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1

The latitude dependencies of the solar wind. [of interplanetary magnetic field polarity and configurations  

NASA Technical Reports Server (NTRS)

The motion of spacecraft following the earth's orbit occurs within the solar latitude range of 7 deg 15 min N on approximately September 7 to 7 deg 15 min S on approximately March 6. The latitude dependencies so far detected within this range have shown that the photospheric dipole-like field of the sun makes very important contributions to the interplanetary magnetic field (IMF) observed near the ecliptic. Changes in geomagnetic activity from even to odd numbered 11-year solar cycles are related to changes in the sun's dipolar field. The north-south IMF component and meridional, nonradial flow are important to a complete understanding of steady-state solar wind dynamics. Coronal conditions must be latitude-dependent in a way that accounts for the observed latitude dependence of the velocity and density of the solar wind.

Rosenberg, R. L.; Winge, C. R., Jr.

1974-01-01

2

Cosmic ray modulation with a Fisk-type heliospheric magnetic field and a latitude-dependent solar wind speed  

NASA Astrophysics Data System (ADS)

The effect of a latitude-dependent solar wind speed on a Fisk heliospheric magnetic field [Fisk, L. A. Motion of the footpoints of heliospheric magnetic field lines at the Sun: implications for recurrent energetic particle events at high heliographic latitudes. J. Geophys. Res. 101, 15547-15553, 1996] was first discussed by Schwadron and Schwadron and McComas [Schwadron, N.A. An explanation for strongly underwound magnetic field in co-rotating rarefaction regions and its relationship to footpoint motion on the the sun. Geophys. Res. Lett. 29, 1-8, 2002. and Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41-1, 2003]. Burger and Sello [Burger, R.A., Sello, P.C. The effect on cosmic ray modulation of a Parker field modified by a latitudinal-dependent solar wind speed. Adv. Space Res. 35, 643-646, 2005] found a significant effect for a simplified 2D version of a latitude-dependent Fisk-type field while Miyake and Yanagita [Miyake, S., Yanagita, S. The effect of a modified Parker field on the modulation of the galactic cosmic rays. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, 445-448, 2007] found a smaller effect. The current report improves on a previous attempt Hitge and Burger [Hitge, M., Burger, R.A. The effect of a latitude-dependent solar wind speed on cosmic-ray modulation in a Fisk-type heliospheric magnetic field. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, pp. 449-450, 2007] where the global change in the solar wind speed and not the local speed gradient was emphasized. The sheared Fisk field of Schwadron and McComas [Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: Favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41-1, 2003.) is similar to the current Schwadron-Parker hybrid field. Little difference is found between the effects of a Parker field and a Schwadron-Parker hybrid field on cosmic-ray modulation, in contrast to the results of Burger and Sello and Miyake and Yanagita [Burger, R.A., Sello, P.C. The effect on cosmic ray modulation of a Parker field modified by a latitudinal-dependent solar wind speed. Adv. Space Res. 35, 643-646, 2005 and Miyake, S., Yanagita, S. The effect of a modified Parker field on the modulation of the galactic cosmic rays. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, pp. 445-448, 2007]. The two-dimensional approximation used by these authors is therefore inadequate to model the complexities of the actual three-dimensional field. We also show that a Fisk-type field with a latitude-dependent solar wind speed (Schwadron-Parker hybrid field) decreases both the relative amplitude of recurrent cosmic ray intensity variations and latitude gradients and yields similar constants of proportionality for these quantities as for the constant solar wind speed case.

Hitge, M.; Burger, R. A.

2010-01-01

3

Time trends and latitude dependence of uveal and cutaneous malignant melanoma induced by solar radiation  

SciTech Connect

In order to evaluate the role of solar radiation in uveal melanoma etiology, the time and latitude dependency of the incidence rates of this melanoma type were studied in comparison with those of cutaneous malignant melanoma (CMM). Norway and several other countries with Caucasian populations were included. There is a marked north - south gradient of the incidence rates of CMM in Norway, with three times higher rates in the south than in the north. No such gradient is found for uveal melanoma. Similar findings have been published for CMM in other Caucasian populations, with the exception of Europe as a whole. In most populations the ratios of uveal melanoma incidence rates to those of CMM tend to decrease with increasing CMM rates. This is also true for Europe, in spite of the fact that in this region there is an inverse latitude gradient of CMM, with higher rates in the north than in the south. In Norway the incidence rates of CMM have increased until about 1990 but have been constant, or even decreased (for young people) after that time, indicating constant or decreasing sun exposure. The uveal melanoma rates have been increasing after 1990. In most other populations the incidence rates of CMM have been increasing until recently while those of uveal melanoma have been decreasing. These data generally support the assumption that uveal melanomas are not generated by ultraviolet (UV) radiation and that solar UV, via its role in vitamin D photosynthesis, may have a protective effect.

Moan, J.; Setlow, R.; Cicarma, E.; Porojnicu, A. C.; Grant, W. B.; Juzeniene, A.

2010-01-01

4

Latitude-Dependent Effects in the Stellar Wind of Eta Carinae  

NASA Technical Reports Server (NTRS)

The Homunculus reflection nebula around eta Carinae provides the rare opportunity to observe the spectrum of a star from more than one direction. In the case of eta Car, the nebula's geometry is known well enough to infer how wind profiles vary with latitude. We present STIS spectra of several positions in the Homunculus, showing directly that eta Car has an aspherical and axisymmetric stellar wind. P Cygni absorption in Balmer lines depends on latitude, with relatively high velocities and strong absorption near the polar axis. Stronger absorption at high latitudes is surprising, and it suggests higher mass flux toward the poles, perhaps resulting from equatorial gravity darkening on a rotating star. Reflected profiles of He I lines are more puzzling, and offer clues to eta Car's wind geometry and ionization structure. During eta Car's high-excitation state in March 2000, the wind had a fast, dense polar wind, with higher ionization at low latitudes. Older STIS data obtained since 1998 reveal that this global stellar-wind geometry changes during eta Car's 5.5 year cycle, and may suggest that this star s spectroscopic events are shell ejections. Whether or not a companion star triggers these outbursts remains ambiguous. The most dramatic changes in the wind occur at low latitudes, while the dense polar wind remains relatively undisturbed during an event. The apparent stability of the polar wind also supports the inferred bipolar geometry. The wind geometry and its variability have critical implications for understanding the 5.5 year cycle and long-term variability, but do not provide a clear alternative to the binary hypothesis for generating eta Car s X-rays.

Smith, Nathan; Davidson, Kris; Gull, Theodore R.; Ishibashi, Kazunori; Hillier, D. John

2002-01-01

5

A COMPANION AS THE CAUSE OF LATITUDE-DEPENDENT EFFECTS IN THE WIND OF ETA CARINAE  

SciTech Connect

We analyze spatially resolved spectroscopic observations of the Eta Carinae binary system obtained with the Hubble Space Telescope/STIS. Eta Car is enshrouded by the dusty Homunculus nebula, which scatters light emitted by the central binary and provides a unique opportunity to study a massive binary system from different vantage points. We investigate the latitudinal and azimuthal dependence of H{alpha} line profiles caused by the presence of a wind-wind collision (WWC) cavity created by the companion star. Using two-dimensional radiative transfer models, we find that the wind cavity can qualitatively explain the observed line profiles around apastron. Regions of the Homunculus which scatter light that propagated through the WWC cavity show weaker or no H{alpha} absorption. Regions scattering light that propagated through a significant portion of the primary wind show stronger P Cygni absorption. Our models overestimate the H{alpha} absorption formed in the primary wind, which we attribute to photoionization by the companion, not presently included in the models. We can qualitatively explain the latitudinal changes that occur during periastron, shedding light on the nature of Eta Car's spectroscopic events. Our models support the idea that during the brief period of time around periastron when the primary wind flows unimpeded toward the observer, H{alpha} absorption occurs in directions toward the central object and Homunculus SE pole, but not toward equatorial regions close to the Weigelt blobs. We suggest that observed latitudinal and azimuthal variations are dominated by the companion star via the WWC cavity, rather than by rapid rotation of the primary star.

Groh, J. H. [Geneva Observatory, Geneva University, Chemin des Maillettes 51, CH-1290 Sauverny (Switzerland); Madura, T. I.; Weigelt, G. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Hillier, D. J. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States); Kruip, C. J. H., E-mail: jose.groh@unige.ch [Leiden Observatory, Leiden University, Postbus 9513, NL-2300 RA Leiden (Netherlands)

2012-11-01

6

A Companion as the Cause of Latitude-dependent Effects in the Wind of Eta Carinae  

NASA Astrophysics Data System (ADS)

We analyze spatially resolved spectroscopic observations of the Eta Carinae binary system obtained with the Hubble Space Telescope/STIS. Eta Car is enshrouded by the dusty Homunculus nebula, which scatters light emitted by the central binary and provides a unique opportunity to study a massive binary system from different vantage points. We investigate the latitudinal and azimuthal dependence of H? line profiles caused by the presence of a wind-wind collision (WWC) cavity created by the companion star. Using two-dimensional radiative transfer models, we find that the wind cavity can qualitatively explain the observed line profiles around apastron. Regions of the Homunculus which scatter light that propagated through the WWC cavity show weaker or no H? absorption. Regions scattering light that propagated through a significant portion of the primary wind show stronger P Cygni absorption. Our models overestimate the H? absorption formed in the primary wind, which we attribute to photoionization by the companion, not presently included in the models. We can qualitatively explain the latitudinal changes that occur during periastron, shedding light on the nature of Eta Car's spectroscopic events. Our models support the idea that during the brief period of time around periastron when the primary wind flows unimpeded toward the observer, H? absorption occurs in directions toward the central object and Homunculus SE pole, but not toward equatorial regions close to the Weigelt blobs. We suggest that observed latitudinal and azimuthal variations are dominated by the companion star via the WWC cavity, rather than by rapid rotation of the primary star. Based on observations made with HST/STIS.

Groh, J. H.; Madura, T. I.; Hillier, D. J.; Kruip, C. J. H.; Weigelt, G.

2012-11-01

7

Solar Wind Five  

NASA Technical Reports Server (NTRS)

Topics of discussion were: solar corona, MHD waves and turbulence, acceleration of the solar wind, stellar coronae and winds, long term variations, energetic particles, plasma distribution functions and waves, spatial dependences, and minor ions.

Neugebauer, M. (editor)

1983-01-01

8

The Solar Wind  

NSDL National Science Digital Library

This site describes the nature of the solar winds and the relationships between its speed and solar features. The effect of the variations in the speed of the solar wind on the magnetosphere of the Earth is also discussed, along with the research results of the Ulysses spacecraft and the Advanced Composition Explorer (ACE) satellite. The site also provides links to solar wind conditions for the last seven days and the last 24 hours.

Hathaway, David

9

The Solar Wind  

NASA Technical Reports Server (NTRS)

The first evidence of the solar wind was provided through observations of comet tail deflections by L. Biermann in 1951. A cometary ion tail is oriented along the difference between the cometary and solar wind velocities, whereas the dust tail is in the antisunward direction; the ion tail directions demonstrated the existence of an outflow of ionized gas from the Sun (the solar wind) and allowed estimates of solar wind speed. Spacecraft observations have now established that at 1 AU the solar wind has a typical ion number density of about 7 /cc and is composed by number of about 95% protons and 5% Helium, with other minor ions also present. The solar wind as observed at 1 AU in the ecliptic has speeds typically in the range 300-700 km/ s. At such speeds ions travel from the Sun to 1 AU in from 2.5 to 6 days. The impact of the solar wind on planets with magnetic fields (Earth, Jupiter, Saturn, Uranus, Neptune) causes phenomena such as magnetospheres, aurorae, and geomagnetic storms, whereas at objects lacking magnetospheres (Mars, Venus, comets), atmospheric neutrals undergo charge exchange and are picked up by the solar wind flow. The solar wind also shields the Earth from low energy cosmic rays, and is responsible for the existence of the anomalous component of the cosmic rays a low energy component that is created locally rather than in the galaxy. Presented here is a brief introduction to the solar wind and a description of some current topics of research. Solar wind properties vary a great deal due to the changing magnetic structure on the Sun.

Goldstein, B. E.

1998-01-01

10

Solar wind composition  

NASA Technical Reports Server (NTRS)

Advances in instrumentation have resulted in the determination of the average abundances of He, C, N, O, Ne, Mg, Si, S, and Fe in the solar wind to approximately 10%. Comparisons with solar energetic particle (SEP) abundances and galactic cosmic ray abundances have revealed many similarities, especially when compared with solar photospheric abundances. It is now well established that fractionation in the corona results in an overabundance (with respect to the photosphere) of elements with first ionization potentials less than 10 eV. These observations have in turn led to the development of fractionation models that are reasonably successful in reproducing the first ionization (FIP) effect. Under some circumstances it has been possible to relate solar wind observations to particular source regions in the corona. The magnetic topologies of the source regions appear to have a strong influence on the fractionation of elements. Comparisons with spectroscopic data are particularly useful in classifying the different topologies. Ions produced from interstellar neutral atoms are also found in the solar wind. These ions are picked up by the solar wind after ionization by solar radiation or charge exchange and can be identified by their velocity in the solar wind. The pick-up ions provide most of the pressure in the interplanetary medium at large distances. Interstellar abundances can be derived from the observed fluxes of solar wind pick-up ions.

Ogilvie, K. W.; Coplan, M. A.

1995-01-01

11

SOLAR WIND CORRELATIONS: USING A SOLAR WIND MONITOR SUCCESSFULLY  

E-print Network

SOLAR WIND CORRELATIONS: USING A SOLAR WIND MONITOR SUCCESSFULLY K.I. PAULARENA AND J.D. RICHARDSON.N. ZASTENKER AND P.A. DALIN Space Research Institute, RAS, Moscow, Russia Abstract. Solar wind plasma to which distant solar wind plasma measurements (such as those from near Earth's L1 point) represent

Richardson, John

12

The Solar Wind  

NSDL National Science Digital Library

This set of web pages provide an elementary introduction to the solar wind, starting with evidence from comet tails and continuing to Parker's theory of the Sun's corona and observations of the solar wind. A graphic exercise, suitable for the classroom, for tracing interplanetary magnetic field lines "dragged out" of the Sun by the solar wind is included. These pages are part of a larger site, "The Exploration of the Earth's Magnetosphere", that gives a non-mathematical introduction to the magentic properties of the sun and planets, space weather, and the motion of charged particles in magnetic fields. A Spanish translation is available.

Stern, David

2005-04-27

13

Flank solar wind interaction  

NASA Technical Reports Server (NTRS)

In this report we will summarize the results of the work performed under the 'Flank Solar Wind Interaction' investigation in support of NASA's Space Physics Guest Investigator Program. While this investigation was focused on the interaction of the Earth's magnetosphere with the solar wind as observed by instruments on the International Sun-Earth Explorer (ISEE) 3 spacecraft, it also represents the culmination of decades of research performed by scientists at TRW on the rich phenomenology of collisionless shocks in space.

Moses, Stewart L.; Greenstadt, Eugene W.; Coroniti, Ferdinand V.

1994-01-01

14

Solar wind composition experiment  

NASA Technical Reports Server (NTRS)

The Apollo 16 SWC experiment is a continuation of the earlier experiments; however, an essential change was introduced in the solar wind particle collection technique. Platinum surfaces were incorporated in the collector foil, and use was made of a layer technique for distinguishing particles of different energies and different directions of arrival. The improvements and the expanded scope of the Apollo 16 experiment, relative to the earlier SWC experiments, can be summarized as follows: elimination of possible residual dust contamination by treating the platinum foil sections with dilute hydrofluoric acid before analysis; increased accuracy of solar wind argon abundance; determination of solar wind albedo; and search for helium in the energy range above approximately 40 KeV/nucleon.

Geiss, J.; Buehler, F.; Cerutti, H.; Eberhardt, P.; Filleux, C.

1972-01-01

15

Petrovay: Solar physics Solar wind and heliosphere THE SOLAR WIND AND THE HELIOSPHERE  

E-print Network

Petrovay: Solar physics Solar wind and heliosphere THE SOLAR WIND AND THE HELIOSPHERE 1951: First radial (aberration effect). 1958: Parker's supersonic wind model 1962: Mariner-2 detects solar wind. v shock. 2012: V1 crosses heliopause. #12;Petrovay: Solar physics Solar wind and heliosphere Reminder

Petrovay, Kristóf

16

Solar wind stream interfaces  

Microsoft Academic Search

Measurements aboard Imp 6, 7, and 8 reveal that approximately one third of all high-speed solar wind streams observed at 1 AU contain a sharp boundary (of thickness less than approx.4 x 10⁴ km) near their leading edge, called a stream interface, which separates plasma of distinctly different properties and origins. Identified as discontinuities across which the density drops abruptly,

J. T. Gosling; J. R. Asbridge; S. J. Bame; W. C. Feldman

1978-01-01

17

Solar Wind Electrons  

Microsoft Academic Search

Average characteristics of solar wind electron velocity distributions as well as the range and nature of their variations are presented. The measured distributions are generally symmetric about the heat flux direction and are adequately parameterized by the superposition of a nearly bi-Maxwellian function which characterizes the low-energy electrons and a bi-Maxwellian function which characterizes a distinct, ubiquitous component of higher-energy

W. C. Feldman; J. R. Asbridge; S. J. Bame; M. D. Montgomery; S. P. Gary

1975-01-01

18

Discontinuities in the solar wind  

Microsoft Academic Search

The nonuniform emission of the solar wind from the sun means that conditions are established which favor the development of discontinuities in the plasma parameters. Since the solar wind is in rapid proper motion with respect to the sun and the earth, examination of these discontinuities requires that the wind velocity be transformed away. Then it is found that they

D. S. Colburn; C. P. Sonett

1966-01-01

19

Composition of the Solar Wind  

NASA Technical Reports Server (NTRS)

The solar wind reflects the composition of the Sun and physical processes in the corona. Analysis produces information on how the solar system was formed and on physical processes in the corona. The analysis can also produce information on the local interstellar medium, galactic evolution, comets in the solar wind, dust in the heliosphere, and matter escaping from planets.

Suess, S. T.

2007-01-01

20

77 FR 61597 - Avalon Wind, LLC; Avalon Wind 2, LLC; Catalina Solar, LLC; Catalina Solar 2, LLC; Pacific Wind...  

Federal Register 2010, 2011, 2012, 2013

...EL12-109-000] Avalon Wind, LLC; Avalon Wind 2, LLC; Catalina Solar, LLC; Catalina Solar 2, LLC; Pacific Wind Lessee, LLC; Pacific Wind 2, LLC...planned capacity of the Petitioners' wind and solar generation projects to the...

2012-10-10

21

Solar wind stagnation near comets  

Microsoft Academic Search

The nature of the solar wind flow near comets is examined analytically in this paper. In particular, typical values for the stagnation pressure and magnetic barrier strength are estimated, taking into account magnetic field line tension and change-exchange cooling of the mass-loaded solar wind. A knowledge of the strength of the magnetic barrier is required in order to determine the

A. A. Galeev; T. E. Cravens; T. I. Gombosi

1985-01-01

22

New Horizons Solar Wind Around Pluto (SWAP) Solar Wind Measurements  

NASA Astrophysics Data System (ADS)

The Solar Wind Around Pluto (SWAP) instrument on the New Horizons (NH) spacecraft has measured the solar wind from 5 to 27 AU. Optimization of the SWAP instrument design for the NH Pluto/Charon flyby mission requirements, adds complexity to the analysis of the measurements. In this presentation we describe key aspects of the instrument calibration necessary to obtain accurate solar wind parameters. In the SWAP instrument, ions from the full field-of-view (10 by 276°) are focused onto a pair of coincidence Channel Electron Multipliers (CEMs). The instrument sensitivity varies across the FOV, and the energy and range of energies observed depends on the angle at which the ions enter. We developed a simple analytic expression for the count rates, which neglects such angle dependences, but runs quickly. Recently we developed a more comprehensive model that runs slower, but reproduces the spin variation due to the angle dependences in the instrument response. In the recent NH-SWAP observations, there are long intervals of very steady solar wind speeds. This is consistent with many solar wind structures becoming worn down with increasing distance as different speed parcels dynamically interact. In the steady solar wind speed intervals, we will examine the temperature to assess if the temperature shows signs of prior dynamic interaction between fast and slow wind streams as the wind parcels traversed distances greater than 20 AU. It could be that the temperature shows a regular alternating pattern of hotter and cooler wind. Although much of the recent solar wind observations are steady, at ~23.8 AU the SWAP measurements indicate a clear rarefaction with a decreasing speed profile followed by an increase in the speed forming a wave or shock. We compare this wave/shock event to the neighboring steady solar wind speed intervals.

Elliott, H. A.; McComas, D. J.; Mukherjee, J.; Valek, P. W.; Livadiotis, G.; Delamere, P. A.; Bagenal, F.; Nicolaou, G.

2013-12-01

23

The Solar Wind Helium Abundance: Variation with Wind Speed and the Solar Cycle  

E-print Network

The Solar Wind Helium Abundance: Variation with Wind Speed and the Solar Cycle Matthias R. Aellig Alamos National Lab., Los Alamos, NM 87545 Abstract We investigate the helium abundance in the solar wind a clear dependency of the He/H ratio in the solar wind on the solar cycle. In the slow solar wind

Richardson, John

24

Forecasting Solar Wind Speeds  

E-print Network

By explicitly taking into account effects of Alfven waves, I derive from a simple energetics argument a fundamental relation which predicts solar wind (SW) speeds in the vicinity of the earth from physical properties on the sun. Kojima et al. recently found from their observations that a ratio of surface magnetic field strength to an expansion factor of open magnetic flux tubes is a good indicator of the SW speed. I show by using the derived relation that this nice correlation is an evidence of the Alfven wave which accelerates SW in expanding flux tubes. The observations further require that fluctuation amplitudes of magnetic field lines at the surface should be almost universal in different coronal holes, which needs to be tested by future observations.

Takeru K. Suzuki

2006-02-03

25

Wind and Solar Curtailment: Preprint  

SciTech Connect

High penetrations of wind and solar generation on power systems are resulting in increasing curtailment. Wind and solar integration studies predict increased curtailment as penetration levels grow. This paper examines experiences with curtailment on bulk power systems internationally. It discusses how much curtailment is occurring, how it is occurring, why it is occurring, and what is being done to reduce curtailment. This summary is produced as part of the International Energy Agency Wind Task 25 on Design and Operation of Power Systems with Large Amounts of Wind Power.

Lew, D.; Bird, L.; Milligan, M.; Speer, B.; Wang, X.; Carlini, E. M.; Estanqueiro, A.; Flynn, D.; Gomez-Lazaro, E.; Menemenlis, N.; Orths, A.; Pineda, I.; Smith, J. C.; Soder, L.; Sorensen, P.; Altiparmakis, A.; Yoh, Y.

2013-09-01

26

Solar wind acceleration in the solar corona  

NASA Technical Reports Server (NTRS)

The intensity ratio of the O VI doublet in the extended area is analyzed. The O VI intensity data were obtained with the ultraviolet coronagraph spectrometer (UVCS) during the SOHO campaign 'whole sun month'. The long term observations above the north pole of the sun were used for the polar coronal data. Using these measurements, the solar wind outflow velocity in the extended corona was determined. The 100 km/s level is running along the streamer borders. The acceleration of the solar wind is found to be high in regions between streamers. In the central part of streamers, the outflow velocity of the coronal plasma remains below 100 km/s at least within 3.8 solar radii. The regions at the north and south poles, characterized by a more rapid acceleration of the solar wind, correspond to regions where the UVCS observes enhanced O VI line broadenings.

Giordano, S.; Antonucci, E.; Benna, C.; Kohl, J. L.; Noci, G.; Michels, J.; Fineschi, S.

1997-01-01

27

Highly Alfvenic Slow Solar Wind  

NASA Technical Reports Server (NTRS)

It is commonly thought that fast solar wind tends to be highly Alfvenic, with strong correlations between velocity and magnetic fluctuations, but examples have been known for over 20 years in which slow wind is both Alfvenic and has many other properties more typically expected of fast solar wind. This paper will present a search for examples of such flows from more recent data, and will begin to characterize the general characteristics of them. A very preliminary search suggests that such intervals are more common in the rising phase of the solar cycle. These intervals are important for providing constraints on models of solar wind acceleration, and in particular the role waves might or might not play in that process.

Roberts, D. Aaron

2010-01-01

28

STATIONARITY IN SOLAR WIND FLOWS  

SciTech Connect

By using single-point measurements in space physics it is possible to study a phenomenon only as a function of time. This means that we cannot have direct access to information about spatial variations of a measured quantity. However, the investigation of the properties of turbulence and of related phenomena in the solar wind widely makes use of an approximation frequently adopted in hydrodynamics under certain conditions, the so-called Taylor hypothesis; indeed, the solar wind flow has a bulk velocity along the radial direction which is much higher than the velocity of a single turbulent eddy embedded in the main flow. This implies that the time of evolution of the turbulent features is longer than the transit time of the flow through the spacecraft position, so that the turbulent field can be considered frozen into the solar wind flow. This assumption allows one to easily associate time variations with spatial variations and stationarity to homogeneity. We have investigated, applying criteria for weak stationarity to Ulysses magnetic field data in different solar wind regimes, at which timescale and under which conditions the hypothesis of stationarity, and then of homogeneity, of turbulence in the solar wind is well justified. We extend the conclusions of previous studies by Matthaeus and Goldstein to different parameter ranges in the solar wind. We conclude that the stationarity assumption in the inertial range of turbulence on timescales of 10 minutes to 1 day is reasonably satisfied in fast and uniform solar wind flows, but that in mixed, interacting fast, and slow solar wind streams the assumption is frequently only marginally valid.

Perri, S.; Balogh, A., E-mail: silvia.perri@issibern.c, E-mail: a.balogh@imperial.ac.u [International Space Science Institute, Hallerstrasse 6, Bern CH-3012 (Switzerland)

2010-05-01

29

Solar cycle variations in the solar wind  

NASA Technical Reports Server (NTRS)

The solar cycle variations of various solar wind parameters are reviewed. It is shown that there is a gradual decrease in the duration of high-speed streams from the declining phase of solar cycle 20 through the ascending phase of cycle 21 and a corresponding decrease in the annual average of the proton speed toward solar maximum. Beta, the ratio of the proton thermal pressure to magnetic pressure, undergoes a significant solar cycle variation, as expected from the variation in the IMF. Individual hourly averages of beta often exceed unity with 20 cases exceeding 10 and one case as high as 25. The Alfven Mach number shows a solar cycle variation similar to beta, lower aboard solar maximum. High-speed streams can be seen clearly in epsilon and the y component of the interplanetary magnetic field.

Freeman, John W.; Lopez, Ramon E.

1986-01-01

30

Wind in the Solar System  

ERIC Educational Resources Information Center

As an astronomy instructor I am always looking for commonly experienced Earthly phenomena to help my students and me understand and appreciate similar occurrences elsewhere in the solar system. Recently I wrote short "TPT" articles on frost and precipitation. The present article is on winds in the solar system. A windy day or storm might motivate…

McIntosh, Gordon

2010-01-01

31

Solar wind interaction with Mars.  

NASA Astrophysics Data System (ADS)

The existence of an intrinsic magnetic field at Mars is still a subject of debate. The ionospheric thermal pressure above 300 km is insufficient by itself to withstand the solar wind dynamic pressure, suggesting the presence of a magnetic field in the ionosphere of Mars which can either be a weak intrinsic magnetic field or an induced magnetic field driven by the solar wind interaction with Mars. The photodynamical model of Mahajan and Mayr (1990) for the case of a magnetic field induced by the solar wind plus ion loss via horizontal convection has been studied. It has been found that the induced magnetic field does not affect or alter the photodynamical nature of the ionosphere of Mars.

Mohan, M.

1997-08-01

32

The Genesis Solar Wind Concentrator  

Microsoft Academic Search

The primary goal of the Genesis Mission is to collect solar wind ions and, from their analysis, establish key isotopic ratios\\u000a that will help constrain models of solar nebula formation and evolution. The ratios of primary interest include 17O\\/16O and 18O\\/16O to ±0.1%, 15N\\/14N to ±1%, and the Li, Be, and B elemental and isotopic abundances. The required accuracies in

Jane E. Nordholt; Roger C. Wiens; Rudy A. Abeyta; Juan R. Baldonado; Donald S. Burnett; Patrick Casey; Daniel T. Everett; Joseph Kroesche; Walter L. Lockhart; Paul MacNeal; David J. McComas; Donald E. Mietz; Ronald W. Moses; Marcia Neugebauer; Jane Poths; Daniel B. Reisenfeld; Steven A. Storms; Carlos Urdiales

2003-01-01

33

Solar wind electron density and temperature over solar cycle 23: Thermal noise measurements on Wind  

E-print Network

Solar wind electron density and temperature over solar cycle 23: Thermal noise measurements on Wind; received in revised form 6 April 2005; accepted 25 April 2005 Abstract We present the solar wind plasma parameters obtained from the Wind spacecraft during more than nine years, encompassing almost the whole solar

California at Berkeley, University of

34

Turbulence of the Solar Wind Studies of the Solar Wind Using the ACE and Helios Spacecraft  

E-print Network

Turbulence of the Solar Wind Studies of the Solar Wind Using the ACE and Helios Spacecraft Bejamin;Abstract The solar wind is a supersonic ow of plasma emanating from the sun and traveling through the interplanetary medium to the outermost reaches of the heliosphere. The solar wind experiences in situ

35

Solar and Wind Technologies for Hydrogen Production: Report to Congress Solar and Wind Technologies  

E-print Network

.........................5 1.4 Potential Capacity for Hydrogen Production from Conventional Electrolysis Using Wind and SolarSolar and Wind Technologies for Hydrogen Production: Report to Congress Solar and Wind Technologies For Hydrogen Production Report to Congress December 2005 (ESECS EE-3060) #12;Solar and Wind Technologies

36

Compressibility of solar wind Bogdan A. Hnat  

E-print Network

Compressibility of solar wind turbulence Bogdan A. Hnat Centre for Fusion, Space and Astrophysics Collaborators: S. C. Chapman, K. Kiyani and G. Rowlands #12;Introduction Solar wind modeled by incompressible MHD (supported by observations in the fast solar wind [1]) Generation of compressive modes from

Sengun, Mehmet Haluk

37

The Heating & Acceleration of the Solar Wind  

E-print Network

The Heating & Acceleration of the Solar Wind Eliot Quataert (UC Berkeley) Collaborators: Steve #12;Background · Heating required to accelerate the solar wind · Early models invoked e- conduction requires oppositely directed waves · solar wind: inward propagating waves generated by reflection of long

Wurtele, Jonathan

38

THE SOLAR WIND PLASMA Dr. Joe Borovsky  

E-print Network

THE SOLAR WIND PLASMA Dr. Joe Borovsky Los Alamos National Laboratory and University of Michigan Wednesday, 19 October 2011 4:00 pm Room 1005 EECS Building Abstract The solar wind is a large bumps and wiggles at all timescales. A difficulty in characterizing the solar wind from the time

Shyy, Wei

39

Coronal holes as sources of solar wind  

Microsoft Academic Search

We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial

J. T. Nolte; A. S. Krieger; A. F. Timothy; R. E. Gold; E. C. Roelof; G. Vaiana; A. J. Lazarus; J. D. Sullivan; P. S. McIntosh

1976-01-01

40

Solar wind electrons: Parametric constraints  

SciTech Connect

Solar wind electrons are often observed to consist of two distinguishable components, a thermal, more dense core and a suprathermal, less dense halo. In this core/halo model linear Vlasov theory for the whistler heat flux instability predicts dimensionless heat flux thresholds which decrease as the electron core beta, {tilde {beta}}{sub {parallel}c}, increases. It has been proposed that this theoretical threshold corresponds to an observable upper bound on the electron heat flux. Linear theory also predicts that there is a critical value of {tilde {beta}}{sub {parallel}c} below which the whistler heat flux instability does not have appreciable growth in the solar wind; there is another suggestion that this corresponds to an observable lower bound on {tilde {beta}}{sub {parallel}c}. These two proposals are examined by comparison of linear theory and data from the initial in-ecliptic phase of the Ulysses mission. The instability threshold does provide a statistical constraint on observed solar wind heat fluxes, and the critical {tilde {beta}}{sub {parallel}c} of theory is not inconsistent with a statistical lower bound on the observations of that parameter. {copyright} 1999 American Geophysical Union

Gary, S.P.; Neagu, E.; Skoug, R.M. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Goldstein, B.E. [Jet Propulsion Laboratory, Pasadena, California (United States)] [Jet Propulsion Laboratory, Pasadena, California (United States)

1999-09-01

41

MAGNETOHYDRODYNAMIC SIMULATIONS OF THE SOLAR CORONA AND SOLAR WIND USING A BOUNDARY TREATMENT TO LIMIT SOLAR WIND MASS FLUX  

E-print Network

MAGNETOHYDRODYNAMIC SIMULATIONS OF THE SOLAR CORONA AND SOLAR WIND USING A BOUNDARY TREATMENT TO LIMIT SOLAR WIND MASS FLUX Keiji Hayashi W. W. Hansen Experimental Physics Laboratory, Stanford ABSTRACT Magnetohydrodynamic simulations of the solar corona and solar wind are sensitive to conditions

California at Berkeley, University of

42

Evolution of Solar Wind Heavy Ions over the Solar Cycle  

NASA Astrophysics Data System (ADS)

Solar wind composition has been shown to effectively discriminate between different types of solar wind, including slow, fast and ICME related wind. The composition reflects the properties of the source regions of the wind in the corona and their evolution. We present the systematic and comprehensive analysis of the ionic and elemental composition observed on ACE over solar cycle 23 from 2000 until 2010. During this period, the Sun evolved through solar maximum to solar minimum. We find significantly lower C, O, and Fe charge states as well as a 50% decrease in heavy ion abundances (He, C, O, Si, Fe) relative to H during this transition towards solar minimum. We also examined the FIP bias. We consider the implications of these findings for solar wind models and for identification of the fast and slow wind.

Lepri, S. T.; Landi, E.; Zurbuchen, T. H.

2014-05-01

43

Source regions of the solar wind  

NASA Technical Reports Server (NTRS)

Using Skylab XUV data, we examine some properties of the source regions of the solar wind. In particular, we discuss the physical nature of polar plumes and their relationship to the polar wind, the nature of the source regions of the slow solar wind, and the relationship between abundance anomalies (the FIP effect) determined from the Skylab data and the sources of fast and slow wind.

Wang, Y.-M.; Sheeley, N. R., Jr.

1995-01-01

44

The Solar Wind Ion Composition Spectrometer  

NASA Technical Reports Server (NTRS)

The Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses is designed to determine uniquely the elemental and ionic-charge composition, and the temperatures and mean speeds of all major solar-wind ions, from H through Fe, at solar wind speeds ranging from 175 km/s (protons) to 1280 km/s (Fe(8+)). The instrument, which covers an energy per charge range from 0.16 to 59.6 keV/e in about 13 min, combines an electrostatic analyzer with postacceleration, followed by a time-of-flight and energy measurement. The measurements made by SWICS will have an impact on many areas of solar and heliospheric physics, in particular providing essential and unique information on: (1) conditions and processes in the region of the corona where the solar wind is accelerated; (2) the location of the source regions of the solar wind in the corona; (3) coronal heating processes; (4) the extent and causes of variations in the composition of the solar atmosphere; (5) plasma processes in the solar wind; (6) the acceleration of energetic particles in the solar wind; (7) the thermalization and acceleration of interstellar ions in the solar wind, and their composition; and (8) the composition, charge states, and behavior of the plasma in various regions of the Jovian magnetosphere.

Gloeckler, G.; Geiss, J.; Balsiger, H.; Bedini, P.; Cain, J. C.; Fisher, J.; Fisk, L. A.; Galvin, A. B.; Gliem, F.; Hamilton, D. C.

1992-01-01

45

Wind loading on solar collectors  

SciTech Connect

The present design methodology for the determination of wind loading on the various solar collectors has been reviewed and assessed. The total force coefficients of flat plates of aspect ratios 1.0 and 3.0, respectively, at various angles of attack obtained by using the guidelines of the ANSI A58.1-1982, have been compared with those obtained by using the methodology of the ASCE Task Committee, 1961, and the experimental results of the full-scale test of heliostats by Peglow. The turbulent energy spectra, currently employed in the building code, are compared with those of Kaimal et al., Lumley, and Ponofsky for wind velocities of 20.0 m/s and 40.24 m/s at an elevation of 9.15 m. The longitudinal spectra of the building code overestimates the Kaimal spectra in the frequency range of 0.007 Hz to 0.08 Hz and underestimates beyond the frequency of 0.08 Hz. The peak angles of attack, on the heliostat, stowed in horizontal position, due to turbulent vertical and lateral components of wind velocity, have been estimated by using Daniel's methodology for three wind velocities and compared with the value suggested by the code. The experimental results of a simple test in the laboratory indicate the feasibility of decreasing the drag forces of the flat plate by reducing the solidity ratio.

Bhaduri, S.; Murphy, L.M.

1985-06-01

46

Composition of quasi-stationary solar wind flows from Ulysses\\/Solar Wind Ion Composition Spectrometer  

Microsoft Academic Search

Using improved, self-consistent analysis techniques, we determine the average solar wind charge state and elemental composition of nearly 40 ion species of He, C, N, O, Ne, Mg, Si, S, and Fe observed with the Solar Wind Ion Composition Spectrometer on Ulysses. We compare results obtained during selected time periods, including both slow solar wind and fast streams, concentrating on

R. von Steiger; N. A. Schwadron; L. A. Fisk; J. Geiss; G. Gloeckler; S. Hefti; B. Wilken; R. F. Wimmer-Schweingruber; T. H. Zurbuchen

2000-01-01

47

Solar wind thermal electron distributions  

SciTech Connect

Solar wind thermal electron distributions exhibit distinctive trends which suggest Coulomb collisions and geometric expansion in the interplanetary magnetic field play keys roles in electron transport. We introduce a simple numerical model incorporating these mechanisms, discuss the ramifications of model results, and assess the validity of the model in terms of ISEE-3 and Ulysses observations. Although the model duplicates the shape of the electron distributions, and explains certain other observational features, observed gradients in total electron temperature indicate the importance of additional heating mechanisms. 5 refs., 7 figs.

Phillips, J.L.; Gosling, J.T.

1991-12-01

48

Solar Wind's Effect on Earth  

NSDL National Science Digital Library

The Sun produces 'solar wind', a continuous flow of charged particles that can affect us on Earth. It may also release huge storms of charged particles, called coronal mass ejections, that can disrupt communications, navigation systems, and satellites; and cause power outages, such as the extensive Canadian blackout in 1989. This video segment introduces viewers to coronal mass ejections, their effects on Earth's magnetosphere and atmosphere, and their potentially damaging effects on satellites, power grids, and other human infrastructure. The segment is four minutes forty-four seconds in length.

2011-05-05

49

Solar Wind's Effect on Earth  

NSDL National Science Digital Library

The Sun produces 'solar wind', a continuous flow of charged particles that can affect us on Earth. It may also release huge storms of charged particles, called coronal mass ejections, that can disrupt communications, navigation systems, and satellites; and cause power outages, such as the extensive Canadian blackout in 1989. This video segment introduces viewers to coronal mass ejections, their effects on Earth's magnetosphere and atmosphere, and their potentially damaging effects on satellites, power grids, and other human infrastructure. The segment is four minutes forty-four seconds in length.

50

Effects of the Dayside Ionospheric Conductance on Solar Wind-Magnetosphere-Ionosphere Coupling  

NASA Astrophysics Data System (ADS)

In the present study we seek to observationally address the role of ionospheric conductance in the solar wind-magnetosphere coupling in terms of global field-aligned currents (FACs). Solar EUV irradiance changes during a solar cycle, and so does its contribution to the ionospheric conductance. We statistically examine how, for fixed ranges of external driver, the intensities of the R1 and R2 currents and their demarcation latitude depend on solar activity (F10.7). An emphasis is placed on night-side FACs in the dark hemisphere. The result shows that under fixed external conditions, the night-side FACs are more intense for higher solar activity irrespective of their polarities or local time. It is also found that the overall FAC system, therefore the auroral oval, moves equatorward as the solar activity increases. For both current intensity and latitude, the dependence on solar activity is more sensitive for smaller values of F10.7 and it becomes more gradual with increasing F10.7. The intensities of dayside FACs reveal similar F10.7 dependence as expected from the enhancement of the local ionospheric conductance. Interestingly, they also move equatorward with increasing solar activity. We suggest that as the dayside R1 current becomes more intense with increasing solar activity, the magnetosphere shrinks on the day side and expands on the night side. This configurational change of the magnetosphere is considered to affect the energy transport from the solar wind to the magnetosphere, although the details still remain to be understood. We conclude that the ionospheric conductance actively affects the solar wind-magnetosphere-ionosphere coupling.

Ohtani, S.; Wing, S.; Merkin, V. G.; Higuchi, T.

2013-12-01

51

The global nature of solar cycle variations of the solar wind dynamic pressure  

E-print Network

1 The global nature of solar cycle variations of the solar wind dynamic pressure John Richardson: SOLAR WIND DYNAMIC PRESSURE #12;2 Abstract. The solar wind dynamic pressure measured near the ecliptic-scale variation of the solar wind dynamic pressure is the same at all latitudes. Thus the solar wind source varies

Richardson, John

52

Solar wind tans young asteroids  

NASA Astrophysics Data System (ADS)

A new study published in Nature this week reveals that asteroid surfaces age and redden much faster than previously thought -- in less than a million years, the blink of an eye for an asteroid. This study has finally confirmed that the solar wind is the most likely cause of very rapid space weathering in asteroids. This fundamental result will help astronomers relate the appearance of an asteroid to its actual history and identify any after effects of a catastrophic impact with another asteroid. ESO PR Photo 16a/09 Young Asteroids Look Old "Asteroids seem to get a ‘sun tan' very quickly," says lead author Pierre Vernazza. "But not, as for people, from an overdose of the Sun's ultraviolet radiation, but from the effects of its powerful wind." It has long been known that asteroid surfaces alter in appearance with time -- the observed asteroids are much redder than the interior of meteorites found on Earth [1] -- but the actual processes of this "space weathering" and the timescales involved were controversial. Thanks to observations of different families of asteroids [2] using ESO's New Technology Telescope at La Silla and the Very Large Telescope at Paranal, as well as telescopes in Spain and Hawaii, Vernazza's team have now solved the puzzle. When two asteroids collide, they create a family of fragments with "fresh" surfaces. The astronomers found that these newly exposed surfaces are quickly altered and change colour in less than a million years -- a very short time compared to the age of the Solar System. "The charged, fast moving particles in the solar wind damage the asteroid's surface at an amazing rate [3]", says Vernazza. Unlike human skin, which is damaged and aged by repeated overexposure to sunlight, it is, perhaps rather surprisingly, the first moments of exposure (on the timescale considered) -- the first million years -- that causes most of the aging in asteroids. By studying different families of asteroids, the team has also shown that an asteroid's surface composition is an important factor in how red its surface can become. After the first million years, the surface "tans" much more slowly. At that stage, the colour depends more on composition than on age. Moreover, the observations reveal that collisions cannot be the main mechanism behind the high proportion of "fresh" surfaces seen among near-Earth asteroids. Instead, these "fresh-looking" surfaces may be the results of planetary encounters, where the tug of a planet has "shaken" the asteroid, exposing unaltered material. Thanks to these results, astronomers will now be able to understand better how the surface of an asteroid -- which often is the only thing we can observe -- reflects its history. More information This result was presented in a paper published this week in the journal Nature, "Solar wind as the origin of rapid reddening of asteroid surfaces", by P. Vernazza et al. The team is composed of Pierre Vernazza (ESA), Richard Binzel (MIT, Cambridge, USA), Alessandro Rossi (ISTI-CNR, Pisa, Italy), Marcello Fulchignoni (Paris Observatory, France), and Mirel Birlan (IMCCE, CNRS-8028, Paris Observatory, France). A PDF file can be downloaded here. Notes [1] Meteorites are small fragments of asteroids that fall on Earth. While a meteorite enters the Earth's atmosphere its surface can melt and be partially charred by the intense heat. Nevertheless, the meteorite interior remains unaffected, and can be studied in a laboratory, providing a wealth of information on the nature and composition of asteroids. [2] An asteroid family is a group of asteroids that are on similar orbits around the Sun. The members of a given family are believed to be the fragments of a larger asteroid that was destroyed during a collision. [3] The surface of an asteroid is affected by the highly energetic particles forming the solar wind. These particles partially destroy the molecules and crystals on the surface, re-arranging them in other combinations. Over time, these changes

2009-04-01

53

Ulysses' return to the slow solar wind  

Microsoft Academic Search

After ten long years of wandering the uncharted seas, Ulysses returned to his home port of Ithaca. Similarly, after its unprecedented five year odyssey through the previously uncharted regions over the poles of the Sun, the Ulysses spacecraft has returned to the slow, variable solar wind which dominates observations near the ecliptic plane. Solar wind plasma and magnetic field observations

D. J. McComas; S. J. Bame; B. L. Barraclough; W. C. Feldman; H. O. Funsten; J. T. Gosling; P. Riley; R. Skoug; A. Balogh; R. Forsyth; B. E. Goldstein; M. Neugebauer

1998-01-01

54

Sources of solar wind over the solar activity cycle  

PubMed Central

Fast solar wind has been recognized, about 40 years ago, to originate in polar coronal holes (CHs), that, since then, have been identified with sources of recurrent high speed wind streams. As of today, however, there is no general consensus about whether there are, within CHs, preferential locations where the solar wind is accelerated. Knowledge of slow wind sources is far from complete as well. Slow wind observed in situ can be traced back to its solar source by backward extrapolation of magnetic fields whose field lines are streamlines of the outflowing plasma. However, this technique often has not the necessary precision for an indisputable identification of the region where wind originates. As the Sun progresses through its activity cycle, different wind sources prevail and contribute to filling the heliosphere. Our present knowledge of different wind sources is here summarized. Also, a Section addresses the problem of wind acceleration in the low corona, as inferred from an analysis of UV data, and illustrates changes between fast and slow wind profiles and possible signatures of changes along the solar cycle. A brief reference to recent work about the deep roots of solar wind and their changes over different solar cycles concludes the review.

Poletto, Giannina

2012-01-01

55

Solar Wind Interaction with Venus  

NASA Astrophysics Data System (ADS)

Venus Express, which was inserted into orbit in mid-2006, has added significantly to the knowledge gained from Pioneer Venus from 1978 to 1992. This observational database interpreted in terms of modern multi-fluid codes and hybrid simulations has deepened our understanding of Earth's very different twin sister planet. Furthermore, the very different orbits of VEX and PVO has allowed the more complete mapping of the volume of space around the planet. Now the bow shock has been probed over its full surface, the ionosphere mapped everywhere, and the tail studied from the ionosphere to 12 Venus radii. Some unexpected discoveries have been made. The exospheric hydrogen at Venus, unlike that at Mars,does not produce ion-cyclotron waves, perhapsbecause the stronger gravity of Venus produces a smaller geocorona. The solar wind interaction drapes the magnetic field around the planet, and a strong layer of magnetic field builds up at low altitudes. While the layer does not appear to penetrate into the dayside atmosphere (perhaps diffusing only slowly through the low atmosphere), it does appear to dip into the atmosphere at night. Surprisingly, over the poles, this layer is most strongly seen when the IMF BY component has a positive Y-component in Venus- Solar-Orbital coordinates. Multi-fluid simulations show that this result is consistent with the pressure of significant ion densities of ions with quite different mass which causes magnetic polarity control of the ion flow over the terminators. Reconnection is found in the tail close to the planet, and the structure of the outer tail found by PVO is confirmed to exist in the inner tail by VEX. When combined, the VEX and PVO Data provide a very comprehensive picture of the physics of the solar wind interaction with the ionosphere of Venus.

Russell, C. T.; Luhmann, J. G.; Ma, Y. J.; Villarreal, M. N.; Zhang, T. L.

2014-04-01

56

Expansion effects on solar wind hybrid simulations  

SciTech Connect

Ion kinetic simulations of the solar wind using hybrid codes can model local wave input, heating and instabilities, but generally do not include long term evolution effects in the expanding solar wind. We further develop the expanding box model used in earlier studies to include the mirror force effects and study their role in the evolution of the proton distribution functions in the outer corona and inner heliosphere. The mirror force, significant in the acceleration region of the solar wind, is required for consistency with the conservation of magnetic moment of particles in the expanding wind. We present preliminary results from the modified 1D expanding box hybrid (EBHM) simulations.

Parashar, Tulasi N.; Velli, Marco; Goldstein, Bruce E. [NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2013-06-13

57

Ion release experiments in the solar wind  

NASA Astrophysics Data System (ADS)

In a new departure in experimental Space Plasma Physics, lithium and barium plasmas were injected into the solar wind approximately 110,000 kms above the earth's surface. The effects, monitored in-situ by two spacecraft of the AMPTE (Active Magnetospheric Particle Tracer Explorers) mission, included the formation of diamagnetic cavities, a slowing down locally of the solar wind, generation of plasma waves and heating of solar-wind electrons. These comet-like interactions between the solar wind and obstacles presented by the injected plasmas are discussed and compared with the effect of the natural obstacle of the earth's magnetosphere first encountered by the solar wind at the bow shock. Particular reference is made to the 'artificial comet' created by a barium-ion release on 27 December 1984.

Bryant, D. A.

1985-12-01

58

SOLAR AND WIND ELECTRICITY IN AUSTRALIA  

Microsoft Academic Search

This paper examines the renewable generation of electricity in Australia from photovoltaics (PV), solar thermal electricity (STE) and wind. PV, STE and wind have immense resources and small environmental impacts even when deployed on very large scales. They are the only fully sustainable technologies able to completely replace fossil and nuclear electricity generation during this century. Wind energy is now

Andrew Blakers

59

The quiescent corona and slow solar wind  

NASA Technical Reports Server (NTRS)

The observations of the ultraviolet coronagraph spectrometer (UVCS), operating onboard the Solar and Heliospheric Observatory (SOHO) spacecraft, are discussed. The purpose of the UVCS is the study of the quiescent coronal streamer and the slow solar wind. The observations started in January 1996. Polarized radiance data in the visible continuum were obtained. Some characteristics of the coronal streamer from the UVCS recorded data are discussed. A model for the source of the slow solar wind in the inner corona is proposed.

Noci, G.; Kohl, J. L.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Fineschi, S.; Gardner, L. D.; Korendyke, C. M.; Nicolosi, P.; Romoli, M.; Spadaro, D.; Maccari, L.; Raymond, J. C.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Giordano, S.; Michels, J.; Modigliani, A.; Naletto, G.

1997-01-01

60

Contact discontinuities in solar wind  

NASA Astrophysics Data System (ADS)

Contact discontinuities (CD) are discontinuities that have magnetic fields linked between two sides but no plasma flows across its surface. Due to the lack of demonstrations of CD in observation, their stable existence is still under debate. Contact discontinuities are not expected to be observed in the solar wind because of the rapid diffusion of plasma along the magnetic fields across their surfaces. Nevertheless, hybrid simulations had demonstrated that stable CD can exist with a finite ratio of the electron temperature to ion temperature; but full particle simulations predicted that CD cannot persist in collisionless plasma as a result of electron thermal transport. On the other hand, electrostatic Vlasov simulations show that the structure of a contact discontinuity can be stable under a condition of out-of-phase profiles of the ion and electron temperatures. According to theoretical considerations, CD can survive in magnetodynamics plasma with constant total thermal pressure across the surface of CD, in ion-electron two-fluid plasma further with out-of-phase variations of the ion and electron thermal pressures, and in Vlasov theory with additionally out-of-phase variations of the ion and electron temperatures. In this study, we define the criteria for the selection of a CD event in observation, in accord with the jump conditions. CD events in the solar wind, with a constant total thermal pressure but different performances on the variations of thermal pressure and temperatures of ions and electrons will be demonstrated. The practical behavior of ion and electron temperature will be discussed in follow.

Hsieh, Wen-Chieh; Shue, Jih-Hong; Chao, Jih-Kwin; Tsai, Tsung-Che; Nemecek, Zdenek; Safrankova, Jana; Kruparova, Oksana

2014-05-01

61

Solar energy tracking structure incorporating wind spoilers  

Microsoft Academic Search

This patent describes a solar energy tracking assembly. The assembly producing reduced torque loading forces due to wind on the rotating portion of the tracking assembly. The solar energy tracking assembly comprised of: a fixed position base having one end securely fixed to the ground and having the second end supporting the remaining tracking assembly components; solar energy collecting means

M. W. Frohardt; K. H. Hartz; P. C. Hardee

1989-01-01

62

Lognormal distributions and spectra of solar wind plasma fluctuations: Wind 19951998  

E-print Network

Lognormal distributions and spectra of solar wind plasma fluctuations: Wind 1995­1998 L. F. Burlaga with large tails. There remains a need for dynamical models of the solar wind that incorporate and describe both deterministic and statistical properties of the solar wind. 1. Introduction The solar wind

Richardson, John

63

Global Network of Slow Solar Wind  

NASA Technical Reports Server (NTRS)

The streamer belt region surrounding the heliospheric current sheet (HCS) is generally treated as the primary or sole source of the slow solar wind. Synoptic maps of solar wind speed predicted by the Wang-Sheeley-Arge model during selected periods of solar cycle 23, however, show many areas of slow wind displaced from the streamer belt. These areas commonly have the form of an arc that is connected to the streamer belt at both ends. The arcs mark the boundaries between fields emanating from different coronal holes of the same polarity and thus trace the paths of belts of pseudostreamers, i.e., unipolar streamers that form over double arcades and lack current sheets. The arc pattern is consistent with the predicted topological mapping of the narrow open corridor or singular separator line that must connect the holes and, thus, consistent with the separatrix-web model of the slow solar wind. Near solar maximum, pseudostreamer belts stray far from the HCS-associated streamer belt and, together with it, form a global-wide web of slow wind. Recognition of pseudostreamer belts as prominent sources of slow wind provides a new template for understanding solar wind stream structure, especially near solar maximum.

Crooker, N. U.; Antiochos, S. K.; Zhao, X.; Neugebauer, M.

2012-01-01

64

DSCOVR High Time Resolution Solar Wind Measurements  

NASA Technical Reports Server (NTRS)

The Deep Space Climate Observatory (DSCOVR), previously known as Triana, spacecraft is expected to be launched in late 2014. It will carry a fluxgate magnetometer, Faraday Cup solar wind detector and a top-hat electron electrostatic analyzer. The Faraday Cup will provide an unprecedented 10 vectors/sec time resolution measurement of the solar wind proton and alpha reduced distribution functions. Coupled with the 40 vector/sec vector magnetometer measurements, the identification of specific wave modes in the solar wind will be possible for the first time. The science objectives and data products of the mission will be discussed.

Szabo, Adam

2012-01-01

65

Anisotropic turbulence in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind turbulence has been viewed traditionally as composed of parallel propagating ('slab' fluctuations) or otherwise as isotropic turbulence. A variety of recent investigations, reviewed here, indicate that the spectrum may contain a significant admixture of two dimensional fluctuations, having variations mainly perpendicular to the local magnetic field. These indications come from simulations, from the theory of nearly incompressible MHD, from cosmic ray transport studies and from transport theory for solar wind turbulence, as well as from interpretations of direct observations. Thus, solar wind turbulence may be more like bundles of spaghetti than like parallel phase fronts.

Matthaeus, W. H.; Bieber, J. W.; Zank, G. P.

1995-01-01

66

Alfvén wave interactions in the solar wind  

NASA Astrophysics Data System (ADS)

Alfvén wave mixing (interaction) equations used in locally incompressible turbulence transport equations in the solar wind are analyzed from the perspective of linear wave theory. The connection between the wave mixing equations and non-WKB Alfven wave driven wind theories are delineated. We discuss the physical wave energy equation and the canonical wave energy equation for non-WKB Alfven waves and the WKB limit. Variational principles and conservation laws for the linear wave mixing equations for the Heinemann and Olbert non-WKB wind model are obtained. The connection with wave mixing equations used in locally incompressible turbulence transport in the solar wind are discussed.

Webb, G. M.; McKenzie, J. F.; Hu, Q.; le Roux, J. A.; Zank, G. P.

2012-11-01

67

Global Network of Slow Solar Wind N. U. Crooker1  

E-print Network

Global Network of Slow Solar Wind N. U. Crooker1 Center for Space Physics, Boston University of the slow solar wind. Synoptic maps of solar wind speed predicted by the Wang-Sheeley-Arge model during selected periods of solar cycle 23, however, show many areas of slow wind displaced from the streamer belt

Zhao, Xuepu

68

The Solar Wind and Its Interaction with the Interstellar Medium  

E-print Network

The Solar Wind and Its Interaction with the Interstellar Medium John D. Richardson Abstract The solar wind is a magnetized plasma of ions and electrons which flows outward from the Sun. This chapter begins with a brief history of the discovery of the solar wind. Solar wind properties at 1 AU

Richardson, John

69

Prospects for future solar-wind missions  

NASA Astrophysics Data System (ADS)

Possible activities and future goals for solar wind research in the post Soho era are discussed. Two major enterprises which will open up important fields in the future study of the Sun are addressed. The first deals with in situ study of the solar corona, a region that has not been accessible for direct study in the past. This exploratory work will include the coronal heating and the acceleration of the solar wind much closer to its origin and the determination of the charge states of a large number of ions as a diagnostic tool for fractionation processes in these regions. The second major goal will be the setting up of a baseline for the isotopic composition in the solar system by studying a sample from the Sun in detail. These studies will be complemented by a direct comparison with extra solar samples of interstellar pick up ions, which become accessible with the same instrumentation as is necessary for the detailed investigation of the solar wind's isotopic composition. In order to achieve these goals, advanced composition experiments are developed to investigate the solar wind with enhanced mass resolution, considerably increased geometrical factor, and improved time resolution. The placing of sophisticated mass/charge spectrometers, with the ability to investigate both charge and velocity distributions with enhanced time resolution, in the solar wind acceleration region, is also proposed.

Bochsler, P.; Moebius, E.

1993-06-01

70

Electrostatic Solitary Waves in the Solar Wind: Evidence for Instability at Solar Wind Current Sheets  

NASA Technical Reports Server (NTRS)

A strong spatial association between bipolar electrostatic solitary waves (ESWs) and magnetic current sheets (CSs) in the solar wind is reported here for the first time. This association requires that the plasma instabilities (e.g., Buneman, electron two stream) which generate ESWs are preferentially localized to solar wind CSs. Distributions of CS properties (including shear angle, thickness, solar wind speed, and vector magnetic field change) are examined for differences between CSs associated with ESWs and randomly chosen CSs. Possible mechanisms for producing ESW-generating instabilities at solar wind CSs are considered, including magnetic reconnection.

Malaspina, David M.; Newman, David L.; Wilson, Lynn Bruce; Goetz, Keith; Kellogg, Paul J.; Kerstin, Kris

2013-01-01

71

Turbulence in solar wind and laboratory plasmas  

SciTech Connect

Recent studies of plasma turbulence based on measurements within solar wind and laboratory plasmas has been discussed. Evidences for the presence of a turbulent energy cascade, using the Yaglom's law for MHD turbulence, has been provided through data from the Ulysses spacecraft. This allows, for the first time, a direct estimate of the turbulent energy transfer rate, which can contribute to the in situ heating of the solar wind. The energy cascade has been evidenced also for ExB electrostatic turbulence in laboratory magnetized plasmas using measurements of intermittent transport (bursty turbulence) at the edge of the RFX-mod reversed field pinch plasma device. Finally the problem of the dispersive region of turbulence in solar wind above the ion-cyclotron frequency, where a spectral break is usually observed, and the problem of dissipation in a collisionless fluid as the solar wind, are briefly discussed.

Carbone, V. [Dipartimento di Fisica, Universita della Calabria, 87036 Rende (Italy) and Licryl Regional Laboratory/CNR, Ponte P. Bucci Cubo 33B, 87036 Rende (Italy)

2010-06-16

72

The solar wind in the outer heliosphere  

E-print Network

The solar wind evolves as it moves outward due to interactions with both itself and with the circum-heliospheric interstellar medium. The speed is, on average, constant out to 30 AU, then starts a slow decrease due to the ...

Richardson, John D.

73

Pluto's interaction with the solar wind  

SciTech Connect

If Pluto's atmospheric escape rate is significantly greater than 1.5 x 10{sup 27} molecules s{sup {minus}1} then the interaction with the tenuous solar wind at 30 A.U. will be like that of a comet: there will be extensive ion pick-up upstream and the size of the interaction region will vary directly with variations in the solar wind flux. If the escape flux is much less, then one expects that the solar wind will be deflected around Pluto's ionosphere in a Venus-like interaction. In either case, the weak interplanetary magnetic field at 30 A.U. results in very large gyroradii for the picked up ions and a thick bow shock, necessitating a kinetic treatment of the interaction. Strong variations in the size of the interaction region are expected on time scales of days due to changes in the solar wind.

Bagenal, F. (Univ. of Colorado, Boulder (USA)); McNutt, R.L. Jr. (Massachusetts Institute of Technology, Cambridge (USA))

1989-11-01

74

A Comparison of Solar Wind Conditions During the Genesis Mission with Forty Years of Solar Wind Observations  

NASA Astrophysics Data System (ADS)

To better understand how the solar wind sample collected during the Genesis mission relates to the average solar wind composition, we analyze the average plasma state of the solar wind during the Genesis mission and compare it to solar wind observations collected over the past 40 years.

Reisenfeld, D. B.; Steinberg, J. T.; Wiens, R. C.; Lepri, S.; Raines, J.

2011-03-01

75

Magnetic energy flow in the solar wind.  

NASA Technical Reports Server (NTRS)

Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun.

Modisette, J. L.

1972-01-01

76

The interaction of the solar wind with the interstellar medium  

NASA Technical Reports Server (NTRS)

The expected characteristics of the solar wind, extrapolated from the vicinity of the earth are described. Several models are examined for the interaction of the solar wind with the interstellar plasma and magnetic field. Various aspects of the penetration of neutral interstellar gas into the solar wind are considered. The dynamic effects of the neutral gas on the solar wind are described. Problems associated with the interaction of cosmic rays with the solar wind are discussed.

Axford, W. I.

1972-01-01

77

Empirical Solar Wind Forecasting from the Chromosphere  

E-print Network

Recently, we correlated the inferred structure of the solar chromospheric plasma topography with solar wind velocity and composition data measured at 1AU. We now offer a physical justification of these relationships and present initial results of a empirical prediction model based on them. While still limited by the fundamentally complex physics behind the origins of the solar wind and how its structure develops in the magnetic photosphere and expands into the heliosphere, our model provides a near continuous range of solar wind speeds and composition quantities that are simply estimated from the inferred structure of the chromosphere. We suggest that the derived quantities may provide input to other, more sophisticated, prediction tools or models such as those to study Coronal Mass Ejections (CME) propagation and Solar Energetic Particle (SEP) generation.

Robert J. Leamon; Scott W. McIntosh

2007-01-11

78

Magnetospheric response to solar wind variations  

SciTech Connect

The time lagged response of the magnetosphere to solar wind variations has been determined using the linear prediction filtering method and 34 intervals of high time resolution IMP-8 solar wind data and auroral electrojet AL index data. The linear prediction filtering method is a powerful time series analysis technique which is utilized to produce a filter of time lagged response coefficients which estimates the most general linear relationship between magnetospheric activity and solar wind variations. This study uses the AL index to monitor the magnetosphere's response and VB/sub s/ to monitor the solar wind input. Before analysis, the median value of the AL index for each of the 34 intervals was utilized to rank the intervals according to the level of geomagnetic activity. It is found that the VB/sub s/-AL filters are composed of two response pulses peaking at time lags of 20-minutes and 60-minutes. Our interpretation associates the 20-minute pulse with activity driven directly by solar wind-magnetosphere interaction and it associates the 60-minute pulse with activity driven by the release of stored energy from the magnetotail. Thus, the filter results suggest that both the directly driven and the unloading models of magnetospheric response are important in describing the time lagged response of the magnetosphere to solar wind variations. 11 refs., 3 figs.

Bargatze, L.F.; Baker, D.N.; McPherron, R.L.

1985-04-01

79

Origin of the Ubiquitous Fast Solar Wind  

NASA Technical Reports Server (NTRS)

The solar wind is a direct manifestation of the coronal heating processes which continue to elude us. For over three decades, observations in interplanetary space have identified two types of wind: a slow component with highly variable physical properties also characterized by speeds typically beow 500 kn/s, and a much less variable fast wind flowing on average at 750 km/s1.

Habbal, S. R.; Woo, R.; Fineschi, S.; O'Neal, R.; Kohl, J.; Noci, G.

1997-01-01

80

Sulfur abundances in the solar wind measured by SWICS on Ulysses. [Solar Wind Ion Composition Spectrometer  

NASA Technical Reports Server (NTRS)

One of the nine experiments on Ulysses (launched October, 1990), the Solar Wind Ion Composition Spectrometer, utilizes an energy per charge deflection system along with time of flight technology to uniquely determine the mass and mass per charge of solar wind particles. Thus the composition of various solar wind types can be analyzed. Using the SWICS data accumulated during the in-ecliptic phase of the mission, we have determined the sulfur abundance, relative to silicon, in two different types of solar wind: transient and coronal hole associated flows. Sulfur is of extreme interest because it is one of the few elements that lies in the transitional region of the FIP-dependent relative abundance enrichment function, observed for solar energetic particles and some types of solar wind flows.

Shafer, C. M.; Gloeckler, G.; Galvin, A. B.; Ipavich, F. M.; Geiss, J.; Von Steiger, R.; Ogilvie, K.

1993-01-01

81

About the correlation between solar micro bursts and the change of the solar wind parameters  

E-print Network

The Sun is the closest star to our planet and it is the most studied, perhaps, there exist too much procesess not-understood. One of the solar processes that have a direct interaction with the earth is the solar wind. The solar wind is defined as the plasma expulsed from the solar atmosphere, this wind was cataloged and is considered that have three components: - Passive solar wind: Is the constant component of the solar wind. - Supersonic and quasistady flux. - Sporadic supersonic flux. We present and brief explanation of the Parker's model of the solar wind and a correlation analysis between solar micro radio bursts and the change of the solar wind parameters.

Juan Carlos Martinez Oliveros; Daniel Ricardo Izquierdo P

2005-08-02

82

The Genesis Solar Wind Sample Return Mission  

NASA Technical Reports Server (NTRS)

The Genesis spacecraft was launched on August 8 from Cape Canaveral on a journey to become the first spacecraft to return from interplanetary space. The fifth in NASA's line of low-cost Discovery-class missions, its goal is to collect samples of solar wind and return them to Earth for detailed isotopic and elemental analysis. The spacecraft is to collect solar wind for over two years, while circling the L1 point 1.5 million km sunward of the earth, before heading back for a capsule-style re-entry in September, 2004. After parachute deployment, a mid-air helicopter recovery will be used to avoid a hard landing. The mission has been in the planning stages for over ten years. Its cost, including development, mission operations, and sample analysis, is approximately $209M. The Genesis science team, headed by principal investigator Donald Burnett of Caltech, consists of approximately 20 co-investigators from universities and science centers around the country and internationally. The spacecraft consists of a relatively flat spacecraft bus containing most of the subsystem components, situated below a sample return capsule (SRC) which holds the solar-wind collection substrates and an electrostatic solar wind concentrator. Some of the collectors are exposed throughout the collection period, for a sample of bulk solar wind, while others are exposed only to certain solar wind regimes, or types of flow. Ion and electron spectrometers feed raw data to the spacecraft control and data-handling (C&DH) unit, which determines ion moments and electron flux geometries in real time. An algorithm is used to robotically decide between interstream (IS), coronal hole (CH), and coronal mass ejection (CME) regimes, and to control deployment of the proper arrays to sample these wind regimes independently. This is the first time such a solar-wind decision algorithm has been used on board a spacecraft.

Wiens, Roger C.; Burnett, Donald S.; Neugebauer, Marcia; Sasaki, Chester; Sevilla, Donald; Stansbery, Eileen; Clark, Ben; Smith, Nick; Oldham, Lloyd

1990-01-01

83

The Genesis Mission Solar Wind Collection: Solar-Wind Statistics over the Period of Collection  

NASA Technical Reports Server (NTRS)

The NASA Genesis spacecraft was launched August 8, 2001 on a mission to collect samples of solar wind for 2 years and return them to earth September 8, 2004. Detailed analyses of the solar wind ions implanted into high-purity collection substrates will be carried out using various mass spectrometry techniques. These analyses are expected to determine key isotopic ratios and elemental abundances in the solar wind, and by extension, in the solar photosphere. Further, the photospheric composition is thought to be representative of the solar nebula with a few exceptions, so that the Genesis mission will provide a baseline for the average solar nebula composition with which to compare present-day compositions of planets, meteorites, and asteroids. The collection of solar wind samples is almost complete. Collection began for most substrates in early December, 2001, and is scheduled to be complete on April 2 of this year. It is critical to understand the solar-wind conditions during the collection phase of the mission. For this reason, plasma ion and electron spectrometers are continuously monitoring the solar wind proton density, velocity, temperature, the alpha/proton ratio, and angular distribution of suprathermal electrons. Here we report on the solar-wind conditions as observed by these in-situ instruments during the first half of the collection phase of the mission, from December, 2001 to present.

Barraclough, B. L.; Wiens, R. C.; Steinberg, J. E.; Reisenfeld, D. B.; Neugebauer, M.; Burnett, D. S.; Gosling, J.; Bremmer, R. R.

2004-01-01

84

OMNIWeb: The Ionosphere and Solar Wind  

NSDL National Science Digital Library

This educational brief provides an overview of the layers of the atmosphere, the effects of the solar wind upon them, and how these effects are mitigated by Earth's magnetic field. It also describes OMNIWeb, an internet-based data retrieval interface for obtaining datasets on solar energetic particles.

85

Interaction of Mercury with the Solar Wind  

Microsoft Academic Search

We present the structure of the hermean magnetosphere obtained by a global three-dimensional MHD simulation. The magnetic field of Mercury is strong enough to form a permanent magnetosphere under typical solar wind conditions. Mercury does not have a substantial atmosphere or ionosphere which makes the magnetosphere unique in the solar system. We study in detail the hermean magnetosphere for the

K. Kabin; T. I. Gombosi; D. L. DeZeeuw; K. G. Powell

2000-01-01

86

THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF MAGNETIZED WINDS OF SOLAR-LIKE STARS  

SciTech Connect

By means of self-consistent three-dimensional magnetohydrodynamics (MHD) numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-{beta} parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal three-dimensional MHD equations. We adopt in our simulations a heating parameter described by {gamma}, which is responsible for the thermal acceleration of the wind. We analyze winds with polar magnetic field intensities ranging from 1 to 20 G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. For the maximum magnetic intensity simulated of 20 G and solar coronal base density, the wind velocity reaches values of {approx}1000 km s{sup -1} at r {approx} 20r {sub 0} and a maximum temperature of {approx}6 x 10{sup 6} K at r {approx} 6r {sub 0}. The increase of the field intensity generates a larger 'dead zone' in the wind, i.e., the closed loops that inhibit matter to escape from latitudes lower than {approx}45 deg. extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the density and maintaining B {sub 0} = 20 G the system recover back to slower and cooler winds. For a fixed {gamma}, we show that the key parameter in determining the wind velocity profile is the {beta}-parameter at the coronal base. Therefore, there is a group of magnetized flows that would present the same terminal velocity despite its thermal and magnetic energy densities, as long as the plasma-{beta} parameter is the same. This degeneracy, however, can be removed if we compare other physical parameters of the wind, such as the mass-loss rate. We analyze the influence of {gamma} in our results and we show that it is also important in determining the wind structure.

Vidotto, A. A.; Jatenco-Pereira, V. [University of Sao Paulo, Rua do Matao 1226, Sao Paulo, SP 05508-090 (Brazil); Opher, M. [George Mason University, 4400 University Drive, Fairfax, VA 22030-4444 (United States); Gombosi, T. I. [University of Michigan, 1517 Space Research Building, Ann Arbor, MI 48109-2143 (United States)], E-mail: aline@astro.iag.usp.br

2009-07-01

87

Solar Cycle Effects on Solar Wind-Magnetosphere Coupling  

NASA Astrophysics Data System (ADS)

It is well established that solar wind coupling to the magnetosphere is a maximum at the equinoxes. This is a geometric effect partially caused by the projection of the IMF onto the GSM Z-axis. In the Russell-McPherron effect activity is a maximum at equinox according to the rule "spring to fall away". Recently it has been shown that the equinoctial maximum is also a result of dipole tilt towards and away from the Sun. Coupling is less efficient when this angle departs from 90 degrees. The actual disturbance measured on the ground also depends on ionospheric conductivity so that it is unclear which factors are dominant is determining the strength of ground disturbances. Since conductivity depends on solar UV it is likely that coupling to the magnetosphere is modulated by the solar cycle. In addition we have recently found evidence that coupling depends on the Mach number of the solar wind. This property is modulated by the solar cycle through its dependence on the occurrence of CMEs. These considerations lead us to speculate that there should be an obvious solar cycle dependence of the coupling of the solar wind to the magnetosphere. We will investigate this hypothesis by calculating the prediction filters that relate the solar wind electric field to several different magnetic indices including AL, sym-H, and PC. Filters will be calculated at equinox and solstice for each year of the solar cycle. The sum of the filter coefficients will be used as a measure of coupling strength.

McPherron, R. L.

2005-05-01

88

Solar Wind Forecasting with Coronal Holes  

E-print Network

An empirical model for forecasting solar wind speed related geomagnetic events is presented here. The model is based on the estimated location and size of solar coronal holes. This method differs from models that are based on photospheric magnetograms (e.g., Wang-Sheeley model) to estimate the open field line configuration. Rather than requiring the use of a full magnetic synoptic map, the method presented here can be used to forecast solar wind velocities and magnetic polarity from a single coronal hole image, along with a single magnetic full-disk image. The coronal hole parameters used in this study are estimated with Kitt Peak Vacuum Telescope He I 1083 nm spectrograms and photospheric magnetograms. Solar wind and coronal hole data for the period between May 1992 and September 2003 are investigated. The new model is found to be accurate to within 10% of observed solar wind measurements for its best one-month periods, and it has a linear correlation coefficient of ~0.38 for the full 11 years studied. Using a single estimated coronal hole map, the model can forecast the Earth directed solar wind velocity up to 8.5 days in advance. In addition, this method can be used with any source of coronal hole area and location data.

S. Robbins; C. J. Henney; J. W. Harvey

2007-01-09

89

New Horizons Solar Wind Around Pluto Solar Wind (SWAP) Measurements from 5 to 23 AU  

NASA Astrophysics Data System (ADS)

This year the Solar Wind Around Pluto (SWAP) instrument on the New Horizons (NH) spacecraft collected 79 days of solar wind measurements during hibernation, about 30 days of data during annual checkout operations, and has begun recording another 168 days of data in hibernation which will be played back next year. The currently available NH-SWAP solar wind observations now span from about 5.1 to 23.4 AU. We examine how the peak solar wind speed in the New Horizons measurements vary with distance, report on progress toward automating the fitting of the SWAP solar wind count rate distributions, and take an initial look at the solar wind temperature-speed relationship beyond 11 AU. Since most of the SWAP solar wind observations were collected while spinning, and ions from the entire field-of-view (10 by 276 degrees) are focused onto one pair of coincidence Channel Electron Multiplier, we need to evaluate the effect of spinning on the measured rates. By comparing the 3-axis stabilized, to the rolling and spinning measurements, we strive to assess spin variations in the observed SWAP count rates and develop techniques to account for them. To test our analysis, we fit simulated count rate distributions to quantify how well our technique recovers the input solar wind conditions.

Elliott, H. A.; McComas, D. J.; Delamere, P. A.

2012-12-01

90

Comparison of VLF Wave Activity in the Solar Wind During Solar Maximum and Minimum  

E-print Network

Comparison of VLF Wave Activity in the Solar Wind During Solar Maximum and Minimum: Ulysses and intermediate speed solar wind. The maximum intensity of the electromagnetic waves for the two solar cycle are similar for the slow and intermediate solar wind in both solar maximum and minimum phases. It is also

California at Berkeley, University of

91

The Solar Wind in the Outer Heliosphere at Solar John D. Richardson and Chi Wang  

E-print Network

The Solar Wind in the Outer Heliosphere at Solar Maximum John D. Richardson and Chi Wang Center solar wind observations in the outer heliosphere, concentrating on the recent data near solar maximum-absence of a latitudinal speed gradient at solar maximum allows us to measure the speed decrease of the solar wind and nd

Richardson, John

92

PULSED ALFVEN WAVES IN THE SOLAR WIND  

SciTech Connect

Using 3 s plasma and magnetic field data from the Wind spacecraft located in the solar wind well upstream from Earth, we report observations of isolated, pulse-like Alfvenic disturbances in the solar wind. These isolated events are characterized by roughly plane-polarized rotations in the solar wind magnetic field and velocity vectors away from the directions of the underlying field and velocity and then back again. They pass over Wind on timescales ranging from seconds to several minutes. These isolated, pulsed Alfven waves are pervasive; we have identified 175 such events over the full range of solar wind speeds (320-550 km s{sup -1}) observed in a randomly chosen 10 day interval. The large majority of these events are propagating away from the Sun in the solar wind rest frame. Maximum field rotations in the interval studied ranged from 6 Degree-Sign to 109 Degree-Sign . Similar to most Alfvenic fluctuations in the solar wind at 1 AU, the observed changes in velocity are typically less than that predicted for pure Alfven waves (Alfvenicity ranged from 0.28 to 0.93). Most of the events are associated with small enhancements or depressions in magnetic field strength and small changes in proton number density and/or temperature. The pulse-like and roughly symmetric nature of the magnetic field and velocity rotations in these events suggests that these Alfvenic disturbances are not evolving when observed. They thus appear to be, and probably are, solitary waves. It is presently uncertain how these waves originate, although they may evolve out of Alfvenic turbulence.

Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 (United States); Tian, H. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (United States); Phan, T. D., E-mail: jack.gosling@lasp.colorado.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2011-08-20

93

Titan interaction with the supersonic solar wind  

E-print Network

After 9 years in the Saturn system, the Cassini spacecraft finally observed Titan in the supersonic solar wind. These unique observations reveal that Titan interaction with the solar wind is in many ways similar to un-magnetized planets Mars and Venus in spite of the differences in the properties of the solar plasma in the outer solar system. In particular, Cassini detected a collisionless, supercritical bow shock and a well-defined induced magnetosphere filled with mass-loaded interplanetary magnetic field lines, which drape around Titan ionosphere. Although the flyby altitude may not allow the detection of an ionopause, Cassini reports enhancements of plasma density compatible with plasma clouds or streamers in the flanks of its induced magnetosphere or due to an expansion of the induced magnetosphere. Because of the upstream conditions, these observations are also relevant for unmagnetized bodies in the outer solar system such as Pluto, where kinetic processes are expected to dominate.

Bertucci, C; Kurth, W S; Hospodarsky, G; Mitchell, D; Sergis, N; Edberg, N J T; Dougherty, M K

2014-01-01

94

Solar-wind minor ions: recent observations  

SciTech Connect

During the years following the Solar Wind Four Conference at Burghausen our knowledge of the solar wind ion composition and dynamics has grown. There have been some surprises, and our understanding of the evolution of the solar wind has been improved. Systematic studies have shown that the minor ions generally travel with a common bulk speed and have temperatures roughly proportional to their masses. It has been determined that the /sup 3/He/sup + +/ content varies greatly; /sup 3/He/sup + +///sup 4/He/sup + +/ ranges from as high as 10/sup 2/ values to below 2 x 10/sup -4/. In some solar wind flows which can be related to energetic coronal events, the minor ions are found in unusual ionization states containing Fe/sup 16 +/ as a prominent ion, showing that the states were formed at unusually high temperatures. Unexpectedly, in a few flows substantial quantities of /sup 4/He/sup +/ have been detected, sometimes with ions identifiable as O/sup 2 +/ and O/sup 3 +/. Surprisingly, in some of these examples the ionization state is mixed showing that part of the plasma escaped the corona without attaining the usual million-degree temperatures while other parts were heated more nearly in the normal manner. Additionally, detailed studies of the minor ions have increased our understanding of the coronal expansion. For example, such studies have contributed to identifying near equatorial coronal streamers as the source of solar wind flows between high speed streams.

Bame, S.J.

1982-01-01

95

Laboratory Facility for Simulating Solar Wind Sails  

SciTech Connect

Magnetic sail (MagSail) is a deep space propulsion system, in which an artificial magnetic cavity captures the energy of the solar wind to propel a spacecraft in the direction leaving the sun. For a scale-model experiment of the plasma flow of MagSail, we employed a magnetoplasmadynamic arcjet as a solar wind simulator. It is observed that a plasma flow from the solar wind simulator reaches a quasi-steady state of about 0.8 ms duration after a transient phase when initiating the discharge. During this initial phase of the discharge, a blast-wave was observed to develop radially in a vacuum chamber. When a solenoidal coil (MagSail scale model) is immersed into the quasi-steady flow where the velocity is 45 km/s, and the number density is 10{sup 19} m-3, a bow shock as well as a magnetic cavity were formed in front of the coil. As a result of the interaction between the plasma flow and the magnetic cavity, the momentum of the simulated solar wind is decreased, and it is found from the thrust measurement that the solar wind momentum is transferred to the coil simulating MagSail.

Funaki, Ikkoh [Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, 229-8510 (Japan); JST/CREST, Kawaguchi, Saitama, 332-0012 (Japan); Ueno, Kazuma; Oshio, Yuya [Graduate University for Advanced Studies, Sagamihara, Kanagawa, 229-8510 (Japan); Ayabe, Tomohiro; Horisawa, Hideyuki [Tokai University, Hiratsuka, Kanagawa, 259-1292 (Japan); Yamakawa, Hiroshi [Kyoto University, Uji, Kyoto, 611-0011 (Japan); JST/CREST, Kawaguchi, Saitama, 332-0012 (Japan)

2008-12-31

96

Solar wind ion composition and charge states  

SciTech Connect

The solar wind, a highly tenuous plasma streaming from the Sun into interplanetary space at supersonic speed, is roughly composed of 95% hydrogen and 5% helium by number. All other, heavy elements contribute less than 0.1% by number and thus are truly test particles Nevertheless, these particles provide valuable information not present in the main components. The authors first discuss the importance of the heavy ions as tracers for processes in the solar atmosphere. Specifically, their relative abundances are found to be different in the solar wind as compared to the photosphere. This fractionation, which is best organized as a function of the first ionization time (FIT) of the elements under solar surface conditions, provides information on the structure of the chromosphere, where it is imparted on the partially ionized material by an atom-ion separation mechanism. Moreover, the charge states of the heavy ions can be used to infer the coronal temperature, since they are frozen-in near the altitude where the expansion time scale overcomes the ionization/recombination time scales. Next, the authors review the published values of ion abundances in the solar wind, concentrating on the recent results of the SWICS instrument on Ulysses. About 8 elements and more than 20 charge states can be routinely analyzed by this sensor. There is clear evidence that both the composition and the charge state distribution is significantly different in the fast solar wind from the south polar coronal hole, traversed by Ulysses in 1993/94, as compared to the solar wind normally encountered near the ecliptic plane. The fractionation between low- and high-FIT elements is reduced, and the charge states indicate a lower, more uniform coronal temperature in the hole. Finally, the authors discuss these results in the framework of existing theoretical models of the chromosphere and corona, attempting to identify differences between the low- and high-latitude regions of the solar atmosphere.

Vonsteiger, R.

1995-06-01

97

Solar wind proton temperature-velocity relationship  

NASA Technical Reports Server (NTRS)

Helios 1 data are analyzed to find an experimental fit for the temperature-velocity relationship at 1 AU. It is shown that the proton temperature-velocity changes at a velocity of approximately 500 km/s. Interplanetary dynamic processes, i.e., stream interactions, are shown to affect the temperature-velocity relationships less than 22 percent; the functional form of these relationships appears to be preserved throughout the solar cycle. It is pointed out that any comprehensive model of the solar wind will have to address the difference in the temperature-velocity relationship between the low- and high-speed wind, since this is a product of the acceleration and subsequent heating process generating the solar wind.

Lopez, R. E.; Freeman, J. W.

1986-01-01

98

Shock heating of the solar wind plasma  

NASA Technical Reports Server (NTRS)

The role played by shocks in heating solar-wind plasma is investigated using data on 413 shocks which were identified from the plasma and magnetic-field data collected between 1973 and 1982 by Pioneer and Voyager spacecraft. It is found that the average shock strength increased with the heliocentric distance outside 1 AU, reaching a maximum near 5 AU, after which the shock strength decreased with the distance; the entropy of the solar wind protons also reached a maximum at 5 AU. An MHD simulation model in which shock heating is the only heating mechanism available was used to calculate the entropy changes for the November 1977 event. The calculated entropy agreed well with the value calculated from observational data, suggesting that shocks are chiefly responsible for heating solar wind plasma between 1 and 15 AU.

Whang, Y. C.; Liu, Shaoliang; Burlaga, L. F.

1990-01-01

99

Genesis Capsule Yields Solar Wind Samples  

NASA Astrophysics Data System (ADS)

NASA's Genesis capsule, carrying the first samples ever returned from beyond the Moon, took a hard landing in the western Utah desert on 8 September after its parachutes failed to deploy. Despite the impact, estimated at 310 km per hour, some valuable solar wind collector materials have been recovered. With these samples, the Genesis team members are hopeful that nearly all of the primary science goals may be met. The Genesis spacecraft was launched in August 2001 to collect and return samples of solar wind for precise isotopic and elemental analysis. The spacecraft orbited the Earth-Sun Lagrangian point (L1), ~1.5 million km sunward of the Earth, for 2.3 years. It exposed ultrapure materials-including wafers of silicon, silicon carbide, germanium, chemically deposited diamond, gold, aluminum, and metallic glass-to solar wind ions, which become embedded within the substrates' top 100 nm of these materials.

Wiens, Roger C.; Burnett, Donald S.; Stansbery, Eileen K.; McNamara, Karen M.

2004-11-01

100

Solar cycle evolution of the solar wind in three dimensions  

NASA Technical Reports Server (NTRS)

Measurements of the solar wind speed both in and out of the ecliptic are presented for 1971-82. The speed estimates, which were made with the interplanetary scintillation system at UC San Diego, have been compared to in situ for large, slowly evolving structures, and thus such structures can be studied up to 60 degrees north and south heliographic latitude. Annual average wind speeds are presented versus latitude for an entire solar cycle. Fast wind streams from the poles persisted through declining and low solar activity, but were closed off during four years of high activity. This evolution follows that of the polar coronal holes, as displayed by comparing averaged speed and coronal density over latitude and longitude. The most recent data (1982) show the reestablishment of large tilted polar holes and associated fast streams. Coronal magnetic field data show that the neutral sheet is confined to low latitudes at solar minimum and extends to high latitudes at solar maximum; thus the slow solar wind comes from the same latitude range as that of the neutral sheet.

Rickett, B. J.; Coles, W. A.

1983-01-01

101

Magnetosphere II: The Solar Wind Strikes Back!  

NSDL National Science Digital Library

A view of a computer-generated model of the Earth's magnetosphere. Semi-transparent surfaces represent particle density (red is high, blue is low), the silvery tube represent magnetic field lines and the yellow ribbons represent the paths of charged solar wind particles. In this particular model, the solar wind has an ambient density of 8.35 particles-cm^3. The isosurfaces are then red (>17 particles-cm^3), yellow (>12 particles-cm^3), green (>8.6 particles-cm^3) and blue (<1.0 particle-cm^3).

Bridgman, Tom; Mitchell, Horace; Sokolowsky, Eric; Spicer, Dan

2002-03-01

102

Geomagnetic activity: Dependence on solar wind parameters  

NASA Technical Reports Server (NTRS)

Current ideas about the interaction between the solar wind and the earth's magnetosphere are reviewed. The solar wind dynamic pressure as well as the influx of interplanetary magnetic field lines are both important for the generation of geomagnetic activity. The influence of the geometry of the situation as well as the variability of the interplanetary magnetic field are both found to be important factors. Semi-annual and universal time variations are discussed as well as the 22-year cycle in geomagnetic activity. All three are found to be explainable by the varying geometry of the interaction. Long term changes in geomagnetic activity are examined.

Svalgaard, L.

1977-01-01

103

Solar Wind Change Exchange from the Magnetosheath  

NASA Technical Reports Server (NTRS)

We report the results of a long (approximately 100 ks) XMM-Newton observation designed to observe solar wind charge exchange emission (SWCX) from Earth's magnetosheath. By luck, the observation took place during a period of minimal solar wind flux so the SWCX emission was also minimal. Never-the-less, there is a significant if not stunning correlation between the observed O VIII count rate and our model for magnetosheath emission. We also report on the observed O VII and O VII emission.

Snowden, Steve

2008-01-01

104

Workshop on Solar Activity, Solar Wind, Terrestrial Effects, and Solar Acceleration  

NASA Technical Reports Server (NTRS)

A summary of the proceedings from the workshop are presented. The areas covered were solar activity, solar wind, terrestrial effects, and solar acceleration. Specific topics addressed include: (1) solar cycle manifestations, both large and small scale, as well as long-term and short-term changes, including transients such as flares; (2) sources of solar wind, as identified by interplanetary observations including coronal mass ejections (CME's) or x-ray bright points, and the theory for and evolution of large-scale and small-scale structures; (3) magnetosphere responses, as observed by spacecraft, to variable solar wind and transient energetic particle emissions; and (4) origin and propagation of solar cosmic rays as related to solar activity and terrestrial effects, and solar wind coronal-hole relationships and dynamics.

1992-01-01

105

Solar cycle dependence of nightside field-aligned currents: Effects of dayside ionospheric conductivity on the solar wind-magnetosphere-ionosphere coupling  

NASA Astrophysics Data System (ADS)

the present study we observationally address the role of ionospheric conductivity in the solar wind-magnetosphere coupling in terms of global field-aligned currents (FACs). Solar EUV irradiance changes during a solar cycle and so does its contribution to the ionospheric conductivity. We statistically examine how, under fixed external conditions, the intensities of the R1 and R2 currents and their demarcation latitude depend on solar activity (F10.7). An emphasis is placed on nightside FACs in the dark hemisphere. The result shows that for fixed ranges of interplanetary electric field, the nightside FACs are more intense for higher solar activity irrespective of their polarities or local times. It is also found that the R1-R2 pair, therefore the auroral oval, moves equatorward as the solar activity increases. For both current intensity and latitude, the dependence on F10.7 is more sensitive at smaller F10.7 and it levels off with increasing F10.7. The intensities of dayside FACs reveal similar F10.7 dependence as expected from the enhancement of the local ionospheric conductance. Interestingly, they also move equatorward with increasing F10.7. It is expected from force balance that as the dayside R1 current becomes more intense with increasing solar activity, the magnetosphere shrinks on the day side and expands on the night side. This configurational change of the magnetosphere presumably affects the energy transport from the solar wind to the magnetosphere, although its details still remain to be understood. We conclude that the ionospheric conductivity plays an active role in the solar wind-magnetosphere-ionosphere coupling.

Ohtani, S.; Wing, S.; Merkin, V. G.; Higuchi, T.

2014-01-01

106

What Determines the Solar Wind Speed ?  

Microsoft Academic Search

Recent observations by Interplanetary Scintillation measurements by Nagoya-STEL group (Hirano et al.2003; Kojima et al.2004) show that solar wind speed is well-correlated with B\\/f, where B is radial magnetic field strength at the solar surface and f is a super-radial expansion factor of open flux tubes. We show that this correlation is nicely explained by dissipation of Alfven waves no

T. K. Suzuki; K. Fujiki; M. Kojima; M. Tokumaru; M. Hirano; D. Baba; M. Yamasita; K. Hakamada

2005-01-01

107

Coronal Plumes in the Fast Solar Wind  

NASA Technical Reports Server (NTRS)

The expansion of a coronal hole filled with a discrete number of higher density coronal plumes is simulated using a time-dependent two-dimensional code. A solar wind model including an exponential coronal heating function and a flux of Alfven waves propagating both inside and outside the structures is taken as a basic state. Different plasma plume profiles are obtained by using different scale heights for the heating rates. Remote sensing and solar wind in situ observations are used to constrain the parameter range of the study. Time dependence due to plume ignition and disappearance is also discussed. Velocity differences of the order of approximately 50 km/s, such as those found in microstreams in the high-speed solar wind, may be easily explained by slightly different heat deposition profiles in different plumes. Statistical pressure balance in the fast wind data may be masked by the large variety of body and surface waves which the higher density filaments may carry, so the absence of pressure balance in the microstreams should not rule out their interpretation as the extension of coronal plumes into interplanetary space. Mixing of plume-interplume material via the Kelvin-Helmholtz instability seems to be possible within the parameter ranges of the models defined here, only at large di stances from the Sun, beyond 0.2-0.3 AU. Plasma and composition measurements in the inner heliosphere, such as those which will become available with Solar Orbiter and Solar Probe Plus, should therefore definitely be able to identify plume remnants in the solar wind.

Velli, Marco; Lionello, Roberto; Linker, Jon A.; Mikic, Zoran

2011-01-01

108

The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons  

E-print Network

1 The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons D. McComas1,* , F. Allegrini1Comas@swri.edu) Abstract. The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide

Stern, S. Alan

109

The solar wind-magnetosphere energy coupling and magnetospheric disturbances  

Microsoft Academic Search

Energy coupling between the solar wind and the magnetosphere is examined and the influence of this coupling on magnetospheric disturbances is discussed. Following a review of the components of the total energy production rate of the magnetosphere and progress in the study of solar wind-magnetosphere correlations, the derivation of the solar wind-magnetosphere energy coupling function, which has been found to

S.-I. Akasofu

1980-01-01

110

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind  

E-print Network

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind C. S. Ng Center for Magnetic (MHD) turbulence Observations in ISM and solar wind · Anisotropy due to magnetic field · Electron MHD density spectrum and spatial scales wave number density Kolmogorov law #12;Solar wind turbulence From

Ng, Chung-Sang

111

The Solar Wind, CMEs and the Origins of Heliospheric Activity  

E-print Network

The Solar Wind, CMEs and the Origins of Heliospheric Activity Peter T. Gallagher School of Physics release o Coronal holes o Source of high-speed solar wind #12;peter.gallagher@tcd.ie #12;#12;peter.gallagher@tcd.ie #12;#12;The solar wind o Biermann (1951): comets showed excess ionization and abrupt changes

112

Measuring the Isotopic Composition of Solar Wind Noble Gases  

E-print Network

5 Measuring the Isotopic Composition of Solar Wind Noble Gases Alex Meshik, Charles Hohenberg, Olga and processes leading to the variations observed and how the present solar wind noble gases may differ from and breccias, implanted with solar wind noble gases, did provide a needed ground truth, neither by themselves

113

Magnetospheric cavity modes driven by solar wind dynamic pressure fluctuations  

E-print Network

Magnetospheric cavity modes driven by solar wind dynamic pressure fluctuations S. G. Claudepierre,1-dimensional magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere interaction. We use these simulations to investigate the role that solar wind dynamic pressure fluctuations play in the generation of magnetospheric

114

Turbulent heating of the corona and solar wind: the heliospheric  

E-print Network

Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale that the gas is highly ionized, i.e. a magnetized collisionless plasma ( solar wind model A `solar wind' is accelerated from the corona - Hydrostatic solution (similar to Bondi accretion

115

The driving of the plasma sheet by the solar wind  

Microsoft Academic Search

The coupling of the plasma sheet to the solar wind is studied statistically using measurements from various satellite pairs: one satellite in the solar wind and one in either the magnetotail central plasma sheet or the near-Earth plasma sheet. It is found that the properties of the plasma sheet are highly correlated with the properties of the solar wind: specifically

Joseph E. Borovsky; Michelle F. Thomsen; Richard C. Elphic

1998-01-01

116

Evidence for Langmuir wave tunneling in the inhomogeneous solar wind  

E-print Network

Evidence for Langmuir wave tunneling in the inhomogeneous solar wind A. J. Willes School of Physics tunneling in evanescent regions in the inhomogeneous solar wind. Incident Langmuir waves which are nearly for Langmuir wave tunneling in the inhomogeneous solar wind, J. Geophys. Res., 107(A10), 1320, doi:10

California at Berkeley, University of

117

Martian magnetic morphology: Contributions from the solar wind and crust  

E-print Network

Martian magnetic morphology: Contributions from the solar wind and crust D. A. Brain and F. Bagenal of the solar wind and of crustal magnetic sources. We analyze MAG data to characterize the upstream interplanetary magnetic field (IMF) and confirm trends in the magnetic field expected from the solar wind

California at Berkeley, University of

118

Analysis of Wind Forces on RoofTop Solar Panel  

Microsoft Academic Search

Structural loads on solar panels include forces due to high wind, gravity, thermal expansion, and earthquakes. International Building Code (IBC) and the American Society of Civil Engineers are two commonly used approaches in solar industries to address wind loads. Minimum Design Loads for Buildings and Other Structures (ASCE 7-02) can be used to calculate wind uplift loads on roof-mounted solar

Yogendra Panta; Ganesh Kudav

2011-01-01

119

Energy Primer: Solar, Water, Wind, and Biofuels.  

ERIC Educational Resources Information Center

This is a comprehensive, fairly technical book about renewable forms of energy--solar, water, wind, and biofuels. The biofuels section covers biomass energy, agriculture, aquaculture, alcohol, methane, and wood. The focus is on small-scale systems which can be applied to the needs of the individual, small group, or community. More than one-fourth…

Portola Inst., Inc., Menlo Park, CA.

120

Identifying Wind and Solar Ramping Events: Preprint  

SciTech Connect

Wind and solar power are playing an increasing role in the electrical grid, but their inherent power variability can augment uncertainties in power system operations. One solution to help mitigate the impacts and provide more flexibility is enhanced wind and solar power forecasting; however, its relative utility is also uncertain. Within the variability of solar and wind power, repercussions from large ramping events are of primary concern. At the same time, there is no clear definition of what constitutes a ramping event, with various criteria used in different operational areas. Here the Swinging Door Algorithm, originally used for data compression in trend logging, is applied to identify variable generation ramping events from historic operational data. The identification of ramps in a simple and automated fashion is a critical task that feeds into a larger work of 1) defining novel metrics for wind and solar power forecasting that attempt to capture the true impact of forecast errors on system operations and economics, and 2) informing various power system models in a data-driven manner for superior exploratory simulation research. Both allow inference on sensitivities and meaningful correlations, as well as the ability to quantify the value of probabilistic approaches for future use in practice.

Florita, A.; Hodge, B. M.; Orwig, K.

2013-01-01

121

Studying Solar Wind and Magnetosphere Interactions  

NSDL National Science Digital Library

This educational brief describes the structure of Earth's magnetosphere, how it interacts with energetic particles emitted by the sun, and how it protects Earth from the effects of these particles. Short descriptions of NASA missions to study the magnetosphere, solar wind, and other particle emissions are included.

122

Magnetopause location under extreme solar wind conditions  

Microsoft Academic Search

During the solar wind dynamic pressure enhancement, around 0200 UT on January 11, 1997, at the end of the January 6-11 magnetic cloud event, the magnetopause was pushed inside geosynchronous orbit. The LANL 1994-084 and GMS 4 geosynchronous satellites crossed the magnetopause and moved into the magnetosheath. Also, the Geotail satellite was in the magnetosheath while the Interball 1 satellite

J.-H. Shue; P. Song; J. T. Steinberg; J. K. Chao; G. Zastenker; O. L. Vaisberg; S. Kokubun; H. J. Singer; T. R. Detman; H. Kawano

1998-01-01

123

Triggering of substorms by solar wind discontinuities  

Microsoft Academic Search

In order to study the relationship between substorm occurrence and magnetospheric compression caused by solar wind discontinuities, 125 storm sudden commencements (ssc's) observed during the 4 years 1967-1970 were examined by using ground magnetograms, AE indices, and magnetic field data obtained by Explorer 33, 34, and 35 and OGO 5. Statistical and case studies confirm that geogmagnetic activity and interplanetary

S. Kokubun; R. L. McPherron; C.T. Russell

1977-01-01

124

Material Interactions with Solar Wind Ion Environments  

NASA Technical Reports Server (NTRS)

Solar wind composition is dominated by hydrogen (approx.96%) and helium (approx.3 to 4%) with a minor fraction (less than or equal to 1%) of heavy ions. Hydrogen (helium) ions impact spacecraft surfaces with energies from 0.5 to 5 keV (1.8 to 21 keV) due to variations in solar wind velocity from 300 km/s to 1000 km/sec with extremes of a few 10 s keV during periods of extremely high solar wind velocity exceeding 1000 km/sec. Mean impact energies are typically on the order of approximately 1 keV and 4 keV for hydrogen ions and helium ions, respectively. These energies are typically of the peak of the energy dependent light ion sputter yields for hydrogen and helium on many metals. In addition, light ions with kilovolt energies have been shown to produce blister (or exfoliation) damage to metal surfaces due to formation of high pressure gas bubbles within the materials when exposed to ion fluences on the order of 10(exp 16 to (10(exp 17 ions/sq cm. A number of spacecraft designs for current and future missions include gossamer polymer structures with thin metallic reflection coatings to shield instruments from the Sun or solar sail propulsion systems for use in a variety of locations in the inner solar system from 0.5 to 1 AU. In addition, there is interest in designing spacecraft for solar physics missions requiring operations as close to the Sun as 0.16 to 0.2 AU. Integrity of the metallic coatings is critical in many of these applications since degradation will result in modification of material thermal properties or exposure of polymers to solar UV photons which can compromise mission requirements. This paper will evaluate the relative contributions of sputtering and blister formation to material degradation in solar wind environments over a range of radial distances from the Sun to demonstrate where solar wind environments become important for materials selection. We will first review the physics and results from laboratory measurements of light ion sputtering, blistering, and exfoliation of metallic surfaces to establish the order of magnitude ion fluence required for significant surface damage. Solar wind ion fluence environments will then be evaluated due to variations in solar wind conditions as a function of solar cycle for varying distances from the Sun using models for radial variations in solar wind ion number density, temperature, and velocity to determine where sputtering and blistering is most likely to be an issue. Finally, ion fluence statistics for varying radial distances from the Sun will be shown to establish the mission duration and radial distances from the Sun where missions will encounter sufficient ion fluence to exhibit damage to metallic surfaces.

Minow, Joseph I.; McWilliams, Brett

2006-01-01

125

Genesis Solar Wind Concentrator: Computer Simulations of Performance Under Solar Wind Conditions  

Microsoft Academic Search

The design and operation of the Genesis Solar-Wind Concentrator relies heavily on computer simulations. The computer model\\u000a is described here, as well as the solar wind conditions used as simulation inputs, including oxygen charge state, velocity,\\u000a thermal, and angular distributions. The simulation included effects such as ion backscattering losses, which also affect the\\u000a mass fractionation of the instrument. Calculations were

Roger C. Wiens; Marcia Neugebauer; Daniel B. Reisenfeld; Ronald W. Moses; Jane E. Nordholt; Donald S. Burnett

2003-01-01

126

Magnetopause location under extreme solar wind conditions  

NASA Astrophysics Data System (ADS)

During the solar wind dynamic pressure enhancement, around 0200 UT on January 11, 1997, at the end of the January 6-11 magnetic cloud event, the magnetopause was pushed inside geosynchronous orbit. The LANL 1994-084 and GMS 4 geosynchronous satellites crossed the magnetopause and moved into the magnetosheath. Also, the Geotail satellite was in the magnetosheath while the Interball 1 satellite observed magnetopause crossings. This event provides an excellent opportunity to test and validate the prediction capabilities and accuracy of existing models of the magnetopause location for producing space weather forecasts. In this paper, we compare predictions of two models: the Petrinec and Russell [1996] model and the Shue et al. [1997] model. These two models correctly predict the magnetopause crossings on the dayside; however, there are some differences in the predictions along the flank. The Shue et al. [1997] model correctly predicts the Geotail magnetopause crossings and partially predicts the Interball 1 crossings. The Petrinec and Russell [1996] model correctly predicts the Interball 1 crossings and is partially consistent with the Geotail observations. We further found that some of the inaccuracy in Shue et al.'s predictions is due to the inappropriate linear extrapolation from the parameter range for average solar wind conditions to that for extreme conditions. To improve predictions under extreme solar wind conditions, we introduce a nonlinear dependence of the parameters on the solar wind conditions to represent the saturation effects of the solar wind dynamic pressure on the flaring of the magnetopause and saturation effects of the interplanetary magnetic field Bz on the subsolar standoff distance. These changes lead to a better agreement with the Interball 1 observations for this event.

Shue, J.-H.; Song, P.; Russell, C. T.; Steinberg, J. T.; Chao, J. K.; Zastenker, G.; Vaisberg, O. L.; Kokubun, S.; Singer, H. J.; Detman, T. R.; Kawano, H.

1998-08-01

127

Solar and solar wind sources of geomagnetic activity during grand solar maximum  

NASA Astrophysics Data System (ADS)

We have studied solar activity for over entire grand solar maximum from solar cycle 12 to 23. We have analyzed different solar activity proxies in detail and furthermore the solar originated disturbances and their geomagnetic effects. We compared the occurrence rate of the coronal mass ejections, high-speed streams and co-rotating interaction regions and the occurrence of geomagnetic storms and substorms. We identified and analyzed solar wind ULF waves in details. ULF fluctuations were identified from the solar wind using the Fourier method developed in this work. The solar wind ULFs were identified from ACE and Wind data and ground-based ULFs from Oulujärvi, Kilpisjärvi and Kevo magnetic observations. We found out that solar wind ULF occurrence peaks during the declining solar cycle phase in a same solar cycle phase where high-speed streams and substorms are found to peak. Our analysis furthermore shows that the trend of ULF waves detected from ground-based instruments is similar to the trend of solar wind ULFs.

Hynönen, Reko; Tanskanen, Eija

2014-05-01

128

Noncompressive density enhancements in the solar wind  

NASA Technical Reports Server (NTRS)

When the bulk flow speed is nearly constant or falling, high densities are sometimes observed in the solar wind. These densities do not appear to be generated in interplanetary space. It is noted that the magnetic field is not enhanced within these events, and that the proton and/or electron temperatures are low, varying in opposition to the density. About 1/3 of these density events contains interplanetary magnetic field reversals, some of which are noisy and do not qualify as sector boundaries. It is estimated that the average event contains approximately 10 to the 16th g of material and 2.6 x 10 to the 31st ergs, so that aggregated events, when they are common, make a negligible contribution to the total mass and energy budget of the solar wind at 1 AU. It is suggested that there may be an association between density enhancements and solar coronal mass ejection events.

Gosling, J. T.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Hildner, E.

1977-01-01

129

Simulation study of solar wind push on a charged wire: basis of solar wind electric sail propulsion  

Microsoft Academic Search

One possibility for propellantless propulsion in space is to use the momentum flux of the solar wind. A way to set up a solar wind sail is to have a set of thin long wires which are kept at high positive potential by an onboard electron gun so that the wires repel and deflect incident solar wind protons. The efficiency

P. Janhunen; A. Sandroos

2007-01-01

130

Combined high density solar panels and vertical wind turbines  

Microsoft Academic Search

The combined high density solar panels and vertical wind turbines consist of multiple solar panels with closely spaced solar cells on both sides which are supported by an open framework and vertical posts. The adoption of an elevated, rooftop solar panel array, supported by vertical posts makes the basic structure attractive for the inclusion of multiple vertical wind turbines, as

1978-01-01

131

15/06/2005 Solar Wind 11/SOHO 16 1 Radial Dependence of Solar  

E-print Network

15/06/2005 Solar Wind 11/SOHO 16 1 Radial Dependence of Solar Energetic Particle Events M.-B. Kallenrode #12;15/06/2005 Solar Wind 11/SOHO 16 2 Outline No discussion about composition and charge states spectra) #12;15/06/2005 Solar Wind 11/SOHO 16 3 Propagation of a delta-pulse Delta-pulse gives Green

Kallenrode, May-Britt

132

The relation of open magnetic structures to solar wind flow  

NASA Technical Reports Server (NTRS)

A study has been made of solar wind observations and models of the low-coronal magnetic field of the sun during the Skylab mission. Potential sources of solar wind plasma have been identified and in most cases systematically associated with observed solar wind flow features. The study pinpoints the problems of associating significant portions of the observed solar wind with sources outside coronal holes, although such associations are strongly suggested by the models. The phenomenological relationship between observed high solar wind speed at 1 AU and small coronal field divergence near the sun is examined and found to be well established but causally inconclusive in light of models of the outer heliosphere.

Levine, R. H.

1978-01-01

133

Pluto's solar wind interaction: Collisional effects  

NASA Astrophysics Data System (ADS)

Exospheric neutral atoms and molecules (primarily N2, with trace amounts of CH4 and CO according to our current understanding of Pluto's atmosphere) escape from Pluto and travel into interplanetary space for millions of kilometers. Eventually, the neutrals are ionized by solar EUV photons and/or by collisions with solar wind electrons. The mass-loading associated with this ion pick-up is thought to produce a comet-like interaction of the solar wind with Pluto. Within a few thousand kilometers of Pluto the solar wind interaction should lead to a magnetic field pile-up and draping, as it does around other “non-magnetic” bodies such as Venus and comets. The structure of plasma regions and boundaries will be greatly affected by large gyroradii effects and the extensive exosphere. Energetic plasma should disappear from the flow within radial distances of a few thousand kilometers due to charge exchange collisions. An ionosphere should be present close to Pluto with a composition that is determined both by the primary ion production and ion-neutral chemistry. One question discussed in the paper is whether or not the ionosphere has a Venus-like sharply defined ionopause boundary or a diamagnetic cavity such as that found around comet Halley. Simple physical estimates of plasma processes and structures in the collision-dominated region are made in this paper and predictions are made for the New Horizons mission.

Cravens, T. E.; Strobel, D. F.

2015-01-01

134

Properties of Minor Ions in the Solar Wind and Implications for the Background Solar Wind Plasma  

NASA Technical Reports Server (NTRS)

The scope of the investigation is to extract information on the properties of the bulk solar wind from the minor ion observations that are provided by instruments on board NASA space craft and theoretical model studies. Ion charge states measured in situ in interplanetary space are formed in the inner coronal regions below 5 solar radii, hence they carry information on the properties of the solar wind plasma in that region. The plasma parameters that are important in the ion forming processes are the electron density, the electron temperature and the flow speeds of the individual ion species. In addition, if the electron distribution function deviates from a Maxwellian already in the inner corona, then the enhanced tail of that distribution function, also called halo, greatly effects the ion composition. This study is carried out using solar wind models, coronal observations, and ion calculations in conjunction with the in situ observations.

Wagner, William (Technical Monitor); Esser, Ruth

2004-01-01

135

Solar wind thermally induced magnetic fluctuations.  

PubMed

A kinetic description of Alfvén-cyclotron magnetic fluctuations for anisotropic electron-proton quasistable plasmas is studied. An analytical treatment, based on the fluctuation-dissipation theorem, consistently shows that spontaneous fluctuations in plasmas with stable distributions significantly contribute to the observed magnetic fluctuations in the solar wind, as seen, for example, in [S.?D. Bale et al., Phys. Rev. Lett. 103, 211101 (2009)], even far below from the instability thresholds. Furthermore, these results, which do not require any adjustable parameters or wave excitations, are consistent with the results provided by hybrid simulations. It is expected that this analysis contributes to our understanding of the nature of magnetic fluctuations in the solar wind. PMID:24996092

Navarro, R E; Moya, P S; Muñoz, V; Araneda, J A; F-Viñas, A; Valdivia, J A

2014-06-20

136

The solar wind and magnetospheric dynamics  

NASA Technical Reports Server (NTRS)

The dynamic processes involved in the interaction between the solar wind and the earth's magnetosphere are reviewed. The evolution of models of the magnetosphere is first surveyed. The existence of the auroral substorm and the cyclical polar magnetic substorm is evidence that the magnetosphere is a dynamic system. The dynamic changes occurring in the magnetosphere, including erosion of the magnetopause, changes in the size of the polar cap, variations in the flaring angle of the tail, neutral point formation, plasma sheet motions, and the inward collapse of the midnight magnetosphere, are discussed. The cyclical variations of geomagnetic activity are explained in terms of the control of the solar wind-magnetosphere interaction by the north-south component of the interplanetary magnetic field. Present phenomenological models allow prediction of geomagnetic activity from interplanetary measurements, but modeling of detailed magnetospheric processes is still in its infancy.

Russell, C. T.

1974-01-01

137

Bidirectional solar wind electron heat flux events  

Microsoft Academic Search

Normally the approx. >80-eV electrons which carry the solar wind electron heat flux are collimated along the interplanetary magnetic field (IMF) in the direction pointing outward away from the sun. Occasionally, however, collimated fluxes of approx. >80-eV electrons are observed traveling both parallel and antiparallel to the IMF. Here we present the results of a survey of such bidirectional electron

J. T. Gosling; D. N. Baker; S. J. Bame; W. C. Feldman; R. D. Zwickl; E. J. Smith

1987-01-01

138

Turbulence and waves in the solar wind  

SciTech Connect

Studies of turbulence and waves in the solar wind is discussed. Consideration is given to the observations and theory concerning the origin and evolution of interplanetary MHD fluctuations and to the observations, theory, and simulations of compressive fluctuations. Particular attention is given to extrapolations to near-sun and polar fields regions. Results obtained on turbulence at comets and magnetic turbulence of low-frequency waves excited by unstable distributions of ions are discussed. 230 refs.

Roberts, D.A.; Goldstein, M.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

139

Solar Wind Charge Exchange During Geomagnetic Storms  

NASA Technical Reports Server (NTRS)

On March 31st. 2001, a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 RE. The NASA/GSFC Community Coordinated Modeling Center (CCMe) employed a global magnetohydrodynamic (MHD) model to simulate the solar wind-magnetosphere interaction during the peak of this geomagnetic storm. Robertson et aL then modeled the expected 50ft X-ray emission due to solar wind charge exchange with geocoronal neutrals in the dayside cusp and magnetosheath. The locations of the bow shock, magnetopause and cusps were clearly evident in their simulations. Another geomagnetic storm took place on July 14, 2000 (Bastille Day). We again modeled X-ray emission due to solar wind charge exchange, but this time as observed from a moving spacecraft. This paper discusses the impact of spacecraft location on observed X-ray emission and the degree to which the locations of the bow shock and magnetopause can be detected in images.

Robertson, Ina P.; Cravens, Thomas E.; Sibeck, David G.; Collier, Michael R.; Kuntz, K. D.

2012-01-01

140

Western Wind and Solar Integration Study (Fact Sheet)  

SciTech Connect

Initiated in 2007 to examine the operational impact of up to 35% penetration of wind, photovoltaic (PV), and concentrating solar power (CSP) energy on the electric power system, the Western Wind and Solar Integration Study (WWSIS) is one of the largest regional wind and solar integration studies to date. The goal is to understand the effects of variability and uncertainty of wind, PV, and CSP on the grid. In the Western Wind and Solar Integration Study Phase 1, solar penetration was limited to 5%. Utility-scale PV was not included because of limited capability to model sub-hourly, utility-scale PV output . New techniques allow the Western Wind and Solar Integration Study Phase 2 to include high penetrations of solar - not only CSP and rooftop PV but also utility-scale PV plants.

Not Available

2012-09-01

141

CHARGE STATE EVOLUTION IN THE SOLAR WIND. RADIATIVE LOSSES IN FAST SOLAR WIND PLASMAS  

SciTech Connect

We study the effects of departures from equilibrium on the radiative losses of the accelerating fast, coronal hole-associated solar wind plasma. We calculate the evolution of the ionic charge states in the solar wind with the Michigan Ionization Code and use them to determine the radiative losses along the wind trajectory. We use the velocity, electron temperature, and electron density predicted by Cranmer et al. as a benchmark case even though our approach and conclusions are more broadly valid. We compare non-equilibrium radiative losses to values calculated assuming ionization equilibrium at the local temperature, and we find that differences are smaller than 20% in the corona but reach a factor of three in the upper chromosphere and transition region. Non-equilibrium radiative losses are systematically larger than the equilibrium values, so that non-equilibrium wind plasma radiates more efficiently in the transition region. Comparing the magnitude of the dominant energy terms in the Cranmer et al. model, we find that wind-induced departures from equilibrium are of the same magnitude as the differences between radiative losses and conduction in the energy equation. We investigate which ions are most responsible for such effects, finding that carbon and oxygen are the main source of departures from equilibrium. We conclude that non-equilibrium effects on the wind energy equation are significant and recommend that they are included in theoretical models of the solar wind, at least for carbon and oxygen.

Landi, E.; Gruesbeck, J. R.; Lepri, S. T.; Zurbuchen, T. H.; Fisk, L. A. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

2012-10-10

142

Solar wind effects on atmosphere evolution at Venus and Mars  

NASA Technical Reports Server (NTRS)

The weak intrinsic magnetism of Venus and Mars leaves these planets subject to some unique atmospheric loss processes. This paper reviews the ways in which material seems to be removed by the solar wind interaction, including atmospheric ion pickup by the solar wind, bulk removal and outflow of ionospheric plasma, and atmospheric sputtering by pickup ions. The factors in the planets' and sun's histories, such as planetary magnetism, solar luminosity, and past solar wind properties, that must ultimately be folded into considerations of the effects of the solar wind interaction on atmosphere evolution are discussed.

Luhmann, Janet G.; Bauer, S. J.

1992-01-01

143

Helium Abundance and Minor Ion Charge State Variations in the Solar Wind over the Solar Cycle  

NASA Astrophysics Data System (ADS)

Prior studies have shown that the abundance of helium relative to hydrogen in the solar wind is a highly variable quantity. Kasper, et al. (2007) used observations from the Wind spacecraft to show that that the helium abundance in slow solar wind is strongly correlated with sunspot number. During the penultimate solar minimum, helium abundance was a linear function of solar wind speed. However, this dependence vanished as solar activity increased. We extended this study through the recent deep solar minimum and found that the strong correlation between helium abundance and sunspot number for slow solar wind continued. Moreover, as the deep minimum persisted, the helium abundance reached even lower values than observed previously. The strong linear dependence of helium abundance on winds speed also returned during this solar minimum. Motivated by these results, we used data from the ACE spacecraft to determine if the charge states of minor ions, which are strong indicators of coronal temperature, show similar trends. Indeed, the charge states of carbon and oxygen appear to be related to both solar activity and wind speed. Higher charge state ratios were observed for periods of greater activity, but lower ratios were seen as activity decreased. However, while helium abundance increased with solar wind speed, charge state (and thus coronal temperature) decreased with speed. This suggests that during solar minimum slow solar wind originates in cooler plasma. More broadly, these results challenge solar wind acceleration models that link the final speed of the solar wind to a single coronal temperature.

Kiefer, K. K.; Kasper, J. C.; Maruca, B. A.; Stevens, M. L.

2010-12-01

144

Solar wind observations over Ulysses' first full polar orbit  

Microsoft Academic Search

This study examines solar wind plasma and magnetic field observations from Ulysses' first full polar orbit in order to characterize the high-latitude solar wind under conditions of decreasing and low solar activity. By comparing observations taken over nearly all heliolatitudes and two different intervals covering the same radial distances, we are able to separate the radial and latitudinal variations in

D. J. McComas; B. L. Barraclough; H. O. Funsten; J. T. Gosling; E. Santiago-Muñoz; R. M. Skoug; B. E. Goldstein; M. Neugebauer; P. Riley; A. Balogh

2000-01-01

145

Topological Origins of the Slow Solar Wind  

NASA Technical Reports Server (NTRS)

Although the slow solar wind has been studied for decades with both in situ and remote sensing observations, its origin is still a matter of intense debate. In the standard quasi-steady model, the slow wind is postulated to originate near coronal hole boundaries that define topologically well-behaved separatrices between open and closed field regions. In the interchange model, on the other hand, the slow wind is postulated to originate on open flux that is dynamically diffusing throughout the seemingly closed-field corona. We argue in favor of the quasi-steady scenario and propose that the slow wind is due to two effects: First, the open-closed boundary is highly complex due to the complexity of the photospheric flux distribution. Second, this boundary is continuously driven by the transport of magnetic helicity from the closed field region into the open. The implications of this model for the structure and dynamics of the corona and slow wind are discussed, and observational tests of the mode

Antiochos, Spiro

2008-01-01

146

Variations of the solar wind and solar cycle in the last 300 years  

NASA Technical Reports Server (NTRS)

The past history of the solar wind and solar cycle, inferred from records of geomagnetics and aurora, is examined. Records show that the solar wind apparently varied in a systematic manner throughout the period from 1770 to 1857 and that the period around 1810 resembled the 1901 minimum geomagnetic disturbance. Results show that the solar wind and hence the Sun changes on a time scale long compared to a solar cycle and short compared to the Maunder minimum. The inclusion of a study on the solar wind and solar cycle variations for the SCADM mission is discussed.

Feynman, J.; Silverman, S.

1980-01-01

147

ISOTOPIC MASS FRACTIONATION OF SOLAR WIND: EVIDENCE FROM FAST AND SLOW SOLAR WIND COLLECTED BY THE GENESIS MISSION  

SciTech Connect

NASA's Genesis space mission returned samples of solar wind collected over {approx}2.3 years. We present elemental and isotopic compositions of He, Ne, and Ar analyzed in diamond-like carbon targets from the slow and fast solar wind collectors to investigate isotopic fractionation processes during solar wind formation. The solar wind provides information on the isotopic composition for most volatile elements for the solar atmosphere, the bulk Sun and hence, on the solar nebula from which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion in the slow solar wind compared to the fast wind composition by 63.1 {+-} 2.1 per mille for He, 4.2 {+-} 0.5 per mille amu{sup -1} for Ne and 2.6 {+-} 0.5 per mille amu{sup -1} for Ar. The three Ne isotopes suggest that isotopic fractionation processes between fast and slow solar wind are mass dependent. The He/H ratios of the collected slow and fast solar wind samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb drag model reproduces the measured isotopic fractionation between fast and slow wind. Therefore, we apply this model to infer the photospheric isotopic composition of He, Ne, and Ar from our solar wind data. We also compare the isotopic composition of oxygen and nitrogen measured in the solar wind with values of early solar system condensates, probably representing solar nebula composition. We interpret the differences between these samples as being due to isotopic fractionation during solar wind formation. For both elements, the magnitude and sign of the observed differences are in good agreement with the values predicted by the inefficient Coulomb drag model.

Heber, Veronika S.; Baur, Heinrich; Wieler, Rainer [Institute for Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, CH-8092 Zurich (Switzerland); Bochsler, Peter [Physikalisches Institut, Universitaet Bern, Sidlerstasse 5, CH-3012 Bern (Switzerland); McKeegan, Kevin D. [Department of Earth and Space Sciences, University of California Los Angeles, 595 Charles Young Drive East, Box 951567, Los Angeles, CA 90095-1567 (United States); Neugebauer, Marcia [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 (United States); Reisenfeld, Daniel B. [Department of Physics and Astronomy, University of Montana, Missoula, MT 59812 (United States); Wiens, Roger C., E-mail: heber@ess.ucla.edu [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2012-11-10

148

Isotopic Mass Fractionation of Solar Wind: Evidence from Fast and Slow Solar Wind Collected by the Genesis mission  

NASA Astrophysics Data System (ADS)

NASA's Genesis space mission returned samples of solar wind collected over ~2.3 years. We present elemental and isotopic compositions of He, Ne, and Ar analyzed in diamond-like carbon targets from the slow and fast solar wind collectors to investigate isotopic fractionation processes during solar wind formation. The solar wind provides information on the isotopic composition for most volatile elements for the solar atmosphere, the bulk Sun and hence, on the solar nebula from which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion in the slow solar wind compared to the fast wind composition by 63.1 ± 2.1‰ for He, 4.2 ± 0.5‰ amu-1 for Ne and 2.6 ± 0.5‰ amu-1 for Ar. The three Ne isotopes suggest that isotopic fractionation processes between fast and slow solar wind are mass dependent. The He/H ratios of the collected slow and fast solar wind samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb drag model reproduces the measured isotopic fractionation between fast and slow wind. Therefore, we apply this model to infer the photospheric isotopic composition of He, Ne, and Ar from our solar wind data. We also compare the isotopic composition of oxygen and nitrogen measured in the solar wind with values of early solar system condensates, probably representing solar nebula composition. We interpret the differences between these samples as being due to isotopic fractionation during solar wind formation. For both elements, the magnitude and sign of the observed differences are in good agreement with the values predicted by the inefficient Coulomb drag model.

Heber, Veronika S.; Baur, Heinrich; Bochsler, Peter; McKeegan, Kevin D.; Neugebauer, Marcia; Reisenfeld, Daniel B.; Wieler, Rainer; Wiens, Roger C.

2012-11-01

149

Variations of Strahl Properties with Fast and Slow Solar Wind  

NASA Technical Reports Server (NTRS)

The interplanetary solar wind electron velocity distribution function generally shows three different populations. Two of the components, the core and halo, have been the most intensively analyzed and modeled populations using different theoretical models. The third component, the strahl, is usually seen at higher energies, is confined in pitch-angle, is highly field-aligned and skew. This population has been more difficult to identify and to model in the solar wind. In this work we make use of the high angular, energy and time resolution and three-dimensional data of the Cluster/PEACE electron spectrometer to identify and analyze this component in the ambient solar wind during high and slow speed solar wind. The moment density and fluid velocity have been computed by a semi-numerical integration method. The variations of solar wind density and drift velocity with the general build solar wind speed could provide some insight into the source, origin, and evolution of the strahl.

Figueroa-Vinas, Adolfo; Goldstein, Melvyn L.; Gurgiolo, Chris

2008-01-01

150

Interpretation of Solar Wind Ion Composition Measurements from Ulysses  

NASA Technical Reports Server (NTRS)

The ion compositions measured in situ in the solar wind are important since the ion fractions carry information on the plasma conditions in the inner corona. The conditions in the inner corona define the properties of the solar wind plasma flow. Thus, if the ion fraction measurements can be used to unravel some of the plasma parameters in the inner corona, they will provide a valuable contribution to solving the heating and acceleration problem of the solar wind. The ion charge states in the solar wind carry information on electron temperature, electron density and ion flow speed. They are also sensitive to the shape of the electron distribution function. Through carefully modeling the solar wind and calculating the ion fractions predicted for different solar wind conditions, constraints on the electron temperature and ion flow speeds can be placed if the electron density is measured using polarization brightness measurements.

Esser, Ruth

1998-01-01

151

Reflection of solar wind hydrogen from the lunar surface  

NASA Astrophysics Data System (ADS)

The solar wind continuously flows out from the Sun and directly interacts with the surfaces of dust and airless planetary bodies throughout the solar system. A significant fraction of solar wind ions reflect from an object's surface as energetic neutral atoms (ENAs). ENA emission from the Moon was first observed during commissioning of the Interstellar Boundary Explorer (IBEX) mission on 3 December 2008. We present the analysis of 10 additional IBEX observations of the Moon while it was illuminated by the solar wind. For the viewing geometry and energy range (> 250 eV) of the IBEX-Hi ENA imager, we find that the spectral shape of the ENA emission from the Moon is well-represented by a linearly decreasing flux with increasing energy. The fraction of the incident solar wind ions reflected as ENAs, which is the ENA albedo and defined quantitatively as the ENA reflection coefficient RN, depends on the incident solar wind speed, ranging from ~0.2 for slow solar wind to ~0.08 for fast solar wind. The average energy per incident solar wind ion that is reflected to space is 30 eV for slow solar wind and 45 eV for fast solar wind. Once ionized, these ENAs can become pickup ions in the solar wind with a unique spectral signature that reaches 3vSW. These results apply beyond the solar system; the reflection process heats plasmas that have significant bulk flow relative to interstellar dust and cools plasmas having no net bulk flow relative to the dust.

Funsten, H. O.; Allegrini, F.; Bochsler, P. A.; Fuselier, S. A.; Gruntman, M.; Henderson, K.; Janzen, P. H.; Johnson, R. E.; Larsen, B. A.; Lawrence, D. J.; McComas, D. J.; MöBius, E.; Reisenfeld, D. B.; RodríGuez, D.; Schwadron, N. A.; Wurz, P.

2013-02-01

152

The solar magnetic field and the solar wind: Existence of preferred longitudes  

Microsoft Academic Search

Direct measurements of the solar wind speed and the radial component of the interplanetary magnetic field acquired over more than three solar cycles are used to search for signatures of a persistent dependence of solar wind properties on solar longitude. Two methods of analysis are used. One finds the rotation period that maximizes the amplitude of longitudinal variations of both

M. Neugebauer; E. J. Smith; A. Ruzmaikin; J. Feynman; A. H. Vaughan

2000-01-01

153

Elemental and charge state composition of the fast solar wind observed with SMS instruments on WIND  

NASA Technical Reports Server (NTRS)

The elemental composition and charge state distributions of heavy ions of the solar wind provide essential information about: (1) atom-ion separation processes in the solar atmosphere leading to the 'FIP effect' (the overabundance of low First Ionization potential (FIP) elements in the solar wind compared to the photosphere); and (2) coronal temperature profiles, as well as mechanisms which heat the corona and accelerate the solar wind. This information is required for solar wind acceleration models. The SWICS instrument on Ulysses measures for all solar wind flow conditions the relative abundance of about 8 elements and 20 charge states of the solar wind. Furthermore, the Ulysses high-latitude orbit provides an unprecedented look at the solar wind from the polar coronal holes near solar minimum conditions. The MASS instrument on the WIND spacecraft is a high-mass resolution solar wind ion mass spectrometer that will provide routinely not only the abundances and charge state of all elements easily measured with SWICS, but also of N, Mg, S. The MASS sensor was fully operational at the end of 1994 and has sampled the in-ecliptic solar wind composition in both the slow and the corotating fast streams. This unique combination of SWICS on Ulysses and MASS on WIND allows us to view for the first time the solar wind from two regions of the large coronal hole. Observations with SWICS in the coronal hole wind: (1) indicate that the FIP effect is small; and (2) allow us determine the altitude of the maximum in the electron temperature profile, and indicate a maximum temperature of approximately 1.5 MK. New results from the SMS instruments on Wind will be compared with results from SWICS on Ulysses.

Gloeckler, G.; Galvin, A. B.; Ipavich, F. M.; Hamilton, D. C.; Bochsler, P.; Geiss, J.; Fisk, L. A.; Wilken, B.

1995-01-01

154

What Determines the Solar Wind Speed ?  

NASA Astrophysics Data System (ADS)

Recent observations by Interplanetary Scintillation measurements by Nagoya-STEL group (Hirano et al.2003; Kojima et al.2004) show that solar wind speed is well-correlated with B/f, where B is radial magnetic field strength at the solar surface and f is a super-radial expansion factor of open flux tubes. We show that this correlation is nicely explained by dissipation of Alfven waves no matter what types of the wave dissipation processes operate. B determines the input energy flux of Alfven waves and f controls adiabatic loss of the wave energy, so that B/f is an important control parameter which determines the solar wind speed. (reference ) [1] Hirano, M., Kojima, M., Tokumaru, M., Fujiki, K., Ohmi, T., Yamashita, M, Hakamada, K., and Hayashi, K. 2003,, Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract SH21B-0164 [2] Kojima, M., K. Fujiki, M. Hirano, M. Tokumaru, T. Ohmi, and K. Hakamada, 2004, "The Sun and the heliosphere as an Integrated System", Giannina Poletto and Steven T. Suess, Eds. Kluwer Academic Publishers, in press

Suzuki, T. K.; Fujiki, K.; Kojima, M.; Tokumaru, M.; Hirano, M.; Baba, D.; Yamasita, M.; Hakamada, K.

2005-05-01

155

Solar Wind Fractionation — Isotopic and Elemental — and Implications for Solar Compositions and Future Genesis Analyses  

NASA Astrophysics Data System (ADS)

Fractionation between solar wind and the solar photosphere is substantial, both for elements and isotopes. GENESIS measurements are key to understanding these fractionations, which will in turn provide more accurate solar compositions.

Wiens, R. C.; Reisenfeld, D. B.; Heber, V. S.; Burnett, D. S.

2010-03-01

156

Solar Wind: Manifestations of Solar Activity E N CYC LO PE D IA O F AS T R O N O MY AN D AS T R O PHYS I C S Solar Wind: Manifestations of Solar  

E-print Network

Solar Wind: Manifestations of Solar Activity E N CYC LO PE D IA O F AS T R O N O MY AN D AS T R O PHYS I C S Solar Wind: Manifestations of Solar Activity The Sun's outer atmosphere, the corona, is continually heated and expands to create the solar wind. Solar activity waxes and wanes with the 11 yr cycle

Webb, David F.

157

Elemental composition variations in the solar wind: Comparisons between Ulysses and ACE within different solar wind regimes  

NASA Astrophysics Data System (ADS)

The elemental composition of the solar wind is likely established at the base of the corona, a conclusion based on the observed dependence of solar wind abundances on the first ionization potential (FIP) of the elements. Although the plasma conditions within the ecliptic solar wind are highly variable, the elemental composition is less so, and is an indicator of the nature of the solar source. In particular, coronal hole (CH, fast) solar wind tends to have less of a FIP enhancement of the low -FIP elements (e.g., Fe, Mg, Si) than interstream (IS, slow) solar wind. The elemental composition of coronal mass ejections (CMEs) is more variable, but tends to be similar to IS composition. The question we address here is how much does the average composition of the different solar wind regimes vary over the course of the solar cycle and between solar cycles. For the most recent solar cycle, which included the unusually deep and prolonged solar minimum (2006 - 2010) Lepri et al. (2013) have shown measurable drifts in the elemental composition within solar wind regimes using data from the Advanced Composition Explorer (ACE) Solar Wind Ion Composition Spectrometer (SWICS). In contrast, von Steiger and Zurbuchen (2011) have shown using Ulysses SWIC data that the composition of the very fast polar coronal hole flow has remained constant. Here, we extend the Lepri et al. ecliptic analysis to include data from Ulysses, which allows us to expand the analysis to the previous solar cycle (1990 - 2001), as well as check consistency with their recent solar cycle results. (Note that although Ulysses was nominally a polar mission, it spent considerable time at low latitudes as well.) A major driver for this investigation is the Genesis Mission solar wind sample analysis. Namely, was the solar wind sampled by Genesis between late 2001 and early 2004 typical of the solar wind over longer time scales, and hence a representative sample of the long-term solar wind, or was it somehow unique? Our initial findings show that the low-FIP composition measured by ACE/SWICS during the Genesis collection period was, within systematic error, in agreement with that measured by Ulysses (when it was at latitudes < |20°|). Specifically, the measured CH, IS, and CME Fe/O abundances differed between the ACE and Ulysses by 17%, 6.9% and +17%, respectively. The overall solar wind Fe/O ratio differed by only -3.6%. We will give further details on this comparison, and discuss variations in elemental composition over the course of the solar cycle and between cycles.

Pilleri, P.; Reisenfeld, D. B.; Wiens, R. C.

2013-12-01

158

Dispersive shock waves in the solar wind  

NASA Astrophysics Data System (ADS)

Compressional waves in the solar wind propagating over large distances are likely to steepen into shock waves where the increase in the amplitude is balanced by dissipation. Dispersive effects caused by, e.g. Hall currents perpendicular to the ambient magnetic field can influence the generation and propagation of shock waves. In the present study the dispersion is considered weak but in time its importance can grow. When the effect of dispersion is strong enough, it can balance the nonlinear steepening of waves leading to the formation of solitons. The obtained results show that the weak dispersion will alter the amplitude and propagation speed of the shock wave.

Ballai, I.; Forgács-Dajka, E.; Marcu, A.

2007-10-01

159

Velocity shear generation of solar wind turbulence  

NASA Technical Reports Server (NTRS)

A two-dimensional incompressible MHD spectral code is used to show that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ('Alfvenicity') at small scales. It is shown that large-scale shear can nonlinearly produce a cascade to smaller scale fluctuations even when the linear Kelvin-Helmholtz mode is stable, and that a roughly power law inertial range is established by this process. The evolution found is similar to that seen in some other simulations of MHD turbulence.

Roberts, D. A.; Goldstein, Melvyn L.; Matthaeus, William H.; Ghosh, Sanjoy

1992-01-01

160

Gaseous isotope separation using solar wind phenomena  

PubMed Central

A large evacuated drum-like chamber fitted with supersonic nozzles in the center, with the chamber and the nozzles corotating, can separate gaseous fluids according to their molecular weights. The principle of separation is essentially the same as that of the solar wind propagation, in which components of the plasma fluid are separated due to their difference in the time-of-flight. The process can inherently be very efficient, serving as a pump as well as a separator, and producing well over 105 separative work units (kg/year) for the hydrogen/deuterium mixture at high-velocity flows. PMID:16592924

Wang, Chia-Gee

1980-01-01

161

Latitudinal Dependence of Coronal Hole-Associated Fast Solar Wind  

NASA Astrophysics Data System (ADS)

The fast solar wind can have at least two different coronal sources: high-latitude, polar coronal holes (PCH) and low-latitude, equatorial coronal holes (ECH). The in-situ differences in the PCH and ECH winds have not been well studied, nor have the differences in their evolution over the solar cycles. Ulysses' 19 years of observations from 1990 to 2009, combined with ACE observations from 1998 to the present, provide us with measurements of solar wind properties that span two entire solar cycles, which allow us to study the in-situ properties and evolution of the coronal hole-associated solar wind at different latitudes. In this work, we focus on the PCH and ECH solar winds during the minima between solar cycles 22-23 and 23-24. We use data from SWICS, SWOOPS, and VHM/FGM on board Ulysses, and SWICS, SWEPAM, and MAG on board ACE to analyze the proton dynamics, heavy ion composition, elemental abundance, and magnetic field properties of the PCH wind and ECH wind, with a special focus on their differences during the recent two solar minima. We also include the slow and hot, streamer-associated (ST) wind as a reference in the comparison. The comparison of PCH and ECH wind shows that: 1) the in-situ properties of ECH and PCH winds are significantly different during the two solar minima, and 2) the two types of coronal hole-associated solar wind respond differently to changes in solar activity strength from cycle 23 to cycle 24.

Zhao, L.; Landi, E.

2014-05-01

162

Source Regions of Helium Variations in the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

The relative abundances of helium and hydrogen in the solar wind vary on solar cycle time scales as well as with solar wind speed. Kasper et al., 2007 demonstrated further that, during solar minimum, the relative helium abundance correlated with the heliographic latitude of the observer. They also found a linear relationship between the solar wind speed and relative helium abundance for slow (less than 550 km/s) solar wind. Mapping the in situ measurements back to the solar wind source region allows us to relate helium abundance to conditions at the sun. We investigate the coronal sources of the relative helium abundance variations using the WSA-ENLIL model. Improvements to the WSA-ENLIL model have led to better solar wind predictions. Using these improved simulations of the connection between the corona and interplanetary space, we determine the source regions for several time periods during solar minimum when the predicted solar wind speed yields good results as compared with observations. We investigate helium abundance as a function of source region properties such as distance to the current sheet, magnetic expansion factor and the distance to the edge of a coronal hole.

McGregor, S.; Hughes, W.; Kasper, J.; Arge, C.; Odstrcil, D.; Stevens, M.

2008-12-01

163

Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure fluctuations  

E-print Network

Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure observational studies suggest that solar wind dynamic pressure fluctuations can drive magnetosphericFedderMobarry (LFM) global, threedimensional magnetohydrodynamic (MHD) simulations of the solar wind

164

Ulysses Composition, Plasma and Magnetic Field Observations of High Speed Solar wind Streams  

NASA Technical Reports Server (NTRS)

During 1992-3 as the Ulysses spacecraft passed in and out of the southern high speed solar wind stream, the Solar Wind Ion Spectrometer, SWICS made continuous composition and temperature measurements of all major solar wind ions.

Smith, E. J.

1997-01-01

165

Electric conductivity of plasma in solar wind  

NASA Astrophysics Data System (ADS)

One of the most important parameters in MHD description of the solar wind is the electric conductivity of plasma. There exist now two quite different approaches to the evaluation of this parameter. In the first one a value of conductivity taken from the most elaborated current theory of plasma should be used in calculations. The second one deals with the empirical, phenomenological value of conductivity. E.g.: configuration of interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of electrical conductivity of plasma in the solar wind. Knowing the main empirical features of the field configuration, one may estimate the apparent phenomenological value of resistance. The estimations show that the electrical conductivity should be approximately 1013 times smaller than that calculated by Spitzer. It must be noted that the empirical value should be treated with caution. Due to the method of its obtaining it may be used only for 'large-scale' description of slow processes like coronal expansion. It cannot be valid for 'quick' processes, changing the state of plasma, like collisions with obstacles, e.g., planets and vehicles. The second approach is well known in large-scale planetary hydrodynamics, stemming from the ideas of phenomenological thermodynamics. It could formulate real problems which should be solved by modern plasma physics, oriented to be adequate for complicated processes in space.

Chertkov, A. D.

1995-06-01

166

Variance Anisotropy of Solar Wind fluctuations  

NASA Astrophysics Data System (ADS)

Solar wind observations at MHD scales indicate that the energy associated with velocity and magnetic field fluctuations transverse to the mean magnetic field is typically much larger than that associated with parallel fluctuations [eg, 1]. This is often referred to as variance anisotropy. Various explanations for it have been suggested, including that the fluctuations are predominantly shear Alfven waves [1] and that turbulent dynamics leads to such states [eg, 2]. Here we investigate the origin and strength of such variance anisotropies, using spectral method simulations of the compressible (polytropic) 3D MHD equations. We report on results from runs with initial conditions that are either (i) broadband turbulence or (ii) fluctuations polarized in the same sense as shear Alfven waves. The dependence of the variance anisotropy on the plasma beta and Mach number is examined [3], along with the timescale for any variance anisotropy to develop. Implications for solar wind fluctuations will be discussed. References: [1] Belcher, J. W. and Davis Jr., L. (1971), J. Geophys. Res., 76, 3534. [2] Matthaeus, W. H., Ghosh, S., Oughton, S. and Roberts, D. A. (1996), J. Geophys. Res., 101, 7619. [3] Smith, C. W., B. J. Vasquez and K. Hamilton (2006), J. Geophys. Res., 111, A09111.

Oughton, S.; Matthaeus, W. H.; Wan, M.; Osman, K.

2013-12-01

167

Solar wind velocity and temperature in the outer heliosphere  

NASA Technical Reports Server (NTRS)

At the end of 1992, the Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were at heliocentric distances of 56.0, 37.3, and 39.0 AU and heliographic latitudes of 3.3 deg N, 17.4 deg N, and 8.6 deg S, respectively. Pioneer 11 and Voyager 2 are at similar celestial longitudes, while Pioneer 10 is on the opposite side of the Sun. All three spacecraft have working plasma analyzers, so intercomparison of data from these spacecraft provides important information about the global character of the solar wind in the outer heliosphere. The averaged solar wind speed continued to exhibit its well-known variation with solar cycle: Even at heliocentric distances greater than 50 AU, the average speed is highest during the declining phase of the solar cycle and lowest near solar minimum. There was a strong latitudinal gradient in solar wind speed between 3 deg and 17 deg N during the last solar minimum, but this gradient has since disappeared. The solar wind temperature declined with increasing heliocentric distance out to a heliocentric distance of at least 20 AU; this decline appeared to continue at larger heliocentric distances, but temperatures in the outer heliosphere were suprisingly high. While Pioneer 10 and Voyager 2 observed comparable solar wind temperatures, the temperature at Pioneer 11 was significantly higher, which suggests the existence of a large-scale variation of temperature with heliographic longitude. There was also some suggestion that solar wind temperatures were higher near solar minimum.

Gazis, P. R.; Barnes, A.; Mihalov, J. D.; Lazarus, A. J.

1994-01-01

168

Toward a 3D Kinetic Model of the Solar Wind  

NASA Astrophysics Data System (ADS)

The kinetic approach is used to develop a three-dimensional model of the solar wind. As a first approximation, we consider an exospheric model taking into account the effects of the external forces (gravitational and electromagnetic) in a magnetic field decreasing as r-2 where r is the radial distance. The rotation of the Sun deforms the solar streams into the Parker's spiral shape. Using typical solar observations in the solar corona or at 1 AU as boundary conditions, we determine the solar wind characteristics in the meridian and the ecliptic plane from the solar corona to larger distances.

Pierrard, V.; Pieters, M.

2014-05-01

169

The solar wind in the third dimension  

SciTech Connect

For many years, solar-wind physicists have been using plasma and field data acquired near the ecliptic plane together with data on the scintillation of radio sources and remote sensing of structures in the solar corona to estimate the properties of the high-latitude solar wind. Because of the highly successful Ulysses mission, the moment of truth is now here. This paper summarizes the principal agreements and differences between the Ulysses observations and expectations. The speed of the high-latitude solar wind was even greater than anticipated. The strength of the radial component of the interplanetary magnetic field was found to be independent of latitude. The tilt of the heliospheric current sheet caused reverse corotating shocks to be observed to higher latitudes than forward corotating shocks. The energetic particles accelerated in these shocks were detected well poleward of the latitudes at which Ulysses observed the interaction regions themselves. As anticipated, there was a strong flux of outward propagating Alfven waves throughout the polar flow. Those waves were probably largely responsible for the smaller-than-anticipated increase of galactic cosmic rays with increasing latitude. As expected, the charge state or ionization temperature of heavy ions was lower in the polar flow than in low-latitude interstream flows. What was not anticipated was the correlation of elemental abundances with ionization temperatures; the Ulysses data revealed a connection between the first ionization time in the upper chromosphere and the final ionization state in the corona. As expected, transient events were detected to {approx}60 deg. latitude, but the properties of those high latitude transient flows held some surprises. At high latitudes, the speeds of the transient interplanetary plasma clouds were approximately the same as the speed of the ambient plasma and the expansion of the clouds drove forward and reverse shock pairs that had never been seen at low latitudes. At high latitudes, the plasma in interplanetary clouds differed from low-latitude events in that it was not enriched in helium and did not have high ionization temperatures.

Neugebauer, M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

1996-07-20

170

A view of solar magnetic fields, the solar corona, and the solar wind in three dimensions  

Microsoft Academic Search

In the last few years it has been recognized that the solar corona and the solar wind are three-dimensional. The deviations from spherical or even cylindrical symmetry are first-order effects, which are important for a basic description and physical understanding of the coronal expansion. Models of coronal magnetic fields are considered along with the characteristics of large-scale solar structure, the

L. Svalgaard; J. M. Wilcox

1978-01-01

171

Comparative Study of MHD Modeling of the Background Solar Wind  

NASA Astrophysics Data System (ADS)

Knowledge about the background solar wind plays a crucial role in the framework of space-weather forecasting. In-situ measurements of the background solar wind are only available for a few points in the heliosphere where spacecraft are located, therefore we have to rely on heliospheric models to derive the distribution of solar-wind parameters in interplanetary space. We test the performance of different solar-wind models, namely Magnetohydrodynamic Algorithm outside a Sphere/ENLIL (MAS/ENLIL), Wang-Sheeley-Arge/ENLIL (WSA/ENLIL), and MAS/MAS, by comparing model results with in-situ measurements from spacecraft located at 1 AU distance to the Sun (ACE, Wind). To exclude the influence of interplanetary coronal mass ejections (ICMEs), we chose the year 2007 as a time period with low solar activity for our comparison. We found that the general structure of the background solar wind is well reproduced by all models. The best model results were obtained for the parameter solar-wind speed. However, the predicted arrival times of high-speed solar-wind streams have typical uncertainties of the order of about one day. Comparison of model runs with synoptic magnetic maps from different observatories revealed that the choice of the synoptic map significantly affects the model performance.

Gressl, C.; Veronig, A. M.; Temmer, M.; Odstr?il, D.; Linker, J. A.; Miki?, Z.; Riley, P.

2014-05-01

172

Solar wind control of the magnetopause shape, location, and motion  

Microsoft Academic Search

The authors have assembled a data set of 1,821 magnetopause crossings. Separate fits to subsets of this data set determine the magnetopause location as a function of solar wind dynamic pressure and interplanetary magnetic field operation. Solar wind dynamic pressure variations produce self-similar magnetopause motion on time scales of one hour or longer. They verify the pressure balance relationship between

D. G. Sibeck; R. E. Lopez; E. C. Roelof

1991-01-01

173

The Interaction between the Solar Wind and the Earth's Magnetosphere  

Microsoft Academic Search

It is argued in this note that the interplanetary gas causefully be treated as a continuum as far as the interaction between the solar wind and the terrestrial magnestosphere is concerned. On this basis, since the solar wind is highly supersonic near the earth, a collision- free bow shock wave should be a permanent feature of iaterplanetary space on the

W. I. Axford

1962-01-01

174

On WKB expansions for Alfven waves in the solar wind  

NASA Astrophysics Data System (ADS)

The WKB expansion for 'toroidal' Alfven waves in solar wind, which is described by equations of Heinemann and Olbert (1980), is examined. In this case, the multiple scales method (Nayfeh, 1981) is used to obtain a uniform expansion. It is shown that the WKB expansion used by Belcher (1971) and Hollweg (1973) for Alfven waves in the solar wind is nonuniformly convergent.

Hollweg, Joseph V.

1990-09-01

175

Turbulence in the solar wind: Kinetic effects  

NASA Technical Reports Server (NTRS)

Although a casual look at the fluctuating magnetic and velocity fields in the solar wind may be reminiscent of a chaotic and disordered flow, there is, nonetheless. considerable organization and structure in the temporal and spatial evolution of those fluctuations. Much of that evolution is controlled by processes operating on rather large scales for example, in the inner heliosphere, the fluctuations in magnetic and velocity are highly correlated in the sense of outward propagating Alfven waves. This correlation can be destroyed both in time and distance by the velocity gradients present between fast and slow streams and by other nonlinear processes which stir the medium, producing a turbulent cascade of energy from large to small scales. Many aspects of this turbulent evolution can be described using fluid models; however, at some scale the fluid approximation breaks down and a more detailed paradigm is necessary. The breakdown is evident in the power spectrum of magnetic fluctuations at scales approaching the wavelength of ion cyclotron waves. At those scales, as evident in Mariner 10 and other magnetometer data, the spectrum bends over and the fluctuations damp, possibly heating the ambient plasma. Some evidence for heating of the solar wind is present in the Voyager data. Fluid models can be modified to some extent to incorporate aspects of a kinetic treatment. This is done by modifying the dissipation terms in the fluid equations and by including extra terms, such as the Hall term. As the scale lengths of phenomena shrink further and approach the spatial and temporal scales characteristic of electron phenomena, the fluid description must be abandoned altogether and a fully kinetic treatment is required. One example is the generation of Langmuir solitons produced by the electron beams that generate type 3 solar radio bursts.

Goldstein, M. L.

1995-01-01

176

The Solar Wind: Probing the Heliosphere with Multiple Spacecraft  

E-print Network

This paper will focus on several topics best addressed with multiple spacecraft. Solar cycle variations have long been known to occur in solar wind parameters. Initially these variations were observed only near the ecliptic so it was problematic whether these changes occurred because of the changing streamer belt configuration or resulted from a global solar change in the solar wind source. The recent exploration of higher latitudes by the Voyager and Ulysses spacecraft helps to address this question. Similarly, the question of the latitude profiles of solar wind parameters could previously only be addressed by remote sensing methods (eg., interplanetary scintillation). The combination of spacecraft at different latitudes enables us to put together profiles of solar parameters at solar maximum and solar minimum.

John Richardson Center; John D. Richardson

177

INTERPRETING MAGNETIC VARIANCE ANISOTROPY MEASUREMENTS IN THE SOLAR WIND  

SciTech Connect

The magnetic variance anisotropy (A{sub m}) of the solar wind has been used widely as a method to identify the nature of solar wind turbulent fluctuations; however, a thorough discussion of the meaning and interpretation of the A{sub m} has not appeared in the literature. This paper explores the implications and limitations of using the A{sub m} as a method for constraining the solar wind fluctuation mode composition and presents a more informative method for interpreting spacecraft data. The paper also compares predictions of the A{sub m} from linear theory to nonlinear turbulence simulations and solar wind measurements. In both cases, linear theory compares well and suggests that the solar wind for the interval studied is dominantly Alfvenic in the inertial and dissipation ranges to scales of k{rho}{sub i} {approx_equal} 5.

TenBarge, J. M.; Klein, K. G.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA (United States); Podesta, J. J., E-mail: jason-tenbarge@uiowa.edu [Space Science Institute, Boulder, CO (United States)

2012-07-10

178

Magnetohydrodynamic modeling of the solar wind in the outer heliosphere  

SciTech Connect

We present initial results from a solar wind model that accounts for transport of turbulence and treats pickup protons as a separate fluid. The model is based on a numerical solution of the coupled set of mean-field Reynolds-averaged solar wind equations and small-scale turbulence transport equations in the region from 0.3-100 AU. The pickup protons are assumed to be comoving with the solar wind flow and described by separate mass and energy equations. The equations include the terms for energy transfer from pickup protons to solar wind protons and for the plasma heating by turbulent dissipation. The momentum equation contains a term that describes the loss of momentumby the solar wind flow due to the charge exchangewith the interstellar neutral hydrogen.

Usmanov, A. V.; Goldstein, M. L.; Matthaeus, W. H. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Code 673, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2012-05-21

179

OBSERVATION OF FLUX-TUBE CROSSINGS IN THE SOLAR WIND  

SciTech Connect

Current sheets are ubiquitous in the solar wind. They are a major source of the solar wind MHD turbulence intermittency. They may result from nonlinear interactions of the solar wind MHD turbulence or are the boundaries of flux tubes that originate from the solar surface. Some current sheets appear in pairs and are the boundaries of transient structures such as magnetic holes and reconnection exhausts or the edges of pulsed Alfven waves. For an individual current sheet, discerning whether it is a flux-tube boundary or due to nonlinear interactions or the boundary of a transient structure is difficult. In this work, using data from the Wind spacecraft, we identify two three-current-sheet events. Detailed examination of these two events suggests that they are best explained by the flux-tube-crossing scenario. Our study provides convincing evidence supporting the scenario that the solar wind consists of flux tubes where distinct plasmas reside.

Arnold, L.; Li, G.; Li, X. [Department of Physics and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)] [Department of Physics and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Yan, Y., E-mail: gang.li@uah.edu [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Beijing 100012 (China)

2013-03-20

180

The Western Wind and Solar Integration Study Phase 2  

SciTech Connect

The electric grid is a highly complex, interconnected machine, and changing one part of the grid can have consequences elsewhere. Adding wind and solar affects the operation of the other power plants and adding high penetrations can induce cycling of fossil-fueled generators. Cycling leads to wear-and-tear costs and changes in emissions. Phase 2 of the Western Wind and Solar Integration Study (WWSIS-2) evaluated these costs and emissions and simulated grid operations for a year to investigate the detailed impact of wind and solar on the fossil-fueled fleet. This built on Phase 1, one of the largest wind and solar integration studies ever conducted, which examined operational impacts of high wind and solar penetrations in the West.

Lew, D.; Brinkman, G.; Ibanez, E.; Hodge, B. M.; Hummon, M.; Florita, A.; Heaney, M.

2013-09-01

181

Solar wind control of auroral zone geomagnetic activity  

NASA Technical Reports Server (NTRS)

Solar wind magnetosphere energy coupling functions are analyzed using linear prediction filtering with 2.5 minute data. The relationship of auroral zone geomagnetic activity to solar wind power input functions are examined, and a least squares prediction filter, or impulse response function is designed from the data. Computed impulse response functions are observed to have characteristics of a low pass filter with time delay. The AL index is found well related to solar wind energy functions, although the AU index shows a poor relationship. High frequency variations of auroral indices and substorm expansions are not predictable with solar wind information alone, suggesting influence by internal magnetospheric processes. Finally, the epsilon parameter shows a poorer relationship with auroral geomagnetic activity than a power parameter, having a VBs solar wind dependency.

Clauer, C. R.; Mcpherron, R. L.; Searls, C.; Kivelson, M. G.

1981-01-01

182

Solar wind flows associated with hot heavy ions  

NASA Technical Reports Server (NTRS)

Solar wind heavy ion spectra measured with the Vela instrumentation are studied to determine the solar origins of various solar wind structures which contain anomalously high ionization states. The spectra indicating hot coronal conditions were found to occur in 1/7th of all measurements and almost exclusively in postshock flows, nonshock related helium abundance enhancements, or noncompressive density enhancements. The observation of several flared-related helium abundance enhancements suggests that the flare-heated plasma can evolve into the solar wind without producing a noticeable shock at 1 AU.

Fenimore, E. E.

1980-01-01

183

Solar-wind tritium limit and nuclear processes in the solar atmosphere  

NASA Technical Reports Server (NTRS)

Tritium in Surveyor 3 material is measured, and the resulting H-3/H-1 ratio for the solar wind is applied in a solar flare-solar wind relation to investigate the mixing requirements for the solar atmosphere. The flare-wind relation is derived. None of the tritium can be attributed to solar-wind implantation. The upper limit for the H-3/He ratio in the solar wind is 4 times 10 to the minus tenth power and corresponds to a H-3/H-1 limit of 2 times 10 to the minus eleventh power. This limit imposes a requirement on the mixing rate in the solar atmosphere if the H-3 production rate in solar-surface nuclear reactions is greater than 160/sq cm per sec.

Fireman, E. L.; Damico, J.; Defelice, J.

1975-01-01

184

SOLAR WIND HELIUM ABUNDANCE AS A FUNCTION OF SPEED AND HELIOGRAPHIC LATITUDE: VARIATION THROUGH A SOLAR CYCLE  

E-print Network

SOLAR WIND HELIUM ABUNDANCE AS A FUNCTION OF SPEED AND HELIOGRAPHIC LATITUDE: VARIATION THROUGH of the variation of the relative abundance of helium to hydrogen in the solar wind as a function of solar wind that for solar wind speeds between 350 and 415 km sÃ?1 , AHe varies with a clear 6 month periodicity

Richardson, John

185

Forms of Eulerian correlation functions in the solar wind  

E-print Network

Current spacecraft missions such as Wind and ACE can be used to determine magnetic correlation functions in the solar wind. Data sets from these missions can, in principle, also be used to compute so-called Eulerian correlation functions. These temporal correlations are essential for understanding the dynamics of solar wind turbulence. In the current article we calculate these dynamical correlations by using well-established methods. These results are very useful for a comparison with Eulerian correlations obtained from space craft missions.

A. Shalchi

2005-10-27

186

Analysis and Design of a Domestic Solar-Wind Hybrid Energy System for Low Wind Speeds  

E-print Network

A solar-wind hybrid power generation system has been presented here. The application based system illustrated in this paper is designed on the basis of the solar and wind data for areas in Northern India. The power generated by the system is intended for domestic use. The most common source of unconventional power in homes is battery based UPS (Uninterrupted power supply) inverter. The UPS inverter charges the battery with conventional grid power. This system will charge the battery of UPS inverter by using only wind and solar power, which will make the system cost effective and more reliable. The reason for using both solar and wind is that recent studies have proven that combined system can be more productive and consistent and other thing is that neither of them can be used for continuous power generation. In the system illustrated in this paper the solar-wind system provides power periodically which is controlled by electronic methods and a microcontroller is used to monitor the power from both the inputs. The switching action is provided from the microcontroller to the battery charging based on the power received from solar photovoltaic panel and wind generators. In this paper, an efficient system has been presented comprising of solar panel, wind generator, charge controller and charge storage unit (battery). Solar panel is selected as the main input and the wind resource will be used only in the absence of the solar photovoltaic (PV) output.

Vivek Dixit

187

Mass loading of the solar wind by a sungrazing comet  

NASA Astrophysics Data System (ADS)

Collisionless mass loading was suggested by Biermann et al. (1967) for describing interactions between the solar wind and cometary atmospheres. Recent observations have led to an increased interest in coronal mass loading due to sungrazing comets and collisional debris of sunward migrating interplanetary dust particles. In a previous paper, we presented a 3-D MHD model of the solar corona based on the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme code which includes the interaction of dust with the solar wind. We have shown the impact on the solar wind from abrupt mass loading in the coronal region. We apply the model to a sungrazing cometary source, using ejected dust dynamics to generate tail-shaped mass-loading regions. Results help predict the effects on the solar wind acceleration and composition due to sungrazing comets, such as Comet C/2011 W3 (Lovejoy). We show how these effects may be detected by the upcoming Solar Probe Plus Mission.

Rasca, A. P.; Oran, R.; Horányi, M.

2014-08-01

188

The Effects of Solar Wind Structure on Magnetosphere Parameters  

NASA Astrophysics Data System (ADS)

During the ISTP program we demonstrated that in order to understand the magnetospheric response to solar wind and interplanetary magnetic field changes we had to simulate the magnetosphere using actual spacecraft observations as input to our global MHD models [Frank et al., 1995]. In these studies, we assumed that plasmas and fields observed by the spacecraft monitoring the solar wind were homogeneous and that all of the variations seen at the monitor reached the Earth. Although this approach allowed us to obtain qualitative agreement between the simulations and observations made within the magnetosphere, it has often limited our ability to quantitatively assess the validity of the model. In this study we have tested the assumptions made on the solar wind properties and propagation by modeling a magnetic storm on May 24, 2000 using data from five solar wind monitors (ACE, Wind, Imp-8, Geotail and Interball-1). We compare quantitatively the results of the five simulations assuming that each spacecraft was the only solar wind monitor and discuss the topological changes in the magnetospheric configuration caused by the different solar wind inputs. We use these results to assess quantitatively the errors encountered using a single spacecraft and homogeneous solar wind.

Zelenyi, L. M.; Ashour-Abdalla, M.; Coroniti, F. V.; El-Alaoui, M.; Berchem, J.; Walker, R. J.; Peroomian, V.; Zastenker, G. N.

2002-12-01

189

Tracking the Solar Wind Event to Its Source  

NSDL National Science Digital Library

This is an activity about cause and effect. Learners will calculate the approximate travel time of each solar wind event identified in the previous activity in this set to estimate the time at which the disturbance would have left the Sun. Then, they will examine solar images in an attempt to identify the event on the Sun that may have caused the specific solar wind episode. This is Activity 12 of the Space Weather Forecast curriculum.

190

A Floor in the Solar Wind Magnetic Field  

Microsoft Academic Search

Long-term (~130 years) reconstruction of the interplanetary magnetic field (IMF) based on geomagnetic indices indicates that the solar wind magnetic field strength has a ``floor,'' a baseline value in annual averages that it approaches at each 11 yr solar minimum. In the ecliptic plane at 1 AU, the IMF floor is ~4.6 nT, a value substantiated by direct solar wind

L. Svalgaard; E. W. Cliver

2007-01-01

191

Variation of the plasmasheet O+ and H+ density with solar activity and solar wind conditions  

NASA Astrophysics Data System (ADS)

A modulation of the outflow rate of ionospheric ions - among which a high proportion of O+ ions - by solar EUV flux and solar wind conditions has been evidenced in several observational studies. Similarly, the amount of solar wind plasma - mostly H+ ions - penetrating into the magnetosphere also depends on solar wind conditions. We use long-term measurements from the CODIF ion detector onboard the Cluster spacecraft to quantify the resulting O+ and H+ density variations in the plasmasheet. CODIF data are mapped along magnetic field lines to assess the spatial distribution of O+ and H+ ions at the magnetospheric equatorial plane. We make a multi-correlation analysis between the O+ and H+ density and solar wind parameters to investigate their impact on the plasmasheet composition in various regions. An emphasis is placed on the effect of solar wind pressure on the plasmasheet O+ content. Solar wind pressure is expected to affect the energy and momentum input into the ionosphere, which in turn should modulate the ionospheric ion outflow rate and thus the plasmasheet O+ density. On the other hand, when the solar wind pressure increases, the magnetosphere is compressed, resulting in an increase of the O+ and H+ densities independently of the ionospheric outflow rate variation. To infer the actual influence of the solar wind pressure on the plasmasheet O+ content we compare the O+ and H+ density variations associated with solar wind pressure changes with density variations due to magnetospheric compression alone.

Maggiolo, Romain; Kistler, Lynn; Keyser Johan, De; Emmanuel, Gamby

2014-05-01

192

Latitudinal distribution of the solar wind properties in the low-and high-pressure regimes: Wind observations  

E-print Network

Latitudinal distribution of the solar wind properties in the low- and high-pressure regimes: Wind: 29 November 1999 / Revised: 27 March 2000 / Accepted: 6 April 2000 Abstract. The solar wind ®nd that the solar wind properties mainly depend on the modulus jkj. But they also depend on a local

Paris-Sud XI, Université de

193

Electron densities and temperatures in the Venus ionosphere. Effects of solar EUV, solar wind pressure and magnetic field  

Microsoft Academic Search

The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated

R. C. Elphic; C. T. Russell; L. H. Brace

1985-01-01

194

Electron densities and temperatures in the Venus ionosphere Effects of solar EUV, solar wind pressure and magnetic field  

Microsoft Academic Search

The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated

R. C. Elphic; C. T. Russell; L. H. Brace

1985-01-01

195

Microstructures in the Polar Solar Wind: Ulysses  

NASA Technical Reports Server (NTRS)

We find that small (10-200 rP) magnetic decreases comprise a dominant part of the polar solar wind microstructure at Ulysses distances (2.2 AU). These magnetic field dips are almost always bounded by tangential discontinuities, a feature which is not well understood at this time. Hundreds of these events have been examined in detail and a variety of types have been found. These will be described. It is speculated that these structures have been generated by perpendicular heating of ions closer to the Sun and have then been convected to distances of Ulysses. Such structures may be very important for the rapid cross- field diffusion of ions in the polar regions of the heliosphere.

Tsuruyani, Bruce T.; Arballo, J. K.; Galvan, C.; Goldstein, B. E.; Lakhina, G. S.; Sakurai, R.; Smith, E. J.; Neugebauer, M.

1999-01-01

196

Genesis Solar Wind Array Collector Cataloging Status  

NASA Technical Reports Server (NTRS)

Genesis solar wind array collectors were fractured upon landing hard in Utah in 2004. The fragments were retrieved from the damaged canister, imaged, repackaged and shipped to the Johnson Space Center curatorial facility [1]. As of January 2009, the collection consists of 3460 samples. Of these, 442 are comprised into "multiple" sample groupings, either affixed to adhesive paper (177) or collected in jars (17), culture trays (87), or sets of polystyrene vials (161). A focused characterization task was initiated in May 2008 to document the largest samples in the collection. The task consisted of two goals: to document sapphire based fragments greater than 2 cm in one dimension, and to document silicon based fragments greater than 1 cm in one direction.

Burkett, P.J.; Rodriguez, M.C.; Calaway, M.C.; Allton, J.H.

2009-01-01

197

Innovations in Wind and Solar PV Financing  

SciTech Connect

There is growing national interest in renewable energy development based on the economic, environmental, and security benefits that these resources provide. Historically, greater development of our domestic renewable energy resources has faced a number of hurdles, primarily related to cost, regulation, and financing. With the recent sustained increase in the costs and associated volatility of fossil fuels, the economics of renewable energy technologies have become increasingly attractive to investors, both large and small. As a result, new entrants are investing in renewable energy and new business models are emerging. This study surveys some of the current issues related to wind and solar photovoltaic (PV) energy project financing in the electric power industry, and identifies both barriers to and opportunities for increased investment.

Cory, K.; Coughlin, J.; Jenkin, T.; Pater, J.; Swezey, B.

2008-02-01

198

Stationarity of extreme bursts in the solar wind.  

PubMed

Recent results have suggested that the statistics of bursts in the solar wind vary with solar cycle. Here, we show that this variation is basically absent if one considers extreme bursts. These are defined as threshold-exceeding events over the range of high thresholds for which their number decays as a power law. In particular, we find that the distribution of duration times and energies of extreme bursts in the solar wind ? parameter and similar observables are independent of the solar cycle and in this sense stationary, and show robust asymptotic power laws with exponents that are independent of the specific threshold. This is consistent with what has been observed for solar flares and, thus, provides evidence in favor of a link between solar flares and extreme bursts in the solar wind. PMID:25353849

Moloney, N R; Davidsen, J

2014-05-01

199

Wind loading and size effects in RRSRR solar tracking system  

Microsoft Academic Search

The purpose of this work is to investigate wind loading and size effects in RRSRR solar tracking systems. It is the second of a series of papers on the design of an RRSRR solar system. The RRSRR system, which employed double axes for the displacement of its solar panel, enables in concept, a small mechanism to drive large panels or

J. E. Lay; B. E. Eidelberg; R. H. Owen

1980-01-01

200

RESIDUAL ENERGY SPECTRUM OF SOLAR WIND TURBULENCE  

SciTech Connect

It has long been known that the energy in velocity and magnetic field fluctuations in the solar wind is not in equipartition. In this paper, we present an analysis of 5 yr of Wind data at 1 AU to investigate the reason for this. The residual energy (difference between energy in velocity and magnetic field fluctuations) was calculated using both the standard magnetohydrodynamic (MHD) normalization for the magnetic field and a kinetic version, which includes temperature anisotropies and drifts between particle species. It was found that with the kinetic normalization, the fluctuations are closer to equipartition, with a mean normalized residual energy of {sigma}{sub r} = -0.19 and mean Alfven ratio of r{sub A} = 0.71. The spectrum of residual energy, in the kinetic normalization, was found to be steeper than both the velocity and magnetic field spectra, consistent with some recent MHD turbulence predictions and numerical simulations, having a spectral index close to -1.9. The local properties of residual energy and cross helicity were also investigated, showing that globally balanced intervals with small residual energy contain local patches of larger imbalance and larger residual energy at all scales, as expected for nonlinear turbulent interactions.

Chen, C. H. K.; Bale, S. D.; Salem, C. S.; Maruca, B. A., E-mail: chen@ssl.berkeley.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2013-06-20

201

CONDITIONED ANALYSIS OF HIGH-LATITUDE SOLAR WIND INTERMITTENCY  

SciTech Connect

The solar wind is a turbulent medium displaying intermittency. Its intermittent features have been widely documented and studied, showing how the intermittent character is different in fast and slow wind. In this paper, a statistical conditioned analysis of the solar wind intermittency for a period of high-latitude fast solar wind is presented. In particular, the intermittent features are investigated as a function of the Alfvenic degree of fluctuations at a given scale. The results show that the main contribution to solar wind intermittency is due to non-Alfvenic structures, while Alfvenic increments are found to be characterized by a smaller level of intermittency than the previous ones. Furthermore, the lifetime statistics of Alfvenic periods are discussed in terms of a multiscale texture of randomly oriented flux tubes.

D'Amicis, R.; Consolini, G.; Bavassano, B.; Bruno, R. [INAF-Istituto di Astrofisica e Planetologia Spaziali (IAPS), Via del Fosso del Cavaliere 100, 00133, Roma (Italy)

2012-08-10

202

Solar Wind Abundances From Ulysses-SWICS  

NASA Astrophysics Data System (ADS)

We are in the process of performing a thorough revision of the Ulysses-SWICS data analysis method using modern statistical tools and computing power. With this new tool we have reanalyzed the SWICS abundances, in particular the abundance of nitrogen and other elements that are affected by mutual peak overlaps in the raw data. We find that the nitrogen abundance may have been previously underestimated by as much as 30-40% during the four time periods published in 2000 (DOI: 10.1029/1999JA000358) For the other elements only small differences between the new results and those published previously have been found, all well within the stated systematic uncertainty of 20%. We are currently assessing the systematic uncertainty of the new analysis method but estimate that it will be of the order of 10% or even better. Ultimately this will enable us to provide improved solar wind abundances of C, N, O, Ne, Mg, Si, S, and Fe from nearly two decades of Ulysses-SWICS observations at all solar activity levels.

von Steiger, R.; Shearer, P.; Zurbuchen, T.

2013-12-01

203

Comparison of Coronal Streamer Properties to Solar Wind Models For The Last Two Solar Cycle Minima  

NASA Astrophysics Data System (ADS)

We characterize the physical properties of two coronal streamers during Earth/Ulysses quadrature configurations for the previous two solar minimum periods. Comparisons between coronal remote-sensing observations and in situ measurements of solar wind plasma properties are being used to characterize the origin of slow wind streams. In order to investigate slow solar wind heating and acceleration, we compare the measurements with predictions from MHD models. We aim to use the empirical measurements to distinguish between different proposed physical processes for the slow solar wind. This work is supported by NASA grant NNX10AQ58G to the Smithsonian Astrophysical Observatory.

Miralles, Mari Paz; Landi, E.; Cranmer, S. R.; Raymond, J. C.; Cohen, O.; Oran, R.

2013-07-01

204

Little or no solar wind enters Venus' atmosphere at solar minimum.  

PubMed

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum. PMID:18046399

Zhang, T L; Delva, M; Baumjohann, W; Auster, H-U; Carr, C; Russell, C T; Barabash, S; Balikhin, M; Kudela, K; Berghofer, G; Biernat, H K; Lammer, H; Lichtenegger, H; Magnes, W; Nakamura, R; Schwingenschuh, K; Volwerk, M; Vörös, Z; Zambelli, W; Fornacon, K-H; Glassmeier, K-H; Richter, I; Balogh, A; Schwarzl, H; Pope, S A; Shi, J K; Wang, C; Motschmann, U; Lebreton, J-P

2007-11-29

205

Using comet plasma tails to study the solar wind  

NASA Astrophysics Data System (ADS)

The plasma tails of comets have been used as probes of the solar wind for many years, and well before direct solar wind measurements. Now, analyses utilizing the much greater regularity and extent of comet tails imaged from space detail outward solar wind flow much better than was previously possible. These analyses mark the location of the solar wind flow in three-dimensions over time much as do in-situ measurements. Data from comet plasma tails using coronagraphs and heliospheric white-light imagers provide a view closer to the Sun than where spacecraft have ventured to date. These views show that this flow is chaotic and highly variable, and not the benign regular outward motion of a quiescent plasma. While this is no surprise to those who study and characterize the solar wind in situ or use remotely-sensed interplanetary scintillation (IPS) techniques, these spacecraft images provide a visualization of this as never-before possible. Here we summarize the results of an analysis that determines solar wind velocity from multiple comet tails that were observed by the Solar Mass Ejection Imager (SMEI) and also by the inner Heliospheric Imager (HI) on board the Solar Terrestrial Relations Observatory Ahead (STEREOA) spacecraft. Finally, we present results using a similar analysis that measures this same behavior using coronagraph observations in the low corona.

Jackson, B. V.; Buffington, A.; Clover, J. M.; Hick, P. P.; Yu, H.-S.; Bisi, M. M.

2013-06-01

206

Iron charge states in the solar wind as measured by SMS on Wind  

NASA Technical Reports Server (NTRS)

The Wind spacecraft was launched in November 1994. In the first half of 1995 it was in the interplanetary medium upstream of the Earth. The Solar Wind and Suprathermal Ion Composition Experiment (SMS) on Wind consists of three sensors, the Solar Wind Ion Composition Spectrometer (SWICS), the Suprathermal Ion Composition Spectrometer (STICS), and the high mass resolution spectrometer (MASS). All three instruments utilize electrostatic deflection combined with time-of-flight measurement. The data from these three sensors allows the determination of the ionic composition of the solar wind in a variety of solar wind conditions over a large energy/charge range (0.5 to 230 keV/e). We have examined the Wind database for time periods conducive to observing solar wind iron. With the high mass resolution of the MASS spectrometer (M/Delta-M greater than 100) iron is easily identified while the electrostatic deflection provides information concerning the mass/charge distribution. We present here the relative abundance of iron charge states in the solar wind near 1 AU.

Galvin, A. B.; Cohen, C. M. S.; Ipavich, F. M.; Gloeckler, G.; Hamilton, D. C.; Chotoo, K.; Balsiger, H.; Sheldon, R.

1995-01-01

207

Quantifying shear-induced wave transformations in the solar wind  

E-print Network

The possibility of velocity shear-induced linear transformations of different magnetohydrodynamic waves in the solar wind is studied both analytically and numerically. A quantitative analysis of the wave transformation processes for all possible plasma-$\\beta$ regimes is performed. By applying the obtained criteria for effective wave coupling to the solar wind parameters, we show that velocity shear-induced linear transformations of Alfv\\'en waves into magneto-acoustic waves could effectively take place for the relatively low-frequency Alfv\\'en waves in the energy containing interval. The obtained results are in a good qualitative agreement with the observed features of density perturbations in the solar wind.

Grigol Gogoberidze; Andria Rogava; Stefaan Poedts

2007-03-20

208

Modulation of the solar wind velocity and density by Mercury  

NASA Astrophysics Data System (ADS)

To study the variations in the solar wind velocity during inferior conjunctions of Mercury and Earth, we analyzed 54 events in the period 1995-2012 by the superimposed epoch method. We have found a noticeable increase in the velocity both before and after the conjunctions as well as decrease in the velocity within 3-4 days after them (Mercury's “shadow”). Variations of the solar wind density in 1997-2013 show a similar character, but their dispersion is substantially larger than for the velocity. The results obtained might be used to analyze variations and to improve a forecast of the solar wind velocity and density.

Nikulin, I. F.

2014-09-01

209

The solar wind interaction with unmagnetized planets - A tutorial  

NASA Technical Reports Server (NTRS)

The interaction of the solar wind with the Venus ionosphere induces currents which can substantially exclude the solar wind and IMF from the dayside ionosphere beneath the 'ionopause', where ionosphere thermal pressure equals incident solar wind dynamic pressure. The field then diffuses through the ionopause with increasing speed at decreasing altitudes, and is weakest in the subpolar region. Once within the ionopause, the magnetic field is redistributed by ionospheric convection, and then decays at low altitudes via collisional dissipation of the associated currents. The maximum ionospheric field magnitudes observed, of about 150 nT, furnish magnetic pressures exceeding the ionospheric thermal pressure by a factor of about 3.

Luhmann, J. G.

1990-01-01

210

The relationship between Saturn kilometric radiation and the solar wind  

NASA Technical Reports Server (NTRS)

Voyager spacecraft radio, interplanetary plasma, and interplanetary magnetic field data are used to show that large amplitude fluctuations in the power generated by the Saturn kilometric radio emission are best correlated with solar wind ram pressure variation. In all, thirteen solar wind quantities previously found important in driving terrestrial magnetospheric substorms and other auroral processes were examined for evidence of correlations with the Saturn radio emission. The results are consistent with hydromagnetic wave or eddy diffusion processes driven by large scale solar wind pressure changes at Saturn's dayside magnetopause.

Desch, M. D.; Rucker, H. O.

1983-01-01

211

The relationship between Saturn kilometric radiation and the solar wind  

NASA Technical Reports Server (NTRS)

Voyager spacecraft radio, interplanetary plasma, and interplanetary magnetic field data are used to show that large amplitude fluctuations in the power generated by the Saturn kilometric radio emission are best correlated with solar wind ram pressure variation. In all, thirteen solar wind quantities previously found important in driving terrestrial magnetospheric substorms and other auroral processes were examined for evidence of correlations with the Saturn radio emission. The results are consistent with hydromagnetic wave or eddy diffusion processes driven by large scale solar wind pressure changes at Saturn's dayside magnetopause. Previously announced in STAR as N83-24445

Desch, M. D.; Rucker, H. O.

1983-01-01

212

Diurnal, semiannual, and solar cycle variations of solar wind–magnetosphere–ionosphere coupling  

Microsoft Academic Search

Using the Km index, the F10.7 index, and solar wind data from 1965 to 1996, we have examined the variations for the efficiency of solar wind–magnetosphere–ionosphere (SMI) coupling. It is found that the efficiency of SMI coupling depends on the total solar zenith angle, which is defined by the sum of cosine of the solar zenith angles at the northern

T. Nagatsuma

2006-01-01

213

X-rays from Solar Wind Charge Exchange at Mars  

E-print Network

Wherever the solar wind meets a neutral atmosphere, X-rays are emitted by a charge exchange process between the neutrals and heavy solar wind ions. A hybrid simulation of the solar wind-Mars interaction and a test particle simulation of heavy ion trajectories near Mars is used to compute the contribution from charge exchange processes to the X-ray emission from Mars. The results are compared to observations of X-rays from Mars made with the Chandra telescope [1]. The comparison indicates that the solar wind charge exchange process is a likely candidate for the production of the X-ray halo at Mars. The calculations were performed in three steps. First the solar wind parameters were estimated. We compare the results of two different solar wind parameter estimates: A ballistic model based on data obtained by the WIND spacecraft, and an MHD model using input from interplanetary scintillation measurements. The second step was running a hybrid simulation of the interaction between the solar wind and Mars to obtain the electric and magnetic fields around Mars. As a third step a test particle simulation was run, calculating the trajectories of heavy solar wind ions in the electric and magnetic fields that were obtained from the hybrid simulation. The X-ray emission density was saved on a grid for each time step of the test particle simulation. A hundred thousand trajectories were calculated for each of the ion species O 7+, C 6+, O 6+, O 8+, Mg 10+, Mg 9+, Si 9+, N 6+, C 5+, Ne 8+, Fe 9+, S 9+,

H. Gunell; M. Holmström; E. Kallio; P. Janhunen; K. Dennerl

214

Solar wind proton flux extremes and their association with pseudostreamers  

NASA Astrophysics Data System (ADS)

Proton flux, as defined by the product of proton number density and proton speed, while exhibiting remarkable constancy across heliographic latitudes from pole to equator as measured by the Ulysses spacecraft, nevertheless showed obvious departure from this constancy for some mid-latitude wind and extended to high heliomagnetic latitudes during the recent two solar minima. We examine the solar wind exclusive of ICMEs from Ulysses and ACE observations, to analyze the solar wind in-situ data exhibiting extremes in proton flux. We first find these extreme-proton-flux winds generally originate in latitudes middle-distant from the heliospheric current sheet (HCS), and they have relatively slower speed than the bulk of the solar wind. Then we map the in-situ ACE observations in Carrington rotation (CR) 1997 back to the solar surface by using the Potential-Field-Source-Surface (PFSS) model, in order to consider the coronal properties at the extreme-proton-flux wind sources. We find there is a clear association between these extreme-proton-flux solar wind and the mid-latitude coronal holes and "pseudostreamer" structures.

Zhao, Liang; Gibson, Sarah E.; Fisk, Lennard A.

2013-06-01

215

Solar Wind Turbulence A Study of Corotating Interaction Regions at 1 AU  

E-print Network

Solar Wind Turbulence A Study of Corotating Interaction Regions at 1 AU Je rey A. Tessein Department of Physics University of New Hampshire Durham, NH 03824 May 15, 2009 #12;Abstract The solar wind's rotation and the variability in the source of the solar wind, fast moving wind can crash into slow wind

216

Utility scale hybrid wind–solar thermal electrical generation: A case study for Minnesota  

Microsoft Academic Search

The performance of a hybrid wind–solar power plant in southwestern Minnesota is modeled for a 2-yr period using hourly wind and solar insolation data. The wind portion of the plant consists of four interconnected wind farms within a radius of 90km. The solar component of the plant is a parabolic trough solar thermal electric generating system using a heat transfer

J. P. Reichling; F. A. Kulacki

2008-01-01

217

Shock Acceleration of the Energetic Particle Background in the Solar Wind David T. Sodaitis  

E-print Network

Shock Acceleration of the Energetic Particle Background in the Solar Wind David T. Sodaitis Physics the Lee (1983) theory. 1. Introduction to the Solar Wind The solar wind consists of a stream of ions greater than the restraining force of gravity, the solar wind is driven outward. For those of us residing

218

Altered solar wind -magnetosphere interaction at low Mach numbers: coronal mass ejections  

E-print Network

1 Altered solar wind - magnetosphere interaction at low Mach numbers: coronal mass ejections Benoit fundamental alterations of the solar wind ­ magnetosphere interaction that occur during low Mach number solar wind. We first show that low Mach number solar wind conditions are often characteristic of coronal mass

Boyer, Edmond

219

Improved Method for Specifying Solar Wind Speed Near the Sun Charles N. Arge*  

E-print Network

Improved Method for Specifying Solar Wind Speed Near the Sun Charles N. Arge* , Dusan Odstrcil solar wind flow speed near the Sun (~0.1 AU) us- ing a set of three simple inter-linked coronal/solar wind models. In addition to magnetic field expansion factor, solar wind speed also appears

California at Berkeley, University of

220

Effects of solar wind dynamic pressure on the ionospheric fluence during the 31 August 2005 storm  

E-print Network

Effects of solar wind dynamic pressure on the ionospheric O+ fluence during the 31 August 2005 solar wind data is contrasted against a case where the solar wind dynamic pressure (Pdyn with the solar wind dynamic pressure. Additionally, changes in Pdyn affect the downward Poynting flux only

221

Narrow coronal holes in Yohkoh soft X-ray images and the slow solar wind  

E-print Network

Narrow coronal holes in Yohkoh soft X-ray images and the slow solar wind C.N. Arge , K.L. Harvey of this phenomenon, and have found several candidates. From observations of the associated solar wind, and from modeling, we find these regions to be sources of slow solar wind. INTRODUCTION The solar wind arguably

Hudson, Hugh

222

Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions: Ulysses Observations  

E-print Network

Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions: Ulysses Observations D it observed solar wind shears from the incursions of high-latitude fast solar wind toward the low-latitude slow solar wind. We look for nearly radial field orientations commonly observed in rarefaction regions

Sanahuja, Blai

223

Are energetic electrons in the solar wind the source of the outer radiation belt?  

E-print Network

Are energetic electrons in the solar wind the source of the outer radiation belt? Xinlin Li,1 D. N. Mewaldt6 Abstract. Using data from WIND, SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer the correlation of en- ergetic electrons in the 20-200 keV range in the solar wind and of high speed solar wind

Li, Xinlin

224

Are energetic electrons in the solar wind the source of the outer radiation belt?  

Microsoft Academic Search

Using data from WIND, SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), and the Los Alamos National Laboratory (LANL) sensors onboard geostationary satellites, we investigate the correlation of energetic electrons in the 20-200 keV range in the solar wind and of high speed solar wind streams with relativistic electrons in the magnetosphere to determine whether energetic electrons in the solar wind

Xinlin Li; D. N. Baker; M. Temerin; D. Larson; R. P. Lin; G. D. Reeves; M. Looper; S. G. Kanekal; R. A. Mewaldt

1997-01-01

225

Title: Feasibility Study for 20 MW Hybrid Solar and Wind Park in Colombia  

E-print Network

familiar with solar and wind technologies, but also Colombian energy and environmental regulations. He has development team is experienced in Latin American solar and wind energy development and solar and wind resource assessment. The study includes: · Conduct sophisticated solar and wind energy modeling

Johnson, Eric E.

226

Response of the magnetic field in the geosynchronous orbit to solar wind dynamic pressure pulses  

E-print Network

Response of the magnetic field in the geosynchronous orbit to solar wind dynamic pressure pulses C of the relative change of solar wind dynamic pressure (dPd/Pd) increases, the rate of geosynchronous magnetic and the solar wind Pd, and showed that increases in the solar wind Pd and the geosynchronous magnetic field

Richardson, John

227

Sources of the solar wind - the heliospheric point of view  

NASA Astrophysics Data System (ADS)

The solar wind as observed in the heliosphere has several properties that can be interpreted as signatures of conditions and processes at its source in the solar atmosphere. Traditionally it has been customary to distinguish between solar wind types solely based on its speed, "fast" and "slow" wind. Over the last couple of decades new instruments resolving not only the main constituents (protons and alpha particles) but also heavy ions from C to Fe have added new observables, in particular the charge state and elemental composition of these ions. The charge states are indicators of the coronal temperature at the source region; they have confirmed that the "fast" wind emanates from the relatively cool coronal hole regions, while the "slow" wind originates from hotter sources such as the streamer belt and active regions. Thus they are more reliable indicators of solar wind source than the speed alone could be because they readily discriminate between "fast" wind from coronal holes and fast coronal mass ejections (CMEs). The elemental composition in the solar wind compared to the abundances in the photosphere shows a typical fractionation that depends on the first ionization potential (FIP) of the elements. Since that fractionation occurs beneath the corona, in the chromosphere, its strength is indicative of the conditions in that layer. While the "fast" wind is very similar to photospheric composition, the fractionation of the "slow" wind and of CMEs is higher and strongly variable. We will review the observations of the SWICS composition instruments on both the ACE and the Ulysses missions, which have made composition observations between 1 and 5 AU and at all latitudes in the heliosphere over the last two decades. Specifically, analysis of the "slow" wind observations at all time scales, from hours to complete solar cycles, will be used to better characterize its source regions.

Von Steiger, Rudolf; Shearer, Paul; Zurbuchen, Thomas

228

Ionospheric mid-latitude response to solar wind discontinuities  

NASA Astrophysics Data System (ADS)

We have compiled a database of 356 discontinuities detected by both the Advanced Composition Explorer ACE) and Cluster satellites in the solar wind between 2001-2012 and analyzed their ionospheric response. Each discontinuity of the data base is defined by a change of at least 5 nT in less than 5 min in one or more components of the interplanetary magnetic field (IMF). The discontinuities are observed in January-April every year, when Cluster enters the solar wind. The ionospheric effects of solar wind discontinuities are investigated by checking the variations of critical frequencies foF2, the heights of the F layer and the ionospheric plasma dynamics recorded using ground measurement with a time resolution of 15 minutes from mid-latitude digisondes located in Czech Republic. The time delay between solar wind input and the ionospheric response is analyzed using the characteristics and the shape of the ionograms. The geoeffectiveness of the solar wind discontinuities is expressed as correlation between key plasma parameters (e,g, the solar wind velocity, magnetic jump across the discontinuity) and the ionospheric variations. Solar cycle effects are also discussed.

Munteanu, Costel; Mosna, Zbysek; Kouba, Daniel; Echim, Marius

2013-04-01

229

Stationarity of magnetohydrodynamic fluctuations in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind research and studies of charged particle propagation often assume that the interplanetary magnetic field represents a stationary random process. The extent to which ensemble averages of the solar wind magnetic fields follow the asymptotic behavior predicted by the ergodic theorem was investigated. Several time periods, including a span of nearly two years, are analyzed. Data intervals which span many solar rotations satisfy the conditions of weak stationarity if the effects of solar rotation are included in the asymptotic analysis. Shorter intervals which include a small integral number of interplanetary sectors also satisfy weak stationarity. The results are illustrated using magnetometer data from the ISEE-3, Voyager and IMP spacecraft.

Matthaeus, W. H.; Goldstein, M. L.

1982-01-01

230

Transient flows of the solar wind associated with small-scale solar activity in solar minimum  

NASA Astrophysics Data System (ADS)

The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project n° 284461, www.eheroes.eu).

Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

231

He abundance variations in the solar wind: Observations from Ulysses  

SciTech Connect

The Ulysses mission is providing the first opportunity to observe variations in solar wind plasma parameters at heliographic latitudes far removed from the ecliptic plane. We present an overview of the solar wind speed and the variability in helium abundance, [He] data on [He] in six high latitude coronal mass ejections (CMEs), and a superposed epoch analysis of [He] variations at the seven heliospheric current sheet (HCS) crossings made during the rapid-latitude-scan portion of the mission. The differences in the variability of the solar wind speed and [He] in high latitude and equatorial regions are quite striking. Solar wind speed is generally low but highly variable near the solar equator, while at higher latitudes the average speed is quite high with little variability. [He] can vary over nearly two decades at low solar latitudes, while at high latitudes it varies only slightly. In contrast to the high [He] that is commonly associated with CMEs observed in the ecliptic, none of the six high-speed CMEs encountered at high southern heliographic latitudes showed any significant variation in helium content. A superposed epoch analysis of the [He] during all seven HCS crossings made as Ulysses passed from the southern to northern solar hemisphere shows the expected [He] minimum near the crossing and a broad region of low [He] around the crossing time. We discuss how our solar wind [He] observations may provide an accurate measure of the helium composition for the entire convective zone of the Sun.

Barraclough, B.L.; Gosling, J.T.; Phillips, J.L.; McComas, D.J.; Feldman, W.C. [Los Alamos National Lab., NM (United States); Goldstein, B.E. [California Inst. of Technology, Pasadena, CA (United States). Jet Propulsion Lab.

1995-09-01

232

76 FR 73783 - Residential, Business, and Wind and Solar Resource Leases on Indian Land  

Federal Register 2010, 2011, 2012, 2013

...CFR Part 162 Residential, Business, and Wind and Solar Resource Leases on Indian Land...1076-AE73 Residential, Business, and Wind and Solar Resource Leases on Indian Land...residential leases, business leases, wind resource evaluation and development...

2011-11-29

233

Measurements of Core Electron Heating in Solar Wind Reconnection Exhausts  

NASA Astrophysics Data System (ADS)

Using electron measurements from the Wind/3DP Electron Electrostatic Analyzer and thermal noise spectra from the Wind/WAVES Thermal Noise Receiver, we have developed a technique which (a) corrects electron distribution functions for spacecraft potential and (b) isolates and fits the thermal core electron population in the solar wind. From these fits, we can accurately determine the rate of core electron heating during solar wind reconnection exhausts. We present several examples of observed reconnection events, showing that core electron heating occurs within some exhaust regions but is absent in other events. These examples serve as the starting point for a statistical study, which will determine the dependence of electron heating on exhaust region boundary conditions and solar wind plasma parameters. Results from this study will be compared to recent results from the magnetopause, in an effort to establish a universal relationship between reconnection exhaust parameters and electron heating.

Pulupa, M.; Salem, C. S.; Phan, T.; Bale, S. D.; Gosling, J. T.

2013-12-01

234

Solar wind stream structure at large heliocentric distances Pioneer observations  

NASA Technical Reports Server (NTRS)

Time profiles and histograms of plasma data from Pioneers 10 and 11 are examined for the period between 1975 and 1983. During this time, Pioneer 10 traveled between a heliocentric distance of 8.7 and 30.4 AU. The velocity structure of the solar wind at these heliocentric distances is found to have one of two distinct forms: approximately 70 percent of the time the solar wind has a nearly flat velocity profile. Occasionally, this flat velocity profile is accompanied by quasi-periodic variations in density and in thermal speed consistent with the concept that the 'corotating interaction regions' which are produced by the interaction of high- and low-speed streams at intermediate heliocentric distances are replaced by 'pressure regions' in the outer heliosphere. The remaining 30 percent of the time the solar wind is marked by large (50-200 km/s) long-term (30-120 days) shifts in the average solar wind velocity.

Gazis, P. R.

1987-01-01

235

Ion Trajectory Simulations of the Genesis Solar Wind Concentrator Performance  

NASA Astrophysics Data System (ADS)

We describe improvements to Genesis Solar Wind Concentrator computer simulation, compare results to analyses made on the Concentrator target, and use these to predict the utility of the Concentrator target for analyses of other elements and isotopes.

Wiens, R. C.; Olinger, C. T.; Reisenfeld, D.

2011-03-01

236

Western Wind and Solar Integration Study Phase 2 (Fact Sheet)  

SciTech Connect

This is one-page, two-sided fact sheet presents high-level summary results of the Western Wind and Solar Integration Study Phase 2, which examined operational impacts of high penetrations of variable renewable generation in the West.

Not Available

2013-09-01

237

Western Wind and Solar Integration Study: Phase 2 (Presentation)  

SciTech Connect

This presentation summarizes the scope and results of the Western Wind and Solar Integration Study Phase 2, which examined operational impacts of high penetrations of variable renewable generation in the West.

Lew, D.; Brinkman, G.; Ibanez, E.; Lefton, S.; Kumar, N.; Venkataraman, S.; Jordan, G.

2013-09-01

238

Saturn radio emission and the solar wind - Voyager-2 studies  

NASA Technical Reports Server (NTRS)

Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyze the relationship between parameters of the solar wind/interplanetary medium and the nonthermal Saturn radiation. Solar wind and interplanetary magnetic field properties were combined to form quantities known to be important in controlling terrestrial magnetospheric processes. The Voyager 2 data set used in this investigation consists of 237 days of Saturn preencounter measurements. However, due to the immersion of Saturn and the Voyager 2 spacecraft into the extended Jupiter magnetic tail, substantial periods of the time series were lacking solar wind data. To cope with this problem a superposed epoch method (CHREE analysis) was used. The results indicate the superiority of the quantities containing the solar wind density in stimulating the radio emission of Saturn - a result found earlier using Voyager 1 data - and the minor importance of quantities incorporating the interplanetary magnetic field.

Desch, M. D.; Rucker, H. O.

1985-01-01

239

Ion Beam Instabilities in Solar Wind Reconnection Exhaust  

NASA Astrophysics Data System (ADS)

Observations of the solar wind proton velocity distribution using the Wind faraday cups were studied during inside of and near previously published magnetic reconnection exhausts. We have attempted to test the hypothesis that interpenetrating ion beams in the solar wind can be driven by the reconnection process. The beam and core within the solar wind were fit as two bi-Maxwellian distributions and their velocities compared to Alfvén wave velocity and inflow speed. The differential flow between the beam and the core was found to be mostly in the range of Alfvénic to super Alfvénic instead of reflecting the inflow speed. Further analysis revealed that these beam configurations are frequently unstable and excite parallel-propagating plasma modes. This research was supported by the NSF grant for the Solar Physics REU Program at the Smithsonian Astrophysical Observatory (AGS-1263241).

Kristensen, H.; Stevens, M. L.; Verscharen, D.; Kasper, J. C.

2013-12-01

240

Jupiter's Magnetospheric Dynamics: Evidence of Solar Wind Driving?  

NASA Astrophysics Data System (ADS)

Jupiter's magnetosphere is a highly dynamic environment. Analysis of magnetic field and particle measurements collected by the Galileo spacecraft in Jupiter's magnetotail has shown evidence of hundreds of reconnection events [3,7]. It has long been suggested that Jupiter's magnetospheric dynamics are controlled primarily by rotational stresses, rather than by the solar wind, due to the rapid planetary rotation period and large spatial scales [6]. Such an internally-driven mass loading and release process is expected to occur with a typical 2-4 day recurrence period. Quasi-periodic behavior, suggestive of reconnection, has been observed on a similar time scale intermittently in several data sets, including magnetic field dipolarizations, flow bursts, and the hectometric radio emissions [4,5]. However, several questions remain unanswered, including why some specific spacecraft orbits were particularly dynamic (such as Galileo orbits G2 and G8), why the periodicity is not always observed, and why the characteristic time scale varies from ~1 to 7 days when the periodicity is present. One possible explanation is that the periodic magnetospheric reconfigurations may be modulated by the solar wind, as seen in global MHD simulations of plasmoid release and other dynamics in the magnetospheres of both Jupiter and Saturn [1,2]. In this study we use the Michigan mSWiM propagated solar wind MHD model to estimate the solar wind conditions upstream of Jupiter. We make use of event association tests to determine whether there is a statistical link between Jovian reconnection events and solar wind compressions or other disturbed solar wind conditions. We also consider the possibility that varying solar wind conditions may alter the characteristic periodicity in Jupiter's magnetosphere. For example, we perform a Lomb periodogram analysis on the solar wind model data during both quiet intervals and intervals when quasi-periodic behavior is observed in the in situ magnetospheric data.

Vogt, M. F.; Bunce, E. J.; Kronberg, E. A.

2014-04-01

241

Modulation of the Solar Wind Velocity by Mercury  

E-print Network

To study the variations in the solar wind velocity during inferior conjunctions of Mercury and Earth, we analyzed 54 events in the period 1995 to 2012 by the superimposed epoch method. We have found a noticeable increase in the velocity both before and after the conjunctions as well as decrease in the velocity within 3-4 days after them, which seems to be associated with Mercury's "shadow". The results obtained might be used to improve a forecast of the solar wind velocity.

Nikulin, Igor F

2013-01-01

242

Solar Wind and Magnetosphere Interaction Lab: A Cereal Analogy  

NSDL National Science Digital Library

This open-ended laboratory activity is useful in demonstrating how solar wind particles are deflected by the Earth's magnetosphere and how charged particles are aligned within it. After this lesson, students should be able to discuss and describe the components of solar wind particles, explain why the magnetosphere and ionosphere protect the Earth, and explain how moving particles behave (and align) in a magnetic field. Additional links lead to background material, standards, and assessment.

243

The Turbulent Origin of the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

We report on preliminary analyses of early solar wind turbulence via heliospheric imaging: both the brightness structure function in the STEREO-A HI-1 field of view and paths taken by individual boli of comet-tail material in the solar wind. The analyses are complementary and preliminary results indicate that turbulent processing is underway even within the early HI-1 field of view (as low as 20-30 Rs).

DeForest, Craig; Matthaeus, Bill; Howard, Tim A.

2014-06-01

244

Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind  

NASA Technical Reports Server (NTRS)

The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

Burlaga, L. F.; Barouch, E.

1974-01-01

245

The Character of the Solar Wind, Surface Interactions, and Water  

NASA Technical Reports Server (NTRS)

We discuss the key characteristics of the proton-rich solar wind and describe how it may interact with the lunar surface. We suggest that solar wind can be both a source and loss of water/OH related volatiles, and review models showing both possibilities. Energy from the Sun in the form of radiation and solar wind plasma are in constant interaction with the lunar surface. As such, there is a solar-lunar energy connection, where solar energy and matter are continually bombarding the lunar surface, acting at the largest scale to erode the surface at 0.2 Angstroms per year via ion sputtering [1]. Figure 1 illustrates this dynamically Sun-Moon system.

Farrell, William M.

2011-01-01

246

Potential for Development of Solar and Wind Resource in Bhutan  

SciTech Connect

With support from the U.S. Agency for International Development (USAID), the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) produced maps and data of the wind and solar resources in Bhutan. The solar resource data show that Bhutan has an adequate resource for flat-plate collectors, with annual average values of global horizontal solar radiation ranging from 4.0 to 5.5 kWh/m2-day (4.0 to 5.5 peak sun hours per day). The information provided in this report may be of use to energy planners in Bhutan involved in developing energy policy or planning wind and solar projects, and to energy analysts around the world interested in gaining an understanding of Bhutan's wind and solar energy potential.

Gilman, P.; Cowlin, S.; Heimiller, D.

2009-09-01

247

Dissipation of Turbulence in the Solar Wind  

NASA Technical Reports Server (NTRS)

I will describe the first three-dimensional (3-D) dispersion relations and wavenumber spectra of magnetic turbulence in the solar wind at sub-proton scales. The analysis takes advantage of the short separations of the Cluster spacecraft (d/sim approx.200 km) to apply the {it k}-filtering technique to the frequency range where the transition to sub-proton scales occurs. The dispersion diagrams show unambiguously that the cascade is carried by highly oblique Kinetic Alfven Wave with \\omega\\leq 0.1\\omega_{ci} in the plasma rest frame down to k_\\perp\\rho_i \\sim 2. The wavenumber spectra in the direction perpendicular to the mean magnetic field consists of two ranges of scales separated by a breakpoint in the interval [0.4,1] k_\\perp \\rho_i. Above the breakpoint, the spectra follow the Kolmogorov scaling k_\\perp^{-1.7}, consistent with existing theoretical predictions. Below the breakpoint, the spectra steepen to \\sim k_\\perp^{-4.5}. We conjecture that the turbulence undergoes a {\\it transition-range}, where part of energy is dissipated into proton heating via Landau damping, and the remaining energy cascades down to electron scales where electron Landau damping may predominate.

Goldstein, Melvyn L.

2010-01-01

248

Interaction of Comets and the Solar Wind  

NASA Technical Reports Server (NTRS)

The analysis of Comet Kudo-Fujikawa at perihelion was published and picked up by Der Spiegel. Besides a large and rapidly increasing water outgassing rate, we detected a bright tail in doubly ionized carbon. The amount of carbon was greater than could be accounted for by CO photodissociation, and we attribute it to evaporation of organics from dust. A spectacular disconnection event was apparent in the C III tail, and it coincides within the uncertainties to the position of the heliospheric current sheet. The analysis of the sungrazing comet C2001 C2 is in press. It showed evidence for subfragments and for a very long lasting source of neutrals, which we identify as evaporation of pyroxene dust grains. Results were also presented at COSPAR. We are working on observations of another sungrazer, comet C2002 S2, which shows a sudden 2 magnitude drop in optical brightness and an equally sudden recovery. UVCS observations during that time show a steadily increasing outgassing rate. We have derived solar wind densities for both comets, but we are still sorting out the ambiguities involving the fragmentation and optical behavior.

Wagner, William (Technical Monitor); Raymond, John C.

2004-01-01

249

Interaction of Comets and the Solar Wind  

NASA Technical Reports Server (NTRS)

We had originally planned to analyze UVCS observations of Comet Machholz, but we obtained higher quality observations of Comet Kudo-Fujikawa in January 2003 at its 0.19 AU perihelion. Besides a large and rapidly increasing water outgassing rate, we detected a bright tail in doubly ionized carbon. The amount of carbon was greater than could be accounted for by GO photodissociation, and we attribute the carbon to evaporation of organics from dust. A spectacular disconnection event was apparent in the C III tail, and it coincides within the uncertainties with the position of the heliospheric current sheet. A paper is in press in Science, and it will be the subject of a press release. We are also analyzing two sungrazing comets. Comet C/2001 C2 shows evidence for sub-fragments and for a very long lasting source of neutrals, which we tentatively identify as evaporation of pyroxene dust grains. Comet C/2002 S2 shows a sudden 2 magnitude drop in optical brightness and an equally sudden recovery. UVCS observations during that time show a steadily increasing outgassing rate. We have derived solar wind densities for both comets, but we are still sorting out the ambiguities involving the fragmentation and optical behavior. We are collaborating with Philippe Lamy on the LASCO measurements.

Wagner, William (Technical Monitor); Raymond, John C.

2003-01-01

250

Investigation of Solar Wind Correlations and Solar Wind Modifications Near Earth by Multi-Spacecraft Observations: IMP 8, WIND and INTERBALL-1  

NASA Technical Reports Server (NTRS)

The foundation of this Project is use of the opportunity available during the ISTP (International Solar-Terrestrial Physics) era to compare solar wind measurements obtained simultaneously by three spacecraft - IMP 8, WIND and INTERBALL-1 at wide-separated points. Using these data allows us to study three important topics: (1) the size and dynamics of near-Earth mid-scale (with dimension about 1-10 million km) and small-scale (with dimension about 10-100 thousand km) solar wind structures; (2) the reliability of the common assumption that solar wind conditions at the upstream Lagrangian (L1) point accurately predict the conditions affecting Earth's magnetosphere; (3) modification of the solar wind plasma and magnetic field in the regions near the Earth magnetosphere, the foreshock and the magnetosheath. Our Project was dedicated to these problems. Our research has made substantial contributions to the field and has lead others to undertake similar work.

Paularena, Karolen I.; Richardson, John D.; Zastenker, Georgy N.

2002-01-01

251

Sputtering by the Solar Wind: Effects of Variable Composition  

NASA Technical Reports Server (NTRS)

It has long been recognized that solar wind bombardment onto exposed surfaces in the solar system will produce an energetic component to the exospheres about those bodies. Laboratory experiments have shown that there is no increase in the sputtering yield caused by highly charged heavy ions for metallic and for semiconducting surfaces, but the sputter yield can be noticeably increased in the case of a good insulating surface. Recently measurements of the solar wind composition have become available. It is now known that the solar wind composition is highly dependent on the origin of the particular plasma. Using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), broken down into its various components, we have estimated the total sputter yield for each type of solar wind. Whereas many previous calculations of sputtering were limited to the effects of proton bombardment. we show that the heavy ion component. especially the He++ component. can greatly enhance the total sputter yield during times when the heavy ion population is enhanced. We will discuss sputtering of both neutrals and ions.

Killen, R. M.; Arrell, W. M.; Sarantos, M.; Delory, G. T.

2011-01-01

252

Western Wind and Solar Integration Study Phase 2: Preprint  

SciTech Connect

The Western Wind and Solar Integration Study (WWSIS) investigates the impacts of high penetrations of wind and solar power into the Western Interconnection of the United States. WWSIS2 builds on the Phase 1 study but with far greater refinement in the level of data inputs and production simulation. It considers the differences between wind and solar power on systems operations. It considers mitigation options to accommodate wind and solar when full costs of wear-and-tear and full impacts of emissions rates are taken into account. It determines wear-and-tear costs and emissions impacts. New data sets were created for WWSIS2, and WWSIS1 data sets were refined to improve realism of plant output and forecasts. Four scenarios were defined for WWSIS2 that examine the differences between wind and solar and penetration level. Transmission was built out to bring resources to load. Statistical analysis was conducted to investigate wind and solar impacts at timescales ranging from seasonal down to 5 minutes.

Lew, D.; Brinkman, G.; Ibanez, E.; Hodge, B.-M.; King, J.

2012-09-01

253

Solar wind speed and coronal flux-tube expansion  

Microsoft Academic Search

The hypothesis that the solar wind speed at 1 AU and the rate of magnetic flux-tube expansion in the corona are inversely correlated is shown to be consistent with observations extending over the last 22 years. This empirical relationship allows the daily wind speeds at earth to be predicted from a current-free extrapolation of the observed photospheric field into the

Y.-M. Wang

1990-01-01

254

Constraints on neon and argon isotopic fractionation in solar wind.  

PubMed

To evaluate the isotopic composition of the solar nebula from which the planets formed, the relation between isotopes measured in the solar wind and on the Sun's surface needs to be known. The Genesis Discovery mission returned independent samples of three types of solar wind produced by different solar processes that provide a check on possible isotopic variations, or fractionation, between the solar-wind and solar-surface material. At a high level of precision, we observed no significant inter-regime differences in 20Ne/22Ne or 36Ar/38Ar values. For 20Ne/22Ne, the difference between low- and high-speed wind components is 0.24 +/- 0.37%; for 36Ar/38Ar, it is 0.11 +/- 0.26%. Our measured 36Ar/38Ar ratio in the solar wind of 5.501 +/- 0.005 is 3.42 +/- 0.09% higher than that of the terrestrial atmosphere, which may reflect atmospheric losses early in Earth's history. PMID:17947578

Meshik, Alex; Mabry, Jennifer; Hohenberg, Charles; Marrocchi, Yves; Pravdivtseva, Olga; Burnett, Donald; Olinger, Chad; Wiens, Roger; Reisenfeld, Dan; Allton, Judith; McNamara, Karen; Stansbery, Eileen; Jurewicz, Amy J G

2007-10-19

255

Electron energy transport in the solar wind: Ulysses observations  

NASA Technical Reports Server (NTRS)

The electron heat flux in the solar wind has been measured by the Ulysses solar wind plasma experiment in the ecliptic from 1 to 5 AU and out of the ecliptic during the recently completed pass over the solar south pole and the ongoing pass over the solar north pole. Although the electron heat flux contains only a fraction of the kinetic energy of the solar wind. the available energy is sufficient to account for the non-adiabatic expansion of the solar wind electrons. The Ulysses measurements indicate that the electron heat flux is actively dissipated in the solar wind. The exact mechanism or mechanisms is unknown. but a model based on the whistler heat flux instability predicts radial gradients for the electron heat flux in good agreement with the data. We will present measurements of the correlation between wave activity measured by the unified radio and plasma experiment (URAP) and the electron heat flux throughout the Ulysses mission. The goal is to determine if whistler waves are a good candidate for the observed electron heat flux dissipation. The latitudinal gradients of the electron heat flux. wave activity. and electron pressure will be discussed in light of the changes in the magnetic field geometry from equator to poles.

Scime, Earl; Gary, S. Peter; Phillips, J. L.; Corniileau-Wehrlin, N.; Solomon, J.

1995-01-01

256

A new method to estimate annual solar wind parameters and contributions of different solar wind structures to geomagnetic activity  

NASA Astrophysics Data System (ADS)

In this paper, we study two sets of local geomagnetic indices from 26 stations using the principal component and the independent component (IC) analysis methods. We demonstrate that the annually averaged indices can be accurately represented as linear combinations of two first components with weights systematically depending on latitude. We show that the annual contributions of coronal mass ejections (CMEs) and high-speed streams (HSSs) to geomagnetic activity are highly correlated with the first and second IC. The first and second ICs are also found to be very highly correlated with the strength of the interplanetary magnetic field (IMF) and the solar wind speed, respectively, because solar wind speed is the most important parameter driving geomagnetic activity during HSSs while IMF strength dominates during CMEs. These results help in better understanding the long-term driving of geomagnetic activity and in gaining information about the long-term evolution of solar wind parameters and the different solar wind structures.

Holappa, L.; Mursula, K.; Asikainen, T.

2014-12-01

257

A survey of solar wind conditions at 5 AU: A tool for interpreting solar wind-magnetosphere interactions at Jupiter  

NASA Astrophysics Data System (ADS)

We examine Ulysses solar wind and interplanetary magnetic field (IMF) observations at 5 AU for two ~13 month intervals during the rising and declining phases of solar cycle 23 and the predicted response of the Jovian magnetosphere during these times. The declining phase solar wind, composed primarily of corotating interaction regions and high-speed streams, was, on average, faster, hotter, less dense, and more Alfvénic relative to the rising phase solar wind, composed mainly of slow wind and interplanetary coronal mass ejections. Interestingly, none of solar wind and IMF distributions reported here were bimodal, a feature used to explain the bimodal distribution of bow shock and magnetopause standoff distances observed at Jupiter. Instead, many of these distributions had extended, non-Gaussian tails that resulted in large standard deviations and much larger mean over median values. The distribution of predicted Jupiter bow shock and magnetopause standoff distances during these intervals were also not bimodal, the mean/median values being larger during the declining phase by ~1 - 4%. These results provide data-derived solar wind and IMF boundary conditions at 5 AU for models aimed at studying solar wind-magnetosphere interactions at Jupiter and can support the science investigations of upcoming Jupiter system missions. Here, we provide expectations for Juno, which is scheduled to arrive at Jupiter in July 2016. Accounting for the long-term decline in solar wind dynamic pressure reported by McComas et al. (2013), Jupiter’s bow shock and magnetopause is expected to be at least 8 - 12% further from Jupiter, if these trends continue.

Ebert, Robert; Bagenal, Fran; McComas, David; Fowler, Christopher

2014-09-01

258

Livestock Water Pumping with Wind and Solar Power  

Microsoft Academic Search

Recent developments in pumping technologies have allowed for efficient use of renewable energies like wind and solar to power new pumps for remote water pumping. A helical type, positive displacement pump was developed a few years ago and recently modified to accept input from a variable power source. This pump was tested at different pumping depths with both solar and

R. Nolan Clark; Brian D. Vick

259

Comparing Solar Wind Velocity Measurements Derived from Sun-grazing Comet Lovejoy (C/2011 W3) with Solar Wind Models  

NASA Astrophysics Data System (ADS)

Comets' plasma (type I) tails have been studied as natural probes of the solar wind since the mid-20th century. Local solar wind conditions directly control the morphology and dynamics of a comet's plasma tail. During ideal observing geometries, the orientation and structure of the plasma tail can reveal large-scale and small-scale variations in the local solar wind structure. We present solar wind velocity measurements derived from multiple observing locations of comet Lovejoy (C/2011 W3) from the 14th - 19th December 2011 using recent images from the SECCHI and LASCO heliospheric imagers and coronagraphs aboard STEREO A and B, and SOHO. Overlapping observation sessions from the three spacecraft provided the perfect opportunity to use comet Lovejoy as a diagnostic tool to understand solar wind variability close to the Sun. Our unique analysis technique [submitted] allows us to determine the latitudinal variations of the solar wind, heliospheric current sheet sector boundaries and the boundaries of transient features as comet Lovejoy probes the Sun's atmosphere. We plan to compare our observations to results of suitable simulations of plasma conditions in the corona and inner heliosphere during the time of Lovejoy's perihelion passage.

Ramanjooloo, Y.; Jones, G. H.; Coates, A. J.; Owens, M. J.; Battams, K.

2012-12-01

260

Velocity Distributions and Proton Beam Production in the Solar Wind  

SciTech Connect

Helios, Ulysses, and Wind spacecraft have observed the velocity distribution functions (VDFs) of solar wind particles deviating significantly from Maxwellians. We review recent models using different approximations and mechanisms that determine various observed characteristics of the VDFs for the electrons, protons and minor ions. A new generation mechanism is proposed for super-Alfvenic proton beams and tails that are often observed in the fast solar wind. The mechanism is based on the proton trapping and acceleration by kinetic Alfven waves (KAWs), which carry a field-aligned potential well propagating with super-Alfven velocities.

Pierrard, Viviane; Voitenko, Yuriy [Belgian Institute for Space Aeronomy, Ringlaan-3-Avenue Circulaire, B-1180 Brussels (Belgium)

2010-03-25

261

Velocity shear layers in solar winds affect Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

Human society is increasingly reliant on technology that can be disrupted by space weather. For instance, geomagnetic storms can cause high-latitude air fights to be rerouted, costing as much as $100,000 per fight; induce errors of up to 46 meters in GPS systems; and affect satellites and the International Space Station. Space weather is determined by how the solar wind, a stream of hot plasma from the Sun, interacts with Earth's magnetic field. In studying space weather, scientists have largely neglected the fact that the solar wind contains layers of very strong velocity shear. Scientists understand very little about how these wind shears affect space weather.

Bhattacharya, Atreyee

2012-09-01

262

Electric potential of the moon in the solar wind.  

NASA Technical Reports Server (NTRS)

Acceleration and detection of the lunar thermal ionosphere in the presence of the lunar electric field yields a value of at least +10 V for the lunar electric potential for solar zenith angles between approximately 20 and 45 deg and in the magnetosheath or solar wind. An enhanced positive ion flux is observed with the Apollo Lunar Surface Experiments Package Suprathermal Ion Detector Experiment when a preacceleration voltage attains certain values. This enhancement is greater when the moon is in the solar wind as opposed to the magnetosheath.

Freeman, J. W., Jr.; Fenner, M. A.; Hills, H. K.

1973-01-01

263

Solar Wind Stream Interaction Regions without Sector Boundaries  

NASA Technical Reports Server (NTRS)

During periods of high solar activity when there are many sources of solar wind on the solar disk, a spacecraft occasionally encounters consecutive solar wind streams with the same magnetic polarity. The low-speed wind in the region of interaction between the two streams exhibits many of the same features as, but has some differences from, the low-speed wind that includes crossings of the heliospheric current sheet (HCS) where the direction of the heliospheric magnetic field reverses. The non-HCS slow wind exhibits many of the same small-scale structures usually associated with the slow wind around the HCS; these include discontinuous stream interfaces and other discontinuities, magnetic holes, and low-entropy structures. These entropy holes do not appear to have the same origin as the plasma sheets observed near the HCS, however. The helium abundances and heavy ion charge states in the non-HCS regions are not significantly different from those in HCS-associated regions. Some of the dynamical properties of the non-HCS regions differ from those found near the HCS; the regions between leading and trailing stream interfaces have a shorter duration or scale size, greater minimum speed, and lower peak and average densities. No correlation could be found between the non-HCS slow wind and visible coronal streamers.

Neugebauer, M.; Liewer, P. C.; Goldstein, B. E.; Zhou., X.; Steinberg, J. T.

2004-01-01

264

On the proton temperature anisotropy in the solar wind  

NASA Astrophysics Data System (ADS)

We present a comparison between WIND SWE observations em Kasper et al 2006 of the proton temperature anisotropy T perp p T parallel p in the solar wind and predictions of the Vlasov linear theory In the slow solar wind the observed proton temperature anisotropy seems to be constrained by oblique instabilities by the mirror one and the oblique fire hose contrary to the results of the linear theory which predicts a dominance of the proton cyclotron instability and the parallel fire hose The fast solar wind core protons exhibit an anticorrelation between beta parallel p and T perp p T parallel p similar to that observed in the HELIOS data em Marsch et al 2003 and indicate a possible constraining role of the mirror and parallel fire hose instabilities

Hellinger, P.; Travnicek, P.; Kasper, J. C.; Lazarus, A. J.

265

Shear flow induced wave couplings in the solar wind  

SciTech Connect

A sheared background flow in a plasma induces coupling between different MHD wave modes, resulting in their mutual transformations with corresponding energy redistributing between the modes. In this way, the energy can be transfered from one wave mode to the other, but energy can also be added to or extracted from the background flow. In the present paper it is investigated whether the wave coupling and energy transfer mechanisms can operate under solar wind conditions. It is shown that this is indeed the case. Hence, the long-period waves observed in the solar wind at r > 0.3 AU might be generated by much faster periodic oscillations in the photosphere of the Sun. Other possible consequences for observable beat phenomena in the wind and the acceleration of the solar wind particles are also discussed.

Poedts, S. [KULeuven, Heverlee (Belgium). Centre for Plasma Astrophysics; Rogava, A.D. [Tbilisi State Univ. (Georgia). Dept. of Physics]|[International Centre for Theoretical Physics, Trieste (Italy); Mahajan, S.M. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies]|[International Centre for Theoretical Physics, Trieste (Italy)

1998-01-01

266

Ulysses solar wind plasma observations at high latitudes  

SciTech Connect

Ulysses reached its peak northerly heliolatitude of 80.2{degrees}N on July 31, 1995, and now is moving towards aphelion at 5.41 AU which it will reach in May, 1998. We summarize measurements from the solar wind plasma experiment, SWOOPS, emphasizing northern hemispheric observations but also providing southern and equatorial results for comparison. The solar wind momentum flux during Ulysses` fast pole-to- pole transit at solar minimum was significantly higher over the poles than at near-equatorial latitudes, suggesting a non-circular cross section for the heliosphere. Furthermore, modest asymmetries in the wind speed, density, and mass flux were observed between the two hemispheres during the fast latitude scan. The solar wind was faster and less dense in the north than in the south. These asymmetries persist in the most recent high- and mid-latitude data but are less pronounced. As of July 1, 1996 the northern fast solar wind has lacked any strong stream interactions or shocks and, although a comprehensive search has not yet been made, no CMEs have yet been identified during this interval. On the other hand, Alfv{acute e}nic, compressional, and pressure balanced features are abundant at high latitudes. The most recent data, at 4 AU and 32{degrees}N, has begun to show the effects of solar rotation modulated features in the form of recurrent compressed regions.

Riley, P.; Bame, S.J.; Barraclough, B.L. [and others

1996-10-01

267

VLBI-experiments on research of solar wind plasma  

E-print Network

This work devotes to investigations of solar corona and solar wind plasma by the method of radio probing with using of very long baseline interferometry (VLBI). We performed the theoretical calculation of power spectrum of interferometric response to radio source emission, passed through the turbulent medium. Data of theoretical analysis are compared with results of international VLBI experiments on investigations of solar wind plasma. The observations were realized in 1998, 1999, 2000 with participation of radio telescopes, included at Low Frequency VLBI Network (LFVN): Bear Lakes (RT-64, Russia), Puschino (RT-22, Russia), Urumqi (RT-25, China), Noto (RT-32, Italy), Shanghai (RT-25, China) and others. Preprocessing was carried out with using of S2 correlator at Penticton (Canada). Post processing of experimental data was performed at RRI (Russia) and was aimed to obtain value of solar wind velocity and index of spatial spectrum of electron density fluctuations.

M. B. Nechaeva; V. G. Gavrilenko; Y. N. Gorshenkov; . B. N. Lipatov; L. Xiang; I. E. Molotov; A. B. Pushkarev; R. Shanks; G. Tuccari

2004-12-30

268

Shapes of strong shock fronts in an inhomogeneous solar wind  

NASA Technical Reports Server (NTRS)

The shapes expected for solar-flare-produced strong shock fronts in the solar wind have been calculated, large-scale variations in the ambient medium being taken into account. It has been shown that for reasonable ambient solar wind conditions the mean and the standard deviation of the east-west shock normal angle are in agreement with experimental observations including shocks of all strengths. The results further suggest that near a high-speed stream it is difficult to distinguish between corotating shocks and flare-associated shocks on the basis of the shock normal alone. Although the calculated shapes are outside the range of validity of the linear approximation, these results indicate that the variations in the ambient solar wind may account for large deviations of shock normals from the radial direction.

Heinemann, M. A.; Siscoe, G. L.

1974-01-01

269

SOLAR WIND HEAVY IONS OVER SOLAR CYCLE 23: ACE/SWICS MEASUREMENTS  

SciTech Connect

Solar wind plasma and compositional properties reflect the physical properties of the corona and its evolution over time. Studies comparing the previous solar minimum with the most recent, unusual solar minimum indicate that significant environmental changes are occurring globally on the Sun. For example, the magnetic field decreased 30% between the last two solar minima, and the ionic charge states of O have been reported to change toward lower values in the fast wind. In this work, we systematically and comprehensively analyze the compositional changes of the solar wind during cycle 23 from 2000 to 2010 while the Sun moved from solar maximum to solar minimum. We find a systematic change of C, O, Si, and Fe ionic charge states toward lower ionization distributions. We also discuss long-term changes in elemental abundances and show that there is a {approx}50% decrease of heavy ion abundances (He, C, O, Si, and Fe) relative to H as the Sun went from solar maximum to solar minimum. During this time, the relative abundances in the slow wind remain organized by their first ionization potential. We discuss these results and their implications for models of the evolution of the solar atmosphere, and for the identification of the fast and slow wind themselves.

Lepri, S. T.; Landi, E.; Zurbuchen, T. H. [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, TC 2210 Ann Arbor, MI 48109 (United States)

2013-05-01

270

Elemental composition in the slow solar wind measured with the MASS instrument on WIND  

NASA Technical Reports Server (NTRS)

The MASS instrument on WIND contains the first isochronous time-offlight spectrometer to be flown in the solar wind. The first spectra obtained with this instrument has demonstrated its capability to measure the abundances of several high-and low-FIP elements in the solar wind. The derivation of these abundances requires a careful calibration of the charge exchange efficiencies of the relevant ions in carbon foils. These efficiencies and the corresponding instrument functions have been determined in extensive calibration campaigns at different institutions. We present first and preliminary results obtained in slow solar wind streams and we compare these results with those obtained from previous investigations of solar wind abundances and of coronal abundances as derived from Solar Energetic Particles. Recent models of the FIP related fractionation effect predict a depletion of a factor of typically 4 to 5 for high-FIP elements (He, N, O, Ne, Ar, etc.) relative to low-FIP elements (Mg, Fe, Si, etc.). We also compare our results with the detailed predictions of the different models and we discuss the resulting evidence to validate or to invalidate different physical scenarios explaining the feeding and the acceleration of slow stream solar wind.

Bochsler, P.; Gonin, M.; Sheldon, R. B.; Zurbuchen, Th.; Gloeckler, G.; Galvin, A. B.; Hovestadt, D.

1995-01-01

271

Solar wind interaction with Venus and impact on its atmosphere  

NASA Astrophysics Data System (ADS)

We present a review of the solar wind interaction with Venus and how the interaction affects the Venusian atmosphere. The Venus Express observations for more than 8 years (2005-present) and quantitatively new simulation codes substantially advanced physical understanding of the plasma processes in the near-Venus space since the Pioneer Venus Orbiter (PVO) mission (1978-1992). The near-Venus space can be divided into several plasma domains: the magnetotail with the plasmasheet, induced magnetosphere, and magnetosheath. The bow shock separates the undisturbed solar wind from the Venus-affected environment. We review the shapes and positions of the boundaries enveloping the main domains and discuss how they are formed by the current systems and pressure balance. In particular, we discuss the morphology and dynamics of the near-Venus magnetotail that was not accessible by PVO. Using the unique Venus Express measurements we discuss the ion acceleration processes and their links to the ionosphere. The focus is given to the Venus' atmosphere erosion associated with the solar wind interaction, both through the energy (ion acceleration) and momentum (atmospheric sputtering) transfer. We review the measurements of the escape rates, their variability with the upstream solar wind conditions and the solar cycle. We emphasize the measurements duirng extreme solar wind conditions as an analogue with nominal conditions for the young Sun. The modeling efforts in this area are also reviewed as they provide a quantitatively approach to understand the impact of the solar wind interaction on the atmospheric evolution. Finally, we compare Venus with other planets of the terrestrial planet group, the Earth and Mars. The Earth, a twin planet of the similar size, is magnetized. Mars, an unmagnetized planet like Venus, possesses by far weaker gravitation to hold its atmospheric gasses. This comparative magnetosphere approach based on the natural solar system laboratory of experiments gives a clearer perspective on physics and processes, which forms the near-Venus space.

Barabash, S.; Futaana, Y.; Wieser, G. S.; Luhmann, J.

2014-04-01

272

Sharp boundaries of small-and middle-scale solar wind structures  

E-print Network

Sharp boundaries of small- and middle-scale solar wind structures M. O. Riazantseva1 and G. N-scale solar wind plasma structures. We present examples and statistical results from simultaneous plasma and magnetic field measurements by Interball-1 and Wind from 1996 to 1999. The behavior of the solar wind bulk

Richardson, John

273

Some Characteristics of Solar Wind and Plasma Behavior of the Sun with the Geomagnetic Activity 1  

E-print Network

Variations of the 27-day average solar wind proton density and solar wind plasma speed have been examined for a period from 1970 to 2012. The variation of the solar wind plasma temperature and the plasma speed have also been considered for the same period including the flow pressure, the sunspot number and the variation of ap index. In general, the solar wind speed reveals an inverse correlation with the solar wind proton density while the solar wind plasma speed and solar wind plasma temperature exhibit similar nature of variation. The solar wind flow pressure is found to vary in a reverse way with solar activity cycle but the geomagnetic activity index ap falls at solar minimum even at a high flow pressure.

A. B. Bhattacharya; M. Debnath

274

Solar cosmic ray, solar wind, solar flare, and neutron albedo measurements, part C  

NASA Technical Reports Server (NTRS)

All mineral detectors exposed on Apollo 16 had high surface track densities probably produced by a solar flare that occurred during the mission. The heavy ions followed a power law spectrum with exponent approximately 3 down to approximately 200 KeV/nucleon. The abundance of low-energy particle tracks observed in this flare may explain the high track densities observed in lunar dust grains. Pristine heavy-particle tracks in feldspar give long tracks. Shallow pits similar to those expected from extremely heavy solar wind ions were observed in about the expected number. Initial results give a low apparent value of neutron albedo relative to theory.

Burnett, D.; Hohenberg, C.; Maurette, M.; Monnin, M.; Walker, R.; Wollum, D.

1972-01-01

275

Simulation and optimum design of hybrid solar-wind and solar-wind-diesel power generation systems  

NASA Astrophysics Data System (ADS)

Solar and wind energy systems are considered as promising power generating sources due to its availability and topological advantages in local power generations. However, a drawback, common to solar and wind options, is their unpredictable nature and dependence on weather changes, both of these energy systems would have to be oversized to make them completely reliable. Fortunately, the problems caused by variable nature of these resources can be partially overcome by integrating these two resources in a proper combination to form a hybrid system. However, with the increased complexity in comparison with single energy systems, optimum design of hybrid system becomes more complicated. In order to efficiently and economically utilize the renewable energy resources, one optimal sizing method is necessary. This thesis developed an optimal sizing method to find the global optimum configuration of stand-alone hybrid (both solar-wind and solar-wind-diesel) power generation systems. By using Genetic Algorithm (GA), the optimal sizing method was developed to calculate the system optimum configuration which offers to guarantee the lowest investment with full use of the PV array, wind turbine and battery bank. For the hybrid solar-wind system, the optimal sizing method is developed based on the Loss of Power Supply Probability (LPSP) and the Annualized Cost of System (ACS) concepts. The optimization procedure aims to find the configuration that yields the best compromise between the two considered objectives: LPSP and ACS. The decision variables, which need to be optimized in the optimization process, are the PV module capacity, wind turbine capacity, battery capacity, PV module slope angle and wind turbine installation height. For the hybrid solar-wind-diesel system, minimization of the system cost is achieved not only by selecting an appropriate system configuration, but also by finding a suitable control strategy (starting and stopping point) of the diesel generator. The optimal sizing method was developed to find the system optimum configuration and settings that can achieve the custom-required Renewable Energy Fraction (fRE) of the system with minimum Annualized Cost of System (ACS). Du to the need for optimum design of the hybrid systems, an analysis of local weather conditions (solar radiation and wind speed) was carried out for the potential installation site, and mathematical simulation of the hybrid systems' components was also carried out including PV array, wind turbine and battery bank. By statistically analyzing the long-term hourly solar and wind speed data, Hong Kong area is found to have favorite solar and wind power resources compared with other areas, which validates the practical applications in Hong Kong and Guangdong area. Simulation of PV array performance includes three main parts: modeling of the maximum power output of the PV array, calculation of the total solar radiation on any tilted surface with any orientations, and PV module temperature predictions. Five parameters are introduced to account for the complex dependence of PV array performance upon solar radiation intensities and PV module temperatures. The developed simulation model was validated by using the field-measured data from one existing building-integrated photovoltaic system (BIPV) in Hong Kong, and good simulation performance of the model was achieved. Lead-acid batteries used in hybrid systems operate under very specific conditions, which often cause difficulties to predict when energy will be extracted from or supplied to the battery. In this thesis, the lead-acid battery performance is simulated by three different characteristics: battery state of charge (SOC), battery floating charge voltage and the expected battery lifetime. Good agreements were found between the predicted values and the field-measured data of a hybrid solar-wind project. At last, one 19.8kW hybrid solar-wind power generation project, designed by the optimal sizing method and set up to supply power for a telecommunication relay station on a remote island of Guangdong pr

Zhou, Wei

276

Reflection of solar wind hydrogen from the lunar surface H. O. Funsten,1  

E-print Network

Reflection of solar wind hydrogen from the lunar surface H. O. Funsten,1 F. Allegrini,2,3 P. A] The solar wind continuously flows out from the Sun and directly interacts with the surfaces of dust and airless planetary bodies throughout the solar system. A significant fraction of solar wind ions reflect

Johnson, Robert E.

277

The characteristics of sharp (small-scale) boundaries of solar wind plasma and magnetic field structures  

E-print Network

The characteristics of sharp (small-scale) boundaries of solar wind plasma and magnetic field investigate properties of large (>20%) and sharp (solar wind ion flux changes using INTERBALL-1 are the boundaries of small-scale and mid- dle-scale solar wind structures. We describe the behavior of the solar

Richardson, John

278

Impact of increased penetration of wind and PV solar resources on the  

E-print Network

the impact of increased penetration of wind and solar resources on the bulk energy system (BES) · The BESImpact of increased penetration of wind and PV solar resources on the bulk power system Vijay solar impacts on system dynamic performance · Since wind turbine generators (WTGs) and PV solar

279

Charge state composition in coronal hole and CME related solar wind: Latitudinal variations observed by Ulysses and WIND  

NASA Technical Reports Server (NTRS)

Iron charge states in recurrent coronal hole-associated solar wind flows are obtained in the ecliptic by WIND/SMS, while measurements of iron and silicon from the polar coronal holes are available from Ulysses/SWICS. Ulysses/SWICS also provides ion composition of coronal mass ejection (CME)-related solar wind. Both coronal hole-associated and CME-related solar wind charge charges show heliographic latitudinal variations.

Galvin, A. B.; Gloeckler, G.

1997-01-01

280

Long-term-average, solar cycle, and seasonal response of magnetospheric energetic electrons to the solar wind speed  

E-print Network

to the solar wind speed D. Vassiliadis,1 A. J. Klimas,2 S. G. Kanekal,3 D. N. Baker,3 and R. S. Weigel4. [1] Among the interplanetary activity parameters the solar wind speed is the one best correlated is parameterized by the time delay (t), measured from the time of solar wind impact, and the L shell (L). We

281

SOLAR WIND MODELING WITH TURBULENCE TRANSPORT AND HEATING  

SciTech Connect

We have developed an axisymmetric steady-state solar wind model that describes properties of the large-scale solar wind, interplanetary magnetic field, and turbulence throughout the heliosphere from 0.3 AU to 100 AU. The model is based on numerical solutions of large-scale Reynolds-averaged magnetohydrodynamic equations coupled with a set of small-scale transport equations for the turbulence energy, normalized cross helicity, and correlation scale. The combined set of time-dependent equations is solved in the frame of reference corotating with the Sun using a time-relaxation method. We use the model to study the self-consistent interaction between the large-scale solar wind and smaller-scale turbulence and the role of the turbulence in the large-scale structure and temperature distribution in the solar wind. To illuminate the roles of the turbulent cascade and the pickup protons in heating the solar wind depending on the heliocentric distance, we compare the model results with and without turbulence/pickup protons. The variations of plasma temperature in the outer heliosphere are compared with Ulysses and Voyager 2 observations.

Usmanov, Arcadi V.; Goldstein, Melvyn L. [Code 673, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Matthaeus, William H. [Department of Physics and Astronomy and Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Breech, Benjamin A., E-mail: arcadi.usmanov@nasa.gov [NASA Postdoctoral Program, Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2011-02-01

282

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE  

SciTech Connect

The dissipation of turbulence in the weakly collisional solar wind plasma is governed by unknown kinetic mechanisms. Two candidates have been suggested to play an important role in the dissipation, collisionless damping via wave-particle interactions and dissipation in small-scale current sheets. High resolution spacecraft measurements of the turbulent magnetic energy spectrum provide important constraints on the dissipation mechanism. The limitations of popular fluid and hybrid numerical schemes for simulation of the dissipation of solar wind turbulence are discussed, and instead a three-dimensional kinetic approach is recommended. We present a three-dimensional nonlinear gyrokinetic simulation of solar wind turbulence at electron scales that quantitatively reproduces the exponential form of the turbulent magnetic energy spectrum measured in the solar wind. A weakened cascade model that accounts for nonlocal interactions and collisionless Landau damping also quantitatively agrees with the observed exponential form. These results establish that a turbulent cascade of kinetic Alfven waves that is terminated by collisionless Landau damping is sufficient to explain the observed magnetic energy spectrum in the dissipation range of solar wind turbulence.

TenBarge, J. M.; Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Dorland, W., E-mail: jason-tenbarge@uiowa.edu [Department of Physics, University of Maryland, College Park, MA 20742-3511 (United States)

2013-09-10

283

Magnetic field gradients in solar wind plasma and geophysics periods  

E-print Network

Using recent data obtained by Advanced Composition Explorer (ACE) the pumping scale of the magnetic field gradients of the solar wind plasma has been calculated. This pumping scale is found to be equal to 24h $\\pm$ 2h. The ACE spacecraft orbits at the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth. Since the Earth's magnetosphere extends into the vacuum of space from approximately 80 to 60,000 kilometers on the side toward the Sun the pumping scale cannot be a consequence of the 24h-period of the Earth's rotation. Vise versa, a speculation is suggested that for the very long time of the coexistence of Earth and of the solar wind the weak interaction between the solar wind and Earth could lead to stochastic synchronization between the Earth's rotation and the pumping scale of the solar wind magnetic field gradients. This synchronization could transform an original period of the Earth's rotation to the period close to the pumping scale of the solar wind magnetic field gradients.

A. Bershadskii

2006-11-16

284

Direct evidence for kinetic effects associated with solar wind reconnection  

PubMed Central

Kinetic effects resulting from the two-fluid physics play a crucial role in the fast collisionless reconnection, which is a process to explosively release massive energy stored in magnetic fields in space and astrophysical plasmas. In-situ observations in the Earth's magnetosphere provide solid consistence with theoretical models on the point that kinetic effects are required in the collisionless reconnection. However, all the observations associated with solar wind reconnection have been analyzed in the context of magnetohydrodynamics (MHD) although a lot of solar wind reconnection exhausts have been reported. Because of the absence of kinetic effects and substantial heating, whether the reconnections are still ongoing when they are detected in the solar wind remains unknown. Here, by dual-spacecraft observations, we report a solar wind reconnection with clear Hall magnetic fields. Its corresponding Alfvenic electron outflow jet, derived from the decouple between ions and electrons, is identified, showing direct evidence for kinetic effects that dominate the collisionless reconnection. The turbulence associated with the exhaust is a kind of background solar wind turbulence, implying that the reconnection generated turbulence has not much developed. PMID:25628139

Xu, Xiaojun; Wang, Yi; Wei, Fengsi; Feng, Xueshang; Deng, Xiaohua; Ma, Yonghui; Zhou, Meng; Pang, Ye; Wong, Hon-Cheng

2015-01-01

285

Direct evidence for kinetic effects associated with solar wind reconnection.  

PubMed

Kinetic effects resulting from the two-fluid physics play a crucial role in the fast collisionless reconnection, which is a process to explosively release massive energy stored in magnetic fields in space and astrophysical plasmas. In-situ observations in the Earth's magnetosphere provide solid consistence with theoretical models on the point that kinetic effects are required in the collisionless reconnection. However, all the observations associated with solar wind reconnection have been analyzed in the context of magnetohydrodynamics (MHD) although a lot of solar wind reconnection exhausts have been reported. Because of the absence of kinetic effects and substantial heating, whether the reconnections are still ongoing when they are detected in the solar wind remains unknown. Here, by dual-spacecraft observations, we report a solar wind reconnection with clear Hall magnetic fields. Its corresponding Alfvenic electron outflow jet, derived from the decouple between ions and electrons, is identified, showing direct evidence for kinetic effects that dominate the collisionless reconnection. The turbulence associated with the exhaust is a kind of background solar wind turbulence, implying that the reconnection generated turbulence has not much developed. PMID:25628139

Xu, Xiaojun; Wang, Yi; Wei, Fengsi; Feng, Xueshang; Deng, Xiaohua; Ma, Yonghui; Zhou, Meng; Pang, Ye; Wong, Hon-Cheng

2015-01-01

286

The abundances of elements and isotopes in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind abundances have now been measured for eleven elements and the isotopes of the noble gases. Aside from solar wind protons and alpha particles, which have been studied extensively since the 1960's, information for heavier elements is limited. Nevertheless, two effects stand out. First is the enrichment of abundances of elements with low first ionization potential (FIP), most likely the combined result of an atom-ion separation process in the upper chromosphere, and a marginal coupling of low-charge-state heavy ions to protons and alphas during the acceleration of the solar wind. Second, there is variability in the solar wind composition over a whole range of time scales. Recent measurements carried out in the earth's magnetosheath during times that included high-speed coronal-hole-associated flows indicate a significantly lower overabundance of low FIP elements. Given the fact that the He/H ratio is remarkably constant in the coronal hole solar wind, this result suggests that both enrichment and variability are reduced in such flows.

Gloeckler, George; Geiss, Johannes

1989-01-01

287

78 FR 76609 - Genesis Solar, LLC; NRG Delta LLC; Mountain View Solar, LLC; Pheasant Run Wind, LLC; Pheasant Run...  

Federal Register 2010, 2011, 2012, 2013

...62-000; EG13-63-000; EG13-64-000; FC13-13-000] Genesis Solar, LLC; NRG Delta LLC; Mountain View Solar, LLC; Pheasant Run Wind, LLC; Pheasant Run Wind II, LLC; Tuscola Wind II, LLC; Mountain Wind Power, LLC;...

2013-12-18

288

THE TURBULENT CASCADE AND PROTON HEATING IN THE SOLAR WIND DURING SOLAR MINIMUM  

SciTech Connect

The recently protracted solar minimum provided years of interplanetary data that were largely absent in any association with observed large-scale transient behavior on the Sun. With large-scale shear at 1 AU generally isolated to corotating interaction regions, it is reasonable to ask whether the solar wind is significantly turbulent at this time. We perform a series of third-moment analyses using data from the Advanced Composition Explorer. We show that the solar wind at 1 AU is just as turbulent as at any other time in the solar cycle. Specifically, the turbulent cascade of energy scales in the same manner proportional to the product of wind speed and temperature. Energy cascade rates during solar minimum average a factor of 2-4 higher than during solar maximum, but we contend that this is likely the result of having a different admixture of high-latitude sources.

Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CA (United States); Forman, Miriam A., E-mail: jtu46@wildcats.unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Joshua.Stawarz@Colorado.edu, E-mail: Miriam.Forman@sunysb.edu [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY (United States)

2012-08-01

289

Influence of interplanetary solar wind sector polarity on the ionosphere  

NASA Astrophysics Data System (ADS)

Knowledge of solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability. A solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbance and ionospheric perturbations has been demonstrated. The increases in interplanetary solar wind speed within three days are seen after SB crossings, while the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings are confirmed by the superposed epoch analysis results. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. The F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998-2011 are utilized to extract the related information, revealing that they are not modified significantly and vary within the range of 15% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months, which is mainly caused by larger southward Bz components in equinox. In September equinox, latitudinal profile of relative variations of foF2 at noon is featured by depressions at high latitudes and enhancements in low-equatorial latitudes during IMF away sectors. The negative phase of foF2 is delayed at solar minimum relative to it during other parts of solar cycle, which might be associated with the difference in longevity of major interplanetary solar wind drivers perturbing the Earth's environment in different phases of solar cycle.

liu, jing

2014-05-01

290

Solar wind and coronal rotation during an activity cycle  

NASA Astrophysics Data System (ADS)

The properties of the solar wind flow are strongly affected by the time-varying strength and geometry of the global background magnetic field. The wind velocity and mass flux depend directly on the size and position of the wind sources at the surface, and on the geometry of the magnetic flux-tubes along which the wind flows. We address these problems by performing numerical simulations coupling a kinematic dynamo code (STELEM) evolve in a 2.5D axisymmetric coronal MHD code (DIP) covering an 11 yr activity cycle. The latitudinal distribution of the calculated wind velocities agrees with in-situ (ULYSSES, HELIO) and radio measurements (IPS). The transition from fast to slow wind flows can be explained in terms of the high overall flux-tube superradial expansion factors in the vicinities of coronal streamer boundaries. We found that the Alfvén radii and the global Sun's mass loss rate vary considerably throughout the cycle (by a factor 4.5 and 1.6, respectively), leading to strong temporal modulations of the global angular momentum flux and magnetic braking torque. The slowly varying magnetic topology introduces strong non-uniformities in the coronal rotation rate in the first few solar radii. Finally, we point out directions to assess the effects of surface transient phenomena on the global properties of the solar wind.

Pinto, Rui; Brun, Allan Sacha

291

Wind in the Solar Corona: Dynamics and Composition  

NASA Astrophysics Data System (ADS)

The dynamics of the solar corona as observed during solar minimum with the Ultraviolet Coronagraph Spectrometer, UVCS, on SOHO is discussed. The large quiescent coronal streamers existing during this phase of the solar cycle are very likely composed by sub-streamers, formed by closed loops and separated by open field lines that are channelling a slow plasma that flows close to the heliospheric current sheet. The polar coronal holes, with magnetic topology significantly varying from their core to their edges, emit fast wind in their central region and slow wind close to the streamer boundary. The transition from fast to slow wind then appears to be gradual in the corona, in contrast with the sharp transition between the two wind regimes observed in the heliosphere. It is suggested that speed, abundance and kinetic energy of the wind are modulated by the topology of the coronal magnetic field. Energy deposition occurs both in the slow and fast wind but its effect on the kinetic temperature and expansion rate is different for the slow and fast wind.

Antonucci, Ester

2006-06-01

292

Observing MHD Waves in the Solar Wind Acceleration Region  

NASA Astrophysics Data System (ADS)

We have, for the first time, observed and characterized compressive waves propagating both outward and inward in the outer solar corona above 4 Rs. In addition to detecting the waves, we have used them to measure outflow in the all-important wind acceleration region. Because the corona is an MHD system, any disturbance in the corona launches low-frequency waves that propagate at the familiar MHD speeds and serve to communicate that disturbance to other parts of the system. Through careful filtration of synoptic STEREO-A/COR-2 data, we have been able to measure both inbound and outbound waves at all locations in the solar corona. By measuring in/out asymmetries in the wave characteristics we have been able to estimate the solar wind acceleration profile. Further, we are able to estimate the location of the Alfvén surface - the hard-to-measure transition between the corona and the superalfvénic solar wind, and the boundary at which solar magnetic field lines transition from "closed" to "open". There is a great deal of work to be done beyond these preliminary results, which - it is hoped - open a new avenue for understanding coronal dynamics and the origin of the solar wind.

DeForest, Craig; McComas, Dave; Howard, Tim A.

2014-06-01

293

The Solar Wind at 20-30 AU  

NASA Technical Reports Server (NTRS)

Pioneer 10 sampled the interplanetary plasma over the range 20 to 30 astronomical units, during the period 1979-1983. The median flow speed is about 400 km/s, and at 20 AU the median density, proton temperature and dynamic pressure are, respectively, 0.025 cm-3, 10(4) K, and 6x10-11 dyne cm-2. It is shown that the average solar wind flow speed does not vary significantly with increasing heliocentric distance, and the density falls off as R-2, as predicted by simple solar wind models. The day-to-day variations in solar wind parameters are smaller at larger distance. Very large shocks however, were detected beyond 25 AU. Comparison of Pioneer 10 and 11 observations at similar distances but different phases of the solar activity cycle shows that solar wind dynamic pressure varies over a wider range during epochs of high solar activity. The variation near 20 AU is likely to be smaller at Voyager 2 Uranus encounter than observed by Pioneer 10 in the 1979-80 period.

Barnes, A.; Gazis, P. R.

1984-01-01

294

Generalized similarity in finite range solar wind magnetohydrodynamic turbulence.  

PubMed

Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. The ULYSSES spacecraft solar polar passes at solar minimum provide in situ observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterizes this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum--with turbulent fluctuations down by a factor of approximately 2 in power--provides a test of this invariance. PMID:20366193

Chapman, S C; Nicol, R M

2009-12-11

295

Generalized Similarity in Finite Range Solar Wind Magnetohydrodynamic Turbulence  

SciTech Connect

Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. The ULYSSES spacecraft solar polar passes at solar minimum provide in situ observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterizes this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum - with turbulent fluctuations down by a factor of approx2 in power - provides a test of this invariance.

Chapman, S. C.; Nicol, R. M. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2009-12-11

296

He abundance variations in the solar wind: Observations from Ulysses  

SciTech Connect

The Ulysses mission is providing the first opportunity to observe variations in solar wind plasma parameters at heliographic latitudes far removed from the ecliptic plane. We present here an overview of the solar wind speed and the variability in helium abundance, [He], for the entire mission to date, data on [He] in six high-latitude coronal mass ejections (CMEs), and a superposed epoch analysis of [He] variations at the seven heliospheric current sheet (HCS) crossings made during the rapid-latitude-scan portion of the mission. The differences in the variability of the solar wind speed and [He] in high-latitude and equatorial regions are quite striking. Solar wind speed is generally low but highly variable near the solar equator, while at higher latitudes the average speed is quite high (average speed around 760 km/s) with little variability. [He] can vary over nearly two decades at low solar latitudes, while at high latitudes it varies only slightly around an average value of {approximately}4.3{percent}. In contrast to the high [He] that is often associated with CMEs observed near the ecliptic, none of the six high-speed CMEs encountered at high southern heliographic latitudes showed any significant variation in helium content from average values. Reasons for this difference between high and low latitude CME observations are not yet understood. A superposed epoch analysis of the [He] during all seven HCS crossings made as Ulysses passed from the southern to northern solar hemisphere shows the expected [He] minimum near the crossing and a broad ({plus_minus}3day) period of low [He] around the crossing time. We briefly discuss how our solar wind [He] observations may provide an accurate measure of the helium composition for all regions of the sun lying above the helium ionization zone. {copyright} {ital 1996 American Institute of Physics.}

Barraclough, B.L.; Feldman, W.C.; Gosling, J.T.; McComas, D.J.; Phillips, J.L. [Los Alamos National Laboratory, University of California, Los Alamos, New Mexico (United States); Goldstein, B.E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States)

1996-07-01

297

Tracking Back the Solar Wind to Its Photospheric Footpoints from Wind Observations - A Statistical Study  

NASA Astrophysics Data System (ADS)

It is of great importance to track the solar wind back to its photospheric source region and identify the related current sheets; this will provide key information for investigating the origin and predictions of the solar wind. We report a statistical study relating the photospheric footpoint motion and in-situ observation of current sheets in the solar wind. We used the potential force-free source-surface (PFSS) model and the daily synoptic charts to trace the solar wind back from 1 AU, as observed by the Wind spacecraft, to the solar surface. As the footpoints move along the solar surface we obtain a time series of the jump times between different points. These jumps can be within a cell and between adjacent cells. We obtained the distribution of the jump times and the distribution for a subset of the jump times in which only jumps between adjacent cells were counted. For both cases, the distributions clearly show two populations. These distributions are compared with the distribution of in-situ current sheets reported in an earlier work of Miao, Peng, and Li ( Ann. Geophys. 29, 237, 2011). Its implications on the origin of the current sheets are discussed.

Huang, Chong; Yan, Yihua; Li, Gang; Deng, Yuanyong; Tan, Baolin

2014-08-01

298

Solar wind flow past Venus - Theory and comparisons  

NASA Technical Reports Server (NTRS)

Advanced computational procedures are applied to an improved model of solar wind flow past Venus to calculate the locations of the ionopause and bow wave and the properties of the flowing ionosheath plasma in the intervening region. The theoretical method is based on a single-fluid, steady, dissipationless, magneto-hydrodynamic continuum model and is appropriate for the calculation of axisymmetric supersonic, super-Alfvenic solar wind flow past a nonmagnetic planet possessing a sufficiently dense ionosphere to stand off the flowing plasma above the subsolar point and elsewhere. Determination of time histories of plasma and magnetic field properties along an arbitrary spacecraft trajectory and provision for an arbitrary oncoming direction of the interplanetary solar wind have been incorporated in the model. An outline is provided of the underlying theory and computational procedures, and sample comparisons of the results are presented with observations from the Pioneer Venus orbiter.

Spreiter, J. R.; Stahara, S. S.

1980-01-01

299

Effects of Electrons on the Solar Wind Proton Temperature Anisotropy  

NASA Astrophysics Data System (ADS)

Among the kinetic microinstabilities, the firehose instability is one of the most efficient mechanisms to restrict the unlimited increase of temperature anisotropy in the direction of an ambient magnetic field as predicted by adiabatic expansion of collision-poor solar wind. Indeed, the solar wind proton temperature anisotropy detected near 1 AU shows that it is constrained by the marginal firehose condition. Of the two types of firehose instabilities, namely, parallel and oblique, the literature suggests that the solar wind data conform more closely to the marginal oblique firehose condition. In the present work, however, it is shown that the parallel firehose instability threshold is markedly influenced by the presence of anisotropic electrons, such that under some circumstances, the cumulative effects of both electron and proton anisotropies could describe the observation without considering the oblique firehose mode.

Michno, M. J.; Lazar, M.; Yoon, P. H.; Schlickeiser, R.

2014-01-01

300

Solar-wind interactions - Nature and composition of lunar atmosphere  

NASA Technical Reports Server (NTRS)

The nature and composition of the lunar atmosphere are examined on the basis of solar-wind interactions, and the nature of the species in the trapped-gas layer is discussed using results of theoretical and experimental investigations. It is shown that the moon has a highly tenuous atmosphere consisting of various species derived from five sources: solar-wind interaction products, cosmic-ray interaction products, effects of meteoritic impacts, planetary degassing, and radioactive-decay products. Atmospheric concentrations are determined for those species derived from solar-wind protons, alpha particles, and oxygen ions. Carbon chemistry is briefly discussed, and difficulties encountered in attempts to determine quantitatively the concentrations of molecular oxygen, atomic oxygen, carbon monoxide, carbon dioxide, and methane are noted. The calculated concentrations are shown to be in good agreement with observations by the Apollo 17 lunar-surface mass spectrometer and orbital UV spectrometer.

Mukherjee, N. R.

1975-01-01

301

The interaction of the solar wind with comets  

NASA Technical Reports Server (NTRS)

Presently, it can be stated with confidence that the cometary plasma tail is a product of the comet's interaction with the solar wind, however, beyond this statement, our confidence decreases rapidly. Even our physical understanding of the comet-solar wind interaction is in a primitive state. Because of this, an empirical approach (based on observations and illustrations) is adopted in the present study. The topics covered include the ion species and production zone of cometary plasma; a continuum description of comet/solar wind interaction in the hydrodynamic approximation; the generation of tail streamers; Alfven's hydromagnetic model of cometary tails, and its consequences; the gross and fine structure of the plasma tail; and the problem of anomalous comets.

Brandt, J. C.; Mendis, D. A.

1979-01-01

302

Theory of discrete wave packets in the solar wind.  

NASA Technical Reports Server (NTRS)

Discrete wave packets were observed by Ogo 5 and earlier satellites. These waves were believed to be in the whistler mode. Since their group velocities were found to be smaller than the solar-wind speed, these waves could not have been generated in the bow shock and could not have propagated upstream later. The present theory discusses a mechanism similar to that of the echo phenomenon in plasma physics discovered in recent years. The present theory enables us to explain (a) why the wave packets were associated with the bow shock, (b) why the wave packets were characterized by coherent oscillations, and (c) why the wave packets had group velocities smaller than the solar wind and yet could still occur in the solar wind. In short, our theory is able to interpret all the essential features deduced from the observational data.

Wu, C. S.

1972-01-01

303

Lunar fossil magnetism and perturbations of the solar wind.  

NASA Technical Reports Server (NTRS)

Perturbations of the solar wind downstream of the moon and lying outside of the rarefaction wave that defines the diamagnetic cavity are used to define possible source regions comprised of intrinsically magnetized areas of the moon. A map of the moon is constructed showing that a model in which the sources are exposed to the grazing solar wind during the lunation yields a selenographically invariant set of regions strongly favoring the lunar highlands over the maria. An alternative model with the source due to electromagnetic induction is explored. The ages of the field sources should be consistent with those based on the basalt ages and possibly far older if the sources are connected with the formation of the highland rocks themselves. The perturbations are tentatively identified as weak shock waves, and a Mach angle in accord with nominal values for the solar wind is found.

Sonett, C. P.; Mihalov, J. D.

1972-01-01

304

Deflection of solar wind protons from the Lunar magnetic anomalies  

NASA Astrophysics Data System (ADS)

The first measurements, which was made on the lunar orbits, has shown that Moon has no its intrinsic dipolar magnetic field. However the residual magnetization in returned lunar samples and also the anomalous magnetization of lunar surface (till several hundred nT) was found even in Apollo missions. Observations of Kaguya and Chandrayaan reveal the significant solar wind protons deflection from the lunar surface in particular from the magnetic anomalies regions. Such deflection implies that the magnetic anomalies may act as magnetosphere-like obstacles (mini-magnetospheres), modifying the upstream plasma. We examined the conditions in solar wind and estimated plasma parameters in solar wind and in crustal magnetic field. Then we made the estimation of the possibility of mini-magnetosphere and shock-like structure formation. Also we applied our calculations to the case of big anomaly.

Sadovski, Andrei; Skalsky, Alexander

305

Deflection of solar wind protons from the Lunar magnetic anomalies  

NASA Astrophysics Data System (ADS)

The first measurements, which was made on the lunar orbits, has shown that Moon has no its intrinsic dipolar magnetic field. However the residual magnetization in returned lunar samples and also the anomalous magnetization of lunar surface (till several hundred nT) was found even in Apollo missions. Observations of Kaguya and Chandrayaan reveal the significant solar wind protons deflection from the lunar surface in particular from the magnetic anomalies regions. Such deflection implies that the magnetic anomalies may act as magnetosphere-like obstacles (mini-magnetospheres), modifying the upstream plasma. We examined the conditions in solar wind and estimated plasma parameters in solar wind and in crustal magnetic field. Then we made the estimation of the possibility of mini-magnetosphere and shock-like structure formation. Also we applied our calculations to the case of big anomaly.

Sadovski, Andrei M.; Skalsky, Alexander A.

2014-05-01

306

On the response of polar cap dynamics to its solar wind and magnetotail drivers at high levels of geomagnetic activity  

E-print Network

polar cap potential by intense solar wind electric fields,potentials measured with Super Dual Auroral Radar Network during quasi-steady solar wind andelectric potential as a function of solar wind parameters by

Gao, Ye

2012-01-01

307

Search for fine scale structures in high latitude solar wind  

NASA Technical Reports Server (NTRS)

About 25 years ago, E. Parker suggested that, as a consequence of the inhomogeneous structure of the corona, the solar wind might consist of adjacent structures with different physical conditions. Since that suggestion was made, the solar wind plasma characteristics have been measured in situ through many experiments, but little has been done to check whether the solar wind shows any evidence for fine scale structures, and, in the affirmative, how far from the Sun these structures persist. A previous work on this subject, by Thieme, Marsch and Schwenn (1990), based on Helios data, lead these authors to claim that the solar wind, between 0.3 and 1 AU, is inhomogeneous on a scale consistent with the hypothesis that the plume-interplume plasmas, at those distances, still retain their identity. In this work we present preliminary results from an investigation of the solar wind fine structure from Ulysses high latitude observations. To this end, we have analyzed data over several months, during 1994, at times well after Ulysses's last encounter with the Heliospheric Current Sheet, when the spacecraft was at latitudes above 50 degrees. These data refer to high speed wind coming from southern polar coronal holes and are best suited for plume-interplume identification. We have performed a power spectra analysis of typical plasma parameters, to test whether the wind plasma consist of two distinct plasma populations. We also examined data to check whether there is any evidence for an horizontal pressure balance over the hypothesized distinct structures. Our results are discussed and compared with previous findings.

Livi, S.; Parenti, S.; Poletto, G.

1995-01-01

308

Agua Caliente Wind/Solar Project at Whitewater Ranch  

SciTech Connect

Agua Caliente Band of Cahuilla Indians (ACBCI) was awarded a grant by the Department of Energy (DOE) to study the feasibility of a wind and/or solar renewable energy project at the Whitewater Ranch (WWR) property of ACBCI. Red Mountain Energy Partners (RMEP) was engaged to conduct the study. The ACBCI tribal lands in the Coachella Valley have very rich renewable energy resources. The tribe has undertaken several studies to more fully understand the options available to them if they were to move forward with one or more renewable energy projects. With respect to the resources, the WWR property clearly has excellent wind and solar resources. The DOE National Renewable Energy Laboratory (NREL) has continued to upgrade and refine their library of resource maps. The newer, more precise maps quantify the resources as among the best in the world. The wind and solar technology available for deployment is also being improved. Both are reducing their costs to the point of being at or below the costs of fossil fuels. Technologies for energy storage and microgrids are also improving quickly and present additional ways to increase the wind and/or solar energy retained for later use with the network management flexibility to provide power to the appropriate locations when needed. As a result, renewable resources continue to gain more market share. The transitioning to renewables as the major resources for power will take some time as the conversion is complex and can have negative impacts if not managed well. While the economics for wind and solar systems continue to improve, the robustness of the WWR site was validated by the repeated queries of developers to place wind and/or solar there. The robust resources and improving technologies portends toward WWR land as a renewable energy site. The business case, however, is not so clear, especially when the potential investment portfolio for ACBCI has several very beneficial and profitable alternatives.

Hooks, Todd; Stewart, Royce

2014-12-16

309

A Comparison of Solar Wind Parameters from tExperiments on the IMP 8 and Wind Spacecraf  

E-print Network

A Comparison of Solar Wind Parameters from tExperiments on the IMP 8 and Wind Spacecraf A. J- ent show a velocity dependence not seen in the comparison of densi- M ties from the two MIT) solar wind nstrument on the IMP 8 uses a Faraday Cup sensor which looks out in the equatorial plane

Richardson, John

310

Solar Winds Driven by Nonlinear Low-Frequency Alfven Waves from the Photosphere : Parametric Study for Fast/Slow Winds and Disappearance of Solar Winds  

E-print Network

(abridged) We investigate how the properties of the corona and solar wind in the open coronal holes depend on the properties of the magnetic fields and their footpoint motions at the surface, by perfoming 1D MHD simulations from the photosphere to 0.3 or 0.1AU. We impose low-frequency (solar wind is the universal consequence. The atmosphere is also stably heated up to >10^6K by the dissipation of the Alfven waves through compressive-wave generation and wave reflection in the case of the sufficient wave input with photospheric amplitude, > 0.7km/s. The density, and accordingly the mass flux, of solar winds show a quite sensitive dependence on because of an unstable aspect of the heating by the nonlinear Alfven waves. A case with =0.4km/s gives ~50 times smaller mass flux than the fiducial case for the fast wind with =0.7km/s; solar wind almost disappears only if becomes half. We also find that the solar wind speed has a positive correlation with B/f_max, which is consistent with recent observations. We finally show that both fast and slow solar winds can be explained by the single process, the dissipation of the low-frequency Alfven waves, with different sets of and B/f_max. Our simulations naturally explain the observed (i) anticorrelation of the solar wind speed and the coronal temperature and (ii) larger amplitude of the Alfvenic fluctuations in the fast winds. In Appendix, we also explain our implementation of the outgoing boundary condition of the MHD waves with some numerical tests.

Takeru K. Suzuki; Shu-ichiro Inutsuka

2005-10-31

311

The turbulent cascade and proton heating in the solar wind during solar minimum  

SciTech Connect

Solar wind measurements at 1 AU during the recent solar minimum and previous studies of solar maximum provide an opportunity to study the effects of the changing solar cycle on in situ heating. Our interest is to compare the levels of activity associated with turbulence and proton heating. Large-scale shears in the flow caused by transient activity are a source that drives turbulence that heats the solar wind, but as the solar cycle progresses the dynamics that drive the turbulence and heat the medium are likely to change. The application of third-moment theory to Advanced Composition Explorer (ACE) data gives the turbulent energy cascade rate which is not seen to vary with the solar cycle. Likewise, an empirical heating rate shows no significan changes in proton heating over the cycle.

Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, Colorado (United States); Forman, Miriam A. [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York (United States)

2013-06-13

312

Modulation of Saturn's radio clock by solar wind speed.  

PubMed

The internal rotation rates of the giant planets can be estimated by cloud motions, but such an approach is not very precise because absolute wind speeds are not known a priori and depend on latitude: periodicities in the radio emissions, thought to be tied to the internal planetary magnetic field, are used instead. Saturn, despite an apparently axisymmetric magnetic field, emits kilometre-wavelength (radio) photons from auroral sources. This emission is modulated at a period initially identified as 10 h 39 min 24 +/- 7 s, and this has been adopted as Saturn's rotation period. Subsequent observations, however, revealed that this period varies by +/-6 min on a timescale of several months to years. Here we report that the kilometric radiation period varies systematically by +/-1% with a characteristic timescale of 20-30 days. Here we show that these fluctuations are correlated with solar wind speed at Saturn, meaning that Saturn's radio clock is controlled, at least in part, by conditions external to the planet's magnetosphere. No correlation is found with the solar wind density, dynamic pressure or magnetic field; the solar wind speed therefore has a special function. We also show that the long-term fluctuations are simply an average of the short-term ones, and therefore the long-term variations are probably also driven by changes in the solar wind. PMID:17994092

Zarka, Philippe; Lamy, Laurent; Cecconi, Baptiste; Prangé, Renée; Rucker, Helmut O

2007-11-01

313

Interpretation of Solar Wind Composition Measurements from Ulysses  

NASA Technical Reports Server (NTRS)

Ion charge states measured in situ in interplanetary space carry information on the properties of the solar wind plasma in the inner corona. This information is, however, not easy to extract from the in situ observations. The goal of the proposal was to determine solar wind models and coronal observations that are necessary tools for the interpretation of charge state observations. It has been shown that the interpretation of the in situ ion fractions are heavily dependent on the assumptions about conditions in the inner corona.

Esser, Ruth

1999-01-01

314

Electron energy transport in the solar wind: Ulysses observations  

SciTech Connect

Previous analysis suggests that the whistler heat flux instability is responsible for the regulation of the electron heat flux of the solar wind. For an interval of quiescent solar wind during the in-ecliptic phase of the Ulysses mission, the plasma wave data in the whistler frequency regime are compared to the predictions of the whistler heat flux instability model. The data is well constrained by the predicted upper bound on the electron heat flux and a clear correlation between wave activity and electron heat flux dissipation is observed.

Scime, Earl E.; Gary, S. Peter; Phillips, John L.; Balogh, Andre; Lengyel-Frey, Denise [West Virginia University, Morgantown, West Virginia (United States); Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Blackett Laboratory, Imperial College, London (United Kingdom); University of Maryland, College Park, Maryland (United States)

1996-07-20

315

Electron energy transport in the solar wind: Ulysses observations  

SciTech Connect

Previous analysis suggests that the whistler heat flux instability is responsible for the regulation of the electron heat flux of the solar wind. For an interval of quiescent solar wind during the in-ecliptic phase of the Ulysses mission, the plasma wave data in the whistler frequency regime are compared to the predictions of the whistler heat flux instability model. The data is well constrained by the predicted upper bound on the electron heat flux and a clear correlation between wave activity and electron heat flux dissipation is observed. {copyright} {ital 1996 American Institute of Physics.}

Scime, E.E. [West Virginia University, Morgantown, West Virginia (United States); Gary, S.P.; Phillips, J.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Balogh, A. [Blackett Laboratory, Imperial College, London (United Kingdom); Lengyel-Frey, D. [University of Maryland, College Park, Maryland (United States)

1996-07-01

316

Core Electron Heating in Solar Wind Reconnection Exhausts  

NASA Astrophysics Data System (ADS)

We present observational evidence of core electron heating in solar wind reconnection exhausts. We show two example events, one which shows clear heating of the core electrons within the exhaust, and one which demonstrates no heating. The event with heating occurred during a period of high inflow Alfvén speed (V AL ), while the event with no heating had a low V AL . This agrees with the results of a recent study of magnetopause exhausts, and suggests that similar core electron heating can occur in both symmetric (solar wind) and asymmetric (magnetopause) exhausts.

Pulupa, M. P.; Salem, C.; Phan, T. D.; Gosling, J. T.; Bale, S. D.

2014-08-01

317

Solar wind kinetic instabilities at small plasma betas  

SciTech Connect

The ordinary perpendicular mode of drifting bi-Maxwellian plasma particle distributions with and without temperature anisotropy can provide aperiodic instabilities. These instabilities occur if the perpendicular thermal energy is much smaller than the streaming energy. This provides instabilities at small parallel plasma betas ?{sub ?}<1 and temperature anisotropies A?solar wind is unstable, which cannot be explained so far. To clarify if the ordinary perpendicular mode can be responsible for this instability, here we compare measurements in the solar wind with the instability provided by this mode.

Ibscher, D., E-mail: ibscher@tp4.rub.de; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)] [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

2014-02-15

318

On Polar Cap Dynamics under Strong Solar Wind Driving  

NASA Astrophysics Data System (ADS)

We investigate how polar cap dynamics, quantified by the polar cap (PC) index, respond to solar wind direct driving and magnetotail energy unloading during intervals of exceptionally large (10 mV/m) reconnection electric field. Using 53 one to two-day intervals that include such extreme fields, we find that, among 11 candidate coupling functions including the electric field of Kan and Lee (1979) and the universal coupling function of Newell et al. (2007), the PC index correlates most closely with the electric field of Kivelson and Ridley (2008), EK-R, a form in which the electric field imposed on the ionosphere by low-latitude magnetopause reconnection saturates at high levels of geomagnetic activity. It is found that nightside magnetospheric processes, as represented by an unloading AL index (ALU), make a significant contribution to the PC index. A linear model is constructed to relate the PC index to its solar wind driver and magnetotail driver, i.e. PC ? ?0 + ?1zs(EK-R) + ?2zs(ALU), where ?0, ?1 and ?2 are estimated from regression, and zs( ) is a normalization function. Based on this model, it is estimated that the portion of the PC index directly driven by the solar wind electric field outweighs the contribution arising from energy release in the magnetotail by roughly a factor of 2. The solar wind dynamic pressure (pdyn) does not play a key role in controlling the PC index. However, under intense solar wind driving, the number density (n) can influence the solar wind-magnetosphere coupling by changing the solar wind Alfvén conductance, which is incorporated in EK-R. The validity of the linear model is verified by comparing its results with those obtained from a more general, non-linear model, PC ? ? + f1(EK-R) + f2(ALU), where ? is a constant, and f1( ), f2( ) are arbitrary smooth functions. It is found that, except in anomalous events during which the auroral oval expanded poleward to the latitude of the PC index station and the index increased because of proximity to auroral zone currents, the linear model is a good approximation, since more than 70% of the variation in the PC index is explained by the model. The linear model provides a useful tool to study the coupling between the solar wind, magnetosphere and ionosphere.

Gao, Y.; Kivelson, M. G.; Walker, R. J.; Weygand, J. M.

2012-12-01

319

CHARACTERIZATION OF TRANSITIONS IN THE SOLAR WIND PARAMETERS  

SciTech Connect

The distinction between fast and slow solar wind streams and the dynamically evolved interaction regions is reflected in the characteristic fluctuations of both the solar wind and the embedded magnetic field. High-resolution magnetic field data from the Ulysses spacecraft have been analyzed. The observations show rapid variations in the magnetic field components and in the magnetic field strength, suggesting a structured nature of the solar wind at small scales. The typical sizes of fluctuations cover a broad range. If translated to the solar surface, the scales span from the size of granules ({approx}10{sup 3} km) and supergranules ({approx}10{sup 4} km) on the Sun down to {approx}10{sup 2} km and less. The properties of the short time structures change in the different types of solar wind. While fluctuations in fast streams are more homogeneous, slow streams present a bursty behavior in the magnetic field variances, and the regions of transition are characterized by high levels of power in narrow structures around the transitions. The probability density functions of the magnetic field increments at several scales reveal a higher level of intermittency in the mixed streams, which is related to the presence of well localized features. It is concluded that, apart from the differences in the nature of fluctuations in flows of different coronal origin, there is a small-scale structuring that depends on the origin of streams themselves but it is also related to a bursty generation of the fluctuations.

Perri, S.; Balogh, A., E-mail: silvia.perri@issibern.c, E-mail: a.balogh@imperial.ac.u [International Space Science Institute, Hallerstrasse 6, Bern, CH-3012 (Switzerland)

2010-02-20

320

ACCELERATION OF THE SOLAR WIND BY ALFVEN WAVE PACKETS  

SciTech Connect

A scale separation kinetic model of the solar wind acceleration is presented. The model assumes an isotropic Maxwellian distribution of protons and a constant influx of outward propagating Alfven waves with a single exponent Kolmogorov-type spectrum at the base of a coronal acceleration region ({approx}2 R {sub Sun }). Our results indicate that nonlinear cyclotron resonant interaction taking energy from Alfven waves and depositing it into mostly perpendicular heating of protons in initially weakly expanding plasma in a spherically non-uniform magnetic field is able to produce the typical fast solar wind velocities for the typical plasma and wave conditions after expansion to about 5-10 solar radii R {sub Sun }. The acceleration model takes into account the gravity force and the ambipolar electric field, as well as the mirror force, which plays the most important role in driving the solar wind acceleration. Contrary to the recent claims of Isenberg, the cold plasma dispersion only slightly slows down the acceleration and actually helps in obtaining the more realistic fast solar wind speeds.

Galinsky, V. L.; Shevchenko, V. I., E-mail: vit@ucsd.edu [ECE Department, UC San Diego, MC 407, La Jolla, CA 92093-0407 (United States)

2013-01-20

321

A reexamination of two-fluid solar wind models  

NASA Technical Reports Server (NTRS)

The two-fluid solar-wind equations have been solved by a method which is approximately 50 times faster than any previously developed, through the use of asymptotic expansions which are self-consistently iterated upon to find a solution that passes through the critical point. The energy assumptions in two-fluid solar-wind models are reexamined, and the conclusions are as follows: (1) proton thermal conduction may not be neglected, (2) the Coulomb logarithm must be calculated as a function of radius, and (3) the electron and proton temperatures at the base need not be equal, even when the time scale for energy exchange between the species is an order of magnitude smaller than the expansion time at the base. It is possible to reproduce reasonable quiet-time solar-wind parameters at 1 AU, but only if the proton temperature is approximately twice the electron temperature at 1 solar radius. This may indicate that extended proton heating is important in the outer solar corona. Winds with velocities at 1 AU of 450 km/s are generated without nonthermal energy deposition but require high proton temperatures as well as very low densities at the base. Higher-velocity solutions are not possible in a spherically symmetric geometry for reasonable particle fluxes at 1 AU, and it is suggested that these higher-velocity states probably require additional heating, acceleration mechanisms, or nonradial flow.

Nerney, S.; Barnes, A.

1977-01-01

322

The Spectroscopic Footprint of the Fast Solar Wind  

NASA Astrophysics Data System (ADS)

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1 AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the photosphere, inner heliosphere, and the mapping of the solar wind source region. We focus the bulk of our analysis on interpreting the thermal and spatial dependence of the non-thermal line widths in the ECH as measured by SOHO/SUMER by placing the measurements in context with recent studies of ubiquitous Alfvén waves in the solar atmosphere and line profile asymmetries (indicative of episodic heating and mass loading of the coronal plasma) that originate in the strong, unipolar magnetic flux concentrations that comprise the supergranular network. The results presented in this paper are consistent with a picture where a significant portion of the energy responsible for the transport of heated mass into the fast solar wind is provided by episodically occurring small-scale events (likely driven by magnetic reconnection) in the upper chromosphere and transition region of the strong magnetic flux regions that comprise the supergranular network.

McIntosh, Scott W.; Leamon, Robert J.; De Pontieu, Bart

2011-01-01

323

THE SPECTROSCOPIC FOOTPRINT OF THE FAST SOLAR WIND  

SciTech Connect

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1 AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the photosphere, inner heliosphere, and the mapping of the solar wind source region. We focus the bulk of our analysis on interpreting the thermal and spatial dependence of the non-thermal line widths in the ECH as measured by SOHO/SUMER by placing the measurements in context with recent studies of ubiquitous Alfven waves in the solar atmosphere and line profile asymmetries (indicative of episodic heating and mass loading of the coronal plasma) that originate in the strong, unipolar magnetic flux concentrations that comprise the supergranular network. The results presented in this paper are consistent with a picture where a significant portion of the energy responsible for the transport of heated mass into the fast solar wind is provided by episodically occurring small-scale events (likely driven by magnetic reconnection) in the upper chromosphere and transition region of the strong magnetic flux regions that comprise the supergranular network.

McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Leamon, Robert J. [ADNET Systems Inc., NASA Goddard Space Flight Center, Code 671.1, Greenbelt, MD 20771 (United States); De Pontieu, Bart, E-mail: mscott@ucar.edu, E-mail: robert.j.leamon@nasa.gov, E-mail: bdp@lmsal.com [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover Street, Org. ADBS, Building 252, Palo Alto, CA 94304 (United States)

2011-01-20

324

Knowledge of coronal heating and solar-wind acceleration obtained from observations of the solar wind near 1 AU  

NASA Technical Reports Server (NTRS)

Clues to the nature of the mechanisms responsible for heating the corona and accelerating the solar wind can be obtained by contrasting the properties of the quasi-stationary and transient states of the solar wind. Substantial differences exist in the proton temperatures and anisotropies, the entropy, the field strength, the Alfvenicity of fluctuations in the field, the distribution of MHD discontinuities, and the helium abundance of the two types of flow. Those differences are displayed as a function of the solar wind speed. Several signals of wave acceleration can be found in the data for quasi-stationary flows. The relatively smooth velocity dependences of proton temperature, helium abundance, and frequency of occurrence of rotational discontinuities suggest that the acceleration mechanisms for flow from coronal holes, coronal streamers, and the quasi-stationary low-speed flows between them may be basically the same, differing only in degree.

Neugebauer, M.

1992-01-01

325

A new method to estimate annual solar wind parameters and contributions of different solar wind structures to geomagnetic activity  

E-print Network

In this paper, we study two sets of local geomagnetic indices from 26 stations using the principal component (PC) and the independent component (IC) analysis methods. We demonstrate that the annually averaged indices can be accurately represented as linear combinations of two first components with weights systematically depending on latitude. We show that the annual contributions of coronal mass ejections (CMEs) and high speed streams (HSSs) to geomagnetic activity are highly correlated with the first and second IC. The first and second ICs are also found to be very highly correlated with the strength of the interplanetary magnetic field (IMF) and the solar wind speed, respectively, because solar wind speed is the most important parameter driving geomagnetic activity during HSSs while IMF strength dominates during CMEs. These results help in better understanding the long-term driving of geomagnetic activity and in gaining information about the long-term evolution of solar wind parameters and the different sol...

Holappa, Lauri; Asikainen, Timo

2015-01-01

326

Exploring the Solar Wind and Coronal Mass Ejections  

NSDL National Science Digital Library

This is an activity about the solar activity cycle. Learners will construct a graph to identify a pattern of the number of observed sunspots and the number of coronal mass ejections emitted by the Sun over a fifteen year time span. A graphing calculator is recommended, but not required, for this activity. This is the second activity in the Solar Storms and You: Exploring the Wind from the Sun educator guide.

327

The electric potential of the moon in the solar wind  

NASA Technical Reports Server (NTRS)

Acceleration and detection of the lunar thermal ionosphere in the presence of the lunar electric field yields a value of approximately +10 V for the lunar electric potential for solar zenith angles between 20 and 45 deg and in the magnetosheath or solar wind. The ion number density of the thermal ionosphere observed is compatible with a surface neutral number density of about 100,000 atoms/cu cm.

Freeman, J. W., Jr.; Fenner, M. A.; Hills, H. K.

1973-01-01

328

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind A. Bhattacharjee and C. S. Ng  

E-print Network

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind A. Bhattacharjee and C. S. Ng turbulence in the interstellar medium and the solar wind. The model is motivated by observations that show

Ng, Chung-Sang

329

78 FR 77447 - California Wind Energy Association, First Solar, Inc. v. California Independent System Operator...  

Federal Register 2010, 2011, 2012, 2013

...Docket No. EL14-14-000] California Wind Energy Association, First Solar, Inc. v. California Independent System...18 CFR 385.206 (2013), California Wind Energy Association and First Solar, Inc. (collectively,...

2013-12-23

330

Slow and fast solar wind - data selection and statistical analysis  

NASA Astrophysics Data System (ADS)

In this work we consider the important problem of selection of slow and fast solar wind data measured in-situ by the Ulysses spacecraft during two solar minima (1995-1997, 2007-2008) and solar maximum (1999-2001). To recognise different types of solar wind we use a set of following parameters: radial velocity, proton density, proton temperature, the distribution of charge states of oxygen ions, and compressibility of magnetic field. We present how this idea of the data selection works on Ulysses data. In the next step we consider the chosen intervals for fast and slow solar wind and perform statistical analysis of the fluctuating magnetic field components. In particular, we check the possibility of identification of inertial range by considering the scale dependence of the third and fourth orders scaling exponents of structure function. We try to verify the size of inertial range depending on the heliographic latitudes, heliocentric distance and phase of the solar cycle. Research supported by the European Community's Seventh Framework Programme (FP7/2007 - 2013) under grant agreement no 313038/STORM.

Wawrzaszek, Anna; Macek, Wies?aw M.; Bruno, Roberto; Echim, Marius

2014-05-01

331

Elemental and isotopic abundances in the solar wind  

NASA Technical Reports Server (NTRS)

The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

Geiss, J.

1972-01-01

332

Anisotropic winds from close-in extra-solar planets  

E-print Network

We present two-dimensional hydrodynamic models of thermally driven winds from highly irradiated, close-in extra-solar planets. We adopt a very simple treatment of the radiative heating processes at the base of the wind, and instead focus on the differences between the properties of outflows in multidimensions in comparison to spherically symmetric models computed with the same methods. For hot (T > 2 x 10^{4} K) or highly ionized gas, we find strong (supersonic) polar flows are formed above the planet surface which produce weak shocks and outflow on the night-side. In comparison to a spherically symmetric wind with the same parameters, the sonic surface on the day-side is much closer to the planet surface in multidimensions, and the total mass loss rate is reduced by almost a factor of four. We also compute the steady-state structure of interacting planetary and stellar winds. Both winds end in a termination shock, with a parabolic contact discontinuity which is draped over the planet separating the two shocked winds. The planetary wind termination shock and the sonic surface in the wind are well separated, so that the mass loss rate from the planet is essentially unaffected. However, the confinement of the planetary wind to the small volume bounded by the contact discontinuity greatly enhances the column density close to the planet, which might be important for the interpretation of observations of absorption lines formed by gas surrounding transiting planets.

James M. Stone; Daniel Proga

2008-12-13

333

A Model fot the Sources of the Slow Solar Wind  

NASA Technical Reports Server (NTRS)

Models for the origin of the slow solar wind must account for two seemingly contradictory observations: the slow wind has the composition of the closed-field corona, implying that it originates from the continuous opening and closing of flux at the boundary between open and closed field. On the other hand, the slow wind also has large angular width, up to approx.60deg, suggesting that its source extends far from the open-closed boundary. We propose a model that can explain both observations. The key idea is that the source of the slow wind at the Sun is a network of narrow (possibly singular) open-field corridors that map to a web of separatrices and quasi-separatrix layers in the heliosphere. We compute analytically the topology of an open-field corridor and show that it produces a quasi-separatrix layer in the heliosphere that extends to angles far from the heliospheric current sheet. We then use an MHD code and MDI/SOHO observations of the photospheric magnetic field to calculate numerically, with high spatial resolution, the quasi-steady solar wind, and magnetic field for a time period preceding the 2008 August 1 total solar eclipse. Our numerical results imply that, at least for this time period, a web of separatrices (which we term an S-web) forms with sufficient density and extent in the heliosphere to account for the observed properties of the slow wind. We discuss the implications of our S-web model for the structure and dynamics of the corona and heliosphere and propose further tests of the model. Key words: solar wind - Sun: corona - Sun: magnetic topology

Antiochos, S. K.; Mikic, Z.; Titov, V. S.; Lionello, R.; Linker, J. A.

2011-01-01

334

Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer  

Microsoft Academic Search

The Solar Wind Electron Proton Alpha Monitor (SWEPAM) experiment provides the bulk solar wind observations for the Advanced\\u000a Composition Explorer (ACE). These observations provide the context for elemental and isotopic composition measurements made\\u000a on ACE as well as allowing the direct examination of numerous solar wind phenomena such as coronal mass ejections, interplanetary\\u000a shocks, and solar wind fine structure, with

D. J. McComas; S. J. Bame; P. Barker; W. C. Feldman; J. L. Phillips; P. Riley; J. W. Griffee

1998-01-01

335

Investigations to Determine the Origin of the Solar Wind with SPICE and SolarOrbiter  

NASA Astrophysics Data System (ADS)

At large spatial scales, the structure of the solar wind and it's mapping back to the solar corona, is thought to be reasonably well understood. However, the detailed structure of the various source regions at chromospheric and transition region heights is extremely complex, and less well understood. Determining this connection between heliospheric structures and their source regions at the Sun is one of the overarching objective of the Solar Orbiter mission. During perihelion segments of its orbit, when the spacecraft is in quasi-corotation with the Sun, Solar Orbiter will determine the plasma parameters and compositional signatures of the solar wind, which can be compared directly with the spectroscopic signatures of coronal ions with differing charge-to-mass ratios and FIP. One of the key instruments on the Solar Orbiter mission to make these remote sensing measurements is the SPICE (Spectral Imaging of the Coronal Environment) imaging spectrograph. SPICE will provide the images and plasma diagnostics needed to characterize the plasma state in different source regions, from active regions to quiet Sun to coronal holes. By comparing composition, plasma parameters, and low/high FIP ratios of structures remotely, with those measured directly at the Solar Orbiter spacecraft, Solar Orbiter will provide the first direct link between solar wind structures and their source regions at the Sun. This talk will provide a background of previous compositional correlation measurements and an outline of the method to be used for comparing the spectroscopic and in-situ plasma parameters to be measured with Solar Orbiter.

Hassler, Donald M.; DeForest, C.; Wilkinson, E.; Davila, J.; SPICE Team

2011-05-01

336

Electric Solar Wind Sail (E-sail) mission to asteroids  

NASA Astrophysics Data System (ADS)

There are an estimated one to two million asteroids of diameter over 1 km in-between the orbits of Mars and Jupiter. Impact threat, mining prospects and the understanding of solar system history make asteroids interesting objects for further in-situ studies. Electric Solar Wind Sail (E-sail) [1] technology enables touring several different asteroids with the same spacecraft. It is a propulsion technology first proposed in 2006 and currently developed with the EUs FP7 funding (http://www.electric-sailing.fi/fp7). The E-sail utilizes long, conducting, highly charged tethers to gather momentum from the solar wind ions. It does not consume any propellant and is well maneuverable. The Electric Solar Wind Sail producing 1 N of thrust at 1 AU distance from the Sun could be manufactured to weigh 100-150 kg in total. The constant acceleration gives a large advantage over traditional methods when calculated over the mission lifetime. In a ten year mission a baseline 1 N E-sail could produce 300 MNs of total impulse, Itot. As an example, such a total impulse would be able to move a 3 million ton Earth-threatening asteroid to a safer track [2]. With chemical propellant it would take 100 000 tons of fuel to achieve the same feat. Scientists and miners could have a closer look at several targets and they could decide the next target and the duration of investigations once at the vicinity of the asteroid, so the operations would be very flexible. Such a mission could characterize and map several asteroids, some with rapid fly-bys and a few chosen ones during lengthier rendezvous. [1] Janhunen, P., et. al, Electric solar wind sail: Towards test missions (Invited article), Rev. Sci. Instrum., 81, 111301, 2010. [2] Merikallio, S. and P. Janhunen, Moving an asteroid with electric solar wind sail, Astrophys. Space Sci. Trans., 6, 41-48, 2010

Merikallio, Sini; Janhunen, Pekka; Toivanen, Petri; Jouni Envall, M.(Tech.).

2012-07-01

337

Turbulence and Waves as Sources for the Solar Wind  

NASA Astrophysics Data System (ADS)

Gene Parker's insights from 50 years ago provided the key causal link between energy deposition in the solar corona and the acceleration of solar wind streams. However, the community is still far from agreement concerning the actual physical processes that give rise to this energy. It is still unknown whether the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wavelike fluctuations) or if mass and energy is input more intermittently from closed loops into the open-field regions. No matter the relative importance of reconnections and loop-openings, though, we do know that waves and turbulent motions are present everywhere from the photosphere to the heliosphere, and it is important to determine how they affect the mean state of the plasma. In this presentation, I will give a summary of wave/turbulence models that seem to succeed in explaining the time-steady properties of the corona (and the fast and slow solar wind). The coronal heating and solar wind acceleration in these models comes from anisotropic turbulent cascade, which is driven by the partial reflection of low-frequency Alfven waves propagating along the open magnetic flux tubes. Specifically, a 2D model of coronal holes and streamers at solar minimum reproduces the latitudinal bifurcation of slow and fast streams seen by Ulysses. The radial gradient of the Alfven speed affects where the waves are reflected and damped, and thus whether energy is deposited below or above Parker's critical point. As predicted by earlier studies, a larger coronal expansion factor gives rise to a slower and denser wind, higher temperature at the coronal base, less intense Alfven waves at 1 AU, and correlative trends for commonly measured ratios of ion charge states and FIP-sensitive abundances that are in general agreement with observations. Finally, I will outline the types of future observations that would be most able to test and refine these ideas.

Cranmer, S. R.

2008-05-01

338

Solar Wind Characteristics from SOHO-Sun-Ulysses Quadrature Observations  

NASA Technical Reports Server (NTRS)

Over the past few years, we have been running SOHO (Solar and Heliospheric Observatory)-Sun-Ulysses quadrature campaigns, aimed at comparing the plasma properties at coronal altitudes with plasma properties at interplanetary distances. Coronal plasma has been observed by SOHO experiments: mainly, we used LASCO (Large Angle and Spectrometric Coronagraph Experiment) data to understand the overall coronal configuration at the time of quadratures and analyzed SUMER (Solar Ultraviolet Measurements of Emitted Radiation), CDS (Coronal Diagnostic Spectrometer) and UVCS (Ultraviolet Coronagraph Spectrometer) data to derive its physical characteristics. At interplanetary distances, SWICS (Solar Wind Ion Composition Spectrometer) and SWOOPS (Solar Wind Observation over the Poles of the Sun) aboard Ulysses provided us with interplanetary plasma data. Here we report on results from some of the campaigns. We notice that, depending on the geometry of the quadrature, i.e. on whether the radial to Ulysses traverses the corona at high or low latitudes, we are able to study different kinds of solar wind. In particular, a comparison between low-latitude and high-latitude wind, allowed us to provide evidence for differences in the acceleration of polar, fast plasma and equatorial, slow plasma: the latter occurring at higher levels and through a more extended region than fast wind. These properties are shared by both the proton and heavy ions outflows. Quadrature observations may provide useful information also on coronal vs. in situ elemental composition. To this end, we analyzed spectra taken in the corona, at altitudes ranging between approx. 1.02 and 2.2 solar radii, and derived the abundances of a number of ions, including oxygen and iron. Values of the O/Fe ratio, at coronal levels, have been compared with measurements of this ratio made by SWICS at interplanetary distances. Our results are compared with previous findings and predictions from modeling efforts.

Poletto, Giannina; Suess, Steve T.; Six, N. Frank (Technical Monitor)

2002-01-01

339

The Eect of the Tilt of the HCS on the Solar Wind Speed in the Outer Heliosphere  

E-print Network

1 The Eect of the Tilt of the HCS on the Solar Wind Speed in the Outer Heliosphere J. D. Richardson: THE HCS TILT AND THE SOLAR WIND SPEED #12;2 Abstract. The ow of solar wind from the Sun is bimodal. High with the HCS tilt controls the solar wind velocities in the outer heliosphere near solar minimum when the Sun

Richardson, John

340

VENUS EXPRESS STUDIES PERTAINING TO THE LOSS OF THE VENUS ATMOSPHERE BY ITS INTERACTION WITH THE SOLAR WIND  

E-print Network

WITH THE SOLAR WIND C. T. Russell, T. L. Zhang, M. Delva, S. Barabash, J. G. Luhmann, and H. Y. Wei The solar effectively excludes the solar wind from the planetary atmosphere but that the solar wind can still erode is consistent with the deflection of the solar wind plasma by the magnetic barrier that in turn shields

California at Berkeley, University of

341

Development of the 3-D MHD model of the solar corona-solar wind combining system  

Microsoft Academic Search

In the framework of integrated numerical space weather prediction, we have developed a 3-D MHD simulation model of the solar surface-solar wind system. We report the construction method of the model and its first results. By implementing a grid system with angularly unstructured and increasing radial spacing, we realized a spherical grid that has no pole singularity and realized a

A. Nakamizo; T. Tanaka; Y. Kubo; S. Kamei; H. Shimazu; H. Shinagawa

2009-01-01

342

Implications of the Recent Low Solar Minimum for the Solar Wind during the Maunder Minimum  

NASA Astrophysics Data System (ADS)

The behavior of the Sun and near-Earth space during grand solar minima is not understood; however, the recent long and low minimum of the decadal-scale solar cycle gives some important clues, with implications for understanding the solar dynamo and predicting space weather conditions. The speed of the near-Earth solar wind and the strength of the interplanetary magnetic field (IMF) embedded within it can be reliably reconstructed for before the advent of spacecraft monitoring using observations of geomagnetic activity that extend back to the mid-19th century. We show that during the solar cycle minima around 1879 and 1901 the average solar wind speed was exceptionally low, implying the Earth remained within the streamer belt of slow solar wind flow for extended periods. This is consistent with a broader streamer belt, which was also a feature of the recent low minimum (2009), and yields a prediction that the low near-Earth IMF during the Maunder minimum (1640-1700), as derived from models and deduced from cosmogenic isotopes, was accompanied by a persistent and relatively constant solar wind of speed roughly half the average for the modern era.

Lockwood, M.; Owens, M. J.

2014-01-01

343

Prediction of daily average solar wind velocity from solar magnetic field observations using hybrid intelligent systems  

Microsoft Academic Search

A hybrid intelligent system, combining theory driven and data driven models, is used to predict the daily solar wind velocity at 1 AU from solar magnetic field observations. The Potential Field Model (theory driven) is used to calculate the coronal magnetic field up to the source surface placed at 2.5R?. The Earth's position is projected onto the source surface using

P. Wintoft; H. Lundstedt

1997-01-01

344

Transport of solar wind into Earth's magnetosphere through rolled-up Kelvin-Helmholtz vortices  

Microsoft Academic Search

Establishing the mechanisms by which the solar wind enters Earth's magnetosphere is one of the biggest goals of magnetospheric physics, as it forms the basis of space weather phenomena such as magnetic storms and aurorae. It is generally believed that magnetic reconnection is the dominant process, especially during southward solar-wind magnetic field conditions when the solar-wind and geomagnetic fields are

H. Hasegawa; M. Fujimoto; T.-D. Phan; H. Rème; A. Balogh; M. W. Dunlop; C. Hashimoto; R. TanDokoro

2004-01-01

345

A review of solar wind ion and electron plasma distributions: Present understanding and Ulysses results  

SciTech Connect

Unlike the oral version of this paper at Solar Wind 8, this written version is not intended as an overview of the observational aspects of solar wind ion and electron distributions, but discusses only recent results in this area with emphasis on Ulysses measurements. Although primarily a review, some new results on solar wind proton temperatures at high latitudes are presented.

Goldstein, B. E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109 (United States)

1996-07-20

346

Kinetic And Potential Sputtering Of Lunar Regolith: The Contribution Of The Heavy (Minority) Solar Wind Ions  

E-print Network

, Huntsville, AL 35812, USA Abstract. In this paper the sputtering of lunar regolith by protons and solar wind of JSC-1A AGGL lunar regolith simulant at solar wind velocities, and TRIM simulations of kinetic to the minority heavy ion multicharged ion solar wind component, and the kinetic sputtering contribution of all

347

Enhanced solar wind geoeffectiveness after a sudden increase in dynamic pressure during southward IMF orientation  

E-print Network

Enhanced solar wind geoeffectiveness after a sudden increase in dynamic pressure during southward increase in solar wind pressure results in poleward expansion of the auroral oval and closing of the polar show that southward IMF conditions combined with high solar wind dynamic pressure immediately after

Lummerzheim, Dirk

348

The Solar Wind: Probing the Heliosphere with Multiple Spacecraft John D. Richardson  

E-print Network

1 The Solar Wind: Probing the Heliosphere with Multiple Spacecraft John D. Richardson Center of the Voyager spacecraft in the outer heliosphere, Ulysses at high latitudes, and multiple solar wind monitors near Earth provides a unique opportunity to study the global structure and evolution of the solar wind

Richardson, John

349

THE SOLAR WIND INTERACTION WITH UNMAGNETIZED PLANETS: A TUTORIAL J. G. Luhmann  

E-print Network

THE SOLAR WIND INTERACTION WITH UNMAGNETIZED PLANETS: A TUTORIAL J. G. Luhmann Institute of solar wind origin is transported through the ionopause and distributed within the ionosphere theorists and observationalists. The relative strength of the solar wind and ionospheric pressures at Mars

California at Berkeley, University of

350

Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study  

E-print Network

Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail and the solar wind, as well as >2 MeV geosynchronous electrons, is investigated using plasma sheet measurements from Cluster (2001­2005) and Geotail (1998­2005) and concurrent solar wind measurements from ACE

Li, Xinlin

351

Source regions of solar wind disappearance events P. Janardhan,1,3  

E-print Network

Source regions of solar wind disappearance events P. Janardhan,1,3 K. Fujiki,2 H. S. Sawant,3 M, in May 1999, March 2002, and May 2002, respectively, when the solar wind densities at 1 AU dropped-density anomalies observed at 1 AU are referred to as ``solar wind disappearance events'' and in this paper, we

Padmanabhan, Janardhan

352

The Solar Wind Interaction with the Earth's Magnetosphere: A Tutorial C. T. Russell  

E-print Network

The Solar Wind Interaction with the Earth's Magnetosphere: A Tutorial C. T. Russell Department field. The shape of the magnetosphere is additionally influenced by the drag of the solar wind as reconnection in which the magnetic field of the solar wind links with the magnetic field of the magnetosphere

Russell, Christopher T.

353

Global and multi-scale features of solar wind-magnetosphere coupling: From modeling to forecasting  

E-print Network

Global and multi-scale features of solar wind-magnetosphere coupling: From modeling to forecasting is a spatially extended nonlinear system driven far from equilibrium by the turbulent solar wind. During issue. This paper presents a data-derived model of the solar wind-magnetosphere coupling that combines

Sitnov, Mikhail I.

354

Solar Wind and Interplanetary Magnetic Field: A Tutorial C. T. Russell  

E-print Network

Solar Wind and Interplanetary Magnetic Field: A Tutorial C. T. Russell Institute of Geophysics at the center of the sun to its radiation into space by the photosphere, but most importantly for the solar wind controls the properties of the solar wind. In this tutorial review we examine the properties of the fields

Russell, Christopher T.

355

A SURVEY OF FIELD-ALIGNED MACH NUMBER AND PLASMA BETA IN THE SOLAR WIND  

E-print Network

A SURVEY OF FIELD-ALIGNED MACH NUMBER AND PLASMA BETA IN THE SOLAR WIND JOHAN DE KEYSER and MICHEL Katholieke Universiteit Leuven, Leuven, Belgium Abstract. We have surveyed solar wind plasma beta and field frequency of `magnet- ically dominated' solar wind, whose interaction with a planetary magnetosphere may

De Sterck, Hans

356

Impact of the solar wind dynamic pressure on the Region 2 field-aligned currents  

E-print Network

Impact of the solar wind dynamic pressure on the Region 2 field-aligned currents S. Nakano,1,2 G and the solar wind dynamic pressure is investigated using magnetic field data from Defense Meteorological in the magnetosphere varies with the solar wind dynamic pressure. Therefore, we can expect that the Region 2 currents

Higuchi, Tomoyuki

357

Discrepancies in the Prediction of Solar Wind using Potential Field Source Surface Model: An  

E-print Network

Discrepancies in the Prediction of Solar Wind using Potential Field Source Surface Model between the magnetic flux tube expansion factor (FTE) at the source surface and the solar wind speed observed at Earth, which has been made use of in the prediction of solar wind speed near the Earth

Zhao, Xuepu

358

Gap filling of solar wind data by singular spectrum analysis D. Kondrashov,1  

E-print Network

Gap filling of solar wind data by singular spectrum analysis D. Kondrashov,1 Y. Shprits,1 and M field are crucial for many space weather applications, and require timecontinuous solar wind in solar wind and IMF data, by com- bining it with geomagnetic indices that are timecontinuous

Ghil, Michael

359

Kolmogorov versus IroshnikovKraichnan spectra: Consequences for ion heating in the solar wind  

E-print Network

heating in the solar wind C. S. Ng,1 A. Bhattacharjee,2 D. Munsi,2 P. A. Isenberg,2 and C. W. Smith2. Recently, a solar wind heating model based on Kolmogorov spectral scaling has produced reasonably good), Kolmogorov versus Iroshnikov Kraichnan spectra: Consequences for ion heating in the solar wind, J. Geophys

Ng, Chung-Sang

360

A TRANSONIC COLLISIONLESS MODEL OF THE SOLAR WIND I. Zouganelis,1  

E-print Network

A TRANSONIC COLLISIONLESS MODEL OF THE SOLAR WIND I. Zouganelis,1 M. Maksimovic,1 N. Meyer-Vernet,1 of the semicollisional nature of the solar wind, the collisionless or exospheric approach and the hydrodynamic one basic mechanisms of solar wind acceleration. Previous exospheric models have been able to re- produce

Meyer-Vernet, Nicole

361

Effect of solar wind pressure pulses on the size and strength of the auroral oval  

E-print Network

Effect of solar wind pressure pulses on the size and strength of the auroral oval A. Boudouridis, E. [1] It has recently been found that solar wind dynamic pressure changes can dramatically affect solar wind dynamic pressure increases on the location, size, and intensity of the auroral oval using

Lummerzheim, Dirk

362

J. Astrophys. Astr. (2006) 27, 17 Enigmatic Solar Wind Disappearance Events Do We Understand  

E-print Network

J. Astrophys. Astr. (2006) 27, 1­7 Enigmatic Solar Wind Disappearance Events ­ Do We Understand@prl.ernet.in Abstract. At the Sun­Earth distance of one astronomical unit (1 AU), the solar wind is known to be strongly, solar wind densities (average 10 cm-3 ) and velocities (average 450 km s-1 ) at 1 AU, are known

Padmanabhan, Janardhan

363

The orientation of plasma structure in the solar wind J. D. Richardson and K. I. Paularena  

E-print Network

The orientation of plasma structure in the solar wind J. D. Richardson and K. I. Paularena Center, and WIND spacecraft are used to #12;nd the average east-west orientation of plasma structures in the solar correlations between data sets. These lags, when combined with the spacecraft positions and solar wind speeds

Richardson, John

364

THE GENESIS SOLAR-WIND COLLECTOR MATERIALS A. J. G. Jurewicz1  

E-print Network

THE GENESIS SOLAR-WIND COLLECTOR MATERIALS A. J. G. Jurewicz1 , D. S. Burnett2 , R. C. Wiens3 , T. #12;THE GENESIS SOLAR-WIND COLLECTOR MATERIALS Abstract. Genesis (NASA Discovery Mission #5 to maximize the area for solar-wind collection. Most of the collection area consists of hexagonal collectors

365

Prediction of the AL index using solar wind Xinlin Li,1,2,5  

E-print Network

Prediction of the AL index using solar wind parameters Xinlin Li,1,2,5 Kap Soo Oh,1,3 and M are based on solar wind and magnetometer data from the year 1995. The simple model predicts the 10-min averaged AL index for 1995 using only solar wind measurements with a prediction efficiency of 0

Li, Xinlin

366

Intermittent release of transients in the slow solar wind: 2. In situ evidence  

E-print Network

Click Here for Full Article Intermittent release of transients in the slow solar wind: 2. In situ, the variability of the slow solar wind which originates near helmet streamers. The observation of intense intermittent transient outflow by HI implies that the corresponding in situ observations of the slow solar wind

California at Berkeley, University of

367

Imaging the global solar wind flow in EUV Mike Gruntman,1  

E-print Network

Imaging the global solar wind flow in EUV Mike Gruntman,1 Vlad Izmodenov,2,3 and Vic Pizzo4] We advance the original concept of imaging the three-dimensional solar wind flow (Gruntman, 2001a) by characterizing expected heliospheric EUV signatures under assumptions of a realistic solar wind. Charge exchange

Gruntman, Mike

368

The structure and origin of magnetic clouds in the solar wind V. Bothmer1  

E-print Network

The structure and origin of magnetic clouds in the solar wind V. Bothmer1 * and R. Schwenn2 1 Space in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large- scale to be proportional to RÃ?2X4 , thus being stronger compared to the average solar wind. Four dierent magnetic con

Boyer, Edmond

369

Petschek-type magnetic reconnection exhausts in the solar wind well inside 1 AU: Helios  

E-print Network

Petschek-type magnetic reconnection exhausts in the solar wind well inside 1 AU: Helios J. T; published 5 October 2006. [1] Petschek-type reconnection exhausts can be recognized in solar wind plasma in the solar wind inward to heliocentric distances of 0.31 AU. Most of the exhaust jets identified

Eriksson, Stefan

370

Modeling magnetospheric current response to solar wind dynamic pressure enhancements during magnetic storms  

E-print Network

), Modeling magnetospheric current response to solar wind dynamic pressure enhancements during magnetic storms-latitude and midlatitude ground H component to solar wind dynamic pressure enhancements during several magnetic storms, ShiModeling magnetospheric current response to solar wind dynamic pressure enhancements during

Lyons, Larry

371

Multiple-spacecraft study of an extended magnetic structure in the solar wind  

E-print Network

Multiple-spacecraft study of an extended magnetic structure in the solar wind P. Ruan,1 A. Korth,1 A and B, and CLUSTER) in the solar wind on 15 January 2007. The similar bipolar magnetic field variations-spacecraft study of an extended magnetic structure in the solar wind, J. Geophys. Res., 114, A02108, doi:10

Wiegelmann, Thomas

372

Asteroid surface processes: Experimental studies of the solar wind on reflectance and optical properties of asteroids  

NASA Technical Reports Server (NTRS)

The effect of the solar wind on the optical properties of meteorites was studied to determine whether the solar wind can alter the properties of ordinary chondrite parent bodies resulting in the spectral properties of S-type asteroids. The existing database of optical properties of asteroids was analyzed to determine the effect of solar wind in altering asteroid surface properties.

Mcfadden, Lucy-Ann

1991-01-01

373

The genesis solar-wind sample return mission  

SciTech Connect

The compositions of the Earth's crust and mantle, and those of the Moon and Mars, are relatively well known both isotopically and elementally. The same is true of our knowledge of the asteroid belt composition, based on meteorite analyses. Remote measurements of Venus, the Jovian atmosphere, and the outer planet moons, have provided some estimates of their compositions. The Sun constitutes a large majority, > 99%, of all the matter in the solar system. The elemental composition of the photosphere, the visible 'surface' of the Sun, is constrained by absorption lines produced by particles above the surface. Abundances for many elements are reported to the {+-}10 or 20% accuracy level. However, the abundances of other important elements, such as neon, cannot be determined in this way due to a relative lack of atomic states at low excitation energies. Additionally and most importantly, the isotopic composition of the Sun cannot be determined astronomically except for a few species which form molecules above sunspots, and estimates derived from these sources lack the accuracy desired for comparison with meteoritic and planetary surface samples measured on the Earth. The solar wind spreads a sample of solar particles throughout the heliosphere, though the sample is very rarified: collecting a nanogram of oxygen, the third most abundant element, in a square centimeter cross section at the Earth's distance from the Sun takes five years. Nevertheless, foil collectors exposed to the solar wind for periods of hours on the surface of the Moon during the Apollo missions were used to determine the helium and neon solar-wind compositions sufficiently to show that the Earth's atmospheric neon was significantly evolved relative to the Sun. Spacecraft instruments developed subsequently have provided many insights into the composition of the solar wind, mostly in terms of elemental composition. These instruments have the advantage of observing a number of parameters simultaneously, including charge state distributions, velocities, and densities, all of which have been instrumental in characterizing the nature of the solar wind. However, these instruments have lacked the ability to make large dynamic range measurements of adjacent isotopes (i.e., {sup 17}O/{sup 16}O {approx} 2500) or provide the permil (tenths of percent) accuracy desirable for comparison with geochemical isotopic measurements. An accurate knowledge of the solar and solar-wind compositions helps to answer important questions across a number of disciplines. It aids in understanding the acceleration mechanisms of the solar wind, gives an improved picture of the charged particle environment near the photosphere, it constrains processes within the Sun over its history, and it provides a database by which to compare differences among planetary systems with the solar system's starting composition, providing key information on planetary evolution. For example, precise knowledge of solar isotopic and elemental compositions of volatile species in the Sun provides a baseline for models of atmospheric evolution over time for Earth, Venus, and Mars. Additionally, volatile and chemically active elements such as C, H, O, N, and S can tell us about processes active during the evolution of the solar nebula. A classic example of this is the oxygen isotope system. In the 1970s it was determined that the oxygen isotopic ratio in refractory inclusions in primitive meteorites was enriched {approx}4% in {sup 16}O relative to the average terrestrial, lunar, and thermally processed meteorite materials. In addition, all processed solar-system materials appeared to each have a unique oxygen isotopic composition (except the Moon and Earth, which are thought to be formed from the same materials), though differences are in the fraction of a percent range, much smaller than the refractory material {sup 16}O enrichment. Several theories were developed over the years to account for the oxygen isotope heterogeneity, each theory predicting a different solar isotopic composition and each invoking a differ

Wiens, Roger C [Los Alamos National Laboratory

2009-01-01

374

Probabilistic performance assessment of autonomous solar-wind energy conversion systems  

Microsoft Academic Search

This paper describes the development of a general probabilistic model of an autonomous solar-wind energy conversion system (SWECS) composed of several wind turbines (wind farm), several photovoltaic (PV) modules (solar park), and a battery storage feeding a load. The model takes into consideration outages due to the primary energy fluctuations and hardware failure. It allows the simulation of wind farms

S. H. Karaki; R. B. Chedid; R. Ramadan

1999-01-01

375

On a magnetosphere disturbed by solar wind; observations of macroelectrons  

NASA Astrophysics Data System (ADS)

Three-dimensional electromagnetic full kinetic particle code (a version of TRISTAN) is used to study the interaction of a weakly-magnetized object with a solar wind of low density. The details of two magnetospheric processes - wave activity and energetic electrons appearing at the flanks of the magnetosphere - are presented. The results of the simulation are compared with known magnetospheric data.

Wodnicka, E. B.

2009-06-01

376

A hybrid reconfigurable solar and wind energy system  

Microsoft Academic Search

We study the feasibility of a novel hybrid solar-wind hybrid system that shares most of its infrastructure and components. During periods of clear sunny days the system will generate electricity from the sun using a parabolic concentrator. The concentrator is formed by individual mirror elements and focuses the light onto high intensity vertical multi-junction (VMJ) cells. During periods of high

Sagar A. Gadkari

2008-01-01

377

Fast Solar Wind Monitor (BMSW): Description and First Results  

NASA Astrophysics Data System (ADS)

Monitoring of solar wind parameters is a key problem of the Space Weather program. The paper presents a description of a novel fast solar wind monitor (Bright Monitor of the Solar Wind, BMSW) and the first results of its measurements of plasma moments with a time resolution ranging from seconds to 31 ms. The method of the fast monitoring is based on simultaneous measurements of the total ion flux and ion integral energy spectrum by six nearly identical Faraday cups (FCs). Three of them are dedicated to determination of the ion flow direction, whereas other three equipped with control grids supplied by a retarding potential are used for a determination of the density, temperature, and speed of the plasma flow. The paper introduces not only the measuring methods, the FCs design, and modes of operation, but brings the examples of time series of measurements and their comparison with the observations of other spacecraft as well as the first results of an analysis of frequency spectra of solar wind fluctuations within the ion kinetic scale, examples of rapid measurements at the ramp of an interplanetary shock and investigations of fast variations of alpha particle content.

Šafránková, Jana; N?me?ek, Zden?k; P?ech, Lubomír; Zastenker, Georgy; ?ermák, Ivo; Chesalin, Lev; Komárek, Arnošt; Vaverka, Jakub; Beránek, Martin; Pavl?, Ji?í; Gavrilova, Elena; Karimov, Boris; Leibov, Arkadii

2013-06-01

378

Large scale solar wind structures and equatorial ionospheric variations  

NASA Astrophysics Data System (ADS)

We examined equatorial ionospheric variations during geomagnetic storms associated with large scale solar wind structures. Yohkoh, SOHO and Ulysses missions proved that in general, the mass emissions from the Sun as interplanetary coronal mass ejections (ICMEs), corotating interaction regions (CIRs), and heliospheric current sheet (HCS) are responsible for generation of different types of geomagnetic storms. Intensive ionospheric currents during these types of geomagnetic storms change the quiet ionosphere and short-term variations of the ionospheric characteristics are observed. Under these conditions the critical frequency foF2, virtual height h’F, drift velocities and others ionospheric characteristics are mainly defined by the the state of the solar wind flowing around the Earth's magnetosphere. We show that these variations are defined to a significant degree by the direction of the Bz-component of the interplanetary magnetic field but duration and intensity of these variations determined by the origin of the solar wind streams (CMEs, CIRs or HCS). The ionospheric heights and foF2 variations at the equator during the northward of IMF Bz and the southward of IMF Bz (the main phase of the magnetic storm) are very distinguished. Distinctions between quiet and disturbance periods in the heights can reach up to100 km and more, dropping of the critical frequency foF2 can reach 2 MHz and depends on large scale solar wind structures as CMEs, CIRs or HCS.

Biktash, Lilia

379

Orientation of solar wind dynamic pressure phase fronts  

NASA Astrophysics Data System (ADS)

Orientation of structures in the solar wind plays an important role when attempting to use upstream observations at L1 for prediction of subsequent conditions near the Earth. In this study, the relationship between solar wind dynamic pressure forcing and geosynchronous magnetic field response is used to determine a very large set of lagged correlations between the ACE and GOES satellites. Effects due to tilted solar wind structures are explored using the dispersion of arrival times relative to a simple phase plane model. Assuming that structure phase-front normal vectors were located in the GSE-xy plane, we found a characteristic azimuth of 15°. Similar analysis carried out with velocity scaling according to the Parker spiral model did not produce an improved fit. Binning by average interplanetary magnetic field (IMF) B? orientation produced a clear pattern in characteristic azimuth, with phase-front normals perpendicular to both the predominant Parker spiral orientation and the less common ortho-spiral configuration. An empirical relationship ?n°=-45°sin(2?B) was found to predict phase-front normal azimuth over the entire range of observed IMF azimuths. The effects of lateral displacement from the Sun-Earth line in the GSE-z direction are comparable to those for GSE-y, indicating that solar wind structures are often significantly inclined with respect to the ecliptic plane.

Jackel, Brian J.; Cameron, Taylor; Weygand, James M.

2013-04-01

380

The source of electrostatic fluctuations in the solar-wind  

NASA Technical Reports Server (NTRS)

Solar wind electron and ion distribution functions measured simultaneously with or close to times of intense electrostatic fluctuations are subjected to a linear Vlasov stability analysis. Although all distributions tested were found to be stable, the analysis suggests that the ion beam instability is the most likely source of the fluctuations.

Lemons, D. S.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gary, S. P.; Gosling, J. T.

1979-01-01

381

Astronaut Edwin Aldrin deploying Solar Wind Composition experiment  

NASA Technical Reports Server (NTRS)

Astronaut Edwin E. Aldrin Jr., lunar module pilot, is photographed during the Apollo 11 extravehicular activity on the Moon. Astronaut Neil A. Armstrong, commander, took this picture with a 70mm lunar surface camera. Aldrin has just deployed the Solar Wind Composition experiment, a component of the Early Apollo Scientific Experiments Package (EASEP).

1969-01-01

382

Coronal Streamers in the Solar Wind at 1 AU  

Microsoft Academic Search

Examination of solar wind plasma data obtained by the Los Alamos experiments on Imp 6, 7, and 8 during the 1971 - 1978 interval has revealed a frequent association between minimums in helium abundance and maximums in proton density. These events occur at low flow speeds and are strongly correlated with polarity reversals in the interplanetary magnetic field. A large

J. T. Gosling; G. Borrini; J. R. Asbridge; S. J. Bame; W. C. Feldman; R. T. Hansen

1981-01-01

383

Depletion of solar wind plasma near a planetary boundary  

Microsoft Academic Search

A mathematical model is presented that describes the squeezing of solar wind plasma out along interplanetary magnetic field lines in the region between the bow shock and the effective planetary boundary (in the case of the earth, the magnetopause). In the absence of local magnetic merging the squeezing process should create a 'depletion layer,' a region of very low plasma

B. J. Zwan; R. A. Wolf

1976-01-01

384

Energy coupling function and solar wind-magnetosphere dynamo  

Microsoft Academic Search

The power delivered by the solar wind dynamo to the open magnetosphere is calculated based on the concept of field line reconnection, independent of the MHD steady reconnection theories. By recognizing a previously overlooked geometrical relationship between the reconnection electric field and the magnetic field, the calculated power is shown to be approximately proportional to the Akasofu-Perreault energy coupling function

J. R. Kan; L. C. Lee

1979-01-01

385

Energy coupling between the solar wind and the magnetosphere  

Microsoft Academic Search

This paper describes in detail how we are led to the first approximation expression for the solar wind-magnetosphere energy coupling function ?, which correlates well with the total energy consumption rate UTof the magnetosphere. It is shown that ? is the primary factor which controls the time development of magnetospheric substorms and storms. The finding of this particular expression ?

S.-I. Akasofu

1981-01-01

386

Shape of the Geomagnetic Field Solar Wind Boundary  

Microsoft Academic Search

The shape of the boundary of the geomagnetic field in a solar wind has been calculated by a self-consistent method in which, in first order, approximate magnetic fields are used to calculate a boundary surface. The electric currents in this boundary produce mag- netic fields, which can be calculated once the first surface is known. These are added to the

Gilbert D. Mead; David B. Beard

1964-01-01

387

The Solar Wind in the Outer Heliosphere and Heliosheath  

NASA Technical Reports Server (NTRS)

The solar wind environment has a large influence on the transport of cosmic rays. This chapter discusses the observations of the solar wind plasma and magnetic field in the outer heliosphere and the heliosheath. In the supersonic solar wind, interaction regions with large magnetic fields form barriers to cosmic ray transport. This effect, the "CR-B" relationship, has been quantified and is shown to be valid everywhere inside the termination shock (TS). In the heliosheath, this relationship breaks down, perhaps because of a change in the nature of the turbulence. Turbulence is compressive in the heliosheath, whereas it was non-compressive in the solar wind. The plasma pressure in the outer heliosphere is dominated by the pickup ions which gain most of the flow energy at the TS. The heliosheath plasma and magnetic field are highly variable on scales as small as ten minutes. The plasma flow turns away from the nose roughly as predicted, but the radial speeds at Voyager 1 are much less than those at Voyager 2, which is not understood. Despite predictions to the contrary, magnetic reconnection is not an important process in the inner heliosheath with only one observed occurrence to date.

Richardson, J. D.; Burlaga, L. F.

2011-01-01

388

Hydro, Solar, Wind The Future of Renewable Energy  

E-print Network

Hydro, Solar, Wind The Future of Renewable Energy Joseph Flocco David Lath Department of Electrical. Hydropower Water has grown in previous years to become the most widely used form of renewable energy across years to come from Hydropower. It is considered to be a renewable energy source because it uses

Lavaei, Javad

389

Pioneer 10 observations of the solar wind interaction with Jupiter  

Microsoft Academic Search

Detailed analysis of the Pioneer 10 plasma analyzer experiment flight data during the Jupiter flyby in late November and early December 1973 has been performed. The observations show that the interaction of Jupiter's magnetic field with the solar wind is similar in many ways to that at earth, but the scale size is over 100 times larger. Jupiter is found

J. H. Wolfe; J. D. Mihalov; H. R. Collard; D. D. McKibbin; L. A. Frank; D. S. Intriligator

1974-01-01

390

Livestock water pumping with wind and solar power  

Technology Transfer Automated Retrieval System (TEKTRAN)

Recent developments in pumping technologies have allowed for efficient use of renewable energies like wind and solar to power new pumps for remote water pumping. A helical type, positive displacement pump was developed a few years ago and recently modified to accept input from a variable power sourc...

391

Saturn's Variable Radio Period: Modulation by the Solar Wind  

E-print Network

Saturn's Variable Radio Period: Modulation by the Solar Wind P. Zarka, L. Lamy, B. Cecconi, R and Zarka, 2005] 12h 6h 6h 18h 18h [Galopeau et al., 1995] #12;· « super-clean » SKR data 2003/181 2006 by VSW (+ SKR visibility related to Cassini's orbit) Supports [Cecconi and Zarka, 2005] model [paper

Demoulin, Pascal

392

Latitudinal Variations in the Solar Wind Electron Heat Flux  

Microsoft Academic Search

Ulysses measurements of the solar wind electron heat flux as a function of heliographic latitude are presented. The latitudinal in the electron heat flux presented have been normalized by the radial gradient in the electron heat flux obtained during the in-ecliptic phase of the Ulysses mission (qe˜ R-3.0). We find no significant variation in electron heat flux with latitude.

Earl E. Scime; Samuel J. Bame; John L. Phillips; Andre Balogh

1995-01-01

393

Latitudinal variations in the solar wind electron heat flux  

Microsoft Academic Search

Ulysses measurements of the solar wind electron heat flux as a function of heliographic latitude are presented. The latitudinal in the electron heat flux presented have been normalized by the radial gradient in the electron heat flux obtained during the in-ecliptic phase of the Ulysses mission (qe~ R-3.0). We find no significant variation in electron heat flux with latitude.

Earl E. Scime; Samuel J. Bame; John L. Phillips; Andre Balogh

1995-01-01

394

Polar and high latitude substorms and solar wind conditions  

NASA Astrophysics Data System (ADS)

All substorm disturbances observed in polar latitudes can be divided into two types: polar, which are observable at geomagnetic latitudes higher than 70° in the absence of substorms below 70°, and high latitude substorms, which travel from auroral (<70°) to polar (>70°) geomagnetic latitudes. The aim of this study is to compare conditions in the IMF and solar wind, under which these two types of substorms are observable on the basis of data from meridional chain of magnetometers IMAGE and OMNI database for 1995, 2000, and 2006-2011. In total, 105 polar and 55 high latitude substorms were studied. It is shown that polar substorms are observable at a low velocity of solar wind after propagation of a high-speed recurrent stream during the late recovery phase of a magnetic storm. High latitude substorms, in contrast, are observable with a high velocity of solar wind, increased values of the Bz component of the IMF, the Ey component of the electric field, and solar wind temperature and pressure, when a high-speed recurrent stream passes by the Earth.

Despirak, I. V.; Lyubchich, A. A.; Kleimenova, N. G.

2014-09-01

395

Effect of the Sun's Rotation on the Solar Wind  

Microsoft Academic Search

The effect of the sun's rotation on the solar wind has been treated recently by Modisette (1967), Weber and Davis (1967), and Alfonso- Faus (1967), with similar results in their major features. The angular momentum equation is used, and the boundary value of the azimuthal component of the magnetic field is determined from the requirement that the solution must be

Antonio Alfonso-Faus

1967-01-01

396

Solar Wind Monitoring with SWIM-SARA Onboard Chandrayaan-1  

NASA Astrophysics Data System (ADS)

The SARA experiment aboard the Indian lunar mission Chandrayaan-1 consists of two instruments: Chandrayaan-1 Energetic Neutral Analyzer (CENA) and the SolarWind Monitor (SWIM). CENA will provide measurements of low energy neutral atoms sputtered from lunar surface in the 0.01-3.3 keV energy range by the impact of solar wind ions. SWIM will monitor the solar wind flux precipitating onto the lunar surface and in the vicinity of moon. SWIM is basically an ion-mass analyzer providing energy-per-charge and number density of solar wind ions in the energy range 0.01-15 keV. It has sufficient mass resolution to resolve H+ , He++, He+, O++, O+, and >20 amu, with energy resolution 7% and angular resolution 4:5° × 22:5. The viewing angle of the instrument is 9° × 180°.Mechanically, SWIM consists of a sensor and an electronic board that includes high voltage supply and sensor electronics. The sensor part consists of an electrostatic deflector to analyze the arrival angle of the ions, cylindrical electrostatic analyzer for energy analysis, and the time-of-flight system for particle velocity determination. The total size of SWIM is slightly larger than a credit card and has a mass of 500 g.

Bhardwaj, A.; Barabash, S.; Sridharan, R.; Wieser, M.; Dhanya, M. B.; Futaana, Y.; Asamura, K.; Kazama, Y.; McCann, D.; Varier, S.; Vijayakumar, E.; Mohankumar, S. V.; Raghavendra, K. V.; Kurian, T.; Thampi, R. S.; Andersson, H.; Svensson, J.; Karlsson, S.; Fischer, J.; Holmstrom, M.; Wurz, P.; Lundin, R.

397

Solar Wind Magnetic Field Bending of Jovian Dust Trajectories  

Microsoft Academic Search

From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain

H. A. Zook; E. Grun; M. Baguhl; D. P. Hamilton; G. Linkert; J.-C. Liou; R. Forsyth; J. L. Phillips

1996-01-01

398

Iron charge states observed in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-3 are reported. The low energy section of approx the ULECA sensor selects particles by their energy per charge (over the range 3.6 keV/Q to 30 keV/Q) and simultaneously measures their total energy with two low-noise solid state detectors. Solar wind Fe charge state measurements from three time periods of high speed solar wind occurring during a post-shock flow and a coronal hole-associated high speed stream are presented. Analysis of the post-shock flow solar wind indicates the charge state distributions for Fe were peaked at approx +16, indicative of an unusually high coronal temperature (3,000,000 K). In contrast, the Fe charge state distribution observed in a coronal hole-associated high speed stream peaks at approx -9, indicating a much lower coronal temperature (1,400,000 K). This constitutes the first reported measurements of iron charge states in a coronal hole-associated high speed stream.

Ipavich, F. M.; Galvin, A. B.; Gloeckler, G.; Hovestadt, D.; Klecker, B.; Scholer, M.

1983-01-01

399

The solar wind interaction with the geomagnetic field  

Microsoft Academic Search

A review is presented of the interaction of the solar wind with the magnetic field of the earth. The material is developed primarily from an observational point of view. The early observations are covered through late 1963, with primary emphasis on the sunward interaction region. The historical review of the early results is discussed in terms of the significant contributions

John H. Wolfe; Devrie S. Intriligator

1970-01-01

400

Probabilistic modelling of hybrid solar\\/wind power system with solar tracking system  

Microsoft Academic Search

This paper presents a probabilistic model applied to a hybrid solar-wind power system (HSWPS), which is equipped with either a one-axis or a two-axis solar tracking system.Within the framework of a case study, the potential of the developed probabilistic approach is presented, and the effect of the solar tracking systems on the annual energy gain is discussed.Specifically, the impact of

Giuseppe Marco Tina; Salvina Gagliano

2011-01-01

401

THREE-DIMENSIONAL EVOLUTION OF SOLAR WIND DURING SOLAR CYCLES 22-24  

SciTech Connect

This paper presents an analysis of three-dimensional evolution of solar wind density turbulence and speed at various levels of solar activity between solar cycles 22 and 24. The solar wind data used in this study have been obtained from the interplanetary scintillation (IPS) measurements made at the Ooty Radio Telescope, operating at 327 MHz. Results show that (1) on average, there was a downward trend in density turbulence from the maximum of cycle 22 to the deep minimum phase of cycle 23; (2) the scattering diameter of the corona around the Sun shrunk steadily toward the Sun, starting from 2003 to the smallest size at the deepest minimum, and it corresponded to a reduction of {approx}50% in the density turbulence between the maximum and minimum phases of cycle 23; (3) the latitudinal distribution of the solar wind speed was significantly different between the minima of cycles 22 and 23. At the minimum phase of solar cycle 22, when the underlying solar magnetic field was simple and nearly dipole in nature, the high-speed streams were observed from the poles to {approx}30 Degree-Sign latitudes in both hemispheres. In contrast, in the long-decay phase of cycle 23, the sources of the high-speed wind at both poles, in accordance with the weak polar fields, occupied narrow latitude belts from poles to {approx}60 Degree-Sign latitudes. Moreover, in agreement with the large amplitude of the heliospheric current sheet, the low-speed wind prevailed in the low- and mid-latitude regions of the heliosphere. (4) At the transition phase between cycles 23 and 24, the high levels of density and density turbulence were observed close to the heliospheric equator and the low-speed solar wind extended from the equatorial-to-mid-latitude regions. The above results in comparison with Ulysses and other in situ measurements suggest that the source of the solar wind has changed globally, with the important implication that the supply of mass and energy from the Sun to the interplanetary space has been significantly reduced in the prolonged period of low solar activity. The IPS results are consistent with the onset and growth of the current solar cycle 24, starting from the middle of 2009. However, the width of the high-speed wind at the northern high latitudes has almost disappeared and indicates that the ascending phase of the current cycle has almost reached the maximum phase in the northern hemisphere of the Sun. However, in the southern part of the hemisphere, the solar activity has yet to develop and/or increase.

Manoharan, P. K., E-mail: mano@ncra.tifr.res.in [Radio Astronomy Centre, National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Udhagamandalam (Ooty) 643001 (India)

2012-06-01

402

Signature of open magnetic field lines in the extended solar corona and of solar wind acceleration  

NASA Technical Reports Server (NTRS)

The observations carried out with the ultraviolet coronagraph spectrometer onboard the Solar and Heliospheric Observatory (SOHO) are discussed. The purpose of the observations was to determine the line of sight and radial velocity fields in coronal regions with different magnetic topology. The results showed that the regions where the high speed solar wind flows along open field lines are characterized by O VI 1032 and HI Lyman alpha 1216 lines. The global coronal maps of the line of sight velocity were reconstructed. The corona height, where the solar wind reaches 100 km/s, was determined.

Antonucci, E.; Giordano, S.; Benna, C.; Kohl, J. L.; Noci, G.; Michels, J.; Fineschi, S.

1997-01-01

403

Solar wind induced magnetic field around the unmagnetized Earth  

E-print Network

The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth's surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These polarity reversals correspond to drastic breakdowns of the dynamo action. The question arises what the consequences for the Earth's atmosphere, climate, and, in particular, biosphere are. It is shown by kinematic estimates and three-dimensional plasma-neutral gas simulations that the solar wind can induce very fast a magnetic field in the previously completely unmagnetized Earth's ionosphere that is strong enough to protect Earth from cosmic radiations comparable to the case of an intact magnetic dynamo.

G. T. Birk; H. Lesch; C. Konz

2004-04-29

404

Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24  

PubMed Central

The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is ‘typical’ solar wind, even when the Sun is relatively inactive.

Luhmann, Janet G.; Petrie, Gordon; Riley, Pete

2012-01-01

405

HEMISPHERIC ASYMMETRIES IN THE POLAR SOLAR WIND OBSERVED BY ULYSSES NEAR THE MINIMA OF SOLAR CYCLES 22 AND 23  

SciTech Connect

We examined solar wind plasma and interplanetary magnetic field (IMF) observations from Ulysses' first and third orbits to study hemispheric differences in the properties of the solar wind and IMF originating from the Sun's large polar coronal holes (PCHs) during the declining and minimum phase of solar cycles 22 and 23. We identified hemispheric asymmetries in several parameters, most notably {approx}15%-30% south-to-north differences in averages for the solar wind density, mass flux, dynamic pressure, and energy flux and the radial and total IMF magnitudes. These differences were driven by relatively larger, more variable solar wind density and radial IMF between {approx}36 Degree-Sign S-60 Degree-Sign S during the declining phase of solar cycles 22 and 23. These observations indicate either a hemispheric asymmetry in the PCH output during the declining and minimum phase of solar cycles 22 and 23 with the southern hemisphere being more active than its northern counterpart, or a solar cycle effect where the PCH output in both hemispheres is enhanced during periods of higher solar activity. We also report a strong linear correlation between these solar wind and IMF parameters, including the periods of enhanced PCH output, that highlight the connection between the solar wind mass and energy output and the Sun's magnetic field. That these enhancements were not matched by similar sized variations in solar wind speed points to the mass and energy responsible for these increases being added to the solar wind while its flow was subsonic.

Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; McComas, D. J. [Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 (United States); Pogorelov, N. V. [Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2013-05-10

406

A Comparison of Magnetic Correlation Functions in the Solar Wind  

NASA Astrophysics Data System (ADS)

Magnetic field data from 11 different solar wind spacecraft from many different intervals are employed to estimate spatial and time correlations in the interplanetary magnetic field. Different approaches are employed to find the autocorrelation, cross correlation, and Eulerian correlation functions versus spatial or time separation for turbulent intervals in both the slow and fast solar wind. The cross correlation function is determined by correlating time series data from multiple spacecraft separated in space and relies on many intervals with different spacecraft spatial separations. This is a pure two-point measurement, The autocorrelation function is determined by correlating turbulent magnetic field fluctuations time series data from a single spacecraft with itself "lagged" or separated in time . This relies on frozen in flow approximation to convert to a spatial separation. One method uses the spacecraft separation vector and the flow vector as opposed to simply the separation along X GSE and the solar wind speed. The other method finds the time lag between the spacecraft pairs from a maximum cross correlation value of the turbulent magnetic field intervals. The Eulerian correlation function, purely temporal in the plasma frame, is determined in the spacecraft frame by correlating time series data from multiple spacecraft separated in time and space. This relies on both the frozen in flow approximation and the use of many intervals. For this study we interpret the exponential decay constants from the exponential fit to the Eulerian correlation function as characteristic decorrelation time of the turbulent plasma. Preliminary results demonstrate that the Eulerian decorrelation time is significantly longer in the slow solar wind (<450 km/s) than the fast solar wind (>600 km/s). Our results are compared with the Eulerian decorrelation times in Matthaeus et al. [2010], Weygand et al [2012],Zhou et al. [2004], and Servidio et al. [2011].

Weygand, J. M.; Matthaeus, W. H.; Kivelson, M. G.; Dasso, S.

2012-12-01

407

Solar Wind Turbulence: Perpendicular and Parallel Spectral Transfer  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) turbulence provides a useful framework for understanding the nature and behavior of solar wind fluctuations1. We present a review of MHD turbulence in the solar wind context, where typically ? B / B0 ˜ 1, rather than ? 1. Here B0 denotes the mean or large-scale magnetic field and ? B the rms fluctuation amplitude. We will discuss various consequences of the the well-known anisotropy induced by B0 . For example, the energy transfer is no longer isotropic, with transfer in directions approximately perpendicular to B0 remaining strong whereas parallel transfer is suppressed. Thus, differences in the slope of the energy spectrum in the perpendicular and parallel directions are to be expected. This in turn has implications for scattering of energetic particles. Another consequence of the suppression of parallel transfer is that it restricts the energy available to any kinetic processes which act at large parallel wavenumbers, e.g., ion-cyclotron damping. Since such kinetic processes are likely to be involved in the heating of solar wind fluctuations, the anisotropy of spectral transfer influences heating processes. On the modeling front, anisotropy of spectral transfer helps motivate treating the fluctuations as belonging to two distinct groups, conveniently referred to as the quasi-two-dimensional and the wave-like components. The partitioning is based on the ratio of the nonlinear timescale ? NL(k) to the Alfvén timescale ? A( k) at each wavevector k (see figure). The self interaction of the quasi-2D component is predominantly nonlinear with wave effects being relatively weak. For the wave-like component, the situation is, roughly speaking, reversed. Our presentation will review these concepts and the associated physics. The relevance of the equations of Reduced MHD---originally developed for ? B / B0 ? 1---to solar wind plasma is also discussed. 1 Bruno, R. and Carbone, V., The Solar Wind as a Turbulence Laboratory, Liv. Rev. Sol. Phys., 2 (2005)

Oughton, S.

2011-12-01

408

Four solar cycle ecliptic solar wind data set generated from the OMNI data set  

NASA Astrophysics Data System (ADS)

Numerical modeling of the global heliosphere provides key insights into the physics of the outer heliosphere. The solar wind data utilized by these models impacts their accuracy and should be as close as possible to the actual solar wind. Ideally, the solar wind data would come directly from in situ measurements. Unfortunately the availability of such measurements is severely limited, mostly to points near Earth. A method to infer the solar wind at points not directly observed is developed such that a data set with four solar cycles of solar wind data which fills the ecliptic plane is generated, using the hourly OMNI data set as the seed data. First the OMNI data are separated into four separate categories: fast, slow, CIR and ICME. The categories are characterized by relative coverage, durations, variable distributions, running averages, and step-size distributions. The category statistics allow for inferences as to which category is present during periods and for locations for which no solar wind data are available, generating a continuous 2D category map of the solar wind for the full four solar cycles covered by OMNI. The category maps are used to determine solar wind plasma and interplanetary magnetic field (IMF) characteristics. The plasma and IMF values are determined by local running averages coupled with a random walk technique. The averages provide baseline values and the random walk adds short-duration deviations from this baseline. The resulting four solar cycle 2D data set is analyzed along various heliolongitudes at 1 AU. The statistics from the data along these trajectories are compared to the statistics of the original OMNI data set. The category durations and relative coverage are similar to those of the OMNI data, though with some discrepancies. The plasma and IMF variable distributions are also very similar to those of the OMNI data, again with some discrepancies. Additional generated data sets using different sets of plasma and IMF variables could possibly improve the agreement with OMNI, and the data set remains to be deployed in simulations.

Thatcher, Lucas J.

409

Testing for Asymmetric Scaling of Intermittent Solar Wind Turbulence  

NASA Astrophysics Data System (ADS)

We look at scaling properties of intermittent turbulence in the solar wind. We analyze time series of velocities of the low and fast speed streams measured in situ by Helios spacecraft during solar minimum at distances of 0.3 and 1 AU from the Sun and Advanced Composition Explorer during solar minimum and maximum at 1 AU. To quantify asymmetric scaling of solar wind turbulence, we consider a generalized two-scale weighted Cantor set describing nonuniform intermittent distribution of the kinetic energy flux between cascading eddies of various sizes [1]. We investigate the resulting spectrum of generalized dimensions and the corresponding multifractal singularity spectrum depending on two scaling parameters and one probability measure parameter, demonstrating that intermittent pulses are stronger for the asymmetric multifractal scaling. In particular, the fast streams at 1 AU seem to be more multifractal than the slow streams because the generalized dimensions and multifractal singularity spectra vary more with the index. It is worth noting that for the model with two different scaling parameters a much better agreement with the solar wind data is obtained, especially for the negative index of the generalized dimensions. Therefore we argue that there is a need to use a two-scale cascade model. Hence we propose this new more general model as a useful tool for analysis of intermittent turbulence in space plasmas [1]. [1] Macek, W. M. and A. Szczepaniak (2008), Generalized two-scale weighted Cantor set model for solar wind turbulence, Geophys. Res. Lett., 35, L02108, doi: 10.1029/2007GL032263.

Macek, W. M.; Szczepaniak, A.

2008-05-01

410

Solar Panel Buffeted by Wind at Phoenix Site  

NASA Technical Reports Server (NTRS)

Winds were strong enough to cause about a half a centimeter (.19 inch) of motion of a solar panel on NASA's Phoenix Mars lander when the lander's Surface Stereo Imager took this picture on Aug. 31, 2008, during the 96th Martian day since landing.

The lander's telltale wind gauge has been indicating wind speeds of about 4 meters per second (9 miles per hour) during late mornings at the site.

These conditions were anticipated and the wind is not expected to do any harm to the lander.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

411

A porcupine Sun? Implications for the solar wind and Earth  

NASA Astrophysics Data System (ADS)

The recent minimum was unusually long, and it was not just the case of the ``usual story'' slowed down. The coronal magnetic field never became completely dipolar as in recent Space Age minima, but rather gradually evolved into an (essentially axisymmetric) global configuration possessing mixed open and closed magnetic structures at many latitudes. In the process, the impact of the solar wind at the Earth went from resembling that from a sequence of rotating ``fire-hoses'' to what might be expected from a weak, omnidirectional ``lawn-sprinkler''. The previous (1996) solar minimum was a more classic dipolar configuration, and was characterized by slow wind of hot origin localized to the heliospheric current sheet, and fast wind of cold origin emitted from polar holes, but filling most of the heliosphere. In contrast, the more recent minimum solar wind possessed a broad range of speeds and source temperatures (although cooler overall than the prior minimum). We discuss possible connections between these observations and the near-radial expansion and small spatial scales characteristic of the recent minimum's porcupine-like magnetic field.

Gibson, Sarah E.; Zhao, Liang

2012-07-01

412

Neutral Solar Wind Generated by Lunar Exospheric Dust at the Terminator  

NASA Technical Reports Server (NTRS)

We calculate the flux of neutral solar wind observed on the lunar surface at the terminator due to solar wind protons penetrating exospheric dust with: (1) grains larger that 0.1 microns and (2) grains larger than 0.01 microns. For grains larger than 0.1 microns, the ratio of the neutral solar wind to solar wind flux is estimated to be approx.10(exp -4)-10(exp -3) at solar wind speeds in excess of 800 km/s, but much lower (less than 10(exp -5) at average to low solar wind speeds. However, when the smaller grain sizes are considered, the ratio of the neutral solar wind flux to solar wind flux is estimated to be greater than or equal to 10(exp -5) at all speeds and at speeds in excess of 700 km/s reaches 10(exp -3)-10(exp -2). These neutral solar wind fluxes are easily measurable with current low energy neutral atom instrumentation. Observations of neutral solar wind from the surface of the Moon could provide a very sensitive determination of the distribution of very small dust grains in the lunar exosphere and would provide data complementary to optical measurements at ultraviolet and visible wavelengths. Furthermore, neutral solar wind, unlike its ionized counterpart, is .not held-off by magnetic anomalies, and may contribute to greater space weathering than expected in certain lunar locations.

Collier, Michael R.; Stubbs, Timothy J.

2007-01-01

413

Some remarks on waves in the solar wind  

SciTech Connect

Waves are significant to the solar wind in two ways--as modifiers of the particle distribution functions, and as diagnostics. In addition, the solar wind serves as an important laboratory for the study of plasma wave processes, as it is possible to make detailed measurements of phenomena which are too small to be easily measured by laboratory sized sensors. The waves, both electromagnetic and electrostatic, which are part of the solar type III burst phenomenon, have been extensively studied as examples of nonlinear plasma phenomena, and also used as remote sensors to trace the solar magnetic field. The observations made by Ulysses show that the field can be traced in this way out to perhaps a little more than an A.U., but then the electromagnetic part of the type III burst fades out. Nevertheless, sometimes Langmuir waves appear at Ulysses at an appropriate extrapolated time. This seems to support the picture in which the electromagnetic waves at the fundamental plasma frequency are trapped in density fluctuations. Recently it has been found that Langmuir waves are associated with magnetic holes. This may help to elucidate the nature of magnetic holes. Nonlinear processes are important in the transformation of wave energy to particle energy. Some recent examples from Wind data are shown.

Kellogg, P. J.; Goetz, K.; Monson, S. J.; Balogh, A.; Forsyth, R. J. [School of Physics and Astronomy, University of Minnesota, Minneapolis (United States); The Blackett Laboratory, Imperial College of Science and Technology, London (United Kingdom)

1996-07-20

414

Small solar wind transients: Stereo-A observations in 2009  

SciTech Connect

Year 2009 was the last year of a long and pronounced solar activity minimum. In this year the solar wind in the inner heliosphere was for 90% of the time slow (< 450 km s{sup -1}) and with a weaker magnetic field strength compared to the previous solar minimum 1995-1996. We choose this year to present the results of a systematic search for small solar wind transients (STs) observed by the STEREO-Ahead (ST-A) probe. The data are from the PLASTIC and IMPACT instrument suites. By 'small' we mean a duration from {approx}1 to 12 hours. The parameters we search for to identify STs are (i) the total field strength, (ii) the rotation of the magnetic field vector, (iii) its smoothness, (iv) proton temperature, (v) proton beta, and (vi) Alfven Mach number. We find 45 examples. The STs have an average duration of {approx}4 hours. Ensemble averages of key quantities are: (i) maximum B = 7.01 nT; (ii) proton {beta}= 0.18; (iii) proton thermal speed = 20.8 km s{sup -1}; and (iv) Alfven Mach number = 6.13. No distinctive feature is found in the pitch angle distributions of suprathermal electrons. Our statistical results are compared with those of STs observed near Earth by Wind during 2009.

Yu, W.; Farrugia, C. J.; Galvin, A. B.; Simunac, K. D. C.; Popecki, M. A.; Lugaz, N. [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Kilpua, E. K. J. [Dept. of Physics, Division of Geophysics and Astronomy, University of Helsinki (Finland); Moestl, C. [Institute of Physics, University of Graz, 8010 Graz, Austria and Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Luhmann, J. G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Opitz, A.; Sauvaud, J.-A. [Institut de Recherche en Astrophysique et Planetologie (CNRS-UPS), Universite de Toulouse, F-31038, Toulouse (France)

2013-06-13

415

The Spectroscopic Footprint of the Fast Solar Wind  

E-print Network

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the photosphere, inner heliosphere and the mapping of the solar wind source region. We focus the bulk of our analysis on interpreting the thermal and spatial dependence of the non-thermal line widths in the ECH as measured by SOHO/SUMER by placing the measurements in context with recent studies of ubiquitous Alfven waves in the solar atmosphere and line profile asymmetries (indicative of episodic heating and mass loading of the coronal plasma) that originate in the strong, unipolar magnetic flux concentrations that comprise the supergranular network. The results presented in this paper are consistent with a picture where a significant portion of the energy responsible for t...

McIntosh, Scott W; De Pontieu, Bart

2010-01-01

416

Solar wind heavy ions from flare-heated coronal plasma  

NASA Technical Reports Server (NTRS)

Information concerning the coronal expansion is carried by solar-wind heavy ions. Distinctly different energy-per-charge ion spectra are found in two classes of solar wind having the low kinetic temperatures necessary for E/q resolution of the ion species. Heavy-ion spectra which can be resolved are most frequently observed in the low-speed interstream (IS) plasma found between high speed streams; the streams are thought to originate from coronal holes. Although the sources of the IS plasma are uncertain, the heavy-ion spectra found there contain identifiable peaks of O, Si, and Fe ions. Such spectra indicate that the IS ionization state of O is established in coronal gas at a temperature of approximately 1.6 million K, while that of Fe is frozen in farther out at about 1.5 million K. On occasion anomalous spectra are found outside IS flows in solar wind with abnormally depressed local kinetic temperatures. The anomalous spectra contain Fe(16+) ions, not usually found in IS flows, and the derived coronal freezing-in temperatures are significantly higher. The coronal sources of some of these ionizationally hot flows are identified as solar flares.

Bame, S. J.; Asbridge, J. R.; Feldman, W. C.; Fenimore, E. E.; Gosling, J. T.

1979-01-01

417

Solar cycle evolution of dipolar and pseudostreamer belts and their relation to the slow solar wind  

NASA Astrophysics Data System (ADS)

Dipolar streamers are coronal structures formed by open solar flux converging from coronal holes of opposite polarity. Thus, the dipolar streamer belt traces the coronal foot point of the heliospheric current sheet, and it is strongly associated with the origin of slow solar wind. Pseudostreamers, on the other hand, separate converging regions of open solar flux from coronal holes of the same polarity and do not contain current sheets. They have recently received a great deal of interest as a possible additional source of slow solar wind. Here we add to that growing body of work by using the potential-field source-surface model to determine the occurrence and location of dipolar and pseudostreamers over the last three solar cycles. In addition to providing new information about pseudostreamer morphology, the results help explain why the observations taken during the first Ulysses perihelion pass in 1995 showed noncoincidence between dipolar streamer belt and the locus of slowest flow. We find that Carrington rotation averages of the heliographic latitudes of dipolar and pseudostreamer belts are systematically shifted away from the equator, alternately in opposite directions, with a weak solar cycle periodicity, thus keeping slow wind from the web of combined streamer belts approximately symmetric about the equator. The largest separation of dipolar and pseudostreamer belts occurred close to the Ulysses pass, allowing a unique opportunity to see that slow wind from pseudostreamer belts north of the southward displaced dipolar belt was responsible for the noncoincident pattern.

Owens, M. J.; Crooker, N. U.; Lockwood, M.

2014-01-01

418

Western Wind and Solar Integration Study: Hydropower Analysis  

SciTech Connect

The U.S. Department of Energy's (DOE) study of 20% Wind Energy by 2030 was conducted to consider the benefits, challenges, and costs associated with sourcing 20% of U.S. energy consumption from wind power by 2030. This study found that with proactive measures, no insurmountable barriers were identified to meet the 20% goal. Following this study, DOE and the National Renewable Energy Laboratory (NREL) conducted two more studies: the Eastern Wind Integration and Transmission Study (EWITS) covering the eastern portion of the U.S., and the Western Wind and Solar Integration Study (WWSIS) covering the western portion of the United States. The WWSIS was conducted by NREL and research partner General Electric (GE) in order to provide insight into the costs, technical or physical barriers, and operational impacts caused by the variability and uncertainty of wind, photovoltaic, and concentrated solar power when employed to serve up to 35% of the load energy in the WestConnect region (Arizona, Colorado, Nevada, New Mexico, and Wyoming). WestConnect is composed of several utility companies working collaboratively to assess stakeholder and market needs to and develop cost-effective improvements to the western wholesale electricity market. Participants include the Arizona Public Service, El Paso Electric Company, NV Energy, Public Service of New Mexico, Salt River Project, Tri-State Generation and Transmission Cooperative, Tucson Electric Power, Xcel Energy and the Western Area Power Administration.

Acker, T.; Pete, C.

2012-03-01

419

A Model for the Sources of the Slow Solar Wind  

NASA Technical Reports Server (NTRS)

Models for the origin of the slow solar wind must account for two seemingly contradictory observations: The slow wind has the composition of the closed-field corona, implying that it originates from the continuous opening and closing of flux at the boundary between open and closed field. On the other hand, the slow wind has large angular width, up to approximately 60 degrees, suggesting that its source extends far from the open-closed boundary. We propose a model that can explain both observations. The key idea is that the source of the slow wind at the Sun is a network of narrow (possibly singular) open-field corridors that map to a web of separatrices and quasi-separatrix layers in the heliosphere. We compute analytically the topology of an open-field corridor and show that it produces a quasi-separatrix layer in the heliosphere that extends to angles far front the heliospheric current sheet. We then use an MHD code and MIDI/SOHO observations of the photospheric magnetic field to calculate numerically, with high spatial resolution, the quasi-steady solar wind and magnetic field for a time period preceding the August 1, 2008 total solar eclipse. Our numerical results imply that, at least for this time period, a web of separatrices (which we term an S-web) forms with sufficient density and extent in the heliosphere to account for the observed properties of the slow wind. We discuss the implications of our S-web model for the structure and dynamics of the corona and heliosphere, and propose further tests of the model.

Antiochos, Spiro K.; Mikic, Z.; Titov, V. S.; Lionello, R.; Linker, J. A.

2010-01-01

420

Twisted magnetic flux tubes in the solar wind  

NASA Astrophysics Data System (ADS)

Magnetic flux tubes in the solar wind can be twisted as they are transported from the solar surface, where the tubes are twisted owing to photospheric motions. The twisted magnetic tubes can be detected as the variation of total (thermal+magnetic) pressure during their passage through observing satellite. The twist of isolated magnetic tube may explain the observed abrupt changes of magnetic field direction at tube walls. For the tubes aligned with the Parker spiral, the twist angle can be estimated from the change of magnetic field direction. The twisted tubes are unstable to kink instability when the twist exceeds a critical value. It is shown that the critical twist angle of the tube with a homogeneous twist is 70 degree, but the angle can be decreased owing to the motion of the tube with regards to the solar wind stream. Tangential velocity discontinuity near the boundaries of individual tubes may also result in the Kelvin-Helmholtz instability. It is shown that the axial magnetic field stabilizes the instability in the case of sub-Alfvenic speeds. But even small twist in the external magnetic field allows the Kelvin-Helmholtz instability to be developed for any speed. Therefore, twisted magnetic flux tubes can be unstable to Kelvin-Helmholtz instability when they move with small speed relative to main solar wind stream. The Kelvin-Helmholtz vortices may significantly contribute into the solar wind turbulence. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement N 313038/STORM and from the Austrian 'Fonds zur Förderung der wissenschaftlichen Forschung' under project P24740-N27.

Zaqarashvili, Teimuraz; Voros, Zoltan; Zhelyazkov, Ivan; Narita, Yasuhito; Bruno, Roberto

2014-05-01

421

Observations of the solar wind speed near the sun  

NASA Astrophysics Data System (ADS)

Two-antenna scintillation (IPS) observations can provide accurate measurements of the velocity with which electron density fluctuations drift past the line of sight. These fluctuations can be used as tracers for the solar plasma and allow us to estimate the solar wind velocity near the Sun where spacecraft have not yet penetrated. We present recent IPS measurements made with the EISCAT and VLBA arrays. We have found that by using baselines which are several times the scale size of the diffraction pattern we are able to partially deconvolve the line of sight integration which affects remote sensing data. The long baselines allow the fast and slow components of the solar wind to be separated and their velocities estimated individually. In modeling IPS it is important that the scattering be ``weak'' because the model then requires only 1 spatial parameter instead of 3. EISCAT can only operate near 933MHz which limits the observation to outside of 18Rsolar, however the VLBA has higher frequency receivers which allow it to observe inside of 15Rsolar. The density variance ?Ne2 in the fast wind is a factor of 10-15 less than in the slow (Coles et al., 1995) making it necessary to consider the entire line of sight, particularly when the fast wind occupies the center portion. Using the point of closest approach and the average velocity to characterize the observation can lead to an incorrect interpretation of the data. We have compared our IPS observations with maps made from the Yohkoh soft X ray, HAO's white-light electron density, and Stanford magnetic field measurements as well as with the IMP8 and Ulysses spacecraft data to assist in placing the fast and slow wind. Here we have selected those observation from 1994 which were dominated by the southern coronal hole and have estimated a velocity acceleration profile for the fast solar wind between 7 and 100Rsolar which is presented in Figure 1. The observations suggest that the fast solar wind is fully developed by ~7Rsolar and shows no acceleration over the distance range probed. It is also inconsistent with wave driven acceleration models which continue to show significant acceleration out past 20Rsolar. This talk has been submitted to Nature (Grall et al., 1995).

Grall, R. R.; Coles, Wm. A.; Klinglesmith, M. T.

1996-07-01

422

Statistical study of magnetic reconnection observed by WIND in the solar wind  

NASA Astrophysics Data System (ADS)

Magnetic reconnection is a process where the energy stored in the magnetic field dissipates into plasma heating and acceleration. In spacecraft observations, we can identify magnetic reconnection through its exhaust where the plasma on reconnected field lines leaves the reconnection site. We present a statistical study of magnetic reconnection exhausts in the solar wind. The dataset is based on the WIND observations during the period of 1995-2012. We track the reconnection exhaust signatures like correlated and anticorrelated changes of the magnetic field and solar wind velocity and enhancements of the plasma temperature and density. In this study, we present the dependences of magnetic field and plasma parameters within the reconnection exhaust on the shear angle and on the exhaust thickness.

Enzl, Jakub; Nemecek, Zdenek; Safrankova, Jana; Prech, Lubomir

423

Solar Wind Fluctuations and Their Consequences on the Magnetosphere  

NASA Technical Reports Server (NTRS)

Efforts have been made to extract the physical meaning of each term in our prediction model of the Dst index using the solar wind as the only input. The work has been published Journal of Geophysical Research (Temerin and Li, 21002). We found different terms in the model representing different current in the magnetospheric system and each current has different rise and decay times, with the symmetric ring current the slowest, then the partial ring current, then the tail current. We also have been trying to understand the physical meaning of the diffusion coefficient used in our prediction model of relativistic electron fluxes at geostationary orbit. The model reproduced the observations of MeV electron flux variations well, the diffusion coefficient had be assumed only die to local magnetic field fluctuations, leading to its 10th power dependence on the L. We have studied the theoretical derivation of the diffusion coefficient and we believe that the effect electric field fluctuations at smaller L could become more significant. We have expanded our previous radiation belt electron prediction model, which predicted MeV electron geosynchronous orbit based on solar wind measurements, to predict MeV electrons inside geosynchronous orbit. The model results are compared with measurements from Polar/CEPPAD. Prediction efficiencies of 0.56 and 0.54, respectively, at L=6 and L=4, have been achieved over the entire year of 1998. This work wa reported at 2003 Fall AGU and has been accepted for publication in Space Weather (Barker et al., 2005). We also have used simultaneous measurements of the upstream solar wind and of energetic electrons at geosynchronous orbit to analyze the response of electrons over a very wide energy range, 50 keV-6MeV, to solar wind variations. Enhancements of energetic electron fluxes over this whole energy range are modulated by the solar wind speed and the polarity of the interplanetary magnetic field (IMF). The solar wind speed seems to be a dominant controlling parameter for electrons of all energy. This work has been published in Space Weather (Li et al., 2005).

Li, Xin-Lin

2005-01-01

424

Distant solar wind plasma - View from the Pioneers  

NASA Technical Reports Server (NTRS)

Temporal variation and spatial gradients over nearly 50 AU in heliocentric distance and about 17 deg of latitude are investigated on the basis of observations from Pioneer 10-11, Voyager 2, IMP 8, and the Pioneer Venus Orbiter. The average solar wind velocity was found to vary somewhat over the solar cycle, but at any given epoch the average velocity is essentially independent of heliocentric distance. No indication of a terminal shock or signature of interaction with the interstellar medium was found. The stream structure commonly observed in the inner heliosphere diminishes with increasing heliocentric distance, reflecting the processing of material in the stream-stream heliosphere, both at times of high sunspot activity and disturbed solar conditions, and near the solar minimum when the interplanetary current sheet is flattened.

Barnes, Aaron

1990-01-01

425

Electron densities and temperatures in the Venus ionosphere Effects of solar EUV, solar wind pressure and magnetic field  

NASA Technical Reports Server (NTRS)

The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated magnetic fields induced within the ionosphere. The existence of a substantial nightside ionosphere of Venus is thought to be due to the rapid nightward transport of dayside ionospheric plasma across the terminator. Typical solar wind conditions do not strongly affect this transport and consequently have little direct influence on nightside ionospheric conditions, except on occasions of extremely high solar wind dynamic pressure. However, both nightside electron density and temperature are affected by the presence of magnetic field, as in the case of ionospheric holes.

Elphic, R. C.; Russell, C. T.; Brace, L. H.

1985-01-01

426

Solar Rotational Periodicities and the Semiannual Variation in the Solar Wind, Radiation Belt, and Aurora  

NASA Technical Reports Server (NTRS)

The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from S to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005 -2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (approx.1980, approx.1990, and approx. 2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995-1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27 -day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the > 2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods, showing that processes in the magnetosphere act as a low-pass filter between the solar wind and the radiation belt. The A(sub p)/K(sub p) magnetic currents observed at subauroral latitudes are sensitive to proton auroral precipitation, especially for 9-day and shorter periods, while the A(sub p)/K(sub p) currents are governed by electron auroral precipitation for 13.5- and 27-day periodicities.

Emery, Barbara A.; Richardson, Ian G.; Evans, David S.; Rich, Frederick J.; Wilson, Gordon R.

2011-01-01

427

Neutral hydrogen in the solar wind acceleration region  

NASA Technical Reports Server (NTRS)

Observation of solar Ly alpha radiation scattered by coronal neutral hydrogen atoms can be used to investigate the acceleration region of the solar wind. In this paper we focus on the use of these observations to study Alfven waves, which can accelerate the solar wind plasma to flow speeds observed in high-speed streams if their amplitude at the coronal base is 20 km/s or larger. The wave amplitude is then larger than the proton thermal speed in the outer corona, so that the mean proton speed (averaged over a wave period) is significantly larger than the proton thermal speed. For low-frequency wave the hydrogen atoms follow the proton motion in the waves, while for higher frequencies the protons move relative to the neutrals. Nevertheless, in the higher frequency case, the rates for charge exchange and recombination are high enough to broaden the velocity distribution function of neutral hydrogen. Both the wave motion of the hydrogen atoms in low-frequency Alfven waves and the 'heating' by higher frequency waves lead to a broadening of the scattered solar Ly alpha line. For coronal base amplitues of 20 km/s, the line broadening increases with heliocentric distance beyond 4-5 solar radii.

Olsen, Espen Lyngdal; Leer, Egil; Holzer, Thomas E.

1994-01-01

428

Solar wind control of the earth's electric field  

SciTech Connect

The sun-weather problem is placed within an electrical framework subject to experimental investigation. An explanation is suggested for how solar variability modulates the earth's electric field. The solar wind velocity is inversely correlated with the electrical potential of the ionosphere, a measure of the overall intensity of the earth's fair-weather atmospheric electric field. In seeking a physical cause of this relationship, galactic cosmic radiation was studied and it was also found to be inversely correlated with solar wind velocity. Thus, the earth's electric field intensity which is maintained by worldwide thunderstorm currents - a meteorological phenomenon - varies in phase with cosmic radiation. Since cosmic radiation is the primary source of atmospheric ionization, these findings support a proposed mechanism in which solar control of ionizing radiation modulates atmospheric electrification and thus possibly cloud physical processes. If the latter occurred, atmospheric energetics would be affected. Sun-weather research need no longer only consist of statistical correlations; an experimental approach is described. Establishment of a proposed geoelectric index would add a new dimension to solar-terrestrial studies.

Markson, R. (Massachusetts Inst. of Tech., Cambridge); Muir, M.

1980-05-30

429

On the solar cycle dependence of winds and planetary waves as seen from mid-latitude D1 LF mesopause region wind measurements*  

E-print Network

On the solar cycle dependence of winds and planetary waves as seen from mid-latitude D1 LF-term trends and in¯uences of solar variability. The response of the prevailing wind to the 11-year solar cycle the measurements. This is connected with stronger vertical gradients of the zonal prevailing wind during solar

Paris-Sud XI, Université de

430

Solar wind iron abundance variations at solar wind speeds up to 600 km s sup -1, 1972 to 1976  

NASA Technical Reports Server (NTRS)

The Fe/H ratios in the peaks of high speed streams (HSS) were analyzed during the decline of Solar Cycle 20 and the following minimum (October 1972 to December 1976). The response of the 50 to 200 keV ion channel of the APL/JHU energetic particle experiment (EPE) on IMP-7 and 8 was utilized to solar wind iron ions at high solar wind speeds (V or = 600 km/sec). Fe measurements with solar wind H and He parameters were compared from the Los Alamos National Laboratory (LANL) instruments on the same spacecraft. In general, the Fe distribution parameters (bulk velocity, flow direction, temperature) are found to be similar to the LANL He parameters. Although the average Fe/H ration in many steady HSS peaks agrees within observational uncertainties with the nominal coronal ratio of 4.7 x 0.00001, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated HSS.

Mitchell, D. G.; Roelof, E. C.; Bame, S. J.

1982-01-01

431

Why is the Fast Solar Wind Fast and the Slow Solar Wind Slow? A Survey of Geometrical Models  

E-print Network

Four decades have gone by since the discovery that the solar wind at 1 AU seems to exist in two relatively distinct states: slow and fast. There is still no universal agreement concerning the primary physical cause of this apparently bimodal distribution, even in its simplest manifestation at solar minimum. In this presentation we review and extend a series of ideas that link the different states of solar wind to the varying superradial geometry of magnetic flux tubes in the extended corona. Past researchers have emphasized different aspects of this relationship, and we attempt to disentangle some of the seemingly contradictory results. We apply the hypothesis of Wang and Sheeley (as well as Kovalenko) that Alfven wave fluxes at the base are the same for all flux tubes to a recent model of non-WKB Alfven wave reflection and turbulent heating, and we predict coronal heating rates as a function of flux tube geometry. We compare the feedback of these heating rates on the locations of Parker-type critical points, and we discuss the ranges of parameters that yield a realistic bifurcation of wind solutions into fast and slow. Finally, we discuss the need for next-generation coronagraph spectroscopy of the extended corona - especially measurements of the electron temperature above 1.5 solar radii - in order to confirm and refine these ideas.

Steven R. Cranmer

2005-06-21

432

Solar wind and micrometeorite alteration of the lunar regolith  

NASA Technical Reports Server (NTRS)

Developments in the understanding of reduction processes which occur in the lunar regolith as a result of solar-wind bombardment and micrometeorite impacts are discussed. The mechanism is described by which water released during reduction is removed from the lunar surface, and the possible contribution of solar-wind sputtering to the reduction process is considered. It is shown that the overall reduction efficiency of incoming hydrogen ions may reach several per cent, which is sufficient to produce all the metallic iron observed in the regolith. Mossbauer spectroscopic data on the amount of metallic iron present as isolated atoms or small clusters in reduced grain surfaces are presented together with data on the metallic iron content of fines samples obtained by Mossbauer spectroscopy, ferromagnetic resonance, and scanning as well as transmission electron microscopy. A portable magnetic probe is described which has been designed for determining surface-exposure age profiles in intact lunar core and drive-tube samples.

Housley, R. M.; Cirlin, E. H.; Paton, N. E.; Goldberg, I. B.

1974-01-01

433

The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons  

E-print Network

The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow us to examine the complex plasma interactions at Pluto for the first time. Constrained to fit within minimal resources, SWAP is optimized to make plasma-ion measurements at all rotation angles as the New Horizons spacecraft scans to image Pluto and Charon during the flyby. In order to meet these unique requirements, we combined a cylindrically symmetric retarding potential analyzer (RPA) with small deflectors, a top-hat analyzer, and a redundant/coincidence detection scheme. This configuration allows for highly sensitive measurements and a controllable energy passband at all scan angles of the spacecraft.

D. McComas; F. Allegrini; F. Bagenal; P. Casey; P. Delamere; D. Demkee; G. Dunn; H. Elliott; J. Hanley; K. Johnson; J. Langle; G. Miller; S. Pope; M. Reno; B. Rodriguez; N. Schwadron; P. Valek; S. Weidner

2007-09-27

434

Residual energy in magnetohydrodynamic turbulence and in the solar wind  

E-print Network

Recent observations indicate that kinetic and magnetic energies are not in equipartition in the solar wind turbulence. Rather, magnetic fluctuations are more energetic and have somewhat steeper energy spectrum compared to the velocity fluctuations. This leads to the presence of the so-called residual energy E_r=E_v-E_b in the inertial interval of turbulence. This puzzling effect is addressed in the present paper in the framework of weak turbulence theory. Using a simple model of weakly colliding Alfv\\'en waves, we demonstrate that the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear interaction of Alfv\\'en waves. We establish that magnetic energy is indeed generated more efficiently as a result of these interactions, which proposes an explanation for the solar wind observations.

Stanislav Boldyrev; Jean Carlos Perez; Vladimir Zhdankin

2011-08-30

435

Interaction of the solar wind with the outer planets.  

NASA Technical Reports Server (NTRS)

The hypersonic analog for the interaction of the solar wind with Jupiter, Saturn, Uranus, Neptune, and Pluto is used to provide estimates of shock shapes and locations, as well as average magnetosheath and/or ionosheath properties for these planets. Several representative spacecraft flyby trajectories (designed for outer-planet 'Grand Tour' simulations) are superimposed upon a series of figures in order to provide estimates of potential plasma and field parameters which may be encountered. Consideration is given first to the possibility that several of these planets have intrinsic magnetic fields and, secondly, to the interaction of the solar wind directly on the ionosphere should there actually be no intrinsic field. Saturn and Pluto are chosen as examples of this latter case.

Dryer, M.; Rizzi, A. W.; Shen, W.-W.

1973-01-01

436

Numerical simulation of MHD shock waves in the solar wind  

NASA Technical Reports Server (NTRS)

The effects of the interplanetary magnetic field on the propagation speed of shock waves through an ambient solar wind are examined by numerical solutions of the time-dependent nonlinear equations of motion. The magnetic field always increases the velocity of strong shocks. Although the field may temporarily slow down weak shocks inside 1 AU, it eventually also causes weak shocks to travel faster than they would without the magnetic field at larger distances. Consistent with the increase in the shock velocity, the gas pressure ratio across a shock is reduced considerably in the presence of the magnetic field. The numerical method is used to simulate (starting at 0.3 AU) the large deceleration of a shock observed in the lower corona by ground-based radio instrumentation and the more gradual deceleration of the shock in the solar wind observed by the Pioneer 9 and Pioneer 10 spacecraft.

Steinolfson, R. S.; Dryer, M.

1978-01-01

437

Coronal sources of the intrastream structure of the solar wind  

NASA Technical Reports Server (NTRS)

Short time scale changes in the bulk speed were found not to coincide with X-ray transients near the sub-earth point nor with the number of X-ray bright points within a coronal hole and near the equator. The changes in bulk speed, it is shown, are associated with changes in light areas in a hole which may be associated with the opening or closing of magnetic field lines within the coronal hole. That there is a causal connection between these sudden changes (apperance or disappearance) in light area and sudden changes in the bulk speed of the solar wind is further evidenced by the spatial proximity on the Sun of these changing light re