NOAA SEC Report of Solar-Geophysical Activity 27 Apr 2002

:Product: Report of Solar-Geophysical Activity

:Issued: 2002 Apr 27 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 117 Issued at 2200Z on 27 Apr 2002

IA.  Analysis of Solar Active Regions and Activity from  26/2100Z

to 27/2100Z:  Solar activity was low. The largest event of the period

was a C4/Sf from Region 9919 (N12E14). Other minor C-class flares

were observed in this Beta region. No significant activity or

changes were noted in the remaining active regions. The filament

eruption observed late in the last period from near S32W12 produced

a large CME, but it does not appear Earthbound. New Region 9926

(N12E26) was numbered today. This spot cluster was formerly grouped

with Region 9919, but magnetograms indicate that it is a separate

region.

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

at low levels. Regions 9915 (N11W26) and 9919 will likely produce

C-class flares.

IIA.  Geophysical Activity Summary 26/2100Z to 27/2100Z:

The geomagnetic field was mostly quiet, but became unsettled late in

the period. Solar wind indices on ACE suggest that we are

transitioning into a high speed coronal hole stream. The greater

than 10 MeV protons at geosynchronous orbit remain elevated

following the proton event that began on 21 Apr and ended on the

26th.

IIB.  Geophysical Activity Forecast:  The geomagnetic field is

expected to be mostly unsettled with isolated active periods at all

latitudes due to high speed coronal hole flow. Minor storm

conditions are expected at high latitudes during local nighttime

hours. Expect quiet to unsettled conditions to return by day three.

III.  Event Probabilities 28 Apr-30 Apr

Class M    25/25/25

Class X    05/05/05

Proton     01/01/01

PCAF       green

IV.  Penticton 10.7 cm Flux

Observed           27 Apr 157

Predicted   28 Apr-30 Apr  160/160/165

90 Day Mean        27 Apr 195

V.  Geomagnetic A Indices

Observed Afr/Ap 26 Apr  002/006

Estimated Afr/Ap 27 Apr  007/010

Predicted Afr/Ap 28 Apr-30 Apr  012/012-010/010-008/008

VI.  Geomagnetic Activity Probabilities 28 Apr-30 Apr

A.  Middle Latitudes

Active                35/35/30

Minor storm           15/15/10

Major-severe storm    05/05/01

B.  High Latitudes

Active                45/45/35

Minor storm           25/25/15

Major-severe storm    10/10/05