Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Interplanetary particle acceleration”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

On the connection of interplanetary shock wave parameters and energetic storm particle events

A series of energetic storm particle (ESP) events is investigated on the basis of observations of energetic solar protons by IMPs IV and V between 1967 and 1972. The total number and energy of particles associated with 20 ESP events are analyzed in connection with several plasma parameters at the shock surface; i.e., magnetic and thermal pressure, magnetic field and plasma mass flux. Correlation is established between the total energy of ESPs in the energy range of 1-80 MeV and the jump in the total pressure. It is pointed out that the amount of shock energy converted to the acceleration of ESP particles is not negligible and could, in principle, contribute to the deceleration of the shock wave.

Gombosi, T.↗
NASA NTRS1992

Nonlinear magnetosonic waves and mirror mode structures in the March 1991 Ulysses interplanetary event

In examining the March 23-25, 1991 Ulysses (2.2 AU) high speed solar wind events, two distinct plasma wave modes are found: steepened magnetosonic waves with whistler precursors and mirror mode structures. These two modes are locally generated by plasma instabilities, presumably associated with anisotropies existing in the energetic shock particles and solar wind plasma, respectively. The magnetosonic waves are generated by a right-hand resonant instability associated with an about 40 keV ion beam. By an extrapolation of the results presented here, assuming microflares and nanoflares at the sun generate shocks in the lower corona and these shocks accelerate energetic ions, it is suggested that the ions, via the right-hand resonant instability, generate magnetosonic waves which steepened to form 'microshocks'. These shocks could, in turn, accelerate more energetic ions, leading to a shock/energetic ion/magnetosonic wave cascade. These newly formed magnetosonic waves and shocks presumably could propagate in a broad range of directions, leading to energy dissipation over a large region of the outer corona.

Tsurutani, Bruce T.↗
DOE OSTI2022

The heliospheric ambipolar potential inferred from sunward-propagating halo electrons

ABSTRACT We provide evidence that the sunward-propagating half of the solar wind electron halo distribution evolves without scattering in the inner heliosphere. We assume the particles conserve their total energy and magnetic moment, and perform a ‘Liouville mapping’ on electron pitch angle distributions measured by the Parker Solar Probe SPAN-E instrument. Namely, we show that the distributions are consistent with Liouville’s theorem if an appropriate interplanetary potential is chosen. This potential, an outcome of our fitting method, is compared against the radial profiles of proton bulk flow energy. We find that the inferred potential is responsible for nearly 100 per cent of the proton acceleration in the solar wind at heliocentric distances 0.18-0.79 AU. These observations combine to form a coherent physical picture: the same interplanetary potential accounts for the acceleration of the solar wind protons as well as the evolution of the electron halo. In this picture the halo is formed from a sunward-propagating population that originates somewhere in the outer heliosphere by a yet-unknown mechanism.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2001

Modeling Magnetospheric Sources

We have used global magnetohydrodynamic, simulations of the interaction between the solar wind and magnetosphere together with single particle trajectory calculations to investigate the sources of plasma entering the magnetosphere. In all of our calculations solar wind plasma primarily enters the magnetosphere when the field line on which it is convecting reconnects. When the interplanetary magnetic field has a northward component the reconnection is in the polar cusp region. In the simulations plasma in the low latitude boundary layer (LLBL) can be on either open or closed field lines. Open field lines occur when the high latitude reconnection occurs in only one cusp. In the MHD calculations the ionosphere does not contribute significantly to the LLBL for northward IMF. The particle trajectory calculations show that ions preferentially enter in the cusp region where they can be accelerated by non-adiabatic motion across the high latitude electric field. For southward IMF in the MHD simulations the plasma in the middle and inner magnetosphere comes from the inner (ionospheric) boundary of the simulation. Solar wind plasma on open field lines is confined to high latitudes and exits the tailward boundary of the simulation without reaching the plasma sheet. The LLBL is populated by both ionospheric and solar wind plasma. When the particle trajectories are included solar wind ions can enter the middle magnetosphere. We have used both the MHD simulations and the particle calculations to estimate source rates for the magnetosphere which are consistent with those inferred from observations.

Walker, Raymond J.↗
NASA NTRS1974

Relativistic electron events in interplanetary space

Review of relativistic electron events observed in interplanetary space. The different types of event are identified and illustrated. The relationships between solar X-ray and radio emissions and relativistic electrons are examined, and the relevance of the observations to solar flare acceleration models is discussed. A statistical analysis of electron spectra, the electron/proton ratio and propagation from the flare site to the earth is presented. A model is outlined which can account for the release of electrons from the sun in a manner consistent with observations of energetic solar particles and electromagnetic solar radiation.

Simnett, G. M.↗
NASA NTRS1986

Energetic proton and helium fluxes associated with interplanetary shocks and their relation to the solar wind composition

The He/H ratios in particle events associated with interplanetary travelling shocks are investigated. It is found that immediately after the arrival of the shock, the about 40 keV/nucl He/H flux ratio of energetic particles of equal velocity or equal energy per charge is correlated with the He/H density ratio in the solar wind. The ambient proton flux from the parent solar particle event appears to have a significant effect on the spectral shape of the shock-associated particle spectrum above 200 keV. These observations are consistent with a first-order Fermi acceleration of these particles in which the shock-heated solar wind is the principal contributor to the shock-associated particle population.

Tan, L. C.↗
NASA NTRS2003

Two Components in Major Solar Particle Events

A study has been made of 29 intense, solar particle events observed in the energy range 25-100 MeV/nuc near Earth in the years 1997 through 2001. It is found that the majority of the events (19/29) had Fe to O ratios which were reasonably constant with time and energy, and with values above coronal. These all originated on the Sun s western hemisphere and most had intensities that rose rapidly at the time of an associated flare, and coronal mass ejection (CME), and then decayed more gradually. Few interplanetary shocks were observed during these increases. The spectra were mainly power laws. The remaining 10 events had different intensity-time profiles and Fe to O ratios that varied with time and energy with values at or below coronal. Most of these originated near central meridian and 6 had strong interplanetary shocks that were observed near Earth. In general the spectra were not power laws but steepened at high energies, particularly for Fe. There were four events with two peaks in the intensity-time profiles, the first near the time of the associated flare and the other at shock passage. The results, considered in the light of other recent work, suggest that the high energy particles that occur shortly after flares are indeed flare particles. At the highest rigidities considered here shock-accelerated particles are uncommon and are observed only in association with unusually fast shocks.

White, Nicholas E.↗
NASA NTRS1982

Probing the solar wind acceleration region using spectroscopic techniques

Recent developments in the use of UV and EUV coronagraphic spectroscopy for studying the physical conditions in the solar corona in the solar wind acceleration region from a heliocentric distance of 1.8 solar radii out to 8 solar radii and beyond are reviewed. Particular attention is given to theoretical considerations and techniques for the estimation of particle ionization balances and velocity distributions, coronal temperatures, neutral hydrogen, proton, electron and ion temperatures and densities, outflow velocities, charge states and chemical abundances from spectral line radiation and white-light measurements. Observational considerations are discussed as they relate to requirements for stray light rejection and the effects of geocorona and interplanetary dust emission in coronagraph design. Results of coronal H I Lyman alpha and white light observations made during sounding rocket flights are summarized, and future observational programs making use of rocket-borne instruments, Detached Shuttle Payload Flights, Spacelab or space platforms are indicated.

Withbroe, G. L.↗
NASA NTRS1974

Lunar surface cosmic ray experiment

The galactic cosmic ray and solar flare experiment on Apollo 16 is reported. The published papers presented describe the experiment, equipment, data processing techniques, and operational history. The principle findings include: (1) The composition of heavy ions in interplanetary space at energies between approximately 30 and 130 MeV/nucleon is the same, within experimental errors. (2) The ability of a Lexan stack to determine simultaneously the energy spectra of major elements from He up to Fe in the energy interval 0.2 to 30 MeV/nucleon revealed systematic changes in the composition of solar flare particles as a function of energy. (3) Heavy ions emitted in a solar flare appear to be completely stripped of electrons, and are not in charge equilibrium at the time of acceleration and releases from the sun.

Price, P. B.↗
NASA NTRS1973

Mass motion in solar flares

Mass motions in solar flares are here considered in terms of a previously proposed model. Particle acceleration occurs during reconnection of a current sheet located at coronal heights. The downward component of the particle flux produces an impulsive hard X-ray burst and heats the upper layers of the chromosphere sufficiently to lead to explosive evaporation. Some of the evaporated gas remains trapped in newly closed magnetic field lines and is responsible for the soft thermal component of X-ray emission. Gas which flows along open magnetic field lines subsequently forms a plasmoid which is ejected by magnetic stresses into interplanetary space and may subsequently cause a geomagnetic storm. Analysis of a highly simplified model leads to formulas for the density, temperature, and other parameters of the flare-produced plasma in terms of a length scale and mean magnetic field strength for the flare.

Sturrock, P. A.↗
NASA NTRS1982

Energy dependence in solar cosmic ray composition

An investigation is conducted concerning an occurrence of effects related to energy dependence in studies of solar flare particle composition, taking into account eight large solar-flares associated particle events. The ratios C/O (carbon/oxygen), (MG plus Si)/O, and Fe(group)/O as a function of energy/nucleon are presented in a graph. A wide range of variation in the Fe(group)/O ratios is found from event to event. While the energy dependence is consistent in most events with individual element spectra, several events show unusual behavior in the Fe(group)/O ratio, due to the existence of several distinct spectral components. These multiple spectral components may imply multiple phases of acceleration or substantial interplanetary shock contamination at low energies at times well below the arrival time of these shocks at 1 AU.

Mcguire, R. E.↗
NASA NTRS2013

Comparison Between Path Lengths Traveled by Solar Electrons and Ions in Ground-Level Enhancement Events

We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of plus or minus 10% the deduced path length of low-energy (approximately 27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons.We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

electrons↗
NASA NTRS1982

Starprobe - The science opportunities

The scientific objectives of the NASA Starprobe mission for an unmanned spacecraft to pass within three solar radii of the sun's surface are reviewed. Fundamental observations of gravitation, relativity, and factors related to the solar interior, measurements of the static and dynamic electromagnetic fields and the particle populations close to the sun, and observations of the solar atmosphere from the photosphere to the corona with high spatial resolution would be possible with the Starprobe. A determination of the quadrupole coefficient in the expansion of the gravitational potential field of the sun is noted to be possible by measuring the departure from a Keplerian orbit of the Starprobe as it passes perihelion, yielding data on the rate of revolution of the interior of the sun. Further information on shock acceleration, energy losses, radio bursts, interplanetary propagation, and diffusion will be available at 10-60 solar radii.

Underwood, J. H.↗
NASA NTRS2005

Electron Beam Analysis of Micrometeoroids Captured in Aerogel as Stardust Analogues

In January 2004, NASA s Stardust spacecraft passed through the tail of Comet 81P/Wild-2. The on-board dust flux monitor instrument indicated that numerous micro- and nano-meter sized cometary dust particles were captured by the dedicated silica aerogel capture cell. The collected cometary particles will be returned to Earth in January 2006. Current Stardust analogues are: (i) Light-gas-gun accelerated individual mineral grains and carbonaceous meteoritic material in aerogels at the Stardust encounter velocity ca.approximately 6 kilometers per second. (ii) Aerogels exposed in low-Earth orbit (LEO) containing preserved cosmic dust grains. Studies of these impacts offer insight into the potential state of the captured cometary dust by Stardust and the suitability of various analytical techniques. A number of papers have discussed the application of sophisticated synchrotron analytical techniques to analyze Stardust particles. Yet much of the understanding gained on the composition and mineralogy of interplanetary dust particles (IDPs) has come from electron microscopy studies. Here we discuss the application of scanning electron microscopy (SEM) for Stardust during the preliminary phase of post-return investigations.

Graham, G. A.↗
DOE OSTI2020

Interplanetary Protons versus Interacting Protons in the 2017 September 10 Solar Eruptive Event

We analyze the relativistic proton emission from the Sun during the eruptive event on 2017 September 10, which caused a ground-level enhancement (GLE 72) registered by the worldwide network of neutron monitors. Using the neutron monitor data and interplanetary transport modeling both along and across interplanetary magnetic field (IMF) lines, we deduce parameters of the proton injection into the interplanetary medium. The inferred injection profile of the interplanetary protons is compared with the profile of the >100 MeV γ -ray emission observed by the Fermi Large Area Telescope, attributed to pion production from the interaction of >300 MeV protons at the Sun. GLE 72 started with a prompt component that arrived along the IMF lines. This was followed by a more prolonged enhancement caused by protons arriving at the Earth across the IMF lines from the southwest. The interplanetary proton event is modeled using two sources—one source at the root of the Earth-connected IMF line and another source situated near the solar western limb. The maximum phase of the second injection of interplanetary protons coincides with the maximum phase of the prolonged >100 MeV γ -ray emission that originated from a small area at the solar western limb, below the current sheet trailing the associated coronal mass ejection (CME). A possible common source of interacting protons and interplanetary protons is discussed in terms of proton acceleration at the CME bow shock versus coronal (re-)acceleration in the wake of the CME.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1974

Periodic escape of relativistic electrons from the Jovian magnetosphere

We adopt a model in which the Jovian magnetospheric tail is forced open by plasma that is accelerated out of the ionosphere by the centrifugal force of corotation. Any longitudinal asymmetry that exists in the ionospheric plasma source and/or the planetary magnetic field will cause a diurnal variation in the radial extent of the trapping region for energetic electrons. This diurnal variation in the extent of the particle trapping region can result in a time-dependent loss of relativistic electrons from the Jovian magnetosphere, modulated at the planetary rotation period. The diurnal trapping process may be relevant to the observation of electron pulses in interplanetary space during the Pioneer 10 approach to Jupiter.

Hill, T. W.↗
NASA NTRS1986

A test of Lee's quasi-linear theory of ion acceleration by interplanetary traveling shocks

Lee's (1983) quasi-linear theory of ion acceleration is tested using ISEE-3 measurements of the November 12, 1978 quasi-parallel interplanetary shock. His theory accounts with varying degrees of precision for the energetic proton spatial profiles; the dependence of the spectral index of the power law proton velocity distribution upon the shock compression ratio; the power law dependence of the upstream proton scalelength upon energy; the absolute magnitude of the upstream proton scale length; the behavior of the energetic proton anisotropy upstream and downstream of the shock; the behavior of the alpha-particle proton ratio upstream; the equality of the spatial scale lengths at the shock of the upstream waves and of the protons that resonate with them; and the dependence of the integrated wave energy density upon the proton energy density at the shock. However, the trace magnetic field frequency spectra disagree with his theory in two ways. The part of the spectrum that can resonate with the observed protons via first-order cyclotron resonance is flat, whereas Lee's theory predicts an f exp - 7/4 frequency dependence for the November 12 shock. Higher frequency waves, which could not resonate with the observed upstream protons, increased in amplitude as the shock approached, suggesting that they too were generated by the shock.

Kennel, C. F.↗
NASA NTRS2023

High-Energy (> 40 MeV) Proton Intensity Enhancements Associated with the Passage of Interplanetary Shocks at 1 au

We analyze periods with elevated >40 MeV proton intensities observed near Earth over a time span of 43 years (1973-2016) that coincide with the passage of interplanetary shocks. Typically, elevated proton intensities result from large solar energetic particle (SEP) events. The interplanetary shocks observed during these elevated-intensity periods may or may not be related to the origin of the SEP events. By choosing those cases when the shocks can be confidently associated with the solar eruption that generated the SEP event, we analyze the components of these SEP events that are localized in the vicinity of the shock (so-called “energetic storm particles (ESPs)"), focusing on those events where the ESP component exceeds 40 MeV. We examine the interdependence of these high-energy ESPs with (i) the properties of the solar eruptions that generated the shocks and the SEP events, and (ii) the parameters of the shocks at their arrival at 1 au. The solar eruptions at the origin of the shocks producing >40 MeV proton ESP intensity enhancements are within ±50° longitude of central meridian and are associated with fast coronal mass ejections (plane-of-sky speeds ≳1000 km s -1 ). The ESP events with the largest >40 MeV proton intensity increases tend to occur when there are structures such as intervening interplanetary coronal mass ejections and other unrelated shocks present in the solar wind through which the shock is propagating. Among the various local shock parameters considered, only the shock speed shows a certain degree of correlation with the observed ESP intensity increase.

Solar energetic particles↗