The Integrated Science Investigation of the Sun (ISIS) is a complete science investigation on the Solar Probe Plus (SPP) mission, which flies to within nine solar radii of the Sun’s surface. ISIS ...comprises a two-instrument suite to measure energetic particles over a very broad energy range, as well as coordinated management, science operations, data processing, and scientific analysis. Together, ISIS observations allow us to explore the mechanisms of energetic particles dynamics, including their: (1) Origins—defining the seed populations and physical conditions necessary for energetic particle acceleration; (2) Acceleration—determining the roles of shocks, reconnection, waves, and turbulence in accelerating energetic particles; and (3) Transport—revealing how energetic particles propagate from the corona out into the heliosphere. The two ISIS Energetic Particle Instruments measure lower (EPI-Lo) and higher (EPI-Hi) energy particles. EPI-Lo measures ions and ion composition from ∼20 keV/nucleon–15 MeV total energy and electrons from ∼25–1000 keV. EPI-Hi measures ions from ∼1–200 MeV/nucleon and electrons from ∼0.5–6 MeV. EPI-Lo comprises 80 tiny apertures with fields-of-view (FOVs) that sample over nearly a complete hemisphere, while EPI-Hi combines three telescopes that together provide five large-FOV apertures. ISIS observes continuously inside of 0.25 AU with a high data collection rate and burst data (EPI-Lo) coordinated with the rest of the SPP payload; outside of 0.25 AU, ISIS runs in low-rate science mode whenever feasible to capture as complete a record as possible of the solar energetic particle environment and provide calibration and continuity for measurements closer in to the Sun. The ISIS Science Operations Center plans and executes commanding, receives and analyzes all ISIS data, and coordinates science observations and analyses with the rest of the SPP science investigations. Together, ISIS’ unique observations on SPP will enable the discovery, untangling, and understanding of the important physical processes that govern energetic particles in the innermost regions of our heliosphere, for the first time. This paper summarizes the ISIS investigation at the time of the SPP mission Preliminary Design Review in January 2014.
Using observations from the
High Energy Telescopes
(HETs) on the STEREO A and B spacecraft and similar observations from near-Earth spacecraft, we summarize the properties of more than 200 individual ...> 25 MeV solar proton events, some detected by multiple spacecraft, that occurred from the beginning of the STEREO mission in October 2006 to December 2013, and provide a catalog of these events and their solar sources and associations. Longitudinal dependencies of the electron and proton peak intensities and delays to onset and peak intensity relative to the solar event have been examined for 25 three-spacecraft particle events. Expressed as Gaussians, peak intensities fall off with longitude with
σ
=47±14
∘
for 0.7 – 4 MeV electrons, and
σ
=43±13
∘
for 14 – 24 MeV protons. Several particle events are discussed in more detail, including one on 3 November 2011, in which ∼ 25 MeV protons filled the inner heliosphere within 90 minutes of the solar event, and another on 7 March 2012, in which we demonstrate that the first of two coronal mass ejections that erupted from an active region within ∼ 1 hour was associated with particle acceleration. Comparing the current Solar Cycle 24 with the previous cycle, the first > 25 MeV proton event was detected at Earth in the current solar cycle around one year after smoothed sunspot minimum, compared with a delay of only two months in Cycle 23. Otherwise, solar energetic particle event occurrence rates were reasonably similar during the rising phases of Cycles 23 and 24. However, the rate declined in 2013, reflecting the decline in sunspot number since the peak in the northern-hemisphere sunspot number in November 2011. Observations in late 2013 suggest that the rate may be rising again in association with an increase in the southern sunspot number.
Abstract On 2022 September 5, Parker Solar Probe (Parker) observed a large solar energetic particle (SEP) event at the unprecedented distance of only 15 R S from the Sun. The observations from the ...Integrated Science Investigation of the Sun (IS⊙IS) obtained over the course of this event are remarkably rich, and an overview is presented here. IS⊙IS is capable of measuring ions from 20 keV to over 100 MeV nuc −1 and electrons from 30 keV to 6 MeV; here, we primarily focus on the proton and helium measurements above 80 keV. Among the surprising results are evidence of inverse velocity dispersion at energies above 1 MeV during the onset of the event, a sharp decrease in the energetic particle intensities at all energies at the interplanetary shock crossing, and repeated short durations of highly anisotropic sunward flow. Many changes in the SEP intensities, anisotropy, and spectral steepness are coincident with solar wind structure boundaries identified using the Parker solar wind magnetic field and plasma data. However, there are significant changes that are not correlated with any clearly visible solar wind variation. The observations presented here serve as an introduction to a complex event with numerous opportunities for future, more in-depth studies.
We report abundances of elements from 26Fe to 34Se in the cosmic radiation measured during fifty days of exposure of the Trans-Iron Galactic Element Recorder (TIGER) balloon-borne instrument. These ...observations add support to the concept that the bulk of cosmic ray acceleration takes place in OB associations, and they further support cosmic ray acceleration models in which elements present in interstellar grains are accelerated preferentially compared with those found in interstellar gas.
We draw a comparison between a solar energetic particle event associated with the release of a slow coronal mass ejection close to the Sun, and the energetic particle population produced in high ...current density field-aligned current structures associated with auroral phenomena in planetary magnetospheres. We suggest that this process is common in CME development and lift off in the corona, and may account for the electron populations that generate Type III radio bursts, as well as for the prompt energetic ion and electron populations typically observed in interplanetary space.
Abstract High-energy neutral solar radiation in the form of γ -rays and neutrons is produced as secondary products in solar flares. The characteristics of this emission can provide key information ...regarding the energization of charged particles, particularly when primary particles remain trapped in the corona. The Integrated Science Investigation of the Sun (IS⊙IS) suite on Parker Solar Probe is composed of instruments primarily intended to measure energetic charged particles. However, the High Energy Telescope (HET) in IS⊙IS was also designed with a supplementary neutral mode intended to measure γ -rays and neutrons. HET observed its first clear solar γ -ray event in connection with a hard X-ray flare, the eruption of a coronal mass ejection, and a solar energetic particle event on 2022 September 5. The X-ray spectral shape was observed to harden over the course of the event, culminating with the observation of γ -rays by HET. A coincident enhancement in the lower-energy Energetic Particle Instrument (EPI-Lo) was also observed, likely produced by incident solar γ -rays despite the EPI-Lo instrument not having any special neutral measurement capabilities. We use Monte Carlo modeling to reconstruct the incident γ -ray spectrum based on the measured spectrum to demonstrate that the combination of IS⊙IS instruments can measure hard X-rays and γ -rays from ∼60 keV–7 MeV. Despite the fact that this is a supplemental science goal of the mission, the capability of the IS⊙IS instruments to measure γ -rays is important for the study of this population due to the very limited instruments currently observing the Sun in γ -rays.
The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space called the heliosphere. The recently ...launched Interstellar Boundary Explorer (IBEX) spacecraft has completed its first all-sky maps of the interstellar interaction at the edge of the heliosphere by imaging energetic neutral atoms (ENAs) emanating from this region. We found a bright ribbon of ENA emission, unpredicted by prior models or theories, that may be ordered by the local interstellar magnetic field interacting with the heliosphere. This ribbon is superposed on globally distributed flux variations ordered by both the solar wind structure and the direction of motion through the interstellar medium. Our results indicate that the external galactic environment strongly imprints the heliosphere.
Abstract
The Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer spacecraft has been operating successfully in a halo orbit about the L1 Lagrange point since late 1997. We ...report here the isotopic composition of the Galactic cosmic ray (GCR) elements with 29 ≤
Z
≤ 38 derived from more than 20 years of CRIS data. Using a model of cosmic-ray transport in the Galaxy and the solar system (SS), we have derived from these observations the isotopic composition of the accelerated material at the GCR source (GCRS). Comparison of the isotopic fractions of these elements in the GCRS with corresponding fractions in the solar system gives no indication of GCRS enrichment in
r
-process isotopes. Since a large fraction of core-collapse supernovae (CCSNe) occur in OB associations, the fact that GCRs do not contain enhanced abundances of
r
-process nuclides indicates that CCSNe are not the principal source of lighter (
Z
≤ 38)
r
-process nuclides in the solar system. This conclusion supports recent work that points to binary neutron-star mergers, rather than supernovae, as the principal source of galactic
r
-process isotopes.
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