134 PRINCIPAL MAGNETIC STORMS

WATHERO0 MAGNETIC OBSERVATORY

JXNUAR¾ TO MXRCa, 1944

(Latitud, 30 ø 19'.1 S., longitude 115 ø 52'.6 or 7 h 43m.5 E. of Gr.)

February 7-g--This small disturbance began at about 05 h GMT, February 7. There was no sudden commencement, but the traces gradually became more disturbed, reaching their greatest activity at 12 h 50 m when there were large peaks in D and Z and a considerable bay in H until 13 a 26 m. During this interval the range in//was 103 gammas, in D 11'.5, and in. Z 99 gammas. There was a smaller series of peaks and bays between 15 h and 16 h 30m; however apart from this feature the disturbance gradually subsided until normal conditions again prevailed at 24 h February 8. Ranges- .D, 20'.0; H, 113 gammas; Z, 147 gammas.

March 26-27--.At 02 h 00 m GMT, March 26, there was a fairly rapid but small movement which may have marked the commencement of the storm, although it does not possess the usual features of a sudden commencement. Only slight variations from normal values were re- corded for the next nine hours; between 11 h 30 m and 14 h 30 TM there was a series of peaks and bays in all three elements after which there was a quiet period lasting eight hours. At 23 h 19 TM very rapid motions began in D, tt, and Z which lasted until 07 h March 27. The mean hourly values of the elements did not depart markedly from normal during this period; however there was continuous and rapid motion and /-/was slightly lower than usual. During the following nine hours the mvvements became more leisurely and the disturbance subsided by !6 • March 27. Ranges: D, 19'.5; H, 154 gammas; Z, 114 gammas.

W. C. Px•K•soN, Observer-in-Charge

HERMANUS MAGNETIC OBSERVATORY

OCTOBER TO DECEMBER, 1943

(Latitude 34 ø 25'2 S., longitude 19 ø 13'.5 or 1 •' !6m.9 E. of Gr.)

October I-5--The disturbances which began at midday of Greenwich date September 26 continued until midday October 5. During the period from October ! to October 5 the maximum K-index was 5 for each of the three-hour periods 12h-15 k, October 1, and 12•-15 h and 18 •- 21•, October 2.

October 7-I3--A gradual-commencement disturbance which began at about 06 h 30 ra GMT, October 7, continued until 03 h, October 13. The maximum K-index during this period was 5 for each of the three- hour periods 09h-12 h and 21•-24 h, October 8, and 18•-21 h, October 9.

October 16--Micropulsations on all traces began at 21 h GMT, October 16, and continued for about an hour.

October 20--2The K-index was 5 for each of the two three-hour periods from 15h-21 •, October 20.

October 22-November l•Gradual-commencement disturbances which began at about 06 • 30 • GMT, October 22, continued until 03 h, No- vember 1. During this time the maximum K-index was 5 for each of

PRINCIPAL M'A GNETIC STORMS 135

the following three-hour periods: 09•-12 •, October 22; 09h-15 • and 18•-21 h, October 24; 15h-21 h, October 26; •-21 h, October 28; 18•-21 • October 29; 12•-15 •, October 30; 12h-151•8 and 18•-21 •, October 311 The greatest range in H was 113 gammas on October 26.

November 4-$•Disturbances which began at about 13 h GMT, November 4, continued until 03 •, November 8. The maximum/i-index was 6 for the three-hour period 15•-18 •, November 6. The K-index was 5 for the periods 21h-24h, November 6, and 09a-12 •, November 7.

November i2-16•There were micropulsations on all traces from 19 h to 19 h 30 TM GMT, November 12, from 17 h 40 m to 18 h 00 m, Novem- ber 14, and from 01 a 50 • to 02 • 40 m, November 16.

November l$-19•Disturbances which began fairly abruptly at 13 h 21TM GMT, November 18, continued until 21•, November 29. There were many micropulsations from 03 • to 16 •, November 19, and the dis- turbances during this period were very oscillatory. The maximum K-index was 6 for the three-hour period 09h-12 h, November 19. The K-index was 5 for each of the following three-hour periods' 06•-09 •, 12•-15 •, and 21•-24 h, November 19; 00•-03 • and 15h-21 h, November 21; 12•-15h and 21 h-24 h, November 23; 18•-21 h, November 25; 12 •-24 •, November 26.

December 1-5•A gradual-commencement disturbance began at about 12 h GMT, December 1, and continued until 21h, December 5. The maximum K-index was 5 in each of the three-hour periods 15•-21 •, December 2, and 18h-21 h, December 3.

December 15-26•Gradual-commencement disturbances which began at about 09 • GMT, December 15, continued until 22 •, December 26. The disturbances were not of large range but were very oscillatory. The maximum K-index was 5 for each of the three-hour periods 15 •-21 •, December 19. There were micropulsations from 02 h 35 TM to 03 • 00 TM and from 03 h 35 m to 04h 00 TM, December 25.

December 29----There were micropulsations on all traces from 02 h 15 TM to 03 h 00 TM GMT, December 29. The D-pulsations were the strongest.

A. OGG, Magnetic. Survey Adviser

APIA OBSERVATORY

jANUARY TO MARCH, 1944 (Lotitude 13 ø 48'.4 S., longitude 171 ø 46'.5 or I1 • 27.1TM W. of Gr.)

February 13-14mtt became disturbed at 23 h 00 TM GMT, February !3. A maximum was reached at 00 h 19 m, February 14, and decreased steadily to a minimum at 07 h 05 m. After this the intensity increased with fluc- tuations to 14 h 06 TM, when the trace became normal. D and Z were slightly disturbed. Range in H was 155 gammas.

March 26-27--H became disturbed at 23 • 06'" G•IT, March 26, and continued so until 12 h 03 m, March 27. The maximum in H was reached at 23 h 09 TM, March 26, and the minimum at 06 • 00 m, March 27. Z was disturbed over the same period with a minimum at 00 h 36 m, March 27, and a maximum at 09 h 27 TM, March 27. Ranges: tt, 146 gammas; Z, 34 gammas.

H. B•uc• S,xrsro•), Acting Director