Viewing archive of Saturday, 20 September 2003

Solar activity report

Report of Solar-Geophysical Activity 2003 Sep 20 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 263 Issued at 2200Z on 20 Sep 2003

IA. Analysis of Solar Active Regions and Activity from 19-2100Z to 20-2100Z

Solar activity was low during the past 24 hours. Today's largest event was a C3.6 at 1536 UTC. There was only limited image data for this event, but it appears to have originated from newly assigned Region 464 (N05E77) which rotated into view today. Region 464 is a relatively large (360 millionths) E-type sunspot group and displayed frequent surge activity during the past 24 hours. Region 461 (N13W89), now crossing the west limb, produced the second largest event of the day, a C3 at 0512 UTC. Region 459 (S11W40) showed slow growth and occasional brightenings but was otherwise stable. LASCO images show a coronal mass ejection (CME) off the west limb, beginning at 0430 UTC. The CME does not appear to have any earthward component.
IB. Solar Activity Forecast
Solar activity is expected to be low for the next three days. Regions 464 and 459 are the most likely sources for activity. There is a slight chance for an isolated M-class flare.
IIA. Geophysical Activity Summary 19-2100Z to 20-2100Z
The geomagnetic field was at unsettled to minor storm levels with an isolated major storm period at some locations between 0300-0600 UTC. Geomagnetic conditions were initially unsettled from 20/2100-21/0000 UTC, but became more disturbed after 0000 UTC and remained so for the remainder of the day, with active conditions predominating. The solar wind signatures show the continued presence of a high speed coronal hole stream. In particular, the solar wind speed showed an increase around 0000 UTC up to about 700 km/s. The signature is consistent with the transition of the solar wind source from an isolated coronal hole in the western hemisphere to a southern polar extension coronal hole that crossed central meridian on 18 September. The greater than 2 MeV electron fluxes reached high levels during the past 24 hours.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to be mostly active for the next 24 hours as the current coronal-hole driven disturbance continues. A slight decline to predominantly unsettled to active is expected for the second and third days. There is a fair chance for some isolated storm periods over the next three days.
III. Event Probabilities 21 Sep to 23 Sep
Class M20%20%20%
Class X01%01%01%
IV. Penticton 10.7 cm Flux
  Observed       20 Sep 112
  Predicted   21 Sep-23 Sep  112/115/115
  90 Day Mean        20 Sep 120
V. Geomagnetic A Indices
  Observed Afr/Ap 19 Sep  026/032
  Estimated     Afr/Ap 20 Sep  025/025
  Predicted    Afr/Ap 21 Sep-23 Sep  020/025-015/020-015/020
VI. Geomagnetic Activity Probabilities 21 Sep to 23 Sep
A. Middle Latitudes
Minor storm25%20%20%
Major-severe storm10%05%05%
B. High Latitudes
Minor storm35%25%25%
Major-severe storm20%15%10%

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