Synopsis: A Crack in Earth’s Protective Shield

Observations with India’s cosmic-ray telescope indicate that Earth’s magnetic field weakened during a 2015 geomagnetic storm, allowing cosmic rays to pass through.
Synopsis figure
S. K. Gupta/Tata Institute of Fundamental Research

In the early hours of June 21, 2015, a giant cloud of magnetized plasma was ejected from the Sun in a solar flare. Forty hours later, those particles slammed into Earth’s magnetosphere, triggering a severe geomagnetic storm that knocked out radio signals in North and South America. New observational data from the GRAPES-3 cosmic-ray telescope in India show that an unusually high flux of cosmic rays breached the magnetosphere during this storm, resulting in a 2-hour-long cosmic-ray shower on Earth. Simulations performed by the GRAPES-3 collaboration, which includes researchers from India and Japan, suggest that the burst of cosmic rays was allowed to enter because the geomagnetic storm temporarily weakened Earth’s polar magnetic field.

Earth’s magnetic field deflects most cosmic rays, protecting living things from harmful radiation. But large geomagnetic storms can reconfigure this protective shield, opening up weak spots that let radiation and cosmic rays slip through. This vulnerability can occur when magnetized plasma from the Sun deforms Earth’s magnetic field, stretching its shape at the poles and diminishing its ability to deflect charged particles. Numerical simulations performed by the GRAPES-3 researchers suggest that this is exactly what happened following the June 21 solar flare, allowing the cosmic-ray breach that their telescope detected.

This research is published in Physical Review Letters.

–Katherine Wright

Katherine Wright is a Contributing Editor for Physics.


More Features »


More Announcements »

Subject Areas


Previous Synopsis

Next Synopsis

Semiconductor Physics

Valley of the Dichalcogenides

Read More »

Related Articles

Synopsis: Cosmic Voids Under Pressure

Synopsis: Cosmic Voids Under Pressure

An analysis of distortions in the cosmic microwave background reveals information about the gas inside large voids in space. Read More »

Viewpoint: Intermittent Turbulence in a Global Ocean Model

Viewpoint: Intermittent Turbulence in a Global Ocean Model

A large-scale model of ocean dynamics finds intermittent behavior that may have implications for how the ocean’s energy budget is assessed. Read More »

Synopsis: Intel on Stellar Element Production from Accelerator Data
Nuclear Physics

Synopsis: Intel on Stellar Element Production from Accelerator Data

Measurements of a nuclear reaction relevant to the synthesis of calcium, potassium, and argon in stars boost the accuracy of models for predicting the elements’ abundances. Read More »

More Articles