Cosmic rays are charged particles that reach us from distant stellar explosions. But before hitting a detector, they must pass through the bubble of the solar wind. The Sun breathes: it inflates this bubble, then contracts it. Particles have to fight through a changing magnetic field, like a swimmer against a current that alternately strengthens and weakens.
Scientists took data from the AMS-02 detector on the International Space Station over an entire 11-year solar activity cycle. They tested how well different models describe the way the Sun distorts the particle flux. The simple model, like a current map that ignores obstacles, worked only in quiet years and only for positively charged nuclei. For antiprotons, it was wrong at all times.
Errors pile up: in the end, scientists get a cosmic ray map shifted by 10–15%. It's like measuring a river's depth without knowing that the water level changes with the seasons. To see the true picture, observations spanning a full 22-year cycle are needed — then the Sun's breathing can be separated from distant sources.
Antiprotons are rare visitors: there are a million times fewer of them than ordinary protons, but they are precisely the ones sensitive to the direction of the Sun's magnetic field.