Alternate Definitions for Q index

I5-minute index of geomagnetic activity for high-latitude (auroral) stations. After quiet diurnal variations are removed, Q is the largest deviation scaled from the undisturbed level for the two horizontal components. (This differs from the K index, which is scaled from the largest relative deviation.) The I5-minute periods are centered on the hour and at 15, 30, and 45 minutes past each hour. The range of Q is from 0 to 11; the upper limit, in nanotesla, for each index value is given below.
Q = 0
1
2
3
4
5
6
7
8
9
10
11
10
20
40
80
140
240
400
660
1000
1500
2200
Unlimited