NOAA SEC Report of Solar-Geophysical Activity 19 Apr 2002

:Product: Report of Solar-Geophysical Activity

:Issued: 2002 Apr 19 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 109 Issued at 2200Z on 19 Apr 2002

IA.  Analysis of Solar Active Regions and Activity from  18/2100Z

to 19/2100Z:  Solar activity was low. Region 9906 (S14W66) produced

several C-class subflares during the past day. The largest was a

C3/Sf at 19/1822 UTC. This region continues to decay slowly but

retains appreciable size and magnetic complexity. New Regions 9913

(S15E23) and 9914 (N04E72) were numbered.

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

moderate. Region 9906 appears to be capable of M-class activity,

including an isolated major flare.

IIA.  Geophysical Activity Summary 18/2100Z to 19/2100Z:

The geomagnetic field ranged from unsettled to major storm. A shock

was observed at ACE at 19/0804 UTC and was followed by an SI at

ground magnetometers (36 nT at Boulder) at 19/0836 UTC. This shock

is believed to be associated with the LDE M2/CME that occurred on 17

April.

IIB.  Geophysical Activity Forecast:  The geomagnetic field is

expected to be at active to major storm levels for about the next 12

hours as the current CME passes. The field is expected to return to

quiet to unsettled conditions by the end of the 3-day forecast

period. A greater than 10 MeV proton event is possible if Region

9906 produces a major flare.

III.  Event Probabilities 20 Apr-22 Apr

Class M    50/30/30

Class X    05/01/01

Proton     05/01/01

PCAF       yellow

IV.  Penticton 10.7 cm Flux

Observed           19 Apr 180

Predicted   20 Apr-22 Apr  175/170/170

90 Day Mean        19 Apr 201

V.  Geomagnetic A Indices

Observed Afr/Ap 18 Apr  035/054

Estimated Afr/Ap 19 Apr  030/040

Predicted Afr/Ap 20 Apr-22 Apr  030/040-012/015-008/015

VI.  Geomagnetic Activity Probabilities 20 Apr-22 Apr

A.  Middle Latitudes

Active                60/30/10

Minor storm           30/10/05

Major-severe storm    10/05/01

B.  High Latitudes

Active                45/40/15

Minor storm           40/15/05

Major-severe storm    15/10/01