NOAA:s Kp-forecast for Sep 26 - Oct 22
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26
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27
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This forecast was published on Sep 26, 2022.

Moon phase

26.9.-22new moon
3.10.-22first quarter
9.10.-22full moon
17.10.-22last quarter
NOAA:s Ak-forecast for Sep 26 - Oct 22
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M
26
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27
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28
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29
F
30
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01
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02
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03
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04
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05
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06
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07
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08
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09
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10
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13
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This forecast was published on Sep 26, 2022.

About this forecast

Chart above is the long term Kp-forecast published by NOAA, just shown in different format. Forecast is updated weekly, typically very early on each Monday. Original forecast can be found from here. The forecast is based on coronal holes on the surface of the sun. Those holes stay open typically about five rotations of the sun (one takes about 27 days). During that time these coronal holes can grow or shrink, or even disappear. On the other hand also new holes can form. In practise this means that the forecast is based on those coronal holes, that have existed on previous rotation(s) of the sun, and the predicted Kp-value is based on the measurements and effects of the solar wind during that time. This forecast also cannot predict any possible coronal mass ejections (CME).

Kp-value varies from 0 to 9. 0 equals average geomacnetic conditions ("quiet" background), and 9 means "giant geomagnetic storm". Ak-number changes between 0 and 400. Ak-value can be converted from Kp-values by taking each of the eight daily Kp-values (not shown in the chart above) and using conversion table to find equivalent Ak-value. The average of the sum of those eight values is daily Ak-value. Main difference between these two charts is that Kp-value means highest predicted Kp for given day, and the Ak-value means estimated average value of geomagnetic disturbances of the same day

Kp0123456789
Ak03715274880140240400

The colored bars on the charts represent highest forecasted Kp- and Ak-values for each day. The higher the bar is, the higher the forecasted value and thus also the chance for aurora to occur. However, auroras can be seen also when the forecasted value is weak, because both values are planetary, which basically means that those are averaged values for the whole planet. Local values can be something very different.

Below each bar there is highest measured Kp-values (naturally only for those days that are in the past). Kp-value is also a link to more detailed solar wind-data. Values are rounded to nearest integer, but you can see exact value if you move mouse onto the number. You can also browse old forecast and measurements from the link on the left side of the chart.