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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 181 records · Page 10
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NASA NTRS2004

XMM-Newton Observations of Solar Wind Charge Exchange Emission

We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

Snowden, S. L.↗
NASA NTRS2005

Chandra Observations of Comet 2P/Encke 2003: First Detection of a Collisionally Thin, Fast Solar Wind Charge Exchange System

We report the results of 15 hr of Chandra observations of comet 2P/Encke 2003 on November 24. X-ray emission from comet Encke was resolved on scales of 500-40,000 km, with unusual morphology due to the presence of a low-density, collisionally thin (to charge exchange) coma. A light curve with peak-to-peak amplitude of 20% consistent with a nucleus rotational period of 11.1 hr was found, further evidence for a collisionally thin coma. We confirm emission lines due to oxygen and neon in the 800-1000 eV range but find very unusual oxygen and carbon line ratios in the 200-700 eV range, evidence for low-density, high effective temperature solar wind composition. We compare the X-ray spectral observation results to contemporaneous measurements of the coma and solar wind made by other means and find good evidence for the dominance of a postshock bubble of expanding solar wind plasma, moving at 600 km/s with charge state composition between that of the "fast" and "slow" solar winds.

Lisse, C. M.↗
NASA NTRS2019

NIAC Phase I Final Report: On-Orbit, Collision-Free Mapping of Small Orbital Debris

Sub-centimeter orbital debris is currently undetectable using ground-based radar and optical methods. However, the pits in Space Shuttle windows produced by paint chips (e.g. the 3.8mm diameter pit produced by a 0.2mm paint chip on STS-7) demonstrate that small debris can cause serious damage to spacecraft. Recent analytical, computational and experimental work has shown that charged objects moving quickly through a plasma will cause the formation of solitons in the plasma density. Due to their exposure to the solar wind plasma environment, even the smallest space debris will be charged. Depending on the debris size, charge and velocity, the plasma signature of the solitons may be detected by simple instrumentation on spacecraft. We will describe the amplitude and velocity of solitons that may be produced by mm-cm scale orbital debris in LEO. We will discuss the feasibility of mapping sub-cm orbital debris using a fleet of CubeSats equipped with Langmuir probes. The time and fleet size required to map the debris will also be described. Plasma soliton detection would be the first collision-free method of mapping the small debris population.

Orbital Debris↗
NASA NTRS1971

Magnetic field anomalies in the lunar wake

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar wind flow. A statistical study of umbral increases and of penumbral variations was conducted with respect to variation in the solar wind plasma value beta, the distance from the moon, and the selenographic longitude of the limb regions of the lunar surface in the solar wind flow. All lunar wake anomalies show a strong positive correlation with the plasma value beta, while only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of penumbral anomaly occurrence with selenographic longitude of the exposed lunar limb in the solar wind flow.

Whang, Y. C.↗
NASA NTRS1974

Pioneer Solar Plasma and Magnetic Field Measurements in Interplanetary Space During August 2-17, 1972

Solar wind plasma and magnetic field measurements from Pioneers 9 and 10 during August 2-17, 1972, reveal complex and large-amplitude variations on a one-hour time scale and numerous discontinuities. During this time period an approximate radial alignment of the two spacecraft as seen from the Sun occurred with heliocentric distances of 0.8 AU for Pioneer 9 and 2.2 AU for Pioneer 10, both at 45 deg east of the Earth's solar longitude. The peak hourly average solar wind proton bulk velocity measured at Pioneer 9 was 990 km sec (exp -1) during hour 0 UT of August 5. The peak hourly average proton number density was 62 cm (exp -3) during hour 11 UT of August 3. The peak solar wind speeds are generally much reduced at Pioneer 10 compared with those observes at Pioneer 9. The peak 30 minute average magnetic field magnitude was 85 gamma during 1245 - 1315 UT of August 3. The Pioneer 9 data indicate passage of four fast forward interplanetary shocks, and one slow forward interplanetary shock.

Mihalov, J. D.↗
NASA NTRS2016

MAVEN Observation of an Obliquely Propagating Low-Frequency Wave Upstream of Mars

We report Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observations of a large amplitude low-frequency plasma wave that propagated oblique to the ambient magnetic field upstream of Mars along with a non-solar-wind plasma component that had a flow velocity perpendicular to the magnetic field. We consider nine possibilities for this wave that include various combinations of its propagation direction, polarization in the solar wind frame, and ion source responsible for its generation. Using the observed wave parameters and the measured plasma parameters as constraints, we uniquely identify the wave by systematically discarding these possibilities. We determine that the wave is a right-hand polarized wave that propagated upstream in the solar wind frame. We find two possibilities for the ion source that can be responsible for this wave generation. They are either newly born pickup protons or reflected solar wind protons from the bow shock.We determine that the observed non-solar-wind component is not responsible for the wave generation, and it is likely that the non-solar-wind component was merely perturbed by the passage of the wave.

low frequency wave↗
NASA NTRS1983

ISEE-3 - A late entry in the great comet chase

The ISEE-3 spacecraft, currently in a figure-8 traverse of the geomagnetic tail between 80-220 earth radii, is being redirected to a flyby of the Giacobini-Zinner comet in 1985. The satellite carries experiments for the solar wind plasma, magnetic field data, plasma wave and composition, radio waves, and energetic protons, and can gather data on the solar wind-comet interaction. A double lunar swingby will be employed to establish the intercept trajectory, yielding a total velocity change of 100 m/sec, with a reserve of 100 m/sec for midcourse corrections. The comet will be encountered at a distance of 3000 km in September 1985, followed by passage through the Halley's comet tail 5000 km from the nucleus in March 1986.

Farquhar, R.↗
NASA NTRS1977

Pioneer 9 and Pioneer 10 observations of the solar wind associated with the August 1972 events

Observations are presented of the changes in the solar wind proton parameters at 0.8 and 2.2 AU as a result of the solar flares in August 1972. These observations were obtained by the NASA Ames Research Center solar wind plasma analyzer experiments on Pioneer 9 and Pioneer 10. High time resolution measurements are presented of the solar wind proton speed associated with the arrival of the interplanetary shocks at Pioneer 9 and Pioneer 10. For these events, differential ion energy per unit charge spectra are shown which indicate the changes in the solar wind ion distribution function associated with the arrival of each of the interplanetary shocks. Four fast shocks are identified at Pioneer 9, and it is found that previously the time of arrival of the first interplanetary shock at Pioneer 9 was not correctly identified. Two fast shocks and one reverse shock are identified at Pioneer 10.

Intriligator, D. S.↗
NASA NTRS1972

Magnetic-field anomalies in the lunar wake.

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar-wind flow. A statistical study of the umbral increases and penumbral decreases and increases was conducted with variation of the solar-wind plasma beta value, the distance from the moon and the selenographic longitude of the limb regions of the lunar surface in the solar-wind flow. All lunar-wake anomalies show a strong positive correlation with the plasma beta value, whereas only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of occurrence of penumbral anomaly with selenographic longitude of the exposed lunar limb in the solar-wind flow.

Whang, Y. C.↗
NASA NTRS1994

A survey of bidirectional greater than or equal to MeV ion flows during the Helios 1 and Helios 2 mission: Observations from the Goddard Space Flight Center instruments

A survey is made of 1.1-2.1 MeV and 3-21 MeV bidirectional ion flows (BIFs) in the solar wind at 0.3-1.0 AU observed by the Goddard Space Flight Center instruments on the Helios 1 and Helios 2 spacecraft during the spacecraft mission in 1974-1984 and 1979-1980, respectively. Some 774 events have been identified Helios 1, and 223 at Helios 2, with mean durations of approximately 2.5 hr at each spacecraft. BIFs were observed for approximately 1%-3% of the observation time during solar minimum conditions in 1975-1977 and for approximately 10%-14% in 1980-1981 around solar maximum. These occurrence rates are similar to those of approximately 1 MeV BIFs observed at the Interplanetary Monitoring Platform 8 and International Sun Earth Explorers (ISEE) 3 spacecraft, and of bidirectional electron heat fluxes at ISEE 3. Solar wind plasma parameters during BIFs were similar to those found generally during the Helios missions, though BIFs have a greater tendency to be associated with cool, low-beta plasma, moderately enhanced and low-variance magnetic fields, both less than 300 km/s and greater than 750 km/s solar wind. Solar wind features associated with the greater than 4 hr duration BIFs include clear plasma shock-driver signatures: approximately 36% of the events; postshock plasma, not associated with shock-driver signatures: approximately 13%; noncompressive density enhancements: approximately 22% (half associated with plasma proton temperature depression); high-speed streams not associated with shocks: approximately 10%; corotating interaction regions: approximately 5%; immediately upstream of shocks: approximately 5%. Around 8% were associated with other solar wind structures, while approximately 4% showed no associated structure. BIFs were present in several of the shock drivers associated with coronal mass ejections (CMEs) observed by the Solwind coronagraph during intervals when Helios 1 was off the limbs of the Sun, showing directly the association of some BIFs with CMEs. some BIFs with CMEs.

Richardson, I. G.↗
NASA NTRS1976

A quasi-linear kinetic equation for cosmic rays in the interplanetary medium

A kinetic equation for interplanetary cosmic rays is set up with the aid of weak-plasma-turbulence theory for an idealized radially symmetric model of the interplanetary magnetic field. As a starting point, this treatment invokes the Vlasov equation instead of the traditional Fokker-Planck equation. Quasi-linear theory is applied to obtain a momentum diffusion equation for the heliocentric frame of reference which describes the interaction of cosmic rays with convecting magnetic irregularities in the solar-wind plasma. Under restricted conditions, the well-known equation of solar modulation can be obtained from this kinetic equation.

Luhmann, J. G.↗
NASA NTRS1992

Ulysses plasma observations of coronal mass ejections near 2.5 AU

The Ulysses solar wind plasma experiment observed a series of interplanetary shocks and coronal mass ejections (CMEs), the latter evidenced by counterstreaming electrons and a variety of ion signatures, during March and April 1991. A striking sequence was observed near 2.5 AU from March 23 through April 2, with the second of two counterstreaming events lasting 6.4 days. The plasma observations for these features are summarized suggesting that the second counterstreaming period may be two juxtaposed CMEs. The relationship between the events observed at Ulysses, about 60 deg east of earth in ecliptic longitude, and those causing a geomagnetic storm on March 24, is unclear.

Phillips, J. L.↗
NASA NTRS1976

Hot plasmas in the earth's magnetosphere

Several recent findings from observational researches of various facets of magnetospheric plasmas are summarized. These new results encompass entry of solar wind plasmas into the dayside magnetosphere, the acceleration of plasmas both at great distances from the earth in the magnetotail and at low altitudes over auroral luminosities, and the substantial contributions of the upper ionosphere to the plasma compositions of the distant magnetosphere.

Frank, L. A.↗
NASA NTRS1978

The composition of corotating energetic particle streams

The relative abundances of 1.5-23 MeV per nucleon ions in corotating nucleon streams are compared with ion abundances in particle events associated with solar flares and with solar and solar wind abundances. He/O and C/O ratios are found to be a factor of the order 2-3 greater in corotating streams than in flare-associated events. The distribution of H/He ratios in corotating streams is found to be much narrower and of lower average value than in flare-associated events. H/He in corotating energetic particle streams compares favorably in both lack of variability and numerical value with H/He in high-speed solar wind plasma streams. The lack of variability suggests that the source population for the corotating energetic particles is the solar wind, a suggestion consistent with acceleration of the corotating particles in interplanetary space.

Mcguire, R. E.↗
NASA NTRS1982

Lion roars and nonoscillatory drift mirror waves in the magnetosheath

It is shown that Extremely Low Frequency, or 'lion' roars are closely coupled to quasi-periodic, large scale magnetosheath structures. Because the latter are waves generated by the drift mirror instability, an attempt is made to identify and describe the magnetic and plasma features associated with this instability. Observations and analyses of the large scale structures using ISEE 1 and 2 data for the earth's magnetosheath and Pioneer 11 data for Jupiter and Saturn are presented, along with the background of the drift mirror waves. The cyclotron and drift mirror instabilities occurring in the magnetosheath are natural relaxation processes which reduce the plasma pressure anisotropies created by preferential heating of the solar wind plasma as it passes through the bow shock, as well as the compression occurring when the plasma and fields approach the near-subsolar magnetopause.

Tsurutani, B. T.↗
NASA NTRS2015

Comparisons of Characteristics of Magnetic Clouds and Cloud-Like Structures During 1995-2012

Using eighteen years (1995 - 2012) of solar wind plasma and magnetic field data (observed by the Wind spacecraft), solar activity (e.g. sunspot number: SSN), and the geomagnetic activity index (Dst), we have identified 168 magnetic clouds (MCs) and 197 magnetic cloud - like structures (MCLs), and we have made relevant comparisons. The following features are found during seven different periods (TP: Total period during 1995 - 2012, P1 and P2: first and second half period during 1995 - 2003 and 2004 - 2012, Q1 and Q2: quiet periods during 1995 - 1997 and 2007 - 2009, A1 and A2: active periods during 1998 - 2006 and 2010 - 2012). (1) During the total period the yearly occurrence frequency is 9.3 for MCs and 10.9 for MCLs. (2) In the quiet periods Q1 > Q1 and Q2 > Q2, but in the active periods A1 < A1 and A2 < A2. (3) The minimum Bz (Bzmin) inside of a MC is well correlated with the intensity of geomagnetic activity, Dstmin (minimum Dst found within a storm event) for MCs (with a Pearson correlation coefficient, c.c. = 0.75, and the fitting function is Dstmin = 0.90+7.78Bzmin), but Bzmin for MCLs is not well correlated with the Dst index (c.c. = 0.56, and the fitting function is Dstmin = -9.40+ 4.58 Bzmin). (4) MCs play a major role in producing geomagnetic storms: the absolute value of the average Dstmin ( MC = -70 nT) for MCs associated geomagnetic storms is two times stronger than that for MCLs ( MCL = -35 nT), due to the difference in the IMF (interplanetary magnetic field) strength. (5) The SSN is not correlated with MCs ( TP, c.c. = 0.27), but is well associated with MCLs ( TP, c.c. = 0.85). Note that the c.c. for SSN vs. P2 is higher than that for SSN vs. P2. (6) Averages of IMF, solar wind speed, and density inside of the MCs are higher than those inside of the MCLs. (7) The average of MC duration (approx. = 18.82 hours) is approx. = 20 % longer than the average of MCL duration (approx. = 15.69 hours). (8) There are more MCs than MCLs in the quiet solar period, and more MCLs than MCs in the active solar period, probably due to the interaction between a MC and another significant interplanetary disturbance (including another MC) which could obviously change the character of a MC, but we speculate that some MCLs are no doubt due to other factors such as complex birth conditions at the Sun.

CME↗
NASA NTRS2004

Magnetic Fields and Flows in Open Magnetic Structures

Open magnetic structures connect the solar surface to the heliosphere and are thus of great interest in solar-terrestrial physics. This talk is primarily an observational review of what is known about magnetic fields and particularly flows in such regions with special focus on coronal holes and origins of the fast solar wind. First evidence of the connection between these two features was seen in correlations of Skylab data with in situ measurements of the solar wind soon after the discovery of coronal holes, which are now known to emanate from unipolar magnetic regions at the photosphere. Subsequently many observations of have been made, ranging from oscillations in the underlying photosphere and chromosphere, to possible beginnings of the solar wind as observed by Doppler shifts in high chromospheric and transition-region lines, to coronagraphic time-lapse studies of outward-moving blobs of material which perhaps trace elements of solar-wind plasma. Some of the many unresolved and controversial issues regarding details of these observations and their association with the solar wind will be discussed.

Jones, Harrlson P.↗