The solar eclipse and its impact on cosmic radiation

12. 08. 2026

Today, we will be able to observe a solar eclipse. Although this is a visually spectacular astronomical phenomenon, its effect on the amount of cosmic radiation reaching Earth is rather marginal – cosmic radiation is, among other topics, studied at the Nuclear Physics Institute of the Czech Academy of Sciences. The Moon creates a tiny “shadow” in cosmic radiation by simply blocking some of the particles arriving from the direction of the Sun. However, the effect is so small that it can only be detected using large specialised detectors. This is because cosmic radiation reaches Earth not only from the direction of the Sun, but from the entire Universe.

From a physics perspective, the solar corona – the very tenuous and hot outer atmosphere of the Sun – is particularly interesting during an eclipse. Processes associated with solar activity take place in the corona and can influence space weather and, consequently, radiation conditions around Earth. Coronal mass ejections and their shock waves, for example, can accelerate particles to high energies. These particles can contribute to increased radiation exposure in space and, under certain conditions, at the altitudes at which commercial aircraft fly – environments whose radiation conditions are also studied by scientists from the Radiation Dosimetry Department at NPI CAS.

From the Czech Republic, only a partial eclipse can be observed, during which the solar corona will not be visible. Our colleagues Martin Kákona and Roman Dvořák from the Radiation Dosimetry Department have therefore travelled to two different locations in Spain to observe the total eclipse. In addition to observing the eclipse itself, they plan to test instruments that they normally use to study other phenomena. One of these is an electric field mill, a sensor used to measure the intensity of the static electric field.

A total eclipse also provides an opportunity to observe parts of the solar corona that are otherwise hidden by the bright solar disk. A similar principle is used by coronagraphs on space observatories. For example, the LASCO instrument aboard the SOHO observatory creates an artificial eclipse using an occulting disk, allowing continuous observation of the solar corona and coronal mass ejections. A natural eclipse has one advantage, however: it makes it possible to observe the inner parts of the corona that are obscured by the solar disk in a coronagraph.

If you would like to observe the eclipse yourself, remember to protect your eyes. Never look directly at the Sun, even when it is partially obscured or low above the horizon, without certified eclipse glasses or filters compliant with the ISO 12312-2 standard. A safe alternative is indirect projection, for example using a pinhole camera.

Image credit: NASA

The solar eclipse and its impact on cosmic radiation

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