2,685 research outputs found
The isotopic composition of cosmic ray chlorine
The isotopic composition of galactic cosmic ray chlorine (approx. = 225 MeV/amu) has been studied using the high energy cosmic ray experiment on the International Sun Earth Explorer 3 (ISEE-3) spacecraft. The abundances of 35C1 and 37C1 are found to be consistent with the secondary production expected from a propagation model developed to account for both light and subiron secondaries. An upper limit on the abundance of the radioactive isotope 36C1 (halflife approx. = 0.3 Myr) is used to set a lower limit on the confinement time of cosmic rays of approximately 1 Myr
Multiple Scattering Effects in de/dx-E Instruments for Isotopic Composition Studies
The development of cosmic ray telescopes to separate individual isotopes of heavy elements using the dE/dx-vs.-E technique depends on the incorporation of precise trajectory sensing elements into these systems. In typical implementations the particle trajectory is derived from a set of position measurements made prior to a particle's entering the first energy loss detector. The use of the trajectory obtained in this way to correct energy loss signals for the actual pathlengths through the detectors depends on the assumption that the particle trajectory is a straight line. In order to resolve iron isotopes the angles of incidence, theta the particle track must be known rather accurately
Energy spectra of 3He-rich solar energetic particles associated with coronal waves
In addition to their anomalous abundances, 3He-rich solar energetic particles
(SEPs) show puzzling energy spectral shapes varying from rounded forms to power
laws where the later are characteristics of shock acceleration. Solar sources
of these particles have been often associated with jets and narrow CMEs, which
are the signatures of magnetic reconnection involving open field. Recent
reports on new associations with large-scale EUV waves bring new insights on
acceleration and transport of 3He-rich SEPs in the corona. We examined energy
spectra for 32 3He-rich SEP events observed by ACE at L1 near solar minimum in
2007-2010 and compared the spectral shapes with solar flare signatures obtained
from STEREO EUV images. We found the events with jets or brightenings tend to
be associated with rounded spectra and the events with coronal waves with power
laws. This suggests that coronal waves may be related to the unknown second
stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.Comment: Presented at 15th Annual International Astrophysics Conference "The
Science of Ed Stone". Accepted for publication in Journal of Physics:
Conference Serie
The Level of Solar Modulation of Galactic Cosmic Rays from 1997 to 2005 as Derived from ACE Measurements of Elemental Energy Spectra
Elemental and isotopic composition measurements of galactic cosmic rays
Measurements of the relative abundances of elements and their isotopes in galactic cosmic rays, which include both stable and long lived radioactive species, have led to a variety of insights into the nature of the cosmic ray source, the mechanisms involved in accelerating particles to high energies, and characteristics of their transport in the Galaxy. Some key developments that have contributed to the present understanding of cosmic rays are summarized
Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves
Small 3He-rich solar energetic particle (SEP) events have been commonly
associated with extreme-ultraviolet (EUV) jets and narrow coronal mass
ejections (CMEs) which are believed to be the signatures of magnetic
reconnection involving field lines open to interplanetary space. The elemental
and isotopic fractionation in these events are thought to be caused by
processes confined to the flare sites. In this study we identify 32 3He-rich
SEP events observed by the Advanced Composition Explorer near the Earth during
the solar minimum period 2007-2010 and examine their solar sources with the
high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images.
Leading the Earth, STEREO-A provided for the first time a direct view on
3He-rich flares, which are generally located on the Sun's western hemisphere.
Surprisingly, we find that about half of the 3He-rich SEP events in this survey
are associated with large-scale EUV coronal waves. An examination of the wave
front propagation, the source-flare distribution and the coronal magnetic field
connections suggests that the EUV waves may affect the injection of 3He-rich
SEPs into interplanetary space.Comment: accepted for publication in The Astrophysical Journa
Composition Measurements from ISEE-3: Fluorine through Calcium
Spacecraft measurements are reported of the elemental composition of galactic cosmic rays with 9 ≤ Z ≤ 5 ~20 at energies ~220 MeV /nucleon. In addition, for the elements with 16 ≤ Z ≤ 20 isotopic composition results are reported. The measured composition is found to be in generally good agreement with that expected from a propagated solar-like source
3He-Rich Solar Energetic Particles in Helical Jets on the Sun
Particle acceleration in stellar flares is ubiquitous in the Universe,
however, our Sun is the only astrophysical object where energetic particles and
their source flares can both be observed. The acceleration mechanism in solar
flares, tremendously enhancing (up to a factor of ten thousand) rare elements
like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we
present some of the most intense 3He- and Fe-rich solar energetic particle
events ever reported. The events were accompanied by non-relativistic electron
events and type III radio bursts. The corresponding high-resolution,
extreme-ultraviolet imaging observations have revealed for the first time a
helical structure in the source flare with a jet-like shape. The helical jets
originated in relatively small, compact active regions, located at the coronal
hole boundary. A mini-filament at the base of the jet appears to trigger these
events. The events were observed with the two Solar Terrestrial Relations
Observatories STEREO on the backside of the Sun, during the period of increased
solar activity in 2014. The helical jets may be a distinct feature of these
intense events that is related to the production of high 3He and Fe
enrichments.Comment: accepted for publication in The Astrophysical Journa
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