In the 12 hours following a worldwide storm sudden commencement at 0027 UT on July 29 there was a series of at least four magnetospheric substorms, the last and largest of which exhibited an expansion phase onset at ∼1200 UT. Data from six spacecraft in three general local time groupings (0300, 0700, and 1300 LT) were examined, and vector magnetic field data and energetic electron and ion data from ∼15 keV to >2 MeV were employed. Four primary types of studies were carried out: (1) timing and morphology of energetic particle injections; (2) variation of particle phase space densities f(µ = p²/2mB), using local magnetic field and particle flux data; (3) measurement of boundary motions, using high‐energy ion gradient anisotropies; and (4) adiabatic modeling, which included injection, large‐scale convection, corotation, and gradient drifts. For the 1200 UT substorm it is concluded that there was a substantial flux dropout in a broad sector near local midnight because of a large‐scale boundary motion, followed by a recovery to a predropout configuration. There were then several subsequent injection events with distinct onsets (extending as far eastward as 0300 LT), for which ion anisotropy information suggests an inward motion of particles from outside of geostationary orbit. Particle drift information reveals that these particles drifted azimuthally completely around the earth. It is also concluded from the phase space density studies that ‘fresh’ particles with magnetic moments of up to at least several hundred MeV/gauss were injected near geostationary orbit. The present adiabatic convection model can explain the observed injection of large magnetic moment particles from the plasma sheet into synchronous orbit, although physical elements of the normal model must be altered somewhat.

No abstract

A significant increase in solar cosmic-ray activity began in early 1966. During the period from March 1966 to June 1967, 14 events were observed. This can be compared to one event in 1964 and one event in 1965. Events in 1966 occurred on 24 March, 7 July, 28 August, 2 September, and 14 September. Events in 1967 include those of 28 January, 2 February, 7 February, 13 February, 11 March, 23 March, 23 May, 28 May, and 6 June.The 2 September 1966 event, reaching a maximum of 13 dB (~105/cm2 s > 2 MeV), was the largest observed since July 1961. The 23 May 1967 event, with 11 dB, reached maximum absorption 35 hours after first observation. The 28 January 1967 event exhibits several interesting features. There is an apparent lack of a visible flare. Low-energy particles were observed for several hours before neutron monitors observed an event in excess of 15%, representing a low-energy precursor to the high-energy event. Details of these events are discussed. Parameters related to acceleration and propagation such as delay times and intensity–time profiles, effects related to other geophysical phenomena, and comparisons with satellite observations are also included. This paper is based on 30-MHz riometer observations at the Douglas Observatories located at McMurdo, Antarctica, and Shepherd Bay, N.W.T., Canada (80° geomagnetic latitude). The measured absorption is proportional to the square root of the particle intensity.

A series of balloon flights was con. ducted at Minneapolis, Minnesota, during the solar cosmic-ray events from April 1, 1960, through April 30, 1960. The largest event on April 1 was recorded by a balloon at high altitude, and for a power-law spectrum of the solar protons the exponent • was determined to be 2.4. This spectrum, when extrapolated, agrees with the rates measured by the earth satellite Explorer ? for the same event. It is shown that at Minneapolis a partial geomagnetic cutoff was in effect that limited the low-energy particles detected at balloon levels. Comparison of the simultaneous readings of the Pioneer 5 deep space probe confirms this picture. A relationship is established between the Deep River neutron monitor and various balloon instruments at high altitude, and the proportionality is determined during a large Forbush decrease. The event on April 28 was also detected at Minneapolis with balloons, and the data are consistent with time variations in the local geomagnetic cutoff. The paper includes many details of the construction of the ion chambers, counters, and telemetry system used for the balloon monitoring program at Minnesota.

An observation has been made with balloon detectors of a radiation increase that can be identified with certainty as a burst of bremsstrahlung originating on the sun during a class 2+ flare. The observation was made simultaneously with identical detectors on a balloon at Minneapolis, Minnesota, at 45° geographic latitude, and at Fort Churchill, Manitoba, Canada, at 58.5° geographic latitude and essentially at the same longitude of 95°W. The instruments consisted of an aluminum‐walled ionization chamber filled with argon gas operating on the pulsing electrometer system, an aluminum Geiger counter, and a copper Geiger counter. The two counters were also electronically connected to form a vertical coincidence train.