The Joint USAF/NOAA Report of Solar and Geophysical Activity, issued on February 23, 2005, provides a comprehensive analysis of solar and geophysical conditions observed between February 22 and February 23, 2005. This report, prepared jointly by the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) Space Environment Center and the U.S. Air Force, offers valuable insights into solar activity, geomagnetic conditions, and space weather forecasts during this period.

Solar Activity Analysis

During the reporting period from 2100 UTC on February 22 to 2100 UTC on February 23, 2005, solar activity was classified as low. The primary observations include:

  • Region 736 (N13W92): This sunspot region produced a C2.6 flare at 0934 UTC on February 23 as it rotated around the west limb of the Sun. The flare's classification indicates a moderate level of solar activity.
  • Newly Identified Regions: Two new sunspot regions were numbered during this period:
    • Region 737 (S07W31): Located in the southern hemisphere, this region was identified as a new sunspot group.
    • Region 738 (S10E10): Situated in the eastern hemisphere, this region was also newly numbered.

Overall, solar activity during this period remained at low levels, with no significant flares or coronal mass ejections (CMEs) observed. The solar activity forecast for the subsequent days anticipated very low to low levels of activity, consistent with the observed trend.

Geomagnetic Activity Summary

The geomagnetic field during the reporting period was predominantly quiet, with the following key observations:

  • Solar Wind Conditions: The solar wind speed at the Advanced Composition Explorer (ACE) spacecraft increased from approximately 365 km/s to 400 km/s. Despite this increase, the interplanetary magnetic field (IMF) Bz component remained positive throughout the reporting period, indicating a lack of significant geomagnetic disturbances.
  • Electron Flux Levels: The greater than 2 MeV electron flux at geosynchronous orbit reached high levels, suggesting enhanced electron activity in the Earth's magnetosphere.

Looking ahead, the geomagnetic field was expected to remain quiet to unsettled on February 24. However, a recurrent high-speed stream was anticipated to become geoeffective on February 25, leading to quiet to active conditions. On February 26, unsettled to active conditions with minor storm periods were possible at higher latitudes, as the high-speed stream continued to influence the geomagnetic environment.

Event Probabilities and Forecasts

The report provided specific probabilities for solar and geomagnetic events for the period from February 24 to February 26, 2005:

  • Solar Flare Probabilities:
    • Class M Flare: 5% chance each day (05/05/05)
    • Class X Flare: 1% chance each day (01/01/01)
    • Proton Event: 1% chance each day (01/01/01)
  • Solar Activity Forecast: The solar activity forecast for the period was classified as "green," indicating a low likelihood of significant solar events.
  • Penticton 10.7 cm Flux: The observed flux on February 23 was 85, with predicted values of 85 for February 24, 25, and 26. The 90-day mean flux was 100, reflecting a period of relatively low solar activity.
  • Geomagnetic Activity Indices:
    • Observed Afr/Ap Indices on February 22: 003/004
    • Estimated Afr/Ap Indices on February 23: 004/006
    • Predicted Afr/Ap Indices for February 24-26: 008/012, 012/015, and 012/020, respectively, indicating a gradual increase in geomagnetic activity due to the anticipated high-speed stream.
  • Geomagnetic Activity Probabilities:
    • Middle Latitudes:
      • Active: 20% on February 24, 25% on February 25, and 25% on February 26
      • Minor Storm: 10% on February 24, 15% on February 25, and 15% on February 26
      • Major-Severe Storm: 1% on February 24, 5% on February 25, and 5% on February 26
    • High Latitudes:
      • Active: 25% on February 24, 30% on February 25, and 30% on February 26
      • Minor Storm: 15% on February 24, 15% on February 25, and 20% on February 26
      • Major-Severe Storm: 5% on February 24, 5% on February 25, and 15% on February 26

Conclusion

The Joint USAF/NOAA Report of Solar and Geophysical Activity for February 23, 2005, indicates a period of low solar activity with minimal geomagnetic disturbances. The forecasts for the following days suggest a continuation of these conditions, with a slight increase in geomagnetic activity due to the anticipated high-speed solar wind stream. Such reports are essential for understanding space weather patterns and their potential impacts on satellite operations, communication systems, and other technologies sensitive to solar and geomagnetic influences.

Sources

  • Editor — Joint USAF/NOAA Report of Solar and Geophysical Activity 23 Feb 2005 —
  • Editor — Joint USAF/NOAA Report of Solar and Geophysical Activity 24 Feb 2005 —
  • Editor — Joint USAF/NOAA Report