Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 20 May 2004

By SpaceRef Editor
May 20, 2004
Filed under , ,

Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Environment Center and the U.S. Air Force.

Updated 2004 May 20 2210 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 141 Issued at 2200Z on 20 May 2004

IA. Analysis of Solar Active Regions and Activity from 19/2100Z
to 20/2100Z: Solar activity was low. Newly assigned Region 618
(S10E69) produced all of today’s three C-class flares. The other
sunspot regions on the disk were quiet and stable. A filament in the
northeast quadrant erupted at 0136 UTC and was associated with a CME
off the northeast solar limb. The angular width of the CME was
narrow and the transient does not appear to be directed towards

IB. Solar Activity Forecast: Solar activity is expected to be low.
Most of the activity is expected to occur in Region 618.

IIA. Geophysical Activity Summary 19/2100Z to 20/2100Z:
The geomagnetic field was mostly quiet to unsettled. However, there
was a period of minor storm levels from 0900-1200 UTC. Solar wind
data at ACE showed a steady increase in solar wind velocity from
initial values around 380 km/s up to about 500 km/s by forecast
issue time. Elevated solar wind temperature and wave patterns in the
magnetic field data suggest that the enhancement may originate from
a coronal hole.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly unsettled but with a fair chance for some
isolated active periods during the next two days (21-22 May). A
decline to quiet to unsettled is expected around mid-day on the
third day (23 May).

III. Event Probabilities 21 May-23 May

  • Class M 15/15/15
  • Class X 01/01/01
  • Proton 01/01/01
  • PCAF green

IV. Penticton 10.7 cm Flux

  • Observed 20 May 105
  • Predicted 21 May-23 May 105/100/100
  • 90 Day Mean 20 May 105

V. Geomagnetic A Indices

  • Observed Afr/Ap 19 May 006/006
  • Estimated Afr/Ap 20 May 015/015
  • Predicted Afr/Ap 21 May-23 May 012/015-012/015-010/012

VI. Geomagnetic Activity Probabilities 21 May-23 May

A. Middle Latitudes

  • Active 30/30/25
  • Minor storm 20/20/15
  • Major-severe storm 10/10/05

B. High Latitudes

  • Active 35/35/30
  • Minor storm 20/20/10
  • Major-severe storm 10/10/05

SpaceRef staff editor.