J. Sequeiros

PLASMA AND MAGNETIC FIELD INSIDE MAGNETIC CLOUDS: A GLOBAL STUDY

Data observed during spacecraft encounters with magnetic clouds have been extensively analyzed in the literature. Moreover, several models have been proposed for the magnetic topology of these events, and fitted to the observations. Although these interplanetary events present well-defined plasma features, none of those models have included a simultaneous analysis of magnetic field and plasma data. Using as a starting point a non-force-free model that we have developed previously, we present a global study of MCs that include both the magnetic field topology and the plasma pressure. In this paper we obtain the governing equations for both magnitudes inside a MC. The expressions deduced are fitted simultaneously to the measurements of plasma pressure and magnetic field vector. We perform an analysis of magnetic field and plasma WIND observations within several MCs from 1995 to 1998. The analysis is confined to four of these events that have high-quality data. Only in one fitting procedure we obtain the orientation of the magnetic cloud relative to the ecliptic plane and the current density of the plasma inside the cloud. We find that the equations proposed reproduce the experimental data quite well.

Detector system for low-energy cosmic ions study

Abstract A low-energy cosmic ion detector system composed of a telescope and its amplification electronics has been designed and constructed. The detector system is able to detect ions from hydrogen to iron in the energy range of 1–50 MeV/nucleon. The amplification electronics has been designed using space components so that its weight, dimensions and power consumption would be small enough to allow the telescope to be used for cosmic ion detection in space aboard a satellite. The system was calibrated in a heavy ion accelerator, and the results show good charge and mass discrimination for the registered ions as well as a good response from the amplification electronics.

Charge systematic errors associated with identification methods for heavy-ion ΔE–E telescopes

Abstract The contribution of identification methods to charge systematic errors for heavy-ion Δ E – E multidetector telescopes is studied. In this context, a new identification method is presented in two versions: the first uses one Δ E value and second uses all Δ E data for each event. A Monte Carlo simulation of the response of a solid-state telescope to an isotropic flux of heavy ions is used to test the systematic errors induced by this method and by the Seamster and range methods.

Parametrization of charge and mass resolution for ΔE − E telescopes

Abstract A simple parametrization of energy straggling of 2–200 MeV/nucleon heavy ions traversing thick silicon detectors, based on the Tschalar-Payne theory, is presented. With this parametrization, analytical expressions for the charge and mass resolution of energetic ions detected on ΔE − E telescopes can be obtained. Several consequences that can be extracted from these expressions are analysed, especially, in what concerns the thickness selection for multi-detector telescopes. The validity of those analytical formulae are tested with experimental resolutions obtained from calibration data of three different cosmic-ray telescopes.

Evidence of Magnetic Flux Ropes in the Solar Wind From Sigmoidal and non-Sigmoidal Active Regions

We have examined WIND magnetic field and plasma data during the first half of 1998 in order to find encounters of this spacecraft with magnetic clouds. From the events obtained through this search, we have selected four of them taking into account their solar origin. The four magnetic clouds are related to halo or partial halo CMEs, but the morphology of the active region before the eruption is sigmoidal for three of them and non-sigmoidal for the other one. We have analyzed these events in the solar wind by fitting the experimental data to a non-force-free flux-rope model. We conclude that both kinds of active regions develop in the solar wind an ejection with a flux-rope topology.

Low‐energy (<1.6 MeV) particle counting rates and solar magnetic activity: A study of the 1980 anomaly

We present a study of the relation between the solar magnetic activity (centered in sunspots, flares types N and B, and long-duration X class flares) and the counting rates of particles in interplanetary space with energies below 1.6 MeV obtained from the Low-Energy Proton Experiment (DFH-EPAS) onboard International Sun-Earth Explorer spacecraft, during the period 1978–1982. Our study shows that the particle counting rates are neither correlated with sunspots number nor with flares type N, but they are correlated with flares type B and mainly with long-duration X class flares. The origin of the low counting rates of particles detected during the years 1979–1980 is investigated as well. The disappearance of the strongest interplanetary shocks during that period can explain this phenomenon, at least within the energy range studied. The absence of any anomalous behavior in the flares type B and in the long-duration X class flares during this period suggests that this shock behavior can be produced by anomalous conditions of the interplanetary magnetic field during the Suns polar magnetic field reversal.

HP-NIM data acquisition system

Abstract A Hewlett Packard desktop computer has been connected through a Data Ready Flag with NIM ADCs to produce a data acquisition system which can be used for cosmic ray telescope detector applications. The system has been tested with a two detector telescope irradiated with beams of 20 Ne ions accelerated to 230 and 376 MeV.