A partial halo CME with angular width around 150 degrees was first seen erupting towards the NW by LASCO-C2 at 09:48 UTC on 24 September. This CME is backsided and not expected to affect the Earth.

A halo or partial-halo CME was detected with the following characteristics: t0 | dt0| pa | da | v | dv | minv| maxv| 2023-09-24T09:36:07.402 | 4.0 | 296 | 150 | 367 | 133 | 123 | 710 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 moderate levels. The largest flare was a M1.3-flare, with peak time 09:07 UTC on September 28. This flare was associated with NOAA AR 3450, which rotated over the eastern limb and has been the most active region in the last 24 hours. There are currently 7 numbered active regions on the visible disk. NOAA AR 3445 (beta) has decayed and NOAA AR 3449 (beta-gamma) has grown in size, all other regions have simple alpha or beta magnetic field configurations. The solar flaring activity is likely to be at low levels over the coming days with C-class flares expected, M-class flares possible and a low chance for isolated X-class flaring. No Earth directed CME’s have been detected in the last 24 hours. A CME was seen erupting towards the north-east in LASCO-C2 data from 11:12 UTC on September 27 this is determined to be back-sided and is not expected to impact the Earth. A positive polarity coronal hole began passing the central meridian on September 27 in the northern hemisphere. The greater than 10 MeV proton flux was at background level over the last 24 hours and is expected to remain so in the next 24 hours. The greater than 2 MeV electron flux measured by GOES-16 went above the 1000 pfu threshold value between 12:00 UTC and 17:50 UTC on September 27. The greater than 2 MeV electron flux is expected to increase above the threshold again in the next 24 hours. The 24h electron fluence became elevated going towards moderate levels and is expected to remain at moderate levels in the next 24 hours.

The geomagnetic conditions over the past 24 hours were unsettled globally (Kp 3) and locally (K Bel 3). Quiet to unsettled conditions are expected in the next 24 hours. In the last 24 hours, the interplanetary magnetic field fluctuated between 2 nT and 6 nT and the Bz fluctuated between positive and negative values going down to – 5 nT. The solar wind speed had values varied between 360 km/s and 535 km/s. The phi-angle was mainly in the positive sector (directed away from the Sun). Slow solar wind conditions are expected in the next 24 hours with a possibility of a slight enhancement on the 28 September due to a filament eruption on September 25.