The K-index quantifies disturbances in the horizontal component of earth’s magnetic field with an integer in the range 0–9 with 1 being calm and 5 or more indicating a geomagnetic storm. It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval.

The official planetary Kp-index is derived by calculating a weighted average of K-indices from a network of geomagnetic observatories. Since these observatories do not report their data in real-time, various operations centers around the globe estimate the index based on data available from their local network of observatories. The Kp-index was introduced by Bartels in 1939.

Today

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1

03-06h

0

06-09h

0

09-12h

1

12-15h

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15-18h

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18-21h

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21-00h

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Tomorrow

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03-06h

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09-12h

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12-15h

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15-18h

1

18-21h

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21-00h

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Day After Tomorrow

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03-06h

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06-09h

1

09-12h

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12-15h

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15-18h

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18-21h

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21-00h

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27 Day Aurora Forecast

Sep 13

2

Sep 14

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Sep 15

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Sep 16

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Sep 17

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Sep 18

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Sep 19

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Sep 20

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Sep 21

3

Sep 22

2

Sep 23

2

Sep 24

2

Sep 25

2

Sep 26

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Sep 27

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Sep 30

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Oct 01

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Oct 03

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Oct 04

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Oct 05

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Oct 06

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Oct 09

2