Strong geomagnetic storm (G3) was registered globally on April 19th with NOAA Kp reaching 7 in the interval between 18:00 and 21:00 UTC. The geomagnetic storm was triggered by enhanced solar wind conditions likely due to the arrival of a partial halo CME which lifted off the solar surface on April 15th, possibly combined with an expected CIR in front of a high speed stream arrival. Locally over Belgium, only minor geomagnetic storm conditions were observed (K-Bel = 5). Further minor to moderate storm conditions may be expected in the coming hours.

A halo or partial-halo CME was detected with the following characteristics: t0 | dt0| pa | da | v | dv | minv| maxv| 2024-04-16T10:24:07.520 | 1.0 | 236 | 178 | 1690 | 182 | 1358 | 2011 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 was at moderate level, with multiple C-class flares and three M-class flares recorded in the past 24 hours. The largest flare of the period was an M2.1 flare, peaking at 04:53 UTC on Apr 19, associated with NOAA AR 3647 (beta-delta class). This region was the main driver of the flaring activity observed over the past 24 hours together with NOAA AR 3645 (beta class). Low flaring activity was also produced by NOAA AR 3635 (beta class) and NOAA AR 3639 (beta-gamma class). Other regions on the disc have simple configuration of their photospheric magnetic field (alpha and beta) and did not show any significant flaring activity. The solar flaring activity is expected to be at moderate levels over the next 24 hours, with M-class flares possible and a chance for X-class flare. Multiple CMEs, directed towards south-east from the Earth's perspective, were observed in SOHO/LASCO-C2 starting from approximately 17:16 on Apr 17, likely related to the flaring activity from NOAA AR 3638 and 3643. While bulk of the CME is off the Sun-Earth line, a glancing blow from these CMEs could be possible on Apr 21 - 22, although with low confidence. Over the past 24 hours the greater than 10 MeV GOES proton flux was at nominal levels and is expected to remain so with possible enhancements in case of increased levels of solar activity over the next days. The greater than 2 MeV electron flux, as measured by the GOES-16 satellite, remained below the 1000 pfu threshold. It is expected to remain below the threshold during the next 24 hours. The 24 hour electron fluence was at normal levels and is expected to remain at these levels for the following 24 hours.

The geomagnetic conditions over the past 24 hours were quiet to active globally (NOAA-Kp=1-4). Locally only quiet to unsettled(K-Bel=2-3) conditions were observed over Belgium. Mostly unsettled to active geomagnetic conditions are expected for the next 24 hours, with a chance of reaching minor storm levels due to ongoing ICME influence and expected HSS arrival. At the beginning of the period, the solar wind parameters were reflecting return to slow solar wind conditions. The solar wind speed decreased from the values about 360 km/s to 310 km/s; the total interplanetary magnetic field was below 5 nT. The solar wind conditions became slightly disturbed from around 04:12 UTC on April 19, with the total interplanetary magnetic field reaching the values up to 16 nT. The southward component of the interplanetary magnetic field fluctuated between -12 nT and 5 nT. This is probably associated with the arrival of a faint partial halo CME observed on Apr 15. The solar wind conditions are expected to remain slightly elevated due to the ICME passage with a chance of a further weak enhancement late on Apr 20 - Apr 21 due to the arrival of a high-speed stream from a negative polarity coronal hole, that started to cross the central meridian on Apr 17 and a possible ICMEs arrival.