Viewing archive of Tuesday, 3 April 2001

Solar activity report

Any mentioned solar flare in this report has a scaling factor applied by the Space Weather Prediction Center (SWPC). Because of the SWPC scaling factor, solar flares are reported as 42% smaller than for the science quality data. The scaling factor has been removed from our archived solar flare data to reflect the true physical units.
Report of Solar-Geophysical Activity 2001 Apr 03 2200 UTC
Prepared by the NOAA © SWPC and processed by

Joint USAF/NOAA Report of Solar and Geophysical Activity

SDF Number 093 Issued at 2200Z on 03 Apr 2001

IA. Analysis of Solar Active Regions and Activity from 02-2100Z to 03-2100Z

Solar activity has been high. Region 9393 (N18W82) produced a spectacular flare beginning at 02/2132Z, reaching maximum at 02/2151Z and ending at 02/2203Z: the peak of the event saturated the GOES-XRS sensors, but was estimated to be X20, the largest observed so far this solar cycle. A fast coronal mass ejection (CME) was observed in association with this event. The CME appeared to be primarily headed off the west limb, but there was a deflection of material near the north polar region, suggesting that the event trajectory might have some earthward component. In the LASCO-C3 coronagraph images, this CME was overtaking the previous CME associated with yesterday's X-class event from the same region. Region 9393 also produced an M2/2f flare at 1234Z. The leading spots of 9393 are currently rotating off the solar disk. Newly assigned region 9415 (S22E72) produced an X1/1n flare at 0357Z. The event was also associated with a CME which has the signature of a partial halo event, although the bulk of the material appears to be flowing in a southeasterly direction. So far Region 9415 is showing three large penumbral clusters with an area of about 470 millionths. Solar observers report that additional spots are rotating into view behind this leading section of the region. Two new regions emerged on the disk today: Region 9416 (N17W18) and Region 9417 (S10E43). Region 9408 (S08W46) showed some growth during the past 24 hours but was relatively stable.
IB. Solar Activity Forecast
Solar activity is expected to be high. Region 9393 will continue to be a threat for major flares and proton events during the next three days, although the probabilities will decrease as it rotates around the solar limb. Region 9415 has also clearly shown major flare potential and is expected to be a source of M-class flares and probably additional isolated X-class flares.
IIA. Geophysical Activity Summary 02-2100Z to 03-2100Z
The geomagnetic field ranged from quiet to active levels. Quiet to unsettled levels prevailed for most of the day, but there was an active period from 02/2100-2400Z. An energetic proton event resulted from the X20 flare. Greater than 10 MeV particles exceeded event threshold at 02/2340Z, and reached a maximum of 1,110 PFU at 0745Z. The 10 MeV particle event continues in progress with 308 PFU at forecast issue time. Greater than 100 MeV particles also exceeded thresholds, beginning at 03/0120Z, reaching maximum of 5.4 PFU at 03/0740Z, The greater than 100 MeV particles dipped below threshold around 03/1900Z and appeared to be staying below threshold as of 03/2050Z.
IIB. Geophysical Activity Forecast
The geomagnetic field is expected to increase to minor to major storm levels during the next 24 hours. The two recent CMEs from region 9393 are likely to have combined by now, and the size and possible partial earthward component of the 2nd CME create the expectation of some interaction at Earth. The response is less certain than in the case of a full-halo CME and probably less dramatic than the result of a direct, head-on hit. The forecast is for minor storm levels at the mid-latitudes, with major storm levels at the higher latitudes. Minor storm conditions are expected to persist through the second day. Additional activity, most likely reaching active levels, is possible on the third day due to a glancing blow from the CME from region 9415. The greater than 10 MeV proton event is expected to persist through most of tomorrow.
III. Event Probabilities 04 Apr to 06 Apr
Class M85%80%70%
Class X35%30%20%
PCAFin progress
IV. Penticton 10.7 cm Flux
  Observed       03 Apr 223
  Predicted   04 Apr-06 Apr  215/205/195
  90 Day Mean        03 Apr 166
V. Geomagnetic A Indices
  Observed Afr/Ap 02 Apr  012/020
  Estimated     Afr/Ap 03 Apr  010/012
  Predicted    Afr/Ap 04 Apr-06 Apr  035/060-035/040-020/020
VI. Geomagnetic Activity Probabilities 04 Apr to 06 Apr
A. Middle Latitudes
Minor storm30%30%15%
Major-severe storm25%15%10%
B. High Latitudes
Minor storm35%35%20%
Major-severe storm35%30%15%

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