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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Why Are Most Ground Level Events Associated with High Fe/O Ratios?

In a seminal paper about Ground Level Events (GLEs), Dietrich and Lopate (1999) reported on 24 GLEs from April, 1973 to May, 1998. They noted that alt but one of these GLEs, June 15, 1991, were associated with a Solar Energetic Particle (SEP) event with an enhanced Fe/O ratio. The Fe/O ratio observed for the June 15, 1991 event was only 0.03, well below the nominal coronal abundance of Fe/O = 0.134. For the remaining events, Fe/O ranged from 0.27 to over 3, welt over the nominal coronal value. During Solar Cycle 23, 14 more GLEs were observed, only one of which had very low Fe/O. This was the event of January 20, 2005, the largest ground-level neutron monitor event in 49 years. We will report on our efforts to find out whether the events of June 15, 1991 and January 20, 2005 have features in common, besides high Fe/O, that distinguish them from all other GLE events and may help determine the cause of elevated Fe/O in almost all GLE events. We will use energetic particle, magnetic field, and solar wind plasma data from NASA's IMP-8 Wind, and ACE spacecraft.

von Rosenvinge, Tycho T.↗
NASA NTRS1989

The Advanced Composition Explorer

The Advanced Composition Explorer (ACE) was recently selected as one of two new Explorer-class missions to be developed for launch during the mid-1990's. ACE will observe particles of solar, interplanetary, interstellar, and galactic origins, spanning the energy range from that of the solar wind (approx. 1 keV/nucleon) to galactic cosmic ray energies (several hundred MeV/nucleon). Definitive studies will be made of the abundance of nearly all isotopes from H to Zn (1 less than or = Z less than or = 30), with exploratory isotope studies extending to Zr (Z = 40). To accomplish this, the ACE payload includes six high-resolution spectrometers, each designed to provide the optimum charge, mass, or charge-state resolution in its particular energy range, and each having a geometry factor optimized for the expected flux levels, so as to provide a collecting power a factor of 10 to 1000 times greater than previous or planned experiments. The payload also includes several instruments of standard design that will monitor solar wind and magnetic field conditions and energetic H, He, and electron fluxes. The scientific objectives, instrumentation, spacecraft, and mission approach that were defined for ACE during the Phase-A study period are summarized.

Stone, E. C.↗
NASA NTRS1999

Investigation of the Large Scale Evolution and Topology of Coronal Mass Ejections in the Solar Wind

This investigation is concerned with the large-scale evolution and topology of Coronal Mass Ejections (CMEs) in the solar wind. During this reporting period we have analyzed a series of low density intervals in the ACE (Advanced Composition Explorer) plasma data set that bear many similarities to CMEs. We have begun a series of 3D, MHD (Magnetohydrodynamics) coronal models to probe potential causes of these events. We also edited two manuscripts concerning the properties of CMEs in the solar wind. One was re-submitted to the Journal of Geophysical Research.

Riley, Peter↗
DOE OSTI2025

Occurrence of magnetic reconnection in the heliospheric current sheet

We have analyzed the solar wind properties associated with a comparable number of the heliospheric current sheet (HCS) crossing events by Parker Solar Probe (PSP) ranging from 0.07 to 0.3 au and Advanced Composition Explorer (ACE) at 0.99 au. Nearly all PSP events (7 out of 8) show signatures of magnetic reconnection, which are more frequent than the ACE events (5 out of 8) that show reconnection. Because the HCS reconnection events have occurred in a variety of wind speeds and plasma conditions, for each event, we propose to define an approximate aspect ratio (width/length) of HCS as the ratio between the absolute HCS width (derived from observations) and the distance traveled by Alfvén waves over the propagation time of the solar wind. We find that the aspect ratio defined in such a way tends to be smaller than 0.01 for most reconnecting events, and becomes much larger than 0.01 for non-reconnecting events. This analysis also explains the different occurrence rates of reconnection observed by PSP and ACE. Potential consequences of magnetic reconnection at the HCS are discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2015

End of Life Disposal for Three Libration Point Missions through Manipulation of the Jacobi Constant and Zero Velocity Curves

Flight Dynamics Facility (FDF) located at NASA Goddard Space Flight Center (GSFC) provides the flight dynamics expertise for three Sun-Earth Moon L1 missions. Advanced Composition Explorer (ACE) launched August 1997 Solar and Heliospheric Observatory (SOHO) launched December 1995 Global Geospace Science WIND satellite launched November 1994 entered Lagrange point orbit in 2004.

Ace↗
NASA NTRS2002

IMAGE-EUV Observation of Large Scale Standing Wave Pattern in the Nightside Plasmasphere

We present analyses of a nightside plasmaspheric pattern of bifurcated, filamentary He(+) 30.4-nm emission enhancements observed by IMAGE EUV between approximately 19:40-22:13 UT on 28 June 2000 that indicate the presence of a large-scale, global ULF standing wave pattern. Analysis of coincident IMAGE magnetometer chain data reveals that these ULF waves extend across the magnetic latitude-longitude range of the chain and possess multiple spectral features between 0.6-5-mHz (3-30 minute period). Additionally, analysis of ACE SWE data reveals similarly structured spectral components in the solar wind. Collectively, these analyses lead to the conclusion that the observed large-scale ULF wave pattern is the result of solar wind pressure pulses 'ringing' the inner-magnetosphere.

Six, N. Frank↗
NASA NTRS2001

A Prolonged He(+) Enhancement within a Coronal Mass Ejection in the Solar Wind

A coronal mass ejection and magnetic cloud containing an unusually large enhancement of He+ was observed in the solar wind by the plasma and magnetic field instruments on the Advanced Composition Explorer (ACE) spacecraft on May 2-4, 1998. The He+/He++ ratio during this event exceeded 0.5% for a period of more than 24 hours, and reached values as high as 100%. The high He+/He++ ratio indicates the presence of prominence material, and in fact a disappearing filament and prominence were observed at the Sun in association with this event. The prolonged observation of He+ indicates that prominence material extended through mu ch of this CME, the first such observation in a CME in the solar wind.

Skoug, R. M.↗
NASA NTRS1994

Inter-Agency Consultative Group for Space Science (IACG): Handbook of Missions and Payloads

The ACE spacecraft design is based on the Charge Composition Explorer (CCE) built by Johns Hopkins University (JHU) and the Applied Physics Lab (APL) for the AMPTE program. ACE is designed as a spinning spacecraft with its spin axis aligned to the Earth-Sun axis. The ACE launch weight will be approx. 633 kg, including 105 kg of scientific instruments and 184 kg of propellant. Using a Delta-class expendable launch vehicle, ACE will be launched into an L1 libration point (240 R(sub e)) orbit. Telemetry will be 6.7 kbps average, using tape recorder storage with daily readout to DSN. The experiment power requirement is approximately 76 W nominal and 96 W peak. The prime objective of the ACE mission is: (1) to determine accurate elemental and isotropic abundances including solar matter, local interstellar matter and local galactic matter; (2) to study the origin of elements and evolutionary processing in galactic nucleosynthesis, galactic evolution, origin and evolution of the solar system; (3) to study coronal formation and solar-wind acceleration processes; and (4) to study particle acceleration and transport, including coronal shock acceleration, stochastic flare acceleration, interplanetary shock acceleration, and interstellar acceleration and propagation. To accomplish this objective, ACE will perform comprehensive and coordinated determinations of the elemental and isotopic composition of energetic nuclei accelerated on the Sun, in interplanetary space, and from galactic sources. These observations will span five decades in energy, from solar wind to galactic cosmic ray energies, and will cover the element range from H-1 to Zr-40. Comparison of these samples of matter will be used to study the origin and subsequent evolution of both solar system and galactic material by isolating the effects of fundamental processes that include nucleosynthesis, charged and neutral particle separation, bulk plasma acceleration, and the acceleration of suprathermal and high-energy particles.

Source record↗
NASA NTRS2018

Verification of Real-Time WSA-ENLIL+Cone Simulations of CME Arrival-Time at the CCMC from 2010 to 2016

The Wang-Sheeley-Arge (WSA)-ENLIL+Cone model is used extensively in space weather operations world-wide to model coronal mass ejection (CME) propagation. As such, it is important to assess its performance. We present validation results of the WSA-ENLIL+Cone model installed at the Community Coordinated Modeling Center (CCMC) and executed in real-time by the CCMC space weather team. CCMC uses the WSA-ENLIL+Cone model to predict CME arrivals at NASA missions throughout the inner heliosphere. In this work we compare model predicted CME arrival-times to in situ interplanetary coronal mass ejection leading edge measurements at Solar TErrestrial RElations Observatory-Ahead (STEREO-A), Solar TErrestrial RElations Observatory-Behind (STEREO-B), and Earth (Wind and ACE) for simulations completed between March 2010 and December 2016 (over 1,800 CMEs). We report hit, miss, false alarm, and correct rejection statistics for all three locations. For all predicted CME arrivals, the hit rate is 0.5, and the false alarm rate is 0.1. For the 273 events where the CME was predicted to arrive at Earth, STEREO-A, or STEREO-B, and was actually observed (hit event), the mean absolute arrival-time prediction error was 10.4 +/- 0.9 h, with a tendency to early prediction error of -4.0 h. We show the dependence of the arrival-time error on CME input parameters. We also explore the impact of the multi-spacecraft observations used to initialize the model CME inputs by comparing model verification results before and after the STEREO-B communication loss (since September 2014) and STEREO-A sidelobe operations (August 2014- December 2015). There is an increase of 1.7 h in the CME arrival time error during single, or limited two-viewpoint periods, compared to the three-spacecraft viewpoint period. This trend would apply to a future space weather mission at L5 or L4 as another coronagraph viewpoint to reduce CME arrival time errors compared to a single L1 viewpoint.

MHD / modeling / validation / forecasting / corona↗
NASA NTRS1999

Multi-Spacecraft Observations of Interplanetary Shocks

Using multi-spacecraft observations primarily from ACE and WIND and from IMP 8 and Geotail when available, the 3-dimensional structure of interplanetary shocks on the hundred Earth radii scale will be discussed. The complete magnetic field, and solar wind ion and electron data sets were used to fit the shocks with a full non-linear least squares fitting "Rankine-Hugoniot" technique yielding the local shock surface normals and speeds with associated uncertainties. Multi-spacecraft results reveal that on the distance scale of ACE's L1 halo orbit the shocks deviate from a simple planar geometry. This result has important consequences for the prediction of the exact arrival times of interplanetary shocks at the Earth's magnetosphere, and hence, on the reliability of space weather predictions. It also has implications on the coherence scale of solar wind structures and their evolution from the Sun to Earth.

Smith, C. W.↗
NASA NTRS1999

Multi-Spacecraft Observations of Interplanetary Shocks

Using multi-spacecraft observations primarily from ACE and WIND, and from IMP 8 and Geotail when available, the 3-dimensional structure of interplanetary shocks on the hundred Earth radii scale will be discussed. The complete magnetic field, and solar wind ion and electron data sets were used to fit the shocks with a full non-linear least squares fit "Rankine-Hugoniot" technique yielding the local shock surface normals and speeds with associated uncertainties. Multi-spacecraft results reveal that on the distance scale of ACE's L1 halo orbit the shocks deviate significantly from a simple planar geometry. This result has important consequences for the prediction of the exact arrival times of interplanetary shocks at the Earth's magnetosphere, and hence, on the reliability of space weather predictions. It also has implications on the coherence scale of solar wind structures and their evolution from the Sun to Earth.

Szabo, A.↗
NASA NTRS2021

A Living Catalog of Stream Interaction Regions in the Parker Solar Probe Era

Stream interaction regions (SIRs) and corotating interaction regions (CIRs) are important phenomena in heliospheric physics. These large-scale structures vary temporally and spatially, both in latitude and with radial distance. The additions of Parker Solar Probe(PSP) and Solar Orbiter have allowed for investigations into the radial evolution of these structures over a wide range of heliocentric distances for the first time since the Helios era. To better enable investigations of SIRs and CIRs within the inner heliosphere, we have developed a living catalog of SIR and CIR observations by Parker Solar Probe with corresponding observations by STEREO-A as well as ACE and Wind at 1 au. The methodology used for the identification of events and the generation of this catalog, the initial catalog of PSP observations spanning orbits one through five along with corresponding 1 au observations, and information on accessing the living catalog for future studies is described. This list of SIR and CIR events from PSP and corresponding observations from other heliophysics missions will enable case studies utilizing unique orbital arrangements, as well as aid in future statistical studies to further understand the properties and evolution of these structures.

Catalogs↗
NASA NTRS2004

Identification of Interplanetary Coronal Mass Ejections at 1 AU Using Multiple Solar Wind Plasma Composition Anomalies

We investigate the use of multiple simultaneous solar wind plasma compositional anomalies, relative to the composition of the ambient solar wind, for identifying interplanetary coronal mass ejection (ICME) plasma. We first summarize the characteristics of several solar wind plasma composition signatures (O(+7)/O(+6), Mg/O, Ne/O, Fe charge states, He/p) observed by the ACE and WIND spacecraft within the ICMEs during 1996 - 2002 identsed by Cane and Richardson. We then develop a set of simple criteria that may be used to identify such compositional anomalies, and hence potential ICMEs. To distinguish these anomalies from the normal variations seen in ambient solar wind composition, which depend on the wind speed, we compare observed compositional signatures with those 'expected' in ambient solar wind with the same solar wind speed. This method identifies anomalies more effectively than the use of fixed thresholds. The occurrence rates of individual composition anomalies within ICMEs range from approx. 70% for enhanced iron and oxygen charge states to approx. 30% for enhanced He/p (> 0.06) and Ne/O, and are generally higher in magnetic clouds than other ICMEs. Intervals of multiple anomalies are usually associated with ICMEs, and provide a basis for the identification of the majority of ICMEs. We estimate that Cane and Richardson, who did not refer to composition data, probably identitied approx. 90% of the ICMEs present. However, around 10% of their ICMEs have weak compositional anomalies, suggesting that the presence of such signatures does not provide a necessary requirement for an ICME. We note a remarkably similar correlation between the Mg/O and O(7)/O(6) ratios in hourly-averaged data both within ICMEs and the ambient solar wind. This 'universal' relationship suggests that a similar process (such as minor ion heating by waves inside coronal magnetic field loops) produces the first-ionization potential bias and ion freezing-in temperatures in the source regions of both ICMEs and the ambient solar wind.

Richardson, I. G.↗
NASA NTRS1990

The Advanced Composition Explorer

The Advanced Composition Explorer (ACE) was recently selected as one of two new Explorer-class missions to be developed for launch during the mid-1990s. ACE will observe particles of solar, interplanetary, interstellar, and Galactic origins, spanning the energy range from that of the solar wind to Galactic cosmic ray energies. Definitive studies will be made of the abundance of nearly all isotopes from H to Zn, with exploratory isotope studies extending to Zr. The scientific objectives, instrumentation, spacecraft, and mission approach that were defined for ACE during the Phase-A study period are summarized.

Stone, E. C.↗
NASA NTRS2011

From SOHO to STEREO: Understanding Propagation of Coronal Mass Ejections

Direct comparison between coronal mass ejections (CMEs) from near the Sun and their solar wind counterparts became possible roughly a decade after the discovery of CMEs (Lindsay et aL 1999). This comparison revealed that fast CMEs decelerate and slow CMEs accelerate due to the interaction with the solar wind. Gopalswamy et al (2000) quantified this interaction as an interplanetary acceleration which is useful in predicting the arrival time and speed of CMEs at 1 AU. The interplanetary acceleration is essentially due to the aerodynamic drag between the CME and the solar wind because the propelling force and the solar gravity are effective only near the Sun. Combined remote-sensing and in situ observations from SOHO and Wind/ACE have helped us estimate the influence of the solar wind on the propagation of CMEs. However, these measurements have severe limitations because the remote sensed and in-situ observations correspond to different portions of the CME. Furthermore, the true speeds of Earth-directed CMEs cannot be measured accurately from a spacecraft located along the Sun-Earth line. There have been attempts to model the CME as a cone and get the space speed of the CME, which did improve the travel time predictions. Instruments on board the Solar Terrestrial Relations Observatory (STEREO) mission were able to provide observations of Earth-arriving CMEs without projection effects, while the same CMEs were observed at Sun-Earth L1 by Wind and ACE spacecraft. The quadrature between STEREO and L1 spacecraft presented an ideal situation to study the interplanetary evolution of CMEs and test earlier model results. The quadrature observations did improve the CME travel time predictions, but additional factors such as the unusually slow solar wind, CME cannibalism, and coronal-hole deflection need to be considered to reconcile the difference between observed and predicted travel times. This point is illustrated using the 2011 February 15 CME

Gopalswamy, Natchimuthuk↗
NASA NTRS2024

Multispacecraft Observations of a Widespread Solar Energetic Particle Event on 2022 February 15–16

On 2022 February 15–16, multiple spacecraft measured one of the most intense solar energetic particle (SEP) events observed so far in Solar Cycle 25. This study provides an overview of interesting observations made by multiple spacecraft during this event. Parker Solar Probe (PSP) and BepiColombo were close to each other at 0.34–0.37 au (a radial separation of ∼0.03 au) as they were impacted by the flank of the associated coronal mass ejection (CME). At about 100° in the retrograde direction and 1.5 au away from the Sun, the radiation detector on board the Curiosity surface rover observed the largest ground-level enhancement on Mars since surface measurements began. At intermediate distances (0.7–1.0 au), the presence of stream interaction regions (SIRs) during the SEP arrival time provides additional complexities regarding the analysis of the distinct contributions of CME-driven versus SIR-driven events in observations by spacecraft such as Solar Orbiter and STEREO-A, and by near-Earth spacecraft like ACE, SOHO, and WIND. The proximity of PSP and BepiColombo also enables us to directly compare their measurements and perform cross-calibration for the energetic particle instruments on board the two spacecraft. Our analysis indicates that energetic proton measurements from BepiColombo and PSP are in reasonable agreement with each other to within a factor of ∼1.35. Finally, this study introduces the various ongoing efforts that will collectively improve our understanding of this impactful, widespread SEP event.

Solar energetic particles↗
NASA NTRS2008

The Solar Energetic Particle Event of December 14, 2006

We report on observations of a solar energetic particle event by instruments on five different spacecraft: the Advanced Composition Explorer (ACE), STEREO A and B, WIND, and GOES II. The event began with a class X1.5 .soft x-ray flare in AR930 on December 14 at 22:15 UT. At this time the two STEREO spacecraft were located outside the Earth's magnetosphere and were heading for their first lunar swing-by on December 15. The x-ray event was located on the sun at W46, a longitude which is nominally well-connected magnetically to the Earth. An interplanetary shock, associated with an earlier X3.4 event on December 13 (also from AR930), passed the Earth on December 14 at approx.13:56 (time at ACE). The corresponding magnetic cloud arrived at approx.22 UT on December 14, close to the time of the onset of the particle event associated with the X1.5 flare, and extended until approx.08 UT on December 15. The intensity of approx.14 MeV protons at STEREO A shows three dips by factors of approx.10 or more during the early stages of this event while the spacecraft was within the magnetic cloud. Similar dips are seen for protons to at least 100 MeV. In principle, these dips could have been caused by changes in the magnetic field direction with respect to the particle telescope's field of view while viewing a beamed particle distribution. However, this possibility can be ruled out because the magnetic field at the spacecraft shows no evidence of such directional variations, and similar particle intensity dips were seen by instruments on other spacecraft in the near-Earth solar wind. We shall present evidence that the dips were actually associated with varying magnetic connection to the Sun within the magnetic cloud. These dips were not observed at GOES II, suggesting they were somehow smoothed out by passage into the magnetosphere.

vonRosenvinge, T. T.↗