Characteristics and fine structure of the large cosmic-ray fluctuations in November 1960

Abstract

Measurements obtained at Deep River, Canada, from two large neutron monitors, and at Cambridge, Massachusetts, from a high counting rate meson monitor, during the solar cosmic-ray injections of November 12 and 15, 1960, are reported. In addition, rate-meter pen traces of the neutron increases and a magnetometer trace of H, obtained at Deep River, are reproduced. The solar cosmic-ray increase of November 12 appears to be unique in that while it was in progress a sharp Forbush decrease happened to occur as shown by the MIT meson intensity. Half an hour before the onset of the Forbush decrease, and coincident with a conspicuous increase of H, the intensity of the solar cosmic radiation doubled and then exhibited strong rapid oscillations. We advance arguments that the changes of intensity of the solar cosmic ray• observed at high latitudes at the time of the magnetic disturbance and Forbush decrease are due to the earth sampling solar cosmic rays trapped in the gas cloud responsible for these latter effects. The events of November 12 and 15 are both shown to be in agreement with a recent model for the magnetic fields in the inner solar system. At the time of the solar cosmic-ray increase of November 15, the earth was already inside a trapping region, and periodic oscillations of the solar cosmic-ray intensity were observed lasting for about 2 hours. It is suggested that these oscillations may be closely connected with the storage mechanism. 1363 1364 STELJES, CARMICHAEL, AND McCRACKEN over an hour to reach the same fraction of its initial maximum intensity. A r•markable succession of fluctuations of the solar cosmic rays of periodicity about 20 minutes, lasting for slightly more than 1 hour after the beginning of the November 15 increase, was observed at Deep River. In view of these interesting features it seems worth while to describe and discuss the observations without waiting for data from other cosmicray stations. It has recently been shown [McCracken and Palmetra, 1960; Obayashi and Hakura, 1960] that previously observed solar flare cosmic-ray effects are in agreement with a simple model for the magnetic fields in the inner solar system. We shall present the experimental data from both Deep River and MIT and show that the same model provides a good explanation of the November events as observed at our laboratories. We shall not, in this paper, try to apply any further tests of the model requiring detailed data from elsewhere in the world, but we shall make some general predictions of what may have been observed elsewhere. We shall also describe the newly observed fast fluctuations in detail and discuss their possible significance. The model is the one originally suggested by Cocconi, Gretsch, Morrison, Gold, and Hayakawa [1958] at Varenna in 1957. This model has since then been strongly advocated by Gold [1959], for example, at the 1959 'Symposium on the Exploration of Space.' INSTRUMENTS Deep River Laboratory. The Deep River Laboratory is 145 m above sea level at 46.10øN. Lat. and 77.50øW. Long. The geomagnet...

The 1859 space weather event revisited: limits of extreme activity

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High frequency of occurrence of large solar energetic particle events prior to 1958 and a possible repetition in the near future

“…The neutron monitor network has observed ∼70 GLE since 1956; however, all but three were one or two orders of magnitude less intense than the GLE of 23 February 1956. The comprehensive ionization chamber and neutron monitor data for the GLE of 23 February 1956 provides an intercalibration between the ionization and neutron monitor records of GLE, and threshold levels were further refined using the data obtained during the GLE in November 1960 [ Steljes et al , 1961].…”

Terrestrial cosmic ray intensities

“…[33,34]. The inverse of the hadron flux attenuation length is plotted in units of percent/mm of Hg-see the ordinate values on the right side of the plot to convert to an attenuation length in units of g/cm^The plot shows attenuation length vs. altitude and vs. geomagnetic rigidity, with both the calculations and the many data points coming together with remarkable consistency.…”

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