When solar magnetic fields balance, the corona flips between one and two current sheets over days.

The Sun blows out a stream of particles called the solar wind. It carries magnetic fields that meet at a boundary called the heliospheric current sheet, which divides regions of opposite magnetic direction. Usually, the Sun acts like a two-pole bar magnet and creates a single sheet. But if that main field weakens, a four-pole magnetic setup can create two sheets instead. Scientists wanted to see how the Sun shifts from one sheet to two. They ran computer simulations of the solar wind, changing the balance between the two-pole and four-pole fields. They found that shifting this balance creates a huge loop of trapped magnetic field called a pseudostreamer. When both magnetic fields have roughly equal strength, the Sun's atmosphere can flip back and forth between having one sheet and two sheets over days-to-weeks. The loop opens up, creating a new coronal hole and a second sheet.

Why it matters

This affects predictions of space weather, which can disrupt satellites and power grids. Understanding these shifts helps explain how the sun's magnetic structure evolves over its cycle.

Questions answered