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Geomagnetic storm on 21 Sep 1977 (G3)

Max Kp7+G3

Ap64No. 3 in 1977

Consecutive G1+ days5

Ap rank507since 1932

Kp by 3-hour slot (UTC)

00–034+

03–065+

06–096o

09–127-

12–155-

15–183-

18–214+

21–247+

The days around it

Date	Max Kp	Ap	Level
18 Sep 1977	3o	6	–
19 Sep 1977	6o	42	G2
20 Sep 1977	6-	44	G2
21 Sep 1977	7+	64	G3
22 Sep 1977	7-	63	G3
23 Sep 1977	5o	21	G1
24 Sep 1977	4-	12	–

Highest-Ap days of 1977

2 Dec 197769

2 May 197766

21 Sep 197764

22 Sep 197763

27 Oct 197762

29 Jul 197761

6 Apr 197749

7 Apr 197748

19 Apr 197748

28 Oct 197747

Dates and time slots are UTC. Kp is the 3-hourly planetary geomagnetic index (0–9); Ap is the daily average disturbance. G1–G5 follow the NOAA storm scale (Kp 5- and above counted as G1). Aurora visibility also depends on weather and location. The latest values are preliminary.

← 29 Jul 1977 22 Sep 1977 →

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Max Kp 7+, Ap 64: No. 507 of 34,615 days since 1932 by Ap.