Characteristics of the Termination Shock: Insights from Voyager

We examine the energy spectra obtained from the cosmic ray instrument on the Voyager 1 spacecraft during 2002/215 through 2005/60. We find that the energy spectra of protons below ~20 MeV often resemble two power laws with a relatively hard index at low energies and a softer index at higher energies. The point of intersection of the two power laws is ~3 MeV. Beginning in 2005, the low-energy index is typically –1.5, corresponding to a shock strength (compression ratio) of 2.5. We attribute these characteristics to a restricted region of the solar wind termination shock that is sporadically connected to the Voyager 1 spacecraft by the interplanetary magnetic field. The absence of significant spectral variability in 2005 suggests that Voyager 1 entered a region with minimal spatial gradients of the lowest energy ions

The anomalous cosmic-ray component

This brief report is intended to update the anomalous component section of the summary report of the galactic cosmic-ray working group (Mewaldt et al., 1987), which was drafted at the March 1987 Workshop on the Interplanetary Charged Particle Environment at the Jet Propulsion Laboratory. The description of the spectrum of the anomalous cosmic-ray component is contained in section 3.3 of that report. That description is based on data analyzed through day 310 of 1986, and in it we proposed that the energy spectrum of the various species of the anomalous component could be derived by scaling from two generic spectra. Two generic spectra were required because the energy spectrum of the anomalous component changed shape near the time of the solar magnetic field reversal in 1980. These two generic spectra are shown in Figure 2 of the summary report

Solar cycle variations of the anomalous cosmic ray component

The intensity of the anomalous cosmic ray component, consisting of He, N, O, and Ne, has long been known to be especially sensitive to the effects of solar modulation. Following its discovery in 1972, this component dominated the quiet time flux of cosmic ray nuclei below approx. 30 MeV/nucleon during the 1972 to 1978 solar minimum, but then became essentially unobservable at 1 AU with the approach of solar maximum conditions. One recent theoretical model predicts substantial differences in the intensity of the anomalous fluxes from one solar minimum period to the next because of the reversal of the solar magnetic field. Using data from the Caltech experiments on IMP-8 and ICE (ISEE-3), the intensity of anomalous O and He at 1 AU during the years 1972 to 1985 is reported in particular. Whether the anomalous fluxes will return to their 1972-1978 levels, as predicted by spherically symmetric modulation models, or whether they will fail to return to 1 AU, as suggested by modulation models in which gradient and curvature drifts dominate are to be determined. The preliminary analysis of data from 1984 shows that the intensity of 8 to 27 MeV/nucleon O is still more than an order of magnitude below its 1972 to 1978 levels, while the intensity of 25 to 43 MeV/nucleon He is a factor of Approx. 8 below its maximum level in 1977

Reduction and analysis of data from experiment CAI on the IMP-8 mission

The Caltech Electron/Isotope Spectrometer (EIS) on the Interplanetary Monitoring Platform 8 (IMP-8) has provided precise measurements of the energy spectra and time variations of low energy electrons (0.16 to 6 MeV), the isotopes of hydrogen and helium (approximately 2 to 40 MeV/nucleon), and the elements from lithium through oxygen (approximately 5 to 50 MeV/nucleon) in energetic particle fluxes of solar, galactic, interplanetary, and magnetospheric origin since 1973. The accomplishments that have resulted from EIS measurements during the period March 24, 1980 to December 31, 1984 are summarized

Deviation from Snell's Law for Beams Transmitted Near the Critical Angle: Application to Microcavity Lasers

We show that when a narrow beam is incident upon a dielectric interface near the critical angle for total internal reflection it will be transmitted into the far-field with an angular deflection from the direction predicted by Snell's Law, due to a phenomenon we call "Fresnel Filtering". This effect can be quite large for the parameter range relevant to dielectric microcavity lasers.Comment: 4 pages, 3 figures (eps), RevTeX 3.1, to be published in Optics Letter