magnéticos que habitam a nuvem de Oort. Há uma tempestade galáctica, ou algo parecido, que empurrará a heliopausa para a órbita de Saturno e os seres magnéticos podem impedir isso se alimentando da tempestade.
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.
Olhando para os comentários no Worldbuilding, noto que há uma referência a algo chamado sinew , e isso seria:
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.