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At least 361 records · Page 20
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NASA NTRSDate not supplied

Development of Solar Flare and Energetic Particle Prediction Portal (SEP 3 )

Solar activity is a primary factor determining the state of the Earth’s space environment, geomagnetic and ionospheric disturbances, and radiation hazards. In the current state of knowledge, machine learning (ML) methods provide essential tools for processing data, investigating relationships among various physical properties and characteristics, uncovering hidden connections, and predicting hazardous solar events. The primary difficulty in developing and applying modern machine-learning tools in heliophysics is that the essential data are scattered among over a hundred data repositories developed by instrument teams of space missions and ground-based observatories. In addition, statistical and ML methods require long time series of homogeneous measurements. To facilitate ML-ready data preparation and access, we have developed an interactive database of solar flares integrating the most essential datasets (https://solarflare.njit.edu/). The database performs an initial data processing and is automatically updated. In addition, we are developing the Solar Energetic Particle Prediction Portal (SEP3, https://sun.njit.edu/SEP3), which hosts web applications that allow users to retrieve the database records. The Portal has a search page for browsing the events from the most widely used catalogs and a dedicated space to share the most recent achievements of the team. The interactive widget can display soft X-ray and proton flux time series from GOES satellites and the flare records. The data portal has been used to evaluate the forecasts of solar proton events and investigate machine-learning approaches to SEP prediction.

SMD↗
NASA NTRS1986

Solar filament eruptions and energetic particle events

The 1981 December 5 solar filament eruption that is associated with an energetic (E greater than 50 MeV) particle event observed at 1 AU. The eruption was photographed in H-alpha and was observed by the Solwind whitelight coronagraph on P78-1. It occurred well away from any solar active region and was not associated with an impulsive microwave burst, indicating that magnetic complexity and a detectable impulsive phase are not required for the production of a solar energetic particle (SEP) event. No metric type II or IV emission was observed, but an associated interplanetary type II burst was detected by the low-frequency radio experiment on ISEE 3. The December 5 and two other SEP events lacking evidence for low coronal shocks had unusually steep energy spectra (gamma greater than 3.5). In terms of shock acceleration, this suggests that shocks formed relatively high in the corona may produce steeper energy spectra than those formed at lower altitudes. It is noted that the filament itself maybe one source of the ions accelerated to high energies, since it is the only plausible coronal source of the He(+) ions observed in SEP events.

Kahler, S. W.↗
NASA NTRS1981

Relationship between energetic particles and plasmas in the distant plasma sheet

Measurements of ions from three different instruments on the IMP-7 and 8 spacecraft are combined to yield the differential energy spectra of ions over the entire energy range of 100 eV to 4 MeV in the earth's distant (30 to 40 earth radii) plasma sheet. These spectra, obtained during times of relatively small bulk flow velocities, span the intensity range from 10 to the -5th to 10 to the 5th per sq cm-sec-sr-keV, varying smoothly over the entire energy range both when the plasma is cold (about 1 keV) and hot (about 9 keV). Overall, the shape of the spectrum resembles a Maxwellian but with a high energy (not less than 50 keV) tail described well by a power law. The high energy tail is displaced in a parallel fashion to higher or lower intensities when the plasma is hot or cold, respectively. It is found that the energetic particle populations in the plasma sheet appear to be directly related to the mean thermal energies of the corresponding plasmas.

Sarris, E. T.↗
NASA NTRS1999

GEOTAIL and POLAR Observations of Auroral Kilometric Radiation and Terrestrial Low Frequency Bursts and their Relationship to Energetic Particles, Auroras, and Other Substorm Phenomena

Terrestrial low frequency (LF) bursts are plasma wave phenomena that appear to be a part of the low frequency end of the auroral kilometric radiation (AKR) spectrum and are observed during strong substorms, GEOTAIL and POLAR plasma wave observations from within the magnetosphere show that the AKR increases in intensity and its lower frequency limits decrease when LF bursts are observed. The first is expected as it is shows substorm onset and the latter indicates that the AKR source region is expanding to higher altitudes. Images from the POLAR VIS Earth Camera operating in the far-UV range and the POLAR UVI experiment usually feature an auroral brightening and an expansion of the aurora to higher latitudes at the time of the LF bursts. Enhanced fluxes of X-rays from precipitating electrons have also been observed by POLAR PIXIE. High resolution ground Abstract: magnetometer data from the CANOPUS and IMAGE networks show that the LF bursts occur when the expansive phase onset signatures are most intense. The ground magnetometer data and the CANOPUS meridian scanning photometer data sometimes show that during the LF burst events the expansive phase onset starts at unusually low latitudes and moves poleward. Large injections of energetic protons and electrons have also been detected by the GOES and LANL geosynchronous satellites during LF burst events. While most of the auroral brightenings and energetic particle injections associated with the LF bursts occur near local midnight, several have been observed as early as mid-afternoon. From these various measurements, we are achieving a better understanding of the plasma and particle motions during substorms that are associated with the generation and propagation of terrestrial LF bursts

Anderson, R . R.↗
NASA NTRS1973

Cyclotron resonance wave amplification in the magnetosphere and energetic particle stability

Detailed electron distribution measurements in the outer magnetosphere now available indicate that the energetic electron anisotropy may be very energy dependent, there being positive anisotropies near the magnetic equator for low-energy particles and negative anisotropies in this region for high-energy particles. Previous wave growth calculations assuming the energetic particle anisotropy to be independent of energy are inaccurate at high energies. The net one-hop whistler mode wave amplification is calculated as a function of frequency for a measured electron distribution at L = 7 for a number of assumed equatorial plasma densities. It is found that an increase in cold plasma density results in a change from a net wave damping to significant wave amplification.

Lucas, C.↗
NASA NTRS2002

Regimes of Pulsar Pair Formation and Particle Energetics

We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that,, while only the younger pulsars can produce pairs through CR, nearly all known radio pulsars are capable of producing pairs through non-resonant inverse-Compton scatterings. The effect of the neutron star equations of state on the pair death lines is explored. We show that pair production is facilitated in more compact stars and more a massive stars. Therefore accretion of mass by pulsars in binary systems may allow pair production in most of the millisecond purser population. We also find that two-photon pair production may be important in millisecond pursers if their surface temperatures are above approx. or equal to three million degrees K. Pursers that produce pairs through CRT wilt have their primary acceleration limited by the effect of screening of the electric field. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sup 1/2, sub rot) dependence. The acceleration voltage drop in pursers that produce pairs only through inverse-Compton emission will not be limited by electric field screening. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sub rot) dependence. Thus, older pursers will have significantly lower gamma-ray luminosity.

Harding, Alice K.↗
NASA NTRS1974

Drifting energetic particle bunches observed on ATS 5

Energetic protons and electrons introduced into the vicinity of the synchronous orbit by geomagnetic substorms and observed on ATS 5 at various local times have been analyzed for velocity dispersion effects associated with their longitudinal drift. Particles with energies between about 30 and 200 keV are shown to be produced simultaneously within tens of minutes at local times between about 0000 and 0400 near 6.6 earth radii during substorm activity. Those with energies not less than approximately 75 keV move in longitude in the direction and with the magnitude expected from gradient B drifts. Lower-energy protons and electrons appear at the satellite sooner than expected from their gradient B drifts, as though the observed particles of such energies were not those originally accelerated but were newly produced from or by the higher-energy drifting component.

Bogott, F. H.↗
NASA NTRS1987

On the sources of solar energetic particles

We have examined the time histories of energetic (greater than 1 MeV) particles as detected by instruments in the earth's neighborhood over an 18 year period commencing mid-1967. The majority (greater than 75 percent) of the events extending to proton energies above 20 MeV have their origins in a flare event which includes H-alpha emission, soft x rays, and metric radio bursts of Type 2 and/or Type 4. We have assembled a list of 241 events for which the sources are thus well identified. Two further particle increases have been associated with nonflare events. Of the 82 events originating in regions to the east of central meridian, the sources of 68 (83 percent) were sufficiently energetic that they also generated interplanetary shocks detected at earth. We suggest that shocks are responsible for particles being detectable from source regions not magnetically connected to earth.

Cane, H. V↗
NASA NTRSDate not supplied

SPHINX: A Generalized Tool for Solar Energetic Particle Model Validation

The Integrated Solar Energetic Proton Alert/Warning (ISEP) project was established to aid in the transition of SEP models from the research realm to operational use. This project is a collaboration between the NASA Community Coordinated Model Center (CCMC), the NASA Moon to Mars Space Weather Analysis Office (M2M) and the NASA Space Radiation Analysis Group (SRAG). Through ISEP, the SEP Scoreboards (Intensity, Probability, and All Clear) were developed to visualize real time forecasts from SEP models for use in SRAG operations. To accomplish this, SRAG, CCMC, and M2M work closely with modelers on model development, CCMC works on Scoreboard implementation, and M2M provides human-in-the-loop space weather analysis and ensures that models run in real time.

space weather↗
NASA NTRS1972

Radio tracking of solar energetic particles through interplanetary space.

Satellite observations of traveling solar radio bursts provide information about the propagation of energetic solar particles through interplanetary space. This information leads to data on the solar wind density and gross magnetic field configuration over distances of 1 AU. By placing a radio telescope well above the ionosphere it is possible to observe the radio emission down to frequencies that correspond to emission at distances of the order of 1 AU. The observations reported provide the first 'radio picture' over 1 AU of the spiral magnetic field configuration in interplanetary space.

Fainberg, J.↗
NASA NTRS1990

Possible leakage of energetic particles from the magnetosphere into the upstream region on June 7, 1985

Prognoz 10 observed a series of energetic ion (E not less than 10 KeV) and electron (E not less than 30 KeV) bursts whilst upstream of the dusk bow shock from 2000-2200 UT on June 7, 1985. The particles streamed away from the bow shock along the interplanetary magnetic field (IMF) during periods when the IMF connected the spacecraft to the bow shock/magnetosphere. Both ions and electrons were observed when the IMF connected the spacecraft to the subsolar bow shock, but only ions were observed when the IMF connected the spacecraft to the dusk bow shock. Simultaneous ground and magnetospheric observations are presented which indicate the onset of geomagnetic activity and an increase in magnetospheric energetic particle flux levels just prior to the series of particle bursts observed by Prognoz 10 upstream of the bow shock. The combined observations are consistent with a magnetospheric source for these upstream particle events.

Kudela, K.↗
NASA NTRS1986

Subcritical and supercritical interplanetary shocks - Magnetic field and energetic particle observations

A study of 34 forward interplanetary shocks observed by ISEE 3 during 1978 and 1979 has been conducted. Magnetic field and high-energy particle data have been used, and for each shock the first critical Mach number has been determined. The first surprising result is that the majority of the observed shocks appear to be supercritical, and consistent with their supercritical character, many shocks have a foot and/or an overshoot in the magnetic field structure. Large-amplitude low-frequency waves (period of about 20 s in the spacecraft frame) are commonly observed upstream of all supercritical shocks (except for a few quasi-perpendicular shocks) and also upstream of the few subcritical shocks. Intense particle events are frequently observed at many shocks: spikes at quasi-perpendicular shocks and energetic storm particle events associated with quasi-parallel shocks can be comparably intense. The correlation of the high-energy particle peak flux with various shock parameters is in agreement with the acceleration mechanisms proposed by previous studies.

Bavassano-Cattaneo, M. B.↗
NASA NTRS1991

The magnetosphere of Neptune - Hot plasmas and energetic particles

An overview is presented of the hot plasmas and energetic (not less than 20 keV) particles observed in the vicinity of Neptune by the Low Energy Charged Particle (LECP) experiment aboard the Voyager 2 spacecraft. The LECP findings are presented on the shock, the magnetosheath, the magnetopause, and the cusp of the Neptune's magnetosphere; the middle magnetosphere; the inner magnetosphere and material interactions; the magnetotail and the substorms; and the characteristics of Triton's plasma. It is shown that, in sharp contrast to the Uranian magnetotail, the Neptunian magnetotail shows no evidence of substorm processes.

Mauk, B. H.↗