NOAA SEC Report of Solar-Geophysical Activity 25 Apr 2002

:Product: Report of Solar-Geophysical Activity

:Issued: 2002 Apr 25 2210 UTC

# Prepared jointly by the U.S. Dept. of Commerce, NOAA,

#Space Environment Center and the U.S. Air Force.

#

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 115 Issued at 2200Z on 25 Apr 2002

IA.  Analysis of Solar Active Regions and Activity from  24/2100Z

to 25/2100Z:  Solar activity was moderate. Region 9912 (N11W65)

produced an impulsive M1/1f flare at 24/2156 UTC associated with

minor radio emission. This region continued to slowly decay. Region

9924 (S15W20), which emerged rapidly yesterday, began to gradually

decay. Minor growth was observed in Region 9915 (N12E01). The

remaining regions were unremarkable including newly numbered Region

9925 (S14W36).

IB.  Solar Activity Forecast:  Solar activity is expected to be low

with an outside chance for an isolated low-level M-class flare.

IIA.  Geophysical Activity Summary 24/2100Z to 25/2100Z:

Geomagnetic field activity was at quiet levels during most of the

period. The greater than 10 MeV proton event that began at 21/0225

UTC persisted, but just barely above event threshold (the maximum

for this event was 2520 pfu at 21/2320 UTC).

IIB.  Geophysical Activity Forecast:  Geomagnetic field activity is

expected to be at quiet to unsettled levels on 26 April. Unsettled

to active levels are expected during 27 – 28 April due to recurrent

coronal hole effects. The greater than 10 MeV proton event is

expected to end early on 26 April.

III.  Event Probabilities 26 Apr-28 Apr

Class M    30/30/30

Class X    01/01/01

Proton     01/01/01

PCAF       in progress

IV.  Penticton 10.7 cm Flux

Observed           25 Apr 167

Predicted   26 Apr-28 Apr  170/170/175

90 Day Mean        25 Apr 197

V.  Geomagnetic A Indices

Observed Afr/Ap 24 Apr  006/007

Estimated Afr/Ap 25 Apr  006/007

Predicted Afr/Ap 26 Apr-28 Apr  012/012-015/015-012/012

VI.  Geomagnetic Activity Probabilities 26 Apr-28 Apr

A.  Middle Latitudes

Active                25/35/35

Minor storm           10/15/15

Major-severe storm    01/01/01

B.  High Latitudes

Active                30/40/40

Minor storm           15/20/20

Major-severe storm    01/05/05