The Heliosphere and Galactic Cosmic Rays

  • Released Friday, August 22, 2025
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Surrounding our solar system is a giant protective bubble created by particles and magnetic fields from the Sun called the heliosphere. Every 11 years, the Sun’s activity ramps up and down in what’s known as the solar cycle. As the Sun reaches its peak activity level, called solar maximum, the heliosphere expands. During this time, the heliosphere’s protective shield is strengthened by the increase in particles and magnetic fields from the Sun. As a result, fewer damaging particles from the galaxy, such as galactic cosmic rays, are able to penetrate into the heliosphere. As the Sun ramps down into a low level of activity, called solar minimum, the heliosphere shrinks and more cosmic rays are able to enter the heliosphere.

Conceptual Animation

As the heliosphere expands with the natural 11-year solar cycle, the number of galactic cosmic rays that penetrate the heliosphere decreases. As the heliosphere shrinks, more galactic cosmic rays can penetrate the heliosphere.

Credits

Please give credit for this item to:
NASA's Goddard Space Flight Center Conceptual Image Lab

This page was originally published on Friday, August 22, 2025.
This page was last updated on Wednesday, August 6, 2025 at 2:49 PM EDT.