Measurements of the interplanetary solar wind during the large geomagnetic storm of April 17-18, 1965

Abstract

During the large geomagnetic storm of April 17–18, 1965, measurements of the solar wind were made with electrostatic analyzers on the Vela 2 satellites. A number of the observed solar wind changes can be related to worldwide geomagnetic changes; the most impressive event occurred after the main phase development when a fivefold increase in the solar wind density resulted in a sudden geomagnetic impulse. During the initial phase of the storm the plasma measurements were not complete, but the evidence indicates that the wind pressure increased at the time of the sudden commencement, and other features of the initial phase seem to have been related to solar wind changes. However, the main phase of the storm developed during a period when the solar wind remained relatively steady; further, there was nothing abnormal about the magnitude of the velocity, temperature, or proton density at that time. The α‐particle flux during this period was higher than usual. The storm recovery was characterized by a period of rising solar wind velocity and temperature.

The interplanetary medium and its interaction with the Earth's magnetosphere

“…The existence of tangential discontinuities in the interplanetary medium was confirmed by the magnetic field data obtained in [143] by Mariner 4, in [103,105] by Pioneer 6 and in [142] by IMP-3 and by the plasma data in [137][138][139] by Vela 2. The discontinuities were shown to be connected with sudden commencements (sc) and sudden impulses SI of the geomagnetic field.…”

“…Consequently, we expect the existence of magnetohydrodynamic discontinuities in interplanetary space. Indeed, experimental spacecraft data on the plasma and magnetic field and their theoretical analysis show the presence of different kinds of discontinuities [26,103,105,[132][133][134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151].…”

“…The magnetopause is shifted over more than the average distance, then it gradually returns to the normal level. The remarkable thing is that, during the storm period, satellites could measure the interplanetary plasma (Vela 2 [137]), the magnetic field of the interplanetary medium and the magnetosheath (OGO-1) [54], and inside the magnetosphere (Explorer 26 [263], 1964 83 C [380]) the charged particles [369,374,[381][382][383][384][385]. (Unfortunately, the particles responsible for the geomagnetic effects have not been recorded.)…”

Coronal holes, solar wind streams, and recurrent geomagnetic disturbances: 1973–1976

“…Similar, small, temporal disagreements between the high-speed streams and geomagnetic disturbances are also visible. This close, but inexact, relation between recurrent solar wind streams and geomagnetic disturbances has been recognized for some time (Snyder et al, 1963;Gosling et al, 1967).…”

Singular variations near the contact discontinuity in the theory of interplanetary blast waves

“…Thus, although there exists a difference in the prediction on the peak magnetic field in a typical explosive wave which is important in quantitatively correlating the associated cosmic-ray Forbush effect, a more detailed certification is not warranted at present in the face of other more serious uncertainties in the interplanetary dynamics. Occasional space-probe detections of flare plasmas have been reportedPioneer-V on the March 31 -April l, 1960 event (FAN et a[, 1960;COLEMAN et aI., 1960); Mariner-H on the October 7, 1962 event (ZELWER et al, 1967;SONETT et al, 1964SONETT et al, , 1966; Imp-I on the December 2, 1963 event (NEss, 1966); Vela-II on the April 17-18, 1965 event (GOSLING et al, 1967), and Explorer-33 on the July 8, 1966 event (VAN ALLEN and NESS, 1967). On the basis of inferences from data and with the exception of the March 31-April l, 1960 event, these storms appear to either possess shock waves of only finite strength or have pre-storm velocities of the solar wind too great to be ignored.…”