Forecast Discussion

Product: Forecast Discussion Issued: 2021 May 16 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 2822 (N16W42, Hsx/alpha) was in decay and Region 2823 (S23 L=326) reached plage. No Earth-directed CMEs were observed in available coronagraph imagery.
.Forecast… Solar activity is expected to be very low over 16-18 May.
Energetic Particle
.24 hr Summary… The greater than 2 MeV electron flux was normal to moderate and the greater than 10 MeV proton flux remained at background values.
.Forecast… The greater than 2 MeV electron flux is expected to reach moderate levels and the greater than 10 MeV proton flux is expected to remain at background levels over 16-18 May.
Solar Wind
.24 hr Summary… Solar wind parameters, as measured by the DSCOVR spacecraft, were at near background conditions. Total magnetic field strength was at or below 5 nT and no significant periods of southward Bz were observed. Solar wind speeds were in a declining trend, ending the period near 350 km/s. Phi angle was predominantly oriented in the negative sector.
.Forecast… Solar wind parameters are expected to continue at near background levels over 16 May. Enhanced conditions are expected due to influence from a negative polarity CH HSS on 17 May. On 18 May, the anticipated arrival of the periphery of a CME that left the Sun on 13 May is likely to further enhance the solar wind environment.
.24 hr Summary… The geomagnetic field was quiet.
.Forecast… The geomagnetic field is expected to continue at mostly quiet levels on 16 May. On 17 May, an increase active conditions are likely in response to the onset of coronal hole influence. Modeling of a CME that left the Sun on 13 May suggests passage by Earth on 18 May. The resulting geomagnetic response is likely to be active to G1 (Minor) storm levels.
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