27-Day Geomagnetic Outlook

Long-range forecast for geomagnetic activity and aurora viewing opportunities

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What is the 27-Day Outlook?

The 27-Day Geomagnetic Outlook is a long-range forecast that predicts geomagnetic activity (measured by the Kp Index) for the next 27 days. This forecast is based on the solar rotation cycle, which is approximately 27 days—the time it takes for the Sun to complete one rotation as viewed from Earth.

Why 27 Days?

The Sun rotates on its axis approximately every 27 days. Active regions on the Sun (sunspots, coronal holes, etc.) that produce geomagnetic storms will rotate back into view after this period. By tracking these patterns, forecasters can predict when similar activity might recur.

Key Components

  • Kp Index: The largest predicted Kp value for each day (0-9 scale)
  • Radio Flux (10.7 cm): Solar radio flux measurement indicating solar activity
  • Planetary A Index: Daily geomagnetic activity index
  • Date Range: Forecast covers exactly 27 days from the issue date

How to Use This Forecast

1.
Long-Range Planning: Use this forecast to plan aurora viewing trips weeks in advance. Look for periods with predicted Kp values of 5 or higher for best viewing opportunities.
2.
Pattern Recognition: Notice recurring patterns every ~27 days as active solar regions rotate back into view.
3.
Uncertainty Awareness: Remember that long-range forecasts have lower accuracy than short-term forecasts. Use this as a guide, not a guarantee.
4.
Combined Analysis: Compare with 3-day and 7-day forecasts for more accurate near-term predictions. The 27-day outlook provides context for longer-term trends.

⚠️ Important Limitations

The 27-day outlook is based on solar rotation patterns and historical data. Actual geomagnetic activity can vary significantly due to unpredictable solar events like coronal mass ejections (CMEs) or sudden solar flares. Always check shorter-term forecasts (3-day and 7-day) for more accurate predictions as your viewing date approaches.

27-Day Forecast Chart

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Data Points: days

Date Range: -

Kp Index Scale

0-2
Quiet
3-4
Unsettled
5
Minor Storm
6
Moderate
7-9
Strong

For Aurora Viewing: Kp values of 5 or higher typically indicate good aurora viewing opportunities in Alaska. Higher values (6-9) suggest stronger, more widespread aurora activity.

Data Source

Data Source: The 27-Day Geomagnetic Outlook data is sourced from the NOAA Space Weather Prediction Center (SWPC).

Direct Data Links:

  • JSON Format (services.swpc.noaa.gov/products/27-day-outlook.json)
  • Text Format (services.swpc.noaa.gov/text/27-day-outlook.txt)

Update Frequency: The 27-Day Outlook is updated every Monday at 15:00 UTC by NOAA SWPC.