Status Report

Joint USAF/NOAA Report of Solar and Geophysical Activity 21 May 2004

By SpaceRef Editor
May 21, 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 21 2200 UTC

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 142 Issued at 2200Z on 21 May 2004

IA. Analysis of Solar Active Regions and Activity from 20/2100Z
to 21/2100Z: Solar activity was low during the past 24 hours due to
two C-class flares: a C2 at 0551 UTC from Region 618 (S11E55) and a
C2 at 1623 UTC from Region 617 (S11W46). Region 618 has shown a slow
growth trend and Region 617 appears to be decaying. The remainder of
the solar disk and limbs were quiet and stable.

IB. Solar Activity Forecast: Solar activity is expected to continue
at low levels for the next three days (21-23 May). Region 618 is
expected to be the main source for activity.

IIA. Geophysical Activity Summary 20/2100Z to 21/2100Z:
The geomagnetic field was quiet to unsettled during the past 24 hours
The solar wind speed remains somewhat elevated: there was a slow
declining trend up until 1800 UTC, after which speeds increased
again, with values around 500 km/s by forecast issue time.

IIB. Geophysical Activity Forecast: The geomagnetic field is
expected to be mostly unsettled with a chance for isolated active
periods at high latitudes for the next 24 hours (22 May). Unsettled
conditions should prevail for the second day (23 May) and conditions
should decline to quiet to unsettled by the third day (24 May).

III. Event Probabilities 22 May-24 May

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

IV. Penticton 10.7 cm Flux

  • Observed 21 May 107
  • Predicted 22 May-24 May 105/105/100
  • 90 Day Mean 21 May 105

V. Geomagnetic A Indices

  • Observed Afr/Ap 20 May 011/013
  • Estimated Afr/Ap 21 May 012/010
  • Predicted Afr/Ap 22 May-24 May 010/015-010/012-005/008

VI. Geomagnetic Activity Probabilities 22 May-24 May

A. Middle Latitudes

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

B. High Latitudes

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

SpaceRef staff editor.