The Sun is entering its minimum activity phase, where solar activity at quiet level for the last week. Observations showed that solar disk remains spotless within the last week and there was no flare, radio burst, nor significant CME detected. STEREO/EUVI observation shows that there is one new region emerged at the east limb, thus solar activity next week is predicted to be at eruptive level.
Geomagnet conditions on February, 16th – 22th 2018 was in quiet conditon. Local response from Kupang observatory seen from K index with maximum value was 3. Minimum Dst index was -19 nT on February, 20th, 2018 and maximum Kp index was 4. This means the disturbance occurred at mid-high latitudes but not to the low latitude. This disturbance was caused by high speed stream of solar wind coming from coronal holes. At that time, substorm occurred with long duration and the Ae index showing the value of ≤ 1000 nT for 2 days. The electron flux were on the low level around 10 [/cm2/sec/sr] at the beginning week, then after the disturbance, the electron flux became high around 1000 [/cm2/sec/sr].
Ionosphere conditions in this week were quiet to minor level.
There was depression of foF2 more than 30% from its median value at 20 February for 2 hours duration. The foF2 depressions were impacted to the radiowave propagation over the ionosphere which known as the MUF Depression. Besides the foF2, the minimum frequencies (fmin) of the ionosphere in this week were in quiet condition. There was no increment of fmin that could be a source of disturbance in the HF radio communication which known as a Shortwave Fadeout (SWF) or Radio Blackout (RB). Based on the ionospheric observations using GISTM over Bandung, Biak and Manado the scintillation (S4) condition for this week were in quiet level. The error positioning conditions were between normal to slight level condition that determined by the index W values.
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