:Product: Weekly Highlights and Forecasts :Issued: 2003 Jun 03 2212 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Environment Center # Product description and SEC contact on the Web # http://www.sec.noaa.gov/weekly.html # # Weekly Highlights and Forecasts # Highlights of Solar and Geomagnetic Activity 26 May - 01 June 2003 Solar activity ranged from low to high levels. The period began at moderate levels with Region 365 (S07, L=182, class/area/mag. Dkc/880/Bgd on 29 May) producing two M-class flares on 26 May. The first, an M1/1f at 0550 UTC, was associated with a Type IV radio sweep. The second, an M1 flare at 1637 UTC, was associated with a slow, faint halo CME as seen in LASCO imagery. Region 365 was in a rapid growth phase from 26 – 29 May and developed multiple delta configurations. On 27 May, Region 365 produced two M-class flares and an X1/2b at 2307 UTC. The X1 was associated with a Tenflare (910 SFU), and Type II (650 km/s) and Type IV radio sweeps. High activity levels continued on 28 May when Region 365 produced the largest event of the period, an X3/2b at 0027 UTC with an associated Tenflare (1600 SFU), Type II (392 km/s) and Type IV radio sweeps. The intense metric and centimetric bursts associated with this X3 flare included perhaps the largest 245 MHz burst on record – maxing out sensors near 490,000 SFU. Analysis of LASCO imagery indicated that both of these X-class flares produced full halo CMEs. This region also produced eight C-class events on 28 May. Region 365 produced a third X-class event on 29 May - an X1/2b at 0105 UTC. Associated with this event were Type II (1170 km/s) and Type IV radio sweeps, and a halo CME as seen in LASCO imagery. Region 368 (S32, L=152, class/area/mag. Dao/140/B on 29 May) produced two M-class flares on 29 May: an M1/1f at 0218 UTC and an M2/1n at 1937 UTC. The M2 event was associated with a Type II (430 km/s) and Type IV radio sweep. The low activity levels observed on 30 May abruptly ended on 31 May with the onset of another major flare from Region 365. The M9/2b erupted at 31/0224 UTC and was accompanied by a mostly southwest-directed CME. The end of the period (01 June) was marked by the arrival of another considerably active sunspot group – Region 375 (N11, L=023, class/area/mag. Dao/140/B on 01 Jun), which produced three M1 flares on 1 June. Its proximity to the east limb is likely masking this region’s true size and complexity. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. There was an extended ACE outage late on the 27th through early on the 28th due to a combination of network issues and tracking problems. Solar wind speed began the period in an elevated state due to a high speed coronal hole stream. The already enhanced solar wind speed increased to near 800 km/s on the 28th due to continued high speed stream effects. On 29/1155 UTC, the first of two CMEs associated with the X-class flares from late on the 27th and early on the 28th passed the ACE spacecraft. Sharp increases in solar wind speeds to over 800 km/s were observed and significant increases in solar wind temperature and density were also associated with the passage of these CMEs. The second CME impacted ACE at 29/1830 UTC. IMF Bz turned sharply southward, exceeding –30nT for a short period, before rotating northward early on the 30th. A third CME, likely associated with the X1 flare on 29 May, encountered the ACE spacecraft at about 30/1600 UTC. The speed increase with this transient passage was significant, from just over 500 km/s to almost 900 km/s; however, the IMF structure was weak. A waning transient signature dominated through the 31st, before the onset of another high speed coronal hole stream on 1 June. There were two greater than 10 MeV proton events at geosynchronous orbit during the summary period. The first began at 28/2335 UTC, reached a 121 PFU peak at 29/1530 UTC, and ended at 30/0110 UTC. This proton event was likely associated with the X-class flares from late on the 27th and early on the 28th. The second proton event was likely associated with the M9 flare on 31 May. The start time for this greater than 10 MeV proton event was 31/0440 UTC; the peak of 27 PFU occurred at 31/0645 UTC, and the event end time was 31/1440 UTC. Greater than 100 MeV enhancements were observed during both of these greater than 10 MeV events, but the 1 PFU threshold was not exceeded. The greater than 2 MeV electron flux at geo-synchronous orbit reached high levels on the 26th and 27th and again on the 29th. The geomagnetic field ranged from quiet to severe storm levels. The period began with quiet to active levels; the disturbed periods were associated with a diminishing high speed stream. Late on 27 May, a second coronal hole high speed stream increased solar wind velocity to over 750 km/s and produced active to major storm levels with the most active periods occurring early on 28 May during local nighttime hours. On 29 May, the two CME shocks arrived from the X1 and X3 events on 27-28 May. The first shock passed the NASA/ACE spacecraft at 1150 UTC. The second and stronger CME shock passed ACE at 1830 UTC with a 125 km/s increase in solar wind speed to over 800 km/s and Bz deflections that ranged between –30 nT and +25 nT. The geomagnetic response to these transients was severe with G4 (Kp=8) storm levels at all latitudes. Storm conditions were waning when a CME shock from the X1 event on 29 May passed ACE at 30/1600 UTC. The high solar wind speed increase with this transient passage was offset by weak IMF structure; consequently, mostly active to minor storm conditions ensued. The period ended with predominantly unsettled to active levels as we transitioned into a large recurrent coronal hole. Forecast of Solar and Geomagnetic Activity 04 - 30 June 2003 Solar activity is expected to be at low to moderate levels. Moderate levels are possible early in the period from Region 375, which has already produced a number of low M-class events. Active Region 365 maintained its size and complexity as it rotated around the west limb. It will return by mid June and may produce moderate levels. A small chance for a greater than 10 MeV proton event is possible from Region 375 early in the period. The greater than 2 MeV electron flux is likely to reach high levels on 08 – 16 June and again on 20 – 24 June due to recurring high speed solar wind streams. The geomagnetic field is expected to range from quiet to active levels with occasional minor to major storm periods. A large recurrent southern coronal hole is currently in a geo-effective position and is expected to produce active to minor storm levels through the 11 June. Recurrent coronal hole high speed streams will likely produce unsettled to active conditions with isolated minor storm levels throughout the latter half of the period (17 – 30 June).