Solar activity was at low levels. Region 1574 (S22W70) produced a C1/Sf flare at 20/1139Z. Over the period, the region grew from a simple unipolar spot to a 4 spot bipolar group. All other spotted regions indicated little change. No Earth-directed CMEs were observed.

Solar activity is expected to be at low levels with a slight chance for M-class activity for the next three days (21 - 23 September).

The geomagnetic field was at predominately quiet to unsettled levels with a period of active conditions observed between 19/2100 - 2400Z. The period began with wind speeds, as measured at the ACE spacecraft, steady at 400 km/s while the Bz component of the interplanetary magnetic field (IMF) was mostly south at about -10 nT. At about 19/2300Z, wind speed and temperature indicated slight increases while IMF Bz began fluctuating between +8 to -6 nT. By about 20/0100Z, the phi angle changed from a positive (away) to a negative (toward) orientation. These changes were all indicative of a co-rotating interaction region in advance of a coronal hole high speed stream. By the end of the period, wind velocities were steady at about 575 km/s while IMF Bz did not vary much beyond +/- 2 nT.

The geomagnetic field is expected to be at quiet to unsettled levels with isolated active intervals for days one and two (21 - 22 September) as a coronal hole high speed stream (CH HSS) remains geoeffective. By day three (23 September), mostly quiet to unsettled levels are expected as CH HSS effects wane.

  Osservato       20 Sep 117
  Previsto   21 Sep-23 Sep  115/115/120
  Media di 90 Giorni        20 Sep 122

  Osservato Afr/Ap 19 Sep  013/014
  Stimato     Afr/Ap 20 Sep  010/012
  Previsto    Afr/Ap 21 Sep-23 Sep  008/012-009/012-008/010