NOAA SEC Report of Solar-Geophysical Activity 22 Apr 2002

:Product: Report of Solar-Geophysical Activity

:Issued: 2002 Apr 22 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 112 Issued at 2200Z on 22 Apr 2002

IA.  Analysis of Solar Active Regions and Activity from  21/2100Z

to 22/2100Z:  Solar activity decreased to low levels. Region 9906

(S14W103), now well beyond the west limb, produced a C7 X-ray flare

at 22/0019 UTC associated with a bright surge and an eruptive

prominence. Region 9912 (N10W25) produced a C2/Sf flare at 22/1210

UTC associated with a Type II radio sweep (estimated velocity 804

km/sec). Region 9912 was in a gradual growth phase. A weak magnetic

delta configuration may have developed within its trailer spots. New

Region 9917 (S30E45) was numbered.

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

low to moderate levels. There’s a chance for an isolated M-class

flare from Region 9912.

IIA.  Geophysical Activity Summary 21/2100Z to 22/2100Z:

Geomagnetic field activity ranged from quiet to active levels. Active

levels occurred during 22/0300 – 0600 UTC. The greater than 100 MeV

proton event that began at 21/0155 UTC reached a peak of 22.9 pfu at

21/1025 UTC and was in progress as the period ended. The greater

than 10 MeV proton event that began at 21/0225 UTC reached a peak of

2520 pfu at 21/2320 UTC and was in progress as the period ended.

Peak polar cap absorption associated with the proton event was

estimated to be 16 dB (daytime) and 3.9 dB (nighttime).

IIB.  Geophysical Activity Forecast:  Geomagnetic field activity is

expected to increase to active to minor storm levels on 23 April in

response to yesterday’s X1/partial-halo CME event. Unsettled to

active conditions are expected on 24 April as the disturbance winds

down. Unsettled conditions are expected on the final day. The

greater than 100 MeV proton event is expected to end early on 23

April. The greater than 10 MeV proton event is expected to end on 24

April.

III.  Event Probabilities 23 Apr-25 Apr

Class M    40/40/40

Class X    05/05/05

Proton     99/99/20

PCAF       in progress

IV.  Penticton 10.7 cm Flux

Observed           22 Apr 170

Predicted   23 Apr-25 Apr  170/175/175

90 Day Mean        22 Apr 199

V.  Geomagnetic A Indices

Observed Afr/Ap 21 Apr  004/007

Estimated Afr/Ap 22 Apr  013/015

Predicted Afr/Ap 23 Apr-25 Apr  025/030-015/020-015/015

VI.  Geomagnetic Activity Probabilities 23 Apr-25 Apr

A.  Middle Latitudes

Active                40/40/35

Minor storm           20/10/05

Major-severe storm    10/05/05

B.  High Latitudes

Active                50/50/40

Minor storm           30/20/10

Major-severe storm    15/10/01