:Product: Weekly Highlights and Forecasts :Issued: 2000 Jul 18 2112 UT HIGHLIGHTS OF SOLAR AND GEOMAGNETIC ACTIVITY 10 - 16 JULY 2000 SOLAR ACTIVITY WAS HIGH FOR MOST OF THE PERIOD. REGION 9077 (N18, L = 310, CLASS/AREA FKC/1010 ON 11 JULY), A LARGE GROUP WITH A MAGNETICALLY COMPLEX (BETA-GAMMA-DELTA) STRUCTURE, PRODUCED FOUR MAJOR FLARES DURING THE PERIOD. THE FIRST OF THESE WAS A M5/2B LONG-DURATION FLARE AT 10/2142UT WITH ASSOCIATED TYPE II AND IV RADIO SWEEPS THAT OCCURRED AS THE REGION GREW AT A RAPID RATE. REGION 9077 PRODUCED AN X1/2N FLARE AT 11/1310UT AS THE REGION CONTINUED RAPID DEVELOPMENT. THIS FLARE WAS ASSOCIATED WITH A 1600 SFU TENFLARE AND A FULL-HALO CORONAL MASS EJECTION (CME). REGION 9077 ALSO PRODUCED AN M4 X-RAY FLARE AT 11/1141UT. REGION 9070 (N19, L = 029, CLASS/AREA FKO/680 ON 12 JULY), A LARGE MAGNETICALLY COMPLEX GROUP SHOWED GROWTH AS IT PRODUCED AN M1/1N FLARE AT 11/1858UT. REGION 9077 PRODUCED AN X1/2B FLARE AT 12/1037UT ACCOMPANIED BY A 390 SFU TENFLARE AND A TYPE IV RADIO SWEEP. REGION 9070 ADDED TO THE MAJOR FLARE COUNT WITH AN M5/2F AT 12/1849UT WITH AN ASSOCIATED 230 SFU TENFLARE. IT ALSO PRODUCED A SUBFLARE AT 12/2013UT WITH AN ASSOCIATED TYPE II RADIO SWEEP. SOLAR ACTIVITY REMAINED HIGH ON 13 JULY DUE TO FIVE LOW-LEVEL M-CLASS FLARES FROM A NUMBER OF REGIONS INCLUDING 9070, 9077, AND 9085 (N14, L = 254, CLASS/AREA EKI/270 ON 16 JULY). REGION 9077 PRODUCED THE FOURTH AND LARGEST OF ITS MAJOR FLARES WITH AN X5/3B AT 14/1024UT WITH AN ASSOCIATED 2600 SFU TENFLARE, TYPE II AND IV RADIO SWEEPS (TYPE IV DURATION ABOUT 6.5 HOURS), AND A FAST-MOVING HALO-CME. THIS FLARE ALSO PRODUCED A HUGE SOLAR PROTON EVENT (SEE THE DESCRIPTION BELOW). ACTIVITY DECREASED TO MODERATE LEVELS ON 15 JULY AS REGION 9077 BEGAN TO SLOWLY DECAY ALTHOUGH IT REMAINED LARGE AND RETAINED ITS BETA-GAMMA-DELTA MAGNETIC STRUCTURE. ACTIVITY RETURNED TO HIGH LEVELS ON 16 JULY WITH AN M5/1N FLARE AT 16/0203UT FROM REGION 9090 (N16, L = 204, CLASS/AREA DSO/090 ON 16 JULY), AS WELL AS AN M1/1N FLARE AT 16/2157UT. AS THE PERIOD ENDED, REGION 9077 CONTINUED TO GRADUALLY DECAY, BUT REMAINED LARGE AND COMPLEX. REAL-TIME SOLAR WIND VELOCITY AND DENSITY DATA WERE NOT AVAILABLE FROM THE NASA ADVANCED COMPOSITION EXPLORER (ACE) SPACECRAFT DURING 14/1100 - 16/0000UT DUE TO THE SOLAR PROTON EVENTS DESCRIBED BELOW. HOWEVER, VELOCITY AND DENSITY READINGS WERE AVAILABLE FROM THE SOHO/MTOF SENSOR. THREE INTERPLANETARY SHOCKS PASSED THE ACE SPACECRAFT DURING THE PERIOD ASSOCIATED WITH CMES THAT FOLLOWED FLARES FROM REGION 9077. THE THIRD AND STRONGEST OF THESE SHOCKS OCCURRED AT APPROXIMATELY 15/1400UT AND WAS ACCOMPANIED BY WILDLY VARYING IMF BZ READINGS (PLUS 40 TO MINUS 54 NT (GSM)), VELOCITIES AS HIGH AS 950 KM/SEC, AND DENSITIES AS HIGH AS 50 P/CC. SOLAR WIND PARAMETERS WERE GRADUALLY RETURNING TO MORE NOMINAL VALUES AS THE PERIOD ENDED. PROTON EVENTS AT GREATER THAN 100 MEV AND GREATER THAN 10 MEV OCCURRED AT GEOSYNCHRONOUS ORBIT FOLLOWING THE X5/3B OF 14 JULY. THE GREATER THAN 100 MEV EVENT BEGAN AT 14/1040UT, REACHED A PEAK OF 410 PFU AT 14/1610UT, AND ENDED AT 16/0400UT. THIS WAS THE LARGEST GREATER THAN 100 MEV PROTON EVENT SEEN SINCE 1989. THE GREATER THAN 10 MEV EVENT BEGAN AT 14/1050UT AND REACHED A MAXIMUM OF 24000 PFU AT 15/1230UT. THIS EVENT, THE LARGEST OBSERVED SINCE 1991, WAS IN PROGRESS AS THE PERIOD ENDED. A POLAR-CAP ABSORPTION (PCA) EVENT WAS ASSOCIATED WITH THE PROTON EVENT. IT BEGAN AT 14/1041UT, EVENTUALLY REACHED A PEAK OF 49 DB (ESTIMATED), THEN ENDED AT 17/1943UT. A GROUND-LEVEL EVENT (GLE) ALSO FOLLOWED THE X5 FLARE AND PEAKED AT 36% ABOVE BACKGROUND AT 14/1043UT. THIS WAS ONLY THE SECOND GLE OBSERVED THIS CYCLE - THE FIRST OCCURRED IN NOVEMBER 1997. THE GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT WAS AT NORMAL LEVELS THROUGH 13 JULY. FLUX READINGS WERE NOT AVAILABLE DURING THE REMAINDER OF THE PERIOD DUE TO SENSOR CONTAMINATION RESULTING FROM THE HIGH ENERGY PROTON EVENT MENTIONED ABOVE. GEOMAGNETIC FIELD ACTIVITY WAS AT QUIET TO UNSETTLED LEVELS UNTIL A WEAK SHOCK PASSED THE ACE SPACECRAFT AROUND 10/1600UT, THEN ACTIVITY INCREASED TO UNSETTLED TO ACTIVE LEVELS. ACTIVITY INCREASED TO UNSETTLED TO MINOR STORM LEVELS ON 11 JULY FOLLOWING A SECOND SHOCK PASSAGE AT THE ACE SPACECRAFT AT 11/1125UT. ACTIVITY DECREASED TO QUIET TO UNSETTLED LEVELS AFTER 13/0300UT. QUIET TO UNSETTLED CONDITIONS PREVAILED UNTIL 13/0900UT. A SUDDEN STORM COMMENCEMENT (SSC) OCCURRED AT 13/0945UT (30 NT, AS MEASURED BY THE BOULDER USGS MAGNETOMETER) FOLLOWING A STRONG SHOCK PASSAGE AT THE ACE SPACECRAFT AT 13/0900UT. THE SSC WAS FOLLOWED BY UNSETTLED TO MAJOR STORM LEVELS WITH ISOLATED SEVERE STORM LEVELS AT HIGH LATITUDES. MULTIPLE, SHORT-DURATION MAGNETOPAUSE CROSSINGS WERE DETECTED DURING 14/1740 - 1810UT AND 14/1915 - 2000UT. ACTIVITY INCREASED TO UNSETTLED TO SEVERE STORM LEVELS DURING 15 - 16 JULY WITH SEVERE STORM LEVELS DETECTED GLOBALLY DURING 15/1200 - 16/0600UT. FIELD ACTIVITY DECREASED TO ACTIVE TO QUIET LEVELS AFTER 16/0600UT. THIS STORM WAS THE LARGEST RECORDED SINCE 1989 (PRELIMINARY AP = 152 ON 15 JULY). A FORBUSH DECREASE (PEAK DECREASE OF 8.2%) WAS OBSERVED DURING THE STORM. FORECAST OF SOLAR AND GEOMAGNETIC ACTIVITY 19 JULY - 14 AUGUST 2000 SOLAR ACTIVITY IS EXPECTED TO BE AT MODERATE TO HIGH LEVELS THROUGH 26 JULY WITH ISOLATED MAJOR FLARE ACTIVITY POSSIBLE FROM REGIONS 9077 AND 9087 (S13, L = 230, CLASS/AREA DAO/210 ON 16 JULY). ACTIVITY IS EXPECTED TO BE AT LOW TO MODERATE LEVELS DURING THE REST OF THE PERIOD THERE WILL BE A CHANCE FOR A GREATER THAN 10 MEV SOLAR PROTON EVENT AT GEOSYNCHRONOUS ORBIT THROUGH 26 JULY. THE GREATER THAN 2 MEV ELECTRON FLUX AT GEOSYNCHRONOUS ORBIT IS EXPECTED TO BE AT NORMAL TO MODERATE LEVELS THROUGH MOST OF THE PERIOD. GEOMAGNETIC FIELD ACTIVITY IS EXPECTED TO BE AT QUIET TO UNSETTLED LEVELS, BARRING AN EARTH-DIRECTED CME. .