Viewing archive of Monday, 18 April 2011

Solar activity report

Report of Solar-Geophysical Activity 2011 Apr 18 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 108 Issued at 2200Z on 18 Apr 2011

IA. Analysis of Solar Active Regions and Activity from 17-2100Z to 18-2100Z

Solar activity has been at low levels for the past 24 hours. Region 1193 (N17E05) has been the most active, producing two low-level C-class events. Region 1193 has remained rather stable but continues to grow in sunspot number and magnetic complexity. At 18/0348Z, a C1 flare was observed off the west limb. There was a non-earth directed CME associated with this event visible in LASCO C2 imagery at 18/0412Z.
IB. Solar Activity Forecast
Solar activity is expected to be at low levels with a chance for M-class events for the next three days (19-21 April). Region 1190 (N13W68) is expected to rotate off the visible disk in the next two days, while a new flux Region, visible in STEREO Behind EIT imagery, is forecast to rotate onto the southeast limb early on 19 April.
IIA. Geophysical Activity Summary 17-2100Z to 18-2100Z
The geomagnetic field has been at quiet to unsettled levels for the past 24 hours. Quiet levels were observed till around 18/0634Z when a 24 nT Sudden Impulse (SI) was observed by the Boulder magnetometer. Following the arrival of this shock, mostly unsettled levels were observed at mid latitudes with isolated active periods at high latitudes. This increase in activity was due to the arrival of a slow moving CME, observed lifting off the solar disk on 15 April.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be at quiet levels on day 1 (19 April). An increase to unsettled geomagnetic levels with a chance for active periods is expected on days 2 and 3 (20-21 April), due to the forecasted arrival of a coronal hole high speed stream.
III. Event Probabilities 19 Apr to 21 Apr
Class M20%20%20%
Class X01%01%01%
IV. Penticton 10.7 cm Flux
  Observed       18 Apr 111
  Predicted   19 Apr-21 Apr  115/115/115
  90 Day Mean        18 Apr 104
V. Geomagnetic A Indices
  Observed Afr/Ap 17 Apr  002/005
  Estimated     Afr/Ap 18 Apr  007/008
  Predicted    Afr/Ap 19 Apr-21 Apr  005/005-010/010-010/010
VI. Geomagnetic Activity Probabilities 19 Apr to 21 Apr
A. Middle Latitudes
Minor storm01%10%05%
Major-severe storm01%01%01%
B. High Latitudes
Minor storm01%15%10%
Major-severe storm01%00%01%

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