Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 20 Apr 2005

By SpaceRef Editor
April 21, 2005
Filed under , ,

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.
Updated 2005 Apr 20 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity
SDF Number 110 Issued at 2200Z on 20 Apr 2005

IA. Analysis of Solar Active Regions and Activity from 19/2100Z
to 20/2100Z: Solar activity was very low. Region 755 (S12E37)
produced a B 8 flare at 19/2217 UTC with an associated Type II radio
sweep (estimated speed of 1128 km/s) and a CME with an estimated
speed of 776 km/s. The CME was directed to the east and is not
expected to be geoeffective. No new regions were numbered today.

IB. Solar Activity Forecast: Solar activity is expected to be very
low with a slight chance for an isolated C-flare.

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field was at quiet to minor storm levels. Heightened
activity was due to a solar sector boundary followed by the onset of
a coronal hole high speed stream. Solar wind speed at ACE increased
from approximately 350 km/s to 600 km/s. By the end of the period,
solar wind speed had decreased to approximately 450 km/s.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be quiet to unsettled with isolated active conditions
possible on 21 April. On 22 April, conditions are expected to
increase to unsettled to active with minor storm periods possible as
another coronal hole high speed stream is expected to become
geoeffective. On 23 April, unsettled to active conditions are

III. Event Probabilities 21 Apr-23 Apr

  • Class M 01/01/01
  • Class X 01/01/01
  • Proton 01/01/01
  • PCAF green

IV. Penticton 10.7 cm Flux

  • Observed 20 Apr 077
  • Predicted 21 Apr-23 Apr 080/080/080
  • 90 Day Mean 20 Apr 091

V. Geomagnetic A Indices

  • Observed Afr/Ap 19 Apr 006/008
  • Estimated Afr/Ap 20 Apr 015/020
  • Predicted Afr/Ap 21 Apr-23 Apr 010/015-015/018-012/015

VI. Geomagnetic Activity Probabilities 21 Apr-23 Apr

A. Middle Latitudes

  • Active 25/30/25
  • Minor storm 10/15/10
  • Major-severe storm 01/05/05

B. High Latitudes

  • Active 30/30/30
  • Minor storm 15/15/15
  • Major-severe storm 05/05/05

SpaceRef staff editor.