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1

Depth and latitude dependence of the solar internal angular velocity  

NASA Technical Reports Server (NTRS)

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.

Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

1990-01-01

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

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

4

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

5

The effects of solar cycle and latitude dependence on the formation of ionospheric C layer  

NASA Astrophysics Data System (ADS)

The C-layer effect is observed on long distance very low frequency (VLF) signal propagation at sunrise, when the solar illumination line (terminator) makes a small angle (alpha is less than 20 deg) with the propagation path. The effect may be described as an additional phase advance, just after the sunrise normal phase advance, recovering in about 90 minutes. Analysis of different propagation paths shows that the magnitude of the observed effect presents a latitudinal and solar cycle dependence. Data obtained for geomagnetic latitudes ranging 14 deg N to 50 deg S have shown that the C-layer effect seems to be more pronounced at higher latitudes. Finally analysis of data at different phases of the solar cycle suggest that for the period of maximum activity the magnitude of the observed C-layer effect is reduced. These effects may be understood bearing in mind that cosmic radiation is mainly responsible for the ionization of regions below the ionospheric D-layer. It is more intense at higher latitudes and also presents a variation with the solar cycle, being minimum when maximum solar activity occurs. In the analysis, different phenomena which could influence the C-layer effect were taken into account, such as SIDs at sunrise, Forbush decrease, stratwarm and magnetic storms.

Requiakuntz, Vera Lucia

1987-09-01

6

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

7

Solar Wind Five  

NASA Technical Reports Server (NTRS)

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

Neugebauer, M. (editor)

1983-01-01

8

The Solar Wind  

NSDL National Science Digital Library

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

David Hathaway

9

The Solar Wind  

NASA Technical Reports Server (NTRS)

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

Goldstein, B. E.

1998-01-01

10

Solar Wind Magnetic Fields  

NASA Technical Reports Server (NTRS)

The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

Smith, E. J.

1995-01-01

11

Solar wind composition  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

12

SOLAR WIND CORRELATIONS: USING A SOLAR WIND MONITOR SUCCESSFULLY  

E-print Network

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

Richardson, John

13

The Solar Wind  

NSDL National Science Digital Library

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

Mendez, J.

14

Flank solar wind interaction  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

15

Accelerating the Solar Wind  

NASA Astrophysics Data System (ADS)

At 1 AU the fast solar wind reaches speeds that are 2-3 times greater than can be accounted for by the pressure gradient due to the high coronal temperatures. This paper introduces a mechanism that may account for this shortfall, namely, the force due to the gradient of the magnetic pressure of an azimuthal magnetic field, B?, generated by a current jr flowing along the open-ended flux tube guiding the wind. The electromotive force (EMF) driving this current is due to the difference between the thermoelectric force acting on the electron gas within a flux tube and that in the ambient plasma. Using observed values of the magnetic field, we show that this mechanism is capable of accelerating the solar wind up to speeds of 800 km s-1 and higher. It also produces a profile of the radial wind speed v(r) that is nearly flat beyond about 0.15 AU, as is observed.

Ashbourn, J. M. A.; Woods, L. C.

2005-04-01

16

Flank solar wind interaction  

NASA Technical Reports Server (NTRS)

This report summarizes the results of the first 12 months of our program to study the interaction of the Earth's magnetosphere with the solar wind on the far flanks of the bow shock. This study employs data from the ISEE-3 spacecraft during its traversals of the Earth's magnetotail and correlative data from spacecraft monitoring the solar wind upstream. Our main effort to date has involved assembling data sets and developing new plotting programs. Two talks were given at the Spring Meeting of the American Geophysical Union describing our initial results from analyzing data from the far flank foreshock and magnetosheath. The following sections summarize our results.

Moses, Stewart L.; Greenstadt, Eugene W.

1992-01-01

17

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

E-print Network

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

Petrovay, Kristóf

18

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

19

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

20

Solar wind heating.  

NASA Technical Reports Server (NTRS)

The difference in objectives, physical assumptions, and results among the most recent detailed models aimed at understanding energy transport in the solar wind are analyzed. Models have been judged primarily by comparing their predictions against spacecraft observations near 1 AU. However, the observed values of flow speed, density, and temperature fluctuate over a wide range so that the criteria for agreement between theory and observation are necessarily somewhat subjective.

Barnes, A.; Brandt, J. C.; Hartle, R. E.; Wolff, C. L.

1972-01-01

21

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

22

Composition of the Solar Wind  

NASA Technical Reports Server (NTRS)

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

Suess, S. T.

2007-01-01

23

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, 2014

...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

24

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

25

Solar wind stagnation near comets  

Microsoft Academic Search

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

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

1985-01-01

26

Solar wind photoplate study  

NASA Technical Reports Server (NTRS)

An ion sensitive emulsion detection system has been considered for use in a cycloidal focusing mass spectrometer to measure the various atomic species which comprise the solar plasma. The responses of Ilford Q2 and Kodak SC7 emulsions were measured with N(+) ions at 6 keV to 10 keV, He(++) ions at 750 eV to 2500 eV, and H(+) ions at 550 eV to 1400 eV. These ions have the approximate range of velocities (about 300-500 km/sec) encountered in the solar wind. The work was carried out on a specially prepared magnetic sector mass analyzer. Characteristic response curves were generated, each one utilizing approximately 50 data points at three or more current densities. In addition to the ion response, measurements of the response of these emulsions to a photon flux simulating the visible portion of the solar spectrum were made. The results obtained will be presented in detail and interpreted in relation to other data available for these emulsions.

Scott, B. W.; Voorhies, H. G.

1972-01-01

27

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

E-print Network

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

Richardson, John

28

Measuring the Turbulent Solar Wind  

NASA Astrophysics Data System (ADS)

The slow solar wind is turbulent, a fact that may explain the variability of the slow wind at Earth. But the nature and strength of the turbulence has been hard to quantify because measurements have been limited to in-situ detection of variations in measurable parameters. Remote imaging of comet tails offers a unique opportunity to study the paths of localized "test particles" in the solar wind, and to analyze the motion in the same way that hydrodynamicists might study turbulence in water with test particles. We report on a careful analysis of the motion of 230 individually tracked features in the tail of a comet observed with STEREO/HI-1, which interacted strongly with the solar wind between 0.2 and 0.3 AU during the observation period, and draw deep conclusions about the nature of solar wind variability.

DeForest, Craig; Matthaeus, William; Howard, Tim

2015-04-01

29

Wind and solar powered turbine  

NASA Technical Reports Server (NTRS)

A power generating station having a generator driven by solar heat assisted ambient wind is described. A first plurality of radially extendng air passages direct ambient wind to a radial flow wind turbine disposed in a centrally located opening in a substantially disc-shaped structure. A solar radiation collecting surface having black bodies is disposed above the fist plurality of air passages and in communication with a second plurality of radial air passages. A cover plate enclosing the second plurality of radial air passages is transparent so as to permit solar radiation to effectively reach the black bodies. The second plurality of air passages direct ambient wind and thermal updrafts generated by the black bodies to an axial flow turbine. The rotating shaft of the turbines drive the generator. The solar and wind drien power generating system operates in electrical cogeneration mode with a fuel powered prime mover.

Wells, I. D.; Koh, J. L.; Holmes, M. (inventors)

1984-01-01

30

Solar wind stagnation near comets  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

31

Wind and Solar Curtailment: Preprint  

SciTech Connect

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

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

2013-09-01

32

Highly Alfvenic Slow Solar Wind  

NASA Technical Reports Server (NTRS)

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

Roberts, D. Aaron

2010-01-01

33

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

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

Persistence of solar wind features  

NASA Technical Reports Server (NTRS)

Using data from the plasma and magnetometer experiments on board the Voyagers 1 and 2 during the approach to Jupiter, solar wind persistence is investigated over the period from January 1978 (Voyager 1 passing by Voyager 2) through February 1979. The trajectories of both spacecraft provided a unique opportunity to study the radial evolution and variation of the solar wind over about 3 AU, and to analyze the persistence of solar wind features along the radially increasing separation distance of both Voyagers. Some emphasis is placed on a period of DOY (day of year) 152 through 212, 1978, in which the observed propagation delay time of solar wind signatures between both Voyagers significantly deviates from the expected delay time. A decrease in the correlation coefficient of the corresponding Voyager 1 and 2 data profiles indicates a remarkable change of the solar wind flow. This period in question coincides to a great extent with the interval V of June-July 1978, selected by STIP (Study of Travelling Interplanetary Phenomena).

Rucker, H. O.; Rabl, G. K. F.; Desch, M. D.

1986-01-01

36

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

E-print Network

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

37

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

E-print Network

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

California at Berkeley, University of

38

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

Microsoft Academic Search

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

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

2009-01-01

39

The Heating & Acceleration of the Solar Wind  

E-print Network

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

Wurtele, Jonathan

40

THE SOLAR WIND PLASMA Dr. Joe Borovsky  

E-print Network

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

Shyy, Wei

41

Compressibility of solar wind Bogdan A. Hnat  

E-print Network

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

Sengun, Mehmet Haluk

42

The solar wind throughout the solar cycle  

NASA Astrophysics Data System (ADS)

The existence of solar corpuscular radiation (SCR) was conjectured by Biermann (1951) based on the fact that the ion tails of comets always point radially away from the Sun. Earlier it had been thought that this was due to solar radiation pressure, but when the relevant cross-sections were measured it became clear that these were far too small. This is visible in Figure 3.1, where stars can be seen shining through the ion tail of comet Hale-Bopp, one of the more spectacular sights in the sky of the 20th century. Parker (1958) provided the first theoretical description of the SCR in terms of a supersonic magnetized fluid. He coined the term "solar wind" in order to set it apart from other ideas of a (subsonic) solar breeze that were around at the time. The solar wind was ultimately observed in the early 1960s by the Soviets and independently with the American Mariner 2 mission to Venus (Gringauz et al., 1961; Neugebauer and Snyder, 1962). An excellent account of these early developments is given by Parker (2001).

von Steiger, Rudolf

43

Imaging the Variable Solar Wind  

NASA Astrophysics Data System (ADS)

With the advent of wide-field Thomson scattering imagery from STEREO/SECCHI, it is possible to image the solar wind continuously from its origin in the low corona to large fractions of 1AU from the Sun. Although it is sensitive only to non-stationary density structures, Thomson imaging yields morphological insight and global perspective that are not directly available from in-situ data. I will review recent work on both large and small scale analysis. On large scales, it is now possible to track well-presented CMEs from the pre-eruptive structure to impact with in-situ probes, yielding positive identification of flux rope structure based on both positively tracked morphology and direct magnetic measurement. In some cases, plasma detected in-situ can be positively identified with particular pieces of pre-eruptive anatomy in the low corona. Some observed large-scale features are as-yet unexplained. In quiet solar wind, small ejecta and blobs are readily distinguished from disconnection events that may be identified by their morphology, and all can be tracked through the Alfvén surface boundary at 20-50 Rs into the solar wind proper. In the HI-1 field of view, the solar wind takes on a flocculated appearance, though most of the individual features lose image structure and cannot be tracked across the entire field of view. Analysis of individual ejecta and of the statistical properties of the flocculation pattern is yielding insights into the nature of fluctuations and origin of variability in the slow solar wind.

DeForest, C.; Howard, T. A.; Matthaeus, W. H.

2013-05-01

44

Eight-moment approximation solar wind models  

NASA Technical Reports Server (NTRS)

Heat conduction from the corona is important in the solar wind energy budget. Until now all hydrodynamic solar wind models have been using the collisionally dominated gas approximation for the heat conductive flux. Observations of the solar wind show particle distribution functions which deviate significantly from a Maxwellian, and it is clear that the solar wind plasma is far from collisionally dominated. We have developed a numerical model for the solar wind which solves the full equation for the heat conductive flux together with the conservation equations for mass, momentum, and energy. The equations are obtained by taking moments of the Boltzmann equation, using an 8-moment approximation for the distribution function. For low-density solar winds the 8-moment approximation models give results which differ significantly from the results obtained in models assuming the gas to be collisionally dominated. The two models give more or less the same results in high density solar winds.

Olsen, Espen Lyngdal; Leer, Egil

1995-01-01

45

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

46

Solar wind plasma : kinetic properties and micro-instabilities  

E-print Network

The kinetic properties of ions in the solar wind plasma are studied. Observations of solar wind +H and +2He by the Faraday Cup instrument component of the Solar Wind Experiment on the Wind spacecraft show that these ions ...

Kasper, Justin Christophe, 1977-

2003-01-01

47

Wind loading on solar collectors  

Microsoft Academic Search

The present design methodology for the determination of wind loading on the various solar collectors were 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, were compared with those obtained by using the methodology of the ASCE Task

S. Bhaduri; L. M. Murphy

1985-01-01

48

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

E-print Network

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

California at Berkeley, University of

49

Evolution of Solar Wind Heavy Ions over the Solar Cycle  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

50

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

51

Wind loading on solar collectors  

NASA Astrophysics Data System (ADS)

The present design methodology for the determination of wind loading on the various solar collectors were 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, were 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, were 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

52

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

53

The Solar Wind Ion Composition Spectrometer  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

54

Pc Micropulsations with Discrete, Latitude-Dependent Frequencies  

Microsoft Academic Search

In this report we present an example of continuous Pc micropulsations with discrete, latitude-dependent frequencies in the H (north-south) components. These pulsations were recorded simultaneously at seven ground-based magnetometer stations ranging in geomag- netic latitude from 58.5øN to 77.7øN. The pulsations exhibited four discrete spectral peaks in the H components (\\/ -- 14.7, 6.6, 4.1, and 1.3 mHz; T --

Gordon Rostoker; John C. Samson

1972-01-01

55

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.

56

Solar wind thermal electron distributions  

SciTech Connect

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

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

1991-01-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

59

Simulations of Solar Wind Turbulence  

NASA Technical Reports Server (NTRS)

Recently we have restructured our approach to simulating magnetohydrodynamic (MHD) turbulence in the solar wind. Previously, we had defined a 'virtual' heliosphere that contained, for example, a tilted rotating current sheet, microstreams, quasi-two-dimensional fluctuations as well as Alfven waves. In this new version of the code, we use the global, time-stationary, WKB Alfven wave-driven solar wind model developed by Usmanov and described in Usmanov and Goldstein [2003] to define the initial state of the system. Consequently, current sheets, and fast and slow streams are computed self-consistently from an inner, photospheric, boundary. To this steady-state configuration, we add fluctuations close to, but above, the surface where the flow become super-Alfvenic. The time-dependent MHD equations are then solved using a semi-discrete third-order Central Weighted Essentially Non-Oscillatory (CWENO) numerical scheme. The computational domain now includes the entire sphere; the geometrical singularity at the poles is removed using the multiple grid approach described in Usmanov [1996]. Wave packets are introduced at the inner boundary such as to satisfy Faraday's Law [Yeh and Dryer, 1985] and their nonlinear evolution are followed in time.

Goldstein, Melvyn L.; Usmanov, A. V.; Roberts, D. A.

2008-01-01

60

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

61

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

E-print Network

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

Richardson, John

62

Sources of solar wind over the solar activity cycle  

PubMed Central

Fast solar wind has been recognized, about 40 years ago, to originate in polar coronal holes (CHs), that, since then, have been identified with sources of recurrent high speed wind streams. As of today, however, there is no general consensus about whether there are, within CHs, preferential locations where the solar wind is accelerated. Knowledge of slow wind sources is far from complete as well. Slow wind observed in situ can be traced back to its solar source by backward extrapolation of magnetic fields whose field lines are streamlines of the outflowing plasma. However, this technique often has not the necessary precision for an indisputable identification of the region where wind originates. As the Sun progresses through its activity cycle, different wind sources prevail and contribute to filling the heliosphere. Our present knowledge of different wind sources is here summarized. Also, a Section addresses the problem of wind acceleration in the low corona, as inferred from an analysis of UV data, and illustrates changes between fast and slow wind profiles and possible signatures of changes along the solar cycle. A brief reference to recent work about the deep roots of solar wind and their changes over different solar cycles concludes the review. PMID:25685421

Poletto, Giannina

2012-01-01

63

Solar Wind Interaction with Venus  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

64

Expansion effects on solar wind hybrid simulations  

SciTech Connect

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

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

2013-06-13

65

The abundances of elements and isotopes in the solar wind  

NASA Technical Reports Server (NTRS)

Studies of the chemical and isotopic composition of the solar wind are reviewed. Solar wind abundance measurements are discussed and solar wind, coronal, and photospheric abundances for elements between H and Fe are presented. Also, consideration is given to the determination of the solar wind isotopic composition of the noble gases using foil collection techniques and the observation of solar wind heavy ions with the mass per charge spectrometer on ISEE-3. Other topics include solar wind observations with solid state detectors, solar wind abundances in the magnetosheath and the plasma sheet, and high-mass resolution measurements of chemical elements and isotopes in the solar wind.

Gloeckler, George; Geiss, Johannes

1988-01-01

66

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

NASA Astrophysics Data System (ADS)

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 fast and slow solar wind rely on the superradial expansion of the magnetic field to account for the observed solar wind speed variation. We investigate the solar wind in the inner corona using the Wang-Sheeley-Arge (WSA) coronal model incorporating a new empirical magnetic topology-velocity relationship calibrated for use at 0.1 AU. In this study the empirical solar wind speed relationship was determined by using Helios perihelion observations, along with results from Riley et al. (2003) and Schwadron et al. (2005) as constraints. The new relationship was tested by using it to drive the ENLIL 3-D MHD solar wind model and obtain solar wind parameters at Earth (1.0 AU) and Ulysses (1.4 AU). The improvements in speed, its variability, and the occurrence of high-speed enhancements provide confidence that the new velocity relationship better determines the solar wind speed in the outer corona (0.1 AU). An analysis of this improved velocity field within the WSA model suggests the existence of two distinct mechanisms of the solar wind generation, one for fast and one for slow solar wind, implying that a combination of present theories may be necessary to explain solar wind observations.

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

2011-03-01

67

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

E-print Network

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

Richardson, John

68

Global Network of Slow Solar Wind  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

69

DSCOVR High Time Resolution Solar Wind Measurements  

NASA Technical Reports Server (NTRS)

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

Szabo, Adam

2012-01-01

70

DSCOVR High Time Resolution Solar Wind Measurements  

NASA Astrophysics Data System (ADS)

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

Szabo, A.

2012-12-01

71

Hydromagnetic heating in the solar wind  

NASA Technical Reports Server (NTRS)

Hydromagnetic heating in the solar wind was investigated using the heating model in which fast-mode hydromagnetic waves propagate outward from below the base and deposit energy by collisionless damping. Ray paths were found by solving Hamilton's equations. As the ray propagates along its path, it will damp, supplying thermal energy to the solar wind gas. The strong agreement of these results with observations is clear indication that the primary nonthermal heat source in the solar wind is the collisionless damping of hydromagnetic waves.

Hartle, R.

1972-01-01

72

Global Network of Slow Solar Wind N. U. Crooker1  

E-print Network

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

Zhao, Xuepu

73

The Solar Wind and Its Interaction with the Interstellar Medium  

E-print Network

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

Richardson, John

74

Acceleration and heating of the solar wind  

NASA Technical Reports Server (NTRS)

Some of the competing theories of solar wind acceleration and heating are reviewed, and the observations that are required to distinguish among them are discussed. In most cases what is required is measurement of plasma velocity and temperature and magnetic field, as near the sun as possible and certainly inside 20 solar radii; another critical aspect of this question is determining whether a turbulent envelope exists in this inner region, and if so, defining its properties. Plasma and magnetic observations from the proposed Solar Probe mission would thus yield a quantum jump in our understanding of the dynamics of the solar wind.

Barnes, A.

1978-01-01

75

Turbulent spectra in the solar wind plasma  

NASA Astrophysics Data System (ADS)

Observations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of -5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length scales remains an unresolved paradox of modern turbulence theories, raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time-dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfvénic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (-5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively convect density fluctuations.

Shaikh, Dastgeer; Zank, G. P.

2010-04-01

76

The solar wind in the outer heliosphere  

E-print Network

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

Richardson, John D.

77

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

78

Magnetic energy flow in the solar wind.  

NASA Technical Reports Server (NTRS)

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

Modisette, J. L.

1972-01-01

79

Empirical Solar Wind Forecasting from the Chromosphere  

E-print Network

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

Robert J. Leamon; Scott W. McIntosh

2007-01-12

80

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

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

The Genesis Solar Wind Sample Return Mission  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

83

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

E-print Network

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

Juan Carlos Martinez Oliveros; Daniel Ricardo Izquierdo P

2005-08-02

84

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

85

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.

86

Solar Wind Forecasting with Coronal Holes  

E-print Network

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

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

2007-01-09

87

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

E-print Network

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

California at Berkeley, University of

88

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

E-print Network

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

Richardson, John

89

Solar wind and solar energetic particles: origins and effects  

NASA Astrophysics Data System (ADS)

The paper reports about several actual problems of the solar wind and solar energetic particle studies. Primary focus is on unsolved questions. The clear and sharp boundary in the phase space between solar wind plasma particle populations and “solar energetic particles” does not exist. Because of this separate consideration of “solar energetic particles” has only limited applicability and needs some reservations, which should be clearly stated and not forgotten to avoid possible errors and misinterpretations, which sometimes happen in the literature. In any case, the solar wind particles often serve as a big reservoir for acceleration (or cooling) of less abundant energetic particles. Solar wind and solar energetic particles are just two selected populations (big and small) in their joint distribution functions. It is very difficult and even impossible in many instances to have demarcation between particle populations in the energy space or indicate their ultimate “origins” in the coordinate space. It is because of the absence of localized “accelerators”, “heaters” or “sources” of particles. All these three categories mentioned above often have very limited physical meaning, but sometimes they can be useful and localized in the momentum and coordinate space. We are still too far from complete knowledge and understanding of many relevant questions in this regard.

Veselovsky, Igor S.

90

Titan's interaction with the supersonic solar wind  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

91

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

92

The Solar Wind Ion Analyzer for MAVEN  

NASA Astrophysics Data System (ADS)

The Solar Wind Ion Analyzer (SWIA) on the MAVEN mission will measure the solar wind ion flows around Mars, both in the upstream solar wind and in the magneto-sheath and tail regions inside the bow shock. The solar wind flux provides one of the key energy inputs that can drive atmospheric escape from the Martian system, as well as in part controlling the structure of the magnetosphere through which non-thermal ion escape must take place. SWIA measurements contribute to the top level MAVEN goals of characterizing the upper atmosphere and the processes that operate there, and parameterizing the escape of atmospheric gases to extrapolate the total loss to space throughout Mars' history. To accomplish these goals, SWIA utilizes a toroidal energy analyzer with electrostatic deflectors to provide a broad 360?×90? field of view on a 3-axis spacecraft, with a mechanical attenuator to enable a very high dynamic range. SWIA provides high cadence measurements of ion velocity distributions with high energy resolution (14.5 %) and angular resolution (3.75?×4.5? in the sunward direction, 22.5?×22.5? elsewhere), and a broad energy range of 5 eV to 25 keV. Onboard computation of bulk moments and energy spectra enable measurements of the basic properties of the solar wind at 0.25 Hz.

Halekas, J. S.; Taylor, E. R.; Dalton, G.; Johnson, G.; Curtis, D. W.; McFadden, J. P.; Mitchell, D. L.; Lin, R. P.; Jakosky, B. M.

2013-11-01

93

Evidence for solar wind modulation of lightning  

NASA Astrophysics Data System (ADS)

The response of lightning rates over Europe to arrival of high speed solar wind streams at Earth is investigated using a superposed epoch analysis. Fast solar wind stream arrival is determined from modulation of the solar wind V y component, measured by the Advanced Composition Explorer spacecraft. Lightning rate changes around these event times are determined from the very low frequency arrival time difference (ATD) system of the UK Met Office. Arrival of high speed streams at Earth is found to be preceded by a decrease in total solar irradiance and an increase in sunspot number and Mg II emissions. These are consistent with the high speed stream’s source being co-located with an active region appearing on the Eastern solar limb and rotating at the 27 d period of the Sun. Arrival of the high speed stream at Earth also coincides with a small (˜1%) but rapid decrease in galactic cosmic ray flux, a moderate (˜6%) increase in lower energy solar energetic protons (SEPs), and a substantial, statistically significant increase in lightning rates. These changes persist for around 40 d in all three quantities. The lightning rate increase is corroborated by an increase in the total number of thunder days observed by UK Met stations, again persisting for around 40 d after the arrival of a high speed solar wind stream. This result appears to contradict earlier studies that found an anti-correlation between sunspot number and thunder days over solar cycle timescales. The increase in lightning rates and thunder days that we observe coincides with an increased flux of SEPs which, while not being detected at ground level, nevertheless penetrate the atmosphere to tropospheric altitudes. This effect could be further amplified by an increase in mean lightning stroke intensity that brings more strokes above the detection threshold of the ATD system. In order to remove any potential seasonal bias the analysis was repeated for daily solar wind triggers occurring during the summer months (June to August). Though this reduced the number of solar wind triggers to 32, the response in both lightning and thunder day data remained statistically significant. This modulation of lightning by regular and predictable solar wind events may be beneficial to medium range forecasting of hazardous weather.

Scott, C. J.; Harrison, R. G.; Owens, M. J.; Lockwood, M.; Barnard, L.

2014-05-01

94

Latitudinal dynamics of steady solar wind flows  

NASA Technical Reports Server (NTRS)

In many previous studies, it has been assumed that the streamlines of the solar wind are in a purely radial direction beyond a few solar radii. Therefore, the nonradial modulations by the magnetic force and gas pressure is neglected at large heliocentric distances. The work reported in this paper includes a two-dimensional magnetohydrodynamic (MHD) study of the latitudinal structure of solar wind flows. The dynamical effects of the interplanetary magnetic field (IMF) are investigated by MHD solutions and by comparing them with both one-dimensional and two-dimensional hydrodynamic (HD) solutions. The corotational effect of the sun and the influence of transient events in the solar atmosphere are neglected. With such a simplification, the latitudinal structure of the steady solar wind is controlled by the dynamic balance of the magnetic force and the gas pressure. Several different patterns of the evolution of the solar wind latitudinal structure are exhibited in the calculation. The results indicate the existence of a proton number density maximum at the magnetic neutral line, whether or not there is a density maximum or minimum at the inner boundary. The drift motion of magnetic field lines toward the magnetic neutral line enhances the magnetic field strength around the neutral sheet, which may provide a possible explanation of the discrepancy between the measured IMF at 1 AU and that extrapolated from the photospheric magnetic field by the current source-surface modeling.

Yang, W.-H.; Schunk, R. W.

1991-01-01

95

Solar wind modulation of UK lightning  

NASA Astrophysics Data System (ADS)

The response of lightning rates in the UK to arrival of high speed solar wind streams at Earth is investigated using a superposed epoch analysis. The fast solar wind streams' arrivals are determined from modulation of the solar wind Vy component, measured by the Advanced Composition Explorer (ACE) spacecraft. Lightning rate changes around these event times are then determined from the very low frequency Arrival Time Difference (ATD) system of the UK Met Office. Arrival of high speed streams at Earth is found to be preceded by a decrease in total solar irradiance and an increase in sunspot number and Mg II emissions. These are consistent with the high speed stream's source being co-located with an active region appearing on the Eastern solar limb and rotating at the 27 day rate of the Sun. Arrival of the high speed stream at Earth also coincides with a rapid decrease in cosmic ray flux and an increase in lightning rates over the UK, persisting for around 40 days. The lightning rate increase is corroborated by an increase in the total number of thunder days observed by UK Met stations, again for around 40 days after the arrival of a high speed solar wind stream. This increase in lightning may be beneficial to medium range forecasting of hazardous weather.

Davis, Chris; Harrison, Giles; Lockwood, Mike; Owens, Mathew; Barnard, Luke

2013-04-01

96

Solar wind ion composition and charge states  

NASA Technical Reports Server (NTRS)

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

vonSteiger, R.

1995-01-01

97

Flow Sources and Formation Laws of Solar Wind Streams  

NASA Astrophysics Data System (ADS)

The large-scale stream structure of the solar wind flow is studied in the main acceleration zone from 10 to 40 solar radii from the Sun. Three independent sets of experimental data were used: radio astronomical observations of radio wave scattering using the large radio telescopes of the Lebedev Physical Institute; dual-frequency Doppler solar wind speed measurements from the Ulysses Solar Corona Experiment during the spacecraft's two solar conjunctions in summer 1991 and winter 1995; solar magnetic field strength and configuration computed from Wilcox Solar Observatory data. Both the experimental data on the position of the transonic region of the solar wind flow and the solar wind speed estimates were used as parameters reflecting the intensity of the solar wind acceleration process. Correlation studies of these data with the magnetic field strength in the solar corona revealed several types of solar wind flow differing in their velocities and the location of their primary acceleration region.

Lotova, N. A.; Obridko, V. N.; Vladimirskii, K. V.; Bird, M. K.; Janardhan, P.

2002-01-01

98

Shock heating of the solar wind plasma  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

99

Wind loading on solar collectors  

NASA Astrophysics Data System (ADS)

A review is presented of wind models for the highest speeds, gusts, energy spectra and subsequent forces to be expected on heliostats in a given region. The calculations depend on local meteorological data and several assumptions regarding the behavior of windspeed and direction with height. Current models are found to be too conservative. Extreme value calculations are recommended for each site. Several deficiencies are noted in current ANSI code procedures for deriving the wind energy spectra. It is suggested that the installation of a fence around a heliostat field may be effective in reducing wind loading.

Bhaduri, S.; Murphy, L. M.

1984-12-01

100

Comparison of the Genesis solar wind regime algorithm results with solar wind composition observed by ACE  

SciTech Connect

Launched on 8 August 2001, the NASA Genesis mission is now collecting samples of the solar wind in various materials, and will return those samples to Earth in 2004 for analysis. A primary science goal of Genesis is the determination of the isotopic and elemental composition of the solar atmosphere from the solar wind material returned. In particular, Genesis will provide measurements of those species that are not provided by solar and in situ observations. We know from in situ measurements that the solar wind exhibits compositional variations across different types of solar wind flows. Therefore, Genesis exposes different collectors to solar wind originating from three flow types: coronal hole, coronal mass ejection (CME), and interstream flows. Flow types are identified using in situ measurements of solar wind protons, alphas, and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent collector deployment on Genesis act autonomously. We present an assessment of composition variations of O, He, and Mg ions observed by ACE/SWICS concurrent with Genesis observations, and compare these to the Genesis algorithm decisions. Not only does this serve as a test of the algorithm, the compilation of composition vs. regime will be important for comparison to the abundances determined from sample analysis at the end of the mission.

Reisenfeld, D. B. (Daniel B.); Steinberg, J. T (John T.); Barraclough, B. L. (Bruce L.); Dors, E. E. (Eric E.); Weins, R. C. (Roger C.); Neugebauer, Marcia; Reinard, A. (Alysha)

2002-01-01

101

Solar thermal and wind energy power source  

SciTech Connect

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 energy driving the turbine. The turbine includes an axial drive shaft driving a gear train in turn driving an electric generator, or the like.

Argo, W.H.

1980-09-23

102

Geomagnetic activity: Dependence on solar wind parameters  

NASA Technical Reports Server (NTRS)

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

Svalgaard, L.

1977-01-01

103

Magnetosphere II: The Solar Wind Strikes Back!  

NSDL National Science Digital Library

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

Tom Bridgman

2002-03-01

104

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.

105

Adiabatic cooling of solar wind electrons  

NASA Technical Reports Server (NTRS)

In thermally driven winds emanating from regions in the solar corona with base electron densities of n0 not less than 10 exp 8/cu cm, a substantial fraction of the heat conductive flux from the base is transfered into flow energy by the pressure gradient force. The adiabatic cooling of the electrons causes the electron temperature profile to fall off more rapidly than in heat conduction dominated flows. Alfven waves of solar origin, accelerating the basically thermally driven solar wind, lead to an increased mass flux and enhanced adiabatic cooling. The reduction in electron temperature may be significant also in the subsonic region of the flow and lead to a moderate increase of solar wind mass flux with increasing Alfven wave amplitude. In the solar wind model presented here the Alfven wave energy flux per unit mass is larger than that in models where the temperature in the subsonic flow is not reduced by the wave, and consequently the asymptotic flow speed is higher.

Sandbaek, Ornulf; Leer, Egil

1992-01-01

106

Diagnostics of the Solar Wind Plasma  

NASA Astrophysics Data System (ADS)

The solar wind is a fully ionized plasma, coming from the outer atmosphere of the Sun, the so-called solar corona, which expands as a supersonic flow into the interplanetary medium [55]. The first observations indicating that the Sun might be emitting a wind were made by Biermann in 1946 of comet tails [1], which are observed to point away from the Sun. Comets usually exhibit two tails: a dust tail driven by the radiation pressure and a plasma tail, which points in slightly different directions pushed by the “solar corpuscular radiation” of the Sun. In 1958, E.N. Parker explained theoretically this “particle radiation” using a simple fluid model [55], showing that the solar atmosphere is not in hydrostatic equilibrium but must expand into the interplanetary medium as a wind. The existence of this solar wind was debated until it was indeed confirmed by spacecraft Lunik 2 and 3 [16] and continuously observed by Mariner 2 [53]. The Parker theory is discussed fully in Chap. 7 (Velli).

Issautier, K.

107

Solar wind composition measurements by the Ulysses SWICS experiment during transient solar wind flows  

NASA Technical Reports Server (NTRS)

For the March/April 1991 time period, the alpha/proton abundance ratio, the proton kinetic temperature and speed distributions, and the relative abundance of O(+7) to O(+6) is determined over each 13-minute duty cycle of the Solar Wind Ion Composition Spectrometer (SWICs) experiment on Ulysses. The ratio O(+7)/O(+6) (as a relative measure of ionization temperature) is shown to be useful in identifying possible coronal mass ejection (CME) events. We report measurements of silicon/oxygen abundance ratios and silicon and oxygen charge state distributions in the solar wind during a CME event and compare these compositions to a 'normal' solar wind time period.

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

1993-01-01

108

Solar wind interaction with planetary objects  

Microsoft Academic Search

The interaction of the solar-wind plasma with solar-system objects is examined in a review of recent observational data, in situ measurements, and theoretical calculations. Topics discussed include the moon as a nonconducting body with only small remnants of magnetic field, producing a conical wake with no shock wave and a rarefaction\\/compression wave marking the penumbra; Venus and Mars as conducting

V. Formisano

1984-01-01

109

Case Studies of Extreme Solar Wind in the Current Solar Cycle  

NASA Astrophysics Data System (ADS)

We examine solar wind ion characteristics and solar origins for typical and extreme solar wind speed cases, utilizing near-Earth (OMNI) and STEREO data. Sources of the solar wind are known to be linked to the phase of the solar cycle and include coronal holes, coronal mass ejections, and multiple cycle-dependent sources for the so-called “slow” solar wind. This past solar minimum was characterized by weak transients and sustained periods of slow solar wind, and included cases of “slow” and “slower” solar wind stream interactions. In contrast, intervals around solar maximum have included extremely fast interplanetary coronal mass ejections, with one such ICME observed in situ by STEREO A exceeding 2000 km/s at 1 AU. We will compare extreme cases of slow and fast solar wind observed in situ by STEREO to general solar wind ion parameters, particularly for proton and iron ions.

Galvin, Antoinette; Simunac, Kristin

2015-04-01

110

Solar Wind Interaction with Dusty Cometary Coma  

NASA Astrophysics Data System (ADS)

Interaction of Solar wind with dusty cometary coma is considered. In contrast to previous descriptions of this interaction we take into account the influence of charged dust of cometary coma on bow shock formation. Our description is performed on the basis of a self-consistent model which takes into account solar radiation; dust particle charging; evaporation and formation of neutral particles; photoionization; electric fields; the evolution of solar wind ions, cometary ions and dust particles; as well as the dust charge variation. It is shown that the presence of dust in cometary coma can modify shock wave formed as a result of Solar wind interaction with a comet. The outer shock wave (bow shock) can be considered as an ion acoustic shock wave modified by dust particle charging process. Possible formation of dust structures in the region of the interaction of Solar wind with cometary coma is discussed. The developed model allows us to determine the shock front structure. The calculations are performed for a comet situated at the distance of 1 AU from the Sun. For typical cometary nucleus size of about 1 km and rather dense dusty coma (exceeding million of cubic centimeters near the comet nucleus) the bow shock formed as a result of the interaction of Solar wind with the coma is expected to be related to the anomalous dissipation due to the dust particle charging. The bow shock is similar, by its origin, to the shocks observed by Nakamura et al. (Phys. Rev. Lett. 83, 1602 (1999)) and Luo et al. (Phys. Plasmas 6, 3455 (1999)) and those predicted theoretically (Popel et al., Phys. Plasmas 3, 4313 (1996); Popel et al., Phys. Plasmas 7, 2410 (2000)).

Popel, S. I.; Gisko, A. A.; Losseva, T. V.; Vladimirov, S. V.

111

Coronal Plumes in the Fast Solar Wind  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

112

Particle propagation channels in the solar wind  

NASA Technical Reports Server (NTRS)

The intensities of low energy solar-interplanetary electrons and ions at 1 AU occasionally change in a square wave manner. The changes may be increases or decreases and they typically have durations of from one hour to a few hours. In some cases these channels are bounded by discontinuities in the interplanetary field and the plasma properties differ from the surrounding solar wind. In one case solar flare particles were confined to a channel of width 3 x 10 to the 6th km at Earth. At the Sun this dimension extrapolates to about 12,000 km, a size comparable to small flares.

Anderson, K. A.; Dougherty, W. M.

1987-01-01

113

The solar wind-magnetosphere energy coupling and magnetospheric disturbances  

Microsoft Academic Search

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

S.-I. Akasofu

1980-01-01

114

The Solar Wind, CMEs and the Origins of Heliospheric Activity  

E-print Network

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

115

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind  

E-print Network

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

Ng, Chung-Sang

116

Turbulent heating of the corona and solar wind: the heliospheric  

E-print Network

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

117

Measuring the Isotopic Composition of Solar Wind Noble Gases  

E-print Network

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

118

Magnetospheric cavity modes driven by solar wind dynamic pressure fluctuations  

E-print Network

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

119

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

120

SUBMITTED TO GRL 1 Thermal Anisotropies in the Solar Wind  

E-print Network

SUBMITTED TO GRL 1 E Thermal Anisotropies in the Solar Wind: vidence of Heating by Interstellar cyclotron instabilit s generated by newly created pickup ions and heats the thermal solar wind protons TO GRL 2 T Introduction he thermal anisotropy of the solar wind is the ratio between the temperatures p

Richardson, John

121

Magnetospheric responses to sudden and quasiperiodic solar wind variations  

E-print Network

Magnetospheric responses to sudden and quasiperiodic solar wind variations K.-H. Kim,1 C. A.e., magnetosphere, magnetosheath, and solar wind) because of the solar wind dynamic pressure variations and its high into the magnetosphere, the lower-latitude data on the nightside are important to monitor the external source variations

California at Berkeley, University of

122

Combined Solar and Wind Energy Systems  

NASA Astrophysics Data System (ADS)

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) and WT subsystems can supplement each other to cover building electrical load. In case of using PV/T collectors, the surplus of electricity, if not used or stored in batteries, can increase the temperature of the thermal storage tank of the solar thermal unit. The description of the experimental set-up of the suggested PV/T/WT system and experimental results are presented. In PV/T/WT systems the output from the solar part depends on the sunshine time and the output of the wind turbine part depends on the wind speed and is obtained any time of day or night. The use of the three subsystems can cover a great part of building energy load, contributing to conventional energy saving and environment protection. The PV/T/WT systems are considered suitable in rural and remote areas with electricity supply from stand-alone units or mini-grid connection. PV/T/WT systems can also be used in typical grid connected applications.

Tripanagnostopoulos, Y.; Souliotis, M.; Makris, Th.

2010-01-01

123

Solar Wind and Motion of Meteoroids  

E-print Network

The effect of nonradial component of solar wind is discussed from the qualitative point of view. It is shown that the direction of nonradial component is opposite in comparison with the direction used in papers dealing with orbital evolution of meteoroids.

Jozef Klacka

1999-10-04

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

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.

126

Identifying Wind and Solar Ramping Events: Preprint  

SciTech Connect

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

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

2013-01-01

127

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

128

Studying Solar Wind and Magnetosphere Interactions  

NSDL National Science Digital Library

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

129

Wind loading on solar collectors  

Microsoft Academic Search

A review is presented of wind models for the highest speeds, gusts, energy spectra and subsequent forces to be expected on heliostats in a given region. The calculations depend on local meteorological data and several assumptions regarding the behavior of windspeed and direction with height. Current models are found to be too conservative. Extreme value calculations are recommended for each

S. Bhaduri; L. M. Murphy

1984-01-01

130

Material Interactions with Solar Wind Ion Environments  

NASA Technical Reports Server (NTRS)

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

Minow, Joseph I.; McWilliams, Brett

2006-01-01

131

Solar wind measurements on Solar Orbiter: discovering the links between the solar wind and the atmosphere of our Sun  

NASA Astrophysics Data System (ADS)

The Solar Orbiter spacecraft, a collaborative mission between ESA and NASA, will be launched in 2017 and will include the Solar Wind Analyzer instrumentation suite. This space mission will allow for unprecedented data collection of particle characteristics near the Sun at various heliolatitudes during both the quiet and active phases of the solar cycle. The close proximity will allow for determination of the source regions on the sun for the observed events. Of particular interest will be the study of the origins of and processes related to solar energetic particles. This mission will lead to a better understanding of the Sun and the interstellar medium in our solar system. The Solar Wind Analyzer (SWA) suite is composed by a comprehensive set of sensors to characterize the Solar Wind plasma: the Electron Analyzer System to determine the properties of solar wind electrons, the Proton and Alpha Sensor to measure at high cadence the distribution functions of protons and alphas, and the Heavy Ion Sensor to analyze the minor ion components of the solar wind. As a result of the measurements SWA will take, we will be able to: Identify interplanetary shocks and characterize their spatial and temporal evolution; characterize the power spectra of density and velocity fluctuations upstream and downstream of shocks; study the heating and dissipation mechanisms at shocks at various radial distances and latitudes; and identify the mechanisms that heat thermal solar wind ions near shocks and determine the energy partition at shocks.

Livi, Stefano; Galvin, Antoinette; Kistler, Lynn; Collier, . Michael; Allegrini, Frederic; Lepri, Susan; Zurbuchen, Thomas

2012-07-01

132

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

133

Wind and IMP 8 Solar Wind, Magnetosheath and Shock Data  

NASA Technical Reports Server (NTRS)

The purpose of this project was to provide the community access to magnetosheath data near Earth. We provided 27 years of IMP 8 magnetosheath proton velocities, densities, and temperatures with our best (usually 1-min.) time resolution. IMP 8 crosses the magnetosheath twice each 125 day orbit, and we provided magnetosheath data for the roughly 27 years of data for which magnetometer data are also available (which are needed to reliably pick boundaries). We provided this 27 years of IMP 8 magnetosheath data to the NSSDC; this data is now integrated with the IMP 8 solar wind data with flags indicating whether each data point is in the solar wind, magnetosheath, or at the boundary between the two regions. The plasma speed, density, and temperature are provided for each magnetosheath point. These data are also available on the MIT web site ftp://space .mit.edu/pub/plasma/imp/www/imp.html. We provide ASCII time-ordered rows of data giving the observation time, the spacecraft position in GSE, the velocity is GSE, the density and temperature for protons. We also have analyzed and archived on our web site the Wind magnetosheath plasma parameters. These consist of ascii files of the proton and alpha densities, speeds, and thermal speeds. These data are available at ftp://space.mit.edu/pub/plasma/wind/sheath These are the two products promised in the work statement and they have been completed in full.

2004-01-01

134

Solar Wind Ablation of Terrestrial Planet Atmospheres  

NASA Technical Reports Server (NTRS)

Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

2009-01-01

135

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

E-print Network

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

Kallenrode, May-Britt

136

Preliminary retrieval of solar wind latitude distribution from Solar Wind Anisotropies\\/SOHO observations  

Microsoft Academic Search

The Solar Wind Anisotropies (SWAN) instrument on board the SOHO spacecraft measures Lyman alpha radiation emanating mainly from neutral hydrogen gas in the solar neighborhood. This gas is part of the local interstellar cloud in which the Sun and the heliosphere are immersed. Measurements of Lyman alpha can be used to infer the local cloud characteristics like the velocity and

E. Kyrölä; T. Summanen; W. Schmidt; T. Mäkinen; E. Quemerais; J.-L. Bertaux; R. Lallement; J. Costa

1998-01-01

137

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

138

Pluto's solar wind interaction: Collisional effects  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

139

Lower hybrid waves in the solar wind  

NASA Technical Reports Server (NTRS)

It is demonstrated that the frequently observed broad band low frequency electrostatic noise in the solar wind generally has a dominant lower hybrid component. These modes are probably produced by the anisotropic halos of the solar wind electron velocity distributions exhibiting 'heat flux' profiles and thus, are accompanied by broad band, 'hybrid-like' whistler waves. When the electron temperature is much larger than the ion temperature, these modes can also co-exist with the ion acoustic waves. Since lower hybrid modes propagate nearly normal to the interplanetary magnetic field lines, the ions can be transversely accelerated by these waves and attain the observed anisotropic and/or loss-cone-like distributions.

Marsch, E.; Chang, T.

1982-01-01

140

Solar wind triggering of substorm expansion onset  

NASA Technical Reports Server (NTRS)

A substantial fraction of all substorms with sudden onsets, as identified by minima in the AL index, are found to be triggered by the IMF. Analysis of data from the first six months of 1978 shows auroral zone magnetic records to be disturbed most of the time, with distinct substorms identified in 23 percent of these disturbed hours. For the subset of substorms with sharp onsets and corresponding solar wind data, 44 percent are found to be correlated with northward turnings of the IMF, while 28 percent occur during steady southward IMF. The results suggest that sharp substorm expansion onset is caused by a process internal to the magnetosphere which can be influenced by changes in the solar wind stress applied to the magnetosphere.

Mcpherron, R. L.; Terasawa, T.; Nishida, A.

1986-01-01

141

Solar wind thermally induced magnetic fluctuations.  

PubMed

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

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

2014-06-20

142

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

Federal Register 2010, 2011, 2012, 2013, 2014

...View Solar, LLC; Pheasant Run Wind, LLC; Pheasant Run Wind II, LLC; Tuscola Wind II, LLC; Mountain Wind Power, LLC; Mountain Wind Power II, LLC; Summerhaven Wind, LP; Notice of Effectiveness of Exempt Wholesale Generator or Foreign...

2013-12-18

143

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

144

Comparison Of The Genesis Solar Wind Regime Algorithm Results With Solar Wind Composition Observed By ACE  

NASA Astrophysics Data System (ADS)

Launched on 8 August 2001, the NASA Genesis mission is now collecting samples of the solar wind in various materials, and will return those samples to Earth in 2004 for analysis. A primary science goal of Genesis is the determination of the isotopic and elemental composition of the solar atmosphere from the solar wind material returned. In particular, Genesis will provide measurements of those species that are not provided by solar and in situ observations. We know from in situ measurements that the solar wind exhibits compositional variations across different types of solar wind flows. Therefore, Genesis exposes different collectors to solar wind originating from three flow types: coronal hole (CH), coronal mass ejection (CME), and interstream (IS) flows. Flow types are identified using in situ measurements of solar wind protons, alphas, and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent collector deployment on Genesis act autonomously. We present an assessment of composition variations of O, He, and Mg ions observed by ACE/SWICS concurrent with Genesis observations, and compare these to the Genesis algorithm decisions. Not only does this serve as a test of the algorithm, the compilation of composition vs. regime will be important for comparison to the abundances determined from sample analysis at the end of the mission. By applying the Genesis algorithm results to ACE/SWICS abundance and charge-state data, we show that the solar wind speed history can be used to further discriminate between the IS and CH flow types. By using a lower speed threshold for fast-to-slow than for slow-to-fast regime transitions, the Genesis algorithm effectively compensates for evolution effects that are due to transit to 1 AU. Furthermore, we show that for some signatures, CME composition is independent of speed, having a composition most typical of the slow wind < 400\\ km\\ s-1. However, differences between CMEs and the slow wind exist for He/H and O8+. Also, it is seen that larger helium enhancements are found in faster CMEs. The algorithm is successfully isolating the CME population, and thus protecting the CH and IS samples from contamination by CME material.

Reisenfeld, D. B.; Steinberg, J. T.; Barraclough, B. L.; Dors, E. E.; Wiens, R. C.; Neugebauer, M.; Zurbuchen, T. H.; Reinard, A.

2002-12-01

145

Solar Wind Charge Exchange During Geomagnetic Storms  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

146

Charge State Evolution in the Solar Wind. Radiative Losses in Fast Solar Wind Plasmas  

NASA Astrophysics Data System (ADS)

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.

2012-10-01

147

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

148

Latitude-dependence of Meter-Scale Surface Textures in Deuteronilus Mensae, Mars  

NASA Astrophysics Data System (ADS)

Meter-scale surface textures on lobate aprons and valley floors within the study region exhibit latitude dependence: knobby transitions to pitted terrain at higher latitudes. Observations suggest recent surface mantle degradation via ice sublimation.

Williams, R. M. E.

2006-03-01

149

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

150

Wind loading on solar concentrators: Some general considerations  

Microsoft Academic Search

A survey was 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

E. J. Roschke

1984-01-01

151

Large-scale structure of the fast solar wind  

Microsoft Academic Search

We present the results of a comprehensive study of the fast solar wind near solar minimum conditions using interplanetary scintillation (IPS) data taken with the EISCAT system in northern Scandinavia, and a recent extremely long baseline observation using both EISCAT and MERLIN systems. The results from IPS observations suggest that the fast wind inside 100 solar radii (R$\\\\odot$) can be

M. M. Bisi; R. A. Fallows; A. R. Breen; S. Rifai Habbal; R. A. Jones

2007-01-01

152

Note on the solar wind-induced drag on comets  

Microsoft Academic Search

The solar wind-induced drag on magnetically large comets is estimated as follows. As the comet approaches the sun, solar radiation striking the comet surface generates a surrounding neutral atmosphere which is subsequently ionized. The resulting plasma cloud interacts with the solar wind to produce a comet magnetosphere and associated collision-free shock wave. An approximation to the accompanying drag is obtained

Douglas E. Gonzales

1969-01-01

153

Solar wind turbulence as a driver of geomagnetic activity  

NASA Astrophysics Data System (ADS)

We carried out simultaneous analyses of interplanetary and geomagnetic datasets for the period of (solar Maunder) least (2009) and maximum (2002) solar activity to determine the nature of solar wind turbulence on geomagnetic activity using AE, ASY-D, and ASY-H indices. We determined the role played by Alfvénic fluctuations in the solar wind so as to find out the nature of the turbulence. Our analyses showed that solar wind turbulence play a role in geomagnetic processes at high latitudes during periods of low and high solar activity but does not have any effect at mid-low latitudes.

Ugwu, Ernest Benjamin Ikechukwu; Okeke, Francisca Nneka; Ugonabo, Obiageli Josephine

2015-04-01

154

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

155

Radial evolution of the energy density of solar wind fluctuations  

NASA Technical Reports Server (NTRS)

On the basis of transport theories appropriate to a radially expanding solar wind, we describe new results for the radial evolution of the energy density in solar wind fluctuations at MHD scales. These models include the effects of 'mixing' and driving as well as the possibility of non-isotropic MHD turbulence. Implications of these results for solar wind heating, cosmic ray diffusion and interstellar pick-up ions will also be addressed.

Zank, G. P.; Matthaeus, W. H.; Smith, C. W.

1995-01-01

156

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

157

Solar wind electron temperature and density measurements on the Solar Orbiter with thermal noise spectroscopy  

E-print Network

Solar wind electron temperature and density measurements on the Solar Orbiter with thermal noise of the plasma thermal noise analysis for the Solar Orbiter, in order to get accurate measurements of the total of their small mass and therefore large thermal speed, the solar wind electrons are expected to play a major role

California at Berkeley, University of

158

The ISPM solar-wind ion composition spectrometer  

NASA Technical Reports Server (NTRS)

The International Solar Polar Mission (ISPM) Solar-Wind Ion Composition Spectrometer which determines 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 145 km/sec (protons) to 1352 km/sec (Fe+8) is described. The instrument, which covers an energy per charge range from 110 eV/q to 66.7 keV/q in 13 min, combines an electrostatic analyzer with postacceleration, followed by a time-of-flight and energy measurement. Conditions and processes in the region of the corona where the solar wind is accelerated; location of the source regions of the solar wind in the corona; coronal heating processes; the extent and causes of variations in the composition of the solar atmosphere; plasma processes in the solar wind; acceleration of energetic particles in the solar wind; the thermalization and acceleration of interstellar ions in the solar wind, and their composition; and the composition and behavior of the plasma in the Jovian magnetosphere are studied.

Gloeckler, G.; Geiss, J.; Balsiger, H.; Fisk, L. A.; Gliem, F.; Ipavich, F. M.; Ogilvie, K. W.; Stuedemann, W.; Wilken, B.

1983-01-01

159

Solar wind magnetic turbulence at electron scales  

NASA Astrophysics Data System (ADS)

Turbulent cascade and its dissipation in collisionless space plasmas is a matter of debates for the last few decades. We study the solar wind magnetic turbulence from MHD to electron scales for quasi-perpendicular flow-to-field angles, that gives us measurement of k? spectra under the assumption of validity of the Taylor hypothesis. In the recent works of Alexandrova et al. [2009, 2010], Cluster measurements for different plasma conditions have been used to show that the turbulent spectrum in the free solar wind has a quasi-universal form: at MHD scales, a Kolmogorov's law ˜ k-5/3 was found, in agreement with previous observations. At scales smaller than the ion characteristic scales, a k-2.7 law was observed (in the frequency domain this spectrum covers ˜ [1,10] Hz range). The transition from one power-law to the other, that corresponds to ˜ [0.1,1] Hz, was found to be not universal: the spectral index varies here between -2 and -4. At scales k? e ˜ (0.1-1), where ? e is the electron gyroradius, (i.e. for f>10 Hz) the magnetic spectrum was found to be curved, indicating the onset of dissipation. The most intense spectra, resolved up to 100 Hz, could be approximated by an exponential law ˜ \\exp (-? {k? e}). This is the first observation of an exponential magnetic spectrum in space plasmas. We showed that ? e controls the turbulence level, as the dissipation scale does in the neutral fluid turbulence. These results were obtained considering 7 time periods in the free solar wind. Here we use a data set of 140 time periods to verify our results at electron scales. A comparison with the observations at the electron scales in the electron foreshock of the Earth's bow-shock reported by Sahraoui et al. [2009] will be also presented.

Alexandrova, O.; Lacombe, C.; Mangeney, A.; Maksimovic, M.; Saur, J.; Schwartz, S. J.; Mitchell, J.

2010-12-01

160

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

E-print Network

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

Webb, David F.

161

Genesis Solar Wind Samples: Update of Availability  

NASA Technical Reports Server (NTRS)

The Genesis mission collected solar wind atoms for 28 months with a variety of collectors. The array wafer collector availability is displayed in the online catalog. The purpose of this report is to update the community on availability of array wafer samples and to preview other collectors which are in the process of being added to the online catalog. A total of fifteen pure materials were selected based on engineering and science requirements. Most of the materials were semiconductor wafers which were mounted on the arrays.

Gonzalez, C. P.; Allums, K. K.; Allton, J. H.

2015-01-01

162

Gaseous isotope separation using solar wind phenomena  

PubMed Central

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

Wang, Chia-Gee

1980-01-01

163

Solar Winds-Magnetosphere energy transfer mechanisms  

NASA Astrophysics Data System (ADS)

Magnetic reconnection has been considered as the unique physical mechanism involved in energy transference from solar wind to magnetosphere. However, theoretical models of geomagnetic indices based on reconnection do not forecast properly geomagnetic activity suggesting that other mechanisms are implicated. The joint analysis of interplanetary data and geomagnetic activity data evidence the existence of an extra mechanism implicated in Sun-Earth interaction, which operates when the frequency of southern interplanetary magnetic field is of the order of 10-3 to 10-4 Hz.

Saiz, E.; Cerrato, Y.; Cid, C.

2006-12-01

164

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

165

Global Observations of Evolving 3D Solar Wind Structure  

NASA Astrophysics Data System (ADS)

Interplanetary scintillation (IPS) and Thomson scattered whitelight serve as effective tools to obtain a global view of the evolving solar wind structure, which is hardly accessible to in situ measurements using a limited number of spacecraft. This capability has been greatly enhanced owing to the use of the computer-assisted tomography (CAT) method. From a comparison between IPS reconstructions and photospheric magnetic field observations, we have identified the solar wind sources, which are consistent with plasma outflows observed by Hinode. We have also found a coronal parameter which is closely related to the terminal wind speed, and this result show excellent agreement with the nonlinear Alfven-wave-driven solar wind model. Our IPS observations over three cycles have revealed that the global distribution of solar wind speeds changes systematically depending on the solar activity. An excellent correlation between fast/slow wind areas and polar magnetic fields is demonstrated here. The important point to note is that the solar wind speed distribution for the current minimum differs significantly from that for the previous minimum. This difference is considered a consequence of weaker polar fields in the current minimum. Rapid evolution of the 3D solar wind structure associated with CMEs has been investigated from the combined analysis of IPS and whitelight observations. The results reveal global features of interplanetary CMEs and a drastic change in the expansion speed between the Sun and Earth orbit, suggesting important implications for the propagation dynamics of CMEs in the solar wind.

Tokumaru, M.; Fujiki, K.; Itoh, H.; Iju, T.; Kojima, M.

2012-08-01

166

Flow Sources and Formation Laws of the Solar Wind Streams  

NASA Astrophysics Data System (ADS)

The large-scale stream structure of the solar wind flow is studied in the main acceleration zone from 10 to 40 solar radii from the Sun. Four independent sets of experimental data were used: radio astronomical observations of radio wave scattering using the large radio telescopes of the Lebedev Physical Institute; dual-frequency Doppler solar wind speed measurements from the Ulysses Solar Corona Experiment during the spacecraft's solar conjunctions in summer 1991 and winter 1995; solar magnetic field strength and configuration computed from Wilcox Solar Observatory data; white-light coronagraph images obtained from ground-based eclipse and SOHO observations. Both the experimental data on the position of the transonic region of the solar wind flow and the solar wind speed estimates were used as parameters reflecting the intensity of the solar wind acceleration process. Correlation studies of these data with the magnetic field strength in the solar corona revealed several types of solar wind flow. Different types of streams arise in coronal regions differing by their magnetic field strength and structure. A total of four specific types, two of high-speed and two of low-speed, were revealed.

Lotova, N. A.; Obridko, V. N.; Vladimirskii, K. V.; Bird, M. K.; Janardhan, P.

2001-09-01

167

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

E-print Network

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

168

The structure of the solar wind in the inner heliosphere  

NASA Astrophysics Data System (ADS)

This dissertation is devoted to expanding our understanding of the solar wind structure in the inner heliosphere and variations therein with solar activity. Using spacecraft observations and numerical models, the origins of the large-scale structures and long-term trends of the solar wind are explored in order to gain insights on how our Sun determines the space environments of the terrestrial planets. I use long term measurements of the solar wind density, velocity, interplanetary magnetic field, and particles, together with models based on solar magnetic field data, to generate time series of these properties that span one solar rotation (˜27 days). From these time series, I assemble and obtain the synoptic overviews of the solar wind properties. The resulting synoptic overviews show that the solar wind around Mercury, Venus, Earth, and Mars is a complex co-rotating structure with recurring features and occasional transients. During quiet solar conditions, the heliospheric current sheet, which separates the positive interplanetary magnetic field from the negative, usually has a remarkably steady two- or four-sector structure that persists for many solar rotations. Within the sector boundaries are the slow and fast speed solar wind streams that originate from the open coronal magnetic field sources that map to the ecliptic. At the sector boundaries, compressed high-density and the related high-dynamic pressure ridges form where streams from different coronal source regions interact. High fluxes of energetic particles also occur at the boundaries, and are seen most prominently during the quiet solar period. The existence of these recurring features depends on how long-lived are their source regions. In the last decade, 3D numerical solar wind models have become more widely available. They provide important scientific tools for obtaining a more global view of the inner heliosphere and of the relationships between conditions at Mercury, Venus, Earth, and Mars. When I compare the model results with observations for periods outside of solar wind disturbances, I find that the models do a good job of simulating at least the steady, large-scale, ambient solar wind structure. However, it remains a challenge to accurately model the solar wind during active solar conditions. During these times, solar transients such as coronal mass ejections travel through interplanetary space and disturb the ambient solar wind, producing a far less predictable and modelable space environment. However, such conditions may have the greatest impact on the planets - especially on their atmospheres and magnetospheres. I therefore also consider the next steps in modeling, toward including active conditions.

Lee, Christina On-Yee

2010-12-01

169

Toward a 3D Kinetic Model of the Solar Wind  

NASA Astrophysics Data System (ADS)

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

Pierrard, V.; Pieters, M.

2014-05-01

170

Assessment of existing studies of wind loading on solar collectors  

Microsoft Academic Search

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

1981-01-01

171

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

172

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

Microsoft Academic Search

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

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

1991-01-01

173

Simulation of lunar carbon chemistry. I - Solar wind contribution  

Microsoft Academic Search

Simulation experiments were conducted to identify the role of solar and lunar winds in the evolution of lunar carbon chemistry. Major conclusions are that (1) implantation of solar wind C, D, and N ions in silicates synthesizes small molecules that can be released into vacuum either by ion sputtering or by heating; (2) this synthesis is highly specific when compared

J. P. Bibring; J. Chaumont; Y. Langevin; M. Maurette; A. L. Burlingame; P. C. Wszolek

1974-01-01

174

New Insights into Solar Wind Physics from SOHO  

E-print Network

The Solar and Heliospheric Observatory (SOHO) was launched in December 1995 with a suite of instruments designed to answer long-standing questions about the Sun's internal structure, its extensive outer atmosphere, and the solar wind. This paper reviews the new understanding of the physical processes responsible for the solar wind that have come from the past 8 years of SOHO observations, analysis, and theoretical work. For example, the UVCS instrument on SOHO has revealed the acceleration region of the fast solar wind to be far from simple thermal equilibrium. Evidence for preferential acceleration of ions, 100 million K ion temperatures, and marked departures from Maxwellian velocity distributions all point to specific types of collisionless heating processes. The slow solar wind, typically associated with bright helmet streamers, has been found to share some of the nonthermal characteristics of the fast wind. Abundance measurements from spectroscopy and visible-light coronagraphic movies from LASCO have led to a better census of the plasma components making up the slow wind. The origins of the solar wind in the photosphere and chromosphere have been better elucidated with disk spectroscopy from the SUMER and CDS instruments. Finally, the impact of the solar wind on spacecraft systems, ground-based technology, and astronauts has been greatly aided by having continuous solar observations at the Earth-Sun L1 point, and SOHO has set a strong precedent for future studies of space weather.

Steven R. Cranmer

2004-09-10

175

Turbulence in the solar wind: Kinetic effects  

NASA Technical Reports Server (NTRS)

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

Goldstein, M. L.

1995-01-01

176

Venus Ionosphere and Solar Wind Interaction  

NASA Astrophysics Data System (ADS)

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

Russell, C. T.; Luhmann, Janet G.; Ma, Yingjuan; Zhang, Tielong; Villarreal, M.

177

Ablation of Venusian oxygen ions by unshocked solar wind  

NASA Astrophysics Data System (ADS)

Venus, without Earth-like magnetic dipole, has been seriously losing volatiles into the interplanetary space due to the force of solar wind and radiation. Solar wind is shocked near Venus, and then scavenges ionospheric particles in various ways. The oxygen ion (O+) loss rates estimated from spacecrafts' observations over decades are thought important for understanding the evolution of planetary habitability, considering the accumulation of escape over the history of solar system. However, all the previous observations were made in the shocked solar wind and/or inside the wake, though some simulations showed that unshocked solar wind can also ablate O+ ions. Here we report Venus Express observations of O+ ions in the unshocked solar wind during a solar minimum. These O+ ions are accelerated by the unshocked solar wind through pickup processes. The estimated O+ loss rates are comparable to those measured in the shocked solar wind and the wake. Our results suggest that the atmospheric loss at unmagnetized planets is significantly underestimated by previous observations, and thus the importance of Earth-like dipole for planetary habitability should be appreciated further.

Wei, Yong; Fraenz, Markus; Dubinin, Eduard; Wan, Weixing; Jarvinen, Riku; Zhang, Tielong; Barabash, Stas; Lundin, Rickard

2014-05-01

178

OBSERVATION OF FLUX-TUBE CROSSINGS IN THE SOLAR WIND  

SciTech Connect

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

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

2013-03-20

179

The Western Wind and Solar Integration Study Phase 2  

SciTech Connect

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

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

2013-09-01

180

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

181

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

182

Forms of Eulerian correlation functions in the solar wind  

E-print Network

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

A. Shalchi

2008-09-07

183

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

E-print Network

SOLAR WIND HELIUM ABUNDANCE AS A FUNCTION OF SPEED AND HELIOGRAPHIC LATITUDE: VARIATION THROUGH of the variation of the relative abundance of helium to hydrogen in the solar wind as a function of solar wind that for solar wind speeds between 350 and 415 km sÀ1 , AHe varies with a clear 6 month periodicity

Richardson, John

184

Mass loading of the solar wind by a sungrazing comet  

NASA Astrophysics Data System (ADS)

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

Rasca, A. P.; Oran, R.; Horányi, M.

2014-08-01

185

Solar wind and the motion of dust grains  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the action of solar wind on an arbitrarily shaped interplanetary dust particle. The final relativistically covariant equation of motion of the particle also contains the change of the particle's mass. The non-radial solar wind velocity vector is also included. The covariant equation of motion reduces to the Poynting-Robertson effect in the limiting case when a spherical particle is treated, when the speed of the incident solar wind corpuscles tends to the speed of light and when the corpuscles spread radially from the Sun. The results of quantum mechanics have to be incorporated into the physical considerations, in order to obtain the limiting case. If the solar wind affects the motion of a spherical interplanetary dust particle, then ?. Here, p'in and p'out are the incoming and outgoing radiation momenta (per unit time), respectively, measured in the proper frame of reference of the particle, and ? and ? are the solar wind pressure and the total scattering cross-sections, respectively. An analytical solution of the derived equation of motion yields a qualitative behaviour consistent with numerical calculations. This also holds if we consider a decrease of the particle's mass. Using numerical integration of the derived equation of motion, we confirm our analytical result that the non-radial solar wind (with a constant value of angle between the radial direction and the direction of the solar wind velocity) causes outspiralling of the dust particle from the Sun for large values of the particle's semimajor axis. The non-radial solar wind also increases the time the particle spirals towards the Sun. If we consider the periodical variability of the solar wind with the solar cycle, then there are resonances between the particle's orbital period and the period of the solar cycle.

Kla?ka, J.; Petržala, J.; Pástor, P.; Kómar, L.

2012-04-01

186

Tracking the Solar Wind Event to Its Source  

NSDL National Science Digital Library

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

2013-02-15

187

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

188

Polar solar wind and interstellar wind properties from interplanetary Lyman-alpha radiation measurements  

NASA Technical Reports Server (NTRS)

The analysis of Mariner 10 observations of Lyman-alpha resonance radiation shows an increase of interplanetary neutral hydrogen densities above the solar poles. This increase is caused by a latitudinal variation of the solar wind velocity and/or flux. Using both the Mariner 10 results and other solar wind observations, the values of the solar wind flux and velocity with latitude are determined for several cases of interest. The latitudinal variation of interplanetary hydrogen gas, arising from the solar wind latitudinal variation, is shown to be most pronounced in the inner solar system. From this result it is shown that spacecraft Lyman-alpha observations are more sensitive to the latitudinal anisotropy for a spacecraft location in the inner solar system near the downwind axis.

Witt, N.; Blum, P. W.; Ajello, J. M.

1981-01-01

189

First Results from the Genesis Autonomous Solar Wind Regime Algorithm  

NASA Astrophysics Data System (ADS)

Launched on August 8, 2001, the NASA Genesis mission will collect samples of the solar wind in various materials for approximately two years, and return those samples to Earth for analysis. A primary science goal of Genesis is the determination of the elemental and isotopic composition of the solar atmosphere from the solar wind material returned. Because the solar wind itself is known to exhibit compositional variations across different types of solar wind flows, Genesis will expose different collectors to solar wind originating from three flow types: coronal hole (CH), coronal mass ejection (CME) and interstream (IS) flows. Flow types are identified using in situ measurements of solar wind ions and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent array deployment on Genesis act autonomously, taking into account the proton speed, proton temperature, alpha particle abundance, and the presence of counter-streaming suprathermal electrons as determined onboard. Autonomous determination of counter-streaming electrons is novel, as is the simultaneous utilization of electron information and ion moments in logic that autonomously controls the science payload. We will report on the first four months of algorithm performance, comparing the onboard results to an assessment of regime based on post analysis of the in situ solar wind measurements. At the time of this writing, the regime algorithm has been active for eleven days, choosing regime IS for the first ten days, then transitioning to CH. In addition two interplanetary shocks have been correctly identified.

Steinberg, J. T.; Barraclough, B.; Bremmer, R. R.; Dors, E. E.; Gosling, J. T.; Neugebauer, M.; Skoug, R. M.; Tokar, R. L.; Wiens, R. C.

2001-12-01

190

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

E-print Network

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

Paris-Sud XI, Université de

191

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

192

Nearly Incompressible Modeling of the Solar Wind  

NASA Astrophysics Data System (ADS)

We develop a three-dimensional time dependent numerical model of compressible magnetohydrodynamic fluids describing super-Alfvénic, supersonic and strongly magnetized space and laboratory plasmas show a nonlinear relaxation towards a state of near incompressibility. The latter is characterized essentially by a subsonic turbulent Mach number. This transition is mediated dynamically by disparate spectral energy dissipation rates in compressible magnetosonic and shear Alfvénic modes. Nonlinear cascades lead to super-Alfvénic turbulent motions decaying to a sub- Alfvénic regime that couples weakly with (magneto)acoustic cascades. Consequently, the supersonic plasma motion is transformed into highly subsonic motion and density fluctuations experience a passive convection. This model provides a self-consistent explaination of the ubiquitous nature of incompressible magnetoplasma fluctuations in the solar wind and the interstellar medium.

Zank, G. P.; Shaikh, Dastgeer

2010-11-01

193

Genesis Solar Wind Array Collector Cataloging Status  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

194

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

195

Solar semidiurnal tidal wind oscillations above the CART site  

SciTech Connect

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

196

The Genesis Solar Wind Collection Mission: Current Status  

NASA Technical Reports Server (NTRS)

The NASA Genesis spacecraft was launched August 8, 2001 on a mission to collect samples of solar wind for greater than or equal to 2 years and then return them to Earth in 2004. Detailed analyses of the solar wind ions implanted into high-purity collection substrates will subsequently be carried out in earth-based laboratories using various mass spectrometry techniques. These analyses are expected to determine key isotopic ratios and elemental abundances in the solar wind and, by extension, in the solar photosphere. Further, the photospheric composition is thought to be representative of the solar nebula with a few exceptions so that the Genesis mission will provide a baseline for the average solar nebula composition with which to compare present-day compositions of planets, meteorites, and asteroids. The implications of the solar oxygen isotopic composition have been discussed. A list of other isotopic and elemental measurement objectives, and some of the rationale behind them, is given.

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

2003-01-01

197

Stationarity of extreme bursts in the solar wind.  

PubMed

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

Moloney, N R; Davidsen, J

2014-05-01

198

Residual Energy Spectrum of Solar Wind Turbulence  

E-print Network

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 years of Wind data at 1 AU to investigate the reason for this. The residual energy (difference between energy in velocity and magnetic field fluctuations) was calculated using both the standard magnetohydrodynamic (MHD) normalization for the magnetic field and a kinetic version, which includes temperature anisotropies and drifts between particle species. It was found that with the kinetic normalization, the fluctuations are closer to equipartition, with a mean normalized residual energy of sigma_r = -0.19 and mean Alfven 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 cros...

Chen, C H K; Salem, C S; Maruca, B A

2013-01-01

199

RESIDUAL ENERGY SPECTRUM OF SOLAR WIND TURBULENCE  

SciTech Connect

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

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

2013-06-20

200

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

201

Analysis of Wind Forces on Roof-Top Solar Panel  

NASA Astrophysics Data System (ADS)

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 panels. The present study is primarily focused on 2D and 3D modeling with steady, and turbulent flow over an inclined solar panel on the flat based roof to predict the wind forces for designing wind management system. For the numerical simulation, 3-D incompressible flow with the standard k-? was adopted and commercial CFD software ANSYS FLUENT was used. Results were then validated with wind tunnel experiments with a good agreement. Solar panels with various aspect ratios for various high wind speeds and angle of attacks were modeled and simulated in order to predict the wind loads in various scenarios. The present study concluded to reduce the strong wind uplift by designing a guide plate or a deflector before the panel.

Panta, Yogendra; Kudav, Ganesh

2011-03-01

202

Simulation of lunar carbon chemistry. I - Solar wind contribution  

NASA Technical Reports Server (NTRS)

Simulation experiments were conducted to identify the role of solar and lunar winds in the evolution of lunar carbon chemistry. Major conclusions are that (1) implantation of solar wind C, D, and N ions in silicates synthesizes small molecules that can be released into vacuum either by ion sputtering or by heating; (2) this synthesis is highly specific when compared to other processes accounting for the formation of molecules in the solar nebula or in interstellar space; (3) the carbon injected by the solar wind in the crystalline component of mature soils should reach a saturation concentration of about 200 ppm; and (4) the carbon chemistry of the crystalline component of mature soils is dominated by solar wind implantation effects.

Bibring, J. P.; Chaumont, J.; Langevin, Y.; Maurette, M.; Burlingame, A. L.; Wszolek, P. C.

1974-01-01

203

Quantifying shear-induced wave transformations in the solar wind  

E-print Network

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

Grigol Gogoberidze; Andria Rogava; Stefaan Poedts

2007-03-20

204

The solar wind interaction with unmagnetized planets - A tutorial  

NASA Technical Reports Server (NTRS)

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

Luhmann, J. G.

1990-01-01

205

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

206

Estimates of solar wind heating inside 0.3 AU  

NASA Technical Reports Server (NTRS)

Helios 1 proton temperature data have been normalized in order to determine a base temperature-velocity curve at 0.3 AU and to provide quantitative estimates on the close-in heating at different solar wind velocities. The results suggest that the slope of the solar wind temperature gradients for high-speed streams inside 0.3 AU is about half of that found beyond it. The very-low-speed wind is shown to expand adiabatically all the way out. It is also found that intermediate speed winds have enhanced heating rates in proportion to their velocities.

Freeman, John W.

1988-01-01

207

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

E-print Network

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

208

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

E-print Network

through a power electronic converter 3 #12;Wind and PV solar grid interface 4 Schematic of Type 3 windImpact of increased penetration of wind and PV solar resources on the bulk power system Vijay;Wind and PV solar grid interface · Modern wind turbine generators are typically rated between 1.5 MW

209

Solar wind plasma interaction with solar probe plus spacecraft  

NASA Astrophysics Data System (ADS)

3-D PIC (Particle In Cell) simulations of spacecraft-plasma interactions in the solar wind context of the Solar Probe Plus mission are presented. The SPIS software is used to simulate a simplified probe in the near-Sun environment (at a distance of 0.044 AU or 9.5 RS from the Sun surface). We begin this study with a cross comparison of SPIS with another PIC code, aiming at providing the static potential structure surrounding a spacecraft in a high photoelectron environment. This paper presents then a sensitivity study using generic SPIS capabilities, investigating the role of some physical phenomena and numerical models. It confirms that in the near- sun environment, the Solar Probe Plus spacecraft would rather be negatively charged, despite the high yield of photoemission. This negative potential is explained through the dense sheath of photoelectrons and secondary electrons both emitted with low energies (2-3 eV). Due to this low energy of emission, these particles are not ejected at an infinite distance of the spacecraft and would rather surround it. As involved densities of photoelectrons can reach 106 cm-3 (compared to ambient ions and electrons densities of about 7 × 103 cm-3), those populations affect the surrounding plasma potential generating potential barriers for low energy electrons, leading to high recollection. This charging could interfere with the low energy (up to a few tens of eV) plasma sensors and particle detectors, by biasing the particle distribution functions measured by the instruments. Moreover, if the spacecraft charges to large negative potentials, the problem will be more severe as low energy electrons will not be seen at all. The importance of the modelling requirements in terms of precise prediction of spacecraft potential is also discussed.

Guillemant, S.; Génot, V.; Matéo-Vélez, J.-C.; Ergun, R.; Louarn, P.

2012-07-01

210

Ionospheric mid-latitude response to solar wind discontinuities  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

211

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

E-print Network

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

Sanahuja, Blai

212

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

E-print Network

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

Li, Xinlin

213

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

E-print Network

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

214

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

E-print Network

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

Hudson, Hugh

215

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

E-print Network

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

216

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

217

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

E-print Network

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

Boyer, Edmond

218

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

Microsoft Academic Search

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

J. P. Reichling; F. A. Kulacki

2008-01-01

219

Prediction of geomagnetic storms from solar wind data using Elman recurrent neural networks  

Microsoft Academic Search

In order to accurately predict geomagnetic storms, we exploit Elman recurrent neural networks to predict the Dst index one hour in advance only from solar wind data. The input parameters are the interplanetary magnetic field z-component Bz (GSM), the solar wind plasma number density n and the solar wind velocity V. The solar wind data and the geomagnetic index Dst

Jian-Guo Wu; Henrik Lundstedt

1996-01-01

220

Interpretation of 3He variations in the solar wind  

NASA Technical Reports Server (NTRS)

The ion composition instrument (ICI) on ISEE-3 observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km/s. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of 3He flares occurred during this time.

Coplan, M. A.; Ogilvie, K. W.; Geiss, J.; Bochsler, P.

1983-01-01

221

Interpretation of He-3 abundance variations in the solar wind  

NASA Technical Reports Server (NTRS)

The ion composition instrument (ICI) on ISEE-3 observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km/s. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of He-3 flares occurred during this time.

Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.

1984-01-01

222

Identifying solar wind structures related to Garuda 1 satellite anomaly by analyzing solar wind and IMF parameters  

NASA Astrophysics Data System (ADS)

Understanding solar wind structures associated with anomalies experienced by a satellite can be useful in the prediction of satellite anomalies. This study uses solar wind and interplanetary magnetic field (IMF) parameters to identify the type of solar wind disturbances associated with the reported anomaly experienced by Garuda 1 satellite on April 5, 2005. By superposed epoch analysis we conclude that the corotating interaction region (CIR) with a stream interface at 6:30 UT of 4 April 2005 was associated with the anomaly. This CIR produced a moderate intensity magnetic storm with Dst = -90 nT.

Rachman, Abdul; Herdiwijaya, Dhani

2014-03-01

223

Erosion of carbon/carbon by solar wind charged particle radiation during a solar probe mission  

NASA Technical Reports Server (NTRS)

The possible erosion of a carbon/carbon thermal shield by solar wind-charged particle radiation is reviewed. The present knowledge of erosion data for carbon and/or graphite is surveyed, and an explanation of erosion mechanisms under different charged particle environments is discussed. The highest erosion is expected at four solar radii. Erosion rates are analytically estimated under several conservative assumptions for a normal quiet and worst case solar wind storm conditions. Mass loss analyses and comparison studies surprisingly indicate that the predicted erosion rate by solar wind could be greater than by nominal free sublimation during solar wind storm conditions at four solar radii. The predicted overall mass loss of a carbon/carbon shield material during the critical four solar radii flyby can still meet the mass loss mission requirement of less than 0.0025 g/sec.

Sokolowski, Witold; O'Donnell, Tim; Millard, Jerry

1991-01-01

224

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

NASA Astrophysics Data System (ADS)

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

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

225

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2011-11-29

226

Solar wind flow upstream of the coronal slow shock  

NASA Technical Reports Server (NTRS)

Slow shocks have been predicted to exist embedded in large coronal holes at low altitude. Two or more curved slow shocks may link together to form a composite discontinuity surface around the sun which may be called the coronal slow shock (CSS). Here a solar-wind model is studied under the assumption that a standing CSS exists and cororates with the sun at a constant angular velocity. A steady, axisymmetrical one-fluid model is introduced to study the expansion of solar wind in the open-field region upstream of the CSS. The model requires that the conditions downstream of the CSS near the equatorial plane can produce a solar wind agreeable with the observations made near the earth's orbit. The paper presents an illustrative calculation in which the polar caps within 60 deg of the polar angle are assumed to be the source region of the solar wind.

Whang, Y. C.

1986-01-01

227

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

NASA Astrophysics Data System (ADS)

We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were very clearly resolved. One observation showed clear evidence of two discrete modes of fast solar wind, which we interpret as originating in the crown of the northern polar coronal hole and in an equatorward extension of the polar hole. We suggest that experiments of this type will provide a new and important source of information on the temporal and spatial variation of small-scale turbulence in the solar wind. The improved velocity resolution available from extremely long baseline measurements also provides new information on the development of the large-scale velocity structure of the solar wind in interplanetary space.

Breen, A. R.; Fallows, R. A.; Bisi, M. M.; Thomasson, P.; Jordan, C. A.; Wannberg, G.; Jones, R. A.

2006-08-01

228

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

229

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

SciTech Connect

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

Not Available

2013-09-01

230

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

SciTech Connect

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

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

2013-09-01

231

Charge exchange in solar wind-cometary interactions  

NASA Technical Reports Server (NTRS)

A simple model of a cometary spherically symmetrical atmosphere and ionosphere is considered. An analytic solution of the governing equations describing the radial distribution of the neutral and ion densities is found. The new solution is compared to the well-known solution of the equations containing only ionization terms. Neglecting recombination causes a significant overestimate of the ion density in the vicinity of the comet. An axisymmetric model of the solar wind-cometary interaction is considered, taking into account the loss of solar wind ions due to charge exchange. The calculations predict that for active comets, solar wind absorption due to charge exchange becomes important at a few thousand kilometers from the nucleus, and a surface separating the shocked solar wind from the cometary ionosphere develops in this region. These calculations are in reasonable agreement with the few observations available for the ionopause location at comets.

Gombosi, T. I.; Horanyi, M.; Kecskemety, K.; Cravens, T. E.; Nagy, A. F.

1983-01-01

232

Solar wind propagation from Ulysses to Voyager 2  

NASA Astrophysics Data System (ADS)

Ulysses near 5 AU and Voyager 2 near 80 AU were at the same heliolatitude in mid-2005. This alignment provides an opportunity to study the propagation of the solar wind through the heliosphere. Voyager 2 saw a large shock at roughly the time the solar wind from the alignment time was expected to arrive at Voyager 2 from Ulysses. We model two possible sources of this shock, fast streams from polar coronal holes and coronal mass ejections (CMEs), and obtain a reasonable match to the V2 data by combining these sources. We also investigate the slowdown of the solar wind due to pickup ions over this distance. The modeling of the shock allows us to remove the period when transient plasma from CMEs is important and determine that the solar wind speed decreases about 70 km/s due to pickup ions, consistent with a interstellar hydrogen density at the termination shock of about 0.09/cc.

Richardson, J.; Ying, L.; Wang, C.; McComas, D.

2006-12-01

233

Genesis Solar Wind Array Collector Fragments Post-Recovery Status  

NASA Astrophysics Data System (ADS)

The Genesis solar wind sample return mission spacecraft was launched with 271 whole and 30 half hexagonally-shaped collectors. At 65 cm2 per hexagon, the total collection area was 18,600 cm2. These 301 collectors were comprised of 9 materials mounted on 5 arrays, each of which was exposed to a specific regime of the solar wind. Thoughtfully, collectors exposed to a specific regime were made of a unique thickness: bulk solar wind (700 ?m thick), transient solar wind associated with coronal mass ejection (650 ?m), high speed solar wind from coronal holes (600 ?m), and interstream low-speed solar wind (550 ?m). Thus, it is easy to distinguish the solar wind regime sampled by measuring the fragment thickness. Nearly 10,000 fragments have been enumerated, constituting about 20% of the total area. The sapphire-based hexagons survived better than the silicon hexagons as seen in the percent pre-flight whole collectors compared to the percent of recovered fragments in 10 to 25 mm size range. Silicon-based collectors accounted for 57% of the hexagons flown but 18% of the recovered fragments. However, a) gold coating on sapphire accounted for 12% flown and 27% of the recovered; b) aluminum coating on sapphire for 9% flown and 25% of the recovered; c) silicon coating on sapphire for 7% flown and 18% of the recovered; and d) sapphire for 7% flown and 10% of the recovered. Due to the design of the array frames, many of the recovered fragments were trapped in baffles very near their original location and were relatively protected from outside debris. Collector fragments are coated with particulate debris, and there is evidence that a thin molecular film was deposited on collector surfaces during flight. Therefore, in addition to allocations distributed for solar wind science analysis, poorer quality samples have been used in specimen cleaning tests.

Allton, J. H.

2005-12-01

234

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

235

Solar Wind and Magnetosphere Interaction Lab: A Cereal Analogy  

NSDL National Science Digital Library

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

236

Heating of the interstellar medium by the solar wind  

NASA Technical Reports Server (NTRS)

The heating of inflowing interstellar gas by the solar wind is calculated. The experimental differential cross sections have been used for calculating electron-H(He) and proton-H(He) elastic scattering rate coefficients. The solar wind is assumed to be a two-component (protons and electrons), steady, spherically symmetric stream moving radially outward, with the inflowing gas following Keplerian trajectories. The spatial distributions of effective temperature increase within interplanetary space have been obtained.

Kunc, J. A.; Wu, F. M.; Judge, D. L.

1983-01-01

237

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

NASA Technical Reports Server (NTRS)

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

Burlaga, L. F.; Barouch, E.

1974-01-01

238

Wind loading on solar concentrators: Some general considerations  

NASA Astrophysics Data System (ADS)

A survey was 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.

Roschke, E. J.

1984-05-01

239

Wind loading on solar concentrators: Some general considerations  

NASA Technical Reports Server (NTRS)

A survey was 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.

Roschke, E. J.

1984-01-01

240

Dissipation of Turbulence in the Solar Wind  

NASA Technical Reports Server (NTRS)

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

Goldstein, Melvyn L.

2010-01-01

241

Interaction of Comets and the Solar Wind  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

242

Interaction of Comets and the Solar Wind  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

243

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

NASA Technical Reports Server (NTRS)

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

Farrell, William M.

2011-01-01

244

Origins of the slow and the ubiquitous fast solar wind  

E-print Network

We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5 Rs, obtained during the Galileo solar conjunction in January 1997, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered componentof the oxygen 1032 A and 1037 A lines as measured with the UltraViolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the Large Angle Spectroscopic Coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context ofcoronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo and Martin (1997) that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind...

Habbal, S R; Fineschi, S; O'Neal, R; Kohl, J M; Noci, G; Korendyke, C

1997-01-01

245

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

246

Sputtering by the Solar Wind: Effects of Variable Composition  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

247

Western Wind and Solar Integration Study Phase 2: Preprint  

SciTech Connect

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

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

2012-09-01

248

Determining the LIC H density from the solar wind slowdown  

NASA Astrophysics Data System (ADS)

Context: The ionized solar wind interacts directly with the interstellar neutrals which flow into the heliosphere. These neutrals are ionized, mainly by charge exchange, then accelerated to the solar wind speed with the momentum and energy removed from the bulk flow of the solar wind. Thus, by measuring the solar wind slowdown, one can estimate the interstellar neutral density. Aims: In July 2005, Ulysses at 5 AU and Voyager 2 near 80 AU were at the same heliolatitude. We use this alignment to determine the solar wind speed decrease between these two spacecraft. Methods: Ulysses data are used as input to a 1-D MHD model which includes the effects of pickup ions. We removed a section of data contaminated by an ICME directed toward Voyager 2. Results: Comparison of the Voyager 2 speeds with the model results shows that the solar wind speed decreased by 67 km s-1 between Ulysses and Voyager 2, consistent with an interstellar neutral density at the termination shock of 0.09 cm-3.

Richardson, J. D.; Liu, Y.; Wang, C.; McComas, D. J.

2008-11-01

249

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

250

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

251

Using the fingerprints of solar magnetic reconnection to identify the elemental building blocks of the slow solar wind  

NASA Astrophysics Data System (ADS)

While the source of the fast solar wind is well understood to be linked to coronal holes, the source of the slow solar wind has remained elusive. Many previous studies of the slow solar wind have examined trends in the composition and charge states over long time scales and found strong relationships between the solar wind velocity and these plasma parameters. These relationships have been used to constrain models of solar wind source and acceleration. In this study, we take advantage of high time resolution (12 min) measurements of solar wind composition and charge-state abundances recently reprocessed by the ACE Solar Wind Ion Composition Spectrometer (SWICS) science team to probe the timescales of solar wind variability at relatively small scales. We study an interval of slow solar wind containing quasi-periodic 90 minute structures and show that they are remnants of solar magnetic reconnection. Each 90-minute parcel of slow solar wind, though the speed remains steady, exhibits the complete range of charge state and composition variations expected for the entire range of slow solar wind, which is repeated again in the next 90-minute interval. These observations show that previous statistical results break down on these shorter timescales, and impose new and important constraints on models of slow solar wind creation. We conclude by suggesting these structures were created through interchange magnetic reconnection and form elemental building blocks of the slow solar wind. We also discuss the necessity of decoupling separately the process(es) responsible for the release and acceleration.

Kepko, Larry; Viall, Nicholeen M.; Kasper, Justin; Lepri, Sue

2015-04-01

252

Electron energy transport in the solar wind: Ulysses observations  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

253

Solar wind eddies and the heliospheric current sheet  

NASA Technical Reports Server (NTRS)

Ulysses has collected data between 1 and 5 AU during, and just following solar maximum, when the heliospheric current sheet (HCS) can be thought of as reaching its maximum tilt and being subject to the maximum amount of turbulence in the solar wind. The Ulysses solar wind plasma instrument measures the vector velocity and can be used to estimate the flow speed and direction in turbulent 'eddies' in the solar wind that are a fraction of an astronomical unit in size and last (have either a turnover or dynamical interaction time of) several hours to more than a day. Here, in a simple exercise, these solar wind eddies at the HCS are characterized using Ulysses data. This character is then used to define a model flow field with eddies that is imposed on an ideal HCS to estimate how the HCS will be deformed by the flow. This model inherently results in the complexity of the HCS increasing with heliocentric distance, but the result is a measure of the degree to which the observed change in complexity is a measure of the importance of solar wind flows in deforming the HCS. By comparison with randomly selected intervals not located on the HCS, it appears that eddies on the HCS are similar to those elsewhere at this time during the solar cycle, as is the resultant deformation of the interplanetary magnetic field (IMF). The IMF deformation is analogous to what is often termed the 'random walk' of interplanetary magnetic field lines.

Suess, S. T.; Mccomas, D. J.; Bame, S. J.; Goldstein, B. E.

1995-01-01

254

On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values  

NASA Technical Reports Server (NTRS)

The aa index can be decomposed into two separate components: the leading sporadic component due to solar activity as measured by sunspot number and the residual or recurrent component due to interplanetary disturbances, such as coronal holes. For the interval 1964-2006, a highly statistically important correlation (r = 0.749) is found between annual averages of the aa index and the solar wind speed (especially between the residual component of aa and the solar wind speed, r = 0.865). Because cyclic averages of aa (and the residual component) have trended upward during cycles 11-23, cyclic averages of solar wind speed are inferred to have also trended upward.

Wilson, Robert M.; Hathaway, David H.

2008-01-01

255

Validation of a synoptic solar wind model  

Microsoft Academic Search

We present a validation of a three-dimensional magnetohydrodynamic model for the solar corona and the inner heliosphere. We compare the results of the model with long-term satellite data at 1 AU for a 1 year period during solar minimum and another year period of solar maximum. Overall, the model predicts rather well the magnitude of the magnetohydrodynamical variables for solar

O. Cohen; I. V. Sokolov; I. I. Roussev; T. I. Gombosi

2008-01-01

256

Solar wind flow past nonmagnetic planets-Venus and Mars  

Microsoft Academic Search

The hydromagnetic theory of solar wind flow past the Earth has been extended and modified so as to be applicable to nonmagnetic planets, such as Venus and Mars, that have a sufficient ionosphere to deflect the solar plasma around the planet and its atmosphere. The principal difference in the analysis stems from the fact that the current sheath that bounds

John R. Spreiter; Audrey L. Summers; Arthur W. Rizzi

1970-01-01

257

Livestock Water Pumping with Wind and Solar Power  

Microsoft Academic Search

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

R. Nolan Clark; Brian D. Vick

258

Element Abundances in the Sun and Solar Wind Along the Solar Cycle  

NASA Astrophysics Data System (ADS)

Element abundances are a critical parameter in almost every aspect of solar physics, from regulating the energy flow and the structure of the solar interior, to shaping the energy losses of the solar atmosphere, ruling the radiative output of the UV, EUV and X-rays solar radiation which impacts the Earth's upper atmosphere, and determining the composition of the solar wind.In this work we study the evolution of the element abundances in the solar corona and in the solar wind from 1996 to date using data from SoHO, Hinode, Ulysses and ACE satellites, in order to determine their variability along the solar cycle, and the relationship between solar abundance variations in the solar wind and in its source regions in the solar atmosphere. We study all the most abundant elements, with a special emphasis on Ne and O. We discuss our results in light of the source region of the solar wind, and of the radiative output of the solar corona.

Landi, Enrico

2015-04-01

259

Plasma Properties of Pseudostreamers and Their Solar Wind Streams  

NASA Astrophysics Data System (ADS)

We study pseudostreamers (i.e., open-field extensions of plasma from unipolar footpoints in the corona; distinct from classical helmet streamers that have opposite-polarity footpoints) that are believed to be sources of slow to intermediate speed wind streams. We make use of multi-spacecraft and ground-based observations that extend from the solar corona to the solar wind at 1 AU. We compare the physical properties of selected pseudostreamers and helmet streamers to characterize how the differences in magnetic topology affect the plasma properties of the coronal structures and their wind.

Paz Miralles, Mari; Allen, Lorraine A.

2015-04-01

260

Solar Wind Stream Interaction Regions without Sector Boundaries  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

261

Acceleration of weakly collisional solar-type winds  

E-print Network

One of the basic properties of the solar wind, that is the high speed of the fast wind, is still not satisfactorily explained. This is mainly due to the theoretical difficulty of treating weakly collisional plasmas. The fluid approach implies that the medium is collision dominated and that the particle velocity distributions are close to Maxwellians. However the electron velocity distributions observed in the solar wind depart significantly from Maxwellians. Recent kinetic collisionless models (called exospheric) using velocity distributions with a suprathermal tail have been able to reproduce the high speeds of the fast solar wind. In this letter we present new developments of these models by generalizing them over a large range of corona conditions. We also present new results obtained by numerical simulations that include collisions. Both approaches calculate the heat flux self-consistently without any assumption on the energy transport. We show that both approaches - the exospheric and the collisional one - yield a similar variation of the wind speed with the basic parameters of the problem; both produce a fast wind speed if the coronal electron distribution has a suprathermal tail. This suggests that exospheric models contain the necessary ingredients for the powering of a transonic stellar wind, including the fast solar one.

I. Zouganelis; N. Meyer-Vernet; S. Landi; M. Maksimovic; F. Pantellini

2005-05-16

262

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

263

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

264

Solar Wind Heavy Ions over Solar Cycle 23: ACE/SWICS Measurements  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

265

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

SciTech Connect

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

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

2013-05-01

266

Solar wind interaction with Venus and impact on its atmosphere  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

267

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

E-print Network

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

Richardson, John

268

Sources of Solar Wind at Solar Minimum: Constraints from Composition Data  

NASA Astrophysics Data System (ADS)

In this discussion of observational constraints on the source regions and acceleration processes of solar wind, we will focus on the ionic composition of the solar wind and the distribution of charge states of heavy elements such as oxygen and iron. We first focus on the now well-known bi-modal nature of solar wind, which dominates the heliosphere at solar minimum: Compositionally cool solar wind from polar coronal holes over-expands, filling a much larger solid angle than the coronal holes on the Sun. We use a series of remote and in-situ characteristics to derive a global geometric expansion factor of ˜5. Slower, streamer-associated wind is located near the heliospheric current sheet with a width of 10-20°, but in a well-defined band with a geometrically small transition width. We then compute charge states under the assumption of thermal electron distributions and temperature, velocity, and density profiles predicted by a recent solar wind model, and conclude that the solar wind originates from a hot source at around 1 million K, characteristic of the closed corona.

Zurbuchen, Thomas H.; von Steiger, Rudolf; Gruesbeck, Jacob; Landi, Enrico; Lepri, Susan T.; Zhao, Liang; Hansteen, Viggo

2012-11-01

269

Ions with low charges in the solar wind as measured by SWICS on board Ulysses. [Solar Wind Ion Composition Spectrometer  

NASA Technical Reports Server (NTRS)

We present new data on rare ions in the solar wind. Using the Ulysses-SWICS instrument with its very low background we have searched for low-charge ions during a 6-d period of low-speed solar wind and established sensitive upper limits for many species. In the solar wind, we found He(1+)/He(2+) of less than 5 x 10 exp -4. This result and the charge state distributions of heavier elements indicate that all components of the investigated ion population went through a regular coronal expansion and experienced the typical electron temperatures of 1 to 2 million Kelvin. We argue that the virtual absence of low-charge ions demonstrates a very low level of nonsolar contamination in the source region of the solar wind sample we studied. Since this sample showed the FlP effect typical for low-speed solar wind, i.e., an enhancement in the abundances of elements with low first ionization potential, we conclude that this enhancement was caused by an ion-atom separation mechanism operating near the solar surface and not by foreign material in the corona.

Geiss, J.; Ogilvie, K. W.; Von Steiger, R.; Mall, U.; Gloeckler, G.; Galvin, A. B.; Ipavich, F.; Wilken, B.; Gliem, F.

1992-01-01

270

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

E-print Network

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

Richardson, John

271

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

E-print Network

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

Johnson, Robert E.

272

Correlation of solar wind entropy and oxygen ion charge state ratio  

Microsoft Academic Search

Both proton specific entropy and solar wind composition have been recognized in the past as markers of boundaries between what was originally slow and fast solar wind during the declining phase of the solar cycle, when the solar wind alternates between the two regimes. During the rising phase, when boundaries between regimes are not apparent, ACE SWICS and SWEPAM data

A. C. Pagel; N. U. Crooker; T. H. Zurbuchen; J. T. Gosling

2004-01-01

273

Slow solar wind boundaries and implication for its formation  

NASA Astrophysics Data System (ADS)

Solar wind and the associated magnetic field permeate the heliosphere. Their temporal and spatial variations contribute significantly in the large range of variations in related geomagnetic effects as well as in the properties of solar energetic particles. Among the least understood is the slow solar wind for how it is formed at the Sun and what causes the large variations in its physical properties. This work investigates the variations in the slow solar wind streams measured in-situ at 1 AU and the correlations among the protons, heavy ions, suprathermal electrons, and magnetic field properties. Besides well-established correlations among the proton speed, proton temperature and ion charge states, we also found certain distinct characteristics in the correlation and temporal relationship between the ion charge states, proton velocity fluctuations and, in many cases, suprathermal electron halos. The implications from our findings in the slow wind formation and whether the slow wind has a distinct boundary with the fast wind will be discussed.

Ko, Yuan-Kuen; Roberts, Aaron; Lepri, Susan; Kocher, Manan

2015-04-01

274

Chromospheric alfvenic waves strong enough to power the solar wind.  

PubMed

Alfvén waves have been invoked as a possible mechanism for the heating of the Sun's outer atmosphere, or corona, to millions of degrees and for the acceleration of the solar wind to hundreds of kilometers per second. However, Alfvén waves of sufficient strength have not been unambiguously observed in the solar atmosphere. We used images of high temporal and spatial resolution obtained with the Solar Optical Telescope onboard the Japanese Hinode satellite to reveal that the chromosphere, the region sandwiched between the solar surface and the corona, is permeated by Alfvén waves with strong amplitudes on the order of 10 to 25 kilometers per second and periods of 100 to 500 seconds. Estimates of the energy flux carried by these waves and comparisons with advanced radiative magnetohydrodynamic simulations indicate that such Alfvén waves are energetic enough to accelerate the solar wind and possibly to heat the quiet corona. PMID:18063784

De Pontieu, B; McIntosh, S W; Carlsson, M; Hansteen, V H; Tarbell, T D; Schrijver, C J; Title, A M; Shine, R A; Tsuneta, S; Katsukawa, Y; Ichimoto, K; Suematsu, Y; Shimizu, T; Nagata, S

2007-12-01

275

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

E-print Network

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

276

Direct evidence for kinetic effects associated with solar wind reconnection  

PubMed Central

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

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

2015-01-01

277

Direct evidence for kinetic effects associated with solar wind reconnection.  

PubMed

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

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

2015-01-01

278

COLLISIONLESS DAMPING AT ELECTRON SCALES IN SOLAR WIND TURBULENCE  

SciTech Connect

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

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

2013-09-10

279

Magnetic field gradients in solar wind plasma and geophysics periods  

E-print Network

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

A. Bershadskii

2006-11-16

280

Fast solar wind monitoring available: BMSW in operation  

NASA Astrophysics Data System (ADS)

The Spektr-R spacecraft was launched on a Zenit-3F rocket into an orbit with a perigee of 10.000 kilometers and apogee of 390.000 km on July 18, 2011. The spacecraft operational lifetime would exceed five years. The main task of the mission is investigations of distant sources of electromagnetic emissions but, as a supporting measurement, the spacecraft carries a complex of instruments for solar wind monitoring because it will spend there ˜ 8 days out of the 9-day orbit. The main task of the solar wind monitor (BMSW) is to provide fast measurements of the solar wind density, velocity, and temperature with a maximum time resolution of 31 ms. Such time resolution was obtained using simultaneous measurements of several Faraday cups oriented permanently nearly in the solar wind direction. In this paper, we describe briefly basic principles of the BMSWoperation, and show a few examples its observations. We present frequency spectra of the solar wind turbulence at the kinetic scale and an example of high-frequency waves associated with an IP shock.

Šafránková, J.; N?me?ek, Z.; P?ech, L.; Zastenker, G.

2013-06-01

281

Fast solar wind monitoring available: BMSW in operation  

NASA Astrophysics Data System (ADS)

The Spektr-R spacecraft was launched on a Zenit-3F rocket into an orbit with a perigee of 10.000 kilometers and apogee of 390.000 km on July 18, 2011. The spacecraft operational lifetime would exceed five years. The main task of the mission is investigations of distant sources of electromagnetic emissions but, as a supporting measurement, the spacecraft carries a complex of instruments for solar wind monitoring because it will spend there ~ 8 days out of the 9-day orbit. The main task of the solar wind monitor (BMSW) is to provide fast measurements of the solar wind density, velocity, and temperature with a maximum time resolution of 31 ms. Such time resolution was obtained using simultaneous measurements of several Faraday cups oriented permanently nearly in the solar wind direction. In this paper, we describe briefly basic principles of the BMSWoperation, and show a few examples its observations. We present frequency spectra of the solar wind turbulence at the kinetic scale and an example of high-frequency waves associated with an IP shock.

Šafránková, J.; N?me?ek, Z.; P?ech, L.; Zastenker, G.

2013-06-01

282

The relationship between Jovian electrons and solar wind stream structure  

NASA Technical Reports Server (NTRS)

Near-earth observations of above-0.22-MeV Jovian electrons by the APL/JHU experiments on IMP-7 and 8 during 1972-1975, a period of stable recurrent solar wind, reveals 19 of 26 events in good association with solar wind streams. This pattern of positive correlation with solar wind streams is also observed in 3-6 MeV data from 1965-1972 during well-defined electron events. During their pre-encounter periods Pioneers 10 and 11 were nearly radially aligned with Jupiter and direct magnetic connection was highly unlikely. Jovian electrons above about 5 MeV in the UCSD experiments on Pioneers 10 and 11 were anticorrelated with solar wind velocity from about 3-4 AU until encounter. Reconstructions of the large-scale interplanetary magnetic field suggest that the near-earth events result from direct connection with the Jovian magnetotail and corotation of quasi-trapped populations while for Pioneer events electrons propagate out from the magnetosphere to a solar wind stream interaction, in along the interaction, then in to Pioneer on undisturbed field lines.

Gold, R. E.; Krimigis, S. M.; Roelof, E. C.; Fillius, R. W.

1978-01-01

283

The abundances of elements and isotopes in the solar wind  

NASA Technical Reports Server (NTRS)

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

Gloeckler, George; Geiss, Johannes

1989-01-01

284

Direct evidence for kinetic effects associated with solar wind reconnection  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

285

Parametric decay of Alfvén wave in the solar wind acceleration  

NASA Astrophysics Data System (ADS)

Large amplitude Alfvén waves are commonly observed in the solar wind and it is widely believed that these magnetic waves may contribute to the solar wind heating and acceleration through turbulent dissipation and ponderomotive force. In-situ observations show that a nonlinear cascade of Alfvén waves, mainly propagating outward, is taking place, and that it evolves with heliocentric distance. In spite of the well defined observational signatures, the evolution of such Alfvénic turbulence in the solar wind is still a matter under debate. Parametric decay of large amplitude Alfvén waves has been invoked as a possible driver of such evolution: the decay of an outward Alfvén wave into an inward one and, on the other hand, into a sound wave which naturally tends to steepen, provides the key ingredients for the onset of a turbulent cascade as well as for energy dissipation. In spite of many theoretical and numerical studies on the parametric decay instability, possible effects of the solar wind radial expansion have not yet been taken into account. However, the expansion of the underlying solar atmosphere is an indiscernible element to the extent that the observed decrease in overall rms energies is well accounted for by expansion effects. We provide here a study on the onset and evolution of the parametric decay within the Accelerating Expanding Box model. This model takes into account the effects of the accelerating radial expansion of the solar wind, including the crossing of the critical Alfvén point, where wave amplitudes are expected to peak. The aim is to inspect if and in which manner the non-uniform radial expansion of the solar wind affects the growth and evolution of the instability itself and in which way it may affect the alfvénic spectrum at large heliocentric distances.

Tenerani, Anna; Velli, Marco

2014-05-01

286

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

SciTech Connect

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

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

2012-08-01

287

Origins of the slow and the ubiquitous fast solar wind  

E-print Network

We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5 Rs, obtained during the Galileo solar conjunction in January 1997, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered componentof the oxygen 1032 A and 1037 A lines as measured with the UltraViolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the Large Angle Spectroscopic Coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context ofcoronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo and Martin (1997) that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona, and that a velocity shear between the fast and slow solar wind develops along the streamer stalks.

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

1997-09-03

288

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

289

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

290

Solar wind flow past Venus - Theory and comparisons  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

291

The Interplanetary Magnetic Field and Solar Wind Driven Magnetospheric Reconfiguration  

E-print Network

The magnetic disturbances are associated with electric currents as it is well checked at laboratory room scales and described by the Maxwell's equations of electromagnetic field. The analysis of spacecraft observations for more than a quarter of a century failed to provide a self-consistent three-dimensional picture of the solar wind-magnetosphere dynamo generated magnetospheric and ionospheric current systems. The proposed solar wind and the interplanetary magnetic field (IMF) driven reconfiguration of the earth's magnetosphere directly accounts for the observed magnetic disturbances. So role of the magnetospheric currents in creation of the magnetic disturbances is reconsidered in accordance with some poorly understood observations. A quantitative agreement with observations is demonstrated and a laboratory experiment to test the suggested model of the solar wind/IMF-magnetosphere interaction is described.

Eugene Savov

2003-01-02

292

Lunar fossil magnetism and perturbations of the solar wind.  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

293

Solar wind and stellar jets, from newtonian to relativistic ones  

NASA Astrophysics Data System (ADS)

In parallel to the development of numerical simulations, analytical solutions for modelling the acceleration and the collimation of winds and jets have been proposed. We present here how meridionally self-similar solutions can be used to model the solar wind using Ulysses data at solar minimum. Such solutions may also be adapted to explain the formation core or spine jets in classical and weak TTauri stars (class II and III young stellar jets) as well as relativistic jet cores from AGN. The criterion for collimation explains how the jet evolves towards a wind as the star approaches the main sequence. A similar scenario could explain the winds from Seyfert galaxies by opposition to the powerful jets from Fanaroff Riley sources.

Sauty, C.; Lima, J. J. G.; Tsinganos, K.; Aibeo, A.; Meliani, Z.; Vlahakis, N.

2007-03-01

294

Agua Caliente Wind/Solar Project at Whitewater Ranch  

SciTech Connect

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

Hooks, Todd; Stewart, Royce

2014-12-16

295

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations  

Microsoft Academic Search

Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with \\

B. Lavraud; A. Opitz; J. T. Gosling; A. P. Rouillard; K. Meziane; J.-A. Sauvaud; A. Fedorov; I. Dandouras; V. Génot; C. Jacquey; P. Louarn; C. Mazelle; E. Penou; D. E. Larson; J. G. Luhmann; P. Schroeder; Lan K. Jian; C. T. Russell; C. Foullon; R. M. Skoug; J. T. Steinberg; K. D. Simunac; A. B. Galvin

2010-01-01

296

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

E-print Network

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

Takeru K. Suzuki; Shu-ichiro Inutsuka

2006-05-22

297

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

298

Multi-parametric classification of the solar wind origins  

NASA Astrophysics Data System (ADS)

There are many types of the solar wind sources. They differ in physics and geometry. Our classification is based on dimensionless scaling parameters. Plasma kinetic and MHD regimes define microscopic and macroscopic sources with large and small Knudsen numbers correspondingly. We consider here only macroscopic sources. One-connected solar wind source surfaces represent the most known type in coronal holes. Their geometry and topology is poorly investigated. There are steady state and transient types of the solar wind and corresponding sources with a finite life time according to the Strouhal parameter. The material and energy reservoirs needed for the plasma outflow from the Sun can be stored at different altitudes and in different places in the atmosphere from the photosphere up to the outer corona not higher than several solar radii according to observations. The role of gravity forces diminishes with altitude and regulated by the Froude numbers in streamers and pseudo-streamers. Plasma down-flows were never observed at distances larger than about 6 solar radii. Plasma density, velocity, temperature, ion composition, magnetic and electric fields are combined in many tens of physically different and similar types of origins, which are partially known and to be discovered in future. Thermally driven or magnetically driven winds are well known and delimited by the plasma parameter beta, but we do not know as yet what type is dominating on the Sun as a star globally. This parameter generally around ~ 1, typically being <1 in coronal holes and >1 in active regions from case to case. Laminar and turbulent sources are characterized by corresponding Reynolds numbers. We point out the necessity of the electric field measurements in the corona for better understanding of the solar wind origins of inductive and potential types according to dimensionless Faraday number. Trieste numbers are needed to characterize mostly open, closed or intermittent situations in the sources. We discuss also the astrophysical question about the solar type stars in the stage of unstable accretion.

Igor, Veselovskiy

299

Mass fractionation of the lunar surface by solar wind sputtering  

NASA Technical Reports Server (NTRS)

An investigation is conducted concerning the mass-fractionation effects produced in connection with the bombardment of the moon by the solar wind. Most of the material ejected by sputtering escapes the moon's gravity, but some returning matter settles back onto the lunar surface. This material, which is somewhat richer in heavier atoms than the starting surface, is incorporated into the heavily radiation-damaged outer surfaces of grains. The investigation indicates that sputtering of the lunar surface by the solar wind will give rise to significant surface heavy atom enrichments if the grain surfaces are allowed to come into sputtering equilibrium.

Switkowski, Z. E.; Haff, P. K.; Tombrello, T. A.; Burnett, D. S.

1977-01-01

300

Solar wind kinetic instabilities at small plasma betas  

SciTech Connect

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

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

2014-02-15

301

Interaction effects between solar wind and comet Bennett  

NASA Technical Reports Server (NTRS)

Observations of the solar wind and the comet Bennett made during the period from Mar. 23 to Apr. 5, 1970 are considered. During this period the position of the comet had been comparatively close to earth at a distance of about 0.7 AU. Plasma data from four space probes and photographs of a number of observatories are taken into account. The relation between a sudden change in the velocity of the solar wind and the occurrence of a pronounced disturbance in the cometary tail is investigated.

Burlaga, L. F.; Donn, B. D.; Rahe, J.; Neugebauer, M.

1973-01-01

302

Measurement of Damage Profiles from Solar Wind Implantation  

NASA Technical Reports Server (NTRS)

NASA's Genesis Mission launched from Cape Canaveral in August of 2001 with the goal of collecting solar wind in ultra-pure materials. The samples were returned to Earth more than three years later for subsequent analysis. Although the solar wind is comprised primarily of protons, it also contains ionized species representing the entire periodic table. The Genesis mission took advantage of the natural momentum of these ionized species to implant themselves in specialized collectors including single crystal Si and SiC. The collectors trapped the solar wind species of interest and sustained significant damage to the surface crystal structure as a result of the ion bombardment. In this work, spectroscopic ellipsometry has been used to evaluate the extent of this damage in Si and SiC samples. These results and models are compared for artificially implanted samples and pristine non-flight material. In addition, the flown samples had accumulated a thin film of molecular contamination as a result of outgassing in flight, and we demonstrate that this layer can be differentiated from the material damage. In addition to collecting bulk solar wind samples (continuous exposure), the Genesis mission actually returned silicon exposed to four different solar wind regimes: bulk, high speed, low speed, and coronal mass ejections. Each of these solar wind regimes varies in energy, but may vary in composition as well. While determining the composition is a primary goal of the mission, we are also interested in the variation in depth and extent of the damage layer as a function of solar wind regime. Here, we examine flight Si from the bulk solar wind regime and compare the results to both pristine and artificially implanted Si. Finally, there were four samples which were mounted in an electrostatic "concentrator" designed to reject a large fraction (>85%) of incoming protons while enhancing the concentration of ions mass 4-28 amu by a factor of at least 20. Two of these samples were single crystal 6H silicon carbide. (The others were polycrystalline CVD diamond and amorphous carbon that were not examined in the work.) The ion damaged SiC samples from the concentrator were studied in comparison to the flight Si from the bulk array to understand differences in the extent of the damage.

McNamara, K. M.; Synowicki, R. A.; Tiwald, T. E.

2007-01-01

303

Coronal Magnetic Field Topology and Source of Fast Solar Wind  

NASA Technical Reports Server (NTRS)

We have developed a steady state, 2D semi-empirical MHD model of the solar corona and the solar wind with many surprising results. This model for the first time shows, that the boundary between the fast and the slow solar wind as observed by Ulysses beyond 1 AU, is established in the low corona. The fastest wind observed by Ulysses (680-780 km/s) originates from the polar coronal holes at 70 -90 deg. latitude at the Sun. Rapidly diverging magnetic field geometry accounts for the fast wind reaching down to a latitude of +/- 30 deg. at the orbit of Earth. The gradual increase in the fast wind observed by Ulysses, with latitude, can be explained by an increasing field strength towards the poles, which causes Alfven wave energy flux to increase towards the poles. Empirically, there is a direct relationship between this gradual increase in wind speed and the expansion factor, f, computed at r greater than 20%. This relationship is inverse if f is computed very close to the Sun.

Guhathakurta, M.; Sittler, E.; Fisher, R.; McComas, D.; Thompson, B.

1999-01-01

304

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

SciTech Connect

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

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

2013-06-13

305

ACCELERATION OF THE SOLAR WIND BY ALFVEN WAVE PACKETS  

SciTech Connect

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

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

2013-01-20

306

THE SPECTROSCOPIC FOOTPRINT OF THE FAST SOLAR WIND  

SciTech Connect

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

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

2011-01-20

307

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

E-print Network

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

Holappa, Lauri; Asikainen, Timo

2015-01-01

308

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

NASA Technical Reports Server (NTRS)

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

Neugebauer, M.

1992-01-01

309

Exploring the Solar Wind and Coronal Mass Ejections  

NSDL National Science Digital Library

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

310

On the Origin of Mid-latitude Fast Wind: Challenging the Two-state Solar Wind Paradigm  

NASA Astrophysics Data System (ADS)

The bimodal paradigm of solar wind describes a slow solar wind situated near the heliospheric current sheet while a fast wind overexpands from the poles to fill in the remainder of the heliosphere. In this paper, we challenge this paradigm and focus here on mid-latitude wind using three fast-latitude passes completed by the Ulysses spacecraft. Based on its composition and dynamic properties, we discuss how this wind differs from both the fast, polar coronal hole wind and the low latitude, streamer-associated slow solar wind. Using a detailed analysis of ionic and elemental abundances, as well as solar wind dynamic properties, we conclude that there is a third quasi-stationary solar wind state, called the boundary wind. This boundary wind is characterized by a charge-state distribution that is similar to slow wind, but with an elemental composition that is coronal hole like. Based on these data, we present arguments for the location of the origin of this wind. We conclude that the boundary wind is a subset of the fast wind emanating from regions close to the boundaries of coronal holes and is accelerated by a similar process.

Stakhiv, Mark; Landi, Enrico; Lepri, Susan T.; Oran, Rona; Zurbuchen, Thomas H.

2015-03-01

311

Anisotropic winds from close-in extra-solar planets  

E-print Network

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

James M. Stone; Daniel Proga

2008-12-13

312

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2013-12-23

313

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

E-print Network

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

Ng, Chung-Sang

314

Fine Structure of the Solar Wind Turbulence Inferred from Simultaneous Radio Occultation Observations at  

E-print Network

at heliocentric distances 10 R most likely results from continual deformation of the solar wind density of the solar wind. Strictly speaking, this assump- tion is valid only at large heliocentric distances where

Padmanabhan, Janardhan

315

A Model fot the Sources of the Slow Solar Wind  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

316

Solar Wind Characteristics from SOHO-Sun-Ulysses Quadrature Observations  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

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

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

319

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

E-print Network

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

California at Berkeley, University of

320

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

E-print Network

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

Richardson, John

321

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

322

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

323

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

E-print Network

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

Padmanabhan, Janardhan

324

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

E-print Network

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

Padmanabhan, Janardhan

2006-01-01

325

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

E-print Network

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

326

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

E-print Network

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

California at Berkeley, University of

327

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

E-print Network

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

Li, Xinlin

328

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

E-print Network

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

California at Berkeley, University of

329

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

E-print Network

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

Zhao, Xuepu

330

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

E-print Network

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

Ng, Chung-Sang

331

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

E-print Network

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

Meyer-Vernet, Nicole

332

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

E-print Network

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

Lummerzheim, Dirk

333

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

E-print Network

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

Russell, Christopher T.

334

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

E-print Network

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

Lummerzheim, Dirk

335

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

E-print Network

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

Eriksson, Stefan

336

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

E-print Network

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

Russell, Christopher T.

337

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

E-print Network

The structure and origin of magnetic clouds in the solar wind V. Bothmer1 * and R. Schwenn2 1 Space in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large- scale to be proportional to RÀ2X4 , thus being stronger compared to the average solar wind. Four dierent magnetic con

Boyer, Edmond

338

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

E-print Network

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

Ghil, Michael

339

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

E-print Network

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

Gruntman, Mike

340

Specification of >2 MeV geosynchronous electrons based on solar wind measurements  

E-print Network

Specification of >2 MeV geosynchronous electrons based on solar wind measurements E. Burin des affected by the solar wind. Statistical asynchronous regression (SAR), a statistical method recently use measurements directly from the solar wind, instead of the Kp index, and the SAR method

Li, Xinlin

341

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

E-print Network

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

Li, Xinlin

342

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

E-print Network

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

Sitnov, Mikhail I.

343

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

E-print Network

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

Higuchi, Tomoyuki

344

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

E-print Network

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

Richardson, John

345

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

E-print Network

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

346

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

E-print Network

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

Richardson, John

347

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

E-print Network

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

De Sterck, Hans

348

Solar-Wind Conditions During the Initial Phase of the Genesis Mission  

NASA Technical Reports Server (NTRS)

We describe solar-wind conditions, including relative fractions of the solar-wind regimes (interstream, coronal hole, coronal mass ejections), during initial Genesis solar-wind sample collection, and give implications for eventual sample analysis. Additional information is contained in the original extended abstract.

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

2002-01-01

349

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

E-print Network

1 of 2 Title: Feasibility Study for 20 MW Hybrid Solar and Wind Park in Colombia Principal to assess the Colombian solar and wind resources, looking at different technology options, anticipated performance, and evaluating the economics of solar and wind power technologies. The NMSU team also evaluates

Johnson, Eric E.

350

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

351

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

352

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

353

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

354

Self-Consistent and Time-Dependent Solar Wind Models  

NASA Technical Reports Server (NTRS)

We describe the first results from a self-consistent study of Alfven waves for the time-dependent, single-fluid magnetohydrodynamic (MHD) solar wind equations, using a modified version of the ZEUS MHD code. The wind models we examine are radially symmetrical and magnetized; the initial outflow is described by the standard Parker wind solution. Our study focuses on the effects of Alfven waves on the outflow and is based on solving the full set of the ideal nonlinear MHD equations. In contrast to previous studies, no assumptions regarding wave linearity, wave damping, and wave-flow interaction are made; thus, the models naturally account for the back-reaction of the wind on the waves, as well as for the nonlinear interaction between different types of MHD waves. Our results clearly demonstrate when momentum deposition by Alfven waves in the solar wind can be sufficient to explain the origin of fast streams in solar coronal holes; we discuss the range of wave amplitudes required to obtained such fast stream solutions.

Ong, K. K.; Musielak, Z. E.; Rosner, R.; Suess, S. T.; Sulkanen, M. E.

1997-01-01

355

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

Microsoft Academic Search

We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were

A. R. Breen; R. A. Fallows; M. M. Bisi; P. Thomasson; C. A. Jordan; G. Wannberg; R. A. Jones

2006-01-01

356

Evidence for Langmuir wave tunneling in the inhomogeneous solar wind  

E-print Network

Evidence for Langmuir wave tunneling in the inhomogeneous solar wind A. J. Willes School of Physics 23 October 2002. [1] Spacecraft observations of beat-like Langmuir waveforms on two orthogonal-angle reflection of Langmuir waves from density inhomogeneities or nonlinear decay processes. However

California at Berkeley, University of

357

Genesis Solar-Wind Sample Return Mission: The Materials  

NASA Technical Reports Server (NTRS)

The Genesis spacecraft has two primary instruments which passively collect solar wind. The first is the collector arrays , a set of panels, each of which can deploy separately to sample the different kinds of solar wind (regimes). The second is the concentrator, an electrostatic mirror which will concentrate ions of mass 4 through mass 25 by about a factor of 20 by focusing them onto a 6 cm diameter target. When not deployed, these instruments fit into a compact canister. After a two year exposure time, the deployed instruments can be folded up, sealed into the canister, and returned to earth for laboratory analysis. Both the collector arrays and the concentrator will contain suites of ultra-high purity target materials, each of which is tailored to enable the analysis of a different family of elements. This abstract is meant to give a brief overview of the Genesis mission, insight into what materials were chosen for flight and why, as well as head s up information as to what will be available to planetary scientist for analysis when the solar-wind samples return to Earth in 2003. Earth. The elemental and isotopic abundances of the solar wind will be analyzed in state-of-the-art laboratories, and a portion of the sample will be archived for the use of future generations of planetary scientists. Technical information about the mission can be found at www.gps.caltech.edu/genesis.

Jurewicz, A. J. G.; Burnett, D. S.; Wiens, R. C.; Woolum, D.

2003-01-01

358

Pioneer 10 observations of the solar wind interaction with Jupiter  

Microsoft Academic Search

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

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

1974-01-01

359

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

360

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

361

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

362

The Solar Wind in the Outer Heliosphere and Heliosheath  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

363

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

364

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

365

Genesis Solar-Wind Sample Return Mission: The Materials  

NASA Technical Reports Server (NTRS)

This abstract is a brief overview of the Genesis mission. Included is an instrument description, what materials were chosen for capturing solar wind and why, and information as to what will be available for analysis when the samples return to Earth in 2003.

Jurewicz, A. J. G.; Burnett, D. S.; Wiens, R. C.; Woolum, D.

2000-01-01

366

Solar Wind Monitoring with SWIM-SARA Onboard Chandrayaan-1  

NASA Astrophysics Data System (ADS)

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

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

367

Hydro, Solar, Wind The Future of Renewable Energy  

E-print Network

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

Lavaei, Javad

368

Solar wind interaction with Comet Bennett (1969i  

NASA Technical Reports Server (NTRS)

The relations are examined between the solar-wind and Comet Bennett during the period 23 March to 5 April 1970. A large kink was observed in the ion tail of the comet on April 4, but no solar wind stream was observed in the ecliptic plane which could have caused the kink. Thus, either there was no correlation between the solar wind at the earth and that at Comet Bennett (which was 40 deg above the ecliptic) or the kink was caused by something other than a high-speed stream. The fine structure visible in photographs of the kink favors the second of these alternatives. It is shown that a shock probably passed through Comet Bennett on March 31, but no effect was seen in photographs of the comet. A stream preceded by another shock and a large abrupt change in momentum flux might have intercepted the comet between 24 March and 28 March, but again no effect was seen in photographs of the Comet. In view of these results, the possibility must be considered that a large, abrupt change in momentum flux of the solar-wind is neither necessary nor sufficient to cause a large kink in a comet tail.

Burlaga, L. F.; Rahe, J.; Donn, B. D.; Neugebauer, M.

1972-01-01

369

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

370

Proton corebeam system in the expanding solar wind: Hybrid simulations  

E-print Network

Proton corebeam system in the expanding solar wind: Hybrid simulations Petr Hellinger1,2 and Pavel 9 November 2011. [1] Results of a twodimensional hybrid expanding box simulation of a proton to a decrease of the ratio between the proton perpendicular and parallel temperatures as well as to an increase

California at Berkeley, University of

371

Livestock water pumping with wind and solar power  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

372

How Reliable Is the Prediction of Solar Wind Background?  

NASA Astrophysics Data System (ADS)

The prediction of solar wind background is a necessary part of space weather forecasting. Multiple coronal and heliospheric models have been installed at the Community Coordinated Modeling Center (CCMC) to produce the solar wind, including the Wang-Sheely-Arge (WSA)-Enlil model, MHD-Around-a-Sphere (MAS)-Enlil model, Space Weather Modeling Framework (SWMF), and heliospheric tomography using interplanetary scintillation (IPS) data. By comparing the modeling results with the OMNI data over 7 Carrington rotations in 2007, we have conducted a third-party validation of these models for the near-Earth solar wind. This work will help the models get ready for the transition from research to operation. Besides visual comparison, we have quantitatively assessed the models’ capabilities in reproducing the time series and statistics of solar wind parameters. Using improved algorithms, we have identified magnetic field sector boundaries (SBs) and slow-to-fast stream interaction regions (SIRs) as focused structures. The success rate of capturing them and the time offset vary largely with models. For this period, the 2014 version of MAS-Enlil model works best for SBs, and the heliospheric tomography works best for SIRs. General strengths and weaknesses for each model are identified to provide an unbiased reference to model developers and users.

Jian, Lan K.; MacNeice, Peter; Taktakishvili, Aleksandre; Odstrcil, Dusan; Jackson, Bernard; Yu, Hsiu-Shan; Riley, Pete; Sokolov, Igor

2015-04-01

373

Tsallis non-extensive statistics and solar wind plasma complexity  

NASA Astrophysics Data System (ADS)

This article presents novel results revealing non-equilibrium phase transition processes in the solar wind plasma during a strong shock event, which took place on 26th September 2011. Solar wind plasma is a typical case of stochastic spatiotemporal distribution of physical state variables such as force fields (B ? , E ?) and matter fields (particle and current densities or bulk plasma distributions). This study shows clearly the non-extensive and non-Gaussian character of the solar wind plasma and the existence of multi-scale strong correlations from the microscopic to the macroscopic level. It also underlines the inefficiency of classical magneto-hydro-dynamic (MHD) or plasma statistical theories, based on the classical central limit theorem (CLT), to explain the complexity of the solar wind dynamics, since these theories include smooth and differentiable spatial-temporal functions (MHD theory) or Gaussian statistics (Boltzmann-Maxwell statistical mechanics). On the contrary, the results of this study indicate the presence of non-Gaussian non-extensive statistics with heavy tails probability distribution functions, which are related to the q-extension of CLT. Finally, the results of this study can be understood in the framework of modern theoretical concepts such as non-extensive statistical mechanics (Tsallis, 2009), fractal topology (Zelenyi and Milovanov, 2004), turbulence theory (Frisch, 1996), strange dynamics (Zaslavsky, 2002), percolation theory (Milovanov, 1997), anomalous diffusion theory and anomalous transport theory (Milovanov, 2001), fractional dynamics (Tarasov, 2013) and non-equilibrium phase transition theory (Chang, 1992).

Pavlos, G. P.; Iliopoulos, A. C.; Zastenker, G. N.; Zelenyi, L. M.; Karakatsanis, L. P.; Riazantseva, M. O.; Xenakis, M. N.; Pavlos, E. G.

2015-03-01

374

Iron charge states observed in the solar wind  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

375

The source of electrostatic fluctuations in the solar-wind  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

376

MHD turbulence in the solar wind-comet interaction region  

Microsoft Academic Search

One of the most striking features discovered during the encounter of space probe ICE and comet Giacobini-Zinner was the presence of intensive MHD turbulence even at large distances from the comet. In this paper it is shown that the mass loading of the solar wind with cometary ions can cause such a phenomenon.

R. Z. Sagdeev; V. D. Shapiro; V. I. Shevchenko; K. Szego

1986-01-01

377

Probabilistic performance assessment of autonomous solar-wind energy conversion systems  

Microsoft Academic Search

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

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

1999-01-01

378

Structural stability of concrete wind turbines and solar chimney towers exposed to dynamic wind action  

Microsoft Academic Search

Apart from burning classical fossil resources or generating nuclear power, alternatives have been developed, like the classical ways to capture energy from wind, water and sun, or the innovative solar chimney concept.The paper presents some structural aspects of classical wind energy turbines, like their high-cycle dynamic loading and reaction as well as their fatigue behaviour. Actual research results concerning pre-stressed

Reinhard Harte; Gideon P. A. G. Van Zijl

2007-01-01

379

Reversed energy-latitude dependence of ion precipitation boundary: observations and possible mechanisms  

NASA Astrophysics Data System (ADS)

A previous survey by Donovan et al. [2003] revealed that there exist two typical patterns in terms of the energy-latitude dependence of the ion precipitation boundary. In one common pattern, the precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. Correspondently, at a fixed latitude, the isotropic ratio, defined as the ratio between the precipitation flux and the trapped flux, tends to be higher (lower) for protons with higher (lower) energies. This pattern conforms to the scenario of the pitch-angle scattering of protons led by the field line curvature in the equatorial magnetosphere, which is well recognized as a major mechanism leading to the precipitation of plasma sheet protons. The second pattern, albeit less common than the first one, features distinctly 'reversed' energy-latitude dependences of the ion precipitation boundary, namely that, (a) the isotropic ratio diminishes at higher (lower) latitudes for protons with higher (lower) energies; (b) at a fixed latitude the isotropic ratio tends to be lower (higher) for protons with higher (lower) energies. Donovan et al. [2003] further noted that latter "reversed-type" events predominantly occur in midnight-morning MLT sectors, while their underlying mechanisms remain to be explored. In this study, we present detailed analyses of a few events with this 'reversed' energy-latitude dependence of the ion precipitation boundary, based upon joint observations from low-Earth-orbit satellites and THEMIS in-situ probes. We explore two potential mechanisms: the ion acceleration led by downward parallel electric field in the topside ionosphere, and the pitch-angle scattering of plasma sheet protons by electromagnetic ion cyclotron (EMIC) waves in the equatorial tail. Both mechanisms may act to enhance the precipitation fluxes of protons in energy range mainly between a few hundred eV and several keV; when they are operative in a region southward/earthward of the b2i boundary, which is mainly controlled by the field line curvature, an apparently 'reversed' energy-latitude variation of ion precipitations may be observed in that region. Based upon existing theories and surveys on the downward parallel electric fields and the EMIC waves, we are also able to explain the statistical prevalence of the "reversed-type" events in the postmidnight sector as revealed in Donovan et al. [2003]. Donovan, E., B. Jackel, D. Klumpar, and R. Strangeway (2003), Energy dependence of the isotropy boundary latitude, Proc. of Atmos. Studies by Optical Methods, Sodankyla Geophysical Observatory Publications , Finland, 92:11-14.

Liang, J.; Donovan, E.; Ni, B.; Angelopoulos, V.

2013-12-01

380

MESSENGER observations of Mercury's magnetosphere under extreme solar wind conditions  

NASA Astrophysics Data System (ADS)

MESSENGER observations of Mercury's dayside magnetosphere near local noon have been examined to identify instances of extremely high solar wind ram pressure and/or strong southward magnetosheath magnetic field. Intervals of high solar wind ram pressure were defined on the basis of magnetic field intensity, B, just inside the magnetopause of ~300 nT or greater. If the internal plasma pressure is negligible, the corresponding upstream solar wind pressure is at least ~ 36 nPa. Intense southward magnetic field in the magnetosheath was defined to be at least ~200 nT in magnitude. Four instances of high solar wind pressure during subsolar magnetospheric passes were identified, two with northward magnetosheath magnetic field, one with intense southward magnetic field, and one with intense, but variable north-south magnetic field. One interval of intense southward magnetosheath magnetic field was found with only a moderately high (B ~ 200 nT) solar wind ram pressure. Despite Mercury's magnetic dipole field having a moment of only 190-200 nT-RM3, where RM is Mercury's radius, the subsolar magnetopause was found to stand off from the planetary surface by at least 0.25 RM for each magnetopause crossing even when high ram pressure was accompanied by an intense southward magnetosheath magnetic field. Analysis of the magnetopause location and magnetic field intensity shows that the magnetic fields of greater than ~ 250 nT at ~ 0.25 RM altitude cannot be the result of just Mercury's internal magnetic field and the magnetic field produced by the Chapman-Ferraro current system; additional magnetic fields, most likely due to induction currents in the outer layers of Mercury's interior, are also required. The three intervals with strong southward magnetosheath magnetic field all yielded intense reconnection signatures at the magnetopause, including strong magnetic field normal to the magnetopause; jetting of magnetosheath plasma away from the equatorial regions; showers of flux transfer events; and deep, broad diamagnetic decreases in the cusp. These results suggest that although Mercury's surface is shielded from direct solar wind impact at low to moderate latitudes even during intervals of intense reconnection and very high ram pressure by magnetic field induction inside the planet, the solar wind precipitation in the cusp region appears to maximize under such conditions.

Slavin, J. A.; DiBraccio, G. A.; Gershman, D. J.; Imber, S. M.; Sundberg, T.; Boardsen, S. A.; Sarantos, M.; Anderson, B. J.; Korth, H.; Zurbuchen, T.; Raines, J. M.; Ho, G. C.; Krimigis, S. M.; Baker, D. N.; Johnson, C. L.; Winslow, R. M.; Killen, R. M.; McNutt, R. L.; Solomon, S. C.

2012-12-01

381

Solar wind induced magnetic field around the unmagnetized Earth  

E-print Network

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

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

2004-04-29

382

Solar-wind krypton and solid/gas fractionation in the early solar nebula  

NASA Technical Reports Server (NTRS)

The solar-system Kr abundance is calculated from solar-wind noble-gas ratios, determined previously by low-temperature oxidations of lunar ilmenite grains, normalized to Si by spacecraft solar-wind measurements. The estimated Kr-83 abundance of 4.1 + or - 1.5 per million Si atoms is within uncertainty of estimates assuming no fractionation, determined from CI-chondrite abundances of surrounding elements. This is significant because it is the first such constraint on solid/gas fractionation, though the large uncertainty only confines it to somewhat less than a factor of two.

Wiens, Roger C.; Burnett, D. S.; Neugebauer, M.; Pepin, R. O.

1991-01-01

383

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

PubMed

The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is 'typical' solar wind, even when the Sun is relatively inactive. PMID:25685422

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

2013-05-01

384

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

PubMed Central

The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is ‘typical’ solar wind, even when the Sun is relatively inactive. PMID:25685422

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

2012-01-01

385

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

SciTech Connect

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

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

2013-05-10

386

Photonic spin control for solar wind electric sail  

NASA Astrophysics Data System (ADS)

The electric solar wind sail (E-sail) is a novel, efficient propellantless propulsion concept which utilises the natural solar wind for spacecraft propulsion with the help of long centrifugally stretched charged tethers. The E-sail requires auxiliary propulsion applied to the tips of the main tethers for creating the initial angular momentum and possibly for modifying the spinrate later during flight to counteract the orbital Coriolis effect and possibly for mission specific reasons. We introduce the possibility of implementing the required auxiliary propulsion by small photonic blades (small radiation pressure solar sails). The blades would be stretched centrifugally. We look into two concepts, one with and one without auxiliary tethers. The use of small photonic sails has the benefit of providing sufficient spin modification capability for any E-sail mission while keeping the technology fully propellantless. We conclude that small photonic sails appear to be a feasible and attractive solution to E-sail spinrate control.

Janhunen, Pekka

2013-02-01

387

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

388

Ulysses probes solar wind, interstellar gas  

NASA Technical Reports Server (NTRS)

The ESA-NASA Ulysses mission will furnish high-latitude observations which may deepen current understanding of the outward flow of gases from the magnetically open regions of the sun. Also furnished will be a clearer view of the processes in the Galaxy that create cosmic rays, and how cosmic rays enter the solar system. The Ulysses mission has already achieved important new results during its travel in the ecliptic plane; the density and temperature of the interstellar neutral He flowing into the solar system has been directly measured.

Goldstein, Bruce

1992-01-01

389

Terrestrial Accretion from the Solar Wind  

Microsoft Academic Search

MR. HARRISON has raised a number of important issues which can only be answered tentatively at the present time. Presumably the oxygen is liberated from terrestrial rocks by solar ultra-violet radiation, and an estimate of the mean quantum efficiency of this photochemical process should be readily obtainable in the laboratory, by irradiation of outgassed rock samples in an evacuated chamber,

C. M. de. Turville

1961-01-01

390

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

391

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

392

Capture of Solar Wind He++ by the Martian Exosphere  

NASA Astrophysics Data System (ADS)

The quantity of helium in the Martian atmosphere can be estimated from its emission line at 58 4nm Krasnopolsky and Gladstone Icarus vol 176 395-407 2005 and references therein Considering the necessary balance between losses through escape to the interplanetary medium and sources Krasnopolsky and coworkers have established that radioactive decay of uranium and thorium provides only one third of the lost helium They argue that the remaining two thirds should be captured from the solar wind This external source of Martian helium was also suggested by Barabash et al JGR 100 A11 21307 1995 Brecht JGR 102 A6 11287 1997 has estimated the deposition of protons into the Martian atmosphere from 3d hybrid simulation of the interaction of Mars with a solar wind made of protons and electrons only From these results Brecht gave an estimate of the deposition of solar helium ions into the Martian atmosphere based on scaling arguments In the recent past we have developed a consistent multi-species 3d hybrid model of the interaction of solar wind protons and alpha particles with the Martian plasma environment taking into account the ionisation of the oxygen and hydrogen neutral coronas of Mars Modolo et al Ann Geophys 23 433 2005 Neutral species are ionised by photons and by electron impacts the two processes are simulated consistently and independently through the specification of ionisation frequencies and cross sections Charge exchange reactions of protons and oxygen ions with hydrogen and oxygen atoms are taken into account

Chanteur, G. M.; Modolo, R.; Dubinin, E.

393

Small solar wind transients: Stereo-A observations in 2009  

SciTech Connect

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

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

2013-06-13

394

Invited article: Electric solar wind sail: toward test missions.  

PubMed

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. PMID:21133454

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

395

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

396

Twisted magnetic flux tubes in the solar wind  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

397

Solar Wind Fluctuations and Their Consequences on the Magnetosphere  

NASA Technical Reports Server (NTRS)

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

Li, Xin-Lin

2005-01-01

398

Solar Wind Conditions and Composition During the Genesis Mission as Measured by in situ Spacecraft  

NASA Astrophysics Data System (ADS)

We describe the Genesis mission solar-wind sample collection period and the solar wind conditions at the L1 point during this 2.3-year period. In order to relate the solar wind samples to solar composition, the conditions under which the samples were collected must be understood in the context of the long-term solar wind. We find that the state of the solar wind was typical of conditions over the past four solar cycles. However, Genesis spent a relatively large fraction of the time in coronal-hole flow as compared to what might have been expected for the declining phase of the solar cycle. Data from the Solar Wind Ion Composition Spectrometer (SWICS) on the Advanced Composition Explorer (ACE) are used to determine the effectiveness of the Genesis solar-wind regime selection algorithm. The data collected by SWICS confirm that the Genesis algorithm successfully separated and collected solar wind regimes having distinct solar origins, particularly in the case of the coronal hole sample. The SWICS data also demonstrate that the different regimes are elementally fractionated. When compared with Ulysses composition data from the previous solar cycle, we find a similar degree of fractionation between regimes as well as fractionation relative to the average photospheric composition. The Genesis solar wind samples are under long-term curation at NASA Johnson Space Center so that as sample analysis techniques evolve, pristine solar wind samples will be available to the scientific community in the decades to come. This article and a companion paper (Wiens et al. 2013, this issue) provide post-flight information necessary for the analysis of the Genesis array and foil solar wind samples and the Genesis solar wind ion concentrator samples, and thus serve to complement the Space Science Review volume, The Genesis Mission (v. 105, 2003).

Reisenfeld, Daniel B.; Wiens, Roger C.; Barraclough, Bruce L.; Steinberg, John T.; Neugebauer, Marcia; Raines, Jim; Zurbuchen, Thomas H.

2013-06-01

399

Observations of Rapid Velocity Variations in the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

The technique of interplanetary scintillation (IPS) is the observation of rapid fluctuations of the radio signal from an astronomical compact source as the signal passes through the ever-changing density of the solar wind. Cross-correlation of simultaneous observations of IPS from a single radio source, received at multiple sites of the European Incoherent SCATter (EISCAT) radio antenna network, is used to determine the velocity of the solar wind material passing over the lines of sight of the antennas. Calculated velocities reveal the slow solar wind to contain rapid velocity variations when viewed on a time-scale of several minutes. Solar TErrestrial RElations Observatory (STEREO) Heliospheric Imager (HI) observations of white-light intensity have been compared with EISCAT observations of IPS to identify common density structures that may relate to the rapid velocity variations in the slow solar wind. We have surveyed a one-year period, starting in April 2007, of the EISCAT IPS observing campaigns beginning shortly after the commencement of full science operations of the STEREO mission in a bid to identify common density structures in both EISCAT and STEREO HI datasets. We provide a detailed investigation and presentation of joint IPS/HI observations from two specific intervals on 23 April 2007 and 19 May 2007 for which the IPS P-Point (point of closest approach of the line of sight to the Sun) was between 72 and 87 solar radii out from the Sun's centre. During the 23 April interval, a meso-scale (of the order of 105 km or larger) transient structure was observed by HI-1A to pass over the IPS ray path near the P-Point; the observations of IPS showed a micro-scale structure (of the order of 102 km) within the meso-scale transient. Observations of IPS from the second interval, on 19 May, revealed similar micro-scale velocity changes, however, no transient structures were detected by the HIs during that period. We also pose some fundamental thoughts on the slow solar wind structure itself.

Hardwick, S. A.; Bisi, M. M.; Davies, J. A.; Breen, A. R.; Fallows, R. A.; Harrison, R. A.; Davis, C. J.

2013-07-01

400

Solar flux variations at 175 and 304 Å and their relation to solar wind parameters  

NASA Astrophysics Data System (ADS)

Variations of solar emission in the spectral ranges corresponding to the transition region (304 Å) and corona (175 Å) and their relation to solar wind parameters are investigated for the maximum and declining phase of solar cycle 23 (2001 2004) based on the CORONAS-F/SPIRIT data. It is shown that the variations of solar flux in both ranges are similar and demonstrate a high correlation for long data series. Meanwhile, some time intervals were registered when the intensity variations at 304 Å are delayed with respect to those in 175 Å by, on average, two days. For long periods, the spectra of the full-disk flux at 175 Å and of the solar wind density are close to each other; the same is true for the solar flux spectrum in the 304-Å range and the spectrum of the solar wind velocity. The assumption is made that active processes in the lower corona mainly affect long-period density variations, while the velocity characterizes the kinetics of the total stream of the outflowing matter and its long-term variations are considerably related to the physics of processes occurring deeper in the Sun.

Khabarova, O. V.; Kuzin, S. V.; Bogachev, S. A.; Pertsov, A. A.

2006-07-01

401

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

NASA Technical Reports Server (NTRS)

The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from S to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005 -2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (approx.1980, approx.1990, and approx. 2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995-1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27 -day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the > 2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods, showing that processes in the magnetosphere act as a low-pass filter between the solar wind and the radiation belt. The A(sub p)/K(sub p) magnetic currents observed at subauroral latitudes are sensitive to proton auroral precipitation, especially for 9-day and shorter periods, while the A(sub p)/K(sub p) currents are governed by electron auroral precipitation for 13.5- and 27-day periodicities.

Emery, Barbara A.; Richardson, Ian G.; Evans, David S.; Rich, Frederick J.; Wilson, Gordon R.

2011-01-01

402

Why is the Fast Solar Wind Fast and the Slow Solar Wind Slow? A Survey of Geometrical Models  

E-print Network

Four decades have gone by since the discovery that the solar wind at 1 AU seems to exist in two relatively distinct states: slow and fast. There is still no universal agreement concerning the primary physical cause of this apparently bimodal distribution, even in its simplest manifestation at solar minimum. In this presentation we review and extend a series of ideas that link the different states of solar wind to the varying superradial geometry of magnetic flux tubes in the extended corona. Past researchers have emphasized different aspects of this relationship, and we attempt to disentangle some of the seemingly contradictory results. We apply the hypothesis of Wang and Sheeley (as well as Kovalenko) that Alfven wave fluxes at the base are the same for all flux tubes to a recent model of non-WKB Alfven wave reflection and turbulent heating, and we predict coronal heating rates as a function of flux tube geometry. We compare the feedback of these heating rates on the locations of Parker-type critical points, and we discuss the ranges of parameters that yield a realistic bifurcation of wind solutions into fast and slow. Finally, we discuss the need for next-generation coronagraph spectroscopy of the extended corona - especially measurements of the electron temperature above 1.5 solar radii - in order to confirm and refine these ideas.

Steven R. Cranmer

2005-06-21

403

On the solar cycle dependence of winds and planetary waves as seen from mid-latitude D1 LF mesopause region wind measurements*  

E-print Network

On the solar cycle dependence of winds and planetary waves as seen from mid-latitude D1 LF-term trends and in¯uences of solar variability. The response of the prevailing wind to the 11-year solar cycle the measurements. This is connected with stronger vertical gradients of the zonal prevailing wind during solar

Paris-Sud XI, Université de

404

Coronal sources of the intrastream structure of the solar wind  

NASA Technical Reports Server (NTRS)

Short time scale changes in the bulk speed were found not to coincide with X-ray transients near the sub-earth point nor with the number of X-ray bright points within a coronal hole and near the equator. The changes in bulk speed, it is shown, are associated with changes in light areas in a hole which may be associated with the opening or closing of magnetic field lines within the coronal hole. That there is a causal connection between these sudden changes (apperance or disappearance) in light area and sudden changes in the bulk speed of the solar wind is further evidenced by the spatial proximity on the Sun of these changing light regions to the source position of stream lines from Levine's model that connect into the same solar wind streams.

Sullivan, J. D.; Bridge, H. S.

1983-01-01

405

Mass fractionation of the lunar surface by solar wind sputtering  

NASA Technical Reports Server (NTRS)

The sputtering of the lunar surface by the solar wind is examined as a possible mechanism of mass fractionation. Simple arguments based on current theories of sputtering and the ballistics of the sputtered atoms suggest that most ejected atoms will have sufficiently high energy to escape lunar gravity. However, the fraction of atoms which falls back to the surface is enriched in the heavier atomic components relative to the lighter ones. This material is incorporated into the heavily radiation-damaged outer surfaces of grains where it is subject to resputtering. Over the course of several hundred years an equilibrium surface layer, enriched in heavier atoms, is found to form. The dependence of the calculated results upon the sputtering rate and on the details of the energy spectrum of sputtered particles is investigated. It is concluded that mass fractionation by solar wind sputtering is likely to be an important phenomenon on the lunar surface.

Switkowski, Z. E.; Haff, P. K.; Tombrello, T. A.; Burnett, D. S.

1975-01-01

406

Predicted Impacts of Proton Temperature Anisotropy on Solar Wind Turbulence  

E-print Network

Particle velocity distributions measured in the weakly collisional solar wind are frequently found to be non-Maxwellian, but how these non-Maxwellian distributions impact the physics of plasma turbulence in the solar wind remains unanswered. Using numerical solutions of the linear dispersion relation for a collisionless plasma with a bi-Maxwellian proton velocity distribution, we present a unified framework for the four proton temperature anisotropy instabilities, identifying the associated stable eigenmodes, highlighting the unstable region of wavevector space, and presenting the properties of the growing eigenfunctions. Based on physical intuition gained from this framework, we address how the proton temperature anisotropy impacts the nonlinear dynamics of the \\Alfvenic fluctuations underlying the dominant cascade of energy from large to small scales and how the fluctuations driven by proton temperature anisotropy instabilities interact nonlinearly with each other and with the fluctuations of the large-scal...

Klein, Kristopher G

2015-01-01

407

Residual energy in magnetohydrodynamic turbulence and in the solar wind  

E-print Network

Recent observations indicate that kinetic and magnetic energies are not in equipartition in the solar wind turbulence. Rather, magnetic fluctuations are more energetic and have somewhat steeper energy spectrum compared to the velocity fluctuations. This leads to the presence of the so-called residual energy E_r=E_v-E_b in the inertial interval of turbulence. This puzzling effect is addressed in the present paper in the framework of weak turbulence theory. Using a simple model of weakly colliding Alfv\\'en waves, we demonstrate that the kinetic-magnetic equipartition indeed gets broken as a result of nonlinear interaction of Alfv\\'en waves. We establish that magnetic energy is indeed generated more efficiently as a result of these interactions, which proposes an explanation for the solar wind observations.

Stanislav Boldyrev; Jean Carlos Perez; Vladimir Zhdankin

2011-08-30

408

Counterstreaming solar wind halo electron events on open field lines  

SciTech Connect

Counterstreaming solar wind halo electron events have been identified as a common 1 AU signature of coronal mass ejection events, and have generally been interpreted as indicative of closed magnetic field topologies, i.e., magnetic loops or flux ropes rooted at both ends in the Sun, or detached plasmoids. In this paper we examine the possibility that these events may instead occur preferentially on open field lines, and that counterstreaming results from reflection or injection behind interplanetary shocks or from mirroring from regions of compressed magnetic field farther out in the heliosphere. We conclude the neither of these suggested sources of counterstreaming electron beams is viable and that the best interpretation of observed counterstreaming electron events in the solar wind remains that of passage of closed field structures. 4 refs., 4 figs.

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

1991-01-01

409

Model for vortex turbulence with discontinuities in the solar wind  

NASA Astrophysics Data System (ADS)

A model of vortex with embedded discontinuities in plasma flow is developed in the framework of ideal MHD in a low b plasma. Vortex structures are considered as a result of 2-D evolution of nonlinear shear Alfvén waves in the heliosphere. Physical properties of the solutions and vector fields are analyzed and the observational aspects of the model are discussed. The ratio of normal components to the discontinuity Br /Vr can be close to -2. The alignment between velocity and magnetic field vectors takes place. Spacecraft crossing such vortices will typically observe a pair of discontinuities, but with dissimilar properties. Occurrence rate for different discontinuity types is estimated and agrees with observations in high-speed solar wind stream. Discontinuity crossing provides a backward rotation of magnetic field vector and can be observed as part of a backward arc. The Ulysses magnetometer data obtained in the fast solar wind are compared with the results of theoretical modelling.

Verkhoglyadova, O. P.; Dasgupta, B.; Tsurutani, B. T.

410

Turbulent heating of colliding streams in the solar wind.  

NASA Technical Reports Server (NTRS)

Turbulent heating of colliding plasma streams has previously been observed in the solar wind. The original data were interpreted in terms of a fluid model. It is contended that a plasma-kinetic description is the more appropriate theoretical approach and is necessary in order to better understand the microscopic physical phenomena that underlie all fluid models. Microscopic solar-wind parameters characteristic of conditions during the observations were used, together with the quasi-linear plasma-kinetic theory, to compute the expected magnetic field and temperature enhancements in the interaction region between two counterstreaming plasma beams. The physical mechanism of excitation is the electromagnetic two-stream instability in which Alfven waves are unstable. A total field in the interaction region of about 8 gamma and a change in temperature of about 100,000 K are obtained.

Goldstein, M. L.; Eviatar, A.

1973-01-01

411

Anisotropy of Solar Wind Turbulence in the Dissipation Range  

NASA Astrophysics Data System (ADS)

Although turbulence is readily observed in the solar wind, some aspects are poorly understood with unexplained observations and conflicting theoretical descriptions. In particular the dissipation range (fluctuations smaller than the ion gyroscale) is only just beginning to be thoroughly investigated. Here we present methods and results from a multi-spacecraft analysis of the solar wind dissipation range between the ion and electron gyroscales using the four Cluster satellites. We find that the fluctuations are anisotropic, having a higher power in the direction perpendicular to the local mean magnetic field than parallel to it. We also compare the observed anisotropic scaling to predictions for a kinetic Alfven wave cascade. The implications of anisotropic fluctuations for the interpretation of dissipation range measurements in general are also discussed.

Chen, C. H.; Horbury, T. S.; Schekochihin, A. A.; Wicks, R. T.; Alexandrova, O.

2009-12-01

412

Measuring solar wind velocity with spacecraft phase scintillations  

NASA Technical Reports Server (NTRS)

The measurement of spacecraft phase scintillations with a coherent dual-frequency radio system permits solar-wind velocity measurements based on multiple-station phase scintillations. Advantages of measuring solar-wind velocity on the basis of multiple-station phase scintillations are discussed with respect to amplitude scintillations. These advantages include the ability to carry out observations closer to the sun, a much wider range of possible baselines, a lower S/N ratio for long-baseline phase measurements, and a wider range of antenna sizes and receiver noise temperatures. NASA antennas particularly suitable for these measurements are identified, and observations with the coherent S/X radio system aboard various NASA spacecraft intended for deep-space missions are proposed.

Woo, R.

1977-01-01

413

Extended Coronal Heating and Solar Wind Acceleration Over the Solar Cycle  

E-print Network

This paper reviews our growing understanding of the physics behind coronal heating (in open-field regions) and the acceleration of the solar wind. Many new insights have come from the last solar cycle's worth of observations and theoretical work. Measurements of the plasma properties in the extended corona, where the primary solar wind acceleration occurs, have been key to discriminating between competing theories. We describe how UVCS/SOHO measurements of coronal holes and streamers over the last 14 years have provided clues about the detailed kinetic processes that energize both fast and slow wind regions. We also present a brief survey of current ideas involving the coronal source regions of fast and slow wind streams, and how these change over the solar cycle. These source regions are discussed in the context of recent theoretical models (based on Alfven waves and MHD turbulence) that have begun to successfully predict both the heating and acceleration in fast and slow wind regions with essentially no fre...

Cranmer, Steven R; Miralles, Mari Paz; van Ballegooijen, Adriaan A

2010-01-01

414

Solar Wind Influence on the Oxygen Content of Ion Outflow in the High Altitude Polar Cap During Solar Minimum Conditions  

NASA Technical Reports Server (NTRS)

We correlate solar wind and IMF properties with the properties of O(+) and H(+) in the polar cap in early 1996 during solar minimum conditions at altitudes between 5.5 and 8.9 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the POLAR satellite. Throughout the high altitude polar cap, we observe H(+) to be more abundant than O(+). H(+) is a significant fraction of both the ionosphere and the solar wind, and O(+) is not a significant species in the solar wind. O(+) is the major species in the ionosphere so the faction of O(+) present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. For these reasons, 0+ is of primary interest in this study. We observe O(+) to be most abundant at lower latitudes when the solar wind speed is low (and low Kp), and at higher solar wind speeds (and high Kp) O(+) is observed across most of the polar cap. We also find that O(+) density and parallel flux are well organized by solar wind dynamic pressure; they both increase with solar wind dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, but H(+) density and parallel flux have some negative correlation with IMF By, and some positive correlation with VswBIMF. In this solar minimum data set, H(+) is dominant so that contributions of this plasma to the plasma sheet would have a very low O(+) to H(+) ratio.

Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.

2000-01-01

415

77 FR 48138 - Topaz Solar Farms LLC; High Plains Ranch II, LLC; Bethel Wind Energy LLC; Rippey Wind Energy LLC...  

Federal Register 2010, 2011, 2012, 2013, 2014

...EG12-63-000; EG12-64-000; EG12-65-000; EG12-66-000; EG12- 67-000; EG12-68-000; EG12-69-000] Topaz Solar Farms LLC; High Plains Ranch II, LLC; Bethel Wind Energy LLC; Rippey Wind Energy LLC; Pacific Wind, LLC;...

2012-08-13

416

Finite size effects and scaling in solar wind fluctuations  

NASA Astrophysics Data System (ADS)

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.

2010-12-01

417

Venus-like interaction of the solar wind with Mars  

Microsoft Academic Search

The magnetometer and electron reflectometer experiment (MAG\\/ER) on the Mars Global Surveyor (MGS) spacecraft has obtained magnetic field and electron data which indicates that the solar wind interaction with Mars is primarily an ionospheric-atmospheric interaction similar to that at Venus. However, the global-scale electric currents and resulting magnetic fields due to the interaction at Mars are locally interrupted or perturbed

C. C. Law; D. H. Crider; P. W. Walker; Y. Chen; M. H. Acuña; J. E. P. Connerney; R. P. Lin; K. A. Anderson; D. L. Mitchell; C. W. Carlson; J. McFadden; D. A. Brain; H. Rème; C. Mazelle; J. A. Sauvaud; C. d'Uston; D. Vignes; S. J. Bauer; N. F. Ness

1999-01-01

418

Solar wind flow past Venus - Theory and comparisons  

Microsoft Academic Search

Advanced computational procedures are applied to an improved model of solar wind flow past Venus to calculate the locations of the ionopause and bow wave and the properties of the flowing ionosheath plasma in the intervening region. The theoretical method is based on a single-fluid, steady, dissipationless, magneto-hydrodynamic continuum model and is appropriate for the calculation of axisymmetric supersonic, super-Alfvenic

J. R. Spreiter; Stephen S. Stahara

1980-01-01

419

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 configuration within the magnetosphere is given. The field lines are found to be compressed on both the daytime and

Gilbert D. Mead

1964-01-01

420

Mariner 2 Observations of the Solar Wind, 1, Average Properties  

Microsoft Academic Search

This paper summarizes the properties of the positive-ion component of the solar wind observed during the four months of the Mariner 2 flight to and past Venus in 1962. The protons' average velocity and temperature were approximately 500 km\\/sec and 1.7 X 105øK, respectively. Several streams of hot, high-velocity plasma were observed to recur at 27-day intervals, with peak velocity

Marcia Neugebauer; Conway W. Snyder

1966-01-01

421

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

422

Solar wind plasma injection at the dayside magnetospheric cusp  

Microsoft Academic Search

Two mechanisms have been proposed for solar wind particle injection at the dayside magnetospheric cusps: magnetic merging and cross-field diffusion. These two mechanisms are experimentally distinguishable in that they produce different latitudinal distributions of particles penetrating to the low-altitude cusp. An examination of proton and electron measurements obtained by the AE-C satellite in the low-altitude dayside cusp reveals evidence of

P. H. Reiff; T. W. Hill; J. L. Burch

1977-01-01

423

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

424

Propagation and Evolution of ICMES in the Solar Wind  

Microsoft Academic Search

Interplanetary coronal mass ejections (ICMEs) evolve as they propagate outward from the Sun. They interact with and eventually\\u000a equilibrate with the ambient solar wind. One difficulty in studying this evolution is that ICMEs have no unique set of identifying\\u000a characteristics, so boundaries of the ICMEs are difficult to identify. Two characteristics present in some ICMEs but generally\\u000a not present in

John D. Richardson; Ying Liu; John W. Belcher

425

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

426

Wind\\/solar hybrid generation-based roadway microgrids  

Microsoft Academic Search

This paper presents the concept and design of a novel roadway microgrid. It operates as a smart microgrid that optimally utilizes the public right-of-way and roadway infrastructure to provide cost-effective, highly efficient, and reliable wind\\/solar electric power production, distribution, storage, and utilization. The fundamental unit of the microgrid is called the energy-plus roadway\\/traffic signal light (EPRTL), which contains a grid-connected

Wei Qiao; Anuj Sharma; Jerry L. Hudgins; Elizabeth G. Jones; Laurence Rilett

2011-01-01

427

First Results from SWAN Lyman ? solar wind mapper on SOHO  

Microsoft Academic Search

After one year of almost flawless operation on board the SOHO spacecraft poised at L1 Lagrange point, we report the main features\\u000a of SWAN observations. SWAN is mainly dedicated to the monitoring of the latitude distribution of the solar wind by the L?\\u000a method. Maps of sky L? emissions were recorded througout the year. The region of maximum emission, located

J. L. Bertaux; E. Quémerais; R. Lallement; E. Kyrölä; W. Schmidt; T. Summanen; J. P. Goutail; M. Berthé; J. Costa; T. Holzer

1997-01-01

428

The Latitude Dependence of the Effect of Pinatubo on Stratospheric Ozone  

NASA Technical Reports Server (NTRS)

Statistical analysis of TOMS and SBLT total ozone data indicate that the eruption of Pinatubo in 1991 led to a significant decrease in ozone at northern midlatitudes with little or no effect at southern midlatitudes. We argue that this puzzling absence of a southern hemisphere effect may be an artifact of the statistical analysis. We have run a 3D CTM simulation of the past 30 years of stratospheric photochemistry with variable forcing due to chlorine/bromine compounds, solar ultraviolet radiation, and volcanic aerosols. This integration used winds from the FVGCM, which has similar interannual variability to the atmosphere. When this CTM output was examined with a standard time-series analysis, we found an effect of Pinatubo in the southern hemisphere, but not in the northern hemisphere. We then reran the CTM without volcanic aerosols. The subtraction of the two simulations indicated that, as expected, that Pinatubo affected both hemispheres in the model. This means that the northern hemisphere effect was in the model but did not show up in the statistical analysis. We also had an on-line parameterized chemical ozone tracer with seasonally repeating production and loss over the simulation. We used this as a dynamical surrogate to remove interannual variability from the original model output. The residual time series was then analyzed for the Pinatubo effect and we were able to find it in both hemispheres. We suggest that the combination of the two volcanoes, El Chichon and Pinatubo, with the solar cycle and interannual variability led to this problem of analysis in the northern hemisphere of our model. We furthermore suggest that a similar think may be occurring in the southern hemisphere of the data. An analysis of the atmosphere's southern hemisphere with a good dynamical surrogate may solve the mystery of the missing southern hemisphere effect of Pinatubo on ozone.

Stolarski, Richard S.; Douglass, Anne R.

2004-01-01

429

Alfven Waves in the Solar Wind, Magnetosheath, and Outer Magnetosphere  

NASA Technical Reports Server (NTRS)

Alfven waves Propagating outward from the Sun are ubiquitous in the solar wind and play a major role in the solar wind-magnetosphere interaction. The passage of the waves generally occurs in the form of a series of discrete steepened discontinuities, each of which results in an abrupt change in the interplanetary magnetic field direction. Some orientations of the magnetic field permit particles energized at the Earth's bow shock to gain access to the foreshock region immediately upstream from the Earth's bow shock. The thermal pressure associated with these particles can greatly perturb solar wind plasma and magnetic field parameters shortly prior to their interaction with the Earth's bow shock and magnetosphere. The corresponding dynamic pressure variations batter the magnetosphere, driving magnetopause motion and transient compressions of the magnetospheric magnetic field. Alfven waves transmit information concerning the dynamic pressure variations applied to the magnetosphere to the ionosphere, where they generate the traveling convection vortices (TCVs) seen in high-latitude ground magnetograms. Finally, the sense of Alfvenic perturbations transmitted into the magnetosheath reverses across local noon because magnetosheath magnetic field lines drape against the magnetopause. The corresponding change in velocity perturbations must apply a weak torque to the Earth's magnetosphere.

Sibeck, D. G.

2007-01-01

430

Magnetic Discontinuities in Magnetohydrodynamic Turbulence and in the Solar Wind  

E-print Network

Recent measurements of solar wind turbulence report the presence of intermittent, exponentially distributed angular discontinuities in the magnetic field. In this Letter, we study whether such discontinuities can be produced by magnetohydrodynamic (MHD) turbulence. We detect the discontinuities by measuring the fluctuations of the magnetic field direction, Delta theta, across fixed spatial increments Delta x in direct numerical simulations of MHD turbulence with an imposed uniform guide field B_0. A large region of the probability density function (pdf) for Delta theta is found to follow an exponential decay, proportional to exp(-Delta theta/theta_*), with characteristic angle theta_* ~ (14 deg) (b_rms/B_0)^0.65 for a broad range of guide-field strengths. We find that discontinuities observed in the solar wind can be reproduced by MHD turbulence with reasonable ratios of b_rms/B_0. We also observe an excess of small angular discontinuities when Delta x becomes small, possibly indicating an increasing statistical significance of dissipation-scale structures. The structure of the pdf in this case closely resembles the two-population pdf seen in the solar wind. We thus propose that strong discontinuities are associated with inertial-range MHD turbulence, while weak discontinuities emerge from near-dissipation-range turbulence. In addition, we find that the structure functions of the magnetic field direction exhibit anomalous scaling exponents, which indicates the existence of intermittent structures.

Vladimir Zhdankin; Stanislav Boldyrev; Joanne Mason; Jean Carlos Perez

2012-04-19

431

Construction of Solar-Wind-Like Magnetic Fields  

NASA Technical Reports Server (NTRS)

Fluctuations in the solar wind fields tend to not only have velocities and magnetic fields correlated in the sense consistent with Alfven waves traveling from the Sun, but they also have the magnitude of the magnetic field remarkably constant despite their being broadband. This paper provides, for the first time, a method for constructing fields with nearly constant magnetic field, zero divergence, and with any specified power spectrum for the fluctuations of the components of the field. Every wave vector, k, is associated with two polarizations the relative phases of these can be chosen to minimize the variance of the field magnitude while retaining the\\random character of the fields. The method is applied to a case with one spatial coordinate that demonstrates good agreement with observed time series and power spectra of the magnetic field in the solar wind, as well as with the distribution of the angles of rapid changes (discontinuities), thus showing a deep connection between two seemingly unrelated issues. It is suggested that using this construction will lead to more realistic simulations of solar wind turbulence and of the propagation of energetic particles.

Roberts, Dana Aaron

2012-01-01

432

Studies of Interstellar Pickup Ions in the Solar Wind  

NASA Technical Reports Server (NTRS)

The work under this grant involves studies of the interaction of interstellar pickup ions with the solar wind, with the goal of a comprehensive model of the particle distributions and wave intensities to be expected throughout the heliosphere, as well as the interactions of those distributions with the solar wind termination shock. In the past year, we have completed a number of projects, including observations and modeling of the effects of a large scattering mean free path on the pickup He(+) seen at AMPTE, an analytical model of anisotropic pickup tons in a steady radial magnetic field, and a derivation of a reduced solar wind Mach number due to increased estimates on the inflowing hydrogen density allowing for a weak termination shock. In the next year, we plan to investigate in more detail the correspondence between our models of anisotropic pickup ions and the data on spectra, variations, and proton-He(+) correlation provided by AMPTE, Ulysses, and our instrument on SOHO. We will model the time-dependent pickup ion density resulting from finite periods of radial magnetic field. We will also incorporate the effects of a large mean free path into our analysis of the He(+) focusing cone, leading to more accurate parameter values for the interstellar helium gas. This progress report also includes a discussion of our Space Physics Educational Outreach activities in the past year and plans for the next year.

Isenberg, Philip A.; Lee, Martin A.; Mobius, Eberhard

1996-01-01

433

Solar Wind Driven Plasma Fluxes from the Venus Ionosphere  

NASA Astrophysics Data System (ADS)

SOLAR WIND DRIVEN PLASMA FLUXES FROM THE VENUS IONOSPHERE H. Pérez-de-Tejada (1), R. Lundin (2), H. Durand-Manterola (1), S. Barabash (2), T. L. Zhang (3), J. A., Sauvaud (4), and M. Reyes-Ruiz (5) 1 - Institute of Geophysics, UNAM, México, D. F. 2 - Swedish Institute of Space Physics, Kiruna, Sweden 3 - Space Research Institute, Graz, Austria 4 - CESR, Toulouse, France 5 - Institute of Astronomy, UNAM, Ensenada, México Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the kinetic pressure of planetary O+ ion fluxes measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. The momentum flux of the O+ ions leads to superalfvenic flow conditions. It is suggested that such O+ ion beams are produced in the vicinity of the magnetic polar regions of the Venus ionosphere where the solar wind erodes the local plasma leading to plasma channels that extend downstream from those regions.

Perez De Tejada, H. A.; Lundin, R. N.; Zhang, T.; Sauvaud, J. A.; Reyes-Ruiz, M.

2012-12-01

434

Solar wind interaction with Comet Bennett /1969i/.  

NASA Technical Reports Server (NTRS)

Examination of the relations between the solar-wind and Comet Bennett during the period from Mar. 23 to Apr. 5, 1970. A large kink was observed in the ion tail of the comet on April 4, but no solar-wind stream was observed in the ecliptic plane which could have caused the kink. Thus, either there was no correlation between the solar wind at the earth and that at Comet Bennett (which was 40 deg above the ecliptic) or the kink was caused by something other than a high-speed stream. The fine structure visible in photographs of the kink favors the second of these alternatives. It is shown that a shock probably passed through Comet Bennett on March 31, but no effect was seen in photographs of the comet. A stream preceded by another shock and a large abrupt change in momentum flux might have intercepted the comet between March 24 and March 28, but again no effect was seen in photographs of the Comet.

Burlaga, L. F.; Donn, B.; Neugebauer, M.; Rahe, J.

1973-01-01

435

Magnetic configurations of planetary obstacles. [solar wind obstacles  

NASA Technical Reports Server (NTRS)

The interaction between planetary magnetospheres and solar wind flow is discussed. A proper planetary magnetosphere results from the interaction of a flowing plasma with a planet having an intrinsic, global, magnetic field of sufficient strength to stand off the impinging plasma. Upstream of such an obstacle a bow shock usually exists. The known magnetospheres have severely asymmetric shapes, being elongated approximately along the solar wind flow direction. Conditions which fundamentally determine the structure of a proper planetary magnetosphere are the state of the externally flowing plasma, the planet's magnetic moment, its vector spin, and the presence and nature of internal plasma sources and any plasma sinks. Planets known to have proper magnetospheres are Earth, Mercury, Jupiter, and Saturn. Uranus and Neptune may also have magnetospheres, with that of Uranus promising to have an exotic field configuration, because the planet's magnetic moment is expected to be nearly aligned with the solar wind flow direction. Venus and Mars are also discussed. Magnetopause surface waves are mentioned.

Lepping, R. P.

1986-01-01

436

Kolmogorov spectrum of renewable wind and solar power fluctuations  

NASA Astrophysics Data System (ADS)

With increasing the contribution of renewable energies in power production, the task of reducing dynamic instability in power grids must also be addressed from the generation side, because the power delivered from such sources is spatiotemporally stochastic in nature. Here we characterize the stochastic properties of the wind and solar energy sources by studying their spectrum and multifractal exponents. The computed power spectrum from high frequency time series of solar irradiance and wind power reveals a power-law behaviour with an exponent ˜ 5/3 (Kolmogorov exponent) for the frequency domain 0.001 Hz < f < 0.05 Hz, which means that the power grid is being fed by turbulent-like sources. Our results bring important evidence on the stochastic and turbulent-like behaviour of renewable power production from wind and solar energies, which can cause instability in power grids. Our statistical analysis also provides important information that must be used as a guideline for an optimal design of power grids that operate under intermittent renewable sources of power.

Tabar, M. Reza Rahimi; Anvari, M.; Lohmann, G.; Heinemann, D.; Wächter, M.; Milan, P.; Lorenz, E.; Peinke, Joachim

2014-10-01

437

The DSCOVR Solar Wind Mission and Future Space Weather Products  

NASA Astrophysics Data System (ADS)

The Deep Space Climate Observatory (DSCOVR) mission, scheduled for launch in mid-2014, will provide real-time solar wind thermal plasma and magnetic measurements to ensure continuous monitoring for space weather forecasting. DSCOVR will orbit L1 and will serve as a follow-on mission to NASA's Advanced Composition Explorer (ACE), which was launched in 1997. DSCOVR will have a total of six instruments, two of which will provide real-time data necessary for space weather forecasting: a Faraday cup to measure the proton and alpha components of the solar wind, and a triaxial fluxgate magnetometer to measure the magnetic field in three dimensions. Real-time data provided by DSCOVR will include Vx, Vy, Vz, n, T, Bx, By, and Bz. Such real-time L1 data is used in generating space weather applications and products that have been demonstrated to be highly accurate and provide actionable information for customers. We evaluate current space weather products driven by ACE and discuss future products under development for DSCOVR. New space weather products under consideration include: automated shock detection, more accurate L1 to Earth delay time, and prediction of rotations in solar wind Bz within magnetic clouds. Suggestions from the community on product ideas are welcome.

Cash, M. D.; Biesecker, D. A.; Reinard, A. A.

2012-12-01

438

Silicon and oxygen charge state distributions and relative abundances in the solar wind measured by SWICS on Ulysses. [Solar Wind Ion Composition Spectrometer  

NASA Technical Reports Server (NTRS)

We report an initial survey of solar wind silicon and oxygen using data obtained with the Ulysses Solar Wind Ion Composition Spectrometer. In this study, the O(+7)/O(+6) ratio is used to group silicon counts accumulated over a two month period. Results on Si charge state distributions, relative Si/O abundances, and associated proton kinetic temperature and speed distributions are presented.

Galvin, A. B.; Ipavich, F. M.; Gloeckler, G.; Von Steiger, R.; Wilken, B.

1992-01-01

439

WSA-ENLIL Cone Extension: Improving Solar Wind Forcing Parameter Estimates at Mercury  

NASA Astrophysics Data System (ADS)

Understanding magnetospheric and exospheric processes at Mercury requires knowledge of solar wind 'forcing' conditions. This forcing includes both the background quasi-steady solar wind and the effects of transient solar eruptions, most notably coronal mass ejections (CMEs). The departures from background solar wind due to CMEs often correspond to more than an order of magnitude greater ram pressure and dynamo electric field applied to the magnetosphere. Observations from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft were previously combined with the Wang-Sheeley-Arge (WSA)-ENLIL solar-wind modeling tool to calculate such solar wind forcing parameters as the interplanetary magnetic field (IMF) strength (B); solar wind velocity (V), density (n), and temperature (T); ram pressure (~nV2); cross-magnetosphere electric field (V×B); and Alfvén Mach number (MA). Previous efforts relied only on the background solar wind, however, and constituted an incomplete model of solar wind forcing given that the effects of transient solar phenomena were not included. The WSA-ENLIL model with the Cone extension permits inclusion of the effects of CMEs and related transient solar phenomena, and thus characterization of the effect of strong solar wind perturbations on the Mercury system. The Cone extension utilizes the heliocentric location, velocity, and radial size of a CME to propagate it through the inner solar system under the assumption of constant angular and radial velocity. This more complete approach provides a firmer basis with which to study magnetospheric and exospheric processes at Mercury and thereby better understand how the solar wind drives the Mercury system. Comparisons of WSA-ENLIL-Cone model outputs with measured properties from the MESSENGER Magnetometer (MAG), Neutron Spectrometer (NS), and Energetic Particle and Plasma Spectrometer (EPPS) permit quantification of the improvement in solar wind/IMF specification, particularly during times of the largest solar eruptive events over the period 2011-2013.

Dewey, R. M.; Baker, D. N.; Anderson, B. J.; Benna, M.; Johnson, C. L.; Korth, H.; Gershman, D. J.; Ho, G. C.; McClintock, W. E.; Odstrcil, D.; Raines, J. M.; Schriver, D.; Slavin, J. A.; Solomon, S. C.; Winslow, R. M.; Zurbuchen, T.

2013-12-01

440

Radial variation of the solar wind speed between 1 and 15 AU  

NASA Technical Reports Server (NTRS)

Pioneer 10 and 11 solar wind speeds measured between 1.4 and 15.2 AU are compared with those of IMP 6, 7, and 8 measured at 1 AU for 90-day intervals centered on six solar radial alignments between 1973 and 1978. The time profile of the solar wind speed undergoes change as the distance from the sun increases, which is due to interaction of adjacent solar wind streams. Speed variations are smaller at greater radial distance and both the highest and lowest speeds disappear as radial distance increases. For periods with extremely high speed solar wind streams, the mean solar wind speed decreases as the distance from the sun increases, which must be due to the disappearance of the highest speeds of the streams with increasing distance. It is concluded that at distances from the sun greater than 30-40 AU, the solar wind behavior may closely resemble that of a radially expanding constant speed plasma.

Collard, H. R.; Mihalov, J. D.; Wolfe, J. H.

1982-01-01

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