March 28, 2019: Close your eyes and relax. Daydream about something pleasant. In this state your brain is filled with “alpha waves,” a type of electrical brainwave associated with wakeful relaxation.

Now try it during a geomagnetic storm. It may not be so easy. A new study just published in the journal eNeuro by researchers at Caltech offers convincing evidence that changes in Earth’s magnetic field can suppress alpha waves in the human brain.

Researchers have long known that living creatures can sense magnetic fields. For instance, honeybees, salmon, turtles, birds, whales, and bats use the geomagnetic field to help them navigate, and dogs can be trained to locate buried magnets.

“Many animals have magnetoreception, so why not us?” asks Connie Wang, Caltech graduate student and lead author of the eNeuro study.

To find out if humans can indeed sense magnetic fields, the researchers built an isolated radiofrequency-shielded chamber where participants sat in utter darkness for an hour. As magnetic fields shifted silently around the chamber, participants’ brain waves were measured using electrodes positioned at 64 locations on their heads.

In some of the 34 participants, alpha brainwaves decreased in power by as much as 60 percent in response to the shifting fields. Additional runs of the experiment showed that the effect was reproducible.

Study co-authors Joseph Kirschvink and Shin Shimojo say this is the first concrete evidence of a new human sense: magnetoreception.

Remarkably, participants who experienced the changes reported no awareness of them. It appears to be a completely unconscious effect, never rising to the level of a conscious interruption. This led the researchers to suggest it may be vestigial, some remnant of an ancient ability to navigate using local magnetic cues.

“It is perhaps not surprising that we might retain at least some functioning neural components [of magnetoreception], especially given the nomadic hunter-gatherer lifestyle of our not-too-distant ancestors,” says Kirschvink.

“As a next step, we ought to try bringing this into conscious awareness,” adds Shimojo.

Does this mean people may be able to sense geomagnetic storms? It’s unclear.

When coronal mass ejections (CMEs) and streams of solar wind reach Earth, they cause our planet’s magnetic field to shake, moving back and forth. During the Carrington Event of Sept. 1859, for instance, compass needles at mid-latitudes swung back and forth by several degrees (ref). The Caltech study didn’t look at such small changes, however. Magnetic fields inside their test chamber shifted plus or minus 90 degrees at least. As a result, we do not yet know if human magnetorecepton is sensitive enough to detect the more subtle changes typically associated with space weather.

By developing a robust methodology for testing magnetoreception, Kirschvink says he hopes their study can act as a roadmap for other researchers who are interested in replicating and extending this research. “The full extent of [magnetoreception] remains to be discovered,” he says.

The original research may be read here.