Type of ionospheric phenomena observed, and importance with appropriate times.
Definition of symbols:
- USIDS comes from radio Sudden IonosphericDisturbance, code S
- I I I I I = station indicator
- Y = last digit of year
- MM = month of year, 01 = January, 02 = February, etc.
- DD = UT day of month
- a = type of phenomena
- 0 = sudden frequency deviation (SFD)
- 1 = short wave fade-out with sudden drop out (typical S-SWF)
- 2 = short wave fade-out with slow drop out - 5 to 15 minutes with gradual recovery
- (slow S-SWF)
- 3 = short wave fade-out with fade irregular in drop out and recovery (G-SWF)
- 4 = sudden enhancement of atmospherics (SEA)
- 5 = sudden phase anomaly-phase advance (SPA)
- 6 = sudden cosmic noise absorption (SCNA)
- 7 = sudden enhancement of signal .15 to 200 KHz (SES)
- 8 = sudden phase anomaly-phase retardation (SPA)
Note: To report SPA by degrees, use code UABSE.
- HHmm = UT hour and minute of beginning of phenomena
- c = importance of phenomena
- 0 = importance 1-
- 1 = importance 1
- 2 = importance 2
- 3 = importance 3
- 7 = importance 1+
- 8 = importance 2+
- 9 = importance 3+
- HHmm = UT hour and minute of maximum of phenomena
- d = recording definitiveness and time qualifier
- HHmm = UT hour and minute of end time of phenomena
Note: / is to be used for data not available.