The story is told from the POV of an astronaut who, along with his crew, is launched into orbit to investigate a weird phenomena that has entered local space. Several enormous fields of darkness, probably alien beings (not sure if that is initially understood) are floating near Earth. I'm not sure if they have encircled the Earth at the beginning of the story, or if they move into position after the spaceship has attempted to investigate them.
While encircling the planet, Earth is in total communications blackout with the protagonist and the other astronauts. During this time, the Sun emits a massive solar flare. Tremendous amounts of energy and radiation hurtle towards Earth. It would be a disaster for the planet, but the aliens' nature blocks the incoming energy, saving the planet and everyone on it.
Unfortunately for the astronauts, their spacecraft is not spared the effects of the flare. They absorb lethal doses of radiation and heat, leaving them debilitated and dying. As the alien beings move off, the protagonist, too weak and injured to respond to hails or reply, realizes the people of Earth will never know that the aliens came as saviors. Instead, they will likely blame the aliens for his death and the death of the other crew in the spaceship. The story closes with the protagonist's thought that man will one day seek vengeance on the creatures, thinking them murderers instead of saviors.
Timeframe of Publication
Older story, for sure. I'd guess 50's or 60's, based upon the premise and style of the writing. Might be older than that.