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NASA NTRS1980

Energetic particles in solar flares

The various manifestations of energetic particles in solar flares are examined, and possible mechanisms for the acceleration of these particles are considered. Hard X-ray observations and possible mechanisms for the production of the dominant form of solar energetic particles, electrons with energies between 10 and 100 keV, are discussed, with consideration of thin-target models, thick-target models and thick-target models with reverse currents, and first-phase acceleration mechanisms for energetic electrons emitting impulsive microwave and fast-drift Type III radio bursts as well as impulsive hard X rays, which are detected themselves 20 min after the flare at 1 AU are considered. Radio evidence on the number, energy and pitch-angle distributions of energetic particles produced during solar flares is summarized, and observations at 1 AU of proton and electron energy spectra, the proton/electron ratio and energetic particle events rich in He-3 from solar flares are discussed. Finally, consideration is given to gamma-ray evidence of nuclear reactions in flares and white-light flares

Ramaty, R.↗

NASA NTRS1992

Characterization of radiation-induced damage in high performance polymers by electron paramagnetic resonance imaging spectroscopy

The potential for long-term human activity beyond the Earth's protective magnetosphere is limited in part by the lack of detailed information on the effectiveness and performance of existing structural materials to shield the crew and spacecraft from highly penetrating space radiations. The two radiations of greatest concern are high energy protons emitted during solar flares and galactic cosmic rays which are energetic ions ranging from protons to highly oxidized iron. Although the interactions of such high-energy radiations with matter are not completely understood at this time, the effects of the incident radiation are clearly expected to include the formation of paramagnetic spin centers via ionization and bond-scission reactions in the molecular matrices of structural materials. Since this type of radiation damage is readily characterized by Electron Paramagnetic Resonance (EPR) spectroscopy, the NASA Langley Research Center EPR system was repaired and brought on-line during the 1991 ASEE term. A major goal of the 1992 ASEE term was to adapt the existing core of the LaRC EPR system to meet the requirements for EPR Imaging--a powerful new technique which provides detailed information on the internal structure of materials by mapping the spatial distribution of unpaired spin density in bulk media. Major impetus for this adaptation arises from the fact that information derived from EPRI complements other methods such as scanning electron microscopy which primarily characterize surface phenomena. The modification of the EPR system has been initiated by the construction of specially designed, counterwound Helmholtz coils which will be mounted on the main EPR electromagnet. The specifications of the coils have been set to achieve a static linear magnetic field gradient of 10 gauss/mm/amp along the principal (Z) axis of the Zeeman field. Construction is also in progress of a paramagnetic standard in which the spin distribution is known in all three dimensions. This sample will be used to assess the linearity of the magnetic field gradient and to ensure authentic image reconstruction. A second major task was to secure the computer capability to enable image reconstruction from projection data generated by the magnetic field gradients. To this end, commercially available and public domain software packages which perform inverse Fourier Transform and convoluted (filtered) back projection functions are being integrated into the existing EPR data processing system.

Suleman, Naushadalli K.↗

NASA NTRS1997

Solar Cycle Variation in the Inner Zone Proton Belt Configuration

This paper presents a novel method of demonstrating atmospheric scale-height effects on energetic trapped protons. We have been using 2-D cross correlations as a powerful method of assessing the role of the trapped energetic protons in producing various effects in low altitude satellite systems. The method has permitted us to directly measure the drift of the particle South Atlantic Anomaly (due to the secular variation in the geomagnetic field) as a function of altitude and proton energy and to estimate the energy of the particles causing those effects. We have also been able to address minor artifacts in the AP82 model, itself. In this paper, we show that the technique is sufficiently powerful to address the variation in the inner zone energetic proton environment which occurs as a function of the solar cycle.

Vampola, A. L.↗

NASA NTRS2024

Deployed Electromagnetic Radiation Deflector Shield Creating a Zone of Minimum Radiation and Magnetic/Plasma Effects for Spacecraft

Spaceflight outside of the Earth's protective magnetic field is dangerous from a cosmic radiation perspective. Inside Earth's magnetic field, where the manned International Space Station (ISS) orbits, the radiation encountered is minimal and almost all is deflected by our planet's magnetic fields. However, outside that protective shield, the Sun's solar wind (high energy radiation, solar energetic particles or SEPs) consisting of protons, electrons, alpha particles and plasmas continuously bombards the spacecraft for the months or years of spaceflight. On occasion the Sun produces a CME (Coronal Mass Ejection) that vastly increases the energy and volume of this radiation. These particles damage human DNA as well as living tissue and can destroy sensitive electronics. The Deployed Electromagnetic Radiation Deflector Shield (DERDS) provides a magnetic field that will deflect SEPs and CMEs and other harmful solar and cosmic rays away from a manned spacecraft, robotic spacecraft, or manned extra-planetary base stations using an electromagnet that is deployed between the spacecraft/station and the source of radiation and creates a magnetosphere or zone of minimal radiation in which the spacecraft or base station would reside.

Patent↗

NASA NTRS2022

A Compact Electron-Proton Spectrometer for Moon / Mars Surface Space Weather Monitoring and Crew Protection (CEPS)

Small mass/low-power sensors are needed for autonomous Moon/Mars surface ops that provide alerts to impending adverse space weather conditions. In order to use current operational forecasting tools, a sensor capable of measuring both high-energy electrons and protons is needed. By combining high-TRL Timepix technology with a CdTe layer, this project leverages known technology to fill a critical gap for surface operations. Typical space weather sensors are at least an order of magnitude higher in mass than is expected from Timepix-based devices and are deployed on robotic assets away from human crews. High fidelity measurements at the crew location and subsequent ability are needed to provide warnings to crews to shelter with a device that can easily be carried on the Lunar and Martian surfaces. The aim of this project is the development of compact, low power space weather sensors for crew protection based on the combination of AES flight heritage Timepix hardware with novel CdTe (Cadmium Telluride) sensors. CdTe technology has only recently matured to a point where it can be reliably used with Timepix detectors. These detectors will be able to measure electron spectra in an energy range relevant to the RELEASE model, which is used operationally by NASA to provide crew early warning of Solar Energetic Particle Events as well as protons in the energy ranges relevant to human health allowing for event ‘nowcasting’ and total event crew dose prediction. Compared to existing solutions these detectors will be compact enough to travel with crew, providing a significant advantage to space environment situation awareness. Project results indicate that CdTe-based Timepix sensors respond well to energetic electrons, and particle tracks are sufficiently distinct to be able to measure in a mixed radiation field. Thermal testing results point to a needed design modification to mitigate high temperatures the detector will see in space. Radiation susceptibility testing was conducted to assess the radiation hardness of the CdTe-Timepix assembly. Overall, the assembly continued to operate up to 100 kRad of gamma-ray exposure. The system calibration did show drift over time but recovered once exposure was complete.

Dan James Fry↗

NASA NTRS2023

CEPS – A Compact Electron-Proton Spectrometer

Small mass/low-power sensors are needed for autonomous Moon/Mars surface ops that provide alerts to impending adverse space weather conditions. In order to use current operational forecasting tools, a sensor capable of measuring both high-energy electrons and protons is needed. By combining high-TRL Timepix technology with a CdTe layer, this project leverages known technology to fill a critical gap for surface operations. Typical space weather sensors are at least an order of magnitude higher in mass than is expected from Timepix-based devices and are deployed on robotic assets away from human crews. High fidelity measurements at the crew location and subsequent ability are needed to provide warnings to crews to shelter with a device that can easily be carried on the Lunar and Martian surfaces. The aim of this project is the development of compact, low power space weather sensors for crew protection based on the combination of AES flight heritage Timepix hardware with novel CdTe (Cadmium Telluride) sensors. CdTe technology has only recently matured to a point where it can be reliably used with Timepix detectors. These detectors will be able to measure electron spectra in an energy range relevant to the RELEASE model, which is used operationally by NASA to provide crew early warning of Solar Energetic Particle Events as well as protons in the energy ranges relevant to human health allowing for event ‘nowcasting’ and total event crew dose prediction. Compared to existing solutions these detectors will be compact enough to travel with crew, providing a significant advantage to space environment situation awareness. Project results indicate that CdTe-based Timepix sensors respond well to energetic electrons, and particle tracks are sufficiently distinct to be able to measure in a mixed radiation field. Detector response functions were developed for both electrons and protons. Measurement results showed response to both electrons and protons in the energy range of interest for human space flight.

Radiation↗

NASA NTRS1972

Mariner Venus-Mercury 1973 mission solar proton environment: fluence and dose

A derivation is presented for proton fluence over the duration of the Mariner Venus-Mercury 1973 (MVM73) mission in terms of a relatively constant, low energy component, the solar wind, and a probabilistic high energy component from discrete solar events. An updated correlation of yearly energetic proton fluence with yearly average sunspot number is presented. This correlation and sunspot cycle forecasts for the period of the MVM73 mission (late 1973 through early 1975) form the basis for the high energy proton fluence estimates with various confidence levels. Uncertainties in the probability estimates and in calculation of the scaling with distance from the Sun are discussed. Selection of a particular 95-percentile model as the design constraint is recommended, and reasons are presented for not using the worst-case model. Interior fluences were calculated and expressed in terms useful for spacecraft design.

Thomas, J. R.↗

NASA NTRS1987

Evidence in meteorites for an active early sun

High-sensitivity noble gas mass-spectrometric analyses of meteorite grains having solar flare heavy ion tracks show large enrichments of spallation-produced Ne-21 and Ar-38 when compared to nonirradiated grains from the same meteorite. The enhanced spallation effects in the irradiated grains are due to irradiation by energetic protons early in the history of the solar system, before compaction of the host meteorite. They require a proton fluence (E greater than 10 MeV) of 10 to the 16th to 10 to the 18th/cu cm. These results are best explained by solar flare irradiation in the early solar system with a proton flux several orders of magnitude higher than contemporary solar flares. The Ne isotopic structure suggests a harder energy spectrum than is characteristic of contemporary flares. These observations provide direct evidence for an active early (T Tauri) sun.

Caffee, M. W.↗

NASA NTRS1983

Characteristics of gamma-ray line flares

Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

Bai, T.↗

NASA NTRS1985

The propagation of solar flare particles in a turbulent coronal loop

Energetic solar flare particles, both electrons and protons, must survive the turbulent environment of a flaring loop and propogate to the lower corona or chromosphere in order to produce hard X-ray and gamma ray bursts. This plasma turbulence, often observed in soft X-ray line widths to be in excess of 100 km/s, is presumably capable of efficiently scattering the fast flare particles. This prevents to some degree the free streaming of accelerated particles and depending on the amplitude of the turbulence, restricts the particles to diffusive propagation along the length of the loop to the target chromosphere. In addition this turbulence is capable of performing additional acceleration of the fast particles by the second order Fermi mechanism. For compact flares with rise times 10s, the acceleration effect is small and the propagation of the particles is governed by spatial diffusion and energy loss in the ambient medium. The solution of the time dependent diffusion equation with velocity dependent diffusion and energy loss coefficients yields for the case of nonrelativistic protons particle precipitation rates which are necessary for calculating thick target gamma ray emission and also yields the total thin target emissivity.

Ryan, J. M.↗

NASA NTRS1983

Energetic solar cosmic rays in the outer heliosphere

Intermediate-energy protons (3.5-56 MeV) in the outer heliosphere are studied using data from the GSFC-UNH cosmic-ray telescopes on Pioneer 10 and 11. Flux and anisotropy information in this energy region is used to investigate the properties of the solar-flare-associated flux increases detected between September 1977 and September 1982 for radial distances between 5.8 and 28.5 AU. A propagation model is discussed, and its predictions for the 3-5 MeV protons are presented in diagrams.

Goeman, R.↗

NASA NTRS1985

Characteristics of gamma-ray line flares

Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays, (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

Bai, T.↗

NASA NTRS2000

Natural Hazards of the Space Environment

Spacecraft in Low Earth Orbit (LEO) are subject to numerous environmental hazards. Here I'll briefly discuss three environment factors that pose acute threats to the survival of spacecraft systems and crew: atmospheric drag, impacts by meteoroids and orbital debris, and ionizing radiation. Atmospheric drag continuously opposes the orbital motion of a satellite, causing the orbit to decay. This decay will lead to reentry if not countered by reboost maneuvers. Orbital debris is a by-product of man's activities in space, and consists of objects ranging in size from miniscule paint chips to spent rocket stages and dead satellites. Ionizing radiation experienced in LEO has several components: geomagnetically trapped protons and electrons (Van Allen belts); energetic solar particles; galactic cosmic rays; and albedo neutrons. These particles can have several types of prompt harmful effects on equipment and crew, from single-event upsets, latchup, and burnout of electronics, to lethal doses to crew.All three types of prompt threat show some dependence on the solar activity cycle. Atmospheric drag mitigation and large debris avoidance require propulsive maneuvers. M/OD and ionizing radiation require some form of shielding for crew and sensitive equipment. Limiting exposure time is a mitigation technique for ionizing radiation and meteor streams.

Evans, Steven W.↗

NASA NTRS2006

Use of FlUKA in the Analysis of the Mars Odyssey MARIE Experiment

UH researchers have significantly improved the calibration of the MARIE by simulating its response to energetic protons using FLUKA. Analysis of MARIE data shows that the intensity of solar energetic particles depends strongly on how well the observation point is connected magnetically to the site at which the particles are accelerated.

Pinsky, Lawrence S.↗

NASA NTRS2014

New Aspects of a Lid-Removal Mechanism in the Onset of a SEP-Producing Eruption Sequence

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from SDO/HMI and SDO/AIA, and EUV images from STEREO. Cheng et al. (2013) showed that the first eruption's ("Eruption 1'') flux rope was apparent only in "hotter'' AIA channels, and that it removed overlying field that allowed the second eruption (``Eruption 2'') to begin via ideal MHD instability; here we say Eruption 2 began via a ``lid removal'' mechanism. We show that during Eruption-1's onset, its flux rope underwent ``tether weakening'' (TW) reconnection with the field of an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption-2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption-1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption-2's flare loops (GOES thermal temperatures of approx. 9 MK compared to approx. 14 MK). This eruption sequence produced a strong solar energetic particle (SEP) event (10 MeV protons, >10(exp 3) pfu for 43 hrs), apparently starting when Eruption-2's CME blasted through Eruption-1's CME at 5-10 R_s. This occurred because the two CMEs originated in close proximity and in close time sequence: Eruption-1's fast rise started soon after the TW reconnection; the lid removal by Eruption-1's ejection triggered the slow onset of Eruption 2; and Eruption-2's CME, which started approx. 1 hr later, was three times faster than Eruption-1's CME.

Sterling, Alphonse C.↗

NASA NTRS2019

Space Radiation and Plasma Effects on Satellites and Aviation: Quantities and Metrics for Tracking Performance of Space Weather Environment Models

The Community Coordinated Modeling Center has been leading communitywide space science and space weather model validation projects for many years. These efforts have been broadened and extended via the newly launched International Forum for Space Weather Modeling Capabilities Assessment (https://ccmc.gsfc.nasa.gov/assessment/). Its objective is to track space weather models' progress and performance over time, a capability that is critically needed in space weather operations and different user communities in general. The Space Radiation and Plasma Effects Working Team of the afore mentioned International Forum works on one of the many focused evaluation topics and deals with five different subtopics (https://ccmc.gsfc.nasa.gov/assessment/topics/radiationall.php) and varieties of particle populations: Surface Charging from tens of eV to 50keV electrons and internal charging due to energetic electrons from hundreds keV to several MeVs. Single event effects from solar energetic particles and galactic cosmic rays (several MeV to TeV), total dose due to accumulation of doses from electrons (>100 keV) and protons (>1 MeV) in a broad energy range, and radiation effects from solar energetic particles and galactic cosmic rays at aviation altitudes. A unique aspect of the Space Radiation and Plasma Effects focus area is that it bridges the space environments, engineering, and user communities. The intent of the paper is to provide an overview of the current status and to suggest a guide for how to best validate space environment models for operational/engineering use, which includes selection of essential space environment and effect quantities and appropriate metrics.

Zheng, Yihua↗

NASA NTRS2009

STEREO Observations of Energetic Neutral Hydrogen Atoms during the 5 December 2006 Solar Flare

We report the discovery of energetic neutral hydrogen atoms emitted during the X9 solar event of December 5, 2006. Beginning ~1 hour following the onset of this E79 flare, the Low Energy Telescopes (LETs) on both the STEREO A and B spacecraft observed a sudden burst of 1.6 to 15 MeV protons beginning hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within 10 of the Sun, consistent with the measurement resolution. The derived emission profile at the Sun had onset and peak times remarkably similar to the GOES soft X-ray profile and continued for more than an hour. The observed arrival directions and energy spectrum argue strongly that the particle events less than 5 MeV were due to energetic neutral hydrogen atoms (ENAs). To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. Possible origins for the production of ENAs in a large solar event are considered. We conclude that the observed ENAs were most likely produced in the high corona and that charge-transfer reactions between accelerated protons and partially-stripped coronal ions are an important source of ENAs in solar events.

Mewaldt, R. A.↗

NASA NTRS1986

Shock acceleration of electrons and ions in solar flares

The simultaneous first-order Fermi shock acceleration of electrons, protons, and alpha particles are compared to observations of solar energetic particle events. For each event, a unique shock compression ratio in the range approx. 1.6 to 3 produces spectra in good agreement with observation. The range in compression ratios predicts that the more than 5 orders of magnitude spread in electron to proton intensity ratios observed at MeV energies is compressed to about 3 orders of magnitude at an assumed injection energy of 100 keV. The remaining spread can be accounted for with a modest range of injection conditions. The model predicts that the acceleration time to a given energy will be approximately equal for electrons and protons and, for reasonable solar parameters, can be on the order of 1 second to approx. 100 MeV.

Ellison, Donald C.↗