PRESTO ALERT

:Issued: 2023 Mar 24 0818 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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A severe geomagnetic storm (G4) was registered with NOAA Kp reaching 7.7 in
the time interval 03:00 to 06:00 UTC on March 24th. The severe storm was
triggered by highly disturbed solar wind conditions due to an ICME arrival.
Most likely candidate is the partial halo CME related to a C4.4-class
flaring and consequent filament eruption in the north-east quadrant near
NOAA AR 3258 on March 20th. The severe storm was preceded by two major
storms with NOAA Kp reaching 6.6 and 7.3 and moderate storm before. Locally
in Belgium only minor and moderate storm levels were reached. Since early
UTC evening on March 23rd the interplanetary geomagnetic field registered
long periods with magnitude of approximately 20 nT and steady north-south
Bz component with value close to -16 nT. The solar wind speed has declined
over night with current value around 410 km/s. The interplanetary magnetic
field has declined to 10 nT at present with positive Bz at the time of
writing as the passage of the magnetic cloud related to the ICME arrival is
gradually coming to an end. Further moderate or minor storms remain
possible until the end of the ICME and more can be expected with the
anticipated arrival of a high speed stream and a possible glancing blow
later on March 24th.
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# Solar Influences Data analysis Center - RWC Belgium                #
# Royal Observatory of Belgium                                       #
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