:Issued: 2026 May 16 0845 UTC
:Product: documentation at http://www.sidc.be/products/presto
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# FAST WARNING 'PRESTO' MESSAGE  from the SIDC (RWC-Belgium)         #
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Moderate geomagnetic storm conditions (NOAA Kp = 6 + ) were observed between 21:00
UTC on May 15 and 00:00 UTC on May 16. Locally, several intervals of minor storm
conditions were observed, with K BEL reaching 5. This activity is associated with the
arrival of the high-speed solar wind stream from the large, negative polarity
transequatorial coronal hole (returning SIDC Coronal Hole 147), which started to
cross the central meridian on May 13. Solar wind conditions showed a significant
enhancement, with the solar wind speed increasing up to approximately 810 km/s. The
interplanetary magnetic field reached up to about 17 nT, while the Bz component
reached values down to -11 nT. Active to minor storm conditions may persist over the
next 24 hours due to the continuous influence of the high-speed stream and depending
on the evolution of the interplanetary magnetic field, particularly the Bz
orientation.
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# Solar Influences Data analysis Center - RWC Belgium                #
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