The Sun can produce powerful storms at minimum activity


Our Sun is regularly shaken by powerful eruptions. Generally, they occur at the time of its peak activity or in the decay phase. But in 1903, it was at full minimum that one of the most powerful solar storms in modern history was triggered. Under conditions very similar to those we know today …

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[EN VIDÉO] Fly over the fantastic storms of our Sun
The activity of the Sun during the year 2013 told in images and music, thanks to a compilation of observations from the Soho probe. Taken in several wavelengths (translated by different colors), these images show protuberances, solar flares and spots. © Nasa Goddard

L’sun activity varies on average over an eleven-year cycle. And generally our star experiences more violent eruptions during peak phases or decay phases. The storm recorded in 1903, however, occurred during the calmest phase of the solar cycle. One of storms strongest solar cells in the modern history of Terre. It is now described in detail in a study byJapanese astronomers.

During the last week of October 1903, at the height of minimal activity, a new stain appeared on the Soleil. And when the eruption occurred on October 30, this sunspot directly facing the Earth. A bit like AR2767, the one that appeared on the Sun a few days ago and under the same circumstances. But at that time, no satellite to measure the intensity of the eruption. Only testimonies of the astonishing effects of this storm.

Lots of testimonials and a few measures

In Chicago (USA), for example, the tensions in the telephone lines reached 675 volts. “Enough to kill a man”then headlined the newspapers. In London, telegraph operators were no longer able to send messages. The aurora australis has been seen as far as New South Wales, Australia. As to northern Lights, they surprised the residents of Colorado who reported seeing “Rays of light beautiful and cold ”.

However, a few instruments have been able to measure variations in earth’s magnetic field. Enough to allow astronomers estimate your DST – for Disturbance storm time. This index measures the magnetic disturbance due to solar storms at low latitudes. The more negative its value, the moreenergy accumulated is important. Thus the DST of storms considered to be intense reaches -100 nanoteslas (nT). The DST of the 1903 solar storm is now estimated at -531 nT!

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