:Product: Forecast Discussion :Issued: 2018 Oct 18 1230 UTC # Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center # Solar Activity .24 hr Summary... Solar activity was very low. Region 2725 (S11, L111) returned to plage. A CME signature was observed in LASCO C2 and STEREO COR2 coronagraph imagery at approximately 17/1516 UTC and 17/1509 UTC, respectively. Analysis indicated this was a far sided event and is not Earth-directed. Coronal dimming was also observed in SDO/AIA 193 imagery near the extension of the north polar coronal hole (CH36), at around 17/1541 UTC. An apparent signature was observed in either STEREO or LASCO coronagraph imagery, likely indicating most of the ejecta was reabsorbed. No Earth-directed CMEs were observed in available coronagraph imagery. .Forecast... Solar activity is expected to remain very low on 18-20 Oct. Energetic Particle .24 hr Summary... The greater than 2 MeV electron flux reached high levels with a maximum flux of 1,463 pfu at 17/2020 UTC. The greater than 10 MeV proton flux continued at background values. .Forecast... The greater than 2 MeV electron flux is expected to reach high levels on 18 Oct due to residual effects from the negative polarity CH HSS. The arrival of a CIR is expected to decrease flux to normal and moderate levels on 19 Oct, with an anticipated increase to moderate and high levels on 20 Oct due to effects associated with another CH HSS. The greater than 10 MeV proton flux is expected to remain at background levels. Solar Wind .24 hr Summary... Solar wind parameters were indicative of a return to an ambient background solar wind regime. Solar wind speed decreased from around 445 km/s to near 365 km/s by the end of the period. Total field strength remained steady near 4 nT, while the Bz component remained mostly positive. The phi angle began the period with intermittent oscillations between positive and negative, but remained solidly in the negative sector after 17/1600 UTC. .Forecast... Solar wind parameters are expected to see slight enhancements late on 18 Oct following an anticipated SSBC. On 19 Oct, a CIR followed by the onset of a positive polarity CH HSS, is expected to further enhance the solar wind environment, increasing wind speeds and enhancing the mag field. Conditions should begin to wane late on 20 Oct as the CH HSS moves west. Geospace .24 hr Summary... The geomagnetic field was quiet. .Forecast... The geomagnetic field is expected to be quiet for most of the remainder of 18 Oct, with some unsettled activity late in the day due to the anticipated SSBC activity. Unsettled to active conditions are expected on 19 Oct, with an isolated period of G1 (Minor) storm conditions likely, due to CIR arrival and eventual interaction with the positive polarity CH HSS. Quiet to unsettled conditions are expected on 20 Oct, with a chance for active conditions, as CH HSS influences persist, but gradually weaken.