Cosmic ray intensity variations in Antarctica
References
20
Baker, M. B., A. J . Masley, and P. R. Satterhlom. 1972. Polar riometer observations of the August 1972 solar proton events. American Geophysical Union, E S Transactions, 53: 1056. Kane, S. R., and A. J . Masley. 1969. The relationship between polar riometer and solar cosmic ray measurements in space. American Geophysical Union, E S Transactions, 50: 463. Kane, S. R., and A. J . Masley. 1973. The relationship between polar riometer and space measurements during solar cosmic ray events. McDonnell Douglas Astronautics Company, Paper WD 1030. 22 p. Masley, A. J . , and M. B. Baker. 1972. August 1972 solar particle intensities. American Geophysical Union, E S Trans. actions, 53: 1056.
Iz LU U
15
lO
ta 5
a.
0 U,
Z LU I-
C-) 0 LU
C-) Z
-5 -10 -IS
-20 -25 -30 -35
5 6 7 8 9 10 II AUGUST, 1972 Figure 1. Nucleonic intensity at the South Pole during the August 1972, record-breaking cosmic ray storm. The magnitudes of the galactic ray intensity reductions (Forbush decreases) and of the relativistic solar particle fluxes (ground level events) exceeded those at any other earth station. 3 4
Cosmic ray intensity variations in Antarctica
MARTIN A. POMERANTZ
and
an increase that significantly was above the pre-storm level. This meant that, at first sight, the August 4 fluctuations at these stations appeared to constitute the usual precursor associated with the second Forbush decrease,
SHAKTI P. DUGGAL
Bartol Research Foundation of The Franklin Institute Last year's review (Pomerantz and Duggal, 1972) reported the observation, on September 1, 1971, of an exceedingly rare event: the arrival of solar cosmic rays produced on the sun's invisible disk, far beyond the limb. The abnormal and unexpected north-south asymmetry, manifested by the significant difference in the McMurdo-Thule intensity vs time profiles, stimulated an intensive analytical study. The surprising results of this recently completed analysis (Duggal and Pomerantz, in press) are having great impact upon our basic understanding of important solar phenomena. The most exciting occurrence during 1972 was a record-breaking cosmic ray storm that commenced on August 4, 1972 (Pomerantz and Duggal, 1973). The magnitude of all of its features was greater at South Pole Station than at any other station in the world. Fig. 1 shows that (in addition to the enormous galactic cosmic ray flux reduction, reflected in a total diminution of the nucleonic intensity of about 35 percent) there were two ground level events (GLE) representing the arrival of relativistic solar particles. Because there was not a normal time association between GLE-1 and an appropriate solar flare, it unambiguously was identifiable only in the data from South Pole Station (Pomerantz and Duggal, in press). In fact, as fig. 2 shows, the sea level polar stations Thule and McMurdo did not reveal 240
South Pole
AUGUST 4)1972
I-
2 L*J U
cr Ui aI—
Cl)
2 Ui I.2
0 Z 0 Lii
5
-J
,Thule
0
2
Ei
jk McMurdo'7
IL)
le 14 lb 115 eu UNIVERSAL TIME
Figure 2. Observations of ground level event 1 on an expanded scale, as recorded at several polar stations. Because nucleonic intensity at the South Pole exceeded the pre-storm level 10 percent), this feature represented the arrival of relativistic solar cosmic rays. ANTARCTIC JOURNAL
McMurdo - South Pole
AUGUST 5, 1972
Duggal, S. P., and M. A. Pomerantz. In press. Anisotropies in relativistic cosmic rays from the invisible disk of the sun. Journal of Geophysical Research. Pomerantz, M. A., and S. P. Duggal. 1972. Cosmic ray intensity variations in Antarctica. Antarctic Journal of the U.S., VI1(5): 162-163. Pomerantz, M. A., and S. P. Duggal. 1973. Record-breaking cosmic ray storm stemming from solar activity in August 1972. Nature, 241: 331-332. Pomerantz, M. A., and S. P. Duggal. In press. Remarkable cosmic ray storm and associated relativistic solar particle events of August 1972. Journal of Geophysical Research.
0300 0400 0500 0600 UNIVERSAL TIME
Figure 3. Plot of the 6-minute average percentage increase from minimum intensity at South Pole and McMurdo Stations during the recovery phase of Forbush decrease 2. The data were normalized by dividing the South Pole values by 1.65. Tracking of the two profiles proves that no burst of relativistic solar cosmic rays accompanied the pulse of low energy particles detected during this period by instruments placed aboard spacecraft. FD-2. Analysis of the high time resolution data disclosed that a burst of about 68 percent was registered in a 10-minute interval at the South Pole. GLE-2 on August 7, 1972, was highly anisotropic and generally appeared to be 'typical," in marked contrast with its highly unusual predecessor (GLE-1) that was characterized by an abnormally steep spectrum, and consequently by a velatively short atmospheric absorption mean free path. A distinct north-south asymmetry occurred during the on-set phase of FD-1 and throughout FD-2, with minimum intensity in the Antarctic. The maximum modulation of the galactic flux during FD-2 occurred somewhere near 60 0 west of the sun-earth line. The pulse-like sharp recovery between 0300 to 0500 Universal Time on August 5 was coincident with a sudden rise in the considerably lower-energy solar particles recorded by detectors aboard spacecraft. However, as illustrated in fig. 3, comparison of data recorded at McMurdo and South Pole Stations proves that the cosmic ray spectrum at this time did not differ from that which prevailed during the cosmic ray storm immediately before and after this period (Pomerantz and Duggal, in press), leading to the undisputable conclusion that no detectable flux of particles with relativistic energies simultaneously was reaching the earth. This work was supported by the National Science Foundation.
References
Duggal, S. P., and M. A. Pomerantz. 1973. Relativistic cosmic rays from the sun's invisible disk. Proceedings of the 13th International Conference on Cosmic Rays. September-October 1973
VLF electrical properties of the ice sheet measured at Byrd Station J . C. ROGERS
Geophysical Institute University of Alaska I, C. PEDEN
Department of Electrical Engineering University of Washington This article summarizes results of the first in situ measurements of the dielectric and loss properties (complex permittivity parameters) of deep antarctic ice, as functions of vertical depth. In 1968, the U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, successfully completed the first drill hole to the bottom of the ice sheet at Byrd Station (Gow ci al.. 1968). The results, summarized here, are of interest to glaciologists as well as to polar scientists studying radio propagation over the ice cap in the VLF range, the polar ionosphere, and the operation Of vi.F antennas in the antarctic environment. During the 1969-1970 austral summer, an electrically short dipole probe with encapsulated instrumentation was used in the 2 164 ' -meter-deep drill hole, to obtain measured probe admittances at 5 discrete VLF frequencies (1.25, 2.5, 5, 10, and 20 kilohertz). Direct measurements were made down to the 1500-meter level, and the dielectric properties later were extrapolated to the bottom of the ice sheet. The latter procedure was necessitated by closure of the lower 30 percent of the drill hole before the experiment could be performed (Peden and Rogers, 197 1). Permittivity properties of the fluid in the drill hole also were measured as functions of depth, as was the hole diameter (Rogers and Peden, 1972). Using these data, the input admittance of the fluid-sheathed probe can be related unambiguously to the relative complex permittivity of the ice external to the sheath (Rogers and Peden, 1973). A simple 3-element equivalent circuit 241
20
Baker, M. B., A. J . Masley, and P. R. Satterhlom. 1972. Polar riometer observations of the August 1972 solar proton events. American Geophysical Union, E S Transactions, 53: 1056. Kane, S. R., and A. J . Masley. 1969. The relationship between polar riometer and solar cosmic ray measurements in space. American Geophysical Union, E S Transactions, 50: 463. Kane, S. R., and A. J . Masley. 1973. The relationship between polar riometer and space measurements during solar cosmic ray events. McDonnell Douglas Astronautics Company, Paper WD 1030. 22 p. Masley, A. J . , and M. B. Baker. 1972. August 1972 solar particle intensities. American Geophysical Union, E S Trans. actions, 53: 1056.
Iz LU U
15
lO
ta 5
a.
0 U,
Z LU I-
C-) 0 LU
C-) Z
-5 -10 -IS
-20 -25 -30 -35
5 6 7 8 9 10 II AUGUST, 1972 Figure 1. Nucleonic intensity at the South Pole during the August 1972, record-breaking cosmic ray storm. The magnitudes of the galactic ray intensity reductions (Forbush decreases) and of the relativistic solar particle fluxes (ground level events) exceeded those at any other earth station. 3 4
Cosmic ray intensity variations in Antarctica
MARTIN A. POMERANTZ
and
an increase that significantly was above the pre-storm level. This meant that, at first sight, the August 4 fluctuations at these stations appeared to constitute the usual precursor associated with the second Forbush decrease,
SHAKTI P. DUGGAL
Bartol Research Foundation of The Franklin Institute Last year's review (Pomerantz and Duggal, 1972) reported the observation, on September 1, 1971, of an exceedingly rare event: the arrival of solar cosmic rays produced on the sun's invisible disk, far beyond the limb. The abnormal and unexpected north-south asymmetry, manifested by the significant difference in the McMurdo-Thule intensity vs time profiles, stimulated an intensive analytical study. The surprising results of this recently completed analysis (Duggal and Pomerantz, in press) are having great impact upon our basic understanding of important solar phenomena. The most exciting occurrence during 1972 was a record-breaking cosmic ray storm that commenced on August 4, 1972 (Pomerantz and Duggal, 1973). The magnitude of all of its features was greater at South Pole Station than at any other station in the world. Fig. 1 shows that (in addition to the enormous galactic cosmic ray flux reduction, reflected in a total diminution of the nucleonic intensity of about 35 percent) there were two ground level events (GLE) representing the arrival of relativistic solar particles. Because there was not a normal time association between GLE-1 and an appropriate solar flare, it unambiguously was identifiable only in the data from South Pole Station (Pomerantz and Duggal, in press). In fact, as fig. 2 shows, the sea level polar stations Thule and McMurdo did not reveal 240
South Pole
AUGUST 4)1972
I-
2 L*J U
cr Ui aI—
Cl)
2 Ui I.2
0 Z 0 Lii
5
-J
,Thule
0
2
Ei
jk McMurdo'7
IL)
le 14 lb 115 eu UNIVERSAL TIME
Figure 2. Observations of ground level event 1 on an expanded scale, as recorded at several polar stations. Because nucleonic intensity at the South Pole exceeded the pre-storm level 10 percent), this feature represented the arrival of relativistic solar cosmic rays. ANTARCTIC JOURNAL
McMurdo - South Pole
AUGUST 5, 1972
Duggal, S. P., and M. A. Pomerantz. In press. Anisotropies in relativistic cosmic rays from the invisible disk of the sun. Journal of Geophysical Research. Pomerantz, M. A., and S. P. Duggal. 1972. Cosmic ray intensity variations in Antarctica. Antarctic Journal of the U.S., VI1(5): 162-163. Pomerantz, M. A., and S. P. Duggal. 1973. Record-breaking cosmic ray storm stemming from solar activity in August 1972. Nature, 241: 331-332. Pomerantz, M. A., and S. P. Duggal. In press. Remarkable cosmic ray storm and associated relativistic solar particle events of August 1972. Journal of Geophysical Research.
0300 0400 0500 0600 UNIVERSAL TIME
Figure 3. Plot of the 6-minute average percentage increase from minimum intensity at South Pole and McMurdo Stations during the recovery phase of Forbush decrease 2. The data were normalized by dividing the South Pole values by 1.65. Tracking of the two profiles proves that no burst of relativistic solar cosmic rays accompanied the pulse of low energy particles detected during this period by instruments placed aboard spacecraft. FD-2. Analysis of the high time resolution data disclosed that a burst of about 68 percent was registered in a 10-minute interval at the South Pole. GLE-2 on August 7, 1972, was highly anisotropic and generally appeared to be 'typical," in marked contrast with its highly unusual predecessor (GLE-1) that was characterized by an abnormally steep spectrum, and consequently by a velatively short atmospheric absorption mean free path. A distinct north-south asymmetry occurred during the on-set phase of FD-1 and throughout FD-2, with minimum intensity in the Antarctic. The maximum modulation of the galactic flux during FD-2 occurred somewhere near 60 0 west of the sun-earth line. The pulse-like sharp recovery between 0300 to 0500 Universal Time on August 5 was coincident with a sudden rise in the considerably lower-energy solar particles recorded by detectors aboard spacecraft. However, as illustrated in fig. 3, comparison of data recorded at McMurdo and South Pole Stations proves that the cosmic ray spectrum at this time did not differ from that which prevailed during the cosmic ray storm immediately before and after this period (Pomerantz and Duggal, in press), leading to the undisputable conclusion that no detectable flux of particles with relativistic energies simultaneously was reaching the earth. This work was supported by the National Science Foundation.
References
Duggal, S. P., and M. A. Pomerantz. 1973. Relativistic cosmic rays from the sun's invisible disk. Proceedings of the 13th International Conference on Cosmic Rays. September-October 1973
VLF electrical properties of the ice sheet measured at Byrd Station J . C. ROGERS
Geophysical Institute University of Alaska I, C. PEDEN
Department of Electrical Engineering University of Washington This article summarizes results of the first in situ measurements of the dielectric and loss properties (complex permittivity parameters) of deep antarctic ice, as functions of vertical depth. In 1968, the U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, successfully completed the first drill hole to the bottom of the ice sheet at Byrd Station (Gow ci al.. 1968). The results, summarized here, are of interest to glaciologists as well as to polar scientists studying radio propagation over the ice cap in the VLF range, the polar ionosphere, and the operation Of vi.F antennas in the antarctic environment. During the 1969-1970 austral summer, an electrically short dipole probe with encapsulated instrumentation was used in the 2 164 ' -meter-deep drill hole, to obtain measured probe admittances at 5 discrete VLF frequencies (1.25, 2.5, 5, 10, and 20 kilohertz). Direct measurements were made down to the 1500-meter level, and the dielectric properties later were extrapolated to the bottom of the ice sheet. The latter procedure was necessitated by closure of the lower 30 percent of the drill hole before the experiment could be performed (Peden and Rogers, 197 1). Permittivity properties of the fluid in the drill hole also were measured as functions of depth, as was the hole diameter (Rogers and Peden, 1972). Using these data, the input admittance of the fluid-sheathed probe can be related unambiguously to the relative complex permittivity of the ice external to the sheath (Rogers and Peden, 1973). A simple 3-element equivalent circuit 241
