NOAA/USAF Report of Solar-Geophysical Activity 30 Apr 2000

Report of Solar-Geophysical Activity

:Issued: 2000 Apr 30 2210 UT

# 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 121 ISSUED AT 2200Z ON 30 APR 2000

IA.  ANALYSIS OF SOLAR ACTIVE REGIONS AND ACTIVITY FROM  29/2100Z

TO 30/2100Z:  SOLAR ACTIVITY WAS LOW. REGION 8976 (S11W25) PRODUCED

THE LARGEST EVENT OF THE PERIOD, A C7/1N FLARE WITH AN ACCOMPANYING

TYPE II RADIO SWEEP (VELOCITY = 700 KM/S) AT 30/0808UT. IMAGES FROM

THE LASCO SPACECRAFT INDICATE THAT A POSSIBLY EARTH-DIRECTED CORONAL

MASS EJECTION (CME) ALSO OCCURRED IN CONJUNCTION WITH THIS EVENT.

THE TWO LARGEST REGIONS ON THE DISK, 8970 (S17E44) AND 8971

(N21W48), SHOWED SIGNS OF DECAY BUT STILL PRODUCED OCCASIONAL

OPTICAL SUBFLARES. OLD REGION 8948 SHOULD ROTATE ONTO THE DISK

TOMORROW. EIT IMAGERY HAS SHOWN CONSIDERABLE ACTIVITY FROM THIS

RETURNING REGION.

IB.  SOLAR ACTIVITY FORECAST:  SOLAR ACTIVITY IS EXPECTED TO BE LOW.

THE RETURNING REGION 8948 COULD PRODUCE ISOLATED M-CLASS EVENTS.

IIA.  GEOPHYSICAL ACTIVITY SUMMARY FROM 29/2100Z TO 30/2100Z:

THE GEOMAGNETIC FIELD WAS QUIET TO UNSETTLED.

IIB.  GEOPHYSICAL ACTIVITY FORECAST:  THE GEOMAGNETIC FIELD IS

EXPECTED TO BE QUIET TO UNSETTLED. THE CME DESCRIBED IN SECTION IA

COULD CAUSE ACTIVE CONDITIONS ON THE THIRD DAY OF THE PERIOD,

DEPENDING ON HOW CLOSE IT COMES TO EARTH.

III.  EVENT PROBABILITIES 01 MAY-03 MAY

CLASS M    30/30/30

CLASS X    01/01/01

PROTON     01/01/01

PCAF       GREEN

IV.  PENTICTON 10.7 CM FLUX

OBSERVED           30 APR 170

PREDICTED   01 MAY-03 MAY  175/180/180

90 DAY MEAN        30 APR 189

V.  GEOMAGNETIC A INDICES

OBSERVED AFR/AP 29 APR  012/012

ESTIMATED AFR/AP 30 APR  010/012

PREDICTED AFR/AP 01 MAY-03 MAY  010/010-010/010-015/020

VI.  GEOMAGNETIC ACTIVITY PROBABILITIES 01 MAY-03 MAY

A.  MIDDLE LATITUDES

ACTIVE                20/20/30

MINOR STORM           05/05/05

MAJOR-SEVERE STORM    01/01/01

B.  HIGH LATITUDES

ACTIVE                30/30/40

MINOR STORM           05/05/10

MAJOR-SEVERE STORM    01/01/01