:Product: Forecast Discussion
:Issued: 2026 Jun 18 0030 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
#
Solar Activity

.24 hr Summary...
Solar activity was low with only C-class solar flare activity. Region
4465 (N07W49, Cso/beta) underwent some decay and only produced a
low-level C-class flare. Region 4469 (S16W06, Bxo/beta) decayed further
and was inactive. Region 4470 (N07E54, Dao/beta) underwent some growth,
but did not increase in magnetic complexity. The region was primarily
inactive. The largest solar flare of the period, a C2.5 at 17/1506 UTC,
came from just beyond the west limb with the likely source being
recently rotated out of view Region 4464 (S14, L=342). 

A CME became visible in STEREO coronagraph imagery at 17/0038 UTC and
CCOR imagery approximately 30 min later. This eruption was first
determined to be farsided due to SUVI 304 and 193 imagery; however, the
backfilling of a SOHO LASCO data gap prompted a re-analysis and it
has since concluded that there may be an Earth-directed component.
Modeling is currently ongoing.

There was an additional, faster, eruption off the east limb close to the
equator, with the resulting CME first appearing in LASCO C2 imagery at
approximately 17/0135 UTC. Due to its faintness, this CME is not visible
in other coronagraphs. Modeling of this event is also ongoing, but a
significant Earth-directed component is not anticipated.

.Forecast...
Solar activity is likely to continue at low levels 18-20 Jun, with a
slight chance for M-class (R1-Minor) solar flares due primarily to the
combined flare probabilities of Regions 4465 and 4470.

Energetic Particle

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

.Forecast...
The greater than 2 MeV electron flux is likely to continue reaching
moderate levels 18-20 Jun; while the greater than 10 MeV proton flux is
expected to remain at background.

Solar Wind

.24 hr Summary...
Solar wind parameters were indicative of a weak disturbance in the IMF,
which was probably related to anticipated early stage CH HSS influences.
The total IMF strength peaked at 12 nT due to probable CIR effects,
before it weakened to values at 5 nT or less. The Bz component was
variable without a pronounced southward deflection. The phi angle was
quite variable between sectors. Solar wind speed increased from 400 km/s
to near 500 km/s before declining to about 450 km/s.

.Forecast...
Mild solar wind disturbance and enhancements are anticipated through 20
Jun due to weak positive polarity CH HSS effects.

Geospace

.24 hr Summary...
The geomagnetic field was quiet.

.Forecast...
The geomagnetic field is likely to be quiet to unsettled on 18 Jun in
response to weak CH HSS influences. Slightly more response is forecast
19-20 Jun with unsettled to active conditions likely due to additional
and continuing CH HSS effects.