Product: Weekly Highlights and Forecasts
Issued: 2011 Sep 20 2026 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC web contact www.swpc.noaa.gov/weekly.html
#
# Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity 12 - 18 September 2011
Although by September 15th there were 11 numbered regions on the visible solar disk, solar activity was low. Region 1289 (N23, L=129, class/area, Dho/450 on 10 September) was the largest region but only managed to produce low level C-flare activity. Region 1297 (S18, L=151, class/area, Dao/60 on 16 September), numbered on the 14 September, was the most active region during the period. The region produced 12 flares, including a C9/1F on 14 September at 2051 UTC, before decaying to plage late on the 17 September. Regions 1295 (N22, L=060, class/area, Dhc/300 on 18 September) and 1290 (S15, L=139, class/area, Dsi/070 on 12 September) also produced C9 flares;
a long duration C9 at 12/2054 UTC and a C9/Sf at 16/1136 UTC respectively. The remaining regions produced only low to mid level C-class activity.
The only earth-directed coronal mass ejection (CME) of the week was linked to an eruption on the 13 September in the vicinity of Region 1289 (N24W25). The full halo CME was observed in SOHO / LASCO C2 imagery at 14/0000Z with an estimated plane-of-sky speed of 428 km/s which was later refined to approximately 600 km/s using STEREO COR2 imagery.
No proton events were observed at geosynchronous orbit.
The geomagnetic field ranged from quiet to active levels at mid latitudes and briefly reached severe storm levels at high latitudes. The week began with unsettled to active levels at middle latitudes
with active to major storm conditions at higher latitudes as the geomagnetic field continued to be influenced by a geoeffective coronal hole high speed stream (CH HSS). Disturbed conditions continued until mid day on the 13 September. By 14 September, the geomagnetic field had returned to quiet levels as the effects of the high speed stream waned. Quiet conditions persisted until 17
September when the CME from 13 September arrived at earth. The CME passage was first observed at the ACE spacecraft at 17/0256 UTC followed by a 21 nT sudden impulse at the Boulder magnetometer. The geomagnetic field reacted with unsettled to active conditions at mid latitudes and periods of major to severe storm levels at high latitudes. Mostly quiet conditions returned by 18 September with two active periods observed mid-day at high latitudes.
The greater than 2 MeV electron flux at geosynchronous orbit reached high levels 12-17 September.
Product: 27-day Space Weather Outlook Table 27DO.txt
:Issued: 2011 Sep 20 2026 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC web contact www.swpc.noaa.gov/wwire.html
#
# 27-day Space Weather Outlook Table
# Issued 2011-09-20
#
# UTC Radio Flux Planetary Largest
# Date 10.7 cm A Index Kp Index
2011 Sep 21 140 5 2
2011 Sep 22 140 5 2
2011 Sep 23 135 5 2
2011 Sep 24 135 5 2
2011 Sep 25 130 8 3
2011 Sep 26 130 5 2
2011 Sep 27 130 8 3
2011 Sep 28 130 5 2
2011 Sep 29 130 5 2
2011 Sep 30 130 15 4
2011 Oct 01 130 8 3
2011 Oct 02 135 5 2
2011 Oct 03 135 5 2
2011 Oct 04 135 5 2
2011 Oct 05 135 5 2
2011 Oct 06 140 5 2
2011 Oct 07 140 5 2
2011 Oct 08 145 8 3
2011 Oct 09 145 15 4
2011 Oct 10 145 12 3
2011 Oct 11 140 8 3
2011 Oct 12 140 5 2
2011 Oct 13 140 5 2
2011 Oct 14 140 5 2
2011 Oct 15 140 5 2
2011 Oct 16 140 5 2
2011 Oct 17 140 5 2
(NOAA)