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1

The heliospheric modulation of cosmic rays: Effects of a latitude dependent solar wind termination shock  

NASA Astrophysics Data System (ADS)

Observations made with the two Voyager spacecraft confirmed that the solar wind decelerates to form the heliospheric termination shock and that it has begun its merger with the local interstellar medium. The compression ratio of this shock affects galactic cosmic rays when they enter the heliosphere. Hydrodynamic (HD) models show that the compression ratio can have a significant latitude dependence; with the largest value in the nose direction of the heliosphere, becoming significantly less towards the polar regions. The modulation effects of such large latitude dependence are studied, using a well-established numerical drift and shock modulation model. We focus on computing the modulated spectra for galactic protons with emphasis on the radial and polar gradients in the equatorial plane and at a polar angle of ? = 55°, corresponding to the heliolatitude of Voyager 1. Two sets of solutions are computed and compared each time; with and without a latitude dependence for the compression ratio. All computations are done for the two magnetic field polarity cycles assuming solar minimum conditions. Including the termination shock in the model allows the study of the re-acceleration of galactic protons in the outer heliosphere. We find that for the A < 0 polarity cycle the intensity between ˜200 MeV and ˜1 GeV in the vicinity of the shock in the heliospheric equatorial plane may exceed the local interstellar value specified at the heliopause. Unfortunately, at ? = 55°, the effect is reduced. This seems not possible during an A > 0 cycle because significant modulation is then predicted between the heliopause and the termination shock, depending on how strong global gradient and curvature drifts are in the heliosheath. The overall effect of the shock on galactic protons in the equatorial plane is to reduce the total modulation as a function of radial distance with respect to the interstellar spectrum. Making the compression ratio latitude dependent enhances these effects at energies E < 200 MeV in the equatorial plane. At larger heliolatitudes these effects are even more significant. The differences in the modulation between the two drift cycles are compelling when the compression ratio is made latitude dependent but at Earth this effect is insignificant. A general result is that the computed radial gradient changes for galactic protons at and close to the TS and that these changes are polarity dependent. In line with previous work, large polarity dependent effects are predicted for the inner heliosphere and also close to the shock’s position in the equatorial plane. In contrast, at ? = 55°, the largest polarity effect occurs in the middle heliosphere (50 AU), enhanced by the latitude dependence of the compression ratio. At this latitude, the amount of proton modulation between the heliopause and the termination shock is much reduced. If galactic cosmic rays were to experience some diffusive shock acceleration over the 100-1000 MeV range at the shock, the radial gradient should change its sign in the vicinity of the shock, how large, depends on the compression ratio and the amount of drifts taking place in the outer heliosphere. The effective polar gradient shows a strong polarity dependence at Earth but this dissipates at ? = 55°, especially with increasing radial distance. This tendency is enhanced by making the compression ratio latitude dependent.

Ngobeni, M. D.; Potgieter, M. S.

2010-08-01

2

Depth and latitude dependence of the solar internal angular velocity  

SciTech Connect

One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone. 43 refs.

Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. (Southern California Univ., Los Angeles, CA (USA) JPL, Pasadena, CA (USA) Roma I Universita (Italy) California Univ., Los Angeles (USA))

1990-03-01

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

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

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

Latitude dependence of Thermospheric Neutral Winds and Plasma Drifts: Observations and modelling  

Microsoft Academic Search

We report on the coupling between thermospheric winds and ionospheric electrodynamics using the first coordinated set of low latitude groundbased diagnostics in the same longitude sector. All-sky imagers in Arequipa, Perú (16.5° S, 71.5° W, dip latitude = -2.7° ), and in Tucumán, Argentina (26.5° S, 65° W, dip latitude = -14.5° ), are used to track the plasma drift

C. Martinis; J. Meriwether; M. Biondi; R. Niciewjewski; V. Eccles; C. Fesen; M. Mendillo

2001-01-01

7

Latitude dependency of solar flare index-temperature relation occuring over middle and high latitudes of Atlantic-Eurasian region  

NASA Astrophysics Data System (ADS)

By applying multitaper methods and Pearson test on the surface air temperature and flare index used as a proxy data for possible solar sources of climate-forcing, we investigated the signature of these variables on middle and high latitudes of the Atlantic-Eurasian region (Turkey, Finland, Romania, Ukraine, Cyprus, Israel, Lithuania, and European part of Russia). We considered the temperature and flare index data for the period ranging from January 1975 to the end of December 2005, which covers almost three solar cycles, 21st, 22nd, and 23rd.We found significant correlations between solar activity and surface air temperature over the 50-60° and 60-70° zones for cycle 22, and for cycle 23, over the 30-40°, 40-50°, and 50-60° zones.The most pronounced power peaks for surface air temperature found by multitaper method are around 1.2, 1.7, and 2.5 years which were reported earlier for some solar activity indicators. These results support the suggestion that there is signature of solar activity effect on surface air temperature of mid-latitudes.

Kilcik, A.; Özgüç, A.; Rozelot, J. P.

2010-12-01

8

A RHESSI and SDO Campaign Measuring Latitude-dependent Limb Profiles and Oblateness of the Optical Solar Disk II  

NASA Astrophysics Data System (ADS)

The SDO spacecraft conducts special roll maneuvers every 6 months. These SDO maneuvers enable its HMI instrument to obtain precise observations of the global structure of the limb. During the SDO roll on 2011 April 6 05:50-12:30 UT, we also successfully obtained RHESSI optical observations at very high cadence, 128 samples per sec for each of the three linear CCDs. A second coordinated observation with optimized parameter settings for RHESSI is planned for the time of the SDO roll maneuver in April 2012. The data from the two instruments (RHESSI/SAS and SDO/HMI), give different means for the investigation of the variation of the solar limb properties as a function of position angle (latitude). At the normal RHESSI cadence very long integrations (of order 3 months) are needed to obtain precise limb measurements, but in this case we are able to report results within the exact time frame of the SDO roll maneuver. The special RHESSI data rate was about 10,000 times larger than the standard rate and will achieve high precision in a relatively short time. We will compare these results with our earlier RHESSI observations (Fivian et al., 2008) and those obtained by Kuhn et al. (1998) and Emilio et al. (2007) with the earlier MDI roll maneuvers, and as well as with the most recent analysis of HMI data.

Fivian, Martin; Hudson, H. S.; Lin, R. P.; Bush, R. I.; Emilio, M.; Kuhn, J. R.; Scholl, I. F.

2012-05-01

9

A RHESSI And SDO Campaign Measuring Latitude-dependent Limb ProfilesAnd Oblateness Of The Optical Solar Disk  

NASA Astrophysics Data System (ADS)

The SDO spacecraft conducted a special roll maneuver, 2011 April 6 05:50-12:30 UT, to enable its HMI instrument to obtain precise observations of the global structure of the limb. Similar maneuvers had been carried out with SOHO for MDI in the past. On this occasion we also successfully obtained RHESSI optical observations at very high cadence, 128 samples per sec for each of the three linear CCDs. The data from the two instrument (RHESSI/SAS and SDO/HMI), give different means for the investigation of the variation of the solar limb properties as a function of position angle (latitude). At the normal RHESSI cadence very long integrations (of order 3 months) are needed to obtain precise limb measurements, but in this case we expect to be able to report results within the exact time frame of the SDO roll maneuver. The special RHESSI data rate was about 10,000 times larger than the standard rate and will achieve high precision in a relatively short time. We will compare these results with our earlier RHESSI observations (Fivian et al., 2008) and those obtained by Kuhn et al. (1998) and Emilio et al. (2007) with the earlier MDI roll maneuvers.

Fivian, Martin; Hudson, H. S.; Lin, R. P.; Bush, R. I.; Emilio, M.; Kuhn, J. R.; Scholl, I. F.

2011-05-01

10

Solar Wind Composition  

NASA Astrophysics Data System (ADS)

To first order the solar wind composition reflects the composition of the source material, which is photospheric (SOLAR ABUNDANCES). However, there are some important distinctions between the solar wind and solar abundances which will be discussed in the following paragraphs. Since solar wind particles feed the CORONA, and solar energetic particles (SEPs; see SOLAR WIND: ENERGETIC PARTICLES) larg...

Bochsler, P.; Murdin, P.

2000-11-01

11

Solar Wind: Theory  

NASA Astrophysics Data System (ADS)

The supersonic outflow of electrically charged particles, mainly electrons and protons from the solar CORONA, is called the SOLAR WIND. The solar wind was described theoretically by E N PARKER, in 1958. Parker's theory was verified experimentally by in situ observations by Soviet and American spaceprobes. On its way to Venus, in 1962, the MARINER II spacecraft observed the solar wind for 104 days...

Leer, E.; Murdin, P.

2000-11-01

12

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

13

Solar cycle and latitude dependence of high-beta suprathermal plasma conditions in interplanetary space between 1.3 and 5.4 AU  

NASA Astrophysics Data System (ADS)

The analysis of energetic particles and magnetic field measurements from the Ulysses spacecraft has shown that in a series of events, the energy density contained in the suprathermal tail particle distribution is comparable to or larger than that of the magnetic field, creating conditions of high-beta plasma. In this work we analyze periods of high-beta suprathermal plasma occurrences (?ep > 1) in interplanetary space, using the ratio (?ep) of the energetic particle (20 keV to ˜5 MeV) and magnetic field energy densities from measurements covering the entire Ulysses mission lifetime (1990-2009) in order to reveal new or to reconfirm some recently defined interesting characteristics. The main key-results of the work are summarized as follows: (i) we verify that high-beta events are detected within well identified regions corresponding mainly to the vicinity of shock surfaces and magnetic structures, and associated with energetic particle intensity enhancements due to (a) reacceleration at shock-fronts and (b) unusually large magnetic field depressions. (ii) We define three considerable features for the high-beta events, concentrated on the next points: (a) there is an appreciable solar-activity influence on the high-beta events, during the maximum and middle solar-cycle phase, (b) the annual peak magnitude and the number of occurrences of high events are well correlated with the sunspot number, (c) the high-beta suprathermal plasma events present a spatial distribution in heliographic latitudes (HL) up to ˜±80°, and a specific important concentration on the low (-25° ? HL < -6°, 6° < HL ? 25°) and median (-45° ? HL < -25°, 25° < HL ? 45°) latitudes. We also reconfirm by a statistical analysis the results of Marhavilas and Sarris (2011), that the high-beta suprathermal plasma (?ep > 1) events are characterized by a very large parameter ?ep (up to 1732.5), a great total duration (406 days) and a large percentage of the Ulysses-mission lifetime (which is equal to 6.34% of the total duration with usable measurements, and 11.3% of the duration in presence of suprathermal particles events).

Marhavilas, Panagiotis K.

2012-05-01

14

Solar wind and coronal holes  

Microsoft Academic Search

The genesis of high speed solar wind streams, causing recurrent geomagnetic storms, in coronal holes, i.e., low density, low temperature regions in the corona, where the large scale magnetic field opens up into interplanetary space is reviewed. The basic physics of the solar wind emanating from coronal holes are discussed. It is shown that thermally driven solar wind models cannot

E. Leer; T. E. Holzer

1985-01-01

15

Asteroid interaction with solar wind  

Microsoft Academic Search

Motivated by the Galileo observations of asteroid-associated perturbations of the solar wind magnetic field, we have conducted analytical and numerical studies on the solar wind interaction with an asteroid. As asteroid dimensions are small compared with solar wind ion scale lengths, the interaction cannot be described in terms of magnetohydrodynamic (MHD) theory. We have obtained the solutions for the whistler

Zhi Wang; Margaret Galland Kivelson

1996-01-01

16

Solar wind stream interfaces  

Microsoft Academic Search

Results are presented for a superposed epoch analysis of discontinuous solar wind interfaces. The average time-space profiles of stream interfaces are discussed with reference to fluid properties (flow speed, pressure ridge, density, electron and proton temperatures) and kinetic properties (electron core and halo, flow speed fluctuations, electron heat flux, alpha particles). Other aspects of stream interfaces are described, such as

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

1978-01-01

17

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

18

International Solar Wind 8 Conference  

SciTech Connect

The Eighth International Solar Wind Conference brought together scientists from the various disciplines of solar wind research to present and discuss results from new and old missions (e.g., Pioneer, Voyager, and IMP-8), and to address recent advances in space physics theory. Abstracts of the oral presentations and poster session papers are presented. The presentations addressed one of four session topics: Corona and Solar/Stellar Wind Acceleration; Solar Wind Composition and Internal State; Solar Wind Structure, Dynamics, and Evolution; and Outer Heliosphere, Boundaries, and Interactions with the Local Interstellar Medium. Separate abstracts have been submitted to the database for some articles from this proceedings.

NONE

1995-06-01

19

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

20

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

21

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

22

Venus: Interaction with Solar Wind  

NASA Astrophysics Data System (ADS)

The solar wind interaction with VENUS provides the archetypal interaction of a flowing magnetized PLASMA with a PLANETARY IONOSPHERE. Mars interacts with the solar wind in much the same way as does Venus, while the rotating plasma in the Saturnian magnetosphere is believed to interact similarly with its moon, Titan (see SATURN: MAGNETOSPHERE INTERACTION WITH TITAN). The interaction of the Jovian ...

Russell, C.; Luhmann, J.; Murdin, P.

2002-07-01

23

Temperature Profile of Solar Winds.  

National Technical Information Service (NTIS)

The temperature profile of the solar wind can be calculated from the energy equation by assuming that the velocity profile is known. When the logarithmic expansion rate of the solar wind is small, the heat-flow equation can be integrated analytically. If ...

T. Yeh

1971-01-01

24

Solar and solar-wind isotopic compositions  

NASA Astrophysics Data System (ADS)

With only a few exceptions, the solar photosphere is thought to have retained the mean isotopic composition of the original solar nebula, so that, with some corrections, the photosphere provides a baseline for comparison of all other planetary materials. There are two sources of information on the photospheric isotopic composition: optical observations, which have succeeded in determining a few isotopic ratios with large uncertainties, and the solar wind, measured either in situ by spacecraft instruments or as implanted ions into lunar or asteroidal soils or collection substrates. Gravitational settling from the outer convective zone (OCZ) into the radiative core is viewed as the only solar modification of solar-nebula isotopic compositions to affect all elements. Evidence for gravitational settling is indirect, as observations are presently less precise than the predictions of <10‰ effects for the isotopes of solid-forming elements. Additional solar modification has occurred for light isotopes (D, Li, Be, B) due to nuclear destruction at the base of the convection zone, and due to production by nuclear reactions of photospheric materials with high-energy particles from the corona. Isotopic fractionation of long-term average samples of solar wind has been suggested by theory. There is some evidence, though not unambiguous, indicating that interstream (slow) wind is isotopically lighter than high-speed wind from coronal holes, consistent with Coulomb drag theories. The question of fractionation has not been clearly answered because the precision of spacecraft instruments is not sufficient to clearly demonstrate the predicted fractionations, which are <30‰ per amu between fast and slow wind for most elements. Analysis of solar-wind noble gases extracted from lunar and asteroidal soils, when compared with the terrestrial atmospheric composition, also suggests solar-wind fractionation consistent with Coulomb drag theories. Observations of solar and solar-wind compositions are reviewed for nearly all elements from hydrogen to iron, as well as the heavy noble gases. Other than Li and the noble gases, there is presently no evidence for differences among stable isotopes between terrestrial and solar photosphere compositions. Although spacecraft observations of solar-wind isotopes have added significantly to our knowledge within the past decade, more substantial breakthroughs are likely to be seen within the next several years with the return of long-exposure solar-wind samples from the Genesis mission, which should yield much higher precision measurements than in situ spacecraft instruments.

Wiens, Roger C.; Bochsler, Peter; Burnett, Donald S.; Wimmer-Schweingruber, Robert F.

2004-06-01

25

Solar and solar wind isotopic compositions  

NASA Astrophysics Data System (ADS)

With only a few exceptions, the solar photosphere is thought to have retained the mean isotopic composition of the original solar nebula, so that, with some corrections, the photosphere provides a baseline for comparison of all other planetary materials. There are two sources of information on the photospheric isotopic composition: optical observations, which have succeeded in determining a few isotopic ratios with large uncertainties, and the solar wind, measured either in situ by spacecraft instruments or as implanted ions into lunar or asteroidal soils or collection substrates. Gravitational settling from the outer convective zone (OCZ) into the radiative core is viewed as the only solar modification of solar-nebula isotopic compositions to affect all elements. Evidence for gravitational settling is indirect, as observations are presently less precise than the predictions of <10‰ effects for the isotopes of solid-forming elements. Additional solar modification has occurred for light isotopes (D, Li, Be, B) due to nuclear destruction at the base of the convection zone, and due to production by nuclear reactions of photospheric materials with high-energy particles from the corona. Isotopic fractionation of long-term average samples of solar wind has been suggested by theory. There is some evidence, although not unambiguous, indicating that interstream (slow) wind is isotopically lighter than high-speed wind from coronal holes, consistent with Coulomb drag theories. The question of fractionation has not been clearly answered, because the precision of spacecraft instruments is not sufficient to clearly demonstrate the predicted fractionations, which are <30‰/amu between fast and slow wind for most elements. Analysis of solar wind noble gases extracted from lunar and asteroidal soils, when compared with the terrestrial atmospheric composition, also suggests solar wind fractionation consistent with Coulomb drag theories. Observations of solar and solar wind compositions are reviewed for nearly all elements from hydrogen to iron, as well as the heavy noble gases. Other than Li and the noble gases, there is presently no evidence for differences among stable isotopes between terrestrial and solar photosphere compositions. Although spacecraft observations of solar wind isotopes have added significantly to our knowledge within the past decade, more substantial breakthroughs are likely to be seen within the next several years with the return of long-exposure solar wind samples from the Genesis mission, which should yield much higher precision measurements than in situ spacecraft instruments.

Wiens, Roger C.; Bochsler, Peter; Burnett, Donald S.; Wimmer-Schweingruber, Robert F.

2004-10-01

26

Wave acceleration of the fast solar wind  

Microsoft Academic Search

Observations show that the solar wind exhibits two modes of outflow: the slow (?400kms?1), high density, highly variable wind that emerges from equatorial solar regions, and the high latitude, fast (?800kms?1), low density, steady solar wind. The bi-modal solar wind outflow is most evident near minima of solar activity. Theoretical studies of the fast solar wind in open magnetic structures

Leon Ofman

2006-01-01

27

Variability of the solar wind  

NASA Astrophysics Data System (ADS)

Using data from the entire Ulysses mission (1990-2009) we quantify the variability of the solar wind using distributions of mass, momentum, and total energy measurements in the wind. For this analysis, we separate solar wind measurements according to its two dynamic states - "fast" and "slow" wind. With the advent of composition instrumentation it could be shown that heavy ion charge states are a significantly improved and more physical way for the distinction of these two states. "Fast" wind originates in relatively cool coronal holes, while the source of the "slow" wind is much less clear but must be near or above the streamer belt. Reflecting the properties of their coronal source regions, the "slow" wind is much more variable than its "fast" counterpart. In extreme cases the "slow" wind can have a speed of close to 1000 km/s. We typically find log-normal distributions of these parameters that are about three times wider in the "slow" wind, even for the momentum flux, which was often considered the least variable solar wind parameter. These data should provide important constraints for studies of solar wind turbulence.

von Steiger, R.; Zurbuchen, T.; Balogh, A.

2011-12-01

28

Heliographic latitude dependence of the IMF dominant polarity in 1972--1973 using Pioneer 10 data  

Microsoft Academic Search

The heliographic latitude dependence of the interplanetary magnetic ; field (IMF) was studied by using Pioneer 10 data taken from March 1972 through ; June 1973 over Bartels solar rotation (SR) periods 1896--1913. The daily IMF ; sector polarities were plotted for each of these SR periods. Then the number of ; days of positive polarity (''away'' directed fields) per

Ronald L. Rosenberg

1975-01-01

29

Solar Wind's Effect on Earth  

NSDL National Science Digital Library

The Sun produces a solar wind â a continuous flow of charged particles â that can affect us on Earth. It can, for example, disrupt communications, navigation systems, and satellites. Solar activity can also cause power outages, such as the extensive Canadian blackout in 1989. In this video segment adapted from NASA, learn about solar storms and their effects on Earth.

Foundation, Wgbh E.

2009-07-13

30

The distribution of solar wind speeds during solar minimum: Calibration for numerical solar wind modeling constraints on the source of the slow solar wind  

Microsoft Academic Search

It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from different sources (e.g., closed loops which open up to produce the slow solar wind) or if the

S. L. McGregor; W. J. Hughes; C. N. Arge; M. J. Owens; D. Odstrcil

2011-01-01

31

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

32

The Composition of the Solar Wind  

Microsoft Academic Search

The solar wind's charge state and elemental composition have been measured with the Solar Wind Ion Composition Spectrometers (SWICS) on Ulysses and ACE for a combined period of almost 25 years. This most extensive data set includes all varieties of solar wind flows and extends over more than one solar cycle. With SWICS the abundance of all charge states of

G. Gloeckler; L. Fisk; T. H. Zurbuchen; J. Geiss

2006-01-01

33

Solar Wind Bombardment Rates at Mercury  

Microsoft Academic Search

Because of its relatively small magnetic field and the apparent lack of an ionosphere, Mercury's interaction with the solar wind is substantially different from any other planet in the Solar System. In particular, under certain solar wind conditions, the Mercury's magnetosphere is compressed to the surface of the planet, allowing the direct access of the solar wind. The evolution of

P. Koehn; T. Zurbuchen; K. Kabin

2002-01-01

34

Periodic solar wind density structures  

NASA Astrophysics Data System (ADS)

This dissertation addresses a specific aspect of the Sun-Earth connection: we show that coronal activity creates periodic density structures in the solar wind which convect radially outward and interact with Earth's magnetosphere. First, we analyze 11 years (1995-2005) of in situ solar wind density observations from the Wind spacecraft and find that periodic density structures occur at particular sets of radial length-scales more often than others. This indicates that these density fluctuations, which have radial length-scales of hundreds of megameters, cannot be attributed entirely to turbulence. Next, we analyze their effect on Earth's magnetosphere. Though these structures are not waves in the solar wind rest frame, they appear at discrete frequencies in Earth's reference frame. They compress the magnetosphere as they convect past, driving global magnetospheric oscillations at the same discrete frequencies as the periodic density structures. Last, we investigate source regions and mechanisms of the periodic solar wind density structures. We analyze the alpha particle to proton abundance ratio during events of periodic density structures. In many events, the proton and alpha density fluctuations are anti- correlated, which strongly argues for either temporally or spatially varying coronal source plasma. We examine white light images of the solar wind taken with SECCHI HI1 on the STEREO spacecraft and find periodic density structures as near to the Sun as 15 solar radii. The smallest resolvable periodic structures that we identify are of comparable length to those found at 1 AU, providing further evidence that at least some periodic density structures are generated in the solar corona as the solar wind is formed. Guided by the properties observed during previous studies and the characteristics established through the work presented here, we examine possible candidate mechanisms in the solar corona that can form periodic density structures. We conclude that: coronal activity creates coherent structures in the solar wind at smaller size scales than previously thought; corona-formed coherent structures persist to 1 AU largely intact; finally, a significant amount of discrete frequency wave power in Earth's magnetosphere is directly driven by these structures once they reach Earth.

Viall, Nicholeen Mary

2010-01-01

35

Geoeffectiveness of Extreme Solar Winds  

NASA Astrophysics Data System (ADS)

The geoeffectiveness of the extreme solar winds that flowed pass the Earth on 24 October 2003, 07 November 2004 and 09 November 2004 are presented using Cluster (FGM, CIS, PEACE, STAFF and EFW) and ground- based (EISCAT radars at 69.6N, 19.2E and IMAGE magnetometer network at 68-79N)observations. The Cluster observations suggest that magnetic reconnection need not be the main process for solar wind entry into the magnetosphere during extreme solar winds. The ion velocity in the magnetosheath-cusp region remains strongly anti-sunward and poleward and ion density remains high irrespective of IMF Bz is negative or positive. The ion velocity components are also found to agree with the ExB velocities. The ground-based observations indicate that the extreme solar winds directly affect the high latitude ionosphere. The solar wind plasma is found to enter the ionosphere through an afternoon cusp that descends to low latitudes during negative IMF Bz period when a westward electrojet is also found to ascend to high latitudes.

Alleyne, H.; Nanan, B.; Walker, S.; Reme, H.; Lucek, E.; Andre, M.; Cornilleau-Wehrlin, N.; Fazakerley, A.; Decreau, P.; McCrea, I.; Zhang, S.; van Eyken, A.

2006-12-01

36

Solar-wind velocity decreases  

NASA Astrophysics Data System (ADS)

A model is developed to account for the solar wind electron and proton temperature decreases observed following the passage of an interplanetary shock wave and during the velocity decrease of a solar wind stream. The equations of mass and energy conservation are solved for a fully ionized, electrically neutral plasma expanding radially and spherically symmetrically, taking into account the heat flux from the solor corona to the plasma along the open magnetic field lines, and the electron thermal conductivity. An analytical relationship between the temperature and the velocity of the solar wind plasma is obtained which is found to be in agreement with experimental measurements made by the Vela 5 and 6 and IMP 6 satellites from August 1969-May 1974. It is thus proposed that the observed low plasma temperatures are due to the fact that the temperature decrease of the expanding plasma exceeds the heat gain due to thermal conduction from the corona.

Geranios, A.

1980-08-01

37

ASYMMETRIC SOLAR WIND ELECTRON DISTRIBUTIONS  

SciTech Connect

The present paper provides a possible explanation for the solar wind electron velocity distribution functions possessing asymmetric energetic tails. By numerically solving the electrostatic weak turbulence equations that involve nonlinear interactions among electrons, Langmuir waves, and ion-sound waves, it is shown that different ratios of ion-to-electron temperatures lead to the generation of varying degrees of asymmetric tails. The present finding may be applicable to observations in the solar wind near 1 AU and in other regions of the heliosphere and interplanetary space.

Yoon, Peter H.; Kim, Sunjung; Lee, Junggi; Lee, Junhyun; Park, Jongsun; Park, Kyungsun; Seough, Jungjoon [School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Hong, Jinhy [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2012-08-20

38

Viscosity in the solar wind  

SciTech Connect

The effects of viscosity on a steady, radial, spherically symmetric solar wind with an embedded, non-radial magnetic field are reconsidered. The correct expression for the classical viscosity in the presence of a non-radial magnetic field is shown to be different from that used in the past, and a means of describing non-classical viscosity is presented. A physical interpretation of the classical and nonclassical description of viscosity is provided, and observational inferences are used in discussing the nature and degree of viscous effects in the solar wind.

Holzer, T.E.; Leer, E.; Zhao, X.

1986-04-01

39

Electric Sailing under Observed Solar Wind Conditions  

Microsoft Academic Search

In this paper, sailing and navigation in the solar wind with a spacecraft powered by an electric sail is addressed. The electric sail is a novel propellantless spacecraft propulsion concept based on positively charged tethers that are centrifugally uncoiled and stabilised to extract the solar wind momentum by repelling the solar wind protons. Steering of such a sail ship is

P. K. Toivanen; P. Janhunen

2009-01-01

40

Radial Evolution of Solar Wind Speeds (Postprint).  

National Technical Information Service (NTIS)

The WSA ENLIL model predicts significant evolution of the solar wind speed. Along a flux tube the solar wind speed at 1.0 AU and beyond is found to be significantly altered from the solar wind speed in the outer corona at 0.1 AU, with most of the change o...

C. N. Arge D. Odstreil N. A. Schwadron S. L. McGregor W. J. Hughes

2012-01-01

41

Four Kinds of Solar Wind  

NASA Astrophysics Data System (ADS)

It is customary to divide the solar wind seen during sunspot minimum in distinct fast and slow regimes. Most theoretical modelling has been concerned with the fast wind since the slow wind is evidently inherently transient, associated with the opening and closing of magnetic field lines associated with quiet coronal streamers. The fast wind, associated with polar coronal holes above ˜ 60° latitude, is usually considered to be driven a result of an exponential coronal heating function sufficient to produce the observed ˜ 750 km/sec at large distances. The mass flux is conserved along magnetic flux tubes but cannot be deduced since it is determined at the coronal base, however the free parameter in the heating function must be adjusted so that the density at the base is ˜ 108/cm3 as observed. These constraints, together with a suitable magnetic field model, are sufficient to determine the flow, which exhibits very rapid acceleration. The slow wind is contained in a warped disc, sharply bounded at about ± 15° latitude. It has distinct physical characteristics and has its source in the corona below ˜ 60° latitude. The energy supply to both fast and slow winds and to the quiet corona is evidently the same in each case, namely pico-flare activity in the chromospheric network, which exhibits no significant variation in and out of corona; holes. It is noteworthy that the total energy supply to coronal holes and fast wind (˜ 7x105 erg/cm3) is the same as required for heating the quiet corona and the slow wind. However the total energy, mass flux and magnetic flux contained in the slow wind region is comparatively small. Within the slow wind region is a third component of solar wind flow, namely `bubbles' of magnetic field, produced by reconnection at the tips of coronal streamers, and marking the position of the `equatorial' current sheet. The bubbles have physical characteristics (low temperatures and absence of heat conduction, low helium abundance), which identify them clearly. Within the fast wind region there is a fourth component of the solar wind, namely coronal plumes, which outline the magnetic field configuration and are associated with bright points in the EUV emission marking the chromospheric network. This must be a relatively minor component, which eventually becomes part of the fast wind within a few tens of solar radii. Since the magnetic flux observed above 15° latitude at large distances must all map into the source of the prevailing fast wind, this wind cannot have its origin in plumes and coronal bright points as has sometimes been proposed. Close to the sun, the plume plasma is slow-moving and relatively dense compared to the inter-plume fast wind and presumably relatively cool. It must however eventually accelerate and merge with the fast wind since there is no evidence for plumes at large distances. It is suggested that this is the result of Alfven waves refracting into the plume, accumulating in intensity in the effective wave-guide, and accelerating the plasma until it reached fast wind speeds. Kelvin-Helmholtz instability may also assist the process at distances where the Alfven speed has decreased sufficiently. In this scenario it is possible that the line-of-sight column density of plume plasma is of the same order as the more extensive inter-plume plasma, masking the presence of the latter in some EUV measurements, in particular with respect to its speed and temperature(s).

Axford, W. I.

42

Atomic oxygen profiles (80 to 115 km) derived from Wind Imaging Interferometer/Upper Atmospheric Research Satellite measurements of the hydroxyl and greenline airglow: Local time-latitude dependence  

NASA Astrophysics Data System (ADS)

Hydroxyl and oxygen greenline nightglow observations from the Wind Imaging Interferometer (WINDII) are used to examine the local time-latitude variation of atomic oxygen in the mesopause region. Individual hydroxyl and greenline emission profiles from over 5 years of data are converted to oxygen mixing ratio (or concentration) profiles and then binned into local times, latitudes, and seasons. The two derived oxygen profiles from each emission are then combined into a single profile that spans a significant portion of the mesopause region (80 to 115 km). A technique developed earlier that addresses the altitude variability of the emission profiles is used. This level of agreement indicates a high degree of consistency in the radiance observations and in the photochemistry used to convert the emission rates to oxygen profiles. We demonstrate that the atomic oxygen concentration or mixing ratio profiles are very sensitive to local nighttime, and we display the manner in which they vary. The local time variation is primarily due to the tidal dynamics in the atmosphere. Comparisons between our atomic oxygen data set, a simple tidal model, and the TIME-GCM show good agreement; however, the local time tidal structure of atomic oxygen from MSISE-90 shows a 180° phase inconsistency. The measured local time oxygen variations vary with season and latitude, and we show that these oscillations are stronger under equinox conditions.

Russell, Jason P.; Ward, W. E.; Lowe, R. P.; Roble, R. G.; Shepherd, G. G.; Solheim, B.

2005-08-01

43

Distribution of Solar Wind Speeds During Solar Minimum: Calibration for Numerical Solar Wind Modeling Constraints on the Source of the Slow Solar Wind (Postprint).  

National Technical Information Service (NTIS)

It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from differen...

C. N. Arge D. Odstreil M. J. Owens S. L. McGregor W. J. Hughes

2012-01-01

44

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

45

Locating solar and wind energy sources  

Microsoft Academic Search

Renewable energy sources such as solar and wind power hold out the promise of providing energy that does not produce greenhouse gases. One obstacle to realizing production of energy from the Sun and from wind, however, has been determining where these energy sources can best be tapped.A new project called the Solar and Wind Energy Survey Assessment (SWERA) plans to

Randy Showstack

2002-01-01

46

Wind and solar energy applications study  

Microsoft Academic Search

The study on solar radiation and wind power applications is a facet of the total solar assessment program. Engineering consultants, government authorities, technology assessment specialists and businessmen were contacted for input into the report. The result is a broad implementation plan highlighting seven typical applications - three solar, three wind and one combination. It was not the intention of this

G. T. Koide; P. K. Takahashi

1977-01-01

47

Radio Wave Scattering in the Solar Wind  

Microsoft Academic Search

We have observed 60 VLBA calibrator sources affected to varying degrees by scattering in the solar wind. Our goal was to map the properties of solar wind turbulence over a wide range of solar elongations ranging from a few degrees to over 100 degrees in as short a time as possible. The final aim is to get information about (a)

K. M. Desai; K. Golap; K. R. Anantharamaiah

2000-01-01

48

Solar-wind energy conversion system  

Microsoft Academic Search

A combined solar-wind energy conversion system in which the combined effects of solar and wind energy are utilized in raising water from a lower to an upper water storage tank to increase its potential energy for generation of electricity. Incoming solar energy heats water to form steam which is temporarily stored. The stored steam is vented to one of first

1984-01-01

49

Solar-wind energy conversion system  

Microsoft Academic Search

A combined solar-wind energy conversion system in which the combined effects of solar and wind energy are utilized in raising water from a lower to an upper water storage tank to increase its potential energy for generation of electricity. Incoming solar energy heats water to form steam which is temporarily stored. The stored steam is vented to one of first

1982-01-01

50

Solar wind density influence on geomagnetic storm intensity  

Microsoft Academic Search

Solar wind density has been argued to have a strong effect on geomagnetic storms. Elevated solar wind density tends to occur in time intervals when the solar wind electric field is large. This complicates the analysis required to identify a solar wind density influence because the solar wind electric field is the dominant driver of geomagnetic storms. Statistical studies have

R. S. Weigel

2010-01-01

51

Characterization of Slow Solar Wind Sources  

NASA Astrophysics Data System (ADS)

The slow wind is a sizable component of the solar wind and plays a fundamental role in shaping the interplanetary environment and its variability. Coronal streamers are the prime source of slow solar wind plasma. We use the EUV spectrometers aboard SOHO and Hinode to characterize the physical properties of streamers and other candidate coronal source regions of slow wind. In addition, comparisons between coronal observations and in situ measurements of solar wind plasma properties are being used to further characterize the origins of slow wind streams. In order to investigate slow solar wind heating and acceleration, we also compare with predictions from three-dimensional models. We aim to use the empirical measurements to distinguish between different proposed physical processes for slow wind acceleration (e.g., waves/turbulence versus reconnection). This work is supported by NASA grant NNX10AQ58G to the Smithsonian Astrophysical Observatory.

Miralles, M. P.; Landi, E.; Cranmer, S. R.; Raymond, J. C.

2011-12-01

52

Solar cycle dependence of global distribution of solar wind speed  

Microsoft Academic Search

A review is given of observational results concerning the solar cycle dependence of the global structure of solar wind speed distribution during the years from 1973 to 1987. Since observations of solar wind speed in 3-dimensional space can only be made by the interplanetary scintillation method which has been carried out over one sunspot activity cycle since the early 1970's,

Masayoshi Kojima; Takakiyo Kakinuma

1990-01-01

53

The Solar Wind Ion Composition Spectrometer  

Microsoft Academic Search

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

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

1992-01-01

54

Solar wind and interstellar medium coupling  

Microsoft Academic Search

An overview is given of the current state of theory and modelling for the interaction between the solar wind and the interstellar\\u000a medium (ISM). The final frontiers of the solar wind, as it pushes itself into the ISM, have been an object of speculation\\u000a and analysis for many years. Observational evidence from the solar wind and heliospheric energetic particles, and

David Burgess

1997-01-01

55

How Do Wind and Solar Power Affect Grid Operations: The Western Wind and Solar Integration Study  

SciTech Connect

The Western Wind and Solar Integration Study is one of the largest regional wind and solar integration studies to date, examining the operational impact of up to 35% wind, photovoltaics, and concentrating solar power on the WestConnect grid in Arizona, Colorado, Nevada, New Mexico, and Wyoming. This paper reviews the scope of the study, the development of wind and solar datasets, and the results to date on three scenarios.

Lew, D.; Milligan, M.; Jordan, G.; Freeman, L.; Miller, N.; Clark, K.; Piwko, R.

2009-01-01

56

Wind and Solar Energy Applications Study.  

National Technical Information Service (NTIS)

The study on solar radiation and wind power applications is a facet of the total solar assessment program. Engineering consultants, government authorities, technology assessment specialists and businessmen were contacted for input into the report. The res...

G. T. Koide P. K. Takahashi

1977-01-01

57

Integrated wind and solar powered desalination facility  

SciTech Connect

This design concept for a solar desalination plant couples a state of the art solar power generation system with a reverse osmosis membrane filtration system. An average throughput of 6000 m/sup 3//d is realized through operation totally independent of interconnection with the utility grid. Alternating current electric power is generated by an integrated wind and solar energy conversion system. The optimal wind/solar ratio is very dependent upon site conditions. 7 refs.

Szostak, R.M.; Agarwal, D.; Callahan, J.T.; Mohn, J.V. III

1981-01-01

58

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

59

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.

60

Solar thermal and wind energy power source  

Microsoft Academic Search

A transparent panel enclosed tower provides a confined space for solar heating air. An upright wind turbine, mounted on the tower top, communicates with the tower enclosed space. As the solar heated air expands and becomes lighter it is displaced by cooler atmospheric air at the bottom of the tower creating a turbine driving thermal updraft in combination with wind

Argo

1980-01-01

61

Combined solar-wind power plants  

Microsoft Academic Search

The advantages offered by the combined use of wind energy and solar energy are described, and schemes for the regular electrical supply of autonomous users are proposed. Particular consideration is given to the characteristics of the energy storage units, and to recommendations on the choice and optimization of solar-wind power plants.

S. Seitkurbanov

1983-01-01

62

Expansion effects on solar wind hybrid simulations  

NASA Astrophysics Data System (ADS)

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.

2013-06-01

63

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

64

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

65

Solar- and wind-powered irrigation systems  

NASA Astrophysics Data System (ADS)

Five different direct solar and wind energy systems are technically feasible for powering irrigation pumps. However, with projected rates of fossil fuel costs, only two may produce significant unsubsidied energy for irrigation pumping before the turn of the century. These are photovoltaic systems with nonconcentrating collectors (providing that projected costs of manufacturing solar cells prove correct); and wind systems, especially in remote areas where adequate wind is available.

Enochian, R. V.

1982-02-01

66

Solar wind charge exchange and Earth's magnetosheath  

NASA Astrophysics Data System (ADS)

The solar wind experiences a shock as it approaches Earth's magnetosphere. The region between this shock and the magnetosphere is called the magnetosheath. In this region the solar wind slows down and the solar wind density and temperature increase. This is particularly the case in the sub solar nose of the magnetosheath. This region can clearly be seen in the soft X-ray emission due to charge exchange between heavy solar wind ions and geocoronal neutral hydrogen. The inner and outer boundaries of the magnetosheath are called the magnetopause and the bow shock. These boundaries can easily be seen in the modeled results of solar wind charge exchange (SWCX). The objective of this paper is to show that we can detect these boundaries in the model by using a simulated moving spacecraft (from a range of locations) during a varying solar wind. For this purpose we have created a spacecraft trajectory about 30 RE from Earth and we have used the solar wind data of numerous magneto-hydrodynamic runs.

Robertson, Ina P.; Cravens, Thomas E.; Collier, Michael R.; Sibeck, David G.; Kuntz, Kip D.; Snowden, Steven L.

2013-06-01

67

Solar wind speed variations: 1962--1974  

Microsoft Academic Search

An analysis of solar wind speed variations, with particular emphasis on changes associated with the advance of the solar activity cycle, has been completed for the period extending from 1962 through 1974. Stable, large amplitude (peak to trough greater than or equal to 350 km s⁻¹) streams were most commonly observed in years of declining and near-minimum solar activity. The

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

1976-01-01

68

Integrated wind and solar powered desalination facility  

Microsoft Academic Search

This design concept for a solar desalination plant couples a state of the art solar power generation system with a reverse osmosis membrane filtration system. An average throughput of 6000 m³\\/d is realized through operation totally independent of interconnection with the utility grid. Alternating current electric power is generated by an integrated wind and solar energy conversion system. The optimal

R. M. Szostak; D. Agarwal; J. T. Callahan; J. V. Mohn

1981-01-01

69

Electric Solar Wind Sail in tailwind  

NASA Astrophysics Data System (ADS)

The Electric Solar Wind Sail (E-sail) is a novel propulsion concept that enables faster space travel to many solar system targets. E-sail uses charged solar wind particles as the source of its propulsion. This is achieved by deploying long, conducting and charged tethers, which get pushed by the solar wind by Coulomb drag [1]. E-sail technology is being developed to technical readiness level (TRL) 4-5 by the European Union's Seventh Framework Programme for Research and Technological Development, EU FP7, in a project named ESAIL (http://www.electric-sailing.fi/fp7). Prototypes of the key parts are to be produced. The design will be scalable so that a real solar wind demonstration mission could be scaled up from them. We review here the latest results of the constantly evolving E-sail project.

Janhunen, P.; Merikallio, S.; Toivanen, P.; Polkko, J.; Haeggström, E.; Seppänen, H.; Kurppa, R.; Ukkonen, J.; Ylitalo, T.; Kiprich, S.; Koivisto, H.; Kalvas, T.; Tarvainen, O.; Kauppinen, J.; Thornell, G.; Kratz, H.; Sundqvist, J.; Grönland, T.-A.; Johansson, H.; Rangsten, P.; Vinterhav, E.; Noorma, M.; Envall, J.; Lätt, S.; Allik, V.; Voormansik, K.; Kvell, U.; Lebreton, J.-P.; Hallikainen, M.; Praks, J.; Krömer, O.; Rosta, R.; Salminen, P.; Mengali, G.; Quarta, A.; Aliasi, G.; Marcuccio, S.; Pergola, P.; Giusti, N.

2011-10-01

70

Solar winds along curved magnetic field lines  

NASA Astrophysics Data System (ADS)

Context. Both remote-sensing measurements using the interplanetary scintillation (IPS) technique and in-situ measurements by the Ulysses spacecraft show a bimodal structure for the solar wind at solar minimum conditions. At present it still remains to address why the fast wind is fast and the slow wind is slow. While a robust empirical correlation exists between the coronal expansion rate fc of the flow tubes and the speeds v measured in situ, a more detailed data analysis suggests that v depends on more than just fc. Aims. We examine whether the non-radial shape of field lines, which naturally accompanies any non-radial expansion, could be an additional geometrical factor. Methods. We solved the transport equations incorporating the heating from turbulent Alfvén waves for an electron-proton solar wind along curved field lines given by an analytical magnetic field model, which is representative of a solar minimum corona. Results. The field line shape is found to influence the solar wind parameters substantially, reducing the asymptotic speed by up to ~130 km s-1 or by ~28% in relative terms, compared with the case where the field line curvature is neglected. This effect was interpreted in the general framework of energy addition in the solar wind: compared to the straight case, the field line curvature enhances the effective energy deposition to the subsonic flow, which results in a higher proton flux and a lower terminal proton speed. Conclusions. Our computations suggest that the field line curvature could be a geometrical factor which, in addition to the tube expansion, substantially influences the solar wind speed. Furthermore, although the field line curvature is unlikely to affect the polar fast solar wind at solar minima, it does help make the wind at low latitudes slow, which in turn helps better reproduce the Ulysses measurements.

Li, B.; Xia, L. D.; Chen, Y.

2011-05-01

71

Stream interaction as a heat source in the solar wind  

Microsoft Academic Search

Proton heating at stream interaction regions in the solar wind is investigated based on the solar wind data obtained by Suisei spacecraft between 0.68 and 1.01 AU from the Sun. The deflection angle of the solar wind flow in the ecliptic plane is used to identify the interaction region. In the solar wind flows coming from east of the Sun

W. Miyake; T. Mukai; T. Terasawa; K. Hirao

1988-01-01

72

Compressibility in solar wind plasma turbulence.  

PubMed

Incompressible magnetohydrodynamics is often assumed to describe solar wind turbulence. We use extended self-similarity to reveal scaling in the structure functions of density fluctuations in the solar wind. The obtained scaling is then compared with that found in the inertial range of quantities identified as passive scalars in other turbulent systems. We find that these are not coincident. This implies that either solar wind turbulence is compressible or that straightforward comparison of structure functions does not adequately capture its inertial range properties. PMID:16090255

Hnat, Bogdan; Chapman, Sandra C; Rowlands, George

2005-05-23

73

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

74

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

NASA Astrophysics Data System (ADS)

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, D. M.; Newman, D. L.; Wilson, L. B., III; Goetz, K.; Kellogg, P. J.; Kersten, K.

2013-02-01

75

Explicit Solution for Polytrope Solar Wind Equations.  

National Technical Information Service (NTIS)

An explicit solution for polytrope solar winds is presented, in which both the distance and the flow velocity are expressed as simple functions of the mass density. The correspondence between the velocity and the distance is explicitly exhibited through t...

T. Yeh

1970-01-01

76

Ion abundances in the solar wind  

Microsoft Academic Search

studies of the elemental abundances in the corona and solar wind. The conclusions reached by Bame et al. (1968) and Hundhausen (1968) result from identification of peaks in the energy per charge (E\\/Z) spectrum from a high-resolution curved- plate analyzer. Measurements of solar wind plasma. usually show two prominent peaks in the E\\/Z spectrum. Of these two, the smaller peak

J. Lange; F. Scherb

1970-01-01

77

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

78

Solar Wind Flow with Hydrogen Pickup  

NASA Astrophysics Data System (ADS)

The interaction of the solar wind with neutral interstellar hydrogen is reconsidered. A detailed derivation of the well-known one-fluid hydrodynamic description of the solar wind modified by interstellar pickup ions is presented, based on a semikinetic guiding center description. This analysis clarifies several of the underlying assumptions implicit in Holzer's (1972) model. A brief discussion of stationary solar wind solutions modified by the interstellar neutral gas is given, and, on the basis of this analysis, we deduce that the termination shock may be interpreted as a surface of strong discontinuity with an attached weak discontinuity. Our principal result addresses the stability of the supersonic solar wind in the presence of mass, momentum, and energy loading. It is found that beyond 25 AU a gradient catastrophe can develop, which leads to the formation of the termination shock in the outer heliosphere. The location of the termination shock may be interpreted as due primarily to the properties of the interstellar neutrals (such as the value of their number density) rather than as due entirely to the balancing of the solar wind dynamic pressure and interstellar plasma pressure. Examples of recent multidimensional computations of the interaction of the solar wind with the local interstellar medium that include interstellar neutrals in a fully self-consistent manner are presented, and these provide support for the simpler one-dimensional analysis.

Khabibrakhmanov, Ildar K.; Summers, Danny; Zank, Gary P.; Pauls, H. Louis

1996-10-01

79

Shock heating of the solar wind plasma  

SciTech Connect

The authors present a study of all shocks observed from Pioneers and Voyagers in 1973-1982. The average shock strength increases with the heliocentric distance outside 1 AU, reaches a maximum near 5 AU, and then decreases with the distance. The increase in the entropy of the solar wind protons across shocks also reaches a maximum near 5 AU. When an average shock propagates through the solar wind, the shock heating increases the entropy of the solar wind protons by approximately 0.8 {times} 10{sup {minus}23} J/K/proton. They also use plasma data from Voyagers and Pioneers between 1 and 30 AU and data from IMP at 1 AU to calculate the increase in the average entropy of solar wind protons with the heliocentric distance. When the distance increases by a factor of 10, the entropy increases by about 4 {times} 10{sup {minus}23} J/K/proton. In order to evaluate the role played by shocks for the heating of the solar wind, they use a MHD simulation model to calculate the entropy changes for the November, 1977 event. Shock heating is the only heating mechanism included in the model. The calculated entropy increase agrees reasonably well with that calculated from observational data. The simulation result suggests that shocks are chiefly responsible for the heating of the solar wind plasma between 1 and 15 AU.

Whang, Y.C.; Liu, Shaoliang (Catholic Univ. of America, Washington, DC (United States)); Burlaga, L.F. (NASA Goddard Space Flight Center, Greenbelt, MD (United States))

1990-11-01

80

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

81

Combined Solar and Wind Energy Systems  

Microsoft Academic Search

In this paper we present the new concept of combined solar and wind energy systems for buildings applications. Photovoltaics (PV) and small wind turbines (WTs) can be install on buildings, in case of sufficient wind potential, providing the building with electricity. PVs can be combined with thermal collectors to form the hybrid photovoltaic\\/thermal (PV\\/T) systems. The PVs (or the PV\\/Ts)

Y. Tripanagnostopoulos; M. Souliotis; Th. Makris

2010-01-01

82

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.

83

Handbook of solar and wind energy  

Microsoft Academic Search

A general qualitative survey of the state of the art in solar and other nonfossil energy sources is presented together with a timetable of probable development. Attention is given to the relationship between solar and wind energy and the utility industry on the assumption that those most likely to exploit nonfossil energy sources are already in the energy business. Specific

F. Hickok

1975-01-01

84

Solar Wind Interaction With the Lunar Environment  

NASA Astrophysics Data System (ADS)

The Earth's Moon, lacking a substantial atmosphere or global magnetic field, presents one of the simpler obstacles to solar wind flow in our solar system. Despite this apparent simplicity, a rich array of interesting plasma physics occurs in the lunar environment. To first order, the Moon is completely unshielded from solar wind plasma and solar photons, and direct incidence of solar wind plasma can lead to implantation of volatiles and ion sputtering and pickup. The solar wind is blocked by the lunar obstacle, resulting in a plasma void on the night side. A potential drop across the wake boundary is generated as solar wind electrons attempt to refill the wake cavity, resulting in a tenuous high-temperature electron population and anisotropic ion beams in the wake. A system of diamagnetic currents is formed on the boundary surface, enhancing the magnetic field in the wake and reducing the field around it. Meanwhile, waves are generated by the unstable particle distributions generated by this interaction. On the day side, photon-driven positive charging of the lunar surface occurs. On the night side, on the other hand, charging is controlled by the tenuous wake plasma, and is generally electron-driven and negative. When the Moon traverses the Earth's magnetotail and is exposed to low-density plasma in the tail lobes and high-temperature plasma in the plasmasheet, extreme surface charging of up to hundreds of V positive and several keV negative can occur. Lunar surface charging may affect ion sputtering and likely results in significant dust transport. The presence of remanent crustal magnetism causes significant perturbations to this picture. Some crustal fields are large enough to stand off the solar wind (possibly affecting solar wind volatile implantation), and we observe large shock-like magnetic enhancements upstream from the largest crustal sources. The occurence of these "limb shocks" depends on solar wind parameters, suggesting that the crustal sources are only large enough and strong enough for solar wind plasma to react in a fluid-like way for certain upstream conditions.

Halekas, J. S.

2005-12-01

85

Simulating Upstream Solar Wind Conditions at Mercury: Results From two Independent Solar Wind Models  

Microsoft Academic Search

The knowledge of upstream solar wind conditions at Mercury is essential not only for modeling the Hermian magnetosphere-exosphere-surface system but also for interpreting the pioneering in situ observations made by MESSENGER during the January and October 2008 flybys. For this reason, and due to the fact that the MESSENGER plasma instruments cannot see the solar wind, we intend to provide

B. Zieger; K. C. Hansen; O. Cohen; T. I. Gombosi; T. H. Zurbuchen; B. J. Anderson; H. Korth

2009-01-01

86

Reconnection in the Solar Wind: An Update  

NASA Astrophysics Data System (ADS)

Magnetic reconnection plays a central role in a wide variety of observed solar and space phenomena. In the solar wind magnetic reconnection commonly occurs in a quasi-stationary mode at extended X-lines. It produces Petschek-like exhausts of roughly Alfv'enic jetting plasma typically bounded by back-to-back rotational discontinuities that bifurcate a reconnecting current sheet. It occurs at thin current sheets most frequently associated with relatively small (less than 90 deg) magnetic field rotations in low beta plasma. Reconnection exhausts are observed most frequently (typically 1-3 events/day at 1 AU) in the low-speed wind and within interplanetary coronal mass ejections, and less frequently (0.6 events/day) in the Alfv'enic turbulence characteristic of the high-speed wind from coronal holes. Reconnection occurs relatively infrequently at the heliospheric current sheet, HCS, but observations of exhausts at the HCS are particularly revealing of the magnetic field topology changes associated with the reconnection process. Reconnection in the solar wind is usually fast, but not explosive -- the magnetic energy release occurs over a long time interval following reconnection as the Alfv'enic disturbances initiated by the process propagate into the surrounding solar wind plasma. There is as yet no hard evidence that indicates that reconnection in the solar wind ever produces substantial particle acceleration.

Gosling, John

2009-11-01

87

The Interaction of the Solar Wind With Mars  

Microsoft Academic Search

The interaction of the solar wind with Mars is unique in the solar system because it combines many aspects of the solar wind interaction with other unmagnetized bodies. Like Venus, the Martian atmosphere is primarily responsible for diverting the solar wind around the planet since it lacks a significant global dipole field. Like comets, the neutral atmosphere extends into the

D. A. Brain

2005-01-01

88

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

89

Ion Heating in the Solar Corona and Solar Wind  

Microsoft Academic Search

The solar corona is the hot, ionized outer atmosphere of the Sun that expands into interplanetary space as a supersonic solar wind. This tenuous medium is a unique laboratory for the study of magnetohydrodynamics (MHD) and plasma physics with ranges of parameters that are inaccessible on Earth. The last decade has seen significant progress toward identifying and characterizing the processes

Steven Cranmer

2009-01-01

90

Ion Cyclotron Damping in the Solar Corona and Solar Wind  

Microsoft Academic Search

The solar corona is the hot, ionized outer atmosphere of the Sun. Coronal plasma expands into interplanetary space as a supersonic bulk outflow known as the solar wind. This tenuous and unbounded medium is a unique laboratory for the study of kinetic theory in a nearly collisionless plasma, as well as magnetohydrodynamic waves, shocks, and jets. Particle velocity distributions in

Steven R. Cranmer

91

Ion cyclotron damping in the solar corona and solar wind  

Microsoft Academic Search

The solar corona is the hot, ionized outer atmosphere of the Sun. Coronal plasma expands into interplanetary space as a supersonic bulk outflow known as the solar wind. This tenuous and unbounded medium is a unique laboratory for the study of kinetic theory in a nearly collisionless plasma, as well as magnetohydrodynamic waves, shocks, and jets. Particle velocity distributions in

Steven R. Cranmer

2001-01-01

92

Structure of Slow Solar Wind during Solar Activity Minimum  

NASA Astrophysics Data System (ADS)

We investigate the structure of the slow solar wind using the observations by the STEREO and Wind spacecraft during two Carrington rotations (2054 and 2055) that occurred at the time of the present solar activity minimum. At solar minimum distinct interplanetary coronal mass ejections (ICMEs) are rare, but we found that the signatures of transients with small scale-sizes and/or low magnetic field strength (comparable with the typical solar wind value) are frequently found in the slow solar wind at these times. Source mapping using models based on GONG magnetograms suggests that these transients come from the vicinity of coronal source surface sector boundaries and in-situ they are correspondingly observed near high density structures where the dominant electron heat flux reverses its flow polarity. We will discuss the properties of the identified transients and the extent the slow solar wind may be considered transient in nature. We will also discuss their connection to dynamical changes at the coronal hole boundaries where magnetic reconnection has been suggested to open up the magnetic field lines allowing the material to escape from the closed loops.

Kilpua, E. K. J.; Luhmann, J. G.; Gosling, J. T.

2009-04-01

93

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

94

ACE\\/Wind multispacecraft analysis of the magnetic correlation in the solar wind  

Microsoft Academic Search

The propagation of galactic and solar cosmic rays in the solar wind (SW) can be strongly influenced by the SW fluctuations properties. Magnetohydrodynamic (MHD) scale fluctuations in the solar wind are usually highly anisotropic, and have also been found to exhibit different properties in regions of high and low solar wind speed. Previous studies analyzed the anisotropy properties of the

S. DASSO; J. M. WEYGAND; PIYANATE CHUYCHAI; L. J. MILANO; C. W. SMITH; M. G. KIVELSON

95

Global distribution of the solar wind during solar cycle 23: ACE observations  

Microsoft Academic Search

The composition of the solar wind can be used to determine its origin at the Sun; e.g., solar wind from coronal holes has demonstrably lower charge states than solar wind of other origins. The O7+\\/O6+ ratio as measured by Advanced Composition Explorer (ACE) during 1998–2008 is used to divide the solar wind into three categories: non-transient solar wind from coronal

L. Zhao; T. H. Zurbuchen; L. A. Fisk

2009-01-01

96

Magnetohydrodynamic Simulations of the Solar Corona and Solar Wind Using a Boundary Treatment to Limit Solar Wind Mass Flux  

Microsoft Academic Search

Magnetohydrodynamic simulations of the solar corona and solar wind are sensitive to conditions in the sub-Alfvénic plasma at the base of the solar corona because the structure of the simulated solar corona is determined by the pressure balance of the plasma and the magnetic field. Therefore, it is important to construct an adequate boundary treatment for the sub-Alfvénic surface, and

Keiji Hayashi

2005-01-01

97

On the solar wind composition during the November 1997 solar particle events: WIND/MASS observations  

NASA Astrophysics Data System (ADS)

November 1997 saw a series of very intense and unusual solar particle events that have been well studied [Cohen et al., 1999; Lario et al., 1998; Mason et al., 1999; Mazur et al., 1999; Möbius et al., 1999]. However, the composition of the solar wind has not previously been analyzed. We report the elemental and charge-state composition of the solar wind during these events. We find unusually broad and high charge-state distributions for O, Si, and Fe. Fe/O was enhanced by a factor >3-5 relative to the ambient solar wind in the magnetic cloud and in the following material. We speculate whether the observed compositional similarities in the solar wind and energetic particles might, in part, be explained by a common reservoir out of which both kinds of particles were accelerated.

Wimmer-Schweingruber, Robert F.; Kern, Olivier; Hamilton, Douglas C.

1999-12-01

98

Ion beaming in the solar wind: Wind Observations and Solar Probe Plus Challenges  

NASA Astrophysics Data System (ADS)

Observations of the micro-state of ions in the solar wind have revealed that double-streaming protons carry a significant portion of the kinetic energy in the inner heliosphere, and in fast/collisionally young wind. We present the results of a comprehensive investigation into field-aligned proton beams in the solar wind at 1 AU, as observed by the Solar Wind Explorer (SWE) on the Wind spacecraft. A re-analysis of the Wind SWE data set has recently been conducted in order to characterize features in the SWE velocity distribution function that are attributable to minor ions or to secondary proton and alpha components, including Alfvénic beams. The kinetic substructure of the SWE ion velocity distribution function (VDF) contains the fingerprints of heating processes in the solar wind and in the corona, however counter-streaming proton detections also provide evidence of ongoing plasma interpenetration at magnetic reconnection exhaust sites, providing insight into the mechanism in those structures. It is shown that about 40% of simple, so-called "quasi-steady" reconnection structure that can be readily identified in the solar wind at 1 AU is associated with proton beams. This suggests that magnetic reconnection in situ may be a significant source mechanism for ion beaming. Statistics of the Wind ion beam data set are presented in the context of candidate beam origination and dissipation mechanisms. The SPC/SPAN experiment on Solar Probe Plus will measure the solar wind micro-state in a new region of the heliosphere, improving in detail and in scope upon the previous observations from the Helios missions. By considering the collisional age of plasma streams with beam structure that are not readily attributable to an in situ mechanism, our study is also used to predict the ion VDF in the inner heliosphere as it will be measured by the SPC/SPAN experiment on Solar Probe Plus.

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

2011-12-01

99

Solar Wind Properties During the Current Solar Minimum: Ulysses Observations  

NASA Astrophysics Data System (ADS)

During its nearly 19 year mission, Ulysses pioneered novel measurements of the three-dimensional heliosphere and particularly first in situ observations of solar wind from polar coronal holes (PCHs). It is thus possible to compare observations in the current, peculiar solar minimum with those obtained in 1994-95. It has been reported earlier that, during the current minimum, there is a ~ 15% reduction of the heliospheric magnetic field (Smith and Balogh, 2008), and ~ 17% and ~ 14% reduction in density and temperature, respectively (McComas et al., 2008), as compared to the previous minimum. But the PCH-associated solar wind streams show long-term variability not only in dynamic, but also in compositional signatures. From 1995 to 2008, the C and O freeze-in temperatures measured in high-latitude solar wind have decreased by ~ 15% and are now around 0.86 MK and 1.0 MK, respectively. Si and Fe ionization states also exhibit a substantial cooling with a reduction of 0.2 and 0.3 charge states, respectively. Thus it appears that the PCH of cycle 23 are cooler overall than those of cycle 22. It is more difficult to assess whether there are significant changes of the elemental composition of the solar wind, as exhibited through the First Ionization Potential fractionation effect, which seems to have remained at f = 1.8 ± 0.3 during both sets of polar passages, i.e., enhanced to the photospheric composition (f = 1). If this can be confirmed the streams from PCH would truly be the 'ground state' of the solar wind. These observations provide a unique test for theories of the solar wind and its composition. We will present results from this data analysis and also provide a discussion of their scientific implications.

von Steiger, Rudolf; Zurbuchen, Thomas H.

2010-05-01

100

Electron Heating in the Fast Solar Wind  

Microsoft Academic Search

In-situ observations of charge states of fast solar wind ions revealhigher average charges than the coronal hole source regions asderived from spectroscopy, implying that some extra electron heatingand ionization must have occurred in the wind acceleration regionprior to freeze-in. We present an extensive analysis of Ulysses andACE charge state data near the boundaries of different coronalholes, and from different regions

J. M. Laming; S. T. Lepri

2006-01-01

101

Quiet and Disturbed Solar Wind in the New Solar Cycle  

NASA Astrophysics Data System (ADS)

Observations of the solar wind since the beginning of the STEREO mission in 2007 show the notably weak solar wind and interplanetary field described in the literature persists even in the face of the increasing activity of solar cycle 24. These conditions have produced on average low values of geoeffective parameters such as solar wind dynamic pressure and the southward component of the interplanetary field -Bz. In addition, the magnetic disturbances associated with interplanetary coronal mass ejections (ICMEs) have been primarily northward in their leading edges where their fields are compressed by their ambient solar wind interaction. This combination has generally reduced the strengths of storms produced by the ICMEs and stream interaction regions. Interestingly, the rate of CMEs in coronal images has been similar to the previous cycle which had a significantly higher sunspot number and related solar surface field. We summarize how recent conditions on the Sun have modified those that affect the Earth and planets, and the likely trends we may expect.

Luhmann, Janet G.; Jian, Lan; Galvin, Antoinette; Simunac, Kristin; Kilpua, Emilia; Russell, Christopher; Ellenburg, Michael

2012-07-01

102

Extended Self Similarity in Solar Wind Turbulence  

NASA Astrophysics Data System (ADS)

The solar wind provides a natural laboratory for observations of MHD turbulence over extended temporal scales. A hallmark of turbulence is scaling- and scaling in the Probability Density Functions (PDF) of fluctuations in certain solar wind in- situ bulk plasma parameters has been established from WIND and ACE observations on `short' timescales up to a few hours. On longer timescales there is a crossover in scaling to uncorrelated behaviour. The intermittency of the system is expressed in these parameters through the non-Gaussian nature of the fluctuations PDF up to this timescale. Here we apply a generic approach to turbulence- that of Extended Self Similarity (ESS)- to the analysis of solar wind observations. We find that ESS can extend the range of scaling and for some parameters reveals two distinct scaling regions for the `short' and long timescales, whereas for others, a single scaling encompasses the behaviour over the full range of timescales. That certain parameters, and conditions, can be distinguished via ESS may provide physical insight into the turbulent solar wind.

Rowlands, G.; Chapman, S. C.; Hnat, B.

2005-12-01

103

Alfvén wave mixing in the solar wind  

NASA Astrophysics Data System (ADS)

Alfven wave mixing equations used in locally incompressible turbulence transport equations in the solar wind are analyzed from the perspective of linear wave theory. A Green's formula is developed for the wave mixing equations, in which the formal solution of boundary value and initial value problems for the wave mixing equations are given in terms of the adjoint Green's functions. The linear wave mixing equations with no sources are expressed in terms of variational principles, and conservation laws of the equations are obtained. We discuss the possible use of Green's formulas in turbulence transport in the solar wind.

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

2013-06-01

104

Standing shocks in the inner solar wind  

SciTech Connect

It has been pointed out by several authors that the equations describing rapidly diverging flow in the solar wind and in related astrophysical systems allow for solutions with standing shocks in the acceleration region of the flow. The range of plasma and flow-geometry parameters that allow for such solutions are investigated. It is shown that, for reasonable geometries, shocks can occur only for a very narrow range of flow parameters in the case of the solar wind. Similar results can be expected for related astrophysical systems. 20 refs.

Leer, E.; Holzer, T.E. (Oslo Universitetet (Norway) High Altitude Observatory, Boulder, CO (USA))

1990-08-01

105

Solar wind parameters and substorm occurence  

NASA Astrophysics Data System (ADS)

Three different phenomena are used to for automated detection of substrom onsets: (1) A rapid increase in the mid-latitude asymmetric disturbance index ASY-D. (2) A sharp decrease in the AL index. (3) An onset of Pi2 geomagnetic pulsation data from Kakioka observatory. The solar wind data where obtained from the NSSDC OMNI database for the years: 1985-1987 and 1990-2001. Based on this dataset, we analyzed the substorm occurrence frequency and its dependence on Bz ( interplanetary magnetic field Z-component in GSM coordinates), Np ( proton density) and SWS (solar wind speed). Our results indicate a strong control of SWS on substorm occurrence frequency.

Silbergleit, V.; Iyemori, T.

106

Solar wind composition from the Moon;  

NASA Astrophysics Data System (ADS)

The lunar regolith contains the best accessible record of the solar wind composition of the past few billion years. Interpreting this record crucially depends on our understanding of the implantation mechanisms, potential alternative sources other than the solar wind, storage and degradation processes, and transport- and loss-mechanisms of trapped particles in the regolith. We therefore suggest that a future mission to the Moon should contain the following objectives: (1) A thorough in-situ investigation of the contemporary solar wind composition by means of long-duration exposure experiments with various techniques as baseline for investigation of the historic and ancient solar wind. (2) A multidisciplinary program, involving an experimental investigation of implantation-, storage- and loss-processes of solar particles at the conditions of the lunar environment. This program is complementary to an elaborated systematic sampling of all layers of the lunar regolith, based on the experience from the Apollo- and the Luna-missions. Difficulties with the interpretation of the lunar record are illuminated in the case of surface correlated nitrogen. (3) A complementary goal for the extensive sampling of the lunar surface is the documentation of the lunar regolith for future generations, prior to extended human activites which could have detrimental effects to the lunar environment.

Bochsler, P.

1994-06-01

107

The Relationship Between Magnetosheath and Solar Wind Parameters  

Microsoft Academic Search

In general, solar wind drives magnetospheric activity and is used to quantify it. In reality, it is the magnetosheath which is in contact with the magnetosphere. Parameters in the magnetosheath therefore modulate magnetospheric activity. We expect that the relationship between solar wind and magnetosheath parameters will have a linear relationship at low solar wind magnetic field values. However, at high

Crystal Red Eagle; Phyllis Whittlesey; Robert Allen; Sophia Cockrell; Elizabeth Mitchell; Ramon Lopez

2009-01-01

108

Apollo 11 Solar Wind Composition Experiment: First Results  

Microsoft Academic Search

The helium-4 solar wind flux during the Apollo 11 lunar surface excursion was (6.3 ± 1.2) × 106 atoms per square centimeter per second. The solar wind direction and energy are essentially not perturbed by the moon. Evidence for a lunar solar wind albedo was found.

F. Buehler; P. Eberhardt; J. Geiss; J. Meister; P. Signer

1969-01-01

109

Solar wind: Internal parameters driven by external source  

Microsoft Academic Search

A new concept interpreting solar wind parameters is suggested. The process of increasing twofold of a moving volume in the solar wind (with energy transfer across its surface which is comparable with its whole internal energy) is a more rapid process than the relaxation for the pressure. Thus, the solar wind is unique from the point of view of thermodynamics

A. D. Chertkov

1995-01-01

110

Solar wind driven magnetosphere: Are we asking the right questions?  

Microsoft Academic Search

High solar wind speed together with a southward component of the interplanetary magnetic field are key elements in energy, momentum, and plasma transfer processes from the solar wind to the magnetosphere. The product of these, the rectified dawn-to-dusk electric field Ey, is the simplest coupling function, which highlights the role of dayside reconnection as the primary solar wind - magnetosphere

H. Koskinen

2009-01-01

111

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

112

Kinetic Models of the Solar Wind: Achievements and Fundamental Questions  

Microsoft Academic Search

Recent kinetic models of the solar corona and of the solar wind will be presented with emphasis on the characteristics of the particle velocity distribution function (VDF). ULYSSES and WIND have observed that the VDF of the solar wind particles deviate significantly from Maxwellians. Using exospheric collisionless models based on the solution of Vlasov equation, we show that the presence

V. Pierrard

2008-01-01

113

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

114

Solar wind modification upstream of the bow shock  

NASA Astrophysics Data System (ADS)

A spacecraft configuration with two monitors near L1 and a fleet of the spacecraft orbiting in front of the bow shock brings a great opportunity to test the propagation techniques for the solar wind and the assumption on a negligible solar wind parameter evolution. We use multi-point observations of the THEMIS-ARTEMIS mission and compare them with data from the Wind solar wind monitor in order to estimate different factors influencing solar wind speed evolution. We have found a significant deceleration (up to 6%) of the solar wind close to the bow shock and the effect extends up to 30 RE from the Earth. It is controlled by the level of magnetic field fluctuations and by the flux of reflected and accelerated particles. We can conclude that the reflected particles not only excite waves of large amplitudes but also modify mean values of the solar wind speed measured in an unperturbed solar wind.

Urbá?, J.; N?me?ek, Z.; P?ech, L.; Šafránková, J.; Jelínek, K.

2013-06-01

115

CORONAL PLUMES IN THE FAST SOLAR WIND  

SciTech Connect

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 {approx}50 km s{sup -1}, 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 distances 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 [Jet Propulsion Laboratory, Pasadena, CA 91109 (United States); Lionello, Roberto; Linker, Jon A.; Mikic, Zoran, E-mail: mvelli@mail.jpl.nasa.gov, E-mail: lionel@predsci.com, E-mail: linkerj@predsci.com, E-mail: mikicz@predsci.com [Predictive Science, Inc., San Diego, CA 92121-2910 (United States)

2011-07-20

116

Solar wind–magnetosphere coupling efficiency for solar wind pressure impulses  

Microsoft Academic Search

We investigate the solar wind–magnetosphere coupling efficiency in response to solar wind dynamic pressure impulses. We carry out a superposed epoch analysis of 236 pressure impulses from the years 1998–2002 detected by the ACE\\/SWEPAM instrument. For the coupling efficiency, we use four definitions based on: the polar cap potential from SuperDARN radars, the northern polar cap index (PCN), the available

M. Palmroth; N. Partamies; J. Polvi; T. I. Pulkkinen; D. J. McComas; R. J. Barnes; P. Stauning; C. W. Smith; H. J. Singer; R. Vainio

2007-01-01

117

Evolution of solar-type stellar winds  

NASA Astrophysics Data System (ADS)

By extending our self-consistent MHD simulations for the solar wind, we study the evolution of stellar winds of solar-type stars from early main sequence stage to red giant phase. Young solar-type stars are active and the mass loss rates are larger by up to ˜100 times than that of the present-day sun. We investigate how the stellar wind is affected when the magnetic field strength and fluctuation amplitude at the photosphere increase. While the mass loss rate sensitively depends on the input energy from the surface because of the global instability related to the reflection and nonlinear dissipation of Alfvén waves, it saturates at ˜100 times because most of the energy is used up for the radiative losses rather than the kinetic energy of the wind. After the end of the main sequence phase when the stellar radius expands by ˜10 times, the steady hot corona with temperature 106 K, suddenly disappears. Chromospheric materials, with hot bubbles embedded owing to thermal instability, directly stream out; the red giant wind is not a steady stream but a structured outflow.

Suzuki, T. K.

2013-02-01

118

Electron Heating in the Solar Wind  

Microsoft Academic Search

We report on progress in modeling the elevated charge states observed in the fast solar wind with respect to the coronal hole source region. Improvements include the incorporation of new atomic data for dielectronic recombination of L-shell ions in our modeling, following the recent work of Badnell and collaborators. A second issue considered will be that of magnetic field inhomogeneity

M. Laming

2005-01-01

119

Solar and wind energy resources and prediction  

Microsoft Academic Search

Energy and environmental issues are among the most important problems of public concern. There are increasing debates about whether to resort to drilling more oil and mining more coal or to using renewable, sustainable, and clean resources such as solar and wind energies. Through our analyses and modeling on the basis of the National Center for Environment Prediction data, we

Quanhua Liu; Qinxian Miao; Jue J. Liu; Wenli Yang

2009-01-01

120

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

121

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.

122

ISEE-C Solar Wind Plasma Experiment  

Microsoft Academic Search

Two 135° spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are

S. J. Bame; J. R. Asbridge; H. E. Felthauser; J. P. Glore; H. L. Hawk; J. Chavez

1978-01-01

123

Solar wind in the distant heliosphere  

Microsoft Academic Search

This paper presents a quantitative MHD model to study the effects of pickup protons on the solar wind. The model includes the kinetic theory solution of interstellar neutral hydrogen, the ionization process for the production of pickup protons, the spiral interplanetary magnetic field, and the full MHD equations. In order to study the effects of pickup protons, we first obtain

Y. C. Whang

1998-01-01

124

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

125

Solar wind-Magnetosphere Interaction at Mercury  

Microsoft Academic Search

Since Mercury's sodium exosphere was discovered in 1986, two competing mechanisms have been proposed to account for the rapid time variability and high latitude enhancements seen in sodium emission. We developed an analytical model of the Hermean magnetosphere, based on the Toffoletto-Hill 1993 model, to determine the locus of field lines for particular conditions of solar wind speed, density and

M. Sarantos; P. H. Reiff; T. W. Hill; R. M. Killen

2001-01-01

126

Waves and irregularities in the solar wind  

Microsoft Academic Search

This review is not meant to be for the specialist who already knows the subject area but rather for the nonspecialist who wants a simple physical picture. Therefore some simple calculations are given to show why waves and irregularities in the solar wind are of importance in obtaining a physical understanding of the dynamical processes occurring in the interplanetary medium.

M. A. Lee; I. Lerche

1974-01-01

127

Helium abundance in the solar wind  

Microsoft Academic Search

Observations of hydrogen and helium ions in the solar wind have been carried out by the Goddard Space Flight Center - University of Maryland plasma instrument on Explorer 34. These ions are completely separated by means of electrostatic and magnetic fields. The average value of the ratio of number densities is 0.051 ± .02, derived from over 3000 h of

K. W. Ogilvie; T. D. Wilkerson

1969-01-01

128

Double ion streams in the solar wind  

Microsoft Academic Search

Distinct interpenetrating ion streams have been identified in the solar wind for the first time. They are shown to be interplanetary in origin and to be associated with the filling in of regions of density rarefactions accompanying high-velocity streams. With few excep- tions, the ion stream with the lower-energy density flux has higher energy. Furthermore, nonradial magnetic field directions seem

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

1973-01-01

129

The Origin of the Solar Wind  

NASA Astrophysics Data System (ADS)

Nearly 1,400 years ago, Chinese astronomers noticed that comet tails always point away from the Sun. They concluded that the Sun must have chi—a basic life force—that blows the tails away. It wasn't until the middle of the 20th century that scientists understood that this "force" actually consisted of little pieces of the sun itself—protons and electrons—blowing out into the solar system as a "wind" at more than a million kilometers per hour. The traditional view of the solar wind's origins suggests that it originates from special regions on the Sun, called coronal holes. Woo and Habbal present new evidence showing that the wind actually emanates from all regions on the Sun.

Woo, Richard; Habbal, Shadia Rifai

2002-12-01

130

Solar Wind Properties During the Current Solar Minimum: Ulysses Observations  

NASA Astrophysics Data System (ADS)

Using Ulysses solar wind composition data it is possible to compare observations in the current, unusual solar minimum with those obtained during the minimum in 1994-95. It has been re-ported earlier that, during the current minimum, there is a ˜ 15% reduction of the heliospheric magnetic field (Smith and Balogh, 2008), and ˜ 17% and ˜ 14% reduction in density and temperature, respectively (McComas et al., 2008), as compared to the previous minimum. But the polar coronal hole (PCH)-associated solar wind streams show long-term variability not only in dynamic, but also in compositional properties. The observed trends provide powerful tools to investigate the properties of the underlying corona during this time. From 1995 to 2008, the C and O freeze-in temperatures measured in high-latitude solar wind have steadily decreased by ˜ 15% and are now around 0.86 MK and 1.0 MK, respectively. Si and Fe ionization states also exhibit a substantial cooling with a reduction of 0.2 and 0.3 charge states, respectively. Thus it appears that all observed PCHs of cycle 23 are cooler overall than those of cycle 22. It is more difficult to assess whether there are significant changes of the elemental composition of the solar wind, as exhibited through the First Ionization Potential fractionation effect, which seems to have remained at f = 1.8 ± 0.3 during all polar passages. These observations provide a unique test for theories of the solar wind and its composition. Furthermore, the comparative analysis of the corona with these data provides important insights about the physical processes that link the Sun and its heliosphere.

von Steiger, Rudolf; Zurbuchen, Thomas H.

131

On Solar-Wind Electron Heating at Large Solar Distances  

NASA Astrophysics Data System (ADS)

We study the temperature of electrons advected with the solar wind to large solar distances far beyond 1 AU. Almost nothing is known about the thermodynamics of these electrons from in-situ plasma observations at these distances, and usually it is tacitly assumed that electrons, due to adiabatic behaviour and vanishing heat conduction, rapidly cool off to very low temperatures at larger distances. In this article we show, however, that electrons on their way to large distances undergo non-adiabatic interactions with travelling shocks and solar-wind bulk-velocity jumps and thereby are appreciably heated. Examining this heating process on an average statistical basis, we find that solar-wind electrons first cool down to a temperature minimum, which depending on the occurrence frequency of bulk velocity jumps is located between 3 and 6 AU, but beyond this the lowest electron temperature again starts to increase with increasing solar distance, finally achieving temperatures of about 7×104 K to 7×105 K at the location of the termination shock. Hence these electrons are unexpectedly shown to play an important dynamical role in structuring this shock and in determining the downstream plasma properties.

Chashei, Igor V.; Fahr, Hans J.

2013-09-01

132

The Composition of the Solar Wind in Polar Coronal Holes  

Microsoft Academic Search

The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers\\u000a (SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of\\u000a solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of

George Gloeckler; Johannes Geiss

2007-01-01

133

The Composition of the Solar Wind in Polar Coronal Holes  

Microsoft Academic Search

\\u000a The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers\\u000a (SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of\\u000a solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of

George Gloeckler; Johannes Geiss

134

Laboratory experiments simulating solar wind driven magnetospheres  

SciTech Connect

Magnetosphere-solar wind interactions are simulated in a laboratory setting with a small permanent magnet driven by two types of supersonic plasma wind sources. The first higher speed, shorter duration plasma wind is from a laser blow-off plasma while the second longer duration, lower speed plasma wind is produced with a capacitor discharge driven coaxial electrode creating plasma jets. The stand off distance of the solar wind from the magnetosphere was measured to be 1.7{+-}0.3 cm for the laser-produced plasma experiment and 0.87{+-}0.03 cm for the coaxial electrode plasma experiment. The stand off distance of the plasma was calculated using data from HYADES[J. T. Larsen and S. M. Lane, J. Quant. Spectrosc. Radiat. Transf. 51, 179 (1994)] as 1.46{+-}0.02 cm for the laser-produced plasma, and estimated for the coaxial plasma jet as r{sub mp}=0.72{+-}0.07 cm. Plasma build up on the poles of the magnets, consistent with magnetosphere systems, was also observed.

Brady, P.; Ditmire, T. [Fusion Research Center, The University of Texas at Austin, Austin, Texas 78712 (United States); Horton, W.; Mays, M. L. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Zakharov, Y. [Institute of Laser Physics, Russian Academy of Sciences, Novosibirsk 630090, Av. Lavrentyeva 13/3 (Russian Federation)

2009-04-15

135

Oxygen 16 to oxygen 18 abundance ratio in the solar wind observed by Wind/MASS  

NASA Astrophysics Data System (ADS)

Measurements of the O-16 and O-18 distribution functions in the solar wind at low to average solar wind speeds from the MASS instrument on the Wind spacecraft are reported. The O-16/O-18 density ratio is 450 +/- 130, a value consistent with terrestrial, solar photospheric, solar energetic particle, and galactic cosmic ray O-16/O-18 isotopic ratios. This study constitutes the first reported spacecraft measurement of the isotope O-18 in the core solar wind and may represent the best determination of the solar O-16/O-18 density ratio to date.

Collier, Michael R.; Hamilton, D. C.; Gloeckler, G.; Ho, G.; Bochsler, P.; Bodmer, R.; Sheldon, R.

1998-01-01

136

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

137

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

138

The Large-Scale Variability of Solar Wind Streams  

Microsoft Academic Search

Fast and slow solar wind are fundamentally different. In particular, slow solar wind shows a significant and persistent variability that is absent in the fast wind. It is generally believed that this structure is driven by a combination of temporal and spatial variations, however, its origin remains poorly understood. It has been suggested, for example, that the super-radial expansion of

P. Riley; Z. Mikic; J. A. Linker; R. Lionello; A. J. Lazarus

2001-01-01

139

Ion Heating in the Solar Corona and Solar Wind  

NASA Astrophysics Data System (ADS)

The solar corona is the hot, ionized outer atmosphere of the Sun that expands into interplanetary space as a supersonic solar wind. This tenuous medium is a unique laboratory for the study of magnetohydrodynamics (MHD) and plasma physics with ranges of parameters that are inaccessible on Earth. The last decade has seen significant progress toward identifying and characterizing the processes that heat the corona and accelerate the solar wind, but the basic physics is still unclear. Some key clues about the mechanisms responsible for energizing the plasma have come from UV spectroscopy of the extended corona (i.e., using a combination of an occulting coronagraph and a spectrometer). There is evidence for preferential acceleration of heavy ions in the fast solar wind, ion temperatures exceeding 100 million K, and marked departures from Maxwellian velocity distributions. These collisionless departures from thermal equilibrium point to specific types of kinetic processes. This presentation reviews the measurements (both telescopic and from `in situ' probes) that constrain theoretical explanations and provides a current survey of the landscape of proposed ideas for ion energization. Many of the suggested processes are related to the dissipation of MHD waves (e.g., ion cyclotron waves), and many involve multiple steps of energy conversion between waves, turbulence, current sheets, and other nonlinear plasma features. A discussion of future measurements that could help to test, refine, and possibly winnow down the list of competing models will also be presented.

Cranmer, Steven

2009-05-01

140

On tracing the origins of the solar wind  

NASA Astrophysics Data System (ADS)

Since the 1960s, in situ observations have shown that the solar wind is comprised of two distinct states: slow (300-550 km/s) and fast (600-800 km/s). Temperature, density, and compositional variations between the two suggest different sources for the fast and slow solar wind. Several theories have been proposed to explain the speed and the compositional differences between the two wind types. Waves-driven models rely on the structure and geometry of the coronal magnetic field to explain the differences. Others argue that the Sun is inherently dynamic, with flux tubes reconfiguring and tapping into heated closed coronal loops. This thesis investigates these issues by using coronal and solar wind models. Using a semi-empirical coronal model I derive a new empirical relationship for the solar wind speed at 0.1 AU based on the magnetic field configuration in the corona. This new empirical relationship exposes how the fast and slow solar wind speeds are controlled by different coronal parameters. I also find that the solar wind observations used to distinguish between fast and slow solar wind are not as unambiguous as previously thought. The solar wind speed can evolve significantly in the inner (less than 0.4 AU) heliosphere, confusing source region identification of in situ observations. When the evolution of the solar wind speed is accounted for, it produces a greater separation in the fast and slow coronal speed populations and also explains observed compositional variations that were found to be dependent on the observer's heliographic latitude. Investigating the solar wind composition variations during solar minimum shows that there are two populations of slow solar wind. These populations can be distinguished by their relative helium abundance. I find that a combination of present theories, including both the time dependent nature and large scale magnetic structure of the corona, are required to best explain solar wind sources and observations.

McGregor, Sarah Lynn

141

Observed Properties of the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

The source of the slow solar wind is poorly understood, in part because observations of its properties have led to conflicting phenomenological views. To provide a sound basis for a synthesis view and, ultimately, for a successful physical model, the observed properties are reviewed with minimal reference to interpretation. Slow wind properties can be sorted into three categories according to scale size. At large scales they include depressed temperature and helium abundance and elevated density, charge-state ratios, and elemental abundance ratios. At medium scales these parameters are highly variable. At small scales the magnetic field magnitude plays a major role in defining structures with high plasma beta and isotropic suprathermal electron distributions. Other slow wind properties of interest include evidence for a boundary layer and the relationship of slow wind structures to the heliospheric current sheet (HCS). Against expectations, a relatively large fraction of spacecraft passages through the slow wind lack HCS crossings. Seen as a whole, the observed properties of the slow wind suggest a synthesis view with both steady-state and transient aspects.

Crooker, N.

2008-12-01

142

Latitudinal Variation of Solar Wind Velocity  

NASA Astrophysics Data System (ADS)

Single station solar wind velocity measurements using the Ooty Radio Telescope (ORT) in India (operating at 327 MHz) are reported for the period August 1992 to August 1993. Interplanetary scintillation (IPS) observations on a large number of compact radio sources covering a latitudinal range of ±80° were used to derive solar wind velocities using the method of fitting a power law model to the observed IPS spectra. The data shows a velocity versus heliographic latitude pattern which is similar to that reported by Rickett and Coles (1991) for the 1981 1982 period. However, the average of the measured equatorial velocities are higher, being about 470 km s-1 compared to their value of 400 km s-1. The distribution of electron density variations (?N e ) between 50R? and 90R? was also determined and it was found that ?N e was about 30% less at the poles as compared to the equator.

Ananthakrishnan, S.; Balasubramanian, V.; Janardhan, P.

1995-04-01

143

Equatorwards Expansion of Unperturbed, High-Latitude Fast Solar Wind  

NASA Astrophysics Data System (ADS)

We use dual-site radio observations of interplanetary scintillation (IPS) with extremely long baselines (ELB) to examine meridional flow characteristics of the ambient fast solar wind at plane-of-sky heliocentric distances of 24 - 85 solar radii ( R ?). Our results demonstrate an equatorwards deviation of 3 - 4? in the bulk fast solar wind flow direction over both northern and southern solar hemispheres during different times in the declining phase of Solar Cycle 23.

Dorrian, G. D.; Breen, A. R.; Fallows, R. A.; Bisi, M. M.

2013-07-01

144

Velocity shear generation of solar wind turbulence  

Microsoft Academic Search

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

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

1992-01-01

145

Velocity shear generation of solar wind turbulence  

Microsoft Academic Search

The authors use a two-dimensional, incompressible MHD spectral code to establish 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 ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to

D. Aaron Roberts; Melvyn L. Goldstein; S. Ghosh; W. H. Matthaeus

1992-01-01

146

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

147

Turbulence in the solar wind: Kinetic effects  

SciTech Connect

Nonlinear processes in the solar wind drive a turbulent cascade of energy from large to small scales. Many aspects of this turbulent evolution can be described using fluid models, but near the wavelength of ion cyclotron waves, the spectrum steepens; evidence that the fluctuations are damped, heating the ambient plasma. Fluid models can be modified to approximate the physics of these kinetic processes by modifying the dissipation terms and by including extra terms which approximate some aspects of kinetic interactions.

Goldstein, Melvyn L. [NASA/Goddard Space Flight Center, Code 692, Laboratory for Extraterrestrial Physics, Greenbelt, Maryland 20771 (United States)

1996-07-20

148

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

149

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

150

Enabling Technologies for High Penetration of Wind and Solar Energy  

Microsoft Academic Search

High penetration of variable wind and solar electricity generation will require modifications to the electric power system. This work examines the impacts of variable generation, including uncertainty, ramp rate, ramp range, and potentially excess generation. Time-series simulations were performed in the Texas (ERCOT) grid where different mixes of wind, solar photovoltaic and concentrating solar power provide up to 80% of

Denholm

2011-01-01

151

The Solar Wind outside the Plane of the Ecliptic  

Microsoft Academic Search

The scintillation of radio sources caused by the interplanetary medium offers a means of studying the motion of the solar wind well away from the plane of the ecliptic, where direct measurements have so far been confined. Observations from a triangular arrangement of radio receivers (on 81.5 Mc\\/s) suggest that the solar wind is faster over the solar poles than

P. A. Dennison; A. Hewish

1967-01-01

152

Coronal roots of solar wind streams: 3-D MHD modeling  

Microsoft Academic Search

Weak (discontinuous) solutions of the 3-D MHD equations look like a promising tool to model the transonic solar wind with structural elements: current sheets, coronal plumes etc. Using the observational information about various coronal emissions one can include these structural elements into the 3-D MHD solar wind model by embedding the discontinuities of given type. Such 3-D MHD structured solar

Yu. V. Pisanko

1995-01-01

153

A model for the origin of solar wind stream interfaces  

Microsoft Academic Search

The basic variations in solar wind properties that have been observed at 'stream interfaces' near 1 AU are explained by a gas dynamic model in which a radially propagating stream, produced by a temperature variation in the solar envelope, steepens nonlinearly while moving through interplanetary space. The region thus identified with the stream interface separates the ambient solar wind from

A. J. Hundhausen; L. F. Burlaga

1975-01-01

154

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

Microsoft Academic Search

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

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

2010-01-01

155

Magnetospheric feedbacks in solar wind energy transfer  

NASA Astrophysics Data System (ADS)

The solar wind kinetic energy, fueling all dynamical processes within the near-Earth space, is extracted by a dynamo process at the magnetopause converting kinetic energy into magnetic energy. We investigate the magnetopause energy transfer both in small and large scales; using Cluster observations as well as a three-dimensional global magnetohydrodynamic (MHD) simulation GUMICS-4. In the simulation, the spatial distribution of the energy transfer exhibits a dependence on the interplanetary magnetic field (IMF) orientation, which is shown to agree with observational local estimates from Cluster spacecraft recordings. In both sythetic runs with artificial solar wind input as well as in reproductions of the observed solar wind we observe a "hysteresis" effect, where the magnetopause energy input stays enhanced longer than the traditional energy transfer proxies (e.g., epsilon) indicate. Specifically we focus in the simulation of a substorm sequence on Feb 18, 2004, during which an exceptional agreement between the simulation results and spacecraft recordings was observed on several orbits within the near-Earth space. In this event, we again observe the hysteresis effect and investigate the processes causing it at the magnetopause. We argue that since GUMICS-4 reproduces the observed signatures of the substorm sequence in question, the simulation results represent physical processes within the magnetosphere. We conclude that as the simulation energy input exhibits delays already at the magnetopause, the delays in the classical substorm loading - unloading cycle may be interpreted in a new light.

Palmroth, Minna; Pulkkinen, Tuija I.; Anekallu, Chandrasekhar R.; Honkonen, Ilja; Koskinen, Hannu E. J.; Lucek, Elizabeth A.; Dandouras, Iannis

2010-05-01

156

The spectrum of electron density fluctuations in the solar wind and its variations with solar wind speed  

Microsoft Academic Search

We describe simultaneous interplanetary scintillation (IPS) measurements for the solar distance range 70-185 solar radii made using the Ooty Radio Telescope and the Solar Terrestrial Environment Laboratory three-antenna system during the first half of the current solar cycle 22. These measurements have been used to establish the spectral characteristics of the electron density fluctuations in the solar wind, and we

P. K. Manoharan; M. Kojima; H. Misawa

1994-01-01

157

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

158

The Rising Phase of Solar Cycle 24: General Solar Wind, Large-Scale Solar Wind Structures, and Sector Asymmetry  

NASA Astrophysics Data System (ADS)

The solar polar field is presently nearing its reversal, suggesting the approach of solar maximum. However, the sunspot number, solar wind dynamic pressure, and IMF are still weak, similar to conditions in 1998 (the middle of last rising phase), suggesting a peculiar rising phase for Solar Cycle 24. In this presentation, following the study of solar minimum 23/24 in Jian et al. (2011), we first report the variations of solar wind parameters from the beginning of space era to present and compare the current rising phase with that of previous cycles. Secondly, based on our long-term study of large-scale solar wind structures, including interplanetary CMEs (ICMEs), stream interaction regions (SIRs), and their associated shocks at 1 AU from 1995 to present, we compare their properties in this rising phase with those of Cycle 23 and study their possible influence on geomagnetic activity. Thirdly, dividing the solar wind into positive (anti-sunward) and negative (sunward) sectors depending on the IMF polarity, we compare the solar wind parameters of the two polarity sectors from the beginning of Solar Cycle 21 to present. We note that an asymmetry between the two sectors exists for past cycles as reported by Hiltula and Mursula (2007) as well as Erdos and Balogh (2010). The sector asymmetry is more pronounced during the last solar minimum 23/24. Positive polarity solar wind is observed more often at 1 AU than negative polarity in Cycles 21 and 23 and less often in Cycle 22 and likely in this Cycle 24. Using the PFSS and MHD models, we can calculate the polarity distributions closer to the Sun, and they do not always agree with the observations. We closely examine several representative Carrington rotations to find out the reason. From 1-AU observations, the solar wind from the negative polarity sector (currently from northern hemisphere of the Sun) is found to be faster, hotter, and have a smaller proton density than the wind from the positive sector since 2009. This can affect the geomagnetic activity systematically. Comparing with the solar and coronal observations, we look for interpretations of the asymmetry.

Jian, L.; Russell, C. T.; Luhmann, J. G.; Riley, P.; Hoeksema, J. T.; Odstrcil, D.; Petrie, G. J.

2011-12-01

159

Variations of Strahl Properties With Fast and Slow Solar Wind  

NASA Astrophysics Data System (ADS)

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 bulk solar wind speed could provide some insight into the source, origin, and evolution of the strahl.

Nieves-Chinchilla, T.; Viñas, A. F.; Goldstein, M. L.; Gurgiolo, C.

2008-12-01

160

Comparison of the solar wind energy input to the magnetosphere measured by Wind and Interball-1  

Microsoft Academic Search

Timely solar wind measurements are indispensable for space weather forecasts and magnetospheric studies, but solar wind variations detected by a distant spacecraft might be different from those actually hitting Earth's magnetosphere. To determine how important these differences can be for geophysical applications, we compared energy input to the magnetosphere which was simultaneously measured by the Wind and Interball-1 spacecraft at

A. A. Petrukovich; S. I. Klimov; A. Lazarus; R. P Lepping

2001-01-01

161

Abundance of solar wind magnesium isotopes determined with WIND/MASS  

NASA Astrophysics Data System (ADS)

We present first results of the abundance ratios of Mg isotopes in the solar wind using the high resolution mass spectrometer on the WIND spacecraft. The isotopic composition of Mg in the solar wind is consistent with terrestrial values. Our preliminary result is 24Mg:25Mg:26Mg=(0.792+/-0.006):(0.095+/-0.005):(0.113+/-0.005).

Bochsler, P.; Gonin, M.; Sheldon, R. B.; Zurbuchen, Th.; Gloeckler, G.; Hamilton, D. C.; Collier, M. R.; Hovestadt, D.

1996-07-01

162

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

163

Fast Solar Wind Streams From the Sun to 1 AU During the Recent Solar Minimum  

NASA Astrophysics Data System (ADS)

The origin and evolution of the solar wind from coronal holes is studied by characterizing the physical properties of the solar wind plasma (temperature, density, outflow velocity, and composition) with multi-spacecraft and ground-based observations. PFSS modeling is also used to confirm interpretation of the source regions and in wind-stream boundary mapping. We discuss the results for the fast solar wind from polar and low-latitude coronal-hole wind streams. We also compare the characteristics of these wind streams with results from the previous solar minimum.

Miralles, M. P.; Simunac, K. D.; Strachan, L.; Galvin, A. B.; Landi, E.; Lee, C. O.; Luhmann, J. G.; McIntosh, P. S.

2010-12-01

164

First determination of the silicon isotopic composition of the solar wind: WIND/MASS results  

NASA Astrophysics Data System (ADS)

Silicon is a common material in the solar system. For instance, Si accounts for about 10% of the material in primitive meteorites (CI chondrites). Since silicon is a refractory element, we expect the meteoritic isotopic composition to be very similar to that of the Sun. The isotopic composition of Si in meteorites is well known and varies little. Thus the three stable isotopes of Si may serve as powerful indicators to test fractionation of isotopes in the transition from the solar atmosphere into the solar wind. We present, for the first time, measurements of the isotopic composition of Si in the solar wind. The data were obtained with the MASS instrument aboard the WIND spacecraft and accumulated in exceedingly cold and slow wind. Such wind is often associated with large superradial expansion factors and with current sheet crossings which in turn are associated with the most efficient isotopic fractionation processes in the solar wind acceleration region. We detect little or no isotopic fractionation between the solar surface assumed to be of meteoritic composition and the solar wind. This constrains solar wind acceleration models and puts stringent limits on possible secular changes in the isotopic composition of the outer solar convective zone, the solar atmosphere, and the solar wind.

Wimmer-Schweingruber, Robert F.; Bochsler, Peter; Kern, Olivier; Gloeckler, George; Hamilton, Douglas C.

1998-09-01

165

Coupling of the solar wind to the magnetosphere  

NASA Astrophysics Data System (ADS)

Solar wind-magnetosphere coupling is considered in the context of four major questions. The first of these questions is concerned with the process of solar wind plasma entry. The processes of energy and momentum transfer from the solar wind to the magnetosphere comprise the focus of the second question. The third question deals with the physics of magnetospheric boundary layers, specifically their role as generators, loads, and plasma transport regions. The final question concerns the global magnetohydrodynamics that characterize the magnetosphere for the various coupling processes and as functions of solar wind parameters.

1984-06-01

166

Flux tubes in the solar wind from Cluster measurements  

NASA Astrophysics Data System (ADS)

Recent studies of solar wind turbulence suggest that tangential discontinuities in the interplanetary medium can introduce significant intermittency and these discontinuities may be a natural manifestation of flux-tube-like structures in the solar wind. Because the existence of these flux tubes can affect our understanding of the solar wind MHD turbulence, it is necessary that we verify their existence and are able to identify them individually. Using the magnetic field data from FGM instrument onboard Cluster spacecraft, we examine the existence of flux tubes in the solar wind. Cluster/FGM has a high time resolution of magnetic field data and the orbits of Cluster also traverse through various dynamic regions, including the solar wind, Earth's magnetosheath and magnetotail, making Cluster's dataset ideal for studying the differences between, for example, solar wind turbulence and those inside the magnetosphere (e.g. turbulence in plasma sheet). Using a recent data analysis by Li, [2007a,b], we show that flux tubes exist in the solar wind, but not inside Earth's magnetotial. The existence of flux-tube-like structures in the solar wind implies that current studies of solar wind MHD turbulence must be carefully re-examined because these flux tubes will inneviatablly cause intermittency and affect turbulence power spectrum.

Li, G.; Lee, E.; Parks, G.

2007-12-01

167

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

Microsoft Academic Search

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

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

1995-01-01

168

Improved forecasts of solar wind parameters using the Kalman filter  

Microsoft Academic Search

A Kalman filter technique is applied to an empirical solar wind forecast modelWith KF, the forecasting errors decrease and the applicability period increasesKF grants to the model some robustness againt transient solar activity

M. E. Innocenti; G. Lapenta; B. Vrsnak; F. Crespon; C. Skandrani; M. Temmer; A. Veronig; L. Bettarini; S. Markidis; M. Skender

2011-01-01

169

Numerical modeling of transient phenomena in the distant solar wind  

NASA Astrophysics Data System (ADS)

The solar wind is essentially time dependent. There are many timescales of interest: the 11 year period of solar activity, the 26 day solar rotation period, and shorter scales related to other unsteady phenomena originating at the Sun. In this study we analyze the behavior of the supersonic solar wind taking into account the formation of corotating interaction regions (CIR) due to the fast and slow solar wind interactions. The solution obtained is used as a starting point to study a three-dimensional evolution of 2000 global merged interaction region (GMIR) and the 2003 Halloween event in the distant heliosphere. The results are compared with the Voyagers data.

Borovikov, S.; Pogorelov, N. V.; Hu, Q.; Burlaga, L. F.; Zank, G. P.

2009-12-01

170

An Improved Solar Wind Electron Density Model for Pulsar Timing  

NASA Astrophysics Data System (ADS)

Variations in the solar wind density introduce variable delays into pulsar timing observations. Current pulsar timing analysis programs only implement simple models of the solar wind, which not only limit the timing accuracy, but can also affect measurements of pulsar rotational, astrometric, and orbital parameters. We describe a new model of the solar wind electron density content which uses observations from the Wilcox Solar Observatory of the solar magnetic field. We have implemented this model into the TEMPO2 pulsar timing package. We show that this model is more accurate than previous models and that these corrections are necessary for high-precision pulsar timing applications.

You, X. P.; Hobbs, G. B.; Coles, W. A.; Manchester, R. N.; Han, J. L.

2007-12-01

171

Global distribution of the solar wind during solar cycle 23: ACE observations  

NASA Astrophysics Data System (ADS)

The composition of the solar wind can be used to determine its origin at the Sun; e.g., solar wind from coronal holes has demonstrably lower charge states than solar wind of other origins. The O 7+/O 6+ ratio as measured by Advanced Composition Explorer (ACE) during 1998-2008 is used to divide the solar wind into three categories: non-transient solar wind from coronal holes (hereafter referred to as CHW); non-transient solar wind that originates from outside of coronal holes (hereafter referred to as NCHW), and solar wind associated with transient interplanetary coronal mass ejections (ICMEs). The global distribution of the solar wind relative to the Heliospheric Current Sheet (HCS), as specified by a Potential-Field-Source-Surface model, is then determined. The solar wind from outside of coronal holes is found to originate from a band of about 40° in width about the HCS during solar maximum conditions, and a much smaller band of < 17° during solar minimum. These results are consistent with models for the global transport of the solar magnetic field during the solar cycle, and they are consistent with earlier global flow structure determinations based upon velocity alone.

Zhao, L.; Zurbuchen, T. H.; Fisk, L. A.

2009-07-01

172

Suprathermal Tails in Solar Wind Oxygen and Iron  

NASA Astrophysics Data System (ADS)

High speed suprathermal tails with a fixed energy spectrum have been observed in solar wind H and He2+, as well as in He+ pickup ions (e.g. Gloeckler et al., 2007). These tails appear to have a persistent and constant power law energy spectrum, unchanged in a variety of solar conditions. The presence of the tails have implications for particle injection into the interplanetary shock acceleration process. The suprathermal tails of solar wind Fe and O have been investigated with the STEREO/PLASTIC mass spectrometer. The energy spectra of solar wind O and Fe will be presented for periods of slow and fast solar wind. Variations in energy spectra are observed in both species at speeds up to 1.8 times the solar wind speed.

Popecki, M. A.; Galvin, A.; Klecker, B.; Kucharek, H.; Kistler, L.; Bochsler, P.; Blush, L.; Möbius, E.

2008-12-01

173

Effect of Flow-Tube Geometry on Solar Wind Properties  

NASA Astrophysics Data System (ADS)

A mathematical description of the solar wind flow-tube geometry is proposed. The expansion factor of the flow tube f(r) (= a/r 2, r is the heliocentric distance and a is the flow-tube cross-section area)increases monotonically from 1 at the coronal base to m at r c, and approaches its asymptotic value f ? nearly in a width of2? c . The flow tube with f m =f infin is demonstrated to be approximately equivalent to that given by Kopp and Holzer (1976) for the fast solar wind, and it presumably represents slow wind tubes as f m is substantially larger than f ?. In terms of an Alfvén wave-driven solar wind model, the effect of the flow-tube geometry on solar wind properties is examined. It is found that with the same flow conditions at the coronal base an expansion factor which increases monotonically with the radial distance results in a fast solar wind solution, whereas a flow tube which undergoes an expansion-contraction-reexpansion process creates a slow solar wind solution. Among the four flow-tube parameters the maximum expansion factor f m has the strongest effect, and the associated Laval-nozzle formed by the contraction and reexpansion of theflow tube plays a crucial role in determining solar wind properties. It is suggested that one must take the effect of the flow-tube geometry into account while constructing reasonable flow-tube models for the slow solar wind.

Chen, Y.; Hu, Y. Q.

2002-10-01

174

Signatures of shock drivers in the solar wind and their dependence on the solar source location  

Microsoft Academic Search

Solar wind and energetic ion observations following 40 interplanetary shocks with well-established solar source locations have been examined in order to determine whether signatures characteristic of the coronal material forming the shock driver are present. The signatures considered include magnetic-field-aligned bidirectional ion flows observed by the ISEE 3 and IMP 8 spacecraft; bidirectional solar wind electron heat fluxes; solar wind

I. G. Richardson; H. V. Cane

1993-01-01

175

Solar wind: The solar wind and the Sun-Earth link  

Microsoft Academic Search

The solar wind fills the space between the Sun and its planets, shapes the planetary environments and the heliosphere, and comes to a screeching halt at the heliopause, the boundary with the interstellar medium. This tenuous medium is a fertile environment for exotic plasma processes, most of which are not fully understood. It also holds the intimate secrets of the

Shadia Rifia Habbal; Richard Woo

2004-01-01

176

Solar wind dependence of energy coupling between solar wind and magnetosphere during intense northward IMFs  

NASA Astrophysics Data System (ADS)

We statistically study the solar wind dependence of the magnetospheric activities during intense northward interplanetary magnetic fields (IMFs) events (Bz>10 nT, last over 3 h). It was found that the energy coupling between solar wind and magnetosphere during intense northward IMFs was mainly controlled by solar wind velocity and IMF clock angle (?). A northward IMF coupling function was derived based on the dimensional analysis and quantitative analysis of the solar wind parameters and the geomagnetic indices. It was shown that when ?>˜45°, the energy input increases obviously as ? increases. Most importantly, it was also found that the relative importance between the viscous interaction and the IMF ?By? effect in controlling the energy input into the magnetosphere during intense northward IMFs mainly depends on IMF clock angle. The viscous interaction will outweigh the IMF ?By? effect in the northward IMF events with ?<˜75°. In contrast, for those northward IMF events with ?>˜75°, the IMF ?By? effect may be more important than the viscous interaction.

Luo, H.; Chen, G. X.; Du, A. M.; Xu, W. Y.

2013-05-01

177

Spectroscopic measurements of solar wind generation  

NASA Astrophysics Data System (ADS)

Spectroscopically observable quantities are described which are sensitive to the primary plasma parameters of the solar wind's source region. The method is discussed in which those observable quantities are used as constraints in the construction of empirical models of various coronal structures. Simulated observations are used to examine the fractional contributions to observed spectral intensities from coronal structures of interest which co-exist with other coronal structures along simulated lines-of-sight. The sensitivity of spectroscopic observables to the physical parameters within each of those structures is discussed.

Kohl, J. L.; Withbroe, G. L.; Zapata, C. A.; Noci, G.

1983-11-01

178

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.

Wang, Chia-Gee

1980-01-01

179

The floor in the solar wind: status report  

NASA Astrophysics Data System (ADS)

Cliver & Ling (2010) recently suggested that the solar wind had a floor or ground-state magnetic field strength at Earth of ~2.8 nT and that the source of the field was the slow solar wind. This picture has recently been given impetus by the evidence presented by Schrijver et al. (2011) that the Sun has a minimal magnetic state that was approached globally in 2009, a year in which Earth was imbedded in slow solar wind ~70% of the time. A precursor relation between the solar dipole field strength at solar minimum and the peak sunspot number (SSN MAX ) of the subsequent 11-yr cycle suggests that during Maunder-type minima (when SSN MAX was ~0), the solar polar field strength approaches zero - indicating weak or absent polar coronal holes and an increase to nearly ~100% in the time that Earth spends in slow solar wind.

Cliver, E. W.

2012-07-01

180

ELECTRON TRANSPORT IN THE FAST SOLAR WIND  

SciTech Connect

The electron velocity distribution function is studied in the extended solar corona above coronal holes (i.e., the inner part of the fast solar wind) from the highly collisional corona close to the Sun to the weakly collisional regions farther out. The electron kinetic equation is solved with a finite-element method in velocity space using a linearized Fokker-Planck collision operator. The ion density and temperature profiles are assumed to be known and the electric field and electron temperature are determined self-consistently. The results show quantitatively how much lower the electron heat flux and the thermal force are than predicted by high-collisionality theory. The sensitivity of the particle and heat fluxes to the assumed ion temperature profile and the applied boundary condition at the boundary far from the Sun is also studied.

Smith, H. M.; Marsch, E. [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Strasse 2, 37191 Katlenburg-Lindau (Germany); Helander, P., E-mail: hakan.smith@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, Wendelsteinstrasse 1, 17491 Greifswald (Germany)

2012-07-01

181

Solar Wind Eight: Proceedings of the Eighth International Solar Wind Conference. Proceedings  

SciTech Connect

These proceedings represent papers presented at the eighth international solar wind conference held at the Dana Point Resort, California. The conference was sponsored by the National Aeronautics and Space Administration(NASA), the National Science Foundation(NSF) and the Committee on space Research (COSPAR). The proceedings from this conference reflected the state of the art of solar wind research: its origin at the sun, the transport through the solar system, and its ultimate fate at the heliocentric boundaries. There were one hundred and seventy eight papers presented and nineteen papers for which the research was sponsored by the US Department of Energy have been abstracted for the Energy Science and Technology database.(AIP)

Winterhalter, D. [Jet Propulsion Laboratory, California Institute of Technology (United States); Gosling, J.T. [Los Alamos National Laboratory (United States); Habbal, S.R. [Harvard-Smithsonian Center for Astrophysics (United States); Kurth, W.S. [University of Iowa (United States); Neugebauer, M. [Jet Propulsion Laboratory, California Institute of Technology (United States)

1997-06-01

182

Magnetospheric modes and solar wind energy coupling efficiency  

Microsoft Academic Search

Using observations and two different global MHD simulations, we demonstrate that the solar wind speed controls the magnetospheric response such that the higher the speed, the more dynamic and irregular is the magnetospheric response. For similar level of driving solar wind electric field, the magnetospheric modes can be organized in terms of speed: Low speed produces steady convection events, intermediate

T. I. Pulkkinen; M. Palmroth; H. E. J. Koskinen; T. V. Laitinen; C. C. Goodrich; V. G. Merkin; J. G. Lyon

2010-01-01

183

Structure of international research collaboration in wind and solar energy  

Microsoft Academic Search

Climate change is a common global issue. Advanced technologies to tackle the problem are spread throughout the world. Among varies kind of energy sources, wind power and solar cell are the most promising technologies for green growth. This paper will first aim to identify the structure of international research collaboration in wind power and solar cell. Secondly, this paper will

Ichiro Sakata; Hajime Sasaki; Toshihiro Inoue

2011-01-01

184

The acceleration of minor ion species in the solar wind  

Microsoft Academic Search

This paper provides a comprehensive analysis of the dynamics of the flow of minor ion species in the solar wind under the combined influences of gravity, Coulomb friction (with protons), rotational forces (arising from the Sun's rotation and the interplanetary spiral magnetic field) and wave forces (induced in the minor ion flow by Alfvén waves propagating in the solar wind).

J. F. McKenzie; W. H. IP; W. I. Axford

1979-01-01

185

Ionospheric and Magnetospheric Configurations During Extreme Solar Wind Conditions  

Microsoft Academic Search

Using the University of Michigan MHD code, we have simulated the magnetospheric and ionospheric configuration for a number of different extreme solar wind and interplanetary magnetic field conditions. We have calculated magnetopause standoff distances and bowshock locations for a wide range of solar wind and IMF conditions, and compare these with data-derived models. We examine the saturation of the cross

A. Ridley; T. Gombosi; D. de Zeeuw; K. Powell

2002-01-01

186

On the Solar wind Origin Problem and its Evolutionary Solution  

Microsoft Academic Search

We demonstrate that the solar wind origin problem can have only one evolutionary solution. It is not known when and how the solar wind started to blow, but there are evidences that it existed on the geological time scale and will continue to exist even during crossing of dense galactic arms by the Sun in future. The Hayashi phase or

I. Veselovsky

2008-01-01

187

Model for Proton Heating in the Solar Wind.  

National Technical Information Service (NTIS)

Quasilinear theory is used to calculate the power dissipated via obliquely propagating Alfven waves to heat the solar wind protons. This shows good agreement with the power which needs to be supplied to the solar wind protons as deduced from Helios observ...

H. A. Shah L. Iess M. Dobrowolny

1985-01-01

188

Solar wind dependence of the Pc1 wave activity  

Microsoft Academic Search

When we try to understand the origin of Pc1 geomagnetic pulsations, which are the ULF electromagnetic waves in the frequency range between 0.2 and 5 Hz, we normally think of such pulsations as a result of interaction of the solar wind with the Earth's magnetosphere. In other words, the solar wind is considered as a prime cause which leads to

A. Guglielmi; J. Kangas; J. Kultima; A. Potapov

2002-01-01

189

Energy costs in combined solar-wind power plants  

Microsoft Academic Search

A method for appraising the energy cost for a combined solar-wind power plant (SWPP) is described and assessed. It is shown\\u000a that the best way to reduce the energy cost is to increase the generation time and provide the optimum combination of wind\\u000a and solar components.

Sh. I. Klychev; M. M. Mukhammadiyev; O. Kh. Nizomov; K. D. Potayenko

2008-01-01

190

Energetic Solar Wind Ions As Probes Of Saturn's Magnetosphere  

NASA Astrophysics Data System (ADS)

Energetic solar wind ions can be used as tracers of solar wind particle entry into and interaction with planetary magnetospheric environments. We use Cassini's MIMI/CHEMS Charge-Energy-Mass Spectrometer to investigate the solar wind origin He+2 and high charge state O?+6 and Fe?+7 ions observed in and near Saturn's magnetosphere in the range ~3-220 keV/e. He+2 being a major solar wind component is measured throughout most of the magnetosphere, while O?+6 and Fe?+7, lesser solar wind components than He+2, are abundant enough to often present useful flux levels therein. O?+6 and Fe?+7 are valuable in that they experience charge exchange with Saturn's neutral populations. Low oxygen charge states O?+3 originate in Saturn's magnetosphere from Saturn's moons and rings. Intermediate charge exchange products O+4 and O+5 are produced in the magnetosphere by charge exchange down from solar wind O?+6 and up from magnetospheric O?+3. All oxygen charge states exhibit variable flux levels from orbit to orbit, reflecting variations in the solar wind and magnetospheric sources and, possibly, the magnetospheric neutral population. We will survey the O?+4 and Fe?+7 ions observed in and near the magnetosphere from the 2004-2006 equatorial orbits to assess their usefulness in investigating both charge exchange in and the solar wind interaction with Saturn's magnetosphere.

Christon, S. P.; Hamilton, D. C.; Mitchell, D. G.; Krimigis, S. M.

2009-12-01

191

Western Wind and Solar Integration Study: Executive Summary.  

National Technical Information Service (NTIS)

The focus of the Western Wind and Solar Integration Study (WWSIS) is to investigate the operational impact of up to 35% energy penetration of wind, photovoltaics (PVs), and concentrating solar power (CSP) on the power system operated by the WestConnect gr...

2010-01-01

192

The solar wind as we know it today  

Microsoft Academic Search

The first evidence of the solar wind surfaced after comet tail deflections were observed 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 indicated the existence of an outflow of ionized gas from the Sun

B. E. Goldstein

1993-01-01

193

Wind and radiant solar energy for drying fruits and vegetables  

Microsoft Academic Search

The combination of wind with radiant solar energy for drying fruits and vegetables can help promote conservation of food and nonrenewable energy resources. Low-cost, small-scale solar dryers have been developed with the potential for developing larger dryers. These dryers depend on natural air convection to remove moisture. Designing the dryers to incorporate natural wind currents, providing forced air circulation, could

C. J. Jr. Wagner; R. L. Coleman; R. E. Berry

1981-01-01

194

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

195

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

196

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

197

Spatial Correlation of Solar Wind Fluctuations and Their Solar Cycle Dependence  

Microsoft Academic Search

We investigate the spatial correlation properties of the solar wind in the ecliptic at 1 AU using simultaneous in situ observations by the Advanced Composition Explorer and Wind spacecraft. We present the first direct study of the spatial correlation length scale lambda of fluctuations in the solar wind ion density rho, and find it to be smaller than that of

R. T. Wicks; S. C. Chapman; R. O. Dendy

2009-01-01

198

The Electrodynamics of the Solar Wind Interaction with Venus  

NASA Astrophysics Data System (ADS)

Venus has a thick atmosphere whose upper reaches are ionized by solar EUV. The temperature and density of this ionosphere provide sufficient pressure that, at solar maximum for normal solar wind pressures, the solar wind is deflected at altitudes far above the region of significant ion-neutral collisions. Hence when the interplanetary field changes, a current is induced at the ionopause that excludes the magnetic field from the ionosphere. A magnetic barrier of magnetic field draped around the ionosphere builds up and forms the obstacle to the solar wind flow. Since the size of the Venus obstacle vastly exceeds that of the ion-gyro motion, a bow shock forms that slows, heats, and deflects the solar wind plasma. This interaction is the epitome of the induced magnetosphere. At times though, the solar wind pressure is too strong to be stood off by the ionosphere, and the ionopause drops to collisional altitudes. At this point, the ionosphere becomes magnetized throughout. Venus also has an H and O exosphere that extends into the solar wind. These can lead to the occurrence of cometary processes like mass pickup and deceleration of the flow. In short, the solar wind interaction with Venus has many facets and is sufficiently complex to continue to fuel new discoveries and a little controversy.

Russell, C. T.; Ma, Y. J.; Luhman, J. G.

2010-05-01

199

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

200

Velocity shear generation of solar wind turbulence  

SciTech Connect

The authors use a two-dimensional, incompressible MHD spectral code to establish 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 ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find 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. While the fluctuations thus produced are not Alfvenic, they are nearly equipartitioned between magnetic and kinetic energy. The authors report simulations with Alfvenic fluctuations at high wave numbers, both with and without shear layers and find that it is the low cross helicity at low wave numbers that is critical to the cross helicity evolution, rather than the geometry of the flow or the dominance of kinetic energy at large scales. The fluctuations produced by shear effects are shown to evolve similarly but more slowly in the presence of a larger mean field and to be anisotropic with a preferred direction of spectral transfer perpendicular to the mean field. The evolution found is similar to that seen in some other simulations of HMD turbulence, and thus seems in many respects to be an instance of a more generic turbulent evolution rather than due to specific conditions in the solar wind. 75 refs., 18 figs.

Roberts, D.A.; Goldstein, M.L.; Ghosh, S. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Matthaeus, W.H. [Univ. of Delaware, Newark, DE (United States)

1992-11-01

201

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

202

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

203

Short-scale Variations of the Solar Wind Helium Abundance  

NASA Astrophysics Data System (ADS)

Abrupt changes of the relative He abundance in the solar wind are usually attributed to encounters with boundaries dividing solar wind streams from different sources in the solar corona. This paper presents a systematic study of fast variations of the He abundance that supports the idea that a majority of these variations on short timescales (3-30 s) are generated by in-transit turbulence that is probably driven by the speed difference between the ion species. This turbulence contributes to the solar wind heating and leads to a correlation of the temperature with He abundance.

Šafránková, J.; N?me?ek, Z.; Cagaš, P.; P?ech, L.; Pavl?, J.; Zastenker, G. N.; Riazantseva, M. O.; Koloskova, I. V.

2013-11-01

204

A study of the composition of the solar corona and solar wind  

Microsoft Academic Search

Effects of diffusion on the composition of the solar corona and solar wind have been examined. Multi-component diffusion equations have been solved simultaneously in attempts to account for the flux of He and heavier elements in the solar wind. Large enhancements of these elements at the base of the assumed isothermal corona appear to be required to give observed fluxes.

M. P. Nakada

1970-01-01

205

Combined solar and wind powered generator with spiral surface pattern  

Microsoft Academic Search

This patent describes a combination solar and wind power generator. It includes a wind generator, responsive to the flow of air currents, for converting mechanical energy into electrical energy; the wind generator including a plurality of air engaging vanes having at least first and second surfaces, the first and second surfaces forming a cavity internal to the air engaging vanes,

Hickey

1991-01-01

206

The Importance of Using Continuous Solar Inputs in 3D Models to Simulate the Distant Solar Wind and Heliosheath  

Microsoft Academic Search

Solar transients and the background solar wind give rise to asymmetries in the distant solar wind and heliosheath. Entering continuous solar data into time-dependent, 3D models originating at the Sun is crucial for accurately characterizing the distant solar wind and the heliosheath. We employ our time-dependent, 3D MHD (magnetohydrodynamic) model the HHMS - the Hybrid Heliospheric Modeling System - to

D. S. Intriligator; T. Detman; W. Sun; A. Rees; T. S. Horbury; C. Deehr; M. Dryer; C. D. Fry; J. Intriligator

2007-01-01

207

On tracing the origins of the solar wind  

Microsoft Academic Search

Since the 1960s, in situ observations have shown that the solar wind is comprised of two distinct states: slow (300-550 km\\/s) and fast (600-800 km\\/s). Temperature, density, and compositional variations between the two suggest different sources for the fast and slow solar wind. Several theories have been proposed to explain the speed and the compositional differences between the two wind

Sarah Lynn McGregor

2011-01-01

208

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

Microsoft Academic Search

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

Wei Zhou

2008-01-01

209

A new view of solar wind structures: Combined interplanetary scintillation and STEREO HI studies of the inner solar wind  

Microsoft Academic Search

The heliospheric imagers (HI) on the STEREO A and B spacecraft are now providing the first continuous, detailed images of structures in the interplanetary solar wind. When combined with simultaneous radio measurements of interplanetary scintillation (IPS), STEREO images allow the structure of the solar wind to be studied with much greater certainty than has been possible before. The STEREO HI

R. A. Fallows; A. R. Breen; G. D. Dorrian; I. Whittaker; M. Grande

2009-01-01

210

Development of three-dimensional magnetohydrodynamic model for solar corona and solar wind simulation  

NASA Astrophysics Data System (ADS)

Propagation of coronal mass ejections from solar surface to the Earth magnetosphere is strongly influenced by the conditions in solar corona and ambient solar wind. Thus, reliable simulation of the background solar wind is the primary task toward the development of numerical model for the transient events. In this paper we introduce a new numerical model which has been specifically designed for numerical study of the solar corona and ambient solar wind. This model is based on our recently developed three-dimensional Spherical Coordinate Adaptive Magneto-Hydro-Dynamic (MHD) code (SCA-MHD-3D) [Yuan et al., 2009]. Modifications has been done to include the observed magnetic field at the photosphere as inner boundary conditions. The energy source term together with reduced plasma gamma are used in the nonlinear MHD equations in order to simulate the solar wind acceleration from subsonic speed at solar surface to supersonic speed at the inter-heliosphere region, and the absorbing boundary conditions are used at the solar surface. This model has been applied to simulate the background solar wind condition for several different solar rotations, and comparison between the observation and model output have shown that it reproduces many features of solar wind, including open and closed magnetic fields, fast and slow solar wind speed, sector boundaries, etc.

Yuan, Xingqiu; Trichtchenko, Larisa; Boteler, David

211

Parametric study of hybrid (wind + solar + diesel) power generating systems  

Microsoft Academic Search

The combined utilization of renewables such as solar and wind energy is becoming increasingly attractive and is being widely used for substitution of oil-produced energy, and eventually to reduce air pollution. In the present investigation, hourly wind-speed and solar radiation measurements made at the solar radiation and meteorological monitoring station, Dhahran (26°32?N, 50°13?E), Saudi Arabia, have been analyzed to study

M. A. Elhadidy; S. M. Shaahid

2000-01-01

212

Coronal roots of solar wind streams: 3-D MHD modeling  

NASA Astrophysics Data System (ADS)

Weak (discontinuous) solutions of the 3-D MHD equations look like a promising tool to model the transonic solar wind with structural elements: current sheets, coronal plumes etc. Using the observational information about various coronal emissions one can include these structural elements into the 3-D MHD solar wind model by embedding the discontinuities of given type. Such 3-D MHD structured solar wind is calculated self-consistently: variants are examined via numerical experiments. In particular, the behavior of coronal plumes in the transonic solar wind flow, is modeled. The input information for numerical modeling (for example, the magnetic field map at the very base of the solar corona) can be adjusted so that fast stream arises over the center of the coronal hole, over the coronal hole boundaries and, even, over the region with closed magnetic topology. 3-D MHD equations have the analytical solution which can serve as a model of supersonic trans-alfvenic solar wind in the (5-20) solar radii heliocentric distance interval. The transverse, nonradial total (gas + magnetic field) pressure balance in the flow is the corner-stone of this solution. The solution describes the filamentation (ray-like structure of the solar corona) and streaming (formation of high-speed streams with velocities up to 800 km/sec) as a consequence of the magnetic field spatial inhomogeneous structure and trans-alfvenic character of the flow. The magnetic field works in the model as a 'controller' for the solar wind streaming and filamentation.

Pisanko, Yu. V.

1995-06-01

213

Next-Generation Model of the Corona and Solar Wind.  

National Technical Information Service (NTIS)

A central goal of solar and space physics is to understand the influence of the sun and its activity on the heliosphere, particularly the space environment near the Earth. A quantitative description of the ambient solar corona and solar wind is key to und...

J. A. Linker

2011-01-01

214

Solar semidiurnal tidal wind oscillations above the CART site  

NASA Astrophysics Data System (ADS)

Harmonic analysis of wintertime data from 915- and 404-MHz radar wind profilers at four sites in North America has identified coherent semidiurnal wind oscillations through the entire depth of the troposphere. These winds are readily apparent above the CART site, as evidenced from analyses of data from the Haviland, KS, radar profiler. The characteristics of this wind system match the characteristics of solar semidiurnal atmospheric tides, as predicted by a simple dynamic model.

Whiteman, C. D.; Bian, X.

1995-03-01

215

COMPOSITION OF THE SOLAR CORONA, SOLAR WIND, AND SOLAR ENERGETIC PARTICLES  

SciTech Connect

Along with temperature and density, the elemental abundance is a basic parameter required by astronomers to understand and model any physical system. The abundances of the solar corona are known to differ from those of the solar photosphere via a mechanism related to the first ionization potential of the element, but the normalization of these values with respect to hydrogen is challenging. Here, we show that the values used by solar physicists for over a decade and currently referred to as the 'coronal abundances' do not agree with the data themselves. As a result, recent analysis and interpretation of solar data involving coronal abundances may need to be revised. We use observations from coronal spectroscopy, the solar wind, and solar energetic particles as well as the latest abundances of the solar photosphere to establish a new set of abundances that reflect our current understanding of the coronal plasma.

Schmelz, J. T. [Physics Department, University of Memphis, Memphis, TN 38152 (United States); Reames, D. V. [IPST, University of Maryland, College Park, MD 20742 (United States); Von Steiger, R. [ISSI, Hallerstrasse 6, 3012 Bern (Switzerland); Basu, S., E-mail: jschmelz@memphis.edu [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)

2012-08-10

216

Abundance variations in the solar wind  

NASA Astrophysics Data System (ADS)

The solar wind (SW) allows us to probe the solar material in situ, particularly its composition, without the need to fly a spacecraft to inhospitably small heliocentric distances. However, it turns out that this plasma source is biased with respect to the photosphere. Elements with a low first ionization potential (FIP) are overabundant by a factor of 3-5 relative to high-FIP elements in the slow SW, but only by a factor of 1.5-2 in the fast streams emanating from coronal holes. It is thus important to have a good understanding of this FIP fractionation effect, which operates between the photosphere and the corona. Such a theory may improve on our understanding of the solar atmosphere and SW acceleration. We present SW measurements, concentrating on results of the SWICS mass spectrometer on Ulysses, which is currently sampling the SW on a highly inclined orbit. IN 1992/93, Ulysses was traversing a recurrent high-speed stream once per solar rotation, alternating with slow SW, providing a unique opportunity to compare these two SW types. We find a strongly positive correlation for low- to high-FIP element ratios (such as Mg/O) with coronal temperature, which in turn is anticorrelated with the SW speed. The correlation of these three parameters -- one chromospheric, one coronal, and one from the SW -- points at a common cause for their variations, and provides a challenge to theorists to model these three domains in an unified approach. Further, abundance variations found in the SW from coronal streamers and in coronal mass ejections are presented and discussed. Finally, we address the question of abundance variations within the fast streams, looking for abundance gradients with heliographic latitude.

von Steiger, R.; Schweingruber, R. F. Wimmer; Geiss, J.; Gloeckler, G.

1995-07-01

217

Wind and radiant solar energy for drying fruits and vegetables  

SciTech Connect

The combination of wind with radiant solar energy for drying fruits and vegetables can help promote conservation of food and nonrenewable energy resources. Low-cost, small-scale solar dryers have been developed with the potential for developing larger dryers. These dryers depend on natural air convection to remove moisture. Designing the dryers to incorporate natural wind currents, providing forced air circulation, could increase drying rates. Preliminary studies to provide information for such designs included: (1) comparing drying tests with and without forced air circulation, (2) monitoring wind speeds on-site, and (3) testing wind collecting devices. Average wind speeds during solar periods were higher than air velocities from unassisted air convection in these small food dryers. Drying rates were increased by 6 to 11% when the natural convection dryer was provided with a small electric fan. Either of two wind collecting devices also could increase drying rates.

Wagner, C.J. Jr.; Coleman, R.L.; Berry, R.E.

1981-01-01

218

Suprathermal Tails in Solar Wind Oxygen and Iron  

NASA Astrophysics Data System (ADS)

High speed suprathermal tails with a fixed energy spectrum have been observed in solar wind H and He2+, as well as in He+ pickup ions (e.g. Gloeckler et al., 2007). These tails appear to have a persistent and constant power law energy spectrum, unchanged in a variety of solar conditions. The presence of the tails have implications for particle injection into the interplanetary shock acceleration process. The suprathermal tails of ions heavier than H and He may be investigated with the STEREO/PLASTIC mass spectrometer, for speeds up to several times the solar wind speed. The energy spectra of solar wind O and Fe are presented for periods of slow and fast solar wind. Variations in energy spectra will be discussed.

Popecki, M.; Galvin, A. B.; Kistler, L. M.; Klecker, B.; Bochsler, P.; Kucharek, H.; Blush, L.; Wimmer-Schweingruber, R. F.; Moebius, E.

2008-05-01

219

Interaction of ICMEs with the Solar Wind  

NASA Astrophysics Data System (ADS)

Interplanetary Coronal Mass Ejections (ICMEs) are formed of plasma and magnetic field launched from the Sun into the Solar Wind (SW). These coherent magnetic structures, frequently formed by a flux rope, interact strongly with the SW. This interaction is reviewed by comparing the results obtained from in situ observations and numerical simulations. Like fast ships in the ocean, fast ICMEs drive an extended shock in front. ICMEs expand in all directions while traveling away from the Sun, a sheath of SW plasma and magnetic field accumulates in front of the ICME, which partially reconnects with the ICME magnetic field. Furthermore, not only do ICMEs have a profound impact on the heliosphere, but the type of SW encountered by an ICME has an important impact on its evolution (e.g. increase of mass, global deceleration, lost of magnetic flux and helicity, distortion of the configuration).

Démoulin, Pascal

2010-03-01

220

Solar wind interaction with Jupiter's magnetosphere  

NASA Astrophysics Data System (ADS)

We suggest that the solar wind interaction with Jupiter's magnetosphere is dominated by viscous processes at the magnetopause boundary rather than a coherent reconnection-driven Dungey cycle. In particular, we show that shear flow-driven instabilities (e.g. Kelvin-Helmholtz) on Jupiter's magnetopheric flank can account for observations of: 1) flux tubes substantially depleted of energetic particles in regions outside of the plasmasheet, 2) anti-sunward flow in the dawnside ionosphere, 3) an aurorally active polar cap, and 4) a long magnetotail extending ~4 AU downstream. A preliminary analysis of the Kelvin-Helmholtz instability (KHI) as a function of local time will be presented along with initial two-dimensional hybrid code simulations of KHI at Jupiter's magnetopause boundary.

Delamere, P. A.; Bagenal, F.

2009-12-01

221

Solar wind fluctuations: Not your grandmother's turbulence  

NASA Astrophysics Data System (ADS)

For a while it seemed like a simple fluid-like, self-similar, Kolomogoroff cascade was the easy explanation for the nature and evolution of the majority of solar wind fluctuations. More recently we have found that the cascade is not driven by stirring at large scales; the velocity and magnetic spectra evolve differently with different "inertial ranges" in both slope (until far from the Sun) and wavenumber range (everywhere); anisotropy in both variances and spectral characteristics are the order of the day and are strongly scale dependent; and it is not clear what fraction of the fluctuations should be considered to be turbulent as opposed to, for example, convected structures. This paper gives a brief history and reviews some recent results in these areas.

Roberts, D. Aaron

2013-06-01

222

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

223

KOLMOGOROV VECTORIAL LAW FOR SOLAR WIND TURBULENCE  

SciTech Connect

We investigate a class of axisymmetric magnetohydrodynamic turbulence which satisfies the exact relation for third-order Elsaesser structure functions. Following the critical balance conjecture, we assume the existence of a power-law relation between correlation length scales along and transverse to the local mean magnetic field direction. The flow direction of the vector third-order moments F{sup {+-}} is then along axisymmetric concave/convex surfaces, the axis of symmetry being given by the mean magnetic field. Under this consideration, the vector F{sup {+-}} satisfies a simple Kolmogorov law which depends on the anisotropic parameter a{sup {+-}}, which measures the concavity of the surfaces. A comparison with recent in situ multispacecraft solar wind observations is made; it is concluded that the underlying turbulence is very likely convex. A discussion is given about the physical meaning of such an anisotropy.

Galtier, Sebastien, E-mail: sebastien.galtier@ias.u-psud.fr [Institut d'Astrophysique Spatiale, Univ Paris-Sud, bat. 121, 91405 Orsay (France)

2012-02-20

224

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

225

A feasibility study of a novel combined solar concentration\\/wind augmentation system  

Microsoft Academic Search

Solar energy and wind energy are two main renewable energy sources. Concentration of solar energy onto a smaller area may reduce the cost of PV modules and achieve high efficiency. On the other hand, wind augmentation allows lower trigger wind speed besides the reduced wind turbine size. For both solar concentration and wind augmentation, their tracking and support system may

Yuehong Su; Saffa B. Riffat; Tom Rogers; Hongfei Zheng; Hulin Huang

2010-01-01

226

Geomagnetic storms driven by ICME- and CIR-dominated solar wind  

Microsoft Academic Search

The interaction of the solar wind and the Earth's magnetosphere is complex and the phenomenology of the interaction is very different for solar wind dominated by interplanetary coronal mass ejections (ICMEs) compared to solar wind dominated by corotating interaction regions (CIRs). We perform a superposed epoch study of the effects of ICME- and CIR-dominated solar wind upon the storm-time plasma

M. H. Denton; J. E. Borovsky; R. M. Skoug; M. F. Thomsen; B. Lavraud; M. G. Henderson; R. L. McPherron; J. C. Zhang; M. W. Liemohn

2006-01-01

227

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

228

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

NASA Astrophysics Data System (ADS)

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.

1995-06-01

229

Residual Energy Spectrum of Solar Wind Turbulence  

NASA Astrophysics Data System (ADS)

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 ?r = -0.19 and mean Alfvén ratio of r 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.

2013-06-01

230

The Energy Spectra of Suprathermal Tails in Solar Wind Iron  

NASA Astrophysics Data System (ADS)

High speed suprathermal tails with a fixed energy spectrum have been observed in solar wind H+ and He2+, as well as in He+ pickup ions (e.g. Gloeckler et al., 2007). The presence of the tails have implications for particle injection into the interplanetary shock acceleration process. The suprathermal tails of solar wind Fe have been investigated with the STEREO/PLASTIC mass spectrometer. The energy spectra will be presented for periods of slow and fast solar wind, and for the entire STEREO mission.

Popecki, M. A.; Galvin, A.; Bochsler, P.; Klecker, B.; Kucharek, H.; Kistler, L.; Blush, L.; Moebius, E.

2009-05-01

231

Peculiarities of the MHD discontinuities interactions in the solar wind  

NASA Astrophysics Data System (ADS)

Different types of solar wind shock waves and rotational and contact discontinuity interactions are considered. It is shown that there are key parameters that describe the catastrophic reconstruction of the flow structure. The double shock wave ensemble's generation and the problem of magnetic field reconnection are discussed in the framework of the nonlinear MHD discontinuity interactions problem. The nonflare origin of some fast solar wind shock waves is indicated. The appearance of the slow shock wave in the result of nonshock discontinuities collision is underlined. The possibilities of the examination of the nonstationary solar wind phenomena with the help of the proposed method are shown.

Grib, S. A.; Pushkar', E. A.

232

MEASUREMENTS OF RAPID DENSITY FLUCTUATIONS IN THE SOLAR WIND  

SciTech Connect

The power spectrum of density fluctuations in the solar wind is inferred by tracking small timescale changes in the electron plasma frequency during periods of strong Langmuir wave activity. STEREO electric field waveform data are used to produce time profiles of plasma density from which the density power spectrum is derived. The power spectra obtained by this method extend the observed frequency range by an order of magnitude while remaining consistent with previous results near a few Hertz. Density power spectral indices are found to be organized by the angle between the local magnetic field and the solar wind direction, indicating significant anisotropy in solar wind high-frequency density turbulence.

Malaspina, D. M.; Ergun, R. E. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States); Kellogg, P. J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Bale, S. D., E-mail: David.Malaspina@colorado.ed [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2010-03-01

233

Ionospheric and Magnetospheric Configurations During Extreme Solar Wind Conditions  

NASA Astrophysics Data System (ADS)

Using the University of Michigan MHD code, we have simulated the magnetospheric and ionospheric configuration for a number of different extreme solar wind and interplanetary magnetic field conditions. We have calculated magnetopause standoff distances and bowshock locations for a wide range of solar wind and IMF conditions, and compare these with data-derived models. We examine the saturation of the cross polar cap potential for strongly negative IMF Bz and the influence of the solar wind dynamic pressure on the cross polar cap potential. Lastly, we present results from the 1859 Carrington Event superstorm.

Ridley, A.; Gombosi, T.; de Zeeuw, D.; Powell, K.

234

Wind loading on solar concentrators: some general considerations  

SciTech Connect

A survey has been completed to examine the problems and complications arising from wind loading on solar concentrators. Wind loading is site specific and has an important bearing on the design, cost, performance, operation and maintenance, safety, survival, and replacement of solar collecting systems. Emphasis herein is on paraboloidal, two-axis tracking systems. Thermal receiver problems also are discussed. Wind characteristics are discussed from a general point of view; current methods for determining design wind speed are reviewed. Aerodynamic coefficients are defined and illustrative examples are presented. Wind tunnel testing is discussed, and environmental wind tunnels are reviewed; recent results on heliostat arrays are reviewed as well. Aeroelasticity in relation to structural design is discussed briefly. Wind loads, i.e., forces and moments, are proportional to the square of the mean wind velocity. Forces are proportional to the square of concentrator diameter, and moments are proportional to the cube of diameter. Thus, wind loads have an important bearing on size selection from both cost and performance standpoints. It is concluded that sufficient information exists so that reasonably accurate predictions of wind loading are possible for a given paraboloidal concentrator configuration, provided that reliable and relevant wind conditions are specified. Such predictions will be useful to the design engineer and to the systems engineer as well. Information is lacking, however, on wind effects in field arrays of paraboloidal concentrators. Wind tunnel tests have been performed on model heliostat arrays, but there are important aerodynamic differences between heliostats and paraboloidal dishes.

Roschke, E.J.

1984-05-01

235

Coronal Heating and the Solar Wind Acceleration  

NASA Astrophysics Data System (ADS)

The twisting magnetic field as the DC energy injection will produce charge separation and consequently an electric field parallel to the magnetic field. Accelerated beam electrons (a few times thermal velocity) due to this electric filed will be stopped by classical collisions with ambient electrons and ions. The beam electrons, 10-3 of the bulk electrons, do not create electric currents due to the back streaming bulk electrons. Hence it is not the normal or anomalous Joule heating, but a co-spatial frictional heating, and yet bulk heating. The heating rate is the kinetic energy density of beams multiplied by the classical collision frequency, and is about 10-4 erg cm-3 s-1. It successfully reproduces observations of quiet and active regions, including the RTV scaling law. In the open field, the damping length of this Alfvénic twist is 0.4 solar radii. This is appropriate to produce slow and high-speed solar winds. Ion-cyclotron waves may be excited due to supra-thermal beams.

Hirayama, T.

236

Magnetic Maps and Coronal\\/Solar Wind Modeling: Practices and Pitfalls (Invited)  

Microsoft Academic Search

The ambient solar corona and solar wind play a crucial role in solar and heliospheric physics. The Sun's magnetic field is an essential ingredient of any predictive model of the solar wind. It defines the structure of the heliosphere, including the position of the heliospheric current sheet and the regions of fast and slow solar wind. The geoeffectiveness of CMEs

J. A. Linker; Z. Mikic; P. Riley; R. Lionello; V. S. Titov

2010-01-01

237

On the Role of Interchange Reconnection in the Generation of the Slow Solar Wind  

Microsoft Academic Search

The heating of the solar corona and therefore the generation of the solar wind, remain an active area of solar and heliophysics research. Several decades of in situ solar wind plasma observations have revealed a rich bimodal solar wind structure, well correlated with coronal magnetic field activity. Therefore, the reconnection processes associated with the large-scale dynamics of the corona likely

J. K. Edmondson

2011-01-01

238

Predicting solar and wind energy trends using cloud cover and wind velocity  

Microsoft Academic Search

Developments include: (1) a mode to predict potential and clear sky solar radiation on a horizontal surface and clear sky solar radiation on a tilted panel for any latitude, POTSOL; (2) a model to predict solar radiation on a horizontal surface for any latitude as a function of total opaque cloud cover, ESR; and (3) a program to estimate wind

Brinsfield

1981-01-01

239

Using Solar Wind Composition As A Tracer For Solar Processes: Applications For Plastic On Stereo  

NASA Astrophysics Data System (ADS)

Solar wind composition is increasingly being used as a tracer for various processes in the solar atmosphere and in interplanetary space. We will discuss applications of solar wind composition measurements that are relevant for the STEREO mission and that will be supplied by the PLASTIC sensor. Solar wind elemental abundances are affected by processes acting in the solar interior, chromosphere, and in the corona, while charge-state composition is largely determined in the corona. Farther out in the inner heliosphere, composition measurements can give information about interplanetary processes and serves as an excellent tracer for the coronal and chromospheric origin of the measured solar wind. Coronal mass ejections often exhibit unusual charge-state and elemental composition that is indicative of unusual conditions in the solar atmosphere prior and during the launch of the ejection. We will discuss observational opportunities unique to collaborative studies with vari- ous instruments on STEREO.

Wimmer-Schweingruber, Robert F.; Allegrini, Frédéric; Blush, Lisa; Bochsler, Peter; Fischer, Josef; Wurz, Peter; Galvin, A. B.; Moebius, E.; Klecker, B.; Thompson, B.; Plastic Team

240

Martian Ionospheric and Atmospheric Interaction Under Extreme Solar Wind Conditions  

NASA Astrophysics Data System (ADS)

As a weakly magnetized planet, Mars interacts directly with the solar wind. During periods of enhanced solar activities, solar radiation, as well as the interplanetary magnetic field (IMF), solar wind plasma density and flow speed can be greatly enhanced. The planetary particle escape rate is estimated to be more than an order of magnitude larger under extreme solar wind conditions than in normal situations. To understand the responses and its long-term consequences of the Martian ionosphere and atmosphere to extreme space weather events, we study Martian ionospheric and atmospheric interaction with extreme solar wind conditions using two sophisticated 3D models. We use a multi-species global MHD model to simulate cases with enhanced solar wind density, flow speed, magnetic field and intensity of the solar radiation, respectively to quantify the effect of each parameter and to identify the most significant one that cause the enhancement of the particle escape. A newly developed 3D test particle model, which traces the motion of pick-up ions is also used to examine the same problem based on the corresponding MHD electro-magnetic field results. The calculated ion escape fluxes for different ion species will be compared with MHD model results.

Ma, Y.; Fang, X.; Nagy, A. F.; Russell, C. T.

2008-12-01

241

Genesis capturing the sun: Solar wind irradiation at Lagrange 1  

NASA Astrophysics Data System (ADS)

Genesis, a member of NASAs Discovery Mission program, is the world’s first sample return mission since the Apollo program to bring home solar matter in ultra-pure materials. Outside the protection of Earth’s magnetosphere at the Earth-Sun Lagrange 1 point, the deployed sample collectors were directly exposed to solar wind irradiation. The natural process of solar wind ion implantation into a highly pure silicon (Si) bulk composition array collector has been measured by spectroscopic ellipsometry and scanning transmission electron microscopy (STEM). Ellipsometry results show that bulk solar wind ions composed of approximately 95% H+, 4% He+ and <1% other elements physically altered the first 59-63 nm of crystalline silicon substrate during 852.8 days of solar exposure. STEM analysis confirms that the solar accelerated ions caused significant strain and visible structural defects to the silicon structure forming a 60-75 nm thick irradiation damage region directly below the surface SiO2 native oxide layer. Monte Carlo simulations of solar wind H, He, C, O, Ne, Mg, Si and Fe ion collisions in the Si collector with fluences calculated from the Genesis and ACE spacecrafts were used to estimate the energy deposited and Si vacancies produced by nuclear stopping in a flight-like Si bulk array collector. The coupled deposited energy model with the flown Genesis Si in situ measurements provides new insight into the basic principles of solar wind diffusion and space weathering of materials outside Earth’s magnetosphere.

Calaway, Michael J.; Stansbery, Eileen K.; Keller, Lindsay P.

2009-04-01

242

Mass dragged from Mars's atmosphere by the solar wind  

NASA Astrophysics Data System (ADS)

In the past Mars had a denser atmosphere, but it lacks a magnetic field to protect the ionosphere and exosphere from the solar wind. A model describing the loss of atmosphere by the erosion of the solar wind in geologic time is presented. Recent results shows that the Martian dynamo existed in Early and Middle Noachian. Then solar wind erosion would have started at the end of Middle Noachian or the beginning of Late Noachian. With this assumption the amount of volatiles dragged by the solar wind, if the chronology developed by Neukum and Wise is correct, is in the range of 0.472 to 1.89 Terrestrial Atmospheric Masses (TAM). If the chronology developed by Hartmann et al. is correct, the loss remains in the range of 0.0624 to 0.25 TAM.

Durand-Manterola, H. J.

2003-12-01

243

Velocity of the Solar Wind at Low Heliographic Latitudes.  

National Technical Information Service (NTIS)

Data from comet tail deflection observations were used to analyze the relationship between the solar-wind aberrational velocity and the heliographic latitude in the near-equatorial region. The aberrational velocities are found to vary with heliographic la...

V. P. Tarashchuk

1976-01-01

244

Solar wind alpha particle capture at Mars and Venus  

NASA Astrophysics Data System (ADS)

Helium is detected in the atmospheres of both Mars and Venus. It is believed that radioactive decay of uranium and thorium in the interior of the planets' is not sufficient to account for the abundance of helium observed. Alpha particles in the solar wind are suggested to be an additional source of helium, especially at Mars. Recent hybrid simulations show that as much as 30% of the alpha particles can be lost from the solar wind due to charge-exchange processes associated with the Mars/solar wind interaction. We use ion data from the ASPERA-3 and ASPERA-4 instruments on Mars and Venus Express to estimate how efficient solar wind alpha particles are captured in the atmospheres of the two planets.

Stenberg, Gabriella; Barabash, Stas; Nilsson, Hans; Fedorov, Andrei; Brain, Dave

2010-05-01

245

Solar Wind Charge State Composition Results from PLASTIC  

NASA Astrophysics Data System (ADS)

The PLASTIC instrument on the STEREO spacecraft provides solar wind proton moments and heavy ion composition. Using an electrostatic analyzer with a time of flight and residual energy measurement, it can supply mass and ionic charge state for solar wind heavy ions. Preliminary results for iron will be shown for selected events, including the possible flux rope passage on May 21-22, 2007, and a near-magnetotail passage in February, 2007.

Popecki, M.; Galvin, A. B.; Kistler, L. M.; Moebius, E.; Klecker, B.; Kucharek, H.; Simunac, K.; Bochsler, P.; Blush, L.; Karrer, R.; Daoudi, H.; Opitz, A.; Giammanco, C.; Wimmer-Schweingruber, R.

2007-12-01

246

Eigenmode Structure in Solar-Wind Langmuir Waves  

Microsoft Academic Search

We show that observed spatial- and frequency-domain signatures of intense solar-wind Langmuir waves can be described as eigenmodes trapped in a parabolic density well. Measured solar-wind electric field spectra and waveforms are compared with 1D linear solutions and, in many cases, can be represented by 1 3 low-order eigenstates. To our knowledge, this report is the first observational confirmation of

R. E. Ergun; D. M. Malaspina; Iver H. Cairns; M. V. Goldman; D. L. Newman; P. A. Robinson; S. Eriksson; J. L. Bougeret; C. Briand; S. D. Bale; C. A. Cattell; P. J. Kellogg; M. L. Kaiser

2008-01-01

247

Solar wind forcing at Mercury: WSA-ENLIL model results  

NASA Astrophysics Data System (ADS)

Analysis and interpretation of observations from the MESSENGER spacecraft in orbit about Mercury require knowledge of solar wind "forcing" parameters. We have utilized the Wang-Sheeley-Arge (WSA)-ENLIL solar wind modeling tool in order to calculate the values of interplanetary magnetic field (IMF) strength (B), solar wind velocity (V) and density (n), ram pressure (~nV2), cross-magnetosphere electric field (V × B), Alfvén Mach number (MA), and other derived quantities of relevance for solar wind-magnetosphere interactions. We have compared upstream MESSENGER IMF and solar wind measurements to see how well the ENLIL model results compare. Such parameters as solar wind dynamic pressure are key for determining the Mercury magnetopause standoff distance, for example. We also use the relatively high-time-resolution B-field data from MESSENGER to estimate the strength of the product of the solar wind speed and southward IMF strength (Bs) at Mercury. This product VBs is the electric field that drives many magnetospheric dynamical processes and can be compared with the occurrence of energetic particle bursts within the Mercury magnetosphere. This quantity also serves as input to the global magnetohydrodynamic and kinetic magnetosphere models that are being used to explore magnetospheric and exospheric processes at Mercury. Moreover, this modeling can help assess near-real-time magnetospheric behavior for MESSENGER or other mission analysis and/or ground-based observational campaigns. We demonstrate that this solar wind forcing tool is a crucial step toward bringing heliospheric science expertise to bear on planetary exploration programs.

Baker, Daniel N.; Poh, Gangkai; Odstrcil, Dusan; Arge, C. Nick; Benna, Mehdi; Johnson, Catherine L.; Korth, Haje; Gershman, Daniel J.; Ho, George C.; McClintock, William E.; Cassidy, Timothy A.; Merkel, Aimee; Raines, Jim M.; Schriver, David; Slavin, James A.; Solomon, Sean C.; TráVní?Ek, Pavel M.; Winslow, Reka M.; Zurbuchen, Thomas H.

2013-01-01

248

Reproducing spacecraft measurements of magnetic correlations in the solar wind  

NASA Astrophysics Data System (ADS)

Analytical models for magnetic turbulence are an important ingredient in the theory of field line wandering and cosmic ray diffusion. In previous investigations, a so-called slab/2D model has been used. In the present article, we develop a more general analytical model for magnetic turbulence. This model is then compared with solar wind observations. We investigate numerically the possibility to explain the maltese cross structure of the correlation function of solar wind turbulence with this model.

Weinhorst, B.; Shalchi, A.

2010-03-01

249

Dust acoustic instability driven by solar and stellar winds  

SciTech Connect

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar or stelar wind. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion plasma propagates through another quasi-neutral plasma which contains dust, electrons and ions. The cometary dusty plasma in the solar wind appears to be practically always unstable.

Vranjes, J. [Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussels (Belgium)

2011-11-29

250

Structure of the Solar Wind and Compositional Variations  

Microsoft Academic Search

The composition of the solar wind is largely determined by the composition of the source material, i.e. the present-day composition\\u000a of the outer convective zone. It is then modified by the processes which operate in the transition region and in the inner\\u000a corona. In situ measurements of the solar wind composition give a unique opportunity to obtain information on the

P. Bochsler

1998-01-01

251

Wave Heating and Acceleration of the Fast Solar Wind  

Microsoft Academic Search

\\u000a Wave heating and acceleration of the fast solar wind has been studied and debated for decades. Low frequency MHD waves, and\\u000a high frequency ion-cyclotron waves were proposed separately as the sources of energy and momentum of the solar wind. Recent\\u000a UVCS observations and theoretical studies suggest that the resonant absorption of ion cyclotron waves heats and accelerates\\u000a the minor ions

L. Ofman

252

New Forecasting Factor for Solar Wind Velocity From EIT Observations  

NASA Astrophysics Data System (ADS)

Various solar wind velocity forecasting methods at 1AU have been developed during the last decade, such as Wang-sheeley model and Hakamada-Akasofu-Fry Version 2 (HAFv2) model. Some authors have found that Coronal hole(CH) areas can be used to forecast the solar wind velocity with better results in low CME activity periods(e.g. Vršnak et.al.). The property of the solar surface is a good indication of the following interplanetary and geomagnetic activities. We analyzed all EIT284Å images in almost the whole solar cycle 23 and developed a new forecasting factor(Pch) from the brightness of the solar Extreme Ultraviolet Images. and a good relationship was found between the Pch and solar wind velocity V three days later probed by ACE spacecraft. A simple method of forecasting the solar wind speed near earth in low CME activity periods is presented. For Pch and solar wind velocity, the linear correlation coefficients is R = 0.89 from 21 September until 26 December. For comparison we also analysed the same period data as Vršnak(2007) who using the coronal hole areas AM as input parameters for predicting solar wind velocity. The linear least-squares fit of Pch with the 3-day lag solar wind velocity showed a correlation coefficient R = 0.70, which is better than the result using AM(R = 0.62). The solar wind speed could be expressed as V (km s-1) = 337 + 0.00868 × Pch. The average of relative difference between the calculated and the observed values amounts to |?¯| ? 12.15%. Furthermore, for the ten peaks during the analysis period, AM and V just showed a correlation coefficient R = 0.32, much worse than using Pch factor which showed R = 0.75. Moreover, the Pch factor exterminated personal bias in the forecasting process, which existed in the method using AM as input parameters because the coronal hole boundary can not be easily determined since no quantitative criteria can be used to precisely locate coronal holes from observation. Finally, the expression of V by Pch is analysed, which showed the variation of background solar wind speed during the whole solar cycle 23.

Luo, B.; Liu, S.; Zhong, Q.; Gong, J.

2007-12-01

253

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

254

Dst Prediction Based on Solar Wind Parameters  

NASA Astrophysics Data System (ADS)

We reevaluate the Burton equation (Burton et al. 1975) of predicting Dst index using high quality hourly solar wind data supplied by the ACE satellite for the period from 1998 to 2006. Sixty magnetic storms with monotonously decreasing main phase are selected. In order to determine the injection term (Q) and the decay time (tau) of the equation, we examine the relationships between Dst^ast and VB_s, Delta Dst^ast and VB_s, and Delta Dst^ast and Dst^ast during the magnetic storms. For this analysis, we take into account one hour of the propagation time from the ACE satellite to the magnetopause, and a half hour of the response time of the magnetosphere/ring current to the solar wind forcing. The injection term is found to be Q({nT}/h)=-3.56VB_s for VB_s>0.5mV/m and Q({nT}/h)=0 for VB_s leq0.5mV/m. The tau (hour) is estimated as 0.060 Dst^ast + 16.65 for Dst^ast>-175nT and 6.15 hours for Dst^ast leq -175nT. Based on these empirical relationships, we predict the 60 magnetic storms and find that the correlation coefficient between the observed and predicted Dst^ast is 0.88. To evaluate the performance of our prediction scheme, the 60 magnetic storms are predicted again using the models by Burton et al. (1975) and O'Brien & McPherron (2000a). The correlation coefficients thus obtained are 0.85, the same value for both of the two models. In this respect, our model is slightly improved over the other two models as far as the correlation coefficients is concerned. Particularly our model does a better job than the other two models in predicting intense magnetic storms (Dst^ast lesssim -200nT).

Park, Yoon-Kyung; Ahn, Byung-Ho

2009-12-01

255

Ionic Composition and Electron Heating in the Fast Solar Wind  

Microsoft Academic Search

In-situ observations of charge states of fast solar wind ions reveal higher average charges than the coronal hole source regions as derived from spectroscopy, implying that some extra electron heating and ionization must have occurred in the wind acceleration region prior to freeze-in. We present an extensive analysis of Ulysses and ACE charge state data near the boundaries of different

Susan T. Lepri; J. M. Laming

2006-01-01

256

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

257

Solar wind parameters for magnetospheric magnetic field modeling  

Microsoft Academic Search

Magnetospheric magnetic fleld models are crucial for many space weather applications. However, the latest empirical models require solar wind and IMF data, which are not always available. Data gaps are especially common for times before the launch of the WIND spacecraft at the end of 1994, but even after then there are data gaps. We present a method to interpolate

Z. Qin; R. E. Denton; N. A. Tsyganenko; S. Wolf

2007-01-01

258

Identifying Current-Sheet-like Structures in the Solar Wind  

NASA Astrophysics Data System (ADS)

In past years, measurements of the solar wind plasma have advanced our understanding of MHD turbulence tremendously. At small scales, the solar wind is believed to be ve`xry multifractal with nonlinear interactions causing an intermittent energy dissipation, leading to possible current-sheet structures. In this Letter, we propose a systematic data analysis procedure to examine the existence of current sheets in the solar wind. We show that by studying the integrated distribution function F(?, ?) of the angle between two unit magnetic fields b?(t) and b?(t+?), as well as its ?-dependence, one can unambiguously identify the existence of current-sheet-like structures in the solar wind. Using this procedure, we analyze magnetic field data from the VHM/FGM instrument on board the spacecraft Ulysses for two periods, one in solar maximum and the other in solar minimum. In both cases, current sheets are clearly inferred. Furthermore, we also outline a procedure that allows the identification of the actual locations of these current sheets. Results from our analysis and the implications of the existence of current sheets in the solar wind are discussed.

Li, G.

2008-01-01

259

Solar and Solar-Wind Composition Results from the Genesis Mission  

NASA Astrophysics Data System (ADS)

The Genesis mission returned samples of solar wind to Earth in September 2004 for ground-based analyses of solar-wind composition, particularly for isotope ratios. Substrates, consisting mostly of high-purity semiconductor materials, were exposed to the solar wind at L1 from December 2001 to April 2004. In addition to a bulk sample of the solar wind, separate samples of coronal hole (CH), interstream (IS), and coronal mass ejection material were obtained. Although many substrates were broken upon landing due to the failure to deploy the parachute, a number of results have been obtained, and most of the primary science objectives will likely be met. These objectives include He, Ne, Ar, Kr, and Xe isotope ratios in the bulk solar wind and in different solar-wind regimes, and 15N/14N and 18O/17O/16O to high precision. The greatest successes to date have been with the noble gases. Light noble gases from bulk solar wind and separate solar-wind regime samples have now been analyzed. Helium results show clear evidence of isotopic fractionation between CH and IS samples, consistent with simplistic Coulomb drag theory predictions of fractionation between the photosphere and different solar-wind regimes, though fractionation by wave heating is also a possible explanation. Neon results from closed system stepped etching of bulk metallic glass have revealed the nature of isotopic fractionation as a function of depth, which in lunar samples have for years deceptively suggested the presence of an additional, energetic component in solar wind trapped in lunar grains and meteorites. Isotope ratios of the heavy noble gases, nitrogen, and oxygen are in the process of being measured.

Wiens, R. C.; Burnett, D. S.; Hohenberg, C. M.; Meshik, A.; Heber, V.; Grimberg, A.; Wieler, R.; Reisenfeld, D. B.

260

Solar and Solar-Wind Composition Results from the Genesis Mission  

NASA Astrophysics Data System (ADS)

The Genesis mission returned samples of solar wind to Earth in September 2004 for ground-based analyses of solar-wind composition, particularly for isotope ratios. Substrates, consisting mostly of high-purity semiconductor materials, were exposed to the solar wind at L1 from December 2001 to April 2004. In addition to a bulk sample of the solar wind, separate samples of coronal hole (CH), interstream (IS), and coronal mass ejection material were obtained. Although many substrates were broken upon landing due to the failure to deploy the parachute, a number of results have been obtained, and most of the primary science objectives will likely be met. These objectives include He, Ne, Ar, Kr, and Xe isotope ratios in the bulk solar wind and in different solar-wind regimes, and 15N/14N and 18O/17O/16O to high precision. The greatest successes to date have been with the noble gases. Light noble gases from bulk solar wind and separate solar-wind regime samples have now been analyzed. Helium results show clear evidence of isotopic fractionation between CH and IS samples, consistent with simplistic Coulomb drag theory predictions of fractionation between the photosphere and different solar-wind regimes, though fractionation by wave heating is also a possible explanation. Neon results from closed system stepped etching of bulk metallic glass have revealed the nature of isotopic fractionation as a function of depth, which in lunar samples have for years deceptively suggested the presence of an additional, energetic component in solar wind trapped in lunar grains and meteorites. Isotope ratios of the heavy noble gases, nitrogen, and oxygen are in the process of being measured.

Wiens, R. C.; Burnett, D. S.; Hohenberg, C. M.; Meshik, A.; Heber, V.; Grimberg, A.; Wieler, R.; Reisenfeld, D. B.

2007-06-01

261

STEREO's in-situ perspective on the solar minimum solar wind structure  

NASA Astrophysics Data System (ADS)

STEREO multipoint measurements of the solar wind structure with the IMPACT and PLASTIC investigations, near Earth but off the Sun-Earth line, allow its sources and structure to be examined at solar minimum when such studies are particularly straightforward. With the aid of 3D models of the heliosphere available at the CCMC, we map the in-situ observations to their solar sources using a combination of the open field regions inferred from the SECCHI EUVI imagers and SOHO EIT, and the magnetogram-based models of the corona and solar wind. Our ultimate goal is the continuous tracking of solar wind source regions as the STEREO mission progresses, as well as the use of the mappings to deduce the distinctive properties of solar wind from different types of sources

Luhmann, J. G.; Larson, D.; Schroeder, P.; Lee, C. O.; Sauvaud, J.; Acuna, M. H.; Galvin, A. B.; Russell, C. T.; Jian, L.; Arge, C. N.; Odstrcil, D.; Riley, P.; Howard, R. A.; Aschwanden, M.; MacNeice, P.; Chulaki, A.

2007-05-01

262

Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum  

NASA Astrophysics Data System (ADS)

STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

Galvin, A. B.; Popecki, M. A.; Simunac, K. D. C.; Kistler, L. M.; Ellis, L.; Barry, J.; Berger, L.; Blush, L. M.; Bochsler, P.; Farrugia, C. J.; Jian, L. K.; Kilpua, E. K. J.; Klecker, B.; Lee, M.; Liu, Y. C.-M.; Luhmann, J. L.; Moebius, E.; Opitz, A.; Russell, C. T.; Thompson, B.; Wimmer-Schweingruber, R. F.; Wurz, P.

2009-10-01

263

Solar wind: The solar wind and the Sun-Earth link  

NASA Astrophysics Data System (ADS)

The solar wind fills the space between the Sun and its planets, shapes the planetary environments and the heliosphere, and comes to a screeching halt at the heliopause, the boundary with the interstellar medium. This tenuous medium is a fertile environment for exotic plasma processes, most of which are not fully understood. It also holds the intimate secrets of the mechanisms heating the corona that continue to elude us. As the only accessible space plasma laboratory, we must continue its exploration in search of the processes that impact the Earth's environment and govern the evolution of stars and their planetary systems.

Habbal, Shadia Rifia; Woo, Richard

2004-08-01

264

Solar Wind Characteristics during the Current Solar Minimum (2007-2009): STEREO PLASTIC Observations  

NASA Astrophysics Data System (ADS)

We present solar wind trends observed by STEREO-A PLASTIC during Carrington Rotations 2053-2090 (February 2007 to December 2009) in relation to the current solar cycle conditions. The solar wind speed, mass number, and iron average charge state all showed a decline in the latter half of the survey period, during the time of minimal sunspot area, a retreat of the polar coronal holes (but with occasional isolated coronal holes) and a flattening of the neutral line.

Galvin, A. B.; Popecki, M.; Simunac, K.; Kistler, L.; Ellis, L.; Farrugia, C.

2010-06-01

265

Solar wind drivers of geomagnetic storms over more than four solar cycles  

NASA Astrophysics Data System (ADS)

Using a classification of near-Earth solar wind flows into corotating high-speed streams, slow interstream solar wind, and transients originating with coronal mass ejections at the Sun, we determine the drivers of geomagnetic storms of various sizes from 1964 to 2011 based on the Kp index, encompassing more than four solar cycles. We also briefly discuss storm occurrence rates since the beginning of Kp in 1932.

Richardson, Ian G.; Cane, Hilary V.

2013-06-01

266

How does the solar wind blow? Some basic aspects  

Microsoft Academic Search

Major properties of the solar atmosphere and wind are not understood. The energy distribution of the solar atmosphere perturbations, over nearly ten orders of magnitude in energy, is close (within one order of magnitude) to a power-law of index -2, even though there is no agreement on the detailed shape. There is no agreed explanation of the origin of the

Nicole Meyer-Vernet

2006-01-01

267

Solar wind control of the earth's electric field  

Microsoft Academic Search

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

R. Markson; M. Muir

1980-01-01

268

Heliospheric modeling used to map global solar wind flows  

Microsoft Academic Search

In a recent paper Leinert and Jackson (1998) analyzed brightness observations from the Helios spacecraft photometers, in situ data and interplanetary scintillation (IPS) velocities, and used these to model global heliospheric plasma changes over solar cycle no. 21. Our analysis shows changes in the solar wind flow in terms of mass and velocity over one Carrington rotation. We model the

B. V. Jackson; P. Hick; Ch. Leinert; A. Yokobe

1998-01-01

269

Path of the solar wind energy into the Earth s magnetosphere  

Microsoft Academic Search

The solar wind MHD generator is an unique energy source for all magnetospheric processes. The field-aligned currents directly transport the energy and momentum of the solar wind plasma to the Earth's ionosphere. The magnetospheric lobe and plasma sheet convection generated by the solar wind is another magnetospheric energy source. Plasma sheet particles and cold ionospheric polar wind ions are accelerated

I. Alexeev

2002-01-01

270

Utilizing wind and solar energy as power sources for a hybrid building ventilation device  

Microsoft Academic Search

Wind and solar energy are currently used to power many building ventilation devices. Such devices rely exclusively on either solar or wind energy, which limits their usefulness. A low-cost hybrid ventilation device that utilizes both wind and solar energy as power sources was designed to overcome some of the shortcomings of these devices. Wind tunnel testing conducted at the aerodynamics

Simon Shun; Noor A. Ahmed

2008-01-01

271

Termination of the solar wind in the hot, partially ionized interstellar medium  

Microsoft Academic Search

Theoretical foundations for understanding the problem of the termination of the solar wind are reexamined in the light of most recent findings concerning the states of the solar wind and the local interstellar medium. The investigation suggests that a simple extention of Parker's (1961) analytical model provides a useful approximate description of the combined solar wind, interstellar wind plasma flowfield

C. K. Lombard

1974-01-01

272

An Empirical Solar Wind Forecast Model From The Chromosphere  

NASA Astrophysics Data System (ADS)

Recently, we [McIntosh and Leamon, ApJL, 624, 117, 2005] correlated the inferred topography of the solar chromospheric plasma with in situ solar wind velocity and composition data measured at 1~AU. Specifically, the measured separation in height of the TRACE 1600Å\\ and 1700Å\\ UV band pass filters correlate very strongly with solar wind velocity and inversely with the ratio of ionic oxygen (O^{7+/O^{6+}}) densities. Here, we build on our previous results by presenting initial results of a model developed to so predict interplanetary solar wind conditions, using SOHO/MDI magnetograms with 96 minute cadence as proxies of chromospheric topography as input. Specifically, we use the observed correlation between the measured chromospheric travel-time and the magnetic field strength to allow us to convert the into a (reasonable) full-disk travel-time diagnostic (in place of limited field of view TRACE observations). Maps of full-disk travel-time are scaled to wind diagnostic maps which are then "forward" mapped into the heliosphere using a PFSS model. The resulting wind forecast matches the observed state of the solar wind remarkably well for a simple model.

Leamon, R. J.; McIntosh, S. W.

2006-12-01

273

Solar-Flare-Initiated Shock Waves; Blast Waves Riding on the Solar Wind.  

National Technical Information Service (NTIS)

Consider the speed of the solar flare initiated disturbance as having two separable components. These are: (1) the speed of the blast wave initiated by the impulsive release of energy by the solar flare and (2) the speed of the preexisting solar wind. In ...

D. F. Smart M. A. Shea

1983-01-01

274

Half a Century of Kinetic Solar Wind Models  

SciTech Connect

I outline the development of four generations of kinetic models, starting with Chamberlain's solar breeze exospheric model. It is shown why this first kinetic model did not give apposite supersonic evaporation velocities, like early hydrodynamic models of the solar wind. When a self-consistent polarization electric potential distribution is used in the coronal plasma, instead of the Pannekoek-Rosseland's one, supersonic bulk velocities are readily obtained in the second generation of kinetic models. It is outlined how the third and fourth generations of these models have improved the agreement with observations of slow and fast speed solar wind streams.

Lemaire, Joseph [Institut d'Aeronomie Spatiale de Belgique, 3, Avenue Circulaire, B-1180 Bruxelles (Belgium)

2010-03-25

275

Scale-free texture of the fast solar wind.  

PubMed

The higher-order statistics of magnetic field magnitude fluctuations in the fast quiet solar wind are quantified systematically, scale by scale. We find a single global non-Gaussian scale-free behavior from minutes to over 5 h. This spans the signature of an inertial range of magnetohydrodynamic turbulence and a ~1/f range in magnetic field components. This global scaling in field magnitude fluctuations is an intrinsic component of the underlying texture of the solar wind and puts a strong constraint on any theory of solar corona and the heliosphere. Intriguingly, the magnetic field and velocity components show scale-dependent dynamic alignment outside of the inertial range. PMID:22304144

Hnat, B; Chapman, S C; Gogoberidze, G; Wicks, R T

2011-12-29

276

Propagation of Radio Waves in the Corona and Solar Wind  

NASA Astrophysics Data System (ADS)

The solar corona and solar wind are plasmas characterized by large scale MHD structures, waves, and turbulence. These introduce both systematic and random variations in the refractive index which affect the propagation of radio waves. A variety of propagation phenomena occur -- regular refraction; angular, temporal, and spectral broadening; scintillations in amplitude and phase -- widely referred to as scattering phenomena. In this tutorial I review the physical basis of these phenomena and describe a variety of techniques designed to exploit observations of scattering phenomena to deduce properties of the corona and solar wind plasma.

Bastian, T. S.

277

Coronal Streamers and Their Associated Solar Wind Streams  

NASA Astrophysics Data System (ADS)

We use the EUV spectrometers aboard SOHO and Hinode and white-light coronagraphs to characterize the physical properties of coronal streamers during Earth/Ulysses quadrature configurations for the previous two solar minimum periods. In addition, comparisons between coronal observations and in situ measurements of solar wind plasma properties are being used to further characterize the origins of slow wind streams. In order to investigate slow solar wind heating and acceleration, we also compare with predictions from three-dimensional MHD models. We aim to use the empirical measurements to distinguish between different proposed physical processes for slow wind acceleration (e.g., waves/turbulence versus reconnection). This work is supported by NASA grant NNX10AQ58G to the Smithsonian Astrophysical Observatory.

Miralles, M. P.; Landi, E.; Cranmer, S. R.; Cohen, O.; Raymond, J. C.

2012-12-01

278

Modeling Solar Wind Mass-Loading Due to Cometary Dust  

NASA Astrophysics Data System (ADS)

Collisionless mass-loading was first discussed to describe interactions between the solar wind and cometary atmospheres. Recent observations have led to an increased interest in coronal mass-loading due to sun-grazing comets and collisional debris by sunward-migrating interplanetary dust particles. Using three-dimensional MHD simulations with the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) we have shown the impact on the solar wind from abrupt mass-loading in the coronal region. We also use the model as an application for a mass-loaded coronal wind due to a cometary source, which helps predict the impacts on solar wind acceleration and composition from past and upcoming sungrazing comets.

Rasca, Anthony; Horanyi, M.

2013-10-01

279

The effect of solar-wind structures on the magnetosphere: Current sheets and sudden wind shears  

NASA Astrophysics Data System (ADS)

The solar wind is full of strong current sheets and sudden velocity shears. Often the two types of structures are co-located, so 10 or 20 times per day the Earth simultaneously experiences a sudden change in the magnetic-field direction and a sudden change in the solar-wind flow vector. Using data analysis and simulations, the reaction of the Earth's magnetosphere to these sudden changes is explored.

Borovsky, J. E.; Welling, D. T.; Morley, S.; Birn, J.

2011-12-01

280

Evolution of Coronal Holes with the Solar Cycle: Implications for the Solar Wind at Earth  

NASA Astrophysics Data System (ADS)

The two main sources of space weather are coronal mass ejections (CMEs) and high speed solar wind streams, both of which vary with the solar activity cycle. Fast CMEs with strong southward fields are responsible for the most intense geomagnetic storms. Because the CME rate and speed follows the solar cycle, i.e. CMEs are more frequent and on average faster near solar maximum, strong and short-duration geomagnetic storms are prevalent during times of high solar activity. High speed solar wind streams emanating from low-latitude coronal holes at the Sun can also drive weak to moderate but long-duration geomagnetic storms. This kind of storms are more common during the declining phase of the solar cycle, when coronal holes at low latitudes tend to be large in size and long-lived. In this paper, we will focus on high speed solar wind streams and their solar sources. We will show how the distribution of coronal holes at the Sun affects the solar wind speeds seen at Earth and will discuss the importance of the solar polar magnetic fields for coronal holes near solar minimum, and particularly during recent minima. The past solar minimum and early phase of solar cycle 24 were characterized by low magnetic activity and weak polar magnetic fields. This magnetic configuration gave rise to small polar coronal holes and allowed large, low- to mid-latitude coronal holes to survive during times of very low solar activity, resulting in solar wind properties markedly different from the previous minima during the Space Age.

de Toma, G.

2011-12-01

281

CARBON IONIZATION STAGES AS A DIAGNOSTIC OF THE SOLAR WIND  

SciTech Connect

Oxygen charge states measured by in situ instrumentation have long been used as a powerful diagnostic of the solar corona and to discriminate between different solar wind regimes, both because they freeze in very close to the Sun, and because the oxygen element abundance is comparatively high, allowing for statistically relevant measures. Like oxygen, carbon is also rather abundant and freezes in very close to the Sun. Here, we show an analysis of carbon and oxygen ionic charge states. First, through auditory and Fourier analysis of in situ measurements of solar wind ion composition by ACE/SWICS we show that some carbon ion ratios are very sensitive to solar wind type, even more sensitive than the commonly used oxygen ion ratios. Then we study the evolution of the ionization states of carbon and oxygen by means of a freeze-in code, and find that carbon ions, commonly found in the solar wind, freeze in at comparable coronal distances, while oxygen ions evolve over a much larger range of coronal distances. Finally, we show that carbon and oxygen ion abundance ratios have similar sensitivity to the electron plasma temperature, but the carbon ratios are more robust against atomic physics uncertainties and a better indicator of the temperature of the solar wind source regions.

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

2012-01-10

282

Seasonal dependence and solar wind control of transpolar arc luminosity  

NASA Astrophysics Data System (ADS)

The influence of the solar wind and the interplanetary magnetic field (IMF) on the luminosity of transpolar arcs (TPAs) is examined by taking into account seasonal effects. The study focuses on those transpolar arcs that appear after an IMF By sign change during steady northward IMF. It includes 21 northern hemisphere events identified in a previous study from global UV images taken by the Polar spacecraft between 1996 and 2000. Sorting the TPA events by sign of the Earth dipole tilt we find that the TPAs which appear in the dark hemisphere are on average much weaker than TPAs in the sunlit hemisphere. For the dark hemisphere events, no clear correlation between solar wind parameters and TPA luminosity is found. However, in the sunlit hemisphere, a clear dependence on solar wind and IMF conditions is seen. The TPA brightness is strongly influenced by IMF magnitude, northward IMF Bz and solar wind speed. A weak, negative correlation with the ion density is found. The TPA luminosity in the sunlit hemisphere is much more strongly controlled by the magnetic energy flux than by the kinetic energy flux of the solar wind. This explains the absence of transpolar arcs for the two By sign change cases for positive dipole tilts with lowest magnetic energy flux values. The strong influence of the Earth dipole tilt on the transpolar arc luminosity appears due to the dependence of the ionospheric conductivity on solar EUV emissions.

Kullen, A.; Cumnock, J. A.; Karlsson, T.

2008-08-01

283

Extreme Solar Wind Conditions and Extreme Response of the Earth's Magnetosphere  

Microsoft Academic Search

To a very large extent, the solar wind controls magnetospheric activity, so that measurements of the solar wind upstream of the Earth can be used to predict the geomagnetic activity. We have developed a model to predict the Dst index based on available solar wind and ground magnetic field measurement. We will show that the model works under extreme solar

X. Li; M. Temerin; G. Siscoe; B. Tsurutani; S. Alex

2004-01-01

284

Long term variability in solar wind velocity and IMF intensity and the relationship between solar wind parameters & geomagnetic activity  

Microsoft Academic Search

A study is carried out on the mean monthly values of in situ observations of solar wind velocity (V) and the intensity of interplanetary magnetic field, Bto elucidate their long term variations using the technique of singular spectrum analysis. It is shown that Bexhibits a clear solar cycle signal with progressively deepening minimum and a well-defined longer period variation but

G. K. Rangarajan; L. M. Barreto

2000-01-01

285

Long term variability in solar wind velocity and IMF intensity and the relationship between solar wind parameters & geomagnetic activity  

Microsoft Academic Search

A study is carried out on the mean monthly values of in situ observations of solar wind velocity ( V ) and the intensity of interplanetary magnetic field, B to elucidate their long term variations using the technique of singular spectrum analysis. It is shown that B exhibits a clear solar cycle signal with progressively deepening minimum and a well-defined

G. K. Rangarajan; L. M. Barreto

2000-01-01

286

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

NASA Astrophysics Data System (ADS)

The MASS instrument on WIND contains the first isochronous time-off light 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.

1995-06-01

287

Conductive solar wind models in rapidly diverging flow geometries  

SciTech Connect

A detailed parameter study of conductive models of the solar wind has been carried out, extending the previous similar studies of Durney (1972) and Durney and Hundhausen (1974) by considering collisionless inhibition of thermal conduction, rapidly diverging flow geometries, and the structure of solutions for the entire n/sub 0/-T/sub 0/ plane (n/sub 0/ and T/sub 0/ are the coronal base density and temperature). Primary emphasis is placed on understanding the complex effects of the physical processes operative in conductive solar wind models. There are five points of particular interest that have arisen from the study: (1) neither collisionless inhibition of thermal conduction nor rapidly diverging flow geometries can significantly increase the solar wind speed at 1 AU; (2) there exists a firm upper limit on the coronal base temperature consistent with observed values of the coronal base pressure and solar wind mass flux density; (3) the principal effect of rapidly diverging flow geometries is a decrease in the solar wind mass flux density at 1 AU and an increase in the mass flux density at the coronal base; (4) collisionless inhibition of thermal conduction can lead to a solar wind flow speed that either increases or decreases with increasing coronal base density (n/sub 0/) and temperature (T/sub 0/, depending on the region of the n/sub 0/-T/sub 0/ plane considered; (5) there is a region of the n/sub 0/-T/sub o/ plane at high coronal base densities where low-speed, high-mass-flux, transonic solar wind flows exist: a region not previously considered.

Holzer, T.E.; Leer, E.

1980-09-01

288

Cosmic ray modulation by different types of solar wind disturbances  

NASA Astrophysics Data System (ADS)

Context. Solar wind disturbances such as interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) cause short-term cosmic ray depressions, generally denoted as Forbush decreases. Aims: We conduct a systematic statistical study of various aspects of Forbush decreases. The analysis provides empirical background for physical interpretations of short-term cosmic ray modulations. Methods: Firstly, we analyzed the effects of different types of solar wind disturbances, and secondly, we focused on the phenomenon of over-recovery (the return of the cosmic ray count to a value higher than the pre-decrease level). The analysis is based on ground-based neutron monitor data and the solar wind data recorded by the Advanced Composition Explorer. The correlations between various cosmic ray depressions and solar wind parameters as well as their statistical significance are analyzed in detail. In addition, we performed a normalized superposed epoch analysis for depressions and magnetic field enhancements. Results: The analysis revealed differences in the relationship between different solar wind disturbances and cosmic ray depression parameters. The amplitude of the depression for ICMEs was found to correlate well with the amplitudes of magnetic field strength and fluctuations, whereas for CIRs we found only the correlation between the amplitude of the depression and the solar wind disturbance dimension proxy vtB. Similar behavior was found for shock and no-shock events, respectively. The CIR/ICME composites show a specific behavior that is a mixture of both ICMEs and CIRs. For all analyzed categories we found that the duration of the depression correlates with the duration of the solar wind disturbance. The analysis of the over-recovery showed that there is no straightforward relationship to either "branching-effect" or geomagnetic effects, therefore we propose a scenario where the "branching-effect" is caused by several factors and is only indirectly related to the over-recovery.

Dumbovi?, M.; Vršnak, B.; ?alogovi?, J.; Župan, R.

2012-02-01

289

Stellar wind - observations and theories. Part II. Theoretical modelsof the solar wind.  

NASA Astrophysics Data System (ADS)

Theoretical models of the solar wind - Parker's thermally driven, MHD waves driven and Weber and Davis wind model from rotating Sun are described. The influence of the additional sources or sinks of the energy and momentum on the value of mass loss rates Mand terminal velocity v, according to Leer and Holzer results, is presented.

Krogulec, M.

290

Classification of the low-speed solar wind.  

NASA Astrophysics Data System (ADS)

By analyzing the solar wind data observed at 1 AU during the years from 1970 to 1980, the authors show that about 60% of the coronal streamer-associated streams and about 40% of the CME-associated clouds are the low-speed wind of which the flow speed is less than or equal to 350 km/sec, and about 80% of the low-speed wind originate from the coronal streamers. In addition to the coronal streamers and the CMEs, there seems to be another source region of the low-speed wind.

Xu, Zhaoe-Pu; Xu, Fang-Xiao

1989-11-01

291

Solar wind in the outer Heliosphere by IPS observations  

NASA Astrophysics Data System (ADS)

Planetary magnetospheres exist within the supersonic solar wind and are strongly influenced by variations in the solar wind blowing on them. We have carried out IPS observations at decameter wavelengths with UTR-2 radio telescope using new theoretical and experimental approaches. They allow us to study effectively the solar wind at the large distances from the Sun (up to 5 AU, Jupiter's orbit). The solar wind parameters are obtained by fitting model power spectra to observed ones. The phase screen model is usually used for this purpose at the high frequencies. However, at the large elongations and at the low frequencies the scattering medium is essentially expanded and the most scattering layer is situated near an observer, so use of the phase screen model is not correct. More correct ways are provided by multiple scattering theory methods such as the Feynman path-integral technique. We have adapted the Feynman path-integral technique to calculate model power spectra and to obtain the solar wind parameters. Also, the UTR-2 radio telescope has been equipped with new wide-band radiometers. These allow us to obtain scintillation power spectra with dynamic range of 3 to 4 orders, unachievable before at decameter wavelengths. Since 2003 we have been observing the IPS scintillations, regularly. The brief results of the observations are the next. In most cases we detect the presence of several solar wind flows with different velocities, densities and thicknesses along the line of sight. We managed to trace the movements of high-speed streams of different origins. In November-December 2005 we observed fast streams moving across the lines of sight to the radio sources 3C144, 3C154, 3C196, 3C254. The variations of the solar wind velocity and the scintillation index were in good agreement with the behavior of the plasma density measured by SOHO. A high-speed streams caused by transient events on the Sun are well known to exist in the solar wind. A shock caused by the powerful solar flare 17.03.2003 and the filament outburst 18.03.2003 reached Earth's orbit on March, 20 and was registered by Genesis Discovery Mission as a jump of the solar wind density and speed. We carried out IPS observations during March 21-24 when the shock went by the Earth and was moving in the outer Heliosphere. To probe the solar wind we used two radio sources 3C380 and 3C254 with the strongly different elongations and ecliptic latitudes. The agreement between the solar wind velocity obtained by IPS and that measured directly by Genesis Discovery Mission renders support to our method of analysis. Our investigations have shown the high efficiency of IPS method at decameter wavelengths for studies of the solar wind in the outer Heliosphere. The obtained results and methods are very helpful for investigations of the solar wind effect on planets. Future investigations will require significant improvements in spatial resolution which can be reached by using the larger number of scintillating radio sources.

Kalinichenko, N.; Konovalenko, A.; Falkovich, I.; Olyak, M.

2007-08-01

292

Self-similar signature of the active solar corona within the inertial range of solar-wind turbulence.  

PubMed

We quantify the scaling of magnetic energy density in the inertial range of solar-wind turbulence seen in situ at 1 AU with respect to solar activity. At solar maximum, when the coronal magnetic field is dynamic and topologically complex, we find self-similar scaling in the solar wind, whereas at solar minimum, when the coronal fields are more ordered, we find multifractality. This quantifies the solar-wind signature that is of direct coronal origin and distinguishes it from that of local MHD turbulence, with quantitative implications for coronal heating of the solar wind. PMID:17677760

Kiyani, K; Chapman, S C; Hnat, B; Nicol, R M

2007-05-23

293

Magnetic Reconnection in the Solar Wind: An Update  

NASA Astrophysics Data System (ADS)

Magnetic reconnection in the solar wind commonly occurs in a quasi-stationary mode. It produces extensive Petschek-like exhausts of roughly Alfvénic jetting plasma typically bounded by back-to-back rotational discontinuities that bifurcate a reconnecting current sheet. It occurs most frequently at current sheets associated with relatively small (<90°) magnetic field rotations in low (<1) beta plasma. Reconnection exhausts are relatively common (typically 2-3 events/day at 1 AU) in the low-speed wind and within interplanetary coronal mass ejections, and less common (0.6 events/day) in the Alfvénic turbulence characteristic of the high-speed wind from coronal holes. Reconnection occurs relatively infrequently at the heliospheric current sheet, HCS, but observations of exhausts at the HCS are particularly revealing of the magnetic field topology changes associated with the reconnection process. Reconnection in the solar wind is not explosive-the magnetic energy release occurs over a long time interval following reconnection as the Alfvénic disturbances initiated by the process propagate into the surrounding solar wind plasma. There is as yet no good evidence to suggest that reconnection in the solar wind ever produces substantial particle acceleration beyond that associated with the bulk acceleration of the plasma.

Gosling, J. T.

2010-03-01

294

Flank Magnetopause Boundary Perturbations at Low Solar Wind Dynamic Pressure  

NASA Astrophysics Data System (ADS)

It is widely accepted that magnetic reconnection and Kelvin-Helmholtz instabilities are the two most efficient mechanisms of transferring solar wind mass, momentum and energy into the magnetosphere across the magnetopause boundary layer. The relative effectiveness of the two mechanisms under different solar wind conditions and at different locations at the magnetopause is still under intense investigations. We present studies of plasma characteristics of magnetopause boundary perturbations at the flanks during events of low solar wind dynamic pressure. Using observations from Cluster and/or THEMIS conjunctions, we examine plasma properties of magnetopause boundary perturbations that are essential for reconnection and Kelvin-Helmholtz instability. We study plasma properties including variations of plasma flows, magnetic and electric field components, as well as field-aligned current generation across and further away from the boundaries. Events with prolonged low solar wind dynamic pressure, 1 nPa or less, but with small, variable IMF Bz are studied in detail to further understand how the two competing mechanisms, reconnection and Kelvin-Helmholtz instability, contribute to the momentum transfer across the boundary at the flank magnetopause during intervals of relatively quiet solar wind conditions. Such events are particularly valuable as the effects of enhanced global convection and strong coupling between the ionosphere and magnetosphere due to major geomagnetic storms and substorms are absent, allowing us to better understand local plasma instabilities at the boundary.

Chen, S.; Le, G.; Angelopoulos, V.

2010-12-01

295

The solar wind control of reconnection at the dayside magnetopause  

SciTech Connect

The solar wind control of reconnection is examined using both correlation analysis of geomagnetic activity and in situ observations at the magnetopause. The correlation of geomagnetic activity, as measured by the am index, reveals a dependence of reconnection on the direction of the interplanetary magnetic field, the solar wind magnetosonic Mach number, and the solar wind dynamic pressure. In situ observations of accelerated flows and the magnetic normal component at the magnetopause using the ISEE 1 and 2 spacecraft are correlated with solar wind and magnetosheath parameters. The magnitude of the magnetic normal component is found to increase as the solar wind magnetic field clock angle becomes southward. The occurrence of accelerated flows increases with increasing southward field as well. Accelerated flows are found to occur with greater probability when the magnetosheath beta is low. Accelerated flows occur most often near the subsolar point. The direction and location of accelerated flows indicate the merging line tilts according to the direction of the interplanetary magnetic field with an average length of approximately 6 R[sub e].

Scurry, L.R.

1992-01-01

296

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

297

The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation for Solar Probe Plus  

NASA Astrophysics Data System (ADS)

The NASA Solar Probe Plus mission will be humanity’s first direct visit to the atmosphere of our Sun. The spacecraft will close to within nine solar radii (about four million miles) of the solar surface in order to observe the heating of the corona and the acceleration of the solar wind first hand. A key requirement for Solar Probe Plus is the ability to make continuous, accurate, and fast measurements of the electrons and ionized helium (alpha-particles) and hydrogen (protons) that constitute the bulk of the solar wind. The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation is a two-instrument suite that provides these observations. The purpose of this talk is to describe the science motivation for SWEAP, the instrument designs, and the expected data products. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SWEAP measurements enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, high-energy particle acceleration, and the interaction between solar wind and the dust environment of the inner heliosphere. SPC is a Faraday Cup (FC) that looks at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). SPAN-A and -B are rotated 90 degrees relative to one another so their broad FOV combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution at 0.5-16 Hz and flow angles and fluxes at 128 Hz. Continuous buffering provides triggered burst observations during shocks, reconnection events, and other transient structures with no changes to the instrument operating mode.

Kasper, J. C.; SWEAP Investigation Team

2010-12-01

298

Prediction of solar wind structures between Venus and Mars orbits  

NASA Astrophysics Data System (ADS)

We performed a detailed study of the temporal evolution and spatial variation of the solar wind on different scales during the recent long solar activity minimum. We use STEREO Ahead and Behind, Venus Express and Mars Express in-situ plasma measurements to infer the solar wind properties and structures at any heliospheric in-ecliptic positions. We test the range of validity of these predictions by comparing their results. We find that our predictions are valid at radial spacecraft separations as far as the Mars and Venus orbits and even at 60 degrees longitudinal separation due to the steadiness of the solar wind at this time. Our results prove that two spacecraft positioned at the L4 and L5 Lagrangian points would be indeed suitable for terrestrial space weather forecasting of solar wind features such as high speed streams and stream interaction regions. Since 2010 the frequency of transients increases as the solar cycle proceeds towards activity maximum, so in this time period we expect lower correlations between the datasets of two widely separated spacecraft.

Opitz, A.; Fedorov, A.; Wurz, P.; Sauvaud, J.; Luhmann, J. G.

2011-12-01

299

Solar Wind and Global Electron Hemispheric Power in Solar Minimum Intervals  

NASA Astrophysics Data System (ADS)

We assess the periodicities of the hourly and daily solar wind velocity (Vsw) and average global electron auroral hemispheric power (Hpeg) with Lomb-Scargle (L-S) and Fast Fourier Transforms (FFTs) using three Carrington Rotations (CRs) to a year or more of data in two different solar minimum periods. The first Whole Sun Month (WSM) interval (96223-96252) was during the last solar minimum where the solar magnetic field relaxed into a dipole. A strong 'semiannual' periodicity in Vsw maximizing in equinoxes was found, which enhanced the equinoctial maxima found in Hpeg (and Kp) due to the preferred solar wind and magnetospheric reconnection during equinoxes. In the present solar minimum, the solar magnetic field has considerable quadrupole components during the Whole Heliospheric Interval (WHI, 08080-08107). Hpeg exhibits solar rotational periodicities similar to those for Vsw using both L-S and FFT analyses, where the 9- day periodicity is particularly strong in the present solar minimum period. The 9-day periodicity in the WHI CR was caused by three periods of slow-speed solar wind from near the ecliptic plane as seen in the sign of IMF Bx. Periodicities are examined in Vsw since 1972, and in Hpeg since 1978 to assess solar cycle variations. Periodicities longer than 100 days are not as strong or as well correlated between Vsw and Hpeg compared to the shorter solar rotational periodicities.

Emery, B. A.; Richardson, I. G.; Evans, D. S.; Rich, F. J.; Wilson, G.

2008-12-01

300

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

301

Evaluation of Wind Loads on Solar Panels  

Microsoft Academic Search

The current impetus for alternative energy sources is increasing the demand for solar energy technologies in Florida – the Sunshine State. Florida’s energy production from solar, thermal or photovoltaic sources accounts for only 0.005% of the state total energy generation. The existing types of technologies, methods of installation, and mounting locations for solar panels vary significantly, and are consequently affected

Johann Barata

2011-01-01

302

Solar wind parameters dependence of energy coupling between solar wind and magnetosphere during northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We statistically study the solar wind parameter dependence of the magnetospheric activities during northward interplanetary magnetic fields (IMFs) events (Bz > 10 nT, last over 3 hours). It was found that the energy coupling between solar wind and magnetosphere during northward IMFs was mainly controlled by solar wind velocity and IMF clock angle (?). A northward IMF coupling function was derived based on the dimensional analysis and quantitative analysis of the IMF and the geomagnetic indices. This coupling function can combine the influences of both IMF ? and solar wind velocity and well describe the energy input from the solar wind into the magnetosphere during northward IMF events. In addition, it was shown that when ? is greater than ~ 50o, the energy input increases remarkably as ? increases. Most importantly, our coupling function can measure the relative importance between the viscous interaction and the By reconnection in controlling the energy input into the magnetosphere during northward IMFs. The viscous interaction will overweigh the By reconnection in the northward IMF events with ? less than 70o. In contrast, for those northward IMF events with ? greater than 70o, the By reconnection may be more important than the viscous interaction.

Luo, H.; Chen, G. X.

2012-04-01

303

Electrostatic Short-Scale Termination of Solar-Wind Turbulence  

SciTech Connect

Recent hybrid Vlasov simulations [F. Valentini et al., Phys. Rev. Lett. 101, 025006 (2008)] have shown that the short-scale termination of solar-wind turbulence is characterized by the occurrence of longitudinal electrostatic fluctuations. Beside the ion-acoustic branch, in agreement with solar-wind observations, a novel branch of acoustic-like waves, with phase velocity close to the ion thermal speed, has been recovered in the simulations. In this Letter, we show that these waves turn out to be Bernstein-Greene-Kruskal-like solutions of the hybrid Vlasov-Maxwell equations, driven by kinetic effects of resonant particle trapping. We also discuss the development of the solar-wind turbulent spectra across the ion inertial length and especially stress the fact that turbulence privileges acoustic paths to develop towards short wavelengths.

Valentini, Francesco; Veltri, Pierluigi [Dipartimento di Fisica and CNISM, Universita della Calabria, 87036 Rende (Italy)

2009-06-05

304

Coupling of the solar wind to measures of magnetic activity  

SciTech Connect

The technique of linear prediction filtering has been used to generate empirical response functions relating the solar wind electric field to the most frequently used magnetic indices, AL, AU, Dst and ASYM. Two datasets, one from 1967-1968 and one from 1973-1974, provided the information needed to calculate the empirical response functions. These functions have been convolved with solar wind observations obtained during the IMS to predict the indices. These predictions are compared with the observed indices during two, three-day intervals studied extensively by participants in the CDAW-6 workshop. Differences between the observed and predicted indices are discussed in terms of the linear assumption and in terms of physical processes other than direct solar wind-magnetosphere interaction.

McPherron, R.L.; Fay, R.A.; Garrity, C.R.; Bargatze, L.F.; Baker, D.N.; Clauer, C.R.; Searls, C.

1984-01-01

305

Intermittency and local heating in the solar wind.  

PubMed

Evidence for nonuniform heating in the solar wind plasma near current sheets dynamically generated by magnetohydrodynamic (MHD) turbulence is obtained using measurements from the ACE spacecraft. These coherent structures only constitute 19% of the data, but contribute 50% of the total plasma internal energy. Intermittent heating manifests as elevations in proton temperature near current sheets, resulting in regional heating and temperature enhancements extending over several hours. The number density of non-Gaussian structures is found to be proportional to the mean proton temperature and solar wind speed. These results suggest magnetofluid turbulence drives intermittent dissipation through a hierarchy of coherent structures, which collectively could be a significant source of coronal and solar wind heating. PMID:23004953

Osman, K T; Matthaeus, W H; Wan, M; Rappazzo, A F

2012-06-26

306

Ulysses solar wind plasma observations at high southerly latitudes.  

PubMed

Solar wind plasma observations made by the Ulysses spacecraft through -80.2 degrees solar latitude and continuing equatorward to -40.1 degrees are summarized. Recurrent high-speed streams and corotating interaction regions dominated at middle latitudes. The speed of the solar wind was typically 700 to 800 kilometers per second poleward of -35 degrees . Corotating reverse shocks persisted farther south than did forward shocks because of the tilt of the heliomagnetic streamer belt. Sporadic coronal mass ejections were seen as far south as -60.5 degrees . Proton temperature was higher and the electron strahl was broader at higher latitudes. The high-latitude wind contained compressional, pressure-balanced, and Alfvénic structures. PMID:17774231

Phillips, J L; Bame, S J; Feldman, W C; Gosling, J T; Hammond, C M; McComas, D J; Goldstein, B E; Neugebauer, M; Scime, E E; Suess, S T

1995-05-19

307

Simulation of period doubling of recurrent solar wind structures  

SciTech Connect

In 1974, IMP, Pioneer 11 and Pioneer 10 observed a recurrent solar wind structure over five consecutive solar rotations at three different trajectories between 1 and 6 AU. Using MHD simulations and input functions generated from plasma and magnetic field data observed from Pioneer 11. The authors study the continuing evolution of this solar wind structure between 5 and 20 AU. This simulation uses the shock interactions model which treats MHD shocks as discontinuity surfaces with zero thickness and which uses the exact Rankine-Hugoniot relations to describe the jump conditions. The model can calculate the collision and merging of shocks and the dynamical evolution of the solar wind in the outer heliosphere. The simulation result shows that between 5 and 10 AU there is an evolution from two corotating interaction regions per solar rotation to one merged interaction region (MIR) per solar rotation near 10 AU, i.e., period doubling has occurred. Each MIR was bounded by a forward and a reverse shock and additional weaker shocks may exist inside the MIR. Between 10 and 20 AU the structure of one MIR per solar rotation appears as a very persistent structure.

Whang, Y.C. (Catholic Univ. of America, Washington, DC (USA)); Burlaga, L.F. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1990-12-01

308

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 and "hysteresis" effect on foF2. Ionospheric response to changes in solar sector polarity has not been fully documented previously, partly due to the limitation of observations. In this study, a solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances 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 IMF Bz component for the same solar sector polarity has opposite signs between March equinox and September equinox, and also between June solstice and December solstice. In order to know how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings, 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 southwardBzcomponents 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; Liu, Libo; Zhao, Biqiang; Wan, Weixing

2012-08-01

309

78 FR 38028 - Winding Creek Solar LLC; Notice of Petition for Enforcement  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF ENERGY Federal Energy Regulatory Commission...QF13-403-001] Winding Creek Solar LLC; Notice of Petition...2013, Winding Creek Solar LLC filed a Petition...requesting the Federal Energy Regulatory...

2013-06-25

310

Search for fine scale structures in high latitude solar wind  

NASA Astrophysics Data System (ADS)

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.

1995-06-01

311

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

312

Source reliability in a combined wind-solar-hydro system  

NASA Astrophysics Data System (ADS)

The results of an examination of the feasibility of using coupled wind-solar-hydro power generation systems to provide all of Portugal's electricity by the year 2000 are reported. Portugal used 15.6 TWh of electricity in 1981, of which hydro supplied 10 TWh. Demand is expected to reach 34 TWh in 2000 AD. The full development of hydropower resource would furnish 18 TWh and a storage capacity of 4.5 TWh. The installed hydro system could meet the peak demand of 6 GW, while solar cells and wind turbines must produce 16 TWh annually plus a reserve. The Growian wind turbine, 100 m tall, is considered for its 2.2 MW output. A coastal strip of wind turbines 150 x 20 km, with 1 km spacing between the machines, would be needed to produce 5.4 GW of power. Partially tracking solar cell arrays generating 9.4 GW of electricity would require an area of 100 sq km. Computer simulations of the annual rainfall, combined with projections of the variations in wind-solar output, demonstrates that a reserve margin of 1.20 will be necessary. The costs of installation of the renewable energy converters are estimated at about three times that currently necessary for obtaining the same capacity from fission power plants, although the situation may change due to import and technical considerations.

Traca de Almeida, A.; Martins, A.; Jesus, H.; Climaco, J.

1983-06-01

313

Modified Temperature-Anisotropy Instability Thresholds in the Solar Wind  

NASA Astrophysics Data System (ADS)

The proton and electron temperature anisotropies in the solar wind are constrained by the instability thresholds for temperature-anisotropy-driven kinetic plasma instabilities. The modifications to the marginal instability conditions from accounting for the influence of damping connected with the collisional effects in the solar wind plasma are calculated for right- and left-handed polarized parallel propagating Alfvén waves and mirror and firehose fluctuations. These modifications provide tighter threshold constraints compared to the marginal thresholds but do not fully explain the observations at small values of the parallel plasma beta.

Schlickeiser, R.; Michno, M. J.; Ibscher, D.; Lazar, M.; Skoda, T.

2011-11-01

314

Ion Kinetic Scale in the Solar Wind Observed  

NASA Astrophysics Data System (ADS)

This Letter shows the first results from the solar wind monitor onboard the Spektr-R spacecraft which measures plasma moments with a time resolution of 31 ms. This high-time resolution allows us to make direct observations of solar wind turbulence below ion kinetic length scales. We present examples of the frequency spectra of the density, velocity, and thermal velocity. Our study reveals that although these parameters exhibit the same behavior at the magnetohydrodynamic scale, their spectra are remarkably different at the kinetic scale.

Šafránková, Jana; N?me?ek, Zden?k; P?ech, Lubomír; Zastenker, Georgy N.

2013-01-01

315

Solar wind alpha particle capture at Mars and Venus  

NASA Astrophysics Data System (ADS)

Helium is detected in the atmospheres of both Mars and Venus. It is believed that radioactive decay of uranium and thorium in the interior of the planets' is not sufficient to account for the abundance of helium observed. Alpha particles in the solar wind are suggested to be an additional source of helium, especially at Mars. Recent hybrid simulations show that as much as 30We use ion data from the ASPERA-3 and ASPERA-4 instruments on Mars and Venus Express to estimate how efficient solar wind alpha particles are captured in the atmospheres of the two planets.

Stenberg, Gabriella; Barabash, Stas; Nilsson, Hans; Fedorov, A.; Brain, David; André, Mats

316

Design of wind-solar and pumped-storage hybrid power supply system  

Microsoft Academic Search

To overcome the inherent defects in wind-solar hybrid system: power generation and electricity load's imbalance because of uncertainty of resources. this article aiming at XJ Group's project design of wind-solar hybrid power supply system, by way of pumped-storage to replace the battery of wind-solar hybrid power supply system, this method can effectively overcome above problems. Wind-solar and pumped-storage hybrid power

Ruisheng Lil; Bingxin Wul; Xianwei Lil; Fengquan Zhoul; Yanbin Li

2010-01-01

317

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

318

Venus and Mars Obstacles in the Solar Wind  

NASA Astrophysics Data System (ADS)

Comparisons of the magnetosheaths of Venus and Mars contrast the relative simplicity of the Venus solar wind interaction and the ``Jekyll and Hyde" nature of the Mars interaction. Magnetometer observations from Mars Global Surveyor during the elliptical science phasing orbits and Pioneer Venus Orbiter in its normally elliptical orbit are compared, with various models used to compensate for the different near-polar periapsis of MGS and near-equator periapsis of PVO. Gasdynamic or MHD fluid models of flow around a conducting sphere provide a remarkably good desciption of the Venus case, and the Mars case when the strong Martian crustal magnetic anomalies are in the flow wake. In the case of Venus, large magnetosheath field fluctuations can be reliably tied to occurrence of a subsolar quasiparallel bow shock resulting from a small interplanetary field cone angle (angle between flow and field) upstream. At Mars one must also contend with such large fluctuations from the bow shock, but also from unstable solar wind proton distributions due to finite ion gyroradius effects, and from the complicated obstacle presented to the solar wind when the crustal magnetic anomalies are on the ram face or terminator. We attempt to distinguish between these factors at Mars, which are important for interpretation of the upcoming NOZOMI and Mars Express mission measurements. The results also provide more insights into a uniquely complex type of solar system solar wind interaction involving crustal fields akin to the Moon's, combined with a Venus-like ionospheric obstacle.

Luhmann, J. G.; Mitchell, D. L.; Acuna, M. H.; Russell, C. T.; Brecht, S. H.; Lyon, J. G.

2000-10-01

319

Radio interferometer observations of turbulence in the inner solar wind  

SciTech Connect

Measurements can be made of Very Long Baseline Interferometer (VLBI) phase scintillations due to plasma turbulence in the solar corona and solar wind. These measurements provide information on the spectrum and intensity of density fluctuations with scale sizes of a few hundred to several thousand kilometers. If we model the spatial power spectrum of the density fluctuations as P{sub {delta}}{sub n}(q)=C{sub N}{sup 2}q{sup -{alpha}}, where q is the spatial wavenumber, these observations yield both {alpha} and the path-integrated value of C{sub N}{sup 2}. The recently completed Very Long Baseline Array (VLBA) is capable of making such measurements over the heliocentric distance range from a few solar radii to 60 solar radii and beyond. This permits the determination, with the same technique and instrument, of the radial evolution of turbulent characteristics, as well as their dependence on solar wind transients, sector structure, etc. In this paper we present measurements of 16 sources observed at a wide range of solar elongations and at different times. These observations show that the coefficient C{sub N}{sup 2} depends on heliocentric distance as approximately C{sub N}{sup 2}{proportional_to}(R/R{sub {center_dot}}){sup -3.7}. The radio derived power spectral characteristics are in agreement with in situ measurements by the Helios spacecraft for regions of slow solar wind, but fast solar wind does not have large enough density fluctuations to account for the magnitude of the observed scintillations. The observed radial dependence is consistent with a Wentzel-Kramers-Brillouin (WKB)-type evolution of the turbulence with heliocentric distance.

Spangler, S. R.; Sakurai, T.; Coles, W. A.; Grall, R. R.; Harmon, J. K. [Department of Physics and Astronomy, University of Iowa, Iowa City (United States); E.C.E. Department, University of California at San Diego, La Jolla (United States); Arecibo Observatory, Arecibo (Puerto Rico)

1996-07-20

320

The Economic Analysis of Wind Solar Hybrid Power Generation System in Villa  

Microsoft Academic Search

In order to solve the electricity problem of residents in the single-family villa, while for the effective use of solar and wind energy, the paper give a run analysis of wind solar hybrid power generation system in villa, which is utilized to replace the using of electricity from state grid. The results showed that the off-grid wind solar hybrid power

Wang Jinggang; Gao Xiaoxia; Du Hongbiao

2009-01-01

321

Reliability and cost\\/worth evaluation of generating systems utilizing wind and solar energy  

Microsoft Academic Search

The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and\\/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become

Bagen

2005-01-01

322

Response of the midtail electric field to enhanced solar wind energy input  

Microsoft Academic Search

We study the response of midtail plasma and field parameters to enhanced solar wind electric field input for two substorm intervals on November 22, 1995. The solar wind input signatures were quite different for these two substorms, which had major Pi2 onsets at 1108 and 1502 UT. The solar wind input for the 1108 UT substorm had a short timescale

R. Nakamura; L. F. Bargatze; T. Mukai; T. Nagai; K. B. Baker; M. R. Hairston; P. H. Reiff; A. A. Petrukovich; M. Nozdrachev; O. A. Troshichev

1999-01-01

323

An assessment of solar and wind energy from the electric utility view point  

Microsoft Academic Search

The paper discusses briefly the prospects of several technologies for supplementing energy resources in the coming decade, including wind energy, biomass, solar thermal conversion, ocean thermal gradient systems, and photovoltaic conversion, and then gives an assessment of solar and wind energy economics. Break-even capital cost limits for solar and wind energy systems have been calculated for different fuel costs, interest

R. Ramakumar; W. L. Hughes

1975-01-01

324

Interaction of a nonuniform solar wind with the local interstellar medium  

Microsoft Academic Search

Results from a fully time dependent three-dimensionM gasdynamic model of the interaction of the solar wind with the local interstellar medium are presented. Both subsonic and supersonic interstellar winds are considered, while the mediating effects of interstellar neutrals, magnetic fields, and cosmic rays are ignored. In accord with solar minimum observations by Ulysses, the solar wind properties are assumed to

H. L. Pauls; G. P. Zank

1996-01-01

325

NUMERICAL SIMULATION OF FLARE-GENERATED DISTURBANCES IN THE SOLAR WIND  

Microsoft Academic Search

The propagation of flare-generated shock waves through the solar wind is examined using numerical solutions of the time-dependent hydrodynamic equations. These solutions are valid for all shock strengths, including the intermediate values that have been observed in the solar wind, and take into account the variation of the properties of the ambient solar wind. The entire range of time scales

A. J. Hundhausen; R. A. Gentry

1969-01-01

326

Using Pickup Ions to Determine the Solar Wind Speed at the Cassini Spacecraft  

Microsoft Academic Search

We calculate solar wind speeds at the Cassini spacecraft when it's in the solar wind, as it was during the cruise to Saturn and as it is for a substantial portion of its orbits around Saturn. This benefits magnetospheric studies by providing a key measure of the upstream conditions. Similarly, a solar wind speed monitor at 9 AU (and during

M. E. Hill; D. C. Hamilton; G. Gloeckler; S. M. Krimigis; D. G. Mitchell; J. T. Steinberg; F. J. Crary

2005-01-01

327

Feasibility study of a solar and wind powered desalinization device (SOWIDE). Final report  

Microsoft Academic Search

The scope, need and feasibility of a solar-wind desalinization (SOWIDE) system is examined. A climatological study shows the scope and need where a water deficit, a saline source and solar and wind power coincide. Representative stations around the globe serve as examples. When climatological data are used, relatively few locations meet all requirements. Optimization of wind and solar energy through

M. Garstang; D. C. David; J. W. Snow

1980-01-01

328

Feasibility study of a solar-and-wind-powered desalinization device (SOWIDE). Final report  

Microsoft Academic Search

The scope, need and feasibility of a solar-wind desalinization (SOWIDE) system is examined. A climatological study shows the scope and need where a water deficit, a saline source and solar and wind power coincide. Representative stations around the globe serve as examples. When climatological data are used, relatively few locations meet all requirements. Optimization of wind and solar energy through

M. Garstang; D. C. David; J. W. Snow

1980-01-01

329

The critical solar wind pressure for IMF penetration into the Venus ionosphere  

Microsoft Academic Search

Early observations and simulations have revealed that the occurrence of IMF penetration into the Venus ionosphere depends on the upstream solar wind pressure, and that IMF is transported into the ionosphere by the downward convection when the solar wind dynamic pressure is relatively large. In this paper, we investigated the critical solar wind pressure for the IMF penetration, by using

H. Jin; K. Maezawa; T. Mukai

2008-01-01

330

Optimal design and techno-economic analysis of a hybrid solar–wind power generation system  

Microsoft Academic Search

Solar energy and wind energy are the two most viable renewable energy resources in the world. Good compensation characters are usually found between solar energy and wind energy. This paper recommend an optimal design model for designing hybrid solar–wind systems employing battery banks for calculating the system optimum configurations and ensuring that the annualized cost of the systems is minimized

Hongxing Yang; Zhou Wei; Lou Chengzhi

2009-01-01

331

Feasibility of hybrid (wind + solar) power systems for Dhahran, Saudi Arabia  

Microsoft Academic Search

Hourly mean wind-speed and solar radiation data for the period 1986–1993 [except the years 1989 (some data is missing) and 1991 (Gulf War)] recorded at the solar radiation and meteorological monitoring station, Dhahran (26° 32? N, 50° 13? E), Saudi Arabia, have been analyzed to report the monthly variation of wind speed and solar radiation, probability distribution of wind speed

M. A. Elhadidy; S. M. Shaahid

1999-01-01

332

SWERA - SOLAR AND WIND ENERGY RESOURCE ASSESSMENT - REGIONAL AGENCY FOR LATIN AMERICA  

Microsoft Academic Search

SWERA - Solar and Wind Energy Resource Assessment is a project financed by UNEP, with co-financing by GEF, in the area of renewable energies, and more specifically solar and wind energy. The project includes the efforts of several countries, but is primarily directed to developing countries. The project will bring together high quality information on solar and wind energy resources

Enio Bueno Pereira; Fernando R. Martins; Silvia V. Pereira; Sergio Colle; Samuel L. Abreu; Alfredo Curbelo Alonso; Tom Hamlin

333

Solar wind time history contribution to the day-of-year variation in geomagnetic activity  

Microsoft Academic Search

The day-of-year (DOY) variation in the average value of a solar wind driver of geomagnetic activity has been shown to explain only a minority of the observed amplitude of DOY variation in geomagnetic activity. The proxies for solar wind driving used to show this are averages of a solar wind measurement in the same hour or 3-hour interval as the

R. S. Weigel

2007-01-01

334

Synoptic maps of solar wind parameters from in situ spacecraft observations  

Microsoft Academic Search

Solar wind observations from the Interplanetary Monitoring Platform-8 (IMP-8) and Pioneer Venus Orbiter (PVO) spacecraft from 1982 until 1988 are combined to construct synoptic maps of solar wind parameters near 1 AU. Each map consists of 6 months of hourly averaged solar wind data, binned by heliographic latitude and Carrington longitude and projected back to the Sun. These maps show

P. R. Gazis

1995-01-01

335

Martian Magnetic Topology: Evaluation of Crustal Magnetization and Solar Wind Interaction Models Using MGS MAG Data  

Microsoft Academic Search

Results from the MAG\\/ER experiment aboard Mars Global Surveyor indicate that the magnetic topology near Mars is governed both by the interaction of the solar wind with the Martian obstacle and by regions of magnetized crust. Consequently, the arrangement of magnetic field lines near Mars depends upon solar wind conditions, solar wind magnetic field orientation, and planetary local time. At

D. A. Brain; F. Bagenal; D. H. Crider; M. H. Acuna; J. E. Connerney

2001-01-01

336

A note on using thermally driven solar wind models in MHD space weather simulations  

Microsoft Academic Search

One of the challenges in constructing global magnetohydrodynamic (MHD) models of the inner heliosphere for, e.g., space weather forecasting purposes, is to correctly capture the acceleration and expansion of the solar wind. In many current models, the solar wind is driven by varying the polytropic index so that a desired heating is obtained. While such schemes can yield solar wind

Jens Pomoell; Rami Vainio

2011-01-01

337

The main features of solar wind plasma correlations of importance to space weather strategy  

Microsoft Academic Search

In this work solar wind measurements from several spacecraft were used to investigate the correlations of solar wind plasma parameters. These results provide a test of the concept of predicting space weather by monitoring the condition of the solar wind at a large distance (up to 230Re, the L1 point) upstream from the Earth.We compared the ion flux and bulk

Peter Dalin; Georgy Zastenker; Karolen Paularena; John Richardson

2002-01-01

338

The main features of solar wind plasma correlations of importance to space weather strategy  

Microsoft Academic Search

In this work solar wind measurements from several spacecraft were used to investigate the correlations of solar wind plasma parameters. These results provide a test of the concept of predicting space weather by monitoring the condition of the solar wind at a large distance (up to 230Re, the L1 point) upstream from the Earth. We compared the ion 4ux and

Peter Dalina; Georgy Zastenker; Karolen Paularena; John Richardson

339

Mean wind forces on parabolic-trough solar collectors  

SciTech Connect

The purpose of this study was to investigate characteristics of mean wind loads produced by airflow in and around several configurations of parabolic trough solar collectors with and without a wind fence. Four basic parabolic shapes were investigated as single units and one shape was studied as part of several array fields. One 1:25 scale model of each parabolic shape was constructed for mounting on a force balance to measure two forces and three moments. The effects of several dominant variables were investigated in this study: wind-azimuth (or yaw), trough elevation (or pitch) angle, array field configuration, and protective wind fence characteristics. All measurements were made in a boundary-layer flow developed by the meteorological wind tunnel at the Fluid Dynamics and Diffusion Laboratory of Colorado State University. Results are presented and discussed. (WHK)

Peterka, J.A.; Sinau, J.M.; Cermak, J.E.

1980-05-01

340

On the Role of Interchange Reconnection in the Generation of the Slow Solar Wind  

Microsoft Academic Search

The heating of the solar corona and therefore the generation of the solar wind, remain an active area of solar and heliophysics\\u000a research. Several decades of in situ solar wind plasma observations have revealed a rich bimodal solar wind structure, well\\u000a correlated with coronal magnetic field activity. Therefore, the reconnection processes associated with the large-scale dynamics\\u000a of the corona likely

J. K. Edmondson

341

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

342

Propagation of solar generated disturbances through the solar wind critical points: One-dimensional analysis  

Microsoft Academic Search

We investigate the proper method for mathematically simulating the formation of an interplanetary disturbance (IPD) in the subsonic, sub-Alfvénic region near the solar surface within the constraints of one-dimensional hydrodynamic and magnetohydrodynamic (MHD) analyses. We then numerically simulate the subsequent propagation of the IPD through the solar wind critical points in the equatorial plane to the outer corona. We show

R. S. Steinolfson; M. Dryer

1984-01-01

343

Solar flares and solar wind helium enrichments: July 1965–July 1967  

Microsoft Academic Search

It has previously been suggested that the very high relative abundances of helium occasionally observed in the solar wind mark the plasma accelerated by major solar flares. To confirm this hypothesis, we have studied the 43 spectra with He\\/H ? 15% that were observed among 10300 spectra collected by Vela 3 between July 1965–July 1967. The 43 spectra were distributed

J. Hirshberg; S. J. Bame; D. E. Robbins

1972-01-01

344

A unified model of solar energetic particle transport in structured solar wind  

Microsoft Academic Search

Solar energetic particle (SEP) fluxes, after their propagation from the particles' source to the Earth's orbit, depend on the state of solar wind, which is known to be highly variable in both time and space. Commonly used SEP transport models are based on the assumption of the standard interplanetary magnetic field, which would be the case for a uniform, steady

L. Kocharov; V. J. Pizzo; D. Odstrcil; R. D. Zwickl

2009-01-01

345

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

346

Enabling Technologies for High Penetration of Wind and Solar Energy  

SciTech Connect

High penetration of variable wind and solar electricity generation will require modifications to the electric power system. This work examines the impacts of variable generation, including uncertainty, ramp rate, ramp range, and potentially excess generation. Time-series simulations were performed in the Texas (ERCOT) grid where different mixes of wind, solar photovoltaic and concentrating solar power provide up to 80% of the electric demand. Different enabling technologies were examined, including conventional generator flexibility, demand response, load shifting, and energy storage. A variety of combinations of these technologies enabled low levels of surplus or curtailed wind and solar generation depending on the desired penetration of renewable sources. At lower levels of penetration (up to about 30% on an energy basis) increasing flexible generation, combined with demand response may be sufficient to accommodate variability and uncertainty. Introduction of load-shifting through real-time pricing or other market mechanisms further increases the penetration of variable generation. The limited time coincidence of wind and solar generation presents increasing challenges as these sources provide greater than 50% of total demand. System flexibility must be increased to the point of virtually eliminating must-run baseload generators during periods of high wind and solar generation. Energy storage also becomes increasingly important as lower cost flexibility options are exhausted. The study examines three classes of energy storage - electricity storage, including batteries and pumped hydro, hybrid storage (compressed-air energy storage), and thermal energy storage. Ignoring long-distance transmission options, a combination of load shifting and storage equal to about 12 hours of average demand may keep renewable energy curtailment below 10% in the simulated system.

Denholm, P.

2011-01-01

347

Hemispheric Asymmetries in the Polar Solar Wind Observed by Ulysses near the Minima of Solar Cycles 22 and 23  

NASA Astrophysics Data System (ADS)

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 ~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 ~36°S-60°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.; Pogorelov, N. V.

2013-05-01

348

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

349

STEREO's in-situ perspective on the solar minimum solar wind structure  

Microsoft Academic Search

STEREO multipoint measurements of the solar wind structure with the IMPACT and PLASTIC investigations, near Earth but off the Sun-Earth line, allow its sources and structure to be examined at solar minimum when such studies are particularly straightforward. With the aid of 3D models of the heliosphere available at the CCMC, we map the in-situ observations to their solar sources

J. G. Luhmann; D. Larson; P. Schroeder; C. O. Lee; J. Sauvaud; M. H. Acuna; A. B. Galvin; C. T. Russell; L. Jian; C. N. Arge; D. Odstrcil; P. Riley; R. A. Howard; M. Aschwanden; P. MacNeice; A. Chulaki

2007-01-01

350

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

351

A Model for the Sources of the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

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 at the open-closed field boundary layer, but it also has large angular width, up to 40 degrees. 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 calculate with high numerical resolution, the quasi-steady solar wind and magnetic field for a Carrington rotation centered about the August 1, 2008 total solar eclipse. Our numerical results demonstrate that, at least for this time period, a web of separatrices (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. This work was supported, in part, by the NASA HTP, TR&T and SR&T programs.

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

2010-05-01

352

Assessment of existing studies of wind loading on solar collectors  

SciTech Connect

In developing solar collectors, wind loading is the major structural design consideration. Wind loading investigations have focused on establishing safe bounds for steady state loading and verifying rational but initial and conservative design approaches for the various solar collector concepts. As such, the effort has been very successful, and has contributed greatly to both the recognition and qualitative understanding of many of the physical phenomena involved. Loading coefficients corresponding to mean wind velocities have been derived in these prior studies to measure the expected structural loading on the various solar collectors. Current design and testing procedures for wind loading are discussed. The test results corresponding to numerous wind tests on heliostats, parabolic troughs, parabolic dishes, and field mounted photovoltaic arrays are discussed and the applicability of the findings across the various technologies is assessed. One of the most significant consistencies in the data from all the technologies is the apparent benefit provided by fences and field shielding. Taken in toto, these data show that load reductions of three or possibly more seem feasible, though a more thorough understanding of the phenomena involved must be attained before this benefit can be realized. It is recommended that the required understanding be developed to take advantage of this benefit and that field tests be conducted to correlate with both analyses and tests.

Murphy, L. M.

1981-02-01

353

Modeling and Simulation for Solar and Wind Energy  

Microsoft Academic Search

The application of Modeling and Simulation in the design and verification process for Renewable and Green Energy is the focus of this paper. The scope will be solar and wind energy. First the role of electrical energy is discussed and second samples are given where modeling and simulation can be applied. A brief discussion is given on the model of

Peter van Duijsen; Pavol Bauer; Frank Chen

2006-01-01

354

A space motor using solar wind energy (magnetic particle sail)  

Microsoft Academic Search

A space motor that uses solar wind for spacecraft thrust and electric energy production is described. Since the particle flow density is not great, protons and electrons are collected with a powerful magnet and their consequential reflection, absorption, or acceleration are used to create thrust. If used in conjuction with a superconductor circuit the motor can reach a thrust of

A. A. Bolonkin

1992-01-01

355

Principles of designing solar- and wind-energy systems  

Microsoft Academic Search

A systems analysis approach is proposed for planning and designing solar- and wind-energy systems whose operation involves natural, engineering, and human factors. Such relatively complex systems are characterized by the presence of control, functional objectives, a hierarchical system structure, and a continuously changing state of subsystems and elements. Computer-aided solutions to the problems of optimizing the system structure, the system

R. B. Salieva

1976-01-01

356

Nonlinear Development of Shocklike Structure in the Solar Wind  

Microsoft Academic Search

We report first in situ multispacecraft observations of nonlinear steepening of compressional pulses in the solar wind upstream of Earth's bow shock. The magnetic field of a compressional pulse formed at the upstream edge of density holes is shown to suddenly break and steepen into a shocklike structure. During the early phase of development thermalization of ions is insignificant. Substantial

E. Lee; G. K. Parks; M. Wilber; N. Lin

2009-01-01

357

Hybrid code simulations of the solar wind interaction with Pluto  

Microsoft Academic Search

Pluto's low gravity implies that the atmosphere is only weakly bound and that significant hydrodynamic outflow can exist. Though surface spectroscopy of Pluto has revealed methane frost, the dominant escaping neutral gas is thought to be N2. These escaping neutrals are photoionized, and the heavy ions (N2+) move away from Pluto in the direction perpendicular to the solar wind flow

P. A. Delamere

2009-01-01

358

New Observations of Solar Wind Dissipation across Earth's Bow Shock  

Microsoft Academic Search

Early solar wind (SW) observations showed ion distributions in the vicinity of Earth's bow shock included a secondary beam that was interpreted as SW ions reflected off the bow shock. The current theory of SW thermalization involves instabilities driven by the relative motion of the reflected ions and SW. We present new observations of ions measured by 3D plasma instruments

George Parks; E. Lee; A. Teste; N. Lin; M. Wilber; I. Dancouras; H. Reme; S. Fu; J. Cao

2010-01-01

359

Characteristics of the solar wind controlled auroral emissions  

Microsoft Academic Search

We performed a high-time resolution (5 min) correlative study of the energy deposition rate in the northern auroral zone with the concurrent solar wind plasma and interplanetary magnetic field (IMF) observations for a 4 month period from March 30 to July 29, 1996. Auroral power, inferred by auroral emissions, was derived from images acquired by the ultraviolet imager (UVI) on

K. Liou; P. T. Newell; C.-I. Meng; M. Brittnacher; G. Parks

1998-01-01

360

Pickup ions in the unshocked solar wind at Comet Halley  

Microsoft Academic Search

Data obtained by the Tunde-M experiment aboard the Vega 1 spacecraft indicate that the energetic ion flux begins to increase at a distance of about 10 to the 7th km outside Halley's bow shock, with a number of large enhancements superimposed on the general flux level. The energy spectra of ions were determined in the solar wind reference frame by

K. Kecskemety; T. E. Cravens; V. V. Afonin; G. Erdos; E. G. Eroshenko; L. Gan; T. I. Gombosi; K. I. Gringauz; E. Keppler; I. N. Klimenko; R. Marsden; A. P. Remizov; A. K. Richter; W. Riedler; K. Schwingenschuh; A. J. Somogyi; K. Szego; M. Tatrallyay; A. Varga; M. I. Verigin; K.-P. Wenzel

1989-01-01

361

Validation of Model Forecasts of the Ambient Solar Wind (Invited)  

Microsoft Academic Search

Independent and automated validation is a vital step in the progression of models from the research community into operational forecasting use. In this paper we describe a program in development at the CCMC to provide just such a comprehensive validation for models of the ambient solar wind in the inner heliosphere. We have built upon previous efforts published in the

P. J. MacNeice; M. Hesse; M. M. Kuznetsova; L. Rastaetter; A. Taktakishvili

2009-01-01

362

Spacecraft observations of solar wind turbulence: an overview  

Microsoft Academic Search

Spacecraft measurements in the solar wind offer the opportunity to study magnetohydrodynamic (MHD) turbulence in a collisionless plasma in great detail. We review some of the key results of the study of this medium: the presence of large amplitude Alfvén waves propagating predominantly away from the Sun; the existence of an active turbulent cascade; and the presence of intermittency similar

T. S. Horbury; M. A. Forman; S. Oughton

2005-01-01

363

Reproducing spacecraft measurements of magnetic correlations in the solar wind  

Microsoft Academic Search

Analytical models for magnetic turbulence are an important ingredient in the theory of field line wandering and cosmic ray diffusion. In previous investigations, a so-called slab\\/2D model has been used. In the present article, we develop a more general analytical model for magnetic turbulence. This model is then compared with solar wind observations. We investigate numerically the possibility to explain

B. Weinhorst; A. Shalchi

2010-01-01

364

Gasdynamics of the solar wind interaction with the interstellar medium  

Microsoft Academic Search

A survey of the present-day situation in gasdynamical models of solar wind interaction with the local interstellar medium is presented. A role of these models in interpreting a number of observed physical phenomena is investigated. Experimental data and possible observations are considered from the viewpoint of their interpretation on the basis of theoretical models. Our attention is concentrated on the

V. B. Baranov

1990-01-01

365

Multielement RIMS Analysis of Genesis Solar Wind Collectors  

Microsoft Academic Search

The samples of Solar Wind (SW) delivered by the NASA Genesis mission, present significant challenges for surface analytical techniques, in part due to severe terrestrial contamination of the samples on reentry, in part due to the ultra-shallow and diffused ion implants in the SW collector materials. We are performing measurements of metallic elements in the Genesis collectors using Resonance Ionization

I. V. Veryovkin; C. E. Tripa; A. V. Zinovev; B. V. King; M. J. Pellin; D. S. Burnett

2009-01-01

366

Interaction of the solar wind with the moon  

Microsoft Academic Search

During its orbit about the Earth, the Moon is located in the interplanetary medium or the geomagnetosheath-geomagnetotail formed by the solar wind interaction with Earth. In the tail, no evidence is found for a lunar magnetic field limiting the magnetic moment to 1020 G . cm3 (< 10-6 of that of the Earth). In the interplanetary medium, no evidence exists

Norman F. Ness

1971-01-01

367

Reexamination of rotational and tangential discontinuities in the solar wind  

Microsoft Academic Search

ISEE 3 magnetic field and proton data are used to study the properties of rotational and tangential discontinuities in the solar wind. A Sonnerup-Cahill minimum variance analysis of the magnetic field data is used to determine the direction of the normal to each discontinuity. The discontinuities are then classified as rotational (RD), tangential (TD), or either (ED), depending on the

M. Neugebauer; D. R. Clay; B. E. Goldstein; B. T. Tsurutani; R. D. Zwickl

1984-01-01

368

Air emissions due to wind and solar power.  

PubMed

Renewables portfolio standards (RPS) encourage large-scale deployment of wind and solar electric power. Their power output varies rapidly, even when several sites are added together. In many locations, natural gas generators are the lowest cost resource available to compensate for this variability, and must ramp up and down quickly to keep the grid stable, affecting their emissions of NOx and CO2. We model a wind or solar photovoltaic plus gas system using measured 1-min time-resolved emissions and heat rate data from two types of natural gas generators, and power data from four wind plants and one solar plant. Over a wide range of renewable penetration, we find CO2 emissions achieve approximately 80% of the emissions reductions expected if the power fluctuations caused no additional emissions. Using steam injection, gas generators achieve only 30-50% of expected NOx emissions reductions, and with dry control NOx emissions increase substantially. We quantify the interaction between state RPSs and NOx constraints, finding that states with substantial RPSs could see significant upward pressure on NOx permit prices, if the gas turbines we modeled are representative of the plants used to mitigate wind and solar power variability. PMID:19238948

Katzenstein, Warren; Apt, Jay

2009-01-15

369

Solar Wind Heating: Critical Tests of a Turbulence Theory  

Microsoft Academic Search

We review observations of solar wind heating in the outer heliosphere as measured by the Voyager 2 and Pioneer 11 spacecraft and described previously by a theory of pickup ion wave excitation and turbulent transport. That theory was most recently applied to observations by Smith et al. [2001] and with significant revision of the pickup proton component by Isenberg et

C. W. Smith; P. A. Isenberg; W. H. Matthaeus; J. D. Richardson

2004-01-01

370

The cometary atmosphere and its interaction with the solar wind  

Microsoft Academic Search

The present state of both our knowledge and our understanding of cometary atmospheres and their interactions with the solar wind is critically reviewed. Following the introduction (section 1) the spectrophotometry of the cometary atmosphere and the tail is reviewed in section 2. The existing, rather fragmentary, knowledge about atmospheric abundances and the production rates of various molecular species is given

D. A. Mendis; Harry L. F. Houpis

1982-01-01

371

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

372

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

373

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

374

Solar-wind hybrid power for rural Indian cell sites  

Microsoft Academic Search

Rapid expansion of rural cell phone subscriber base in India is facing some tough challenges in getting the stable back up power for cell sites. Grid power availability is very poor and use of diesel generator is turning out to be expensive with heavy fuel and transportation costs. Use of alternative energy provides a long term viable solution. Solar-wind hybrid

A. Naikodi

2010-01-01

375

Solar Wind Control of Hot Plasma Injections in Saturn's Magnetosphere  

NASA Astrophysics Data System (ADS)

The Ion and Neutral Camera (INCA) on board the Cassini spacecraft have obtained global energetic neutral atom (ENA) images of the hot plasma of Saturn's magnetosphere since July 2004. INCA obtains ENA images in the ~3-200 keV/nuc of protons and O+. The typical observations show hot plasma distributed roughly between 6 to 30 R_S orbiting the planet at a period around the 10h45min rotation period depending on energy and species. However, some observations show how ENA intensity builds up on the nightside during intervals longer than the rotation period which indicates a gradual source of plasma. The intervals are often ended by a dramatic ENA intensification followed by a rotation of the newly injected plasma around the planet. We have selected a few of such intervals when Cassini was in the solar wind and could obtain solar wind parameters and simulataneous ENA image sequences. We use the Magnetic Field Experiment (MFE), the Cassini Charge Energy Mass Spectrometer (CHEMS), and the Cassini Plasma Spectrometer Subsystem (CAPS) to study the IMF, solar wind speed and density during these events and find that Saturn's magnetospheric activity most likely depends more on solar wind pressure than magnetic field orientation.

Brandt, P. C.; Mitchell, D. G.; Rymer, A.; Hill, M.; Paranicas, C. P.

2006-12-01

376

Review of Solar Wind Heating: Observations and Theory  

NASA Astrophysics Data System (ADS)

Observations from Helios, Pioneer 11, and the Voyager 1/2 spacecraft provide clear evidence for heating of the solar wind protons. Several sources of energy to drive the heating are now recognized, from residual waves originating in the low solar corona that may be at least partially responsible for heating the inner heliosphere, to wind shear and shocks that provide energy to heat the solar wind inside 10 to 20 AU, to waves generated by newborn interstellar pickup ions that heat the outer heliosphere. These processes imply the need for a theory to convert energy associated with large-scale structures into the small-scale fluctuations that can interact with the protons via familiar plasma processes. We will briefly review such a theory and test it against the observations. We will examine several formalisms for computing an inferred turbulent heating rate from magnetic field measurements and compare their predictions with observations. We will also review past and recent attempts to identify the plasma processes responsible for converting magnetic energy into heat. This involves studying the so-called dissipation range and resolving its properties in comparison with the more familiar inertial range of interplanetary magnetic fluctuations. While this will not lead to a final decision on what plasma processes heat the solar wind, it will provide a list of diagnostics and observations that constrain the discussion.

Smith, C. W.

2004-12-01

377

Magnetic flux tube evolution in solar wind anisotropic magnetic turbulence  

Microsoft Academic Search

The magnetic turbulence in the solar wind causes a magnetic field line transport that is reflected in the propagation in space of charged particles. Assuming a small localized source, the distribution in space of energetic particles is determined, in part, by the shape of the magnetic flux tube. The spatial evolution of a magnetic flux tube is studied here by

G. Zimbardo; P. Pommois; P. Veltri

2004-01-01

378

Electromagnetic proton\\/proton instabilities in the solar wind: Simulations  

Microsoft Academic Search

Proton velocity distributions in the high-speed solar wind are sometimes observed as two components of approximately equal temperature with an average relative drift velocity parallel to the background magnetic field. This relative drift gives rise to several proton\\/proton instabilities; for representative parameters, linear Vlasov theory demonstrates that the electromagnetic modes most likely to grow are a magnetosonic instability and an

William Daughton; S. Peter Gary; Dan Winske

1999-01-01

379

Seasonal dependence and solar wind control of transpolar arc luminosity  

Microsoft Academic Search

The influence of the solar wind and the interplanetary magnetic field (IMF) on the luminosity of transpolar arcs (TPAs) is examined by taking into account seasonal effects. The study focuses on those transpolar arcs that appear after an IMF B y sign change during steady northward IMF. It includes 21 northern hemisphere events identified in a previous study from global

A. Kullen; J. A. Cumnock; T. Karlsson

2008-01-01

380

Seasonal dependence and solar wind control of transpolar arc luminosity  

Microsoft Academic Search

The influence of the solar wind and the interplanetary magnetic field (IMF) on the luminosity of transpolar arcs (TPAs) is examined by taking into account seasonal effects. The study focuses on those transpolar arcs that appear after an IMF By sign change during steady northward IMF. It includes 21 northern hemisphere events identified in a previous study from global UV

A. Kullen; J. A. Cumnock; T. Karlsson

2008-01-01

381

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

382

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

383

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

384

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

385

Ion escape from Mars as a function of solar wind conditions: A statistical study  

Microsoft Academic Search

The influence of solar EUV and solar wind conditions on ion escape at Mars is investigated using ion data from the Aspera-3 instrument on Mars Express, combined with solar wind proxy data obtained from the Mars Global Surveyor (MGS) spacecraft. A solar EUV flux proxy based on data from the Earth position, scaled and shifted in time for Mars, is

Hans Nilsson; Ella Carlsson; David A. Brain; Masatoshi Yamauchi; Mats Holmström; Stas Barabash; Rickard Lundin; Yoshifumi Futaana

2010-01-01

386

Statistical Properties of the Solar Wind and IMF at 1 AU  

Microsoft Academic Search

During the declining phase of the solar cycle the evolution of the solar magnetic field produces large regions of unipolar magnetic field that create coronal holes and are the sources of high speed solar wind streams. These streams overtake and interact with slow solar wind emitted from the equatorial belt of closed magnetic field lines. These interaction regions corotate (CIR)

R. L. McPherron

2006-01-01

387

Drag of the Venusian Atmosphere by Solar Wind  

NASA Astrophysics Data System (ADS)

One of the more efficient mechanisms of volatiles lost in the non-magnetic planets is its drag by solar wind. In this study it is explored this type of erosion for Venus and it is obtained some numerical results leaving from plausible models of degassing and drag. The obtained results from this study are: Venus had degassed, in all its history, of the order of 286.87 TAM of volatiles (1 TAM = 1 Terrestrial Atmospheric Mass = 5.28x1018 kg), i.e., 1.515x1021 kg. Since current mass of the planet's atmosphere is 89.92 TAM the volatiles mass that Venus has lost in the same period is of the order of 196.95 TAM, i.e., 1.04x1021 kg. The drag capacity of the solar wind in the first Ga of the planet's life was very large such that it could drag of the order of 108 TAM if Venus had have it. Degasification did not could compete with the drag that maintains the planet free of volatiles and at the solar wind flowing directly in surface. After this first Ga in the following 3.6 Ga the drag capacity of the solar wind reduced drastically and then the solar wind only could drag at the most of the order of 88 TAM of volatiles. The mass dragged by the solar wind in all the history of Venus fluctuate between 70 and 200 TAM, i.e., between 3.7x1020 kg and 1.06x1021 kg. In last 3.6 Ga the dragged mass by solar wind fluctuate between 11 and 61 TAM and y the last 500 Ma between 0.32 and 0.41 TAM. The lost by other mechanisms fluctuate between 1 and 130 TAM. For the scenarios of more loss the usual mechanisms could not explain the quantity of lost volatiles, for this it is proposed the hypotheses of the Great Impact (the collision of Venus with a body larger than Moon 500 Ma ago) this hypotheses not only explain the lost of volatiles but also other aspects do not understand of Venus, like its slowly and retrograde rotation and the renovation of all its surface 500 Ma ago.

Durand-Manterol, H.

2006-12-01

388

Variations in Antarctic Mesospheric winds during Solar Proton Events  

NASA Astrophysics Data System (ADS)

During March 2012 a solar proton event (SPE) occurred that coincided exactly with a large change in the neutral wind field in the upper mesosphere above Rothera station on the Antarctic Peninsula. This change appeared as an enhancement in the tidal magnitude in both the meridional and zonal winds. Rothera is well outside the expected cut-off region for very energetic solar protons and consequently the change to the neutral wind field is assumed to be non-local in nature; observations from higher latitude stations are inconclusive due to the attenuation of the radar signal during the SPE. We examine past events in the lifetime of the Rothera radar (2002-current) and show similar responses as well as clear differences during other SPE. We speculate on the underlying mechanism with reference to the chemical and radiative heating effects of energetic protons on the middle atmosphere.

Kavanagh, Andrew; Jarvis, Martin

2013-04-01

389

Alfvénic Turbulence and the Acceleration of the Fast Solar Wind  

NASA Astrophysics Data System (ADS)

Alfvenic turbulence is usually invoked and used in many solar wind models (Isenberg & Hollweg 1982, Tu et al. 1984, Hu et al. 2000, Li 2003, Isenberg 2004) as a process responsible for the transfer of energy released at large scales in the photosphere towards small scales in the corona, where it is dissipated. Usually an initial spectrum is prescribed since its closest constraint is given by Helios measurements at 0.3 AU. With this work we intend to study the efficiency of the reflection as a driver for the nonlinear interactions of Alfven waves, the eventual development of a turbulent spectrum and its evolution in the highly stratified solar atmosphere inside coronal holes. We start imposing an upcoming flux of Alfven waves in a limited range of perpendicular wave numbers, at the base of the corona. Open boundary conditions allow the reflected waves to leave the domain form below and to be advected by the solar wind outside the top boundary. The nonlinear interaction in planes perpendicular to that of propagation (assumed to be radial) are treated with a 2D shell model, so that large Reynolds numbers are reached. Continuous interactions of counter propagating waves form a turbulent spectrum in the low corona, before the sonic point, in very short timescales (compared to the propagation timescales). Both the location and the value of the maximum of the dissipation (per unit mass) scale with the rms amplitude of the velocity fluctuations at the coronal base (delta u), while they are less sensitive to the frequency of the input flux of Alfven waves, provided it is small enough to power the turbulent cascade by means of reflection. For values of delta u in agreement with observational constraints, the turbulent dissipation achieves levels capable of sustaining a fast solar wind, with the maximum dissipation located at 2 solar radii, just below the sonic point. Despite the back reaction of the solar wind is not taken into account, this model shows that, under reasonable assumptions, a turbulent spectrum forms in the corona and it is able to sustain the heating and acceleration of the fast solar wind. Finally, the scaling laws obtained with this simplified 2D turbulence can be further constrained in order to include this mechanism of reflection driven turbulence in more complex solar wind models.

Verdini, A.; Velli, M.; Buchlin, E.

2008-09-01

390

Semiempirical Models of the Slow and Fast Solar Wind  

NASA Astrophysics Data System (ADS)

Coronal holes can produce several types of solar wind with a variety of compositional properties, depending on the location and strength of the heating along their open magnetic field lines. High-speed wind is associated with (relatively) slowly diverging flux tubes rooted in the interiors of large holes with weak, uniform footpoint fields; heating is spread over a large radial distance, so that most of the energy is conducted outward and goes into accelerating the wind rather than increasing the mass flux. In the rapidly diverging open fields present at coronal hole boundaries and around active regions, the heating is concentrated at low heights and the temperature maximum is located near the coronal base, resulting in high oxygen freezing-in temperatures and low asymptotic wind speeds. Polar plumes have a strong additional source of heating at their bases, which generates a large downward conductive flux, raising the densities and enhancing the radiative losses. The relative constancy of the solar wind mass flux at Earth reflects the tendency for the heating rate in coronal holes to increase monotonically with the footpoint field strength, with very high mass fluxes at the Sun offsetting the enormous flux-tube expansion in active region holes. Although coronal holes are its main source, slow wind is also released continually from helmet streamer loops by reconnection processes, giving rise to plasma blobs (small flux ropes) and the heliospheric plasma sheet.

Wang, Y.-M.

2012-11-01

391

Development of steady-state solar polar plume models in one and two dimensions to investigate solar wind sources  

Microsoft Academic Search

Solar plumes are bright radial rays with higher density and lower temperature than the surrounding interplume medium, which occur on the polar areas of the Sun where the high-speed solar wind is known to originate. Polar plumes provide a unique opportunity for understanding solar wind sources and the heating of open-field regions in the corona. We have used the equations

Beidi Peng

2008-01-01

392

Solar wind high-speed streams and related geomagnetic activity in the declining phase of solar cycle 23  

Microsoft Academic Search

Context. Coronal holes (CHs) are the source of high-speed streams (HSSs) in the solar wind, whose interaction with the slow solar wind creates corotating interaction regions (CIRs) in the heliosphere. Aims: We investigate the magnetospheric activity caused by CIR\\/HSS structures, focusing on the declining phase of the solar cycle 23 (years 2005 and 2006), when the occurrence rate of coronal

G. Verbanac; B. Vrsnak; S. Zivkovic; T. Hojsak; A. M. Veronig; M. Temmer

2011-01-01

393

Proton thermal energetics in the solar wind: Helios reloaded  

NASA Astrophysics Data System (ADS)

The proton thermal energetics in the slow solar wind between 0.3 and 1 AU is reinvestigated using the Helios 1 and 2 data, complementing a similar analysis for the fast solar wind [Hellinger et al., 2011]. The results for slow and fast solar winds are compared and discussed in the context of previous results. Protons need to be heated in the perpendicular direction with respect to the ambient magnetic field from 0.3 to 1 AU. In the parallel direction, protons need to be cooled at 0.3 AU, with a cooling rate comparable to the corresponding perpendicular heating rate; between 0.3 and 1 AU, the required cooling rate decreases until a transition to heating occurs: by 1 AU the protons require parallel heating, with a heating rate comparable to that required to sustain the perpendicular temperature. The heating/cooling rates (per unit volume) in the fast and slow solar winds are proportional to the ratio between the proton kinetic energy and the expansion time. On average, the protons need to be heated and the necessary heating rates are comparable to the energy cascade rate of the magnetohydrodynamic turbulence estimated from the stationary Kolmogorov-Yaglom law at 1 AU; however, in the expanding solar wind, the stationarity assumption for this law is questionable. The turbulent energy cascade may explain the average proton energetics (although the stationarity assumption needs to be justified) but the parallel cooling is likely related to microinstabilities connected with the structure of the proton velocity distribution function. This is supported by linear analysis based on observed data and by results of numerical simulations.

Hellinger, Petr; TráVní?ek, Pavel M.; Štverák, Št?pán; Matteini, Lorenzo; Velli, Marco

2013-04-01

394

Global aspects of stream evolution in the solar wind  

SciTech Connect

A spatially variable coronal expansion, when coupled with solar rotation, leads to the formation of high speed solar wind streams which evolve considerably with increasing heliocentric distance. Initially the streams steepen for simple kinematic reasons, but this steepening is resisted by pressure forces, leading eventually to the formation of forward-reverse shock pairs in the distant heliosphere. The basic physical processes responsible for stream steepening an evolution are explored and model calculations are compared with actual spacecraft observations of the process. The solar wind stream evolution problem is relatively well understood both observationally and theoretically. Tools developed in achieving this understanding should be applicable to other astrophysical systems where a spatially or temporally variable outflow is associated with a rotating object. 27 references, 13 figures.

Gosling, J.T.

1984-01-01

395

Solar wind outflow and the chromospheric magnetic network  

PubMed

Observations of outflow velocities in coronal holes (regions of open coronal magnetic field) have recently been obtained with the Solar and Heliospheric Observatory (SOHO) spacecraft. Velocity maps of Ne7+ from its bright resonance line at 770 angstroms, formed at the base of the corona, show a relationship between outflow velocity and chromospheric magnetic network structure, suggesting that the solar wind is rooted at its base to this structure, emanating from localized regions along boundaries and boundary intersections of magnetic network cells. This apparent relation to the chromospheric magnetic network and the relatively large outflow velocity signatures will improve understanding of the complex structure and dynamics at the base of the corona and the source region of the solar wind. PMID:9933156

Hassler; Dammasch; Lemaire; Brekke; Curdt; Mason; Vial; Wilhelm

1999-02-01

396

An analytical theory of the morphology, flows, and shock compressions at corotating interaction regions in the solar wind  

Microsoft Academic Search

An analytical theory for the structure of corotating interaction regions (CIRs) in the solar wind is developed. First, an approximate stream interface is determined by mapping the curve dividing fast and slow streams at the solar wind source surface into the solar wind, at the slow solar wind speed assuming a constant angular rotation rate of the Sun. The flow

Martin A. Lee

2000-01-01

397

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

398

Physical-Statistical Downscaling of Model Wind Speed and Solar Radiation: Forecasting Wind and Solar Energy in Nevada  

NASA Astrophysics Data System (ADS)

High temporal variability in wind speed and downward shortwave flux at ground surface has been evidenced by observations. The values also change spatially due to topography, cloud cover and other characteristics of the planetary boundary layer. Numerical weather prediction provides grid-scale resolved values; however, the sub-grid-scale part generally contributes more to variances of model wind speed and/or solar radiation. This part is parameterized, and not explicitly resolved. Electricity integration costs for wind and/or solar energy may be decreased if the variances and range of uncertainty are well explained to transmission system operators/electricity traders. In this study, month-long simulations in the summer and winter were conducted using the Weather Research and Forecasting (WRF) model. Observed wind and solar radiation data from four 50-m meteorological towers and one 80-m tower were used for evaluation of the model results and statistical analysis regarding the representativeness. Statistical characteristics of the observed and simulated data are analyzed. Physical downscaling of model wind and downward shortwave flux at the ground surface was obtained, with consideration of the influence of topography, cloud cover, turbulence kinetic energy and other characteristics of the PBL. The results show that the temporal variance of shortwave flux is greater than that of the wind power density, but the spatial variance of the wind power density is much greater than that of the shortwave flux. Furthermore, the WRF results are compared with the Operational Multiscale Environment model with Grid Adaptivity (OMEGA) model results. Physical downscaling methods with different parameters are introduced and implemented. The representativeness of model results and observed data are discussed.

Jiang, J.; Koracin, D.; King, K. C.

2011-12-01

399

Solar wind magnetosphere coupling: Predicted and modeled with intelligent hybrid systems  

Microsoft Academic Search

The solar wind-magnetosphere coupling is described as a mapping of the solar-solar wind state (input) to the magnetosphere-ionosphere state (output). The input-state is defined by solar wind parameters and the output-state is defined by geomagnetic disturbance indices. Most often are the geomagnetic disturbance indices Dst and AE used. However, a new family of geomagnetic disturbance indices, CO, SO and EO,

H. Lundstedt

1997-01-01

400

Solar wind iron abundance variations at solar wind speeds > 600 km s/sup -1/, 1972 to 1976  

SciTech Connect

We have analyzed the Fe/H ratios in the peaks of high speed streams (HSS) during the decline of Solar Cycle 20 and the following minimum (October 1972 to December 1976). We utilized the response of the 50 to 200 keV ion channel of the APL/JHU energetic particle experiment (EPE) onIMP-7 and 8 to solar wind iron ions at high solar wind speeds (V greater than or equal to 600 km sec/sup -1/), and compared our Fe measurements with solar wind H and He parameters 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 10/sup -5/, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated HSS. There are, as well, factor of 2 variations between stream-averaged abundances for recurent HSS emanating from different coronal holes occurring on the sun on the same solar rotation. flare-related solar wind streams sometimes show Fe/H ratios enhanced by factors of 4 to 5 over coronal-hole associated, quite time streams. Over the period 1973 to 1976, a steady decrease in the average quitetime Fe/H ratio by a ractor approx. 4 is measured on both IMP-7 and 8.

Mitchell, D.G.; Roelof, E.C.; Bame, S.J.

1982-01-01

401

Generalized similarity in magnetohydrodynamic turbulence as seen in the solar corona and solar wind  

NASA Astrophysics Data System (ADS)

A key property of turbulence is that it can be characterized and quantified in a robust and reproducible way in terms of the ensemble averaged statistical properties of fluctuations. Importantly, fluctuations associated with a turbulent field show similarity or scaling in their statistics and we test for this in observations of magnetohydrodynamic turbulence in the solar corona and solar wind with both power spectra and Generalized Structure Functions. Realizations of turbulence that are finite sized are known to exhibit a generalized or extended self-similarity (ESS). ESS was recently demonstrated in magnetic field timeseries of Ulysses single point in-situ observations of fluctuations of quiet solar wind for which a single robust scaling function was found [1-2]. Flows in solar coronal prominences can be highly variable, with dynamics suggestive of turbulence. The Hinode SOT instrument provides observations (images) at simultaneous high spatial and temporal resolution which span several decades in both spatial and temporal scales. We focus on specific Calcium II H-line observations of solar quiescent prominences with dynamic, highly variable small-scale flows. We analyze these images from the perspective of a finite sized turbulent flow. We discuss this evidence of ESS in the SOT images and in Ulysses solar wind observations- is there a single universal scaling of the largest eddies in the finite range magnetohydrodynamic turbulent flow? [1] S. C. Chapman, R. M. Nicol, Generalized Similarity in Finite Range Solar Wind Magnetohydrodynamic Turbulence, Phys. Rev. Lett., 103, 241101 (2009) [2] S. C. Chapman, R. M. Nicol, E. Leonardis, K. Kiyani, V. Carbone, Observation of universality in the generalized similarity of evolving solar wind turbulence as seen by ULYSSES, Ap. J. Letters, 695, L185, (2009)

Chapman, S. C.; Leonardis, E.; Nicol, R. M.; Foullon, C.

2010-12-01

402

Evolution of coronal holes and recurrent high-speed solar wind streams during solar cycle 23  

NASA Astrophysics Data System (ADS)

The relation between the solar wind velocity and the areas of low-latitude coronal holes (CHs) during solar cycle 23 was investigated. Low-latitude CHs areas were calculated based on SOHO/EIT observation in 195? and 284? channels and STEREO observation in 195? chan- A A A nel using a special numerical algorithm. The correlation between the daily average solar-wind velocities and the calculated CHs areas at different phases of the solar cycle was analyzed. The yearly correlation coefficient values from 0 for 2001 year up to 0.7 for 2003 year were found. Physical explanation of this fact is suggested in relation to the sporadic activity of the Sun. The calculated CHs areas were compared with the mean solar magnetic field measured by SOHO/MDI and ground based observatories. CHs areas measured using SOHO/EIT and STEREO observations in 284? and in 195? channels are compared. Elements of difference and A A likeness in character of correlation have been revealed in these spectral ranges. CHs areas in different spectral ranges can be used for filling data gaps and for investigation structures of the closing and opening magnetic field configuration in the vicinity of CHs. Special periods of time when active regions resided inside CHs are investigated with the results showing the influence of this situation on the solar wind properties. The neural network algorithm for prediction of the daily values of the solar wind velocity by the area of low-latitude CHs was developed and successfully used. A significant feature of such approach is the possibility of search for non-linear interconnections between CHs and the values of solar wind velocity.

Shugay, Yulia

403

Invited Article: Electric solar wind sail: Toward test missions  

NASA Astrophysics Data System (ADS)

The electric solar wind sail (E-sail) is a space propulsion concept that uses the natural solar wind dynamic pressure for producing spacecraft thrust. In its baseline form, the E-sail consists of a number of long, thin, conducting, and centrifugally stretched tethers, which are kept in a high positive potential by an onboard electron gun. The concept gains its efficiency from the fact that the effective sail area, i.e., the potential structure of the tethers, can be millions of times larger than the physical area of the thin tethers wires, which offsets the fact that the dynamic pressure of the solar wind is very weak. Indeed, according to the most recent published estimates, an E-sail of 1 N thrust and 100 kg mass could be built in the rather near future, providing a revolutionary level of propulsive performance (specific acceleration) for travel in the solar system. Here we give a review of the ongoing technical development work of the E-sail, covering tether construction, overall mechanical design alternatives, guidance and navigation strategies, and dynamical and orbital simulations.

Janhunen, P.; Toivanen, P. K.; Polkko, J.; Merikallio, S.; Salminen, P.; Haeggström, E.; Seppänen, H.; Kurppa, R.; Ukkonen, J.; Kiprich, S.; Thornell, G.; Kratz, H.; Richter, L.; Krömer, O.; Rosta, R.; Noorma, M.; Envall, J.; Lätt, S.; Mengali, G.; Quarta, A. A.; Koivisto, H.; Tarvainen, O.; Kalvas, T.; Kauppinen, J.; Nuottajärvi, A.; Obraztsov, A.

2010-11-01

404

Learning about coronal heating from solar wind observations  

SciTech Connect

Vlasov theory describing the interaction of Alfven-cyclotron fluctuations and ions in the collisionless solar wind predicts that alpha particles should be strongly scattered perpendicular to the background magnetic field when the alpha/proton relative velocity v{sub {alpha}}{sub p} is negative or has a sufficiently small positive value relative to the Alfven speed v{sub A}. This theory also predicts that, if v{sub {alpha}}{sub p}/v{sub A} is positive and sufficiently large, it is the protons which are scattered in the perpendicular direction, although less strongly. Here proton and alpha particle anisotropies measured in the solar wind near 1 AU (AU, astronomical unit) by the plasma and magnetic field instruments on the Advanced Composition Explorer spacecraft are reported which are consistent with these predicted signatures. This indicates that Alfven-cyclotron heating of ions is active in the solar wind; by using this medium to study this fundamental process, a greater understanding may be obtained of how Alfven-cyclotron scattering contributes to heating of ions in the solar corona.

Gary, S. Peter; Skoug, Ruth M.; Smith, Charles W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Space Science Center, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2005-05-15

405

Detection of fast nanoparticles in the solar wind  

SciTech Connect

Dust grains in the nanometer range bridge the gap between atoms and larger grains made of bulk material. Their small size embodies them with special properties. Due to their high relative surface area, they have a high charge-to-mass ratio, so that the Lorentz force in the solar wind magnetic field exceeds the gravitational force and other forces by a large amount, and they are accelerated to a speed of the order of magnitude of the solar wind speed. When such fast nanoparticles impact a spacecraft, they produce craters whose matter vaporises and ionises, yielding transient voltages as high as do much larger grains of smaller speed. These properties are at the origin of their recent detection at 1 AU in the solar wind. We discuss the detection of fast nanoparticles by wave instruments of different configurations, with applications to the recent detections on STEREO/WAVES and CASSINI/RPWS. Finally we discuss the opportunities for nanoparticle detection by wave instruments on future missions and/or projects in the inner heliosphere such as Bepi-Colombo and Solar Orbiter.

Meyer-Vernet, N.; Maksimovic, M.; Lecacheux, A.; Le Chat, G. [LESIA, Observatoire de Paris, CNRS, U. Paris Diderot, UPMC, 5 Place Janssen, 92190 Meudon (France); Czechowski, A. [Space Research Centre, Polish Academy of Sciences, Bartycka 18 A PL-00-716, Warsaw (Poland); Mann, I. [School of Science and Engineering, Kindai University Kowakae 3-4-1, Osaka, 577-8502 (Japan); Goetz, K. [School of Physics and Astronomy, University of Minnesota, Minneapolis (United States); Kaiser, M. L.; Cyr, O. C. St. [NASA-GSFC, Greenbelt, MD 20771 (United States); Bale, S. D. [Space Sciences Laboratory, University of California, Berkeley (United States)

2010-03-25

406

Comet flares and velocity waves in the solar wind  

SciTech Connect

The flare activity of comets and the structure of the solar wind fluxes are compared with data of measurements of Pioneer-10, -11, Vela-3, IPM-7, and -8 at a heliocentric distance of r approx. = 1-6 AU. It is shown that velocity waves of the solar wind, which evolve into corotating shock waves beyond the orbit of the earth, may be responsible for the flare activity of comets. The work notes a correspondence between the variations of flare activity of comets as a function of heliocentric distance and the behavior of velocity waves in the solar wind, the closeness of the characteristic times of velocity waves (about 7-8 days at r = 1 AU) and the duration of comet flares, and the increase of this characteristic time with increasing r in both cases. The observed distribution of the parameters of comet flare activity in the 11-yr cycle also corresponds well to the distribution of the area of coronal holes and the rate of variation of the area of sunspots ..delta..Sp over the phase of the solar cycle.

Ptitsyna, N.G.; Breus, T.K.; Rikhter, A.K.

1986-05-01

407

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

408

A MODEL FOR THE SOURCES OF THE SLOW SOLAR WIND  

SciTech Connect

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}60{sup 0}, 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.

Antiochos, S. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mikic, Z.; Titov, V. S.; Lionello, R.; Linker, J. A., E-mail: spiro.antiochos@nasa.gov [Predictive Science, Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States)

2011-04-20

409

Geosynchronous Magnetic Field Response to Solar Wind Dynamic Pressure  

NASA Astrophysics Data System (ADS)

The present study examines the morning-afternoon asymmetry of the geosynchronous magnetic field strength on the dayside (magnetic local time [MLT] = 06:00~18:00) using observations by the Geostationary Operational Environmental Satellites (GOES) over a period of 9 years from February 1998 to January 2007. During geomagnetically quiet time (Kp < 3), we observed that a peak of the magnetic field strength is skewed toward the earlier local times (11:07~11:37 MLT) with respect to local noon and that the geosynchronous field strength is larger in the morning sector than in the afternoon sector. That is, there is the morning-afternoon asymmetry of the geosynchronous magnetic field strength. Using solar wind data, it is confirmed that the morning-afternoon asymmetry is not associated with the aberration effect due to the orbital motion of the Earth about the Sun. We found that the peak location of the magnetic field strength is shifted toward the earlier local times as the ratio of the magnetic field strength at MLT = 18 (B-dusk) to the magnetic field strength at MLT = 06 (B-dawn) is decreasing. It is also found that the dawn-dusk magnetic field median ratio, B-dusk/B-dawn, is decreasing as the solar wind dynamic pressure is increasing. The morning-afternoon asymmetry of the magnetic field strength appears in Tsyganenko geomagnetic field model (TS-04 model) when the partial ring current is included in TS-04 model. Unlike our observations, however, TS-04 model shows that the peak location of the magnetic field strength is shifted toward local noon as the solar wind dynamic pressure grows in magnitude. This may be due to that the symmetric magnetic field associated with the magnetopause current, strongly affected by the solar wind dynamic pressure, increases. However, the partial ring current is not affected as much as the magnetopause current by the solar wind dynamic pressure in TS-04 model. Thus, our observations suggest that the contribution of the partial ring current at geosynchronous orbit is much larger than that expected from TS-04 model as the solar wind dynamic pressure increases.

Park, Jong-Sun; Kim, Khan-Hyuk; Lee, Dong-Hun; Lee, Ensang; Jin, Ho

2011-03-01

410

Ionospheric cusp flows pulsed by solar wind Alfvén waves  

NASA Astrophysics Data System (ADS)

Pulsed ionospheric flows (PIFs) in the cusp foot-print have been observed by the SuperDARN radars with periods between a few minutes and several tens of minutes. PIFs are believed to be a consequence of the interplanetary magnetic field (IMF) reconnection with the magnetospheric magnetic field on the dayside magnetopause, ionospheric signatures of flux transfer events (FTEs). The quasiperiodic PIFs are correlated with Alfvénic fluctuations observed in the upstream solar wind. It is concluded that on these occasions, the FTEs were driven by Alfvén waves coupling to the day-side magnetosphere. Case studies are presented in which the dawn-dusk component of the Alfvén wave electric field modulates the reconnection rate as evidenced by the radar observations of the ionospheric cusp flows. The arrival of the IMF southward turning at the magnetopause is determined from multipoint solar wind magnetic field and/or plasma measurements, assuming plane phase fronts in solar wind. The cross-correlation lag between the solar wind data and ground magnetograms that were obtained near the cusp footprint exceeded the estimated spacecraft-to-magnetopause propagation time by up to several minutes. The difference can account for and/or exceeds the Alfvén propagation time between the magnetopause and ionosphere. For the case of short period ( < 13 min) PIFs, the onset times of the flow transients appear to be further delayed by at most a few more minutes after the IMF southward turning arrived at the magnetopause. For the case of long period (30 40 min) PIFs, the observed additional delays were 10 20 min. We interpret the excess delay in terms of an intrinsic time scale for reconnection (Russell et al., 1997) which can be explained by the surface-wave induced magnetic reconnection mechanism (Uberoi et al., 1999). Here, surface waves with wavelengths larger than the thickness of the neutral layer induce a tearing-mode instability whose rise time explains the observed delay of the reconnection onset. The compressional fluctuations in solar wind and those generated in the magnetosheath through the interaction between the solar wind

Prikryl, P.; Provan, G.; McWilliams, K. A.; Yeoman, T. K.

2002-02-01

411

Turbulent Alfven Waves as a Solar Wind Driver: Results from a new 4D model for the Solar Corona and Solar Wind  

NASA Astrophysics Data System (ADS)

The mechanisms responsible for plasma heating in the solar corona and solar wind acceleration are still not well understood. Turbulent MHD waves have been suggested as a possible mechanism, which both heats the plasma via wave energy dissipation and accelerates it due to the wave pressure gradient force. In order to account for these processes, a self-consistent model of the solar corona and solar wind must include the wave transport equation. Coupling this equation to the 3D MHD equations allows the exchange of momentum and energy between the wave field and the background plasma. This coupled system of equations is solved in a recently developed computational model of MHD wave turbulence, implemented within the SWMF/BATSRUS. The model is based on a wave transport equation for low frequency Alfven waves derived in Sokolov et. al. (2009). In every spatial cell a frequency grid is constructed, allowing the detailed description of the wave energy spectral evolution, making the model effectively 4D. Recent Hinode observations of chromospheric Alfven waves have shown that their energy flux could constitute a sufficient energy source to drive the solar wind. In this work we examined the possible effects of Alfven wave turbulence by imposing a Kolmogorov - type spectrum as the inner boundary condition for the 4D solar corona model. We found that the solar wind can indeed be totally driven by the Alfven wave pressure. The 4D solar corona model is coupled to an MHD model of the inner heliosphere, which extends the simulation results to larger heliocentric distances. This allows us to compare our results to solar wind in situ data at 1AU.

Oran, R.; Sokolov, I.; Roussev, I. I.; Frazin, R. A.; Gombosi, T. I.

2009-12-01

412

Solar winds surfs waves in the Sun's atmosphere!  

NASA Astrophysics Data System (ADS)

The fact that this electrified plasma speeds up to almost 3 million kilometres per hour as it leaves the Sun - twice as fast as originally predicted - has been known for years. The interpretation of how it happens is the real and surprising novelty: "The waves in the Sun's atmosphere are produced by vibrating solar magnetic field lines, which give solar wind particles a push just like an ocean wave gives a surfer a ride" said Dr John Kohl, principal investigator for the Ultraviolet Coronal Spectrometer (UVCS) - the instrument among the 12 aboard SOHO which gathered the data - and for the Spartan 201 mission. The outermost solar atmosphere, or corona, is only seen from Earth during a total eclipse of the Sun, when it appears as a shimmering, white veil surrounding the black lunar disc. The corona is an extremely tenuous, electrically charged gas, known as plasma, that flows throughout the solar system as the solar wind. The waves are formed by rapidly vibrating magnetic fields in the coronal plasma. They are called magneto - hydro - dynamic (MHD) waves and are believed to accelerate the solar wind. The solar wind is made up of electrons and ions, electrically charged atoms that have lost electrons. The electric charge of the solar wind particles forces them to travel along invisible lines of magnetic force in the corona. The particles spiral around the magnetic field lines as they rush into space. "The magnetic field acts like a violin string: when it's touched, it vibrates. When the Sun's magnetic field vibrates with a frequency equal to that of the particle spiraling around the magnetic field, it heats it up, producing a force that accelerates the particle upward and away from the Sun," says Dr. Ester Antonucci, an astronomer at the observatory of Turin, Italy, and co-investigator for SOHO's UVCS an instrument developed with considerable financial support by the Italian Space Agency, ASI. In a way this is similar to what happens if two people hold a string at opposite ends after threading it through an object, like a ring. If one person wiggles the string rapidly up and down, waves form in the string that move toward the person at the other end. The ring will "surf" these waves and move toward the other person as well. Try it! "Even with this major discovery, there are questions left to answer. The observations have made it abundantly clear that heavy particles like oxygen 'surf' on the waves, and there is also mounting evidence that waves are responsible for accelerating the hydrogen atoms, the most common constituent of the solar wind. Future observations are needed to establish this fact. Many other kinds of particles, such as helium (second most common) have never been observed in the accelerating part of the corona, and new observations are also needed to refine our understanding of how the waves interact with the solar wind as a whole," said Dr. Steven Cranmer of the Harvard-Smithsonian Center for Astrophysics, lead author of the research to be published in the Astrophysical Journal*. Nevertheless, SOHO has again been able to reveal another of the Sun's mysteries: "This is another triumph for SOHO, stealing a long-held secret from our Sun", said Dr Martin Huber, Head of ESA Space Science Department and co-investigator for UVCS. *Ref. Article by S.Cranmer, G.B. Field and J.L. Kohl on Astrophysical Journal ( June 20, Vol 518, p. 937-947) available on the web at: http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v518n2/39802/sc0.html

1999-06-01

413

Solar winds surfs waves in the Sun's atmosphere!  

NASA Astrophysics Data System (ADS)

The fact that this electrified plasma speeds up to almost 3 million kilometres per hour as it leaves the Sun - twice as fast as originally predicted - has been known for years. The interpretation of how it happens is the real and surprising novelty: "The waves in the Sun's atmosphere are produced by vibrating solar magnetic field lines, which give solar wind particles a push just like an ocean wave gives a surfer a ride" said Dr John Kohl, principal investigator for the Ultraviolet Coronal Spectrometer (UVCS) - the instrument among the 12 aboard SOHO which gathered the data - and for the Spartan 201 mission. The outermost solar atmosphere, or corona, is only seen from Earth during a total eclipse of the Sun, when it appears as a shimmering, white veil surrounding the black lunar disc. The corona is an extremely tenuous, electrically charged gas, known as plasma, that flows throughout the solar system as the solar wind. The waves are formed by rapidly vibrating magnetic fields in the coronal plasma. They are called magneto - hydro - dynamic (MHD) waves and are believed to accelerate the solar wind. The solar wind is made up of electrons and ions, electrically charged atoms that have lost electrons. The electric charge of the solar wind particles forces them to travel along invisible lines of magnetic force in the corona. The particles spiral around the magnetic field lines as they rush into space. "The magnetic field acts like a violin string: when it's touched, it vibrates. When the Sun's magnetic field vibrates with a frequency equal to that of the particle spiraling around the magnetic field, it heats it up, producing a force that accelerates the particle upward and away from the Sun," says Dr. Ester Antonucci, an astronomer at the observatory of Turin, Italy, and co-investigator for SOHO's UVCS an instrument developed with considerable financial support by the Italian Space Agency, ASI. In a way this is similar to what happens if two people hold a string at opposite ends after threading it through an object, like a ring. If one person wiggles the string rapidly up and down, waves form in the string that move toward the person at the other end. The ring will "surf" these waves and move toward the other person as well. Try it! "Even with this major discovery, there are questions left to answer. The observations have made it abundantly clear that heavy particles like oxygen 'surf' on the waves, and there is also mounting evidence that waves are responsible for accelerating the hydrogen atoms, the most common constituent of the solar wind. Future observations are needed to establish this fact. Many other kinds of particles, such as helium (second most common) have never been observed in the accelerating part of the corona, and new observations are also needed to refine our understanding of how the waves interact with the solar wind as a whole," said Dr. Steven Cranmer of the Harvard-Smithsonian Center for Astrophysics, lead author of the research to be published in the Astrophysical Journal*. Nevertheless, SOHO has again been able to reveal another of the Sun's mysteries: "This is another triumph for SOHO, stealing a long-held secret from our Sun", said Dr Martin Huber, Head of ESA Space Science Department and co-investigator for UVCS. *Ref. Article by S.Cranmer, G.B. Field and J.L. Kohl on Astrophysical Journal ( June 20, Vol 518, p. 937-947) available on the web at: http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v518n2/39802/sc0.html

1999-07-01

414

The effect of model generated solar radiation data usage in hybrid (wind–PV) sizing studies  

Microsoft Academic Search

Wind speed and solar radiation characteristics belonging to past years of a region are the main input parameters in wind–photovoltaic hybrid system (WPHS) sizing studies. Classically, these data are fed to several scenarios with different solar panel, wind turbine, and storage battery number combinations. The solutions with minimal cost which also satisfy the desired maximum loss of energy probability are

Fatih Onur Hocaoglu; Omer Nezih Gerek; Mehmet Kurban

2009-01-01

415

Analysis of off-grid hybrid wind turbine/solar PV water pumping systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

While many remote water pumping systems exist (e.g. mechanical windmills, solar photovoltaic , wind-electric, diesel powered), very few combine both the wind and solar energy resources to possibly improve the reliability and the performance of the system. In this paper, off-grid wind turbine (WT) a...

416

Solar Wind Acceleration Mechanisms: Suprathermal Electron Effects Versus Wave-Particle Interactions  

Microsoft Academic Search

Various physical mechanisms have been considered as possible drivers of the solar wind. One of the possible acceleration mechanisms was suggested to be due to the heat flux generated by the suprathermal electrons in the solar wind [Olbert, 1982]. Such an idea has been applied to the ionospheric polar wind with photoelectrons playing the role of the suprathermal population [Tam

S. W. Tam; T. Chang

2001-01-01

417

Termination of the solar wind in the hot, partially ionized interstellar medium  

Microsoft Academic Search

It is suggested that a simple extention of an existing analytical model provides a useful approximate description of the combined solar wind, interstellar wind plasma flowfield under conditions thought to occur. A linear perturbation solution exhibiting both the effects of photoionization and charge exchange is obtained for the supersonic solar wind. Investigation of the one-dimensional compressible flow equation and heating

C. K. Lombard

1975-01-01

418

The effects of lunar surface plasma absorption and solar wind temperature anisotropies on the solar wind proton velocity space distributions in the low-altitude lunar plasma wake  

NASA Astrophysics Data System (ADS)

We study the solar wind proton velocity space distribution functions on the lunar nightside at low altitudes (?100 km) above the lunar surface using a three-dimensional hybrid plasma solver, when the Moon is in the unperturbed solar wind. When the solar wind encounters a passive obstacle, such as the Moon, without any strong magnetic field and no atmosphere, solar wind protons that impact the obstacle's surface are absorbed and removed from the velocity space distribution functions. We show first that a hybrid model of plasma is applicable to study the low-altitude lunar plasma wake by comparing the simulation results with observations. Then we examine the effects of a solar wind bi-Maxwellian velocity space distribution function and the lunar surface plasma absorption on the solar wind protons' velocity space distribution functions and their entry in the direction parallel to the interplanetary magnetic field lines into the low-altitude lunar wake. We present a backward Liouville method for particle-in-cell solvers that improves velocity space resolution. The results show that the lunar surface plasma absorption and anisotropic solar wind velocity space distributions result in substantial changes in the solar wind proton distribution functions in the low-altitude lunar plasma wake, modifying proton number density, velocity, and temperature there. Additionally, a large temperature anisotropy is found at close distances to the Moon on the lunar nightside as a consequence of the lunar surface plasma absorption effect.

Fatemi, S.; Holmström, M.; Futaana, Y.

2012-10-01

419

Asteroid touring mission with Electric Solar Wind Sail  

NASA Astrophysics Data System (ADS)

Current and planned asteroid missions target only a single, or a few of asteroids, and have consumed their propellant after reaching their targets. We propose here using the new Electric Solar Wind Sail (E-sail) technology in a mission touring several different asteroids with the same spacecraft. This is made possible by the fact that E-sail does not consume any propellant and that the E-sail is well manoeuvrable. Moreover, most of the asteroids reside at a convenient distance from the Sun, providing the Esail with a sufficient stream of solar wind particles to draw momentum from. Currently E-sail seems to be a superior propulsion method for asteroid touring mission type of tasks discussed in this paper.

Merikallio, S.; Kvell, U.; Toivanen, P.; Janhunen, P.

2011-10-01

420

Dayside Magnetosphere-Ionosphere Solar Wind Driven Dynamics  

NASA Astrophysics Data System (ADS)

oDynamical equations are derived for the dayside region 1, region 2, and magnetopause current loops associated with solar wind compressions of the magnetopause stand off distance. The geometry for the loops is determined first with analytical models and then compared with the Tsyganenko 2005 model. The model predicts from solar wind plasma data the motion of the magnetopause standoff distance Rmp(t) and the the upper auroral index AU from the eastward auroral electrojet current in the auroral oval. The dynamical frequencies are in the range to drive ULF and VLF waves in the magnetosphere. The addition of the Chapman-Ferraro currents to the WINDMI model allows the prediction of the sudden commencement peaks of positive Dst that occur when the magnetopuase is pushed Earthward by a strong pressure pulse. The first runs show a sudden commencement signal typical of the data. The work is supported by NSF grant ATM-0638480.

Horton, W.; Mays, M. L.; Spencer, E.

2008-12-01

421

Generation of residual energy in the turbulent solar wind  

SciTech Connect

In situ observations of the fluctuating solar wind flow show that the energy of magnetic field fluctuations always exceeds that of the kinetic energy, and therefore the difference between the kinetic and magnetic energies, known as the residual energy, is always negative. The same behaviour is found in numerical simulations of magnetohydrodynamic turbulence. We study the dynamics of the residual energy for strong, anisotropic, critically balanced magnetohydrodynamic turbulence using the eddy damped quasi-normal Markovian approximation. Our analysis shows that for stationary critically balanced magnetohydrodynamic turbulence, negative residual energy will always be generated by nonlinear interacting Alfven waves. This offers a general explanation for the observation of negative residual energy in solar wind turbulence and in the numerical simulations.

Gogoberidze, G. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom); Institute of Theoretical Physics, Ilia State University, 3/5 Cholokashvili Ave., 0162 Tbilisi (Georgia); Chapman, S. C.; Hnat, B. [Centre for Fusion, Space and Astrophysics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-10-15

422

Coronal Holes and the High-Speed Solar Wind  

NASA Astrophysics Data System (ADS)

Coronal holes are the lowest density plasma components of the Sun's outer atmosphere, and are associated with rapidly expanding magnetic fields and the acceleration of the high-speed solar wind. Spectroscopic and polarimetric observations of the extended corona, coupled with interplanetary particle and radio sounding measurements going back several decades, have put strong constraints on possible explanations for how the plasma in coronal holes receives its extreme kinetic properties. The Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft has revealed surprisingly large temperatures, outflow speeds, and velocity distribution anisotropies for positive ions in coronal holes. We review recent observations, modeling techniques, and proposed heating and acceleration processes for protons, electrons, and heavy ions. We emphasize that an understanding of the acceleration region of the wind (in the nearly collisionless extended corona) is indispensable for building a complete picture of the physics of coronal holes.

Cranmer, Steven R.

2002-08-01

423

Identification of the Coronal Sources of the Fast Solar Wind.  

PubMed

The present spectroscopic study of the ultraviolet coronal emission in a polar hole, detected on 1996 April 6-9 with the Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory spacecraft, identifies the interplume lanes and background coronal hole regions as the channels in which the fast solar wind is preferentially accelerated. In interplume lanes, at heliocentric distance 1.7 R middle dot in circle, the corona expands at a rate between 105 and 150 km s-1, that is, much faster than in plumes in which the outflow velocity is between 0 and 65 km s-1. The wind velocity is inferred from the Doppler dimming of the O vi lambdalambda1032, 1037 lines, within a range of values, whose lower and upper limit corresponds to anisotropic and isotropic velocity distribution of the oxygen coronal ions, respectively. PMID:10673419

Giordano; Antonucci; Noci; Romoli; Kohl

2000-03-01

424

Generation of residual energy in the turbulent solar wind  

NASA Astrophysics Data System (ADS)

In situ observations of the fluctuating solar wind flow show that the energy of magnetic field fluctuations always exceeds that of the kinetic energy, and therefore the difference between the kinetic and magnetic energies, known as the residual energy, is always negative. The same behaviour is found in numerical simulations of magnetohydrodynamic turbulence. We study the dynamics of the residual energy for strong, anisotropic, critically balanced magnetohydrodynamic turbulence using the eddy damped quasi-normal Markovian approximation. Our analysis shows that for stationary critically balanced magnetohydrodynamic turbulence, negative residual energy will always be generated by nonlinear interacting Alfvén waves. This offers a general explanation for the observation of negative residual energy in solar wind turbulence and in the numerical simulations.

Gogoberidze, G.; Chapman, S. C.; Hnat, B.

2012-10-01

425

Solar wind collimation of the Jupiter high velocity dust streams  

NASA Astrophysics Data System (ADS)

The dust bursts discovered by the Ulysses dust sensor when approaching Jupiter in 1992 were later confirmed as collimated streams of high velocity (~200 km/s) charged (~5V) dust grains escaping from Jupiter and dominated by the interplanetary Magnetic field (IMF). With Cassini, a similar phenomenon was observed in Saturn. It was demonstrated that the Jovian dust streams are closely related to the solar wind compressed regions, either Corotating interaction regions (CIRs) or Coronal mass ejections (CMEs) ¨Cto a minor extent-. Actually the dust streams seem ultimately to be generated by such events. This can be explained considering that dust grains are accelerated as they gain substantial energy while compressed at the forward and reverse shocks that bound or precede these solar wind regions.

Flandes, A.; Krueger, H.

2006-12-01

426

THREE-DIMENSIONAL STRUCTURE OF SOLAR WIND TURBULENCE  

SciTech Connect

We present a measurement of the scale-dependent, three-dimensional structure of the magnetic field fluctuations in inertial range solar wind turbulence with respect to a local, physically motivated coordinate system. The Alfvenic fluctuations are three-dimensionally anisotropic, with the sense of this anisotropy varying from large to small scales. At the outer scale, the magnetic field correlations are longest in the local fluctuation direction, consistent with Alfven waves. At the proton gyroscale, they are longest along the local mean field direction and shortest in the direction perpendicular to the local mean field and the local field fluctuation. The compressive fluctuations are highly elongated along the local mean field direction, although axially symmetric perpendicular to it. Their large anisotropy may explain why they are not heavily damped in the solar wind.

Chen, C. H. K.; Bale, S. D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Mallet, A.; Schekochihin, A. A. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); Horbury, T. S. [Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom); Wicks, R. T., E-mail: chen@ssl.berkeley.edu [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-10-20

427

Residual energy in MHD turbulence and in the solar wind  

NASA Astrophysics Data System (ADS)

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 Er = Ev - Eb 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 Alfvén waves, we demonstrate that the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear interaction of Alfvén 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.

Boldyrev, Stanislav; Perez, Jean Carlos; Zhdankin, Vladimir

2012-05-01

428

THE DISSIPATION OF SOLAR WIND TURBULENT FLUCTUATIONS AT ELECTRON SCALES  

SciTech Connect

We present two-dimensional fully kinetic particle-in-cell simulations of decaying electromagnetic fluctuations. The computational box is such that wavelengths ranging from electron to ion gyroradii are resolved. The parameters used are realistic for the solar wind, and the ion-to-electron mass ratio is physical. The dissipation of turbulent fluctuations at small scales is thought to be a crucial mechanism for solar wind acceleration and coronal heating. The computational results suggest that a power-law cascade of magnetic fluctuations could be sustained up to scales of the electron Larmor radius and smaller. We analyze the simulation results in light of the Vlasov linear theory, and we comment on the particle heating. The dispersion curves of lightly damped modes in this regime suggest that a linear mechanism could be responsible for the observed steepening of power spectra at electron scales, but a straightforward identification of turbulent fluctuations as an ensemble of linear modes is not possible.

Camporeale, Enrico; Burgess, David [School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

2011-04-01

429

Finite size effects and scaling in solar wind fluctuations  

SciTech Connect

This review highlights recent examples of generic statistical scaling as departures from ideal Kolmogorov fluid turbulence as seen in the solar wind. Similarity analysis is first reviewed to set turbulence in the context of the wider class of observed phenomenology that show statistical scaling. Examples are provided that are characteristic of finite range MHD turbulent phenomenology-anisotropy, and generalized similarity as a finite range effect. This motivates the question as to whether the observed phenomonology are universal.

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

2010-12-14

430

Multi-scale Turbulence in the Inner Solar Wind  

Microsoft Academic Search

Spacecraft measurements made in the solar wind show velocity and magnetic fluctuations over a broad range of frequencies.\\u000a These fluctuations possess many properties expected of fully developed turbulence. In this paper, a brief overview is given\\u000a on turbulence in the inner ( 1Hz) frequencies for which non linear dispersive\\u000a effects dominate. Then, a discussion is given about recent theoretical results on

Sébastien Galtier

2006-01-01

431

Performance evaluation of hybrid (wind\\/solar\\/diesel) power systems  

Microsoft Academic Search

Depleting oil and gas reserves, combined with the growing concerns of global warming, have made it inevitable to seek alternative\\/renewable energy sources. The integration of renewables such as solar and wind energy is becoming increasingly attractive and is being used widely, for substitution of oil-produced energy, and eventually to minimize atmospheric degradation. The literature shows that commercial\\/residential buildings in Saudi

M. A. Elhadidy

2002-01-01

432

Acceleration of Suprathermal Tails in the Solar Wind  

Microsoft Academic Search

Suprathermal particles are ubiquitously present in the solar wind, with energies typically from ~1 keV\\/nucleon to ~a few MeV\\/nucleon. Remarkably, the suprathermal particles exhibit a common spectral shape in many different circumstances; the distribution function is a power law in particle speed, with spectral index of -5. A theory is presented in which the particles are accelerated in compressional turbulence.

L. A. Fisk; G. Gloeckler

2008-01-01

433

Coupling function between solar wind parameters and geomagnetic indices  

Microsoft Academic Search

Results of past studies on the correlation of a function of solar wind parameters with a geomagnetic index are reviewed and examined to identify the most relevant coupling function among those hitherto proposed. For the AL index, three functions B(s)V, B(s)V-squared, and Akasofu's (1980) epsilon are compared, where B(s) is the southward component of the interplanetary magnetic field and V

Takashi Murayama

1982-01-01

434

Solar wind iron charge states preceding a driver plasma  

Microsoft Academic Search

During September 28 and 29, 1978, the ISEE 3 spacraft observed several distinct types of high-speed solar wind flows when a coronal hole--associated high-speed stream was followed by two interplanetary shocks, one of which was driven by flare ejecta contained in a ''magnetic cloud'' or interplanetary ''plasmoid.'' Using the University of Maryland\\/Max-Planck-Institut ultralow energy charge analyzer (ULECA) on ISEE 3,

A. B. Galvin; F. M. Ipavich; G. Gloeckler; D. Hovestadt; S. J. Bame; B. Klecker; M. Scholer; B. T. Tsurutani

1987-01-01

435

Solar wind-magnetosphere-ionosphere current-voltage relationship  

Microsoft Academic Search

The nature of the solar wind-magnetosphere-ionosphere (SW-M-I) coupling has been a subject of intense study and scientific interest. We report results from a numerical simulation of the SW-M-I system which shed light on the physics and behavior of the controlling processes. The current-voltage relationship is characteristic of a magnetohydrodynamic dynamo with a load operating near short circuit conditions. We discuss

J. A. Fedder; J. G. Lyon

1987-01-01

436

Deflection of solar wind protons over magnetic anomalies  

NASA Astrophysics Data System (ADS)

The Moon has no any significant atmosphere and magnetic field. So it has considered lake a passive absorber of incoming plasma. The latest observation revealed that the significant deflected proton fluxes exist over magnetic anomalies at lunar surface. Such deflection implies that the magnetic anomalies may act as magnetosphere-like obstacles (mini-magnetospheres), modifying the upstream plasma. We described the possible deflection mechanisms and their relations to solar wind.

Sadovski, Andrei M.; Skalsky, Alexander A.

2013-04-01

437

Helium and hydrogen velocity differences in the solar wind  

Microsoft Academic Search

Scalar and vector velocity differences between helium and hydrogen ions in the solar wind measured with the Los Alamos plasma analyzers on Imp 6 and 7 are presented and interpreted. From the bulk speeds and azimuthal components of flow direction for both types of ions the ecliptic projection of the helium to hydrogen velocity difference vector v\\/subo\\/\\/subp\\/ is determined. Short-term

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

1976-01-01

438

Deformation of the Geomagnetic Field by the Solar Wind  

Microsoft Academic Search

From the three-dimensional numerical solution to the Chapman-Ferraro prob- lem of a steady solar wind perpendicularly incident upon a dipole field, a simple spherical harmonic description of the distorted field is obtained. From this, a three-dimensional picture of the field line