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.

A halo or partial-halo CME was detected with the following characteristics: t0 | dt0| pa | da | v | dv | minv| maxv| 2023-03-20T16:06:07.807 | 2.0 | 349 | 220 | 653 | 709 | 348 | 1986 t0: onset time, earliest indication of liftoff dt0: duration of liftoff (hours) pa: principal angle, counterclockwise from North (degrees) da: angular width of the CME (degrees), v: median velocity (km/s) dv: variation (1 sigma) of velocity over the width of the CME mindv: lowest velocity detected within the CME maxdv: highest velocity detected within the CME

Solar flaring activity over the past 24 hours was at very low to low levels with only two low C-class flares from NOAA AR 3259 (beta). NOAA AR 3260 (beta) had developed new trailing spots, but remained inactive. NOAA AR 3257 (alpha) has shown some decay. The remaining two active regions on the visible disc, NOAA AR 3256 (beta) and NOAA AR 3262 (beta) are also relatively simple and did not show any significant evolution, nor flaring activity. Very low to low levels of solar flaring activity are expected over the next 24 hours. No Earth-directed coronal mass ejections (CMEs) have been detected in the available coronagraph imagery. The greater than 10 MeV GOES proton flux was at nominal levels over the past 24 hours and is expected to remain so in the next 24 hours. The greater than 2 MeV electron flux has been below the1000 pfu threshold and is expected to remain under the threshold under the declining influence of the ICME arrival. The 24h electron fluence was at nominal levels and is expected to remain so over the next 24 hours.

Over the past 24 hours the solar wind parameters (ACE and DSCOVR) were highly disturbed under the influence of a ICME arrival with prominent magnetic cloud. The most likely candidate for this ICME 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. A CIR and a high speed stream (HSS) from a negative polarity coronal hole were also expected during the time of the ICME arrival and could have been partially mixed with the CME on its way towards the Earth. The solar wind velocity was at slightly elevated levels, varying in the range of 402 to 513 km/s. The interplanetary magnetic field (B) reached a peak value of 22 nT around 14 UTC on March 23rd. Since early UTC evening on March 23rd the B field registered long periods with magnitude of approximately 20 nT and steady north-south, Bz component, with values close to -16 nT. The lowest negative Bz measurements reached -17.5 nT. The B field remained predominantly in the positive sector (directed away from the Sun) with recent short periods in the negative sector. The B field magnitude declined to 11 nT at present with Bz equals to -4 nT at the time of writing with the diminishing influence of the ICME. The solar wind parameters over the next 24 hours are expected to remain enhanced due to the ongoing ICME and with the expected high speed stream (HSS) arrival. Minor chance for a glancing blow from the March 21st CME remains with possible arrival time in the late evening of March 24th. If this ejecta arrives it will be mixed within the expected HSS and might be difficult to resolve within the data. The geomagnetic conditions over the past 24 hours registered severe storm levels with NOAA Kp index reaching 7.7 in the time interval 03:00 to 06:00 UTC on March 24th. The severe storm was preceded by two major storms with NOAA Kp reaching 6.6 and 7.3 and a moderate storm before. Locally in Belgium only minor and moderate storm levels were reached with K Bel reaching 6 for prolonged intervals after UTC midnight on March 23rd. The geomagnetic storms were triggered by the highly disturbed solar wind conditions due to the ongoing ICME arrival. The geomagnetic conditions over Belgium have currently declined back to unsettled levels, while global conditions register active levels after another major storm. Chances for more severe of major storms are decreasing, but further moderate and minor storms remain possible due to the ongoing ICME and the anticipated arrival of a high speed stream and a possible glancing blow from the March 21st CME.