NOAA SEC Report of Solar-Geophysical Activity 24 Apr 2002

:Product: Report of Solar-Geophysical Activity

:Issued: 2002 Apr 24 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 114 Issued at 2200Z on 24 Apr 2002

IA.  Analysis of Solar Active Regions and Activity from  23/2100Z

to 24/2100Z:  Solar activity remained at low levels with occasional

C-class flares. The largest flare was a C4/1n at 24/1605 UTC from

Region 9912 (N09W51). Region 9912 showed gradual decay, mostly in

its trailer spots. Region 9913 (S16W44) produced occasional

subflares, a few of which reached C-class. It showed minor growth as

well as a minor mix of polarities. Region 9914 (N04E04) showed

gradual growth, but remained simply-structured. New Region 9924

(S17W07) emerged rapidly and produced isolated subflares. It was a

relatively small D- type spot group with minor polarity mixing

throughout. New Region 9923 (S03W31) was also numbered.

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

low to moderate levels. Isolated low-level M-class flares are

possible during the period.

IIA.  Geophysical Activity Summary 23/2100Z to 24/2100Z:

Geomagnetic field activity was at quiet to unsettled levels. The

greater than 10 MeV proton event that began at 21/0225 UTC

continued. The greater than 10 MeV proton flux was around 24.0 PFU

and gradually decreasing as the period ended.

IIB.  Geophysical Activity Forecast:  Geomagnetic field activity is

expected to be at quiet to unsettled levels during 25 – 26 April

increasing to unsettled to active levels on 27 April due to

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

is expected to end early in the period.

III.  Event Probabilities 25 Apr-27 Apr

Class M    40/40/40

Class X    05/05/05

Proton     50/05/05

PCAF       in progress

IV.  Penticton 10.7 cm Flux

Observed           24 Apr 177

Predicted   25 Apr-27 Apr  180/180/185

90 Day Mean        24 Apr 198

V.  Geomagnetic A Indices

Observed Afr/Ap 23 Apr  021/022

Estimated Afr/Ap 24 Apr  008/010

Predicted Afr/Ap 25 Apr-27 Apr  008/010-012/012-015/015

VI.  Geomagnetic Activity Probabilities 25 Apr-27 Apr

A.  Middle Latitudes

Active                20/25/35

Minor storm           10/10/15

Major-severe storm    01/01/01

B.  High Latitudes

Active                20/30/40

Minor storm           10/15/20

Major-severe storm    01/01/05