A faint partial halo CME was observed to the south-east in SOHO/LASCO-C2 data from March 21 16:00 UTC. This this CME appears to originate from a dimming that occurred near the central meridian around 15:45 UTC March 21. Initial analysis suggests this CME may have an Earth directed component and may impact Earth from early on March 24.

Solar flaring activity was moderate over the past 24 hours, with one M-class flare identified. The largest flare was a M1.2 flare (SIDC Flare 3887) peaking on March 21 at 15:58 UTC, which was associated with SIDC Sunspot Group 405 (NOAA Active Region 4028). This region has now started to show signs of decay. SIDC Sunspot Group 450 (NOAA Active Region 4036) has continued to rapidly emerge and is now the largest and most complex region on disk. SIDC Sunspot Groups 398, 436, 440 (NOAA Active Region 4021, 4025, 4031) are now all rotating over the west limb. Solar flaring activity is expected to be low over the next 24 hours, with C-class flares expected and M-class flares possible. A faint partial halo CME was observed to the south-east in SOHO/LASCO-C2 data from March 21 16:00 UTC. This this CME appears to originate from a dimming that occurred near the central meridian around 15:45 UTC March 21. Initial analysis suggests this CME may have an Earth directed component and may impact Earth from March 23. A CME seen in SOHO/LASCO-C2 data to the south-west from around 17:00 UTC March 21 was likely associated with the M1.2 flare. This CME is not expected to be Earth directed. The greater than 10 MeV proton flux as measured by GOES-18 increase slightly but remained below the 10 pfu threshold and is expected to remain so over the next days. The greater than 2 MeV electron flux, as measured by GOES-18, exceeded the 1000 pfu threshold briefly between March 22 19:30 UTC and 20:40 UTC but is expected to remain below the threshold during the next 24 hours. The 24h electron fluence was at normal levels and is expected to remain so for the next 24 hours.

In the past 24 hours the geomagnetic conditions reached moderate storm levels (NOAA Kp 6- on March 22 00:00-03:00 UTC). Geomagnetic conditions are expected to be at active to minor storm conditions on March 22 and 23, with further intervals of moderate storm conditions possible, due to the further ICME effects and the potential high speed stream arrival. The solar wind parameters reflected the ongoing passage of an ICME. The interplanetary magnetic field strength increases sharply on to reach a maximum value of 40nT at 17:42 UTC March 21. The Bz reached a minimum value of -22nT and was consistently negative for a sustained period between 22:30 UTC March 21 and 02:30 UTC March 22. The solar wind speed gradually increased from 380 km/s to a maximum of around 550 km/s on March 22 around 22:00 UTC. The solar wind speed then decreased gradually to values around 430 km/s by the end of the period. The solar wind speed and magnetic field are expected to continue to be slightly elevated on March 22, due to the waning ICME influence. Further enhanced solar wind speed is the possible from March 23 due to the CME of March 21 and the expected high-speed stream associated with the positive polarity coronal hole which began to cross the central meridian March 19.