=================================== Weekly Space Weather Highlights =================================== Highlights of Solar and Geomagnetic Activity 20 - 26 September 2021 Solar activity was at very low to moderate levels. Region 2871 (S27, L=357, class/area=Dao/310 on 21 Sep) produced the largest flare of the period, an M2/1n flare at 23/0444 UTC. Associated with the flare was a Type II radio sweep (966 km/s) followed by a Type IV radio sweep. A subsequent CME signature was observed in SOHO/LASCO C2 coronagraph imagery. Analysis and modeling of the event suggested most of the ejecta was away from the Sun-Earth line but a glancing blow from the periphery of the CME may be possible on 27 Sep. An additional M1/1n flare was produced by the same region at 23/1528 UTC. A subsequent CME signature associated with the event was also analyzed with a similar potential for the periphery of the ejecta to influence Earth around 27 Sep. Other activity included a Type II radio sweep (739 km/s) associated with an eruption around Region 2875 (S32, L=053, class/area Bxo/010 on 24 Sep). The associated CME signature was narrow and directed away from the Sun-Earth line. Most numbered active regions were in decay and they transited through the W hemisphere with most decaying to plage by the end of the period. The remaining numbered regions in the E hemisphere were relatively simple and quiet. No proton events were observed at geosynchronous orbit. The greater than 2 MeV electron flux at geosynchronous orbit was at normal to moderate levels throughout the reporting period. Geomagnetic field activity ranged from quiet to active levels. Active levels were observed on 22 Sep in response to a SSBC followed by influence from positive polarity CH HSS. Unsettled conditions were observed on 21 Sep, and 23-25 Sep due to coronal hole activity. The remainder of the reporting period was quiet. Forecast of Solar and Geomagnetic Activity 27 September - 23 October 2021 Solar activity is expected to range from very low to low levels. Low levels are likely on 27-29 Sep and very low levels are likely for the remainder of the outlook period. No proton events are expected at geosynchronous orbit. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach moderate to high levels. High levels are likely on 29 Sep - 02 Oct, 05-08 Oct and 20-21 Oct due primarily to influence from multiple, recurrent CH HSSs. Normal to moderate levels are expected for the remainder of the outlook period. Geomagnetic field activity is expected to range from quiet to G2 (Moderate) geomagnetic storm conditions. G1-G2 (Minor-Moderate) conditions are likely on 27 Sep in response to combined effects of an anticipated positive polarity CH HSS and possible glancing blow from a CME that left the Sun on 23 Sep. Active conditions associated with coronal hole activity are likely on 28-29 Sep, 05 Oct, 10 Oct and 19 Oct. Unsettled conditions are likely on 04 Oct, 18 Oct and 20-21 Oct. The remainder of the outlook period is expected to be at quiet levels.