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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 Dec 17 1230 UTC.

Solar Activity

24 hr Summary: Solar activity was low. Region 2468 (S17W20, Cao/beta) exhibited signs of growth in both its leader and trailer spots early on, but lost most of its trailer spots by the end of the period. Region 2469 (N18E06, Hax/alpha) remained quiescent throughout the period. Region 2470 (N15E25, Eko/beta) showed slight decay in its intermediate spots and was responsible for both a B7 flare at 17/0341 UTC and a C1/Sf flare (the largest of the period) at 17/0533 UTC.

Analysis was completed on the two asymmetrical, full-halo coronal mass ejections (CMEs) mentioned in the previous discussion. Based on WSA Enlil model data, both appear to have an Earthward directed component, with likely arrival times at Earth near the end of the period on 18 Dec to early in the period on 19 Dec. Impacts are detailed later in this discussion. Forecast: Solar activity is likely to be at low levels with a slight chance for an M-class flare (R1-R2/Minor-Moderate radio blackouts) on days one through three (17-19 Dec).

Energetic Particles

24 hr Summary: The greater than 2 MeV electron flux was at moderate levels throughout the period. The greater than 10 MeV proton flux remained at background levels.

Forecast: The greater than 2 MeV electron flux is expected to be at normal to moderate levels on day one (17 Dec). There is a chance for moderate to high levels on days two and three (18-19 Dec) in response to the elevated wind speeds associated with the recent coronal hole high-speed stream (CH HSS). However, electron flux values will likely fall to background levels as the two expected CMEs pass the GOES satellite and redistribute the electron particles. The greater than 10 MeV proton flux is expected to continue at background levels.

Solar Wind

24 hr Summary: Solar wind parameters were at mostly ambient levels. Solar wind speed began the period near 530 km/s but decreased to near 420 km/s by the end of the period. The total field (Bt) remained fairly consistent near 4nT, but did see a few fluctuations between 1 nT and 6 nT. The Bz component was positive for the majority of the period, but did show a maximum southward deflection to -4 nT. The phi angle was in a predominantly negative solar sector orientation with occasional oscillations into the positive sector throughout the period. Forecast: The solar wind environment is expected to be at background conditions on day one into day two (17-18 Dec). Late on day two (18 Dec), solar wind speeds and IMF total filed strength are likely to see sudden and significant enhancements, with Bz seeing a strong southern deflection as the first CME from 16 Dec is forecast to impact the ACE satellite. These enhancements are expected to continue into day three (19 Dec) as the second CME is expected to hit ACE as well. CME effects are anticipated to linger through most of the day before tapering off by the end of day three (19 Dec).

Geospace

24 hr Summary: The geomagnetic field remained at quiet levels throughout the period.

Forecast: The geomagnetic field is expected to be at mostly quiet levels on day one (17 Dec) and most of the day on day two (18 Dec) due to a return to ambient background conditions. Late on day two (18 Dec)/early on day three (19 Dec) the two CMEs from 16 Dec, described above, are expected to impact Earths magnetosphere, likely producing G1-Minor storm conditions late on 18 Dec and early on 19 Dec.

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