Corotating shock structures

Consideration of observed interplanetary shocks leads to the conclusion that a corotating forward shock has not been unambiguously identified at 1 AU. A reverse shock identified in September 1967 is a likely candidate for a corotating structure

Some contributions to knowledge of the magnetospheric plasma by ISEE investigators

The ISEE project has made substantial contributions to the knowledge of the magnetosphere during the period of the IMS, especially in the discipline of Space Plasma Physics. Results obtained during approximately the first two years of the operation of ISEE-1 and -2, and touches on relevant results of ISEE-3 are reviewed. The ability to control the separation between ISEE-1 and -2, which are in nearly identical orbits, has permitted study of the motion and structure of the bow shock and magnetopause, the boundary layers, and the plasma sheet. Much evidence was obtained favoring the existence of reconnection and its relevance to the transfer of magnetic flux from the frontside to the rear of the magnetosphere, although not everyone agrees that it is the only important process. The presence of both reflected and accelerated particles was shown to lead to the development of a foreshock region between the bow shock and the interplanetary magnetic field line tangential to it

The solar cycle variation of the solar wind helium abundance

A critical survey was made of the experimental evidence for a variation of the relative abundance by number h, (n alpha/np), of helium in the solar wind. The abundance is found to vary by delta h = 0.01 + or - 0.01 from 0.035 to 0.045 over solar cycle 20. Changes in the average bulk speed during the solar activity cycle was insufficient to account for this increase in h with the solar cycle. The slope of the linear relation between h and the plasma bulk speed is also found to vary, being greatest around solar maximum. An attempt is made to explain the 30% variation in h as the result of the variation in the number of major solar flares over a solar cycle. These obvious transients are apparently not numerous enough to explain the observed variation, but the reasonable expectation remains that the transients observed recently by Skylab which may occur more frequently than major flares could augment those associated with major flares. Since the solar wind flux is not observed to increase at solar maximum, the abundance of Helium cannot be proportional to the proton flux leaving the sun unless the solar wind comes from a smaller area of the sun at maximum than at minimum

First results from the six-axis electron spectrometer on ISEE-1

A survey, using results from the first 25 orbits of ISEE-1, was made of some aspects of electrons in the dawn magnetosheath. There are indications that the flow of plasma is not uniformly turbulent over this region. The electron heat flux is observed to be directed away from the shock and to have an average value of about twice the interplanetary heat flux. Many magnetopause crossings were observed and usually resemble abrupt transitions from one well-defined plasma state to another. The ejection of plasma from flux tubes convected up against the magnetopause is observed for about half the time, and its thickness and dependance on the solar wind Mach number agrees with theoretical predictions. A full traversal of the whole forward hemisphere of the magnetosheath is required to fully confirm these deductions

A discussion of interplanetary post-shock flows with two examples

Plasma and magnetometer observations are described for two flare-associated shock flows and the comparison of them with models. One represents a class of flows where the shock is followed by a stream and separated from it by a region in which density temperature and speed decrease monotonically. The other is characterized by a complex region between the shock and the following stream, which has many discontinuities and fluctuations, but in which there is no increase in helium concentration. These two types of flow can be distinguished using ground magnetograms, since the former shows no sudden impulses following the shock, whereas the latter shows many

Acceleration of protons by interplanetary shocks

Acceleration of protons by interplanetary shock

Quasi-periodic oscillations, trapped inertial waves and strong toroidal magnetic fields in relativistic accretion discs

The excitation of trapped inertial waves (r-modes) by warps and eccentricities in the inner regions of a black hole accretion disc may explain the high-frequency quasi-periodic oscillations (HFQPOs) observed in the emission of Galactic X-ray binaries. However, it has been suggested that strong vertical magnetic fields push the oscillations' trapping region toward the innermost stable circular orbit (ISCO), where conditions could be unfavourable for their excitation. This paper explores the effects of large-scale magnetic fields that exhibit \textit{both} toroidal and vertical components, through local and global linear analyses. We find that a strong toroidal magnetic field can reduce the detrimental effects of a vertical field: in fact, the isolation of the trapping region from the ISCO may be restored by toroidal magnetic fields approaching thermal strengths. The toroidal field couples the r-modes to the disc's magneto-acoustic response and inflates the effective pressure within the oscillations. As a consequence, the restoring force associated with the vertical magnetic field's tension is reduced. Given the analytical and numerical evidence that accretion discs threaded by poloidal magnetic field lines develop a strong toroidal component, our result provides further evidence that the detrimental effects of magnetic fields on trapped inertial modes are not as great as previously thought.Comment: 16 pages, 6 figures, MNRAS accepte

Multiaxial analyzer detects low-energy electrons

Three curved plate energy analyzers coupled with three electron multiplier tubes detect and measure low energy electron flux in several directions simultaneously

Infrared upconversion for astronomical applications

The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given

SEPTEMBER 26, 1960 SOLAR COSMIC RAY EVENT

Solar cosmic ray event - september 26, 196