The structure of the solar plasma flow generated by solar flares.
Geomagnetic storms due to solar flares statistically analyzed to obtain configuration of solar plasma flow generated by solar flares
GEOMAGNETIC STORM↗
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The Three-Dimenstional Solar Wind at Solar Activity Minimum
In late 1997, the Ulysses spacecraft completed its first orbit around the Sun, observing the properties of the heliosphere at all latitudes between 80 degrees South and 80 degrees North. Because the mission occurred during a period of near-minimum solar activity, the configuration of the solar wind and interplanetary magnetic field were particularly simple, thus allowing confident comparisons between the properties of the polar corona observed by instruments of the Spartan and SOHO spacecraft and the resulting properties of the solar wind.
Solar Wind Ulysses Solar Activity polar corona↗
(abstract) Interplanetary Lyman-alpha Observations with the Galileo Ultraviolet Spectrometer: Solar Wind Latitude Variations and Multiple Scattering at Solar Maximum
The Galileo Ultraviolet Spectrometer obtained a Lyman-alpha celestrial sphere map on 13,14 December 1990 near the first Earth encounter, with spacecraft near the interstellar wind downwind axis. The data show solar flux longitudinal and latitudinal asymmetries which are modeled with He 10830 Ssolar images. The difference between the observed brightness and a single scattering model is attributed to multiple scattering effects, which we also calculate. The data constrain the solar wind flux latitude variation at solar maximum. Other 1990-1992 Galileo Lyman-alpha data will be discussed.
solar wind ultraviolet spectrometer solar flux cel↗
The FIELDS Instrument Suite for Solar Probe Plus Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients
NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.
Solar Probe Plus↗
A practical six-degree of freedom solar sail dynamics model for optimizing solar sail trajectories with torque constraints
Controlled flight of a solar sail-propelled spacecraft ('sailcraft') is a six-degree-of-freedom dynamics problem. Current state-of-the-art tools that simulate and optimize the trajectories flown by sailcraft do not treat the full kinetic (i.e. force and torque-constrained) motion, instead treating a discrete history of commanded sail attitudes, and either neglecting the sail attitude motion over an integration timestep, or treating the attitude evolution kinematically with a spline or similar treatment. The present paper discusses an aspect of developing a next generation sailcraf trajectory designing optimization tool JPL, for NASA's Solar Sail Spaceflight Simulation Software (SS). The aspect discussed in an experimental approach to modeling full six-degree-of-freedom kinetic motion of a solar sail in a trajectory propagator. Early results from implementing this approach in a new trajectory propagation tool are given.
six-degree-of-freedom↗
Alfven Waves and Turbulence in the Solar Atmosphere and Solar Wind
We solve the problem of propagation and dissipation of Alfvenic turbulence in a model solar atmosphere consisting of a static photosphere and chromosphere, transition region, and open corona and solar wind using a phenomenological model for the turbulent dissipation based on wave reflection. We show that most of the dissipation for a given wave frequency spectrum occurs in the lower corona, and the overall rms amplitude of the fluctuations evolves in a way consistent with observations. The frequency spectrum for a Kolmogorov-like slope is not found to change dramatically from the photosphere to the solar wind; however, it does preserve signatures of transmission throughout the lower atmospheric layers, namely, oscillations in the spectrum at high frequencies reminiscent of the resonances found in the linear case. These may disappear once more realistic couplings for the nonlinear terms are introduced or if time-dependent variability of the lower atmospheric layer is introduced.
turbulence↗
The Solar Umbrella: A Low-cost Demonstration of Scalable Space Based Solar Power
Within the past decade, the Space Solar Power (SSP) community has seen an influx of stakeholders willing to entertain the SSP prospect of potentially boundless, base-load solar energy. Interested parties affiliated with the Department of Defense (DoD), the private sector, and various international entities have all agreed that while the benefits of SSP are tremendous and potentially profitable, the risk associated with developing an efficient end to end SSP harvesting system is still very high. In an effort to reduce the implementation risk for future SSP architectures, this study proposes a system level design that is both low-cost and seeks to demonstrate the furthest transmission of wireless power to date. The overall concept is presented and each subsystem is explained in detail with best estimates of current implementable technologies. Basic cost models were constructed based on input from JPL subject matter experts and assume that the technology demonstration would be carried out by a federally funded entity. The main thrust of the architecture is to demonstrate that a usable amount of solar power can be safely and reliably transmitted from space to the Earth's surface; however, maximum power scalability limits and their cost implications are discussed.
climate change↗
Major Solar Eruptions and High-Energy Particle Events During Solar Cycle 24
We report on a study of all major solar eruptions that occurred on the frontside of the Sun during the rise to peak phase of cycle 24 (first 62 months) in order to understand the key factors affecting the occurrence of large solar energetic particle events (SEPs) and ground level enhancement (GLE) events. The eruptions involve major flares with soft X-ray peak flux greater than or equal to 5.0 x10(exp−5) Wm(exp−2) (i.e., flare size greater than or equal to M5.0) and accompanying coronal mass ejections (CMEs). The selection criterion was based on the fact that the only front-side GLE in cycle 24 (GLE 71) had a flare size of M5.1. Only approximately 37% of the major eruptions from the western hemisphere resulted in large SEP events. Almost the same number of large SEP events was produced in weaker eruptions (flare size less than M5.0), suggesting that the soft X-ray flare is not a good indicator of SEP or GLE events. On the other hand, the CME speed is a good indicator of SEP and GLE events because it is consistently high supporting the shock acceleration mechanism. We found the CME speed, magnetic connectivity to Earth (in longitude and latitude), and ambient conditions as the main factors that contribute to the lack of high-energy particle events during cycle 24. Several eruptions poorly connected to Earth (eastern-hemisphere or behind-the-west-limb events) resulted in very large SEP events detected by the Solar Terrestrial Relations Observatory (STEREO) spacecraft. Some very fast CMEs, likely to have accelerated particles to GeV energies, did not result in a GLE event because of poor latitudinal connectivity. The stringent latitudinal requirement suggests that the highest-energy particles are likely accelerated in the nose part of shocks, while the lower energy particles are accelerated at all parts. There were also well-connected fast CMEs, which did not seem to have accelerated high-energy particles due to possible unfavorable ambient conditions (high Alfven speed, overall reduction in acceleration efficiency in cycle 24).
Flares↗
Performance of NOAA-20 VIIRS Solar Diffuser and Solar Diffuser Stability Monitor
Visible Infrared Imaging Radiometer Suite (VIIRS) radiometrically calibrates its reflective solar bands (RSBs) primarily through a sunlit onboard solar diffuser (SD). The sunlit SD provides a known radiance under the condition that the absolute product of the SD screen transmittance and the bidirectional reflectance distribution function (BRDF) along the SD-to-telescope direction is accurately known. The BRDF changes due to solar exposure. The change, referred to as the H-factor, is monitored by the onboard SD stability monitor (SDSM). The accuracy of the retrieved H-factor propagates to the retrieved F-factor which corrects the scene spectral radiance. High accuracy of the retrieved H-factor relies on high accuracies in the SDSM screen relative effective transmittance and the relative product of the SD screen effective transmittance and the BRDF at the mission start, and a high SDSM detector signal-to-noise ratio (SNR). This article briefly reviews the algorithms used for the NOAA-20 (N20) VIIRS RSB on-orbit radiometric calibration. Additionally, we show the performance of the N20 VIIRS SDSM, giving the SDSM detector SNRs and the SDSM detector gain temporal changes. We develop a model for the SNRs. The model shows that the decreased SNRs in time are due to the detector gain decreases. We also show the N20 VIIRS SD on-orbit performance, measured by the retrieved H-factor and the estimated standard deviation of its error. The H-factor for the telescope view is obtained from the H-factor for the SDSM view, multiplied by an H-factor angular dependence term. We use an innovative method to determine the angular dependence, using the dependence obtained for the Suomi National Polar-orbiting Partnership (SNPP) VIIRS.
VIIRS↗
The NASA Solar Cruiser Solar Sail System – Ready for Heliophysics and Deep Space Missions
Mission Mature solar sail propulsion technology to enable near-term, compelling space missions for NASA and the nation. Mission Technology Goals Demonstrate solar sail propulsion technology to enable near- and midterm missions in cis-lunar space, sun-L1 halo orbits, non-Keplerian and other planetary orbits - Maneuver without regret capability in the Earth/Moon system - Space Domain Awareness - Increased Space Weather warning times - Sustained in-situ measurements within the Earth's magnetotail - High inclination solar orbital observations
Solar Sail↗
Morphology of the Solar Corona from Radio Occultation Measurements: Implications for Solar Probe
This paper summarizes the latest results on the morphology of the near-Sun solar wind obtained from radio occultation measurements, and their impact on the planning and conduct of a mission to the Sun such as Solar Probe.
solar corona radio occultation spacecraft radio me↗
Radiation scales on which standard values of the solar constant and solar spectral irradiance are based
The question of radiation scales is critically examined. There are two radiation scales which are of fundamental validity and there are several calibration standards and radiation scales which have been set up for practical convenience. The interrelation between these scales is investigated. It is shown that within the limits of accuracy of irradiance measurements in general and solar irradiance measurements in particular, the proposed standard values of the solar constant and solar spectrum should be considered to be on radiation scales of fundamental validity; those based on absolute electrical units and on the thermodynamic Kelvin temperature scale.
Thekaekara, M. P.↗
Revised standards for the solar constant and the solar spectrum
The values of the solar constant and solar spectrum are presented which are proposed as revised standards for science and technology. A solar constant value of 1.94 cal/sq cm min or 135.3 mW/sq cm was proposed. A detailed spectral irradiance table is given for the range of 0.12 to 1000 microns.
Thekaekara, M. P.↗
Solar flares and solar wind helium enrichments - July 1965-July 1967.
It has previously been suggested that the very high relative abundances of helium occasionally observed in the solar wind mark the plasma accelerated by major solar flares. To confirm this hypothesis, we have studied the 43 spectra with He/H greater than 15% that were observed among 10,300 spectra collected by Vela 3 between July 1965-July 1967. Six new flare-enhancement events are discussed in this paper. It is concluded that the association of helium enhancements with major flares is real, nonrandom, and very strong. With this study, there are 12 cases of reliable associations between helium enhancements and flares reported in the literature. The general characteristics of these events are discussed. It is found that the flares are typically large and bright (2B or 3B), often they produce cosmic ray protons, and they are widely distributed in solar longitude. A qualitative discussion of some of the possibilities for the source of helium enhanced plasma is presented. It is suggested that the helium enriched plasma may be the piston producing the shock causing the Type II radio emission.
Hirshberg, J.↗
Solar wind helium enhancements following major solar flares
The observations of solar wind helium enhancements following major solar flares are reviewed, and the hypothesis that helium enhancements often mark flare piston plasma is confirmed. Helium enhancements were observed during each of the three periods (March 1966, July 1966, August/September 1966) of major solar activity that occurred from October 1965 to October 1966. No enhancements were seen during the long quiet periods that occurred that year. At 1 AU, the helium-enhanced plasma pistons had slowed so that the velocity was 80 percent of the mean transit velocity, in general agreement with theoretical models of the propagation of flare disturbances. A qualitative model, in which the piston plasma is accelerated from the flare site deep in the corona, is discussed briefly. If the model is valid in general outline, the piston plasmas provide samples of material from the lower levels of the corona.
Hirshberg, J.↗
Variations of the relative abundances of He, (C,N,O) and Fe-group nuclei in solar cosmic rays and their relationship to solar particle acceleration
Measurements of the flux of helium nuclei in the 24 January 1971 event and of helium and (C,N,O) nuclei in the 1 September 1971 event are combined with previous measurements to obtain the relative abundances of helium, (C,N,O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C,N,O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C,N,O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.
Bertsch, D. L.↗
Effects of sudden mixing in the solar core on solar neutrinos and ice ages.
Some numerical experiments with a solar model have been conducted in connection with the hypothesis regarding the effects of mixing in the solar core. Questions concerning a plausible mechanism by which such a mixing could be produced are explored. The variation of solar luminosity throughout the numerical experiments is shown. In connection with a great change in luminosity after a second mixing, it is suggested that the earth is presently undergoing an ice age.
Ezer, D.↗
Measurements of heavy solar wind and higher energy solar particles during the Apollo 17 mission
The lunar surface cosmic ray experiment, consisting of sets of mica, glass, plastic, and metal foil detectors, was successfully deployed on the Apollo 17 mission. One set of detectors was exposed directly to sunlight and another set was placed in shade. Preliminary scanning of the mica detectors shows the expected registration of heavy solar wind ions in the sample exposed directly to the sun. The initial results indicate a depletion of very-heavy solar wind ions. The effect is probably not real but is caused by scanning inefficiencies. Despite the lack of any pronounced solar activity, energetic heavy particles with energies extending to 1 MeV/nucleon were observed. Equal track densities of approximately 6000 tracks/cm sq 0.5 microns in length were measured in mica samples exposed in both sunlight and shade.
Walker, R. M.↗