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1

THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

A new analysis of magnetic and concurrent plasma data collected from the ; space probes Pionecr 5, Explorer 10, and Mariner 2 yields a new model of the ; interplanetary magnetic field. It is hypothesized that the observed ; interplanetary field F\\/sub i\\/ is due to motion of the magnetometer relative to a ; negatively charged rotating sun from which

V. A. BAILEY

1963-01-01

2

Interplanetary Magnetic Field Lines  

NSDL National Science Digital Library

This web page provides information and a graphical exercise for students regarding the interaction between magnetic field lines and a plasma. The activity involves tracing a typical interplanetary magnetic field line, dragged out of a location on the Sun by the radial flow of the solar wind. This illustrates the way magnetic field lines are "frozen to the plasma" and the wrapping of field lines due to the rotation of the sun. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.

Stern, David

2005-04-27

3

Interplanetary magnetic holes: Theory  

NASA Technical Reports Server (NTRS)

Magnetic holes in the interplanetary medium are explained as stationary, non-propagating, equilibrium structures in which there are field-aligned enhancements of the plasma density and/or temperature. Magnetic anti-holes are considered to be associated with depressions in the plasma pressure. In this model, the observed changes in the magnetic field intensity and direction are due to diamagnetic currents that are carried by ions which drift in a sheath as the result of gradients in the magnetic field and in the plasma pressure within the sheath. The thickness of the sheaths considered is approximately a few ion Larmor radii. An electric field is normal to the magnetic field in the sheath. Solutions of Vlasov's equation and Maxwell's equations are presented which account for several types of magnetic holes, including null-sheets, that were observed.

Burlaga, L. F.; Lemaire, J. F.

1978-01-01

4

The interplanetary magnetic field. Solar origin and terrestrial effects  

Microsoft Academic Search

Many observations related to the large-scale structure of the interplanetary magnetic field, its solar origin and terrestrial effects are discussed. During the period observed by spacecraft the interplanetary field was dominated by a sector structure corotating with the sun in which the field is predominantly away from the sun (on the average in the Archimedes spiral direction) for several days

John M. Wilcox

1968-01-01

5

Prediction of the interplanetary magnetic field strength  

Microsoft Academic Search

A new model of the coronal and interplanetary magnetic field can predict both the interplanetary magnetic field strength and its polarity from measurements of the photospheric magnetic field. The model includes the effects of the large-scale horizontal electric currents flowing in the inner corona, of the warped heliospheric current sheet in the upper corona, and of volume currents flowing in

Xuepu Zhao; J. Todd Hoeksema

1995-01-01

6

Magnetic helicity analysis of an interplanetary twisted flux tube  

E-print Network

, and magnetic clouds; 2134 Interplanetary Physics: Interplanetary magnetic fields; 7524 Solar Physics, Astrophysics, and Astronomy: Magnetic fields; 7513 Solar Physics, Astrophysics, and Astronomy: Coronal mass, which are characterized by enhanced magnetic field strength with respect to ambient values, a large

Dasso, Sergio

7

Interplanetary stream magnetism - Kinematic effects  

NASA Technical Reports Server (NTRS)

The particle density and the magnetic-field intensity and direction are calculated for volume elements of the solar wind as a function of the initial magnetic-field direction and the initial speed gradient. It is assumed that the velocity is constant and radial. These assumptions are approximately valid between about 0.1 and 1.0 AU for many streams. Time profiles of the particle density, field intensity, and velocity are calculated for corotating streams, neglecting effects of pressure gradients. The compression and rarefaction of the magnetic field depend sensitively on the initial field direction. By averaging over a typical stream, it is found that the average radial field intensity is inversely proportional to the square of the heliocentric distance, whereas the average intensity in the direction of the planets' motion does not vary in a simple way, consistent with deep space observations. Changes of field direction may be very large, depending on the initial angle; but when the initial angle at 0.1 AU is such that the base of the field line corotates with the sun, the spiral angle is the preferred direction at 1 AU. The theory is also applicable to nonstationary flows.

Burlaga, L. F.; Barouch, E.

1976-01-01

8

Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations  

NASA Technical Reports Server (NTRS)

In order to infer the interplanetary sector polarity from polar geomagnetic field diurnal variations, measurements were carried out at Godhavn and Thule (Denmark) Geomagnetic Observatories. The inferred interplanetary sector polarity was compared with the polarity observed at the same time by Explorer 33 and 35 magnetometers. It is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar cap geomagnetic fields.

Friis-Christensen, E.; Lassen, K.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

1971-01-01

9

INFLUENCE OF INTERPLANETARY MAGNETIC FIELD AND PLASMA ON GEOMAGNETIC ACTIVITY DURING QUIET-SUN CONDITIONS  

Microsoft Academic Search

Observations by the IMP 1 satellite of the interplanetary magnetic field and plasma have been compared with the 3-hour geomagnetic activity index K. The average Kis approximately a linear function of the interplanetary field magnitude B in gammas (i -- (0.33 =k 0.02)B =k 0.2). It appears significant that this relation betweenand field magnitude passes through the origin, whereas the

John M. Wilcox; Kenneth H. Schatten; Norman F. Ness

1967-01-01

10

Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations  

NASA Technical Reports Server (NTRS)

With the use of a prediction technique it is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar geomagnetic field.

Eriss-Christensen, E.; Lassen, K.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

1971-01-01

11

Angular distribution of discontinuity normals of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

High time resolved (6 s) magnetic field data from the Helios-1 and Ulysses spacecrafts were used to investigate MHD discontinuities in the heliosphere. The identification of discontinuities was based on the rotation of the field vectors relative to the distance to the plasma in which the vectors were supposed to be frozen. In order to obtain the real thickness of the discontinuity transition region, the surface normal of discontinuities were calculated by both the minimum variance and cross-product methods. Current work We found an anisotropy in the angular distribution of the discontinuity surface normals in the heliosphere where the average interplanetary magnetic field is close to radial. It is an indirect evidence that most of the discontinuities are tangential rather than rotational ones. This result is also supported by the fact that the Minimum Variance and Cross-Product methods gave similar results for the determination of the surface normals.

Lukács, K.; Erd?s, G.

2013-11-01

12

Heliocentric distance dependence of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations were observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions. Magnetic field variations near the sun are propagated to greater heliocentric distances, also contributing to the observed variablity of the IMF. Temporal variations on a time-scale comparable to or less than the corotation period complicate attempts to deduce radial gradients of the field and its fluctuations from the various observations. However, recent measurements inward to 0.46 AU and outward to 5 AU suggest that the radial component of the field on average decreases approximately as r to the minus second power, while the azimuthal component decreases more rapidly than the r to the minum first power dependence predicted by simple theory. This, and other observations, are discussed.

Behannon, K. W.

1977-01-01

13

Statistical maps of geomagnetic perturbations as a function of the interplanetary magnetic field  

Microsoft Academic Search

Mappings of geomagnetic perturbations are shown for different combinations of the solar wind velocity, interplanetary magnetic field (IMF), and dipole tilt angle (season). Average maps were derived separately for the northward, eastward, and vertical (downward) components of the geomagnetic disturbances, using spherical cap harmonics in least error fits of sorted measurements. The source data are obtained from 104 ground-based magnetometer

D. R. Weimer; C. R. Clauer; M. J. Engebretson; T. L. Hansen; H. Gleisner; I. Mann; K. Yumoto

2010-01-01

14

Response of the Geomagnetic Activity Index K p to the Interplanetary Magnetic Field  

Microsoft Academic Search

latter half of 1965 have been compared with the 3-hour Kindex. The results are consistent with those obtained by IMP I during three solar rotations in the winter of 1963-1964, indicat- ing a stability in the response of geomagnetic activity during these years near solar activity minimum. On the average an interplanetary magnetic field with a southward component is generally

Kenneth H. Schatten; John M. Wilcox

1967-01-01

15

The overall configuration of the interplanetary magnetic field upstream of Saturn as revealed by Cassini observations  

Microsoft Academic Search

The Cassini spacecraft approached Saturn during the declining phase of the solar cycle, at a time when the heliosphere was highly structured by compressions and rarefactions associated with corotating interaction regions (CIRs). We examine in detail the hourly averaged interplanetary magnetic field (IMF) data prior to Saturn Orbit Insertion and during one subsequent orbit of Cassini closer to solar minimum,

C. M. Jackman; R. J. Forsyth; M. K. Dougherty

2008-01-01

16

The spiral interplanetary magnetic field: A polarity and sunspot cycle variation  

NASA Technical Reports Server (NTRS)

Spacecraft observations near the earth of the yearly average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field. The angle between the average field direction when the field polarity was away from the sun and the average direction for toward polarity was 168 deg, rather than 180 deg. This effect appears to have a sunspot cycle variation.

Svalgaard, L.; Wilcox, J. M.

1974-01-01

17

The spiral interplanetary magnetic field - A polarity and sunspot cycle variation  

NASA Technical Reports Server (NTRS)

Spacecraft observations near the earth of the average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field of Parker's classical description. The included angle between the average field direction when the field polarity was away from the sun and the average direction when the field polarity was toward the sun was 168 deg, rather than 180 deg as predicted by Parker. This effect appears to have a sunspot cycle variation.

Svalgaard, L.; Wilcox, J. M.

1974-01-01

18

The role of coronal mass ejections and interplanetary shocks in interplanetary magnetic field statistics and solar magnetic flux ejection  

Microsoft Academic Search

We examine the role of coronal mass ejections (CMEs) and interplan- etary shocks in modifying the large-scale winding of the interplanetary magnetic field (IMF) by extracting CME and shock observations from the ISEE 3 data set and analyzing periods of the disturbed and undisturbed solar wind separately. We use the full ISEE 3 data set representing the entire L1 mission

Charles W. Smith; John L. Phillips

1997-01-01

19

The extension of solar magnetic fields into interplanetary space  

SciTech Connect

The flow of coronal plasma into interplanetary space results in outward transport of the solar magnetic field. The prevailing open'' interplanetary magnetic field is rooted in the corona and wraps up into a spiral due to the rotation of the Sun. This simple configuration, however, is disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from the solar corona into interplanetary space. Observations of CMEs at 1 AU reveal electron signatures indicating a closed magnetic topology, postulated to be: (1) magnetic bottles,'' tied to the corona at both ends; (2) plasmoids that are completely disconnected from the Sun; or (3) flux ropes which have topologies intermediate between (1) and (2). With either the magnetic-bottle or flux rope hypothesis, the inward and outward flux at 1 AU should increase indefinitely as CMEs continue to erupt. Using a new techniques to calculate the 2-D flux through 1 AU from single spacecraft measurements, we show that while there is a solar cycle variation to the magnetic flux, it clearly does not grow without bound. This suggests that either CMEs are closed plasmoids which add to no new flux to the interplanetary medium, or that the opening of new flux by CMEs is balanced via reconnection elsewhere in the corona. We suggest that the this latter process may be dominant and describe observation from the Solar Maximum Mission coronagraph which are consistent with reconnection above helmet streamers in the corona. Such disconnections would serve to return closed field arches to the Sun and release open. U-shaped structures into the solar wind. Coronal disconnections appear in some cases to be triggered by pressure pulses caused by CME eruption elsewhere, suggesting a dynamic flux-balance process. We describe a class of solar wind structures, called heat flux dropouts, in which the solar wind electron heat flux, driven by magnetic connection to the hot corona, is absent or greatly reduced.

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

1991-01-01

20

COLLIMATION OF COSMIC RAYS BY THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

a portion of the cosmic-ray and magnetic data observed during one of these flare events and lo demonstrate specific particle guidance properties of the interplanetary magnetic field. The data were obtained at a time when the spacecraft was 2.8 X 106 km from earth and at a sun-earth probe angle of 90 ø east of the sun and arc, therefore,

K. G. McCracken; N. F. Ness

1966-01-01

21

On the limitations of geomagnetic measures of interplanetary magnetic polarity  

NASA Technical Reports Server (NTRS)

The maximum attainable accuracy in inferring the interplanetary magnetic polarity from polar cap magnetograms is about 88%. This is achieved in practice, when high-latitude polar cap stations are used during local summer months, and the signature in the ground records is strong. An attempt by Svalgaard (1972) to use this effect to infer an index of interplanetary magnetic polarity back to 1926 has not been so successful. Furthermore, some of the properties of the index have changed with time. Prior to 1963, the inferred polarities are strongly dependent on geomagnetic activity, while after this time they are not. Thus, this index should not be used to separate solar-magnetic from solar-activity effects prior to 1963.

Russell, C. T.; Rosenberg, R. L.

1974-01-01

22

Study of interplanetary magnetic field with Ground State Alignment  

NASA Astrophysics Data System (ADS)

We demonstrate a new way of studying interplanetary magnetic field—Ground State Alignment (GSA). Instead of sending thousands of space probes, GSA allows magnetic mapping with any ground telescope facilities equipped with spectropolarimeter. The polarization of spectral lines that are pumped by the anisotropic radiation from the Sun is influenced by the magnetic realignment, which happens for magnetic field (<1 G). As a result, the linear polarization becomes an excellent tracer of the embedded magnetic field. The method is illustrated by our synthetic observations of the Jupiter's Io and comet Halley. Polarization at each point was constructed according to the local magnetic field detected by spacecrafts. Both spatial and temporal variations of turbulent magnetic field can be traced with this technique as well. The influence of magnetic field on the polarization of scattered light is discussed in detail. For remote regions like the IBEX ribbons discovered at the boundary of interstellar medium, GSA provides a unique diagnostics of magnetic field.

Shangguan, Jinyi; Yan, Huirong

2013-01-01

23

The interplanetary magnetic field from a time-dependent solar magnetic field  

Microsoft Academic Search

Effects of the time dependence of the sun's magnetic field on the interplanetary field in the solar wind are considered. General expressions for the interplanetary field are developed under the assumptions that the radial component of the sun's field at some reference surface can be described in terms of spherical harmonics with coefficients which are functions of time represented by

P. J. Coleman Jr.

1976-01-01

24

The interplanetary magnetic field from a time-dependent solar magnetic field  

Microsoft Academic Search

Effects of the time dependence of the sun's magnetic field upon the interplanetary field in the solar wind are considered. General expressions for the interplanetary field are developed under the assumptions that the radial component of the sun's field at some reference surface râ can be described in terms of spherical harmonics with coefficients which are functions of time represented

P. J. Jr

1976-01-01

25

Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides  

E-print Network

the interplanetary magnetic field (IMF), its radial component, and the open solar magnetic flux using the solar the strength of the IMF, its radial component, the solar open magnetic flux, and the solar wind speed. To dateInterplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides F

Wehrli, Bernhard

26

Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9.5 AU  

NASA Technical Reports Server (NTRS)

The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.

Burlaga, L. F.; Klein, L. W.; Lepping, R. P.; Behannon, K. W.

1984-01-01

27

Ground state alignment as a tracer of interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We demonstrate a new way of studying interplanetary magnetic field -- spectropolarimetry based on ground state alignment. Ground state alignment is a new promising way of sub-gausian magnetic fields in radiation-dominated environment. The polarization of spectral lines that are pumped by the anisotropic radiation from the sun is influenced by the magnetic alignment, which happens for sub-gausian magnetic field. As a result, the linear polarization becomes an excellent tracer of the embedded magnetic field. The method is illustrated by our synthetic obser- vation of the Jupiter's Io and comet Halley. A uniform density distribution of Na was considered and polar- ization at each point was then constructed. Both spa- tial and temporal variations of turbulent magnetic field can be traced with this technique as well. Instead of sending thousands of space probes, ground state alignment allows magnetic mapping with any ground telescope facilities equipped with spectrometer and polarimeter. For remote regions like the the boundary of interstellar medium, ground state alignment provides a unique diagnostics of magnetic field, which is crucial for understanding the physical processes such as the IBEX ribbons.

Yan, H.

2012-12-01

28

Critical component of the interplanetary magnetic field responsible for large geomagnetic effects in the polar cap  

NASA Technical Reports Server (NTRS)

An observed influence is studied of the interplanetary magnetic sector structure on the geomagnetic variations in the polar cap which appears to be due to the component of the interplanetary magnetic field near the ecliptic perpendicular to the earth-sun direction. It is suggested that the observed effect on the ground originates in the front of the magnetosphere.

Friis-Christensen, E.; Lassen, K.; Wilhjelm, J.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

1972-01-01

29

Interplanetary magnetic field control of high-latitude electric fields and currents determined from Greenland magnetometer data  

Microsoft Academic Search

To determine the effects of the interplanetary magnetic field (IMF) on the electric potential as well as on ionospheric and field-aligned currents, a recently available numerical algorithm is applied to an empirical model of high-latitude magnetic perturbations, parameterized in terms of the B\\/sub y\\/ and B\\/sub z\\/ components of the IMF. The empirical model is derived from 20-min average magnetometer

E. Friis-Christensen; Y. Kamide; A. D. Richmond; S. Matsushita

1985-01-01

30

Three-dimensional interplanetary stream magnetism and energetic particle motion  

NASA Technical Reports Server (NTRS)

Cosmic rays interact with mesoscale configurations of the interplanetary magnetic field. A technique is presented for calculating such configurations in the inner solar system, which are due to streams and source conditions near the sun, and maps of magnetic field are constructed for some plausible stream and source conditions. One effect of these mesoscale configurations on galactic cosmic rays is shown to be an out-of-the-ecliptic gradient drift sufficient to explain Forbush decreases. The effects on solar energetic particles include small polar drifts due to the field gradients and a possibly large modification of the time-intensity profiles and anisotropy characteristics due to the formation of mirror configurations in space. If a diffusion model is applicable to solar particles, the true diffusion coefficient will be masked by the effects of streams. A conceptual model which incorporates these ideas and those of several other models is presented.

Barouch, E.; Burlaga, L. F.

1976-01-01

31

Repetitive substorms caused by Alfvenic waves of the interplanetary magnetic field during high-speed solar wind streams  

E-print Network

), Repetitive substorms caused by Alfve´nic waves of the interplanetary magnetic field during high- speed solar the declining phase of the solar cycle 20, i.e., 1973­ 1975, to determine the interplanetary magnetic field (IMFRepetitive substorms caused by Alfve´nic waves of the interplanetary magnetic field during high

Lyons, Larry

32

Inferring interplanetary magnetic field polarities from geomagnetic variations  

NASA Astrophysics Data System (ADS)

In this paper, we propose a modified procedure to infer the interplanetary magnetic field (IMF) polarities from geomagnetic observations. It allows to identify the polarity back to 1905. As previous techniques it is based on the well-known Svalgaard-Mansurov effect. We have improved the quality and accuracy of polarity inference compared with the previous results of Svalgaard (1975) and Vennerstroem et al. (2001) by adding new geomagnetic stations and extracting carefully diurnal curve. The data demonstrates an excess of one of the two IMF sectors within equinoxes (Rosenberg-Coleman rule) evidencing polar field reversals at least for the last eight solar cycles. We also found a predominance of the two-sector structure in late of descending phase of solar cycle 16.

Vokhmyanin, M. V.; Ponyavin, D. I.

2012-06-01

33

Magnetic shielding of interplanetary spacecraft against solar flare radiation  

NASA Technical Reports Server (NTRS)

The ultimate objective of this work is to design, build, and fly a dual-purpose, piggyback payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field (1) to protect spacecraft against solar flare protons, (2) to produce a thrust of sufficient magnitude to stabilize low satellite orbits against orbital decay from atmospheric drag, and (3) to test the magsail concept. These all appear to be capable of being tested using the same deployed high temperature superconducting coil. In certain orbits, high temperature superconducting wire, which has now been developed to the point where silver-sheathed high T sub c wires one mm in diameter are commercially available, can be used to produce the magnetic moments required for shielding without requiring any mechanical cooling system. The potential benefits of this concept apply directly to both earth-orbital and interplanetary missions. The usefulness of a protective shield for manned missions needs scarcely to be emphasized. Similarly, the usefulness of increasing orbit perigee without expenditure of propellant is obvious. This payload would be a first step in assessing the true potential of large volume magnetic fields in the US space program. The objective of this design research is to develop an innovative, prototype deployed high temperature superconducting coil (DHTSC) system.

Cocks, Franklin H.; Watkins, Seth

1993-01-01

34

The Interplanetary Magnetic Field and Magnetospheric Current Systems  

NASA Technical Reports Server (NTRS)

We have performed systematic global magnetohydrodynamic (MHD) simulation studies driven by an idealized time series of solar wind parameters to establish basic cause and effect relationships between the solar wind variations and the ionosphere parameters. We studied six cases in which the interplanetary magnetic field (IMF) rotated from southward to northward in one minute. In three cases (cases A, B, and C) we ran five hours of southward IMF with Beta(sub Zeta) = 5 nT, followed by five hours of northward IMF with Beta(sub Zeta) = 5 nT. In the other three cases (cases D, E, and F) the magnetic field magnitude was increased to 10 nT. The solar wind parameters were: For cases A and D a density of 5 cm(exp -3), a thermal pressure of 3.3 nPa, and a solar wind speed 375 km/s, for cases B and E a density of 10 cm(exp -3), a thermal pressure of 9.9 nPa, and a solar wind speed 420 km/s, while for cases C and F a density of 15 cm(exp -3), a thermal pressure of 14.9 nPa, and a solar wind speed of 600 km/s.

El-Alaoui, Mostafa

2003-01-01

35

The Influence of the Interplanetary Magnetic Field (IMF) on Atmospheric Escape at Mars  

NASA Astrophysics Data System (ADS)

We present a study on the response of Mars’ atmosphere to changes in the interplanetary magnetic field (IMF) configuration, specifically with respect to the atmospheric escape rate via pick up ions and upcoming MAVEN observations.

Curry, S. M.; Luhmann, J. G.; Ma, Y.; Dong, C. F.; Brain, D. A.

2014-07-01

36

The Bastille Day Magnetic Clouds and Upstream Shocks: Near Earth Interplanetary Observations  

NASA Technical Reports Server (NTRS)

The energetic charged particle, interplanetary magnetic field, and plasma characteristics of the 'Bastille Day' shock and ejecta/magnetic cloud events at 1 AU occurring over the days 14-16 July 2000 are described. Profiles of MeV (WIND/LEMT) energetic ions help to organize the overall sequence of events from the solar source to 1 AU. Stressed are analyses of an outstanding magnetic cloud (MC2) starting late on 15 July and its upstream shock about 4 hours earlier in WIND magnetic field and plasma data. Also analyzed is a less certain, but likely, magnetic cloud (MC1) occurring early on 15 July; this was separated from MC2 by its upstream shock and many heliospheric current sheet (HCS) crossings. Other HCS crossings occurred throughout the 3-day period. Overall this dramatic series of interplanetary events caused a large multi-phase magnetic storm with min Dst lower than -300 nT. The very fast solar wind speed (greater than or equal to 1100 km/s) in and around the front of MC2 (for near average densities) was responsible for a very high solar wind ram pressure driving in the front of the magnetosphere to geocentric distances estimated to be as low as approx. 5 R(sub E), much lower than the geosynchronous orbit radius. This was consistent with magnetic field observations from two GOES satellites which indicated they were in the magnetosheath for extended times. A static force free field model is used to fit the two magnetic cloud profiles providing estimates of the clouds' physical and geometrical properties. MC2 was much larger than MCI, but their axes were nearly antiparallel, and their magnetic fields had the same left-handed helicity. MC2's axis and its upstream shock normal were very close to being perpendicular to each other, as might be expected if the cloud were driving the shock at the time of observation. The estimated axial magnetic flux carried by MC2 was 52 x 10(exp 20) Mx, which is about 5 times the typical magnetic flux estimated for other magnetic clouds in the WIND data over its first 4 years and is 17 times the flux of MC1. This large flux is due to both the strong axially-directed field of MC2 (46.8 nT on the axis) and the large radius (R(sub 0) = 0.189 AU) of the flux tube. MC2's average speed is consistent with the expected transit time from a halo-CME to which it is apparently related.

Lepping, R. P.; Berdichevsky, D. B.; Burlaga, L. F.; Lazarus, A. J.; Kasper, J.; Desch, M. D.; Wu, C.-C.; Reames, D. V.; Singer, H. J.; Singer, H. J.; Vondrak, Richard R. (Technical Monitor)

2001-01-01

37

Experimental observations of the interplanetary magnetic field distribution in the inner heliosphere: controversial points  

NASA Astrophysics Data System (ADS)

Interplanetary magnetic field (IMF) deviations from a Parker spiral are very often observed in the heliosphere at different distances from the Sun. Commonly, it is supposed that the IMF in the inner heliosphere corresponds to the Parker theory as a whole, but there is some turbulent component that impacts a full picture of the IMF spatial and temporal distribution and damages it. Meanwhile, the analysis of multipoint in-ecliptic IMF measurements from 0.23 AU to 5 AU shows that the radial IMF component in the inner heliosphere corresponds neither r-2 law nor the helicity assumption even under rough average. The next problematic point is an explanation of observational results on the in-ecliptic IMF distribution shape at different AU. It is shown that a bimodal (two-humped) view of Br, RTN (or Bx, By, GSE) distribution, well-known at 1 AU, is most brightly expressed at low heliolatitudes at 0.7-2 AU, but it disappears with an increasing heliocentric distance. The in-ecliptic IMF distribution shape becomes perfectly Gaussian-like at 3-4 AU. Such behaviour of the in-ecliptic IMF can not be explained by any theory of the IMF extension in space. Therefore, experimental results, accumulated for the space era, demonstrates the barest necessity of the 3-D interplanetary magnetic field picture revisiting, looking for new theories of plasma and IMF expansion from the Sun, as well as further development of new models of the inner heliosphere.

Khabarova, O. V.; Obridko, V. N.

2012-04-01

38

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

39

Criteria of interplanetary parameters causing intense magnetic storms (Dst less than -100nT)  

NASA Technical Reports Server (NTRS)

Ten intense storms occurred during the 500 days of August 16, 1978 to December 28, 1979. From the analysis of ISEE-3 field and plasma data, it is found that the interplanetary cause of these storms are long-duration, large and negative IMF B sub Z events, associated with interplanetary duskward-electric fields greater than 5 mV/m. Because a one-to-one relationship was found between these interplanetary events and intense storms, it is suggested that these criteria can, in the future, be used as predictors of intense storms by an interplanetary monitor such as ISEE-3. These B sub Z events are found to occur in association with large amplitudes of the IMF magnitude within two days after the onset of either high-speed solar wind streams or of solar wind density enhancement events, giving important clues to their interplanetary origin. Some obvious possibilities will be discussed. The close proximity of B sub Z events and magnetic storms to the onset of high speed streams or density enhancement events is in sharp contrast to interplanetary Alfven waves and HILDCAA events previously reported, and thus the two interplanetary features corresponding geomagnetic responses can be thought of as being complementary in nature. An examination of opposite polarity B sub Z events with the same criteria show that their occurrence is similar both in number as well as in their relationship to interplanetary disturbances, and that they lead to low levels of geomagnetic activity.

Gonzalez, Walter D.; Tsurutani, Bruce T.

1987-01-01

40

Interplanetary magnetic field as a detector of turbulence in the inner heliosphere  

NASA Astrophysics Data System (ADS)

Analysis of the interplanetary magnetic field (IMF) behavior at different scales may give a key for understanding of turbulence spatial evolution in the heliosphere. It has been known that the solar wind plasma becomes more and more turbulent with heliocentric distance. Recent multi-spacecraft investigations of the large-scale IMF [1] show unexpectedly fast lost of the regular sector structure of the solar wind in the inner heliosphere. In the ecliptic plane, it seems to be broken at 3-4 AU, much closer to the Sun than the Parker spiral gets perpendicular to the sunward direction. At the same time, the high-latitude solar wind remains more structured at the same heliocentric distances [2]. This fact may bear evidence of radial increase of turbulence and intermittency in the solar wind due to magnetic reconnection. The magnetic reconnection recurrently occurs at the large-scale heliospheric current sheet (HCS) as well as at smaller-scale current sheets during the solar wind expansion [3]. As a result, a significant part of the heliosphere is filled with secondary current sheets as well as with waves and accelerated particles in some vicinity of the HCS. Under averaging, it looks as a radial increase of turbulence, especially in low latitudes. It also can be considered as one of the main causes of the break of the expected IMF radial dependence law [1, 2]. Results of the consequent multi-spacecraft analysis of plasma and magnetic filed turbulence characteristics at different heliocentric distances and heliolatitudes will be discussed. 1. O. Khabarova, V. Obridko, Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere, 2012, Astrophysical Journal, 761, 2, 82, doi:10.1088/0004-637X/761/2/82, http://arxiv.org/pdf/1204.6672v2.pdf 2. O.V. Khabarova, The interplanetary magnetic field: radial and latitudinal dependences, Astronomy Reports, 2013, 57, 11, http://arxiv.org/ftp/arxiv/papers/1305/1305.1204.pdf 3. V. Zharkova, O. Khabarova, Particle Acceleration in the Reconnecting Heliospheric Current Sheet: Solar Wind Data Versus 3D PIC Simulations, Astrophysical Journal, 2012, V.752, 1, 35, doi:10.1088/0004-637X/752/1/35

Khabarova, O.

2013-12-01

41

PUZZLES OF THE INTERPLANETARY MAGNETIC FIELD IN THE INNER HELIOSPHERE  

SciTech Connect

Deviations of the interplanetary magnetic field (IMF) from Parker's model are frequently observed in the heliosphere at different distances r from the Sun. Usually, it is supposed that the IMF behavior corresponds to Parker's model overall, but there is some turbulent component that impacts and disrupts the full picture of the IMF spatial and temporal distribution. However, the analysis of multi-spacecraft in-ecliptic IMF measurements from 0.29 AU to 5 AU shows that the IMF radial evolution is rather far from expected. The radial IMF component decreases with the adiabatic power index (|B{sub r} | {proportional_to} r {sup -5/3}), the tangential component |B{sub r}| {proportional_to} r {sup -1}, and the IMF strength B {proportional_to} r {sup -1.4}. This means that the IMF is not completely frozen in the solar wind. It is possible that turbulent processes in the inner heliosphere significantly influence the IMF expansion. This is confirmed by the analysis of the B{sub r} distribution's radial evolution. B{sub r} has a well-known bimodal histogram only at 0.7-2.0 AU. The bimodality effect gradually disappears from 1 AU to 4 AU, and B{sub r} becomes quasi-normally distributed at 3-4 AU (which is a sign of rapid vanishing of the stable sector structure with heliocentric distance). We consider a quasi-continuous magnetic reconnection, occurring both at the heliospheric current sheet and at local current sheets inside the IMF sectors, to be a key process responsible for the solar wind turbulization with heliocentric distance as well as for the breakdown of the ''frozen-in IMF'' law.

Khabarova, Olga; Obridko, Vladimir, E-mail: habarova@izmiran.ru [Heliophysical Laboratory, Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation RAS (IZMIRAN), Troitsk, Moscow Region 142190 (Russian Federation)

2012-12-20

42

Interplanetary medium data book, appendix  

NASA Technical Reports Server (NTRS)

Computer generated listings of hourly average interplanetary plasma and magnetic field parameters are given. Parameters include proton temperature, proton density, bulk speed, an identifier of the source of the plasma data for the hour, average magnetic field magnitude and cartesian components of the magnetic field. Also included are longitude and latitude angles of the vector made up of the average field components, a vector standard deviation, and an identifier of the source of magnetic field data.

King, J. H.

1977-01-01

43

Magnetic loop behind an interplanetary shock - Voyager, Helios, and IMP 8 observations  

Microsoft Academic Search

The flow behind an interplanetary shock was analyzed through the use of magnetic field and plasma data from five spacecraft, with emphasis on the magnetic cloud identified by a characteristic variation of the latitude angle of the magnetic field. The size of the cloud was found to be about 0.5 AU in radial extent and greater than 30 deg in

L. Burlaga; E. Sittler; F. Mariani; R. Schwenn

1981-01-01

44

Characteristic magnetic field and speed properties of interplanetary coronal mass ejections and their  

E-print Network

coordinates, the product of the solar wind radial flow speed and the southward magnetic field strength) plays ability to forecast the 1 AU magnetic field strengths resulting from interplanetary CMEs (ICMEs). In this study we investigate the relation between the characteristic magnetic field strengths and speeds of both

California at Berkeley, University of

45

The interplanetary magnetic field: Radial and latitudinal dependences  

NASA Astrophysics Data System (ADS)

Results of the analysis of spacecraft measurements at 1-5.4 AU are presented within the scope of the large-scale interplanetary magnetic field (IMF) structure investigation. The work is focused on revealing of the radial IMF component ( B r ) variations with heliocentric distance and latitude as seen by Ulysses. It was found out that | B r | decreases as ˜ r -5/3 in the ecliptic plane vicinity (±10° of latitude), which is consistent with the previous results obtained on the basis of the analysis of in-ecliptic measurements from five spacecraft. The difference between the experimentally found ( r -5/3) and commonly used ( r -2) radial dependence of B r may lead to mistakes in the IMF recalculations from point to point in the heliosphere. This can be one of the main sources of the "magnetic flux excess" effect, which is exceeding of the distantly measured magnetic flux over the values obtained through the measurements at the Earth orbit. It is shown that the radial IMF component can be considered as independent of heliolatitude in a rough approximation only. More detailed analysis demonstrates an expressed | B r | (as well as the IMF strength) increase in the latitudinal vicinity of ±30° relative to the ecliptic plane. Also, a slight increase of the both parameters is observed in the polar solar wind. The comparison of the B r distributions confirms that, at the same radial distance, B r values are higher at low than at high latitudes. The analysis of the latitudinal and radial dependences of the B r distribution's bimodality is performed. The B r bimodality is more expressed at high than in the low-latitude solar wind, and it is observed at greater radial distances at high latitudes. The investigation has not revealed any dependence between B r and the solar wind speed V. The two-peak distribution of the solar wind speed as measured by Ulysses is a consequence of a strong latitudinal and solar cycle dependence of V. It is shown that the solar wind speed in high latitudes (above ±40°) anti-correlates with a solar activity: V is maximum during solar-cycle minima and minimum at the maximum of solar activity.

Khabarova, O. V.

2013-11-01

46

Sources of magnetic fields in recurrent interplanetary streams  

NASA Technical Reports Server (NTRS)

The sources of magnetic fields in recurrent streams were examined. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. Some of the magnetic fields and plasmas were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines are more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes ranged from 2G to 18G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 solar radii had a similar range and average, but in two cases the intensities were approximately three times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 solar radii, meandered between -45 deg and +45 deg latitude, and their inclination ranged from near zero to near ninety degrees.

Burlaga, L. F.; Behannon, K. W.; Hansen, S. F.; Pneuman, G. W.; Feldman, W. C.

1977-01-01

47

Interplanetary magnetic field control of Saturn's polar cusp aurora  

NASA Astrophysics Data System (ADS)

Dayside UV emissions in Saturn's polar ionosphere have been suggested to be the first observational evidence of the kronian "cusp" (Gérard et al., 2004). The emission has two distinct states. The first is a bright arc-like feature located in the pre-noon sector, and the second is a more diffuse "spot" of aurora which lies poleward of the general location of the main auroral oval, which may be related to different upstream interplanetary magnetic field (IMF) orientations. Here we take up the suggestion that these emissions correspond to the cusp. However, direct precipitation of electrons in the cusp regions is not capable of producing significant UV aurora. We have therefore investigated the possibility that the observed UV emissions are associated with reconnection occurring at the dayside magnetopause, possibly pulsed, akin to flux transfer events seen at the Earth. We devise a conceptual model of pulsed reconnection at the low-latitude dayside magnetopause for the case of northwards IMF which will give rise to pulsed twin-vortical flows in the magnetosphere and ionosphere in the vicinity of the open-closed field-line boundary, and hence to bi-polar field-aligned currents centred in the vortical flows. During intervals of high-latitude lobe reconnection for southward IMF, we also expect to have pulsed twin-vortical flows and corresponding bi-polar field-aligned currents. The vortical flows in this case, however, are displaced poleward of the open-closed field line boundary, and are reversed in sense, such that the field-aligned currents are also reversed. For both cases of northward and southward IMF we have also for the first time included the effects associated with the IMF By effect. We also include the modulation introduced by the structured nature of the solar wind and IMF at Saturn's orbit by developing "slow" and "fast" flow models corresponding to intermediate and high strength IMF respectively. We then consider the conditions under which the plasma populations appropriate to either sub-solar reconnection or high-latitude lobe reconnection can carry the currents indicated. We have estimated the field-aligned voltages required, the resulting precipitating particle energy fluxes, and the consequent auroral output. Overall our model of pulsed reconnection under conditions of northwards and southwards IMF, and for varying orientations of IMF By, is found to produce a range of UV emission intensities and geometries which is in good agreement with the data presented by Gérard et al. (2004). The recent HST-Cassini solar wind campaign provides a unique opportunity to test the theoretical ideas presented here.

Bunce, E. J.; Cowley, S. W. H.; Milan, S. E.

2005-06-01

48

DECLINE AND RECOVERY OF THE INTERPLANETARY MAGNETIC FIELD DURING THE PROTRACTED SOLAR MINIMUM  

SciTech Connect

The interplanetary magnetic field (IMF) is determined by the amount of solar magnetic flux that passes through the top of the solar corona into the heliosphere, and by the dynamical evolution of that flux. Recently, it has been argued that the total flux of the IMF evolves over the solar cycle due to a combination of flux that extends well outside of 1 AU and is associated with the solar wind, and additionally, transient flux associated with coronal mass ejections (CMEs). In addition to the CME eruption rate, there are three fundamental processes involving conversion of magnetic flux (from transient to wind-associated), disconnection, and interchange reconnection that control the levels of each form of magnetic flux in the interplanetary medium. This is distinct from some earlier models in which the wind-associated component remains steady across the solar cycle. We apply the model of Schwadron et al. that quantifies the sources, interchange, and losses of magnetic flux to 50 yr of interplanetary data as represented by the Omni2 data set using the sunspot number as a proxy for the CME eruption rate. We do justify the use of that proxy substitution. We find very good agreement between the predicted and observed interplanetary magnetic flux. In the absence of sufficient CME eruptions, the IMF falls on the timescale of ?6 yr. A key result is that rising toroidal flux resulting from CME eruption predates the increase in wind-associated IMF.

Smith, Charles W.; Schwadron, Nathan A. [Physics Department, Space Science Center, University of New Hampshire, Durham, New Hampshire (United States); DeForest, Craig E., E-mail: Charles.Smith@unh.edu, E-mail: N.Schwadron@unh.edu, E-mail: DeForest@Boulder.SwRI.edu [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado (United States)

2013-09-20

49

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.

50

Effect of Oblique Interplanetary Magnetic Field on Shape and Behavior of the Magnetosphere  

Microsoft Academic Search

The oblique angle made by the spiral interplanetary magnetic field with the radially expanding solar wind is shown to result in an easterly deflection of the solar wind as it traverses the standing hydromagnetic shock wave a few earth radii upstream of the mag- netosphere. A quantitative estimate of the deflection angle can be obtained from the plasma shock relations,

G. K. Walters

1964-01-01

51

POLAR-CAP ELECTRIC FIELD DISTRIBUTIONS RELATED TO THE INTERPLANETARY MAGNETIC FIELD DIRECTION  

Microsoft Academic Search

was shown that at auroral-belt latitudes in both hemispheres the electric field is consistently directed poleward in the midevening sector and equatorward in the midmorning sector (i.e., from dusk toward dawn), whereas the field at higher (polar cap) latitudes is consistently directed from dawn toward dusk. By consistently, one means independent of magnetic disturbance conditions, interplanetary field directions, and other

J. P. Heppner

1972-01-01

52

Statistical maps of geomagnetic perturbations as a function of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Mappings of geomagnetic perturbations are shown for different combinations of the solar wind velocity, interplanetary magnetic field (IMF), and dipole tilt angle (season). Average maps were derived separately for the northward, eastward, and vertical (downward) components of the geomagnetic disturbances, using spherical cap harmonics in least error fits of sorted measurements. The source data are obtained from 104 ground-based magnetometer stations in the Northern Hemisphere at geomagnetic latitudes over 40° during the years 1998 through 2001. Contour maps of statistical fits are shown along-side scatter plots of individual measurements in corrected geomagnetic apex coordinates. The patterns are consistent with previous mappings of ionospheric electric potential. Interestingly, the vertical component of the magnetic perturbations closely resembles maps of the overhead, field-aligned currents, including the Northward IMF configuration. The maximum and minimum values from the statistical mappings are graphed to show their changes as a function of southward IMF magnitude, solar wind velocity, and seasons. It is expected that this work will lead to better advance predictions of the geomagnetic perturbations that are based on real-time IMF measurements.

Weimer, D. R.; Clauer, C. R.; Engebretson, M. J.; Hansen, T. L.; Gleisner, H.; Mann, I.; Yumoto, K.

2010-10-01

53

Strong ionospheric field-aligned currents for radial interplanetary magnetic fields  

NASA Astrophysics Data System (ADS)

The present work has investigated the configuration of field-aligned currents (FACs) during a long period of radial interplanetary magnetic field (IMF) on 19 May 2002 by using high-resolution and precise vector magnetic field measurements of CHAMP satellite. During the interest period IMF By and Bz are weakly positive and Bx keeps pointing to the Earth for almost 10 h. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average. The cross polar cap potential calculated from Assimilative Mapping of Ionospheric Electrodynamics and derived from DMSP observations have average values of 10-20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the dayside and nightside. At the south pole FACs diminish in intensity to magnitudes of about 0.1 ?A/m2, the plasma convection maintains two-cell flow pattern, and the thermospheric density is quite low. However, there are obvious activities in the northern cusp region. One pair of FACs with a downward leg toward the pole and upward leg on the equatorward side emerge in the northern cusp region, exhibiting opposite polarity to FACs typical for duskward IMF orientation. An obvious sunward plasma flow channel persists during the whole period. These ionospheric features might be manifestations of an efficient magnetic reconnection process occurring in the northern magnetospheric flanks at high latitude. The enhanced ionospheric current systems might deposit large amount of Joule heating into the thermosphere. The air densities in the cusp region get enhanced and subsequently propagate equatorward on the dayside. Although geomagnetic indices during the radial IMF indicate low-level activity, the present study demonstrates that there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the northern polar cusp region.

Wang, Hui; Lühr, Hermann; Shue, Jih-Hong; Frey, Harald. U.; Kervalishvili, Guram; Huang, Tao; Cao, Xue; Pi, Gilbert; Ridley, Aaron J.

2014-05-01

54

Mie scattering of the interplanetary magnetic field by the whole moon  

NASA Technical Reports Server (NTRS)

It is known from the Apollo magnetometer experiments that significant electromagnetic induction takes place in the lunar interior. This induction is excited by fluctuations of the interplanetary magnetic field and is detected by the induced fields on the surface of the moon. These results are reviewed briefly and the formal properties of the theory are discussed. It is shown that the mathematical treatment parallels that for classical electromagnetic scattering. Further the wavelength spectrum of the fluctuations of the interplanetary magnetic field include scales consistent with the radius of the moon. The consequence is that the moon is excited in several modes. Quadrupole and possibly octupole magnetic multipoles are found in the data. The electric type radiation corresponding to transverse magnetic excitation appears suppressed and far below the detection threshold of the magnetometers.

Sonett, C. P.; Colburn, D. S.

1973-01-01

55

Inferring the interplanetary magnetic field by observing the polar geomagnetic field.  

NASA Technical Reports Server (NTRS)

Svalgaard (1968, 1972) and Mansurov (1969) have shown that it is possible to infer the polarity of the interplanetary magnetic field quite reliably from observations of the diurnal variation of polar geomagnetic fields. The effect is most prominent in the vertical component of geomagnetic observatories near the geomagnetic poles during several hours near noon. The interplanetary magnetic field observed with spacecraft near the earth is very similar to the mean solar magnetic field (i.e., the sun observed as though it were a star); thus the fact that observations of the polar geomagnetic field have existed without interruption since 1926 at the Danish Meteorological Institute station at Godhavn, Greenland, means that in effect the inferred solar magnetic field during five sunspot cycles is available for analysis.-

Wilcox, J. M.

1972-01-01

56

Magnetic field modulated dust streams from Jupiter in interplanetary space Alberto Flandes a,, Harald Kr uger b,c  

E-print Network

Magnetic field modulated dust streams from Jupiter in interplanetary space Alberto Flandes a Accepted 25 May 2011 Available online 16 June 2011 Keywords: Interplanetary dust Solar wind Jupiter Io a b s t r a c t High speed dust streams emanating from near Jupiter were first discovered by the Ulysses

Hamilton, Douglas P.

57

Magnetic fields of photosphere and interplanetary space: Imbalance between positive and negative polarities  

NASA Astrophysics Data System (ADS)

Photospheric magnetic fields are studied in this work on the basis of synoptic maps from the Kitt Peak Observatory (1976-2003) and WSO (1976-2012). The imbalance between positive and negative fluxes is considered for strong magnetic fields in the sunspot zone. The imbalance sign coincides with the polar field sign in the Northern hemisphere; it depends on both the phase of the 11-year cycle and the solar cycle parity. These features of variation in the magnetic field can be explained by a strong quadrupole moment of the photospheric magnetic field, which is also seen in a change of the polarity of the interplanetary magnetic field.

Vernova, E. S.; Tyasto, M. I.; Baranov, D. G.

2014-12-01

58

An advanced approach to finding magnetometer zero levels in the interplanetary magnetic This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

An advanced approach to finding magnetometer zero levels in the interplanetary magnetic field magnetometer zero levels in the interplanetary magnetic field H K Leinweber1, C T Russell1, K Torkar2, T L For a magnetometer that measures weak interplanetary fields, the in-flight determination of zero levels is a crucial

California at Berkeley, University of

59

On the importance of interplanetary magnetic field ?By? on polar cap patch formation  

NASA Astrophysics Data System (ADS)

A number of poleward moving events were observed between 1130 and 1300 UT on 11 February 2004, during periods of southward interplanetary magnetic field (IMF), while the steerable antenna of the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and the Tromsø VHF radar pointed nearly northward at low elevation. In this interval, simultaneous SuperDARN CUTLASS Finland radar measurements showed poleward moving radar aurora forms (PMRAFs) which appeared very similar to the density enhancements observed by the ESR northward pointing antenna. These events appeared quasiperiodically with a period of about 10 min. Comparing the observations from the above three radars, it is inferred that there is an almost one-to-one correspondence between the poleward moving plasma concentration enhancements (PMPCEs) observed by the ESR and the VHF radar and the PMRAFs measured by the CUTLASS Finland radar. These observations are consistent with the interpretation that the polar cap patch material was generated by photoionization at subauroral latitudes and that the plasma was structured by bursts of magnetopause reconnection giving access to the polar cap. There is clear evidence that plasma structuring into patches was dependent on the variability in IMF ?By?. The duration of these events implies that the average evolution time of the newly opened flux tubes from the subauroral region to the polar cap was about 33 min.

Zhang, Q.-H.; Zhang, B.-C.; Liu, R.-Y.; Dunlop, M. W.; Lockwood, M.; Moen, J.; Yang, H.-G.; Hu, H.-Q.; Hu, Z.-J.; Liu, S.-L.; McCrea, I. W.; Lester, M.

2011-05-01

60

Small scale magnetic flux-averaged magnetohydrodynamics  

SciTech Connect

By relaxing exact magnetic flux conservation below a scale [lambda] a system of flux-averaged magnetohydrodynamic equations are derived from Hamilton's principle with modified constraints. An energy principle can be derived from the linearized averaged system because the total system energy is conserved. This energy principle is employed to treat the resistive tearing instability and the exact growth rate is recovered when [lambda] is identified with the resistive skin depth. A necessary and sufficient stability criteria of the tearing instability with line tying at the ends for solar coronal loops is also obtained. The method is extended to both spatial and temporal averaging in Hamilton's principle. The resulting system of equations not only allows flux reconnection but introduces irreversibility for appropriate choice of the averaging function. Except for boundary contributions which are modified by the time averaging process total energy and momentum are conserved over times much longer than the averaging time [tau] but not for less than [tau]. These modified boundary contributions correspond to the existence, also, of damped waves and shock waves in this theory. Time and space averaging is applied to electron magnetohydrodynamics and in one-dimensional geometry predicts solitons and shocks in different limits.

Pfirsch, D. (Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-8046 Garching (Germany)); Sudan, R.N. (Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States))

1994-08-01

61

The IDV index: Its derivation and use in inferring long-term variations of the interplanetary magnetic field strength  

NASA Astrophysics Data System (ADS)

On the basis of a consideration of Bartels' historical u index of geomagnetic activity, we devise an equivalent index that we refer to as the interdiurnal variability (IDV). The IDV index has the interesting and useful property of being highly correlated with the strength of the interplanetary magnetic field (B; R2 = 0.75) and essentially unaffected by the solar wind speed (V; R2 = 0.01) as measured by spacecraft. This enables us to obtain the variation of B from 1872 to the present, providing an independent check on previously reported results for the evolution of this parameter. We find that solar cycle average B increased by ˜25% from the 1900s to the 1950s and has been lower since. If predictions for a small solar cycle 24 bear out, solar cycle average B will return to levels of ˜100 years ago during the coming cycle(s).

Svalgaard, Leif; Cliver, Edward W.

2005-12-01

62

Seeing the Sun in a New Light: Interplanetary Magnetic Field Lines  

NSDL National Science Digital Library

This lesson discusses the Sun's corona, observed from spacecraft in the extreme ultra violet (EUV) and in x-rays, including coronal holes and coronal mass ejections (CME), their effect near Earth and their monitoring from space. This section also discusses related phenomena in interplanetary space and on Earth and contains an optional class exercise in which students learn about field line preservation of flows in a highly conducting plasma, and use it to graphically obtain the shapes of interplanetary magnetic field lines. They also receive information about high-energy ions and electrons accelerated by solar activity, probably from magnetic energy, and the hazard they pose to spacefarers. Students receive an introduction to NASA's great observatories, expanding the coverage of the electromagnetic spectrum by astronomers.

David Stern

63

Comparison of inferred and observed interplanetary magnetic field polarities, 1970-1972  

NASA Technical Reports Server (NTRS)

The inferred polarity (toward or away from the sun) of the interplanetary magnetic field at earth using polar observations of the geomagnetic field has been compared with spacecraft observations. A list published by Svalgaard (1974) of the inferred field polarities in the period from 1970 to 1972 is found to be correct on 82% of the days. A near real-time (same day) method of inferring the polarity of the interplanetary magnetic field using geomagnetic observations at Vostok and Thule is in use at the NOAA Space Environment Laboratory, Boulder, Colorado. During 1972, this method is found to be correct on 87% of the days. A list of 'well-defined' sector boundaries at earth from 1970 to 1972 is given.

Wilcox, J. M.; Svalgaard, L.; Hedgecock, P. C.

1975-01-01

64

The relation between the polarity of the interplanetary magnetic field and the polar geomagnetic field  

NASA Technical Reports Server (NTRS)

The relation between the azimuthal component of the interplanetary magnetic field and the polar cap geomagnetic field is discussed. The geomagnetic effects can be described as produced by an ionospheric current system encircling the magnetic pole. The sense of the current is clockwise during toward-sectors and reversed during away-sectors. The importance of this very direct solar-terrestrial relation is stressed. A recent magnetic sunspot cycle model is discussed as inferred from this relationship, the basic feature being that the sun reproduces the same sector pattern during every sunspot cycle.

Svalgaard, L.

1973-01-01

65

Interplanetary magnetic field dependency of stable Sun-aligned polar cap arcs  

Microsoft Academic Search

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed we had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with corresponding

C. E. Valladares; H. C. Carlson Jr.; K. Fukui

1994-01-01

66

Interplanetary magnetic field dependency of stable sun-aligned polar cap arcs  

Microsoft Academic Search

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed the authors had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with

C. E. Valladares; H.C. Jr. Carlson; K. Fukui

1994-01-01

67

Transport equations for low-energy solar particles in evolving interplanetary magnetic fields  

NASA Technical Reports Server (NTRS)

Two new forms of a simplified Fokker-Planck equation are derived for the transport of low-energy solar energetic particles in an evolving interplanetary magnetic field, carried by a variable radial solar wind. An idealized solution suggests that the 'invariant' anisotropy direction reported by Allum et al. (1974) may be explained within the conventional theoretical framework. The equations may be used to relate studies of solar particle propagation to solar wind transients, and vice versa.

Ng, C. K.

1988-01-01

68

In-Situ Solar Wind and Magnetic Field Signatures of Interplanetary Coronal Mass Ejections  

Microsoft Academic Search

The heliospheric counterparts of coronal mass ejections (CMEs) at the Sun, interplanetary coronal mass ejections (ICMEs),\\u000a can be identified in situ based on a number of magnetic field, plasma, compositional and energetic particle signatures as\\u000a well as combinations thereof. We summarize these signatures and their implications for understanding the nature of these structures\\u000a and the physical properties of coronal mass

Thomas H. Zurbuchen; Ian G. Richardson

2006-01-01

69

Rate of erosion of dayside magnetic flux based on a quantitative study of the dependence of polar cusp latitude on the interplanetary magnetic field  

Microsoft Academic Search

By considering only those periods when the delay time from the ; interplanetary observing position to the magnetosphere is less than about 5 min, ; it is found that irrespective of substorm activity: (a) the 45-min average value ; of interplanetary B\\/sub z\\/ predicts the latitudes of the poleward and equatorward ; boundaries of polar cusp electron precipitation with rms

J. L. Burch

1973-01-01

70

Auroral boundary variations and the interplanetary magnetic field  

Microsoft Academic Search

A DMSP satellite data set of 150 auroral images, obtained during magnetically quiet times, has been analyzed in corrected geomagnetic local time and latitudinal coordinates, and fit to offset circles whose parameters can be compared to the hourly IMF prior to the time of the satellite scans of the aurora. The results for variation of circle radius with the north-south

R. H. Holzworth; C.-I. Meng

1984-01-01

71

Structure of magnetic fields in NOAA active regions 0486 and 0501 and in the associated interplanetary ejecta  

E-print Network

data in order to compare the orientations of the magnetic fields on the solar surface and at 1AU and the strength of the magnetic field in an interplanetary ejecta. A good correspon- dence was also found betweenStructure of magnetic fields in NOAA active regions 0486 and 0501 and in the associated

Yurchyshyn, Vasyl

72

Three-dimensional MHD simulation of interplanetary magnetic field changes at 1 AU as a consequence of simulated solar flares  

Microsoft Academic Search

A fully three-dimensional (3D), time-dependent, MHD interplanetary global model (3D IGM) has been used, for the first time, to study the relationship between different forms of solar activity and transient variations of the north-south component, Bz, of the interplanetary magnetic field (IMF) at 1 AU. One form of solar activity, the flare, is simulated by using a pressure pulse at

C.-C. Wu; M. Dryer; S. T. Wu

1996-01-01

73

Origin of interplanetary southward magnetic fields responsible for major magnetic storms near solar maximum (1978--1979)  

Microsoft Academic Search

The origins of the interplanetary southward B\\/sub z\\/ which cause the 10 major (D\\/sub s\\/\\/sub t\\/<-100 nT) magnetic storms detected during the 500 days of study (August 16, 1978, to December 28, 1979) of the Gonzalez and Tsurutani (1987) work are examined in detail. A full complement of ISEE 3 plasma and field data, an 11-station AE index and the

Bruce T. Tsurutani; Walter D. Gonzalez; Frances Tang; Syun I. Akasofu; Edward J. Smith

1988-01-01

74

A magnetohydrodynamic simulation of the bifurcation of tail lobes during intervals with a northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The interaction of the solar wind with the earth's magnetosphere during a northward interplanetary magnetic field was studied by using a three-dimensional magneto-hydrodynamic model. For a northward interplanetary magnetic field on 5 nT, the plasma sheet thickens near the noon-midnight meridian plane. When projected onto the polar cap this appears as a narrow channel extending from midnight towards noon. This plasma pattern is associated with three pairs of convection cells. The high latitude sunward convection and northern B(z) Birkeland current are caused by magnetic merging in the polar region.

Ogino, T.; Walker, R. J.

1984-01-01

75

Interplanetary magnetic field changes and condensations in comet Halley's plasma tail  

NASA Technical Reports Server (NTRS)

In a time-dependent three dimensional MHD simulation for cometary plasmas, Schmidt-Voigt (1989) could observe the formation of condensations in the plasma tail after a 90 degree change in the interplanetary magnetic field (IMF) sweeping over the comet. We investigated the IMF measurements of the Vega SC in the vicinity of the comet Halley for 90 degree changes in the clock angle and studied the relation between them and optical observations of condensations in the plasma tail. For the time interval 24 Feb. 86 to 14 Mar. 86, we could not find a correlation between such changes and the release of condensations from the cometary head.

Delva, Magda; Schwingenschuh, K.

1992-01-01

76

Structures of Interplanetary Magnetic Flux Ropes and Comparison with Their Solar Sources  

NASA Astrophysics Data System (ADS)

Whether a magnetic flux rope is pre-existing or formed in situ in the Sun's atmosphere, there is little doubt that magnetic reconnection is essential to release the flux rope during its ejection. During this process, the question remains: how does magnetic reconnection change the flux-rope structure? In this work, we continue with the original study of Qiu et al. by using a larger sample of flare-coronal mass ejection (CME)-interplanetary CME (ICME) events to compare properties of ICME/magnetic cloud (MC) flux ropes measured at 1 AU and properties of associated solar progenitors including flares, filaments, and CMEs. In particular, the magnetic field-line twist distribution within interplanetary magnetic flux ropes is systematically derived and examined. Our analysis shows that, similar to what was found before, for most of these events, the amount of twisted flux per AU in MCs is comparable with the total reconnection flux on the Sun, and the sign of the MC helicity is consistent with the sign of the helicity of the solar source region judged from the geometry of post-flare loops. Remarkably, we find that about half of the 18 magnetic flux ropes, most of them associated with erupting filaments, have a nearly uniform and relatively low twist distribution from the axis to the edge, and the majority of the other flux ropes exhibit very high twist near the axis, up to >~ 5 turns per AU, which decreases toward the edge. The flux ropes are therefore not linearly force-free. We also conduct detailed case studies showing the contrast of two events with distinct twist distribution in MCs as well as different flare and dimming characteristics in solar source regions, and discuss how reconnection geometry reflected in flare morphology may be related to the structure of the flux rope formed on the Sun.

Hu, Qiang; Qiu, Jiong; Dasgupta, B.; Khare, A.; Webb, G. M.

2014-09-01

77

ON THE EFFECT OF A WEAK INTERPLANETARY MAGNETIC FIELD ON THE INTERACTION BETWEEN THE SOLAR WIND AND THE GEOMAGNETIC FIELD  

Microsoft Academic Search

the presence of a weak interplanetary magnetic field may lead to the ; formation of a collision-free shock wave upstream from the boundary of the ; geomagnetic field and to a transition region characterized by an irregular ; magnetic field in the intervening space. Previous calculations of the ; coordinates of the shock wave are improved upon by application of

John R. Spreiter; Wm. Prichard Jones

1963-01-01

78

Interplanetary magnetic field polarity and the size of low-pressure troughs near 180 deg W longitude  

NASA Technical Reports Server (NTRS)

The relationship between interplanetary magnetic field polarity and the area of low pressure (300 mbar) troughs near 180 deg W longitude is examined. For most of the winters from 1951 to 1973, the trough size, as indicated by the vorticity area index, is found to be significantly greater when the interplanetary magnetic field is directed away from the sun than when the field is directed towards the sun. This relationship is shown to hold for various combinations of winters and for most months within a winter, and be most pronounced at the time when polarity was determined. It is suggested that the phenomenon is caused by merging of interplanetary magnetic field lines, when polarity is directed away from the sun, with geomagnetic field lines in the Northern Hemisphere (where these measurements were made), allowing energetic particle fluxes to have access to the north polar region

Wilcox, J. M.; Duffy, P. B.; Schatten, K. H.; Svalgaard, L.; Scherrer, P. H.; Roberts, W. O.; Olson, R. H.

1979-01-01

79

A dynamic and realistic heliospheric modelling using interplanetary scintillation and photospheric magnetic data  

NASA Astrophysics Data System (ADS)

A new MHD simulation method for reproducing a realistic and time-varying global heliospheric modelling is developed using solar-wind speed data from interplanetary scintillation (IPS) of Nagoya University and photospheric magnetic data from the Wilcox Solar Observatory. These data sets provide inner boundary spherical surface conditions centered at 5 AU from the Sun and include both three-component solar-wind velocity and magnetic field. Hence it enables us to reproduce dynamical co-rotating wind-wind interactions and also magnetic field structures such as an oscillating equatorial magnetic neutral sheet in the three-dimensional heliosphere. In our results, a realistic and oscillating equatorial neutral sheet and periodic increases of temperature due to wind-wind interactions are reproduced during the period from December 6, 2000 to December 31, 2010, both in the interplanetary space and the heliosheath. The decrease of the mean solar wind density during the solar-cycle 23 from 5/cc to 3.5/cc at 1AU is taken into account. The interstellar magnetic field intensity is adopted as 4.6 micro G so that the observed V1-crossing with the termination shock is satisfied. The decrement degree of the solar-wind density around year 2006 is imposed to fit the observed V2-crossing with the termination shock. This simulation result is compared with that of previous simulation in which V2 plasma data were used as the inner boundary assuming an axisymmetric solar wind and a 3 micro G interstellar magnetic field intensity.

Washimi, H.; Hayashi, K.; Tokumaru, M.; Zank, G. P.; Hu, Q.; Tanaka, T.; Florinski, V. A.; Adams, J. H.; Kubo, Y.

2011-12-01

80

Long-term Trends in Interplanetary Magnetic Field Strength and Solar Wind Structure during the 20th Century  

NASA Technical Reports Server (NTRS)

Lockwood et al have recently reported an approximately 40% increase in the radial component of the interplanetary magnetic field (IMF) at Earth between 1964 and 1996. We argue that this increase does not constitute a secular trend but is largely the consequence of lower than average fields during solar cycle 20 (1964-1976) in comparison with surrounding cycles. For times after 1976 the average IMF strength has actually decreased slightly. Examination of the cosmic ray intensity, an indirect measure of the IMF strength, over the last five solar cycles (19-23) also indicates that cycle averages of the IMF strength have been relatively constant since approximately 1954. We also consider the origin of the well-documented increase in the geomagnetic alphaalpha index that occurred primarily during the first half of the twentieth century. We surmise that the coronal mass ejection (CME) rate for recent solar cycles was approximately twice as high as that for solar cycles 100 years ago. However, this change in the CME rate and the accompanying increase in 27-day recurrent storm activity reported by others are unable to account completely for the increase in alphaalpha. Rather, the CMEs and recurrent high-speed streams at the beginning of the twentieth century must have been embedded in a background of slow solar wind that was less geoeffective (having, for example, lower IMF strength and/or flow speed) than its modern counterpart.

Richardson, I. G.; Cliver, E. W.; Cane, H. V.; White, Nicholas E. (Technical Monitor)

2002-01-01

81

Simulation of interplanetary magnetic field B{sub y} penetration into the magnetotail  

SciTech Connect

Based on our global 3D magnetospheric MHD simulation model, we investigate the phenomena and physical mechanism of the B{sub y} component of the interplanetary magnetic field (IMF) penetrating into the magnetotail. We find that the dayside reconnected magnetic field lines move to the magnetotail, get added to the lobe fields, and are dragged in the IMF direction. However, the B{sub y} component in the plasma sheet mainly originates from the tilt and relative slippage of the south and north lobes caused by plasma convection, which results in the original B{sub z} component in the plasma sheet rotating into a B{sub y} component. Our research also shows that the penetration effect of plasma sheet B{sub y} from the IMF B{sub y} during periods of northward IMF is larger than that during periods of southward IMF.

Guo, Jiuling [Center for Educational Technology, Peking University, Beijing 100871 (China); State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Shen, Chao; Liu, Zhenxing [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)

2014-07-15

82

Interplanetary medium condition effects in the South Atlantic Magnetic Anomaly: A case study  

NASA Astrophysics Data System (ADS)

One way to investigate the magnetosphere-ionosphere coupling is through the simultaneous observation of different parameters measured at different locations of the geospace environment and try to determine some relationships among them. The main objective of this work is to examine how the solar energetic particles and the interplanetary medium conditions may affect the space and time configuration of the ring current at low-latitudes and also to get a better understanding on how these particles interfere with the lower ionosphere in the South Atlantic Magnetic Anomaly region (SAMA). To accomplish this, the cosmic noise absorption (CNA) and the horizontal component of the Earth's magnetic field data measured from sites located in the SAMA region were compared with the proton and electron fluxes, interplanetary medium conditions (solar wind and the north-south component of the interplanetary magnetic field measured on board satellites), the SYM-H index and magnetometer data from Kakioka (KAK-Japan), located significantly outside the SAMA region. The time series analyzed correspond to the geomagnetic disturbance that occurred on August 25-30, 1998. The analysis was performed by implementing wavelet techniques, with particular attention to singularities detection, which highlights the presence of transient signals. The results are discussed in terms of the first three wavelet decomposition levels of the parameters. The magnitude of wavelet coefficients of the solar wind and proton flux at the two energy ranges analyzed is timely well correlated, indicating that these two signals are energetically linked. The larger wavelet coefficient amplitude of KAK and VSS magnetograms shows time delays that are compatible with an asymmetric configuration of the ring current, considering that at the storm time, VSS was at the dawn sector of the magnetosphere and KAK at the dusk side. The wavelet analysis of CNA signals reveals that the signal may be sensitive to the ionization produced by energetic electrons and protons as well. The time delays observed in wavelet coefficients may give an indication of the different accelerating process to which the particles are submitted when traveling along the magnetic field lines, from higher to lower latitudes, and the likely contribution of these particles to the ionization measured as an absorption of the cosmic noise in the lower ionosphere.

Mendes da Costa, Aracy; Oliveira Domingues, Margarete; Mendes, Odim; Marques Brum, Christiano Garnett

2011-07-01

83

On the association of magnetic clouds with disappearing filaments. [interplanetary phenomena associated with coronal mass ejection  

NASA Technical Reports Server (NTRS)

Evidence is presented that an interplanetary magnetic cloud preceding an interaction region, observed at earth on January 24, 1974, is associated with the eruptive filament of disparition brusque (DB) near central meridian on January 18. The DB was also associated with a long-decay soft X ray transient and a long-duration gradual-rise-and-fall radio burst. To assess whether magnetic clouds are generally associated with DBs, results from statistical testing of the relation of 33 magnetic clouds (and 33 control samples without magnetic clouds) to disappearing filaments near central meridian (approximately less than 45 deg central meridian distance) are presented. The hypothesis that magnetic cloud are the 1-AU counterparts of either eruptive filaments or the coronal mass ejections which probably accompany them is supported. The major result is that disappearing filaments occur more frequently on the days when magnetic clouds are launched than on control days, a result obtained with greater than 99 pct confidence. There is a suggestion that clouds following shocks, probably launched at times of solar flares, are not as strongly associated with disappearing filaments as are clouds launched less violently.

Wilson, R. M.; Hildner, E.

1986-01-01

84

Magnetic and plasma response of the Earth's magnetosphere to interplanetary shock  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the global response of magnetosphere to interplanetary shock, and focus on the magnetic and plasma variations related to aurora. The analysis utilizes data from simultaneous observations of interplanetary shocks from available spacecraft in the solar wind and the Earth's magnetosphere such as ACE, Wind and SOHO in solar wind, LANL and GOES in outer magnetosphere, TC1 in the midinight neutral plasma sheet, Geotail and Polar in dusk side of plasma sheet, and Cluster in downside LLBL. The shock front speed is ~1051 km/s in the solar wind, and ~981km/s in the Earth's magnetosphere. The shock is propagating anti-sunward (toward the Earth) in the plasma frame with a speed of ~320 km/s. After the shock bumps at the magnetopause, the dayside aurora brightens, then nightside aurora brightens and expanses to poleward. During the aurora activity period, the fast earthward and tailward flows in plasma sheet are observed by TC1 (X~7.1 Re, Y~1.2 Re). The variation of magnetic field and plasma in duskside of magnetosphere is weaker than that in dawnside. At low latitude boundary layer (LLBL), the Cluster spacecraft detected rolled-up large scale vortices generated by the Kelvin-Helmholtz instability (KHI). Toroidal oscillations of the magnetic field in the LLBL might be driven by the Kelvin-Helmholtz instability. The strong IP shock highly compresses the magnetopause and the outer magnetosphere. This process may also lead to particle precipitation and auroral brightening (Zhou and Tsurutani, 1999; Tsurutani et al., 2001 and 2003).

Du, A.; Cao, X.; Wang, R.; Zhang, Y.

2013-12-01

85

Variations of solar, interplanetary, and geomagnetic parameters with solar magnetic multipole fields during Solar Cycles 21-24  

NASA Astrophysics Data System (ADS)

In this study we compare the temporal variations of the solar, interplanetary, and geomagnetic (SIG) parameters with that of open solar magnetic flux from 1976 to 2012 (from Solar Cycle 21 to the early phase of Cycle 24) for a purpose of identifying their possible relationships. By the open flux, we mean the average magnetic field over the source surface (2.5 solar radii) times the source area as defined by the potential field source surface (PFSS) model of the Wilcox Solar Observatory (WSO). In our result, most SIG parameters except the solar wind dynamic pressure show rather poor correlations with the open solar magnetic field. Good correlations are recovered when the contributions from individual multipole components are counted separately. As expected, solar activity indices such as sunspot number, total solar irradiance, 10.7 cm radio flux, and solar flare occurrence are highly correlated with the flux of magnetic quadrupole component. The dynamic pressure of solar wind is strongly correlated with the dipole flux, which is in anti-phase with Solar Cycle (SC). The geomagnetic activity represented by the Ap index is correlated with higher order multipole components, which show relatively a slow time variation with SC. We also found that the unusually low geomagnetic activity during SC 23 is accompanied by the weak open solar fields compared with those in other SCs. It is argued that such dependences of the SIG parameters on the individual multipole components of the open solar magnetic flux may clarify why some SIG parameters vary in phase with SC and others show seemingly delayed responses to SC variation.

Kim, Bogyeong; Lee, Jeongwoo; Yi, Yu; Oh, Suyeon

2015-01-01

86

MAGNETIC VARIANCES AND PITCH-ANGLE SCATTERING TIMES UPSTREAM OF INTERPLANETARY SHOCKS  

SciTech Connect

Recent observations of power-law time profiles of energetic particles accelerated at interplanetary shocks have shown the possibility of anomalous, superdiffusive transport for energetic particles throughout the heliosphere. Those findings call for an accurate investigation of the magnetic field fluctuation properties at the resonance frequencies upstream of the shock's fronts. Normalized magnetic field variances, indeed, play a crucial role in the determination of the pitch-angle scattering times and then of the transport regime. The present analysis investigates the time behavior of the normalized variances of the magnetic field fluctuations, measured by the Ulysses spacecraft upstream of corotating interaction region (CIR) shocks, for those events which exhibit superdiffusion for energetic electrons. We find a quasi-constant value for the normalized magnetic field variances from about 10 hr to 100 hr from the shock front. This rules out the presence of a varying diffusion coefficient and confirms the possibility of superdiffusion for energetic electrons. A statistical analysis of the scattering times obtained from the magnetic fluctuations upstream of the CIR events has also been performed; the resulting power-law distributions of scattering times imply long range correlations and weak pitch-angle scattering, and the power-law slopes are in qualitative agreement with superdiffusive processes described by a Levy random walk.

Perri, Silvia; Zimbardo, Gaetano, E-mail: silvia.perri@fis.unical.it, E-mail: gaetano.zimbardo@fis.unical.it [Dipartimento di Fisica, Universita della Calabria, Ponte P. Bucci, Cubo 31C, I-87036 Arcavacata di Rende (Italy)

2012-07-20

87

Anomalous magnetosheath flows and distorted subsolar magnetopause for radial interplanetary magnetic fields  

NASA Astrophysics Data System (ADS)

On 12 August 2007 from 1436 to 1441 UT, when the five THEMIS probes (THA, THB, THC, THD, and THE) were located near the subsolar magnetopause, a sunward flow was observed in the magnetosheath. A fast anti-sunward flow (-280 km/s) was observed in the magnetosheath before the sunward flow. Although THA observed this fast anti-sunward flow, THC and THD, which were also in the magnetosheath, instead observed a slow flow, indicating that the fast flow was small in scale. With the observed flow vectors and the magnetopause normal directions estimated from tangential discontinuity analysis, we conclude that this fast flow creates an indentation on the magnetopause, 1 R E deep and 2 R E wide. The magnetopause subsequently rebounds, rotating the flow direction sunward along the surface of the magnetopause. The fast flow is likely related to the radial interplanetary magnetic field.

Shue, J.-H.; Chao, J.-K.; Song, P.; McFadden, J. P.; Suvorova, A.; Angelopoulos, V.; Glassmeier, K. H.; Plaschke, F.

2009-09-01

88

Anomalous Magnetosheath Flows and Distorted Subsolar Magnetopause for Radial Interplanetary Magnetic Fields  

NASA Astrophysics Data System (ADS)

On 12 August 2007 from 1436 to 1441 UT, when the five THEMIS probes (THA, THB, THC, THD, and THE) were located near the subsolar magnetopause, a sunward flow was observed in the magnetosheath. A fast anti-sunward flow (-280 km/s) was observed in the magnetosheath before the sunward flow. Although THA observed this fast anti-sunward flow, THC and THD, which were also in the magnetosheath, instead observed a slow flow, indicating that the fast flow was small in scale. With the observed flow vectors and the magnetopause normal directions estimated from tangential discontinuity analysis, we conclude that this fast flow creates an indentation on the magnetopause, 1 Re deep and 2 Re wide. The magnetopause subsequently rebounds, rotating the flow direction sunward along the surface of the magnetopause. The fast flow is likely related to the radial interplanetary magnetic field.

Shue, J.; Chao, J. K.; Song, P.; McFadden, J. P.; Suvorova, A.; Angelopoulos, V.; Glassmeier, K.; Plaschke, F.

2009-12-01

89

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

90

What Controls the Magnetic Field Configuration of Interplanetary Coronal Mass Ejections ?  

NASA Astrophysics Data System (ADS)

In this work we address the question of the classification of interplanetary coronal mass ejections (ICMEs): magnetic cloud (MC) or ejecta (EJ). Using 186 shock-associated ICMEs from 1997 to 2006, we have examined three possible causes : (1) magnetic complexity characterized by sunspot number, (2) CME direction characterized by CME angular distance (the angle between the CME cone axis and the sky plane), and (3) CME-CME interaction characterized by the number of halo CMEs. First, the annual fraction of MC is poorly anti-correlated (R=-0.36) with annual sunspot number. Second, more than half of the CMEs that originated near the central meridian produced EJs and the distribution of CME angular distance for 38 EJs is not much different from that for 16 MCs. Third, the annual fraction of MC is well anti-correlated (R=-0.78) with the annual number of halo CMEs. In addition, we also searched for candidate of interacting CMEs according to temporal and spatial closeness by considering all halo CMEs during the same period. As a result, we find that the annual fraction of interacting CMEs is well correlated (R=0.87) with the annual number of the halo CMEs as well as anti-correlated (R=-0.85) with the annual fraction of MCs. The contingency table between CME-CME interaction and MC occurrence also shows a good statistical result (Prediction of detection 'yes' is 0.88, and Critical Success Index is 0.62), which is better than that for the halo CME-storm relationship. Our results imply that the CME interaction is mainly responsible for their observed structure (MC or EJ) in the interplanetary medium.

Moon, Y.; Gopalswamy, N.; Kim, R.; Xie, H.; Yashiro, S.

2011-12-01

91

Theoretical models of polar-cap convection under the influence of a northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The unexpected patterns of high-latitude auroral luminosity and ionospheric convection that are observed when the interplanetary magnetic field (IMF) has a northward orientation have inspired a variety of theoretical interpretations. The existing models, all referring to steady-state conditions, can be classified according to the topology of the polar magnetic field lines and of the polar-cap convection streamlines. The classes of model include: (1) a closed magnetosphere model, (2) a conventional open model with a distorted, but topologically unchanged, polar-cap boundary, (3) a conventional open model with distorted, but topologically unchanged, polar-cap convection cells, (4) a modified open model with 'lobe convection cells' contained wholly on open magnetic-field lines, and (5) a modified open model with a bifurcated polar cap. The third and fourth types require significant regions of sunward flow on open polar-cap field lines, a concept that presents serious theoretical difficulties. The other three types appear equally viable from a theoretical point of view, and the comparison against observations is an ongoing enterprise. Outstanding theoretical questions include (a) how do observed structures in the polar ionosphere map along magnetic field lines into the magnetosphere?, (b) what is the mechanism that drives the observed sunward convection at highest latitudes on the day side?, and (c) what role does time dependence play in the observed phenomena?

Hill, T. W.

1994-01-01

92

Yearly Comparison of Magnetic Cloud Parameters, Sunspot Number, and Interplanetary Quantities for the First 18 Years of the Wind Mission  

NASA Astrophysics Data System (ADS)

In the scalar part of this study, we determine various statistical relationships between estimated magnetic cloud (MC) model fit-parameters and sunspot number (SSN) for the interval defined by the Wind mission, i.e., early 1995 until the end of 2012, all in terms of yearly averages. The MC-fitting model used is that of Lepping, Jones, and Burlaga ( J. Geophys. Res. 95, 11957 - 11965, 1990). We also statistically compare the MC fit-parameters and other derived MC quantities [ e.g., axial magnetic flux (?O) and total axial current density ( J O)] with some associated ambient interplanetary quantities (including the interplanetary magnetic field ( B IMF), proton number density ( N P), and others). Some of the main findings are that the minimum SSN is nearly simultaneous with the minimum in the number of MCs per year ( N MC), which occurs in 2008. There are various fluctuations in N MC and the MC model-fit quality ( Q') throughout the mission, but the last four years (2009 - 2012) are markedly different from the others; Q' is low and N MC is large over these four years. N MC is especially large for 2012. The linear correlation coefficient (c.c.?0.75) between the SSN and each of the three quantities J O, MC diameter (2 R O), and B IMF, is moderately high, but none of the MC parameters track the SSN well in the sense defined in this article. However, there is good statistical tracking among the following: MC axial field, B IMF, 2 R O, average MC speed ( V MC), and yearly average solar wind speed ( V SW) with relatively high c.c.s among most of these. From the start of the mission until late 2005, J O gradually increases, with a slight violation in 2003, but then a dramatic decrease (by more than a factor of five) occurs to an almost steady and low value of ? 3 ?A km-2 until the end of the interval of interest, i.e., lasting for at least seven years. This tends to split the overall 18-year interval into two phases with a separator at the end of 2005. There is good tracking between 2 R O and the total axial current density, as expected. The MC duration is also correlated well with these two quantities. ?O shows marked variations throughout the mission, but has no obvious trend. N P, B IMF, V MC, Q', and V SW are all quite steady over the full 18 years and have markedly low relative variation. Concerning vector quantities, we examine the distribution of MC type for the 18 years, where type refers to the field directional change through a given MC starting at first encounter ( i.e., North-to-South, or South-to-North, All South, All North, etc.). Combining all 18 years of MC types shows that the occurrence rate varies strongly across the various MC types, with N-to-S being most prevalent, with a 27 % occurrence rate (of all MCs), and S-to-N being second, with a 23 % occurrence. Then All N and All S come next at 16 % and 10 % occurrence rate, respectively. All others are at 7 % or lower. For the variation of MC types with time, the southern types ( i.e., those that start with a southern magnetic field, a negative B Z in geocentric-solar-ecliptic coordinates) decrease, as the northern types ( i.e., those that start with a northern field) increase, apparently consistent with the specific timing of the polarity change of the solar magnetic field, as predicted by Bothmer and Rust (in Crooker, N., Joselyn, J., Feynman J. (eds), Geophys. Monogr., 139 - 146, 1997).

Lepping, R. P.; Wu, C.-C.; Berdichevsky, D. B.

2015-02-01

93

Relating Interplanetary Helium Variation to Coronal Magnetic Fields and Solar Wind Formation  

NASA Astrophysics Data System (ADS)

We have recently identified two new features in the variation of the relative abundance of helium in the solar wind relative to hydrogen as observed by the Wind spacecraft. First, the He/H ratio is a linear function of speed for solar wind speeds ranging from 250-550 km/s. This signal is most evident during the previous solar minimum from 1995 through 1997. Secondly, during that same quiet interval we have identified a six-month periodic modulation of the He/H ratio which can be seen at all solar wind speeds. This modulation is in phase with the orbit of the Earth about the Sun, and maxima in He/H occur at the times when Earth is most distant from the heliographic equator. As we shall demonstrate, these effects are partly in agreement with theoretical models of the magnetic topology of the corona and of the formation of the solar wind. However, these features present challenges to the currently accepted paradigm of solar wind, with helium-poor wind emerging from coronal streamers and fast, helium-rich wind emerging from coronal holes. The abundance of helium is a sensitive test of models of solar wind formation and of the connection between photospheric, coronal, and interplanetary magnetic fields. The observed variations of He/H will be discussed in terms of existing models of coronal magnetic field topology and solar wind acceleration. This research is supported by the NSF/SHINE grant ATM-0327723.

Kasper, J. C.; Lazarus, A. J.; Steinberg, J. T.; Riley, P.; Sheeley, N.; Wang, Y.

2003-12-01

94

Large-scale variations of the interplanetary magnetic field: Voyager 1 and 2 observations between 1-5 AU  

NASA Technical Reports Server (NTRS)

Observations by the Voyager 1 and 2 spacecraft of the interplanetary magnetic field between 1 and 5 AU were used to investigate the large scale structure of the IMF in a period of increasing solar activity. The Voyager spacecraft found notable deviations from the Parker axial model. These deviations are attributed both to temporal variations associated with increasing solar activity, and to the effects of fluctuations of the field in the radial direction. The amplitude of the latter fluctuations were found to be large relative to the magnitude of the radial field component itself beyond approximately 3 AU. Both Voyager 1 and Voyager 2 observed decreases with increasing heliocentric distance in the amplitude of transverse fluctuations in the averaged field strength (B) which are consistent with the presence of predominantly undamped Alfven waves in the solar wind, although and necessarily implying the presence of them. Fluctuations in the strength of B (relative to mean field strength) were found to be small in amplitude, with a RMS which is approximately one third of that for the transverse fluctuations and they are essentially independent of distance from the Sun.

Burlaga, L. F.; Lepping, R. P.; Behannon, K. W.; Klein, L. W.; Neubauer, F. M.

1981-01-01

95

Self-similar evolution of interplanetary magnetic clouds and Ulysses measurements of the polytropic index inside the cloud  

NASA Technical Reports Server (NTRS)

A self similar model for the expanding flux rope is developed for a magnetohydrodynamic model of interplanetary magnetic clouds. It is suggested that the dependence of the maximum magnetic field on the distance from the sun and the polytropic index gamma has the form B = r exp (-1/gamma), and that the ratio of the electron temperature to the proton temperature increases with distance from the sun. It is deduced that ion acoustic waves should be observed in the cloud. Both predictions were confirmed by Ulysses observations of a 1993 magnetic cloud. Measurements of gamma inside the cloud demonstrate sensitivity to the internal topology of the magnetic field in the cloud.

Osherovich, Vladimir A.; Fainberg, J.; Stone, R. G.; MacDowall, R. J.; Berdichevsky, D.

1997-01-01

96

The origin of interplanetary sectors. [solar corona  

NASA Technical Reports Server (NTRS)

The coronal magnetic models of Altschuler and Newkirk (1969), Schatten, Wilcox, and Ness (1969), and Schatten (1971), that allowed calculation of the coronal magnetic field from the observed photometric magnetic field, are reviewed with reference to coronal holes and the origin of interplanetary magnetic field sectors. Some misconceptions about interplanetary magnetic field sectors are examined. It is suggested that interplanetary sector structure should be confined to studies of the outer corona, interplanetary space, and objects therein, but not the sun itself.

Schatten, K. H.

1980-01-01

97

Determination of interplanetary magnetic field strength, solar wind speed and EUV irradiance, 1890-2003  

Microsoft Academic Search

A newly constructed long-term geomagnetic index, the interdiurnal variability (the IDV index; defined to be the unsigned difference between hourly averages of the H-component of the field near local midnight at a midlatitude station for consecutive days), has the useful property that its yearly averages are highly correlated with the solar wind magnetic field strength (B) and are independent of

Leif Svalgaard; Edward W. Cliver; Philippe Lesager

2003-01-01

98

Dependence of the spectrum of Pc 3-4 pulsations on the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Dependence of the power spectrum of Pc 3-4 magnetic pulsations observed at the ATS 6 geosynchronous satellite on the interplanetary magnetic field (IMF) has been studied. Pulsation events that were observed near noon and exhibited harmonic structure are chosen for analysis. Further selected are pulsation events with identical fundamental frequency to study dependence of the power of pulsations at different harmonic bands on the IMF. A weak negative correlation is observed between the IMF cone angle theta-XB and the power of pulsations in the frequency range 20-70 mHz. Also, a positive correlation between the intensity of the IMF B(IMF) and the power of pulsations at 50-70 mHz is found. This B(IMF) control is present at all ranges of the cone angle. A comparison is conducted of this observation with the frequency of bow shock associated upstream waves predicted from a model of wave generation by a cyclotron resonance of ions reflected at the bow shock. The predicted frequency depends on the IMF as B(IMF) (cos theta-XB)-squared. Although this relation gives a proportionality between the frequency and B(IMF) qualitatively consistent with the observation, it does not explain the most obvious IMF control of the spectrum of the pulsations.

Takahashi, K.; Mcpherron, R. L.; Terasawa, T.

1984-01-01

99

Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet  

NASA Technical Reports Server (NTRS)

There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

Hau, L.-N.; Erickson, G. M.

1995-01-01

100

SIGNATURE IN THE INTERPLANETARY MEDIUM FOR SUBSTORMS  

Microsoft Academic Search

A detailed signature for individual substorms is sought in the interplanetary medium. Hourly values of interplanetary field and plasma parameters are correlated with hourly averages of the AE index. An interplanetary variable involving the southward component of the interplanetary field in the solar magnetospheric coordinate system is shown to be singularly important for the generation of substorms. The parameter best

Roger L. Arnoldy

1971-01-01

101

Wavelet detection of coherent structures in interplanetary magnetic flux ropes and its role in the intermittent turbulence  

NASA Astrophysics Data System (ADS)

We implement a method to detect coherent magnetic structures using the Haar discrete wavelet transform (Salem et al., ApJ 702, 537, 2009), and apply it to an event detected by Cluster at the turbulent boundary layer of an interplanetary magnetic flux rope. The wavelet method is able to detect magnetic coherent structures and extract main features of solar wind intermittent turbulence, such as the power spectral density and the scaling exponent of structure functions. Chian and Muñoz (ApJL 733, L34, 2011) investigated the relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection measured by Cluster upstream of the Earth's bow shock on 2005 January 21. We found observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer, where the scaling exponent of structure functions of magnetic fluctuations exhibits multifractal behavior. Using the wavelet technique, we show that the current sheets associated to magnetic reconnection are part of the set of magnetic coherent structures responsible for multifractality. By removing them using a filtering criteria, it is possible to recover a self-similar scaling exponent predicted for homogeneous turbulence. Finally, we discuss an extension of the wavelet technique to study coherent structures in two-dimensional solar magnetograms.

Muñoz, P. R.; Chian, A. C.

2013-12-01

102

Ionospheric convection signatures of the interchange cycle at small interplanetary magnetic field clock angles  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to show a "proof of the existence" of the ionospheric situation that is expected for the interchange cycle, during periods of favorable interplanetary magnetic field (IMF) and dipole tilt conditions. To do so, we present three case studies of dayside high-latitude ionospheric convection that is observed around the equinoxes (near-zero dipole tilt) and at small IMF clock angles (one ?c ˜ -30° event and two ?c ˜ 30° events, where ?c ? Arg(BZ + iBY)), using Super Dual Auroral Radar Network (SuperDARN)/Defense Meteorological Satellite Program (DMSP)/National Oceanic and Atmospheric Administration (NOAA) data in the Northern Hemisphere and, when available, DMSP data in the Southern Hemisphere. The convection pattern exhibits twin reverse cells in both hemispheres, but the constituents of each cell are different. In the Northern Hemisphere, for ?c ˜ 30° (?c ˜ -30°), the center of the dawnside (duskside) cell is located poleward of the polar cap boundary, while the center of the duskside (dawnside) cell is located equatorward of the polar cap boundary. For ?c ˜ 30°, we confirmed that the above-mentioned dawn-dusk relation reverses in the Southern Hemisphere. The north-south asymmetric behavior of the conjugate reverse cells, on the dawnside and duskside each, is consistent with two independent interchange cycles that result from the coupling of IMF-lobe reconnection in one hemisphere with lobe-closed reconnection in the opposite hemisphere.

Watanabe, Masakazu; Sofko, George J.; Yan, Xi; McWilliams, Kathryn A.; St.-Maurice, Jean-Pierre; Koustov, Alexandre V.; Hussey, Glenn C.; Hairston, Marc R.

2010-12-01

103

Field lines and magnetic surfaces in a two-component slab/2D model of interplanetary magnetic fluctuations  

NASA Technical Reports Server (NTRS)

A two-component model for the spectrum of interplanetary magnetic fluctuations was proposed on the basis of ISEE observations, and has found an intriguing level of application in other solar wind studies. The model fluctuations consist of a fraction of 'slab' fluctuations, varying only in the direction parallel to the locally uniform mean magnetic field B(0) and a complement of 2D (two-dimensional) fluctuations that vary in the directions transverse to B(0). We have developed an spectral method computational algorithm for computing the magnetic flux surfaces (flux tubes) associated with the composite model, based upon a precise analogy with equations for ideal transport of a passive scalar in planar two dimensional geometry. Visualization of various composite models will be presented, including the 80 percent 2D/ 20 percent slab model with delta B/B(0) approximately equals 1 and a minus 5/3 spectral law, that is thought to approximately represent a snapshot of solar wind turbulence. Characteristically, the visualizations show that flux tubes, even when defined as regular on some plane, shred and disperse rapidly as they are viewed along the parallel direction. This diffusive process, which generalizes the standard picture of field line random walk, will be discussed in detail. Evidently, the traditional picture that flux tubes randomize like strands of spaghetti with a uniform tangle along the axial direction is in need of modification.

Matthaeus, W. H.; Pontius, D. H., Jr.; Gray, P. C.; Bieber, J. W.

1995-01-01

104

Interplanetary magnetic field control of the ionospheric field-aligned current and convection distributions  

NASA Astrophysics Data System (ADS)

Patterns of the high-latitude ionospheric convection and field-aligned current (FAC) are a manifestation of the solar wind-magnetosphere-ionosphere coupling. By observing them we can acquire information on magnetopause reconnection, a process through which solar wind energy enters the magnetosphere. We use over 10 years of magnetic field and convection data from the CHAMP satellite and Super Dual Auroral Radar Network radars, respectively, to display combined distributions of the FACs and convection for different interplanetary magnetic field (IMF) orientations and amplitudes. During southward IMF, convection follows the established two-cell pattern with associated Region 1 and Region 2 FACs, indicating subsolar reconnection. During northward IMF, superposed on a weak two-cell pattern there is a reversed two-cell pattern with associated Region 0 and Region 1 FACs on the dayside, indicating lobe reconnection. For dominant IMF Bx, the sign of Bz determines whether lobe or subsolar reconnection signatures will be observed, but Bx will weaken the signatures compared to pure northward or southward IMF. When the IMF rotates from northward to duskward or dawnward, the distinct reversed and forward two-cell patterns start to merge into a distorted two-cell pattern. This is in agreement with the IMF By displacing the reconnection location from the open lobe field lines to closed dawn or dusk field lines, even though IMF Bz>0. As the IMF continues to rotate southward, the distorted pattern transforms smoothly to that of the symmetric two-cell pattern. While the IMF direction determines the configuration of the FACs and convection, the IMF amplitude affects their intensity.

Juusola, L.; Milan, S. E.; Lester, M.; Grocott, A.; Imber, S. M.

2014-04-01

105

The relation between the azimuthal component of the interplanetary magnetic field and the geomagnetic field in the polar caps  

NASA Technical Reports Server (NTRS)

The recently discovered relation between the azimuthal component of the interplanetary magnetic field and magnetic variations in the earth's polar caps is reviewed. When the IMF azimuthal component is positive (typical of an interplanetary sector with magnetic field directed away from the sun) geomagnetic perturbations directed away from the earth are observed within 8 deg from the corrected geomagnetic pole. When the IMF azimuthal component is negative (typically within toward sectors) the geomagnetic perturbations are directed towards the earth at both poles. These perturbations can also be described by an equivalent current flowing at a constant magnetic latitude of 80 - 82 deg clockwise around the magnetic poles during toward sectors and counterclockwise during away sectors. This current fluctuates in magnitude and direction with the azimuthal component of the IMF, with a delay time of the order of 20 minutes. The importance of this effect for understanding of both solar magnetism and magnetospheric physics is stressed in view of the possibility for investigating the solar sector structure during the last five sunspot cycles.

Svalgaard, L.

1973-01-01

106

MESSENGER observations of the response of Mercury's magnetosphere to northward and southward interplanetary magnetic fields  

NASA Astrophysics Data System (ADS)

M. H. Ac?a (2), B. J. Anderson (3), D. N. Baker (4), M. Benna (2), S. A. Boardsen (1), G. n Gloeckler (5), R. E. Gold (3), G. C. Ho (3), H. Korth (3), S. M. Krimigis (3), S. A. Livi (6), R. L. McNutt Jr. (3), J. M. Raines (5), M. Sarantos (1), D. Schriver (7), S. C. Solomon (8), P. Travnicek (9), and T. H. Zurbuchen (5) (1) Heliophysics Science Division, NASA GSFC, Greenbelt, MD 20771, USA, (2) Solar System Exploration Division, NASA GSFC, Greenbelt, MD 20771, USA, (3) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA, (4) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA, (5) Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA (6) Southwest Research Institute, San Antonio, TX 28510, USA, (7) Institute for Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024, USA, (8) Department of Terrestrial Magnetism, Carnegie Institution of Washington, DC 20015, USA, and (9) Institute of Atmospheric Physics, Prague, Czech Republic, 14131 MESSENGER's 14 January 2008 encounter with Mercury has provided new observations of the solar wind interaction with this planet. Here we report initial results concerning this miniature magnetosphere's response to the north-south component of the interplanetary magnetic field (IMF). This is the component of the IMF that is expected to exert the greatest influence over the structure of the magnetopause and the processes responsible for energy transfer into the magnetosphere. The IMF was northward immediately prior to and following the passage of the MESSENGER spacecraft through this small magnetosphere. However, several-minute episodes of southward IMF were observed in the magnetosheath during the inbound portion of the encounter. Evidence for reconnection at the dayside magnetopause in the form of welldeveloped flux transfer events (FTEs) was observed in the magnetosheath following some of these southward-Bz intervals. The inbound magnetopause crossing in the magnetic field measurements is consistent with a transition from the magnetosheath into the plasma sheet. Immediately following MESSENGER's entry into the magnetosphere, rotational perturbations in the magnetic field similar to those seen at the Earth in association with large-scale plasma sheet vortices driven by Kelvin-Helmholtz waves along the magnetotail boundary at the Earth are observed. The outbound magnetopause occurred during northward IMF Bz and had the characteristics of a tangential discontinuity. These new observations have important implications for our understanding of energy transfer into Mercury's magnetosphere.

Slavin, James

107

Magnetopause shape as a bivariate function of interplanetary magnetic field B(sub z) and solar wind dynamic pressure  

NASA Technical Reports Server (NTRS)

We present a new method for determining the shape of the magnetopause as a bivariate function of the hourly averaged solar wind dynamic pressure (p) and the north-south component of the interplanetary magnetic field (IMF) B(sub z). We represent the magnetopause (for X(sub GSE) greater than -40 R(sub E)) as an ellipsoid of revolution in solar-wind-aberrated coordinates and express the (p, B(sub z)) dependence of each of the three ellipsoid parameters as a second-order (6-term) bivariate expansion in Inp and B(sub z). We define 12 overlapping bins in a normalized dimensionless (p, B(sub z)) `control space' and fit an ellipsoid to those magnetopause crossings having (p, B(sub z)) values within each bin. We also calculate the bivariate (Inp, B(sub z)) moments to second order over each bin in control space. We can then calculate the six control-space expansion coefficients for each of the three ellipsoid parameters in configuration space. From these coefficients we can derive useful diagnosis of the magnetopause shape as joint functions of p and B(sub z): the aspect ratio of the ellipsoid's minor-to-major axes; the flank distance, radius of curvature, and flaring angle (at X(sub GSE) = 0); and the subsolar distance and radius of curvature. We confirm and quantify previous results that during periods of southward B(sub z) the subsolar magnetopause moves inward, while at X(sub GSE) = 0 the flank magnetopause moves outward and the flaring angle increases.

Roelof, Edmond C.; Sibeck, David G.

1993-01-01

108

Interplanetary medium data book, supplement, 1975 - 1978  

NASA Technical Reports Server (NTRS)

Since the issurance of the Interplanetary Medium Data Book (NSSDC/WDC-A-R&S 77-04, 1977) which contains plots and listings of hourly average interplanetary field and plasma parameters covering the period November 27, 1963 through December 30, 1975, additional data are available which fill some 1975 data gaps and which extend the data coverage well into 1978. This supplement contains all the presently available data for the years 1975-1978, Interplanetary magnetic field (IMF) data are from the IMP 8 triaxial fluxgate magnetometer experiment. Derived plasma parameters are form the IMP 7 and IMP 8 instruments. Some of the early 1975 IMF data are from a HEOS 1 experiment.

King, J. H.

1979-01-01

109

Preliminary testing of global hybrid-Vlasov simulation: Magnetosheath and cusps under northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Global magnetohydrodynamic (MHD) simulations have been successful in describing systems where the important spatial scales are larger than ion inertial length and the plasma has a well-defined temperature. The weakness of global one-fluid MHD simulations is their inability to model the multi-temperature, multi-component plasmas in the inner magnetosphere, where most of space-borne technology, including communication and navigation systems reside. We are developing a global hybrid-Vlasov simulation, where electrons are MHD fluid, but protons are modeled as distribution functions evolved in time using the Vlasov equation. This approach does not include the noise present in kinetic-hybrid simulations, but is computationally extremely challenging requiring petascale computations with thousands of cores. Here, we briefly review the status of our new parallel six-dimensional Vlasov solver. We carry out a test particle simulation and propagate the distribution functions using the electromagnetic fields of the GUMICS-4 global MHD simulation. Our main goal is to test the Vlasov solver in a global setup against the standalone GUMICS-4 global MHD simulation. The results shown here are obtained during due northward interplanetary magnetic field (IMF). We find that the magnetosheath and magnetopause plasma properties from the test particle simulation are in rough agreement with the results from the GUMICS-4 simulation. Furthermore, we show that the cusp injection patterns reproduce the expected behavior of northward IMF. The results indicate that our solver behaves sufficiently well, indicating that global hybrid-Vlasov simulations of this kind are feasible, promising improved global simulation capabilities in the future.

Palmroth, M.; Honkonen, I.; Sandroos, A.; Kempf, Y.; von Alfthan, S.; Pokhotelov, D.

2013-07-01

110

Preliminary testing of global hybrid-Vlasov simulation: Magnetosheath and cusps under northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Global magnetohydrodynamic (MHD) simulations have been successful in describing systems where the important spatial scales are larger than ion inertial length and the plasma has a well-defined temperature. The weakness of global one-fluid MHD simulations is their inability to model the multi-temperature, multi-component plasmas in the inner magnetosphere, where most of space-borne technology, including communication and navigation systems reside. We are developing a global hybrid-Vlasov simulation, where electrons are MHD fluid, but protons are modeled as distribution functions evolved in time using the Vlasov equation. This approach does not include the noise present in kinetic-hybrid simulations, but is computationally extremely challenging requiring petascale computations with thousands of cores. Here, we briefly review the status of our new parallel six-dimensional Vlasov solver. We carry out a test particle simulation and propagate the distribution functions using the electromagnetic fields of the GUMICS-4 global MHD simulation. Our main goal is to test the broad features of the Vlasov solver in a global setup against the standalone GUMICS-4 global MHD simulation. The results shown here are obtained during due northward interplanetary magnetic field (IMF). We find that the magnetosheath and magnetopause plasma properties from the test particle simulation are in rough agreement with the results from the GUMICS-4 simulation. Furthermore, we show that the cusp injection patterns reproduce the expected behavior of northward IMF. The results indicate that our solver behaves sufficiently well, indicating that global hybrid-Vlasov simulations of this kind are becoming possible, promising improved global simulation capabilities in the future.

Palmroth, M. M.; Honkonen, I. J.; Sandroos, A.; Kempf, Y.; von Alfthan, S.; Pokhotelov, D.

2012-12-01

111

Solar Sources and Geospace Consequences of Interplanetary Magnetic Clouds Observed During Solar Cycle 23  

NASA Technical Reports Server (NTRS)

We present results of a statistical investigation of 99 magnetic clouds (MCs) observed during 1995-2005. The MC-associated coronal mass ejections (CMEs) are faster and wider on the average and originate within +/-30deg from the solar disk center. The solar sources of MCs also followed the butterfly diagram. The correlation between the magnetic field strength and speed of MCs was found to be valid over a much wider range of speeds. The number of south-north (SN) MCs was dominant and decreased with solar cycle, while the number of north-south (NS) MCs increased confirming the odd-cycle behavior. Two-thirds of MCs were geoeffective; the Dst index was highly correlated with speed and magnetic field in MCs as well as their product. Many (55%) fully northward (FN) MCs were geoeffective solely due to their sheaths. The non-geoeffective MCs were slower (average speed approx. 382 km/s), had a weaker southward magnetic field (average approx. -5.2nT), and occurred mostly during the rise phase of the solar activity cycle.

Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Michalek, G.; Lepping, R. P.

2007-01-01

112

Observations of the interplanetary magnetic field between 0.46 and 1 A.U. by the Mariner 10 spacecraft. Ph.D. Thesis - Catholic Univ. of Am.  

NASA Technical Reports Server (NTRS)

Almost continuous measurement of the interplanetary magnetic field (IMF) at a sampling rate of 25 vectors/sec was performed by the magnetic field experiment onboard the Mariner 10 spacecraft during the period November 3, 1973 to April 14, 1974, comprising approximately 5-2/3 solar rotations and extending in radial distance from the sun from 1 to 0.46 AU. A clearly discernible two-sector pattern of field polarity was observed during the last 3-1/2 months of the period, with the dominant polarity toward the sun below the solar equatorial plane. Two compound high-speed solar wind streams were also present during this period, one in each magnetic field sector. Relative fluctuations of the field in magnitude and direction were found to have large time variations, but on average the relative magnitude fluctuations were approximately constant over the range of heliocentric distance covered while the relative directional fluctuations showed a slight decrease on average with increasing distance. The occurrence rate of directional discontinuities was also found to decrease with increasing radial distance from the sun.

Behannon, K. W.

1976-01-01

113

Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?  

NASA Astrophysics Data System (ADS)

Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant "turbulence" created by the Alfvén wave dissipation is quite complex. There are both propagating (waves) and nonpropagating (mirror mode structures and MDs) byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the "turbulence" is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1AU from the Sun. A steepening rate of ~35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse) shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunward side of corotating interaction regions (CIRs). Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in this exciting new area.

Tsurutani, B. T.; Lakhina, G. S.; Pickett, J. S.; Guarnieri, F. L.; Lin, N.; Goldstein, B. E.

2005-02-01

114

Response of the Geosynchronous Magnetic Field at the Sub-solar Region to Variations in Interplanetary Magnetic Field Orientations and Changes in Solar Wind Dynamic Pressure  

NASA Astrophysics Data System (ADS)

The magnetic fields Ht at the geosynchronous orbit near the dayside sub-solar region are compared with the up-stream solar wind dynamic pressure (Dp) and north-south component of interplanetary field (Bz) in GSM coordinates based on the 90-second resolution of data observed by WIND, ACE, GOES 8 and 10 satellites for the period 1999-2000. The corrections due to the changes of the latitudinal positions of GOES have been made. There are at most two events selected (one for each GOES) each day when GOES 8 and 10 reach their maximum values of magnetic field strength near the sub-solar region. A total of 507 events are selected such that the up-stream solar wind and IMF data are carefully compared with GOES data so that a proper adjustment for the time delay due to solar-wind propagation from the upstream positions to that of GOES is included. It is found that the well-known results of Ht = a*sqrt(Dp)+b are confirmed for both polarity of Bz where a=30.2, b= 80.2, Ht in nT and Dp in nPa. However, the reduction in Ht due to the negative Bz is not found in our statistical study. Using the magnetopause model of Chao et al. (2002) and Shue et al. (1998), we estimate that the sub-solar distance of the magnetopause, Rmp, reduces about 1 Re on the average for southward Bz when Rmp is in the range of 7 to 10 Re.

Chao, J. K.; Dmitriev, A. V.; Yang, Y. H.

2003-12-01

115

Interplanetary magnetic field By control of prompt total electron content increases during superstorms  

NASA Astrophysics Data System (ADS)

Large magnitude increases in ionospheric total electron content (TEC) that occur over 1-3 h on the dayside are a significant manifestation of the main phases of superstorms. For the largest superstorms of solar cycle 23 (based on the Dst index), ground networks of GPS receivers measured peak total electron content increases greater than a factor of 2 relative to quiet time TEC averaged over the broad latitude band ±40° for local times 1200-1600 LT. Near 30° latitude, the Halloween storms of October 29-30, 2003 appeared to produce storm-time TEC exceeding quiet time values by a factor of 5 within 2-3 h of storm onset, at 1300 LT. The physical cause of these large positive phase ionospheric storms is usually attributed to prompt penetration electric fields (PPEFs) initiated by Region 1 current closure through the ionosphere (Nopper and Carovillano, 1978 mechanism). An unresolved question is what determines variation of the TEC response for different superstorms. It has been suggested that the cross polar cap potential and Region 1 currents are significant factors in determining PPEF in the equatorial ionosphere, which are related to the solar wind reconnection electric field estimated by Kan-Lee and others. In this paper, we show evidence that suggests By may be a significant factor controlling the TEC response during the main phase of superstorms. We analyzed the interplanetary conditions during the period that TEC was increasing for eight superstorms. We find that increasing daytime TEC during superstorms only occurs for large reconnection electric fields when By magnitude is less than Bz. The data suggest that Bz is a far more important factor in the TEC response than the reconnection electric field. We also find that TEC decreases following its peak storm-time value for two superstorms, even though Bz remains large and By magnitudes are less than Bz. Such decreases during the geomagnetic disturbance may indicate the role of magnetospheric shielding currents, or of changes in the thermosphere that have developed over the prolonged period of large solar wind electric field. Further analysis is warranted covering a wider range of storm intensities on the role of By in affecting the daytime TEC response for a range of storm intensities.

Mannucci, A. J.; Crowley, G.; Tsurutani, B. T.; Verkhoglyadova, O. P.; Komjathy, A.; Stephens, P.

2014-08-01

116

Interplanetary magnetic field dependency of stable sun-aligned polar cap arcs  

SciTech Connect

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed the authors had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with corresponding values of the IMF as measured by IMP 8 or ISEE 2. A well-defined dependence for B{sub z} is found for the presence/absence of stable Sun-aligned polar cap aurora steadily increases for larger positive values of B{sub z}, and linearly decreases when B{sub z} becomes more negative. The probability of observing Sun-aligned arcs within the polar cap is determined to vary sharply as a function of the arc location; arcs were observed 40% of the time on the dawnside and only 10% on the duskside. This implies an overall probability of at least 40% for the whole polar cap. 20% of the arcs were observed during {open_quotes}southward IMF conditions,{close_quotes} but in fact under closer inspection were found to have been formed under northward IMF conditions; these {open_quotes}residual{close_quotes} positive B{sub z} arcs had a delayed residence time in the polar cap of about what would be expected after a north to south transition of B{sub z}. A firm dependence on B{sub y} is also found for both the orientation and the dawn-dusk direction of deviations from this orientation, depending primarily upon the location of the arc in corrected geomagnetic (CG) coordinates. The authors found that the arc direction of motion depended both on B{sub y} and the arc location of the polar cap. For a given value of B{sub y}, two well-defined regions (or cells) exist. 59 refs., 21 figs., 1 tab.

Valladares, C.E. [Boston College, Newton, MA (United States)] [Boston College, Newton, MA (United States); Carlson, H.C. Jr.; Fukui, K.

1994-04-01

117

The determination of interplanetary magnetic field polarities around sector boundaries using E greater than 2 keV electrons  

NASA Technical Reports Server (NTRS)

The determination of the polarities of interplanetary magnetic fields (whether the field direction is outward from or inward toward the sun) has been based on a comparison of observed field directions with the nominal Parker spiral angle. These polarities can be mapped back to the solar source field polarities. This technique fails when field directions deviate substantially from the Parker angle or when fields are substantially kinked. We introduce a simple new technique to determine the polarities of interplanetary fields using E greater than 2 keV interplanetary electrons which stream along field lines away from the sun. Those electrons usually show distinct unidirectional pitch-angle anisotropies either parallel or anti-parallel to the field. Since the electron flow direction is known to be outward from the sun, the anisotropies parallel to the field indicate outward-pointing, positive-polarity fields, and those anti-parallel indicate inward-pointing, negative-polarity fields. We use data from the UC Berkeley electron experiment on the International Sun Earth Explorer 3 (ISSE-3) spacecraft to compare the field polarities deduced from the electron data, Pe (outward or inward), with the polarities inferred from field directions, Pd, around two sector boundaries in 1979. We show examples of large (greater than 100 deg) changes in azimuthal field direction Phi over short (less than 1 hr) time scales, some with and some without reversals in Pe. The latter cases indicate that such large directional changes can occur in unipolar structures. On the other hand, we found an example of a change in Pe during which the rotation in Phi was less than 30 deg, indicating polarity changes in nearly unidirectional structures. The field directions are poor guides to the polarities in these cases.

Kahler, S.; Lin, R. P.

1994-01-01

118

Interplanetary magnetic field dependency of stable Sun-aligned polar cap arcs  

NASA Astrophysics Data System (ADS)

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed we had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with corresponding values of the IMF as measured by International Monitoring Platform (IMP) 8 or International Sun Earth Explorer (ISEE) 2. After demonstrating an unbiased data set with smooth normal distributions of events versus the dimensions of time, space, and IMF component, we examine IMF dependencies of the properties of the optical arcs. A well-defined dependence for B(sub z) is found for the presence/absence of stable Sun-aligned polar cap arcs. Consistent with previous statistical studies, the probability of observing polar cap aurora steadily increases for larger positive values of B(sub z), and linearly decreases when B(sub z) becomes more negative. The probability of observing Sun-aligned arcs within the polar cap is determined to vary sharply as a function of the arc location; arcs were observed 40% of the time on the dawnside and only 10% on the duskside. This implies an overall probability of at least 40% for the whole polar cap. 20% of the arcs were observed during 'southward IMF conditions,' but in fact under closer inspection were found to have been formed under northward IMF conditions; these 'residual' positive B(sub z) arcs ha d a delayed residence time in the polar cap of about what would be expected after a north to south transition of B(sub z). A firm dependence on B(sub y) is also found for both the orientation and the dawn-dusk direction of motion of the arcs. All the arcs are Sun-aligned to a first approximation, but present deviations from this orientation, depending primarily upon the location of the arc in corrected geomagnetic (CG) coordinates. The arcs populating the 06-12 and the 12-18 quadrants of the CG coordinate system point toward the cusp. The B(sub y) dependency of the arc alignment is consistent with a cusp displacement in local time according to the sign of B(sub y). We found that the arc direction of motion depended both on B(sub y) and the arc location within the polar cap. For a given value of B(sub y) two well-defined regions (or cells) exist. Within each cell the arcs move in the same direction toward the boundary between the cells. The arcs located in the duskside move dawnward; those in the dawnside move duskward. The relative size of these dusk and dawn regions (or cells) are controlled by the magnitude of B(sub y). This persistent dusk-dawn motion fo the polar cap arcs is interpreted in terms of newly open flux tubes entering the polar cap and exerting a displacement of the convective cells and the polar cap arcs that are embedded within them.

Valladares, C. E.; Carlson, H. C., Jr.; Fukui, K.

1994-04-01

119

Interplanetary magnetic field dependency of stable Sun-aligned polar cap arcs  

NASA Technical Reports Server (NTRS)

This is the first analysis, using a statistically significant data set, of the morphological dependence of the presence, orientation, and motion of stable sun-aligned polar cap arcs upon the vector interplanetary magnetic field (IMF). For the one winter season analyzed we had 1392 all-sky 630.0-nm images of 2-min resolution containing a total of 150 polar cap arcs, all with corresponding values of the IMF as measured by International Monitoring Platform (IMP) 8 or International Sun Earth Explorer (ISEE) 2. After demonstrating an unbiased data set with smooth normal distributions of events versus the dimensions of time, space, and IMF component, we examine IMF dependencies of the properties of the optical arcs. A well-defined dependence for B(sub z) is found for the presence/absence of stable Sun-aligned polar cap arcs. Consistent with previous statistical studies, the probability of observing polar cap aurora steadily increases for larger positive values of B(sub z), and linearly decreases when B(sub z) becomes more negative. The probability of observing Sun-aligned arcs within the polar cap is determined to vary sharply as a function of the arc location; arcs were observed 40% of the time on the dawnside and only 10% on the duskside. This implies an overall probability of at least 40% for the whole polar cap. 20% of the arcs were observed during 'southward IMF conditions,' but in fact under closer inspection were found to have been formed under northward IMF conditions; these 'residual' positive B(sub z) arcs ha d a delayed residence time in the polar cap of about what would be expected after a north to south transition of B(sub z). A firm dependence on B(sub y) is also found for both the orientation and the dawn-dusk direction of motion of the arcs. All the arcs are Sun-aligned to a first approximation, but present deviations from this orientation, depending primarily upon the location of the arc in corrected geomagnetic (CG) coordinates. The arcs populating the 06-12 and the 12-18 quadrants of the CG coordinate system point toward the cusp. The B(sub y) dependency of the arc alignment is consistent with a cusp displacement in local time according to the sign of B(sub y). We found that the arc direction of motion depended both on B(sub y) and the arc location within the polar cap. For a given value of B(sub y) two well-defined regions (or cells) exist. Within each cell the arcs move in the same direction toward the boundary between the cells. The arcs located in the duskside move dawnward; those in the dawnside move duskward. The relative size of these dusk and dawn regions (or cells) are controlled by the magnitude of B(sub y). This persistent dusk-dawn motion fo the polar cap arcs is interpreted in terms of newly open flux tubes entering the polar cap and exerting a displacement of the convective cells and the polar cap arcs that are embedded within them.

Valladares, C. E.; Carlson, H. C., Jr.; Fukui, K.

1994-01-01

120

Pulsating dayside aurora in relation to ion upflow events during a northward interplanetary magnetic field (IMF) dominated by a strongly negative IMF BY  

Microsoft Academic Search

We report a study of ion upflow as seen by the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR), initiated by a rotation from interplanetary magnetic field (IMF) BZ negative to IMF BZ positive, under the influence of a strongly negative IMF BY. We combine ground-based instruments, such as meridian scanning photometers (MSP), all-sky imager (ASI) data, and radars, with solar

D. A. Lorentzen; P. M. Kintner; J. Moen; F. Sigernes; K. Oksavik; Y. Ogawa; J. Holmes

2007-01-01

121

The Parker spiral configuration of the interplanetary magnetic field between 1 and 8.5 AU  

NASA Technical Reports Server (NTRS)

The magnetic field data from the Pioneer 10 and 11 spacecraft show that the field directions between 1 and 8.5 AU are in accordance with the Parker spiral directions within quiet and interaction regions. The included angle between the inward and outward sectored field directions is near 180 deg; the field direction manifests greater variability in quiet regions than in interaction zones. The fractional polarities below 10 deg heliographic latitude are dominated by temporal variations; however, dual-spacecraft investigations permitted a significant latitudinal gradient to be extracted. The sector structure extended occasionally to 16 deg heliographic latitude during the period of average current sheet inclination in 1976; it is proposed that the fast streams associated with interaction regions may move the current sheet to higher latitudes when the source of the fast plasma is in the southern solar hemisphere.

Thomas, B. T.; Smith, E. J.

1980-01-01

122

Three-dimensional numerical simulation of interplanetary magnetic field changes at 1 AU as a consequence of simulated solar flares  

NASA Technical Reports Server (NTRS)

In order to study the relationship between different forms of activity and transient variations of the north-south component, B(sub z), of the Interplanetary Magnetic Field (IMF), at 1 AU, a three dimensional numerical simulation code was employed to study several aspects of this problem. One form of solar activity, the flare, is simulated by using a pressure pulse at different locations near the solar surface and observing the simulated IMF evolution of B(sub theta)(-B(sub z)) at 1 AU. It was found, for a given pressure pulse, that the orientation of the corresponding transient variation of B(sub z) has a strong relationship with the location of the pressure pulse and the initial condition of IMF.

Wu, S. T.; Wu, Chin-Chun; Dryer, Murray

1992-01-01

123

Geospace magnetic field responses to interplanetary shocks J. B. Liu,1  

E-print Network

) in the solar wind Pd always result in increases (decreases) in the geosynchronous magnetic field strength local magnetic field. As the magnitude of the upstream solar wind dynamic pressure increases, the rate [1997] investigated the effects of inter- planetary magnetic field (IMF) z component and the solar wind

Richardson, John

124

Dynamical evolution of interplanetary magnetic fields and flows between 0.3 AU and 8.5 AU: Entrainment  

NASA Technical Reports Server (NTRS)

The radial evolution of interplanetary flows and associated magnetic fields between 0.3 AU and 8.5 was analyzed using data from Helios 1 and Voyager 1, respectively. During a 70 day interval Voyager 1 observed two streams which appeared to be recurrent and which had little fine structure. The corresponding flows observed by Helios 1 were much more complex, showing numerous small streams, transient flows and shocks as well as a few large corotating streams. It is suggested that in moving to 8 AU the largest corotating streams swept up the slower flows (transient and/or corotating streams) and shocks into a relatively thin region in which they coalesced to form a single large amplitude compression wave. This combined process of sweeping and coalescence is referred to as entrainment. The resulting large amplitude compression wave is different from that formed by the steepening of a corotating stream from a coronal hole, because different flows from distinct sources, with possibly different composition and magnetic polarity, are brought together to form a single new structure.

Burlaga, L. F.; Schwenn, R.; Rosenbauer, H.

1983-01-01

125

A deployable high temperature superconducting coil (DHTSC) - A novel concept for producing magnetic shields against both solar flare and Galactic radiation during manned interplanetary missions  

NASA Technical Reports Server (NTRS)

The discovery of materials which are superconducting above 100 K makes possible the use of superconducting coils deployed beyong the hull of an interplanetary spacecraft to produce a magnetic shield capable of giving protection not only against solar flare radiation, but also even against Galactic radiation. Such deployed coils can be of very large size and can thus achieve the great magnetic moments required using only relatively low currents. Deployable high-temperature-superconducting coil magnetic shields appear to offer very substantial reductions in mass and energy compared to other concepts and could readily provide the radiation protection needed for a Mars mission or space colonies.

Cocks, F. Hadley

1991-01-01

126

Interplanetary medium data book: Supplement 3A, 1977-1985  

SciTech Connect

Supplement 3 of the Interplanetary Medium Data Book contains a detailed discussion of a data set compilation of hourly averaged interplanetary plasma and magnetic field parameters. The discussion addresses data sources, systematic and random differences, time shifting of ISEE 3 data, and plasma normalizations. Supplement 3 also contains solar rotation plots of field and plasma parameters. Supplement 3A contains computer-generated listings of selected parameters from the composite data set. These parameters are bulk speed (km/sec), density (per cu cm), temperature (in units of 1000 K) and the IMF parameters: average magnitude, latitude and longitude angles of the vector made up of the average GSE components, GSM Cartesian components, and the vector standard deviation. The units of field magnitude, components, and standard deviation are gammas, while the units of field direction angles and degrees.

Couzens, D.A.; King, J.H.

1986-04-01

127

Venus ionospheric tail rays - Spatial distributions and interplanetary magnetic field control  

NASA Technical Reports Server (NTRS)

The overall properties of Venus ionospheric tail rays (such as density, spatial extent, and distribution) and their relationship to the draped magnetic field configuration behind the planet were investigated using measurements obtained by the Pioneer Venus Orbiter Langmuir probe, a magnetometer, and a plasma-wave detector. The results suggest that tail rays are a normal feature of the steady solar wind interaction with Venus and are not generally associated with a central tail plasma sheet. The statistics of the tail rays occurrence point toward the existence of a distributed terminator ionosphere source, consistent with findings of Brace et al. (1990).

Ong, M.; Luhmann, J. G.; Russell, C. T.; Strangeway, R. J.; Brace, L. H.

1991-01-01

128

Using Statistical Multivariable Models to Understand the Relationship Between Interplanetary Coronal Mass Ejecta and Magnetic Flux Ropes  

NASA Technical Reports Server (NTRS)

In-situ measurements of interplanetary coronal mass ejections (ICMEs) display a wide range of properties. A distinct subset, "magnetic clouds" (MCs), are readily identifiable by a smooth rotation in an enhanced magnetic field, together with an unusually low solar wind proton temperature. In this study, we analyze Ulysses spacecraft measurements to systematically investigate five possible explanations for why some ICMEs are observed to be MCs and others are not: i) An observational selection effect; that is, all ICMEs do in fact contain MCs, but the trajectory of the spacecraft through the ICME determines whether the MC is actually encountered; ii) interactions of an erupting flux rope (PR) with itself or between neighboring FRs, which produce complex structures in which the coherent magnetic structure has been destroyed; iii) an evolutionary process, such as relaxation to a low plasma-beta state that leads to the formation of an MC; iv) the existence of two (or more) intrinsic initiation mechanisms, some of which produce MCs and some that do not; or v) MCs are just an easily identifiable limit in an otherwise corntinuous spectrum of structures. We apply quantitative statistical models to assess these ideas. In particular, we use the Akaike information criterion (AIC) to rank the candidate models and a Gaussian mixture model (GMM) to uncover any intrinsic clustering of the data. Using a logistic regression, we find that plasma-beta, CME width, and the ratio O(sup 7) / O(sup 6) are the most significant predictor variables for the presence of an MC. Moreover, the propensity for an event to be identified as an MC decreases with heliocentric distance. These results tend to refute ideas ii) and iii). GMM clustering analysis further identifies three distinct groups of ICMEs; two of which match (at the 86% level) with events independently identified as MCs, and a third that matches with non-MCs (68 % overlap), Thus, idea v) is not supported. Choosing between ideas i) and iv) is more challenging, since they may effectively be indistinguishable from one another by a single in-situ spacecraft. We offer some suggestions on how future studies may address this.

Riley, P.; Richardson, I. G.

2012-01-01

129

Source Regions of the Interplanetary Magnetic Field and Variability in Heavy-Ion Elemental Composition in Gradual Solar Energetic Particle Events  

NASA Technical Reports Server (NTRS)

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass-ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. But an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the PFSS model to map the Sun-L1 interplanetary magnetic field (IMF) line back to its source region on the Sun at the time of the SEP observations; and (2) then look for correlation between SEP composition (as measured by Wind and ACE at approx. 2-30 MeV/nucleon) and characteristics of the identified IMF-source regions. The study is based on 24 SEP events, identified as a statistically-significant increase in approx. 20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly-emergent solar magnetic flux and CMEs was lower than in solar-maximum years and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF-source, with the largest enhancements occurring when the footpoint field is strong, due to the nearby presence of an active region. In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering, at least on average, similar to that found in impulsive events. These results lead us to suggest that magnetic reconnection in footpoint regions near active regions bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events. To address potential technical concerns about our analysis, we also discuss efforts to exclude impulsive SEP events from our event sample.

Ko, Yuan-Kuen; Tylka, Allan J.; Ng, Chee K.; Wang, Yi-Ming; Dietrich, William F.

2013-01-01

130

Source Regions of the Interplanetary Magnetic Field and Variability in Heavy-Ion Elemental Composition in Gradual Solar Energetic Particle Events  

NASA Astrophysics Data System (ADS)

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass-ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. But an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the PFSS model to map the Sun-L1 interplanetary magnetic field (IMF) line back to its source region on the Sun at the time of the SEP observations; and (2) then look for correlation between SEP composition (as measured by Wind and ACE at ~2-30 MeV/nucleon) and characteristics of the identified IMF-source regions. The study is based on 24 SEP events, identified as a statistically-significant increase in ~20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly-emergent solar magnetic flux and CMEs was lower than in solar-maximum years and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF-source, with the largest enhancements occurring when the footpoint field is strong, due to the nearby presence of an active region. In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering, at least on average, similar to but less pronounced than that found in impulsive events. These results lead us to suggest that magnetic reconnection in footpoint regions near active regions bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events.

Tylka, Allan J.; Ko, Yuan-Kuen; Keong Ng, Chee; Wang, Yi-Ming; Dietrich, William F.

2014-05-01

131

High average power magnetic modulator for metal vapor lasers  

DOEpatents

A three-stage magnetic modulator utilizing magnetic pulse compression designed to provide a 60 kV pulse to a copper vapor laser at a 4.5 kHz repetition rate is disclosed. This modulator operates at 34 kW input power. The circuit includes a step up auto transformer and utilizes a rod and plate stack construction technique to achieve a high packing factor.

Ball, Don G. (Livermore, CA); Birx, Daniel L. (Oakley, CA); Cook, Edward G. (Livermore, CA); Miller, John L. (Livermore, CA)

1994-01-01

132

Intervals of Radial Interplanetary Magnetic Fields at 1 AU, Their Association with Rarefaction Regions, and Their Apparent Magnetic Foot Points at the Sun  

NASA Astrophysics Data System (ADS)

We have examined 226 intervals of nearly radial interplanetary magnetic field orientations at 1 AU lasting in excess of 6 hr. They are found within rarefaction regions as are the previously reported high-latitude observations. We show that these rarefactions typically do not involve high-speed wind such as that seen by Ulysses at high latitudes during solar minimum. We have examined both the wind speeds and the thermal ion composition before, during and after the rarefaction in an effort to establish the source of the flow that leads to the formation of the rarefaction. We find that the bulk of the measurements, both fast- and slow-wind intervals, possess both wind speeds and thermal ion compositions that suggest they come from typical low-latitude sources that are nominally considered slow-wind sources. In other words, we find relatively little evidence of polar coronal hole sources even when we examine the faster wind ahead of the rarefaction regions. While this is in contrast to high-latitude observations, we argue that this is to be expected of low-latitude observations where polar coronal hole sources are less prevalent. As with the previous high-latitude observations, we contend that the best explanation for these periods of radial magnetic field is interchange reconnection between two sources of different wind speed.

Orlove, Steven T.; Smith, Charles W.; Vasquez, Bernard J.; Schwadron, Nathan A.; Skoug, Ruth M.; Zurbuchen, Thomas H.; Zhao, Liang

2013-09-01

133

INTERVALS OF RADIAL INTERPLANETARY MAGNETIC FIELDS AT 1 AU, THEIR ASSOCIATION WITH RAREFACTION REGIONS, AND THEIR APPARENT MAGNETIC FOOT POINTS AT THE SUN  

SciTech Connect

We have examined 226 intervals of nearly radial interplanetary magnetic field orientations at 1 AU lasting in excess of 6 hr. They are found within rarefaction regions as are the previously reported high-latitude observations. We show that these rarefactions typically do not involve high-speed wind such as that seen by Ulysses at high latitudes during solar minimum. We have examined both the wind speeds and the thermal ion composition before, during and after the rarefaction in an effort to establish the source of the flow that leads to the formation of the rarefaction. We find that the bulk of the measurements, both fast- and slow-wind intervals, possess both wind speeds and thermal ion compositions that suggest they come from typical low-latitude sources that are nominally considered slow-wind sources. In other words, we find relatively little evidence of polar coronal hole sources even when we examine the faster wind ahead of the rarefaction regions. While this is in contrast to high-latitude observations, we argue that this is to be expected of low-latitude observations where polar coronal hole sources are less prevalent. As with the previous high-latitude observations, we contend that the best explanation for these periods of radial magnetic field is interchange reconnection between two sources of different wind speed.

Orlove, Steven T.; Smith, Charles W.; Vasquez, Bernard J.; Schwadron, Nathan A. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Skoug, Ruth M. [Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 (United States); Zurbuchen, Thomas H.; Zhao Liang, E-mail: stx33@wildcats.unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: N.Schwadron@unh.edu, E-mail: rskoug@lanl.gov, E-mail: thomasz@umich.edu, E-mail: lzh@umich.edu [Department of Atmospheric, Oceanic and Space Science, University of Michigan, Ann Arbor, MI (United States)

2013-09-01

134

New evidence of the influence of the interplanetary magnetic field on middle-latitude surface atmospheric pressure  

NASA Astrophysics Data System (ADS)

For the polar regions, results have been published over several decades that indicate a meteorological response to the east-west component of the interplanetary magnetic field (IMF), By. Here we present evidence of a previously unrecognised influence of IMF on mid-latitude surface pressure. We examine the difference, ?p(By), between the mean surface pressure for high and low values of IMF By (e.g., By > 3nT and By < -3nT) using NCEP/NCAR reanalysis data in a 50 year interval (1963-2012) for the whole surface of the Earth at a resolution of 2.5 deg. in latitude and longitude. Similarly we find the difference, ?p(Bz), between the mean surface pressures for high and low values of the north-south component of the IMF, Bz. The Student t-test is used to assess the statistical significance of the results. Both ?p(By) and ?p(Bz) possess a significant mid-latitude wave structure. This structure circles the Earth with a wave number of about 4-5, and is similar in location and structure to the cyclones and anti-cyclones produced by the action of atmospheric Rossby waves on the jet stream. Our results indicate that the mechanism that produces atmospheric responses to IMF in the polar regions is also able to modulate pre-existing weather patterns at mid-latitudes. Our results also confirm those published by Burns et al. in 2008 (J. Geophys. Res. 113 - hereafter B08) who found a statistically-significant dependence of surface pressure variations on IMF By at Antarctic stations for 1995-2005, and at Arctic stations for 1999-2002 (around solar maximum). We extend this work to test whether ?p(By) is consistently positive in the Antarctic and negative in the Arctic over the interval 1963-2012. Lastly, we find a significant correlation of surface pressure with IMF Bz at middle to high latitudes, in contrast to a previous study in J. Geophys. Res. 112, in 2007, by Burns et al. (B07). This may be reconciled by recognising that the amplitude of ?p(Bz) is spatially dependent and that the largest values may not be expected to occur at Vostok, where the results of B07 were obtained. It has been proposed that the observed effect of IMF on the atmosphere occurs as a result of modulation of the current density of the atmospheric circuit via the interplanetary electric field, with subsequent changes in cloud dynamics. An investigation of the effect of (i) a time lag between the IMF and the surface pressure and of (ii) the spatial variation of ?p(By) and ?p(Bz) will be used to consider possible mechanisms that can account for our results.

Lam, M.; Chisham, G.; Freeman, M. P.

2012-12-01

135

Variations in the Spectral Slopes of Interplanetary Data  

NASA Astrophysics Data System (ADS)

Inferences on turbulence in interplanetary plasmas commonly depend on the slope of the power spectrum. We have studied the slopes of spectra of the interplanetary magnetic field and charged particles from the HISCALE and EPAM detectors on Ulysses and ACE and find that it is systematically nonstationary. As an example, when the spectra are estimated on time blocks varying between three hours and one day, the average slope on the ACE GSE By component is close to -5/3, but fluctuations about this average are not random. Using 1-minute data, the slopes made from three hour data blocks offset by one hour gives a new time series. Power spectra of these series have strong peaks that are probably gravity modes. Here we extend these calculations to vector--valued data. The eigenvalues of the spectral matrices have similar characteristics to the individual components but the eigenvectors, that describe relative delay and orientation, point to several distinct families of modes.

Thomson, D. J.; Lanzerotti, L. J.

2009-05-01

136

Radiation shielding of astronauts in interplanetary flights: the CREAM surveyor to Mars and the magnetic lens system for a spaceship  

Microsoft Academic Search

The radiation absorbed by astronauts during interplanetary flights is mainly due to cosmic rays of solar origin (SCR). In the most powerful solar flares the dose absorbed in few hours can exceed that cumulated in one year of exposition to the galactic component of cosmic rays (GCR). At energies above the minimum one needed to cross the walls of the

P. Spillantini; F. Taccetti; P. Papini; L. Rossi; M. Casolino

137

Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies  

NASA Technical Reports Server (NTRS)

Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The central polar cap (greater than approx. 80 magnetic latitude) antisunward wind speed is found to be a strong function of both solar and geomagnetic activity. The polar cap temperatures show variations in both solar and geomagnetic activity, with temperatures near 800 K for low K(sub p) and F(sub 10.7) and greater than about 2000 K for high K(sub p) and F(sub 10.7). The observed temperatures are significantly greater than those predicted by the mass spectrometer/incoherent scatter model for high activity conditions. Theoretical analysis based on the NCAR TIGCM indicates that the antisunward upper thermospheric winds, driven by upstream ion drag, basically 'coast' across the polar cap. The relatively small changes in wind velocity and direction within the polar cap are induced by a combination of forcing terms of commensurate magnitude, including the nonlinear advection term, the Coriolis term, and the pressure gradient force term. The polar cap thennospheric thermal balance is dominated by horizontal advection, and adiabatic and thermal conduction terms.

Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

1995-01-01

138

An extended study of the source, characteristics, and geoeffectiveness of the Interplanetary Magnetic Field Southward component at different distances from the Sun  

NASA Astrophysics Data System (ADS)

Most (~75%) long-duration, large-amplitude southward Interplanetary Magnetic field (IMF Bs) intervals are associated with well-defined solar wind structures such as ICMEs and CIRs. Here IMF Bs intervals unrelated to such solar wind structures at 1 AU are examined in detail using plasma and magnetic field data from ACE. We also extend our study of IMF Bs to different heliocentric distances and latitudes using data from Ulysses and Helios. Using ACE observations, we find that low-frequency Alfvén waves in the slow solar wind are a possible source of IMF Bs intervals (t > 3 hours, Bz < -5 nT), and that Alfvén wave-related Bs intervals are geoeffective. We find that the contribution of Bs intervals from ICMEs decreases significantly with radial distance due to their over-expansion. This means that CIR-related Bs intervals dominate at 5.3 AU.

Zhang, X.; Moldwin, M.; Steinberg, J. T.; Skoug, R. M.

2013-12-01

139

Survey of interplanetary shock characteristics  

NASA Astrophysics Data System (ADS)

We report on a comparison of more than one hundred interplanetary shocks observed by both the Wind and ACE spacecraft. For each event, we use single spacecraft analysis methods such as the full Rankine-Hugoniot jump relations and the simpler velocity and magnetic coplanarity techniques to determine the shock orientation, speed, and assorted mach numbers and angles. We present a comparison of the properties of the shocks as a function of the separation between the spacecraft to determine the accuracy of the analysis methods and the non-planarity of IP shocks. The accuracy of the derived shock parameters and the non-planarity of the shock fronts are quantified by comparing the observed shock transit time between the spacecraft with predicted transit times calculated from the derived shock properties. The average timing errors for a given analysis method is the same using the Wind or ACE dataset; The Ranking-Hugoniot method performs best, with an RMS timing error of two minutes. We have studied the non-planarity of the shocks by comparing the implied radius of curvature determined by the difference between the two derived normals with the separation of the spacecraft. The variation is consistent with a five-degree error in shock direction and a typical radius of curvature of 0.1-0.3 AU. The shock parameters are made available through an online database (1). (1) http://space.mit.edu/home/jck/shockdb/shockdb.html

Kasper, J. C.; Lazarus, A. J.; Szabo, A.; Ogilvie, K. W.; Skoug, R.; Steinberg, J. T.; Smith, C.

2005-12-01

140

The 17-22 October (1999) solar-interplanetary-geomagnetic event: Very intense geomagnetic storm associated with a pressure balance between interplanetary coronal mass ejection and a high-speed stream  

Microsoft Academic Search

Using observations from the Advanced Composition Explorer (ACE) magnetic field and plasma experiments, we investigate the magnetic, thermal, and dynamic pressure balance in the border of a high-speed stream (HSS) and an average-speed interplanetary coronal mass ejection (ICME) observed on 21-22 October (1999). We believe that the HSS compressed the ICME and intensified its internal southward magnetic field, resulting in

Alisson Dal Lago; Walter D. Gonzalez; Laura A. Balmaceda; Luis E. A. Vieira; Ezequiel Echer; Fernando L. Guarnieri; Jean Santos; Marlos R. da Silva; Alicia L. Clua de Gonzalez; Ranier Schwenn; Nelson J. Schuch

2006-01-01

141

Sector structure of the interplanetary magnetic field in the second half of the 19th century inferred from ground-based magnetometers  

NASA Astrophysics Data System (ADS)

Interplanetary magnetic field (IMF) polarities can be inferred in the pre-satellite era using Svalgaard-Mansurov effect, according to which different IMF directions lead to different geomagnetic variations at polar stations. Basing on this effect we propose a method to derive a sector structure of the IMF when only ground based data are available. Details of the method and results have been presented in our recent paper: Vokhmyanin, M. V., and D. I. Ponyavin (2012), Inferring interplanetary magnetic field polarities from geomagnetic variations, J. Geophys. Res., 117, A06102, doi:10.1029/2011JA017060. Using data from eight stations: Sitka, Sodankyla, Godhavn, Lerwick, Thule, Baker Lake, Vostok and Mirny, we reconstructed sector structure back to 1905. The quality of inferring from 1965 to 2005 ranges between 78% and 90% depending on the used set of stations. Our results show both high success rate and good agreement with the well-known Russell-McPherron and Rosenberg-Coleman effects. In the current study we applied the technique to historical data of Helsinki observatory where digital versions of hourly geomagnetic components are available from 1844 to 1897. Helsinki station stopped operates at the beginning of 20th century. Thus, to create a model describing the local Svalgaard-Mansurov effect we analyzed data from Nurmijarvi station located near the same region. The success rate of reconstruction from 1965 to 2005 is around 82%. So we assume that the IMF polarities obtained for the period 1869-1889 have sufficient quality. Inferred sector structure at this time consists of two sectors typically for all declining phases of solar activity cycle. Catalogue of IMF proxies seem to be important in analyzing structure and dynamics of solar magnetic fields in the past.; Left: Bartels diagram of IMF sector structure inferred from Helsinki data. Right: sunspot number indicating solar cycles.

Vokhmyanin, M.; Ponyavin, D. I.

2012-12-01

142

Magnetic field hourly averages from the Rome-GSFC experiment aboard Helios 1 and Helio 2  

NASA Technical Reports Server (NTRS)

Plots of all the hourly averages computed from the solar magnetic field measurements obtained during the mission are given separately for Helios 1 and Helios 2. The magnitude and the direction of the averaged field are plotted versus the number of solar rotations as seen from Helios, counted from launch.

Mariani, F.; Ness, N. F.; Bavassano, B.; Bruno, R.; Buccellato, R.; Burlaga, L. F.; Cantarano, S.; Scearce, C. S.; Terenzi, R.; Villante, U.

1987-01-01

143

Adiabatic and nonadiabatic responses of the radiation belt relativistic electrons to the external changes in solar wind dynamic pressure and interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

By removing the influences of 'magnetopause shadowing' (r0>6.6RE) and geomagnetic activities, we investigated statistically the responses of magnetic field and relativistic (>0.5MeV) electrons at geosynchronous orbit to 201 interplanetary perturbations during 6 years from 2003 (solar maximum) to 2008 (solar minimum). The statistical results indicate that during geomagnetically quiet times (HSYM ?-30nT, and AE<200nT), ~47.3% changes in the geosynchronous magnetic field and relativistic electron fluxes are caused by the combined actions of the enhancement of solar wind dynamic pressure (Pd) and the southward turning of interplanetary magnetic field (IMF) (?Pd>0.4 nPa, and IMF Bz<0 nT), and only ~18.4% changes are due to single dynamic pressure increase (?Pd >0.4 nPa, but IMF Bz>0 nT), and ~34.3% changes are due to single southward turning of IMF (IMF Bz<0 nT, but |?Pd|<0.4 nPa). Although the responses of magnetic field and relativistic electrons to the southward turning of IMF are weaker than their responses to the dynamic pressure increase, the southward turning of IMF can cause the dawn-dusk asymmetric perturbations that the magnetic field and the relativistic electrons tend to increase on the dawnside (LT~00:00-12:00) but decrease on the duskside (LT~13:00-23:00). Furthermore, the variation of relativistic electron fluxes is adiabatically controlled by the magnitude and elevation angle changes of magnetic field during the single IMF southward turnings. However, the variation of relativistic electron fluxes is independent of the change in magnetic field in some compression regions during the enhancement of solar wind dynamic pressure (including the single pressure increases and the combined external perturbations), indicating that nonadiabatic dynamic processes of relativistic electrons occur there. Acknowledgments. This work is supported by NSFC (grants 41074119 and 40604018). Liuyuan Li is grateful to the staffs working for the data from GOES 8-12 satellites and OMNI database in CDAWeb.

Li, L.

2013-12-01

144

Anomalous aspects of magnetosheath flow and of the shape and oscillations of the magnetopause during an interval of strongly northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

On 15 Feb. 1978, the orientation of the interplanetary magnetic field (IMF) remained steadily northward for more than 12 hours. The ISEE 1 and 2 spacecraft were located near apogee on the dawn side flank of the magnetotail. IMP 8 was almost symmetrically located in the magnetosheath on the dusk flank and IMP 7 was upstream in the solar wind. Using plasma and magnetic field data, we show the following: (1) the magnetosheath flow speed on the flanks of the magnetotail steadily exceeded the solar wind speed by 20 percent; (2) surface waves with approximately a 5-min period and very non-sinusoidal waveform were persistently present on the dawn magnetopause and waves of similar period were present in the dusk magnetosheath; and (3) the magnetotail ceased to flare at an antisunward distance of 15 R(sub E). We propose that the acceleration of the magnetosheath flow is achieved by magnetic tension in the draped field configuration for northward IMF and that the reduction of tail flaring is consistent with a decreased amount of open magnetic flux and a larger standoff distance of the subsolar magnetopause. Results of a three-dimensional magnetohydrodynamic simulation support this phenomenological model.

Chen, Sheng-Hsien; Kivelson, Margaret G.; Gosling, Jack T.; Walker, Raymond T.; Lazarus, Allan J.

1992-01-01

145

Correlation and Taylor scale variability in the interplanetary magnetic field fluctuations as a function of solar wind speed  

E-print Network

the correlation scale and the magnetic Taylor microscale of the solar wind as functions of the mean magnetic field to the mean magnetic field in both the slow (600 km/s) solar wind, but the Taylor/s) solar wind. The correlation scale, on the other hand, varies with angle from the mean magnetic field

Dasso, Sergio

146

Investigation of influence of hypomagnetic conditions closely similar to interplanetary magnetic filed on behavioral and vegetative reactions of higher mammals  

NASA Astrophysics Data System (ADS)

To study the influence of long being under reduced magnetic field on behavioral and vegetative reactions of higher mammals the white rat males were put into the 700-1000 times reduced geomagnetic field (50-70 nT) for 25 days. Such field was obtained by using automatic compensation of the horizontal and vertical components of the GMF at a frequencies up to 10 Hz by means of solenoids of the experimental magnetic system. Control animals were located in the same room under usual laboratory GMF conditions (52 uT). Two days before the experiment the behavioral reactions were studied in the "open field" by means of a set of tests, characterizing the level of emotionality, moving and orientational-investigative activities of the animals under conditions of unimpeded behavior. 60 white underbred rat males with the initial body mass of 200 g were divided into three clusters. Animals with average indices were selected for the experiment. We have judged behavioral reaction disturbances of the rats under hypomagnetic conditions using videotape recordings carried out in the entire course of the chronic experiment. According to the obtained results during the period of maximum activity (from 230 to 330 a.m.) the number of interrelations between the individuals increased appreciably for experimental rats including interrelations with aggressive character. This was real during all 25 days of observation. We observed a certain dynamics of this index differed from that of the control group. We have also analyzed the final period of observation from the 21th to the 25th days. In this period we studied the 24 hours' dynamics of interrelations which were noted during 5 minutes in every hour around the clock. In the control group the number of interrelation was at a constantly low level. For experimental animals the number of interrelations was higher in the night hours than in the day ones. Moreover it exceeded the similar indexes observed from the 1st to the 20th day. For example from 300 to 305 a.m. on the 23th day we recorded 27 contacts of aggressive character between the individuals. So, in hypomagnetic field conditions the irritability of the animals' central nervous system grows, that expresses itself in the increase of contacts of aggressive and non-aggressive character between the individuals. Also we have carried out the Spirman correlation analysis between studied indices of moving activity and chemiluminescence of blood plasma and urine, electrolytic composition of urine and muscles. For control animals the quantity of correlation connections between electrolyte concentrations in studied substrata was higher than for experimental animals. The physiological sense of these correlation connections is discussed.

Krivova, Natalie; Trukhanov, Kiril; Zamotshina, Tatyana; Zaeva, Olga; Khodanovich, Marina; Misina, Tatyana; Tukhvatulin, Ravil; Suhko, Valery

147

Estimation of average structural parameters of bitumens by 13C nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

The determination of the average molecular parameters of bitumens represents an important step in describing the skeletons of asphalt cements. A new investigation method is presented, based only on the analysis of 13C nuclear magnetic resonance (n.m.r.) data and molecular weights. This method is proved to be an efficient procedure to give independent parameters and to try to define a

Laurent Michon; Didier Martin; Jean-Pascal Planche; Bernard Hanquet

1997-01-01

148

Penetration of the interplanetary magnetic field B(sub y) magnetosheath plasma into the magnetosphere: Implications for the predominant magnetopause merging site  

NASA Technical Reports Server (NTRS)

Magnetosheath plasma peertated into the magnetospere creating the particle cusp, and similarly the interplanetary magnetic field (IMF) B(sub y) component penetrates the magnetopause. We reexamine the phenomenology of such penetration to investigate implications for the magnetopause merging site. Three models are popular: (1) the 'antiparallel' model, in which merging occurs where the local magnetic shear is largest (usually high magnetic latitude); (2) a tilted merging line passing through the subsolar point but extending to very high latitudes; or (3) a tilted merging line passing through the subsolar point in which most merging occurs within a few Earth radii of the equatorial plane and local noon (subsolar merging). It is difficult to distinguish between the first two models, but the third implies some very different predictions. We show that properties of the particle cusp imply that plasma injection into the magnetosphere occurs most often at high magnetic latitudes. In particular, we note the following: (1) The altitude of the merging site inferred from midaltitude cusp ion pitch angle dispersion is typically 8-12 R(sub E). (2) The highest ion energy observable when moving poleward through the cusp drops long before the bulk of the cusp plasma is reached, implying that ions are swimming upstream against the sheath flow shortly after merging. (3) Low-energy ions are less able to enter the winter cusp than the summer cusp. (4) The local time behavior of the cusp as a function of B(sub y) and B(sub z) corroborates predictions of the high-latitude merging models. We also reconsider the penetration of the IMF B(sub y) component onto closed dayside field lines. Our approach, in which closed field lines ove to fill in flux voids created by asymmetric magnetopause flux erosion, shows that strich subsolar merging cannot account for the observations.

Newell, Patrick T.; Sibeck, David G.; Meng, Ching-I

1995-01-01

149

Theory of the solar magnetic cycle wave in the diurnal variation of energetic cosmic rays: Physical basis of the anisotropy  

Microsoft Academic Search

It is proposed that the so-called 20-year wave in the diurnal variation of energetic cosmic rays is a consequence of the likely average odd symmetry of the interplanetary magnetic field about the solar equatorial plane. It is assumed that the magnetic field in each hemisphere of the solar magnetic cavity has the same average sense as the polar magnetic field

E. H. Levy

1976-01-01

150

Radio Tracking of Solar Energetic Particles through Interplanetary Space.  

PubMed

Energetic particles ejected from the sun generate radio waves as they travel out through the interplanetary medium. Satellite observations of this emission at long radio wavelengths provide a means of investigating properties of the interplanetary medium, including the gross magnetic field configuration over distances of 1 astronomical unit. Results of such observations are illustrated. PMID:17798539

Fainberg, J; Evans, L G; Stone, R G

1972-11-17

151

Macroscopic perturbations of the Interplanetary Magnetic Field (IMF) by P/Halley as seen by the Giotto magnetometer  

NASA Technical Reports Server (NTRS)

Giotto magnetic field data were used to analyze the macroscopic field structure in the vicinity of P/Halley. During the Giotto flyby at comet P/Halley the IMF showed a quite stable away polarity. Draping of magnetic field lines is clearly observed along the outbound leg of the trajectory. Inside the magnetic pile-up region the field reverses its polarity several times. A symmetry of oppositely magnetized sheets with respect to the nucleus is found and explained in terms of convected IMF features.

Raeder, J.; Neubauer, F. M.; Ness, N.; Burlaga, L. F.

1986-01-01

152

Comments concerning the origin of the Bz component of the interplanetary magnetic field and the geoefficiency index in Akasofu's model  

NASA Astrophysics Data System (ADS)

Calculations are presented supporting the hypothesis that singularities of the Bz component are localized along the magnetic flux tubes, this localization being due to the stretching of the solar magnetic field loops by the quasi-stationary solar wind. If this hypothesis is correct, Akasofu's (1979) hypothesis of the existence of a special slow epsilon-signal in the solar wind is unnecessary.

Pudovkin, M. I.; Poniavin, D. I.

1982-02-01

153

Pressure enhancement associated with meridional flow in high-speed solar wind: possible evidence for an interplanetary magnetic flux rope  

E-print Network

Pressure enhancement associated with meridional flow in high-speed solar wind: possible evidence. A sizable total-pressure (magnetic pressure plus kinetic pressure) enhancement was found within the high and the magnetic magnitude simultaneously increased for about 6 h. This pressure rise was associated

Paris-Sud XI, Université de

154

The First in situ Observation of Kelvin-Helmholtz Waves at High-Latitude Magnetopause during Strongly Dawnward Interplanetary Magnetic Field Conditions  

NASA Technical Reports Server (NTRS)

We report the first in situ observation of high-latitude magnetopause (near the northern duskward cusp) Kelvin-Helmholtz waves (KHW) by Cluster on January 12, 2003, under strongly dawnward interplanetary magnetic field (IMF) conditions. The fluctuations unstable to Kelvin-Helmholtz instability (KHI) are found to propagate mostly tailward, i.e., along the direction almost 90 deg. to both the magnetosheath and geomagnetic fields, which lowers the threshold of the KHI. The magnetic configuration across the boundary layer near the northern duskward cusp region during dawnward IMF is similar to that in the low-latitude boundary layer under northward IMF, in that (1) both magnetosheath and magnetospheric fields across the local boundary layer constitute the lowest magnetic shear and (2) the tailward propagation of the KHW is perpendicular to both fields. Approximately 3-hour-long periods of the KHW during dawnward IMF are followed by the rapid expansion of the dayside magnetosphere associated with the passage of an IMF discontinuity that characterizes an abrupt change in IMF cone angle, Phi = acos (B(sub x) / absolute value of Beta), from approx. 90 to approx. 10. Cluster, which was on its outbound trajectory, continued observing the boundary waves at the northern evening-side magnetopause during sunward IMF conditions following the passage of the IMF discontinuity. By comparing the signatures of boundary fluctuations before and after the IMF discontinuity, we report that the frequencies of the most unstable KH modes increased after the discontinuity passed. This result demonstrates that differences in IMF orientations (especially in f) are associated with the properties of KHW at the high-latitude magnetopause due to variations in thickness of the boundary layer, and/or width of the KH-unstable band on the surface of the dayside magnetopause.

Hwang, K.-J.; Goldstein, M. L.; Kuznetsova, M. M.; Wang, Y.; Vinas, A. F.; Sibeck, D. G.

2012-01-01

155

Rigidity Dependence of the Long-Term Variations of Galactic Cosmic-Ray Intensity in Relation to the Interplanetary Magnetic-Field Turbulence: 1968 - 2002  

NASA Astrophysics Data System (ADS)

We studied the relationship between the power-law exponent ? on the rigidity R of the spectrum of galactic cosmic-ray (GCR) intensity variation ( ?D( R)/ D( R)? R - ? ) and the exponents ? y and ? z of the power spectral density (PSD) of the B y and B z components of the interplanetary magnetic field (IMF) turbulence (PSD˜ f - ? , where f is the frequency). We used the data from neutron monitors and IMF for the period of 1968 - 2002. The exponents ? y and ? z were calculated in the frequency interval ? f= f 2- f 1=3×10-6 Hz of the resonant frequencies ( f 1=1×10-6 Hz, f 2=4×10-6 Hz) that are responsible for the scattering of GCR particles with the rigidity range detected by neutron monitors. We found clear inverse correlations between ? and ? y or ? z when the time variations of the resonant frequencies were derived from in situ measurements of the solar wind velocity U sw and IMF strength B during 1968 - 2002. We argue that these inverse relations are a fundamental feature in the GCR modulation that is not restricted to the analyzed years of 1968 - 2002.

Siluszyk, M.; Iskra, K.; Alania, M. V.

2014-11-01

156

Influence of interplanetary solar wind sector polarity on the ionosphere  

NASA Astrophysics Data System (ADS)

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

liu, jing

2014-05-01

157

Solar magnetic fields and convection. IX - A primordial magnetic field  

Microsoft Academic Search

Observational evidence is reviewed in an attempt to decide between a reversing (dynamo) and a nonreversing primordial solar poloidal magnetic field. The data examined include Zeeman-effect measurements, measurements of gross magnetic fluxes in individual magnetic elements, determinations of average field strength, observations of polar-cap magnetic fields, eclipse observations of coronal structure, and observations of interplanetary-magnetic-field polarity reversals. It is suggested

J. H. Piddington

1977-01-01

158

Use of induction linacs with nonlinear magnetic drive as high average power accelerators  

SciTech Connect

The marriage of induction linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 Mev/meter, and with power efficiencies approaching 50%. A 2 MeV, 5 kA electron accelerator is under construction at Lawrence Livermore National Laboratory (LLNL) to allow us to demonstrate some of these concepts. Progress on this project is reported here.

Birx, D.L.; Cook, E.G.; Hawkins, S.A.; Newton, M.A.; Poor, S.E.; Reginato, L.L.; Schmidt, J.A.; Smith, M.W.

1984-08-20

159

Cusp/cleft auroral activity in relation to solar wind dynamic pressure, interplanetary magnetic field B(sub z) and B(sub y)  

NASA Technical Reports Server (NTRS)

Continuous optical observations of cusp/cleft auroral activities within approximately equal to 09-15 MLT and 70-76 deg magnetic latitude are studied in relation to changes in solar wind dynamic pressure and interplanetary magnetic field (IMF) variability. The observed latitudinal movements of the cusp/cleft aurora in response to IMF B(sub z) changes may be explained as an effect of a variable magnetic field intensity in the outer dayside magnetosphere associated with the changing intensity of region 1 field-aligned currents and associated closure currents. Ground magnetic signatures related to such currents were observed in the present case (January 10, 1993). Strong, isolated enhancements in solar wind dynamic pressure (Delta p/p is greater than or equal to 0.5) gave rise to equatorward shifts of the cusp/cleft aurora, characteristic auroral transients, and distinct ground magnetic signatures of enhanced convection at cleft latitudes. A sequence of auroral events of approximately equal to 5-10 min recurrence time, moving eastward along the poleward boundary of the persistent cusp/cleft aurora in the approximately equal to 10-14 MLT sector, during negative IMF B(sub z) and B(sub y) conditions, were found to be correlated with brief pulses in solar wind dynamic pressure (0.1 is less than Delta p/p is less than 0.5). Simultaneous photometer observations from Ny Alesund, Svalbard, and Danmarkshavn, Greenland, show that the events often appeared on the prenoon side (approximately equal to 10-12 MLT), before moving into the postnoon sector in the case we study here, when IMF B(sub y) is less than 0. In other cases, similar auroral event sequences have been observed to move westward in the prenoon sector, during intervals of positive B(sub y). Thus a strong prenoon/postnoon asymmetry of event occurence and motion pattern related to the IMF B(sub y) polarity is observed. We find that this category of auroral event sequence is stimulated bursts of electron precipitation that originate from magnetosheath plasma that has accessed that dayside magnetosphere in the noon or near-noon sector, possibly at high latitudes, partly governed by the IMF orientation as well as by solar wind dynamic pressure pulses.

Sandholt, P. E.; Farrugia, C. J.; Burlaga, L. F.; Holtet, J. A.; Moen, J.; Lybekk, B.; Jacobsen, B.; Opsvik, D.; Egeland, A.; Lepping, R.

1994-01-01

160

A rapid inversion and resolution analysis of magnetic microscope data by the subtractive optimally localized averages method  

NASA Astrophysics Data System (ADS)

Modern scanning magnetic microscopes have the potential for fine-scale magnetic investigations of rocks. Observations at high spatial resolution produce large volumes of data, and the interpretation of these data is a nontrivial task. We have developed software using an efficient magnetic inversion technique that explicitly constructs the spatially localized Backus-Gilbert averaging kernel. Our approach, using the subtractive optimally localized averages (SOLA) method (Pijpers, R.P., Thompson, M.J., 1992. Faster formulations of the optimally localized averages method for helioseismic inversions. Astronomy and Astrophysics 262, L33-L36), yield a unidirectional magnetization. The averaging kernel expresses the spatial resolution of the inversion and is valuable for paleomagnetic application of the scanning magnetic microscope. Inversion examples for numerical magnetization patterns are provided to exhibit the performance of the method. Examples of actual magnetic field data collected from thin sections of natural rocks measured with a magnetoimpedance (MI) magnetic microscope are also provided. Numerical tests suggest that the data-independent averaging kernel is desirable for a point-to-point comparison among multiple data. Contamination by vector magnetization components can be estimated by the averaging kernel. We conclude that the SOLA method is a useful technique for paleomagnetic and rock magnetic investigations using scanning magnetic microscopy.

Usui, Y.; Uehara, M.; Okuno, K.

2012-01-01

161

Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations: Determination of the ionospheric phase velocity  

SciTech Connect

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-hour interval in question IMF B[sub z] oscillates between [plus minus] 7 nT with about a 1-hour period. Corresponding variations in the ground magnetic disturbance are observed which the authors infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5[degrees] magnetic latitude, but separated by [approximately]2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector ([approximately]10 MLT) and then spread outward toward dawn and dusk with a phase speed of [approximately]5 km s[sup [minus]1] over the longitude range [approximately]8 to 12 MLT, slowing to [approximately] 2 km s[sup [minus]1] outside this range. Cross correlating the data from these ground stations with IMP 8 IMF B[sub z] records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds. The authors interpret these observations in terms of the ionospheric response to the onset, expansion and decay of magnetic reconnection at the dayside magnetopause.

Saunders, M.A.; Freeman, M.P.; Southwood, D.J.; Cowley, S.W.H. (Imperial College of Science, Technology and Medicine, London (United Kingdom)); Lockwood, M. (Rutherford Appleton Lab., Oxfordshire (United Kingdom)); Samson, J.C. (Univ. of Alberta, Edmonton (Canada)); Farrugia, C.J. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Hughes, T.J. (National Research Council of Canada, Ottawa, Ontario (Canada))

1992-12-01

162

An interplanetary planar magnetic structure oriented at a large (about 80 deg) angle to the Parker spiral  

NASA Technical Reports Server (NTRS)

Magnetic field structures in the solar wind, characterized by a variation of the field vectors within a plane inclined to the ecliptic ('Planar Magnetic Structures', PMSs), were reported recently (Nakagawa et al., 1989). These PMSs have the property that the plane of variation of the field also contains the nominal Parker spiral direction. An observation of a PMS where the direction of the line of intersection of the plane of field variation with the ecliptic plane makes a large (about 80 deg) angle to the Parker spiral direction is presented. Furthermore, the angular variables of the field (1) vary over a restricted range, and (2) are linearly related. The latter property is related to the former. Currently proposed models for the origin of PMS, inasmuch as they require field configurations which retain strict alignment with the Parker spiral direction from formation to observation, are probably incomplete.

Farrugia, M. W.; Dunlop, M. W.; Geurts, F.; Balogh, A.; Southwood, D. J.; Bryant, D. A.; Neugebauer, M.

1990-01-01

163

Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations - Determination of the ionospheric phase velocity  

NASA Technical Reports Server (NTRS)

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-h interval in question, IMF Bz oscillates between +/- 7 nT with about a 1-h period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5 deg magnetic latitude, but separated by about 2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (about 10 MLT) and then spread outward toward dawn and dusk with a phase speed of about 5 km/s over the longitude range about 8 to 12 MLT, slowing to about 2 km/s outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds.

Saunders, M. A.; Freeman, M. P.; Southwood, D. J.; Cowley, S. W.; Lockwood, M.; Samson, J. C.; Farrugia, C. J.; Hughes, T. J.

1992-01-01

164

The average configuration of the induced Venus magnetotail  

NASA Technical Reports Server (NTRS)

The interaction of the solar-wind flow with Venus is discussed as well as the morphology of magnetic-field-line draping in the Venus magnetotail. Emphasis is placed on the importance of the interplanetary magnetic field X-component in controlling the configuration of field draping in this induced magnetotail. The average magnetic configuration of this magnetotail is studied. A connection is made between the derived consistent plasma flow speed and density and the observational energy/charge range and sensitivity of the Pioneer Venus Orbiter plasma analyzer.

Mccomas, D. J.; Spence, H. E.; Russell, C. T.

1987-01-01

165

Implementing the Interplanetary Internet  

E-print Network

, 2002/2003. IRTF DTN research group set up. (Kevin introduces DTNRG at IETF 56, March 2003.) DARPA at each node #12;77Interplanetary Internet ­ Lloyd Wood What is the Bundle Protocol?What is the Bundle Protocol?What is the Bundle Protocol?What is the Bundle Protocol? Basically layer over different internets

Wood, Lloyd

166

Cosmic ray modulation by interplanetary disturbances  

NASA Astrophysics Data System (ADS)

Interplanetary disturbances such as ICMEs (Interplanetary Coronal Mass Ejections) and CIRs (Corotating Interaction Regions), modulate high-energy cosmic rays reaching the Earth. Prior to the arrival of the disturbances at the Earth, ground based high-energy muon detectors can detect precursory effects in cosmic-ray anisotropy, such as precursory deficit and/or excess of intensity along the sunward IMF (Interplanetary Magnetic Field) direction. With suitable analyses, these precursors are found typically around 8 hours prior to the disturbance arrival at the Earth. The objective of this work is to analyze these precursors by using the Global Muon Detector Network (GMDN), an international network formed by four multidirectional muon detectors viewing a full range of the pitch angle measured from the sunward IMF direction. By analyzing the variation of the count rate global distribution of the observed intensity (instead of analyzing the count rate) precursory signatures can be enhanced when compared with analyses of count rates. For some events, it is possible to make almost a global distribution map of cosmic ray density using all the directional channels of the detectors. Precursory signature is generally accompanied by the interplanetary shock, but there are also some signatures not associated with the shock.

Braga, Carlos Roberto; Dal Lago, Alisson; Schuch, Nelson Jorge; da Silva, Marlos; Echer, Ezequiel; Demítrio Gonzalez Alarcon, Walter; Munakata, Kazuoki; Kuwabara, Takao; Kato, Chihiro; Bieber, John W.

167

Averaging out magnetic forces with fast rf-sweeps in an optical trap for metastable chromium atoms  

E-print Network

We introduce a novel type of time-averaged trap, in which the internal state of the atoms is rapidly modulated to modify magnetic trapping potentials. In our experiment, fast radiofrequency (rf) linear sweeps flip the spin of atoms at a fast rate, which averages out magnetic forces. We use this procedure to optimize the accumulation of metastable chomium atoms into an optical dipole trap from a magneto-optical trap. The potential experienced by the metastable atoms is identical to the bare optical dipole potential, so that this procedure allows for trapping all magnetic sublevels, hence increasing by up to 80 percent the final number of accumulated atoms.

Q. Beaufils; R. Chicireanu; A. Pouderous; W. de Souza Melo; B. Laburthe-Tolra; E. Maréchal; L. Vernac; J. C. Keller; O. Gorceix

2007-11-05

168

Electron Distribution Functions Near Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

This paper examines the signatures of electron velocity distribution functions near several interplanetary shocks as observed by the Vector Electron Spectrometer on the WIND spacecraft. These interplanetary shocks are moderate in strength and have values of thetabn between 60 and 90 degrees. We concentrate on a quasi-perpendicular shock observed by WIND on August 26, 1998 which was associated with an interplanetary type II radio burst. WIND observations of this shock have previously been studied by Bale et al. [GRL, June 1, 1999] who found the first evidence for electron beams in the source region of a type II burst in the upstream region of this shock. Our focus will be on comparing the electron distribution functions before and after the WIND encounter with the shock, showing the evidence for electron acceleration and heating from the shapes of the distributions. In the upstream, loss cone and bump on tail distributions are observed that are characteristic of magnetic mirroring in the rising magnetic field of the shock layer. The dispersion in arrival times of the upstream electrons has been used to measure the distance along the magnetic field lines connecting the spacecraft and the shock. On traversing the shock layer from the upstream to the downstream, the distributions broaden, first in the direction perpendicular to the magnetic field, followed by broadening of the parallel distribution and the formation of parallel beams until the distribution is nearly isotropic. The downstream distributions of this shock, as well as several of the other stronger interplanetary shocks in this study, have the typical flat top signature of electron heating and the electron beams found immediately downstream of the Earth's bow shock. Observations by the WAVES experiment on WIND also show typical broadband, impulsive signatures in the shock. Further downstream the distributions again become slightly anisotropic with the perpendicular temperature exceeding the parallel. We compare the observed distributions with results of theoretical works, particularly the recent work of Hull et al. [JGR, August 1, 2001].

Ogilvie, K. W.; Fitzenreiter, R. J.; Bale, S. D.; Szabo, A.

2001-12-01

169

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

The logistical aspects of orbit determination (OD) in the interplanetary phase of the Mariner Mars 1971 mission are described and the working arrangements for the OD personnel, both within the Navigation Team and with outside groups are given. Various types of data used in the OD process are presented along with sources of the data. Functional descriptions of the individual elements of the OD software and brief sketches of their modes of operation are provided.

Zielenbach, J. W.; Acton, C. H.; Born, G. H.; Breckenridge, W. G.; Chao, C. C.; Duxbury, T. C.; Green, D. W.; Jerath, N.; Jordan, J. F.; Mottinger, N. A.

1973-01-01

170

Radioactivity in interplanetary dust  

Microsoft Academic Search

Most of the radioactivity in interplanetary dust in the region of the Earth's orbit results from interactions with solar protons. The most abundant nuclides having half-lives longer than a few hours in a dust of chondritic composition are Co56, Fe55, Al26, Mn53, Co55, C14, Na22, and Co57. The measurement of ratios of dust radionuclides can provide a means of measuring

John T. Wasson

1963-01-01

171

Anharmonic vibrational frequencies and vibrationally averaged structures and nuclear magnetic resonance parameters of FHF-.  

PubMed

The anharmonic vibrational frequencies of FHF(-) were computed by the vibrational self-consistent-field, configuration-interaction, and second-order perturbation methods with a multiresolution composite potential energy surface generated by the electronic coupled-cluster method with various basis sets. Anharmonic vibrational averaging was performed for the bond length and nuclear magnetic resonance indirect spin-spin coupling constants, where the latter computed by the equation-of-motion coupled-cluster method. The calculations placed the vibrational frequencies at 580 (nu(1)), 1292 (nu(2)), 1313 (nu(3)), 1837 (nu(1) + nu(3)), and 1864 cm(-1) (nu(1) + nu(2)), the zero-point H-F bond length (r(0)) at 1.1539 A, the zero-point one-bond spin-spin coupling constant [(1)J(0)(HF)] at 124 Hz, and the bond dissociation energy (D(0)) at 43.3 kcal/mol. They agreed excellently with the corresponding experimental values: nu(1) = 583 cm(-1), nu(2) = 1286 cm(-1), nu(3) = 1331 cm(-1), nu(1) + nu(3) = 1849 cm(-1), nu(1) + nu(2) = 1858 cm(-1), r(0) = 1.1522 A, (1)J(0)(HF) = 124+/-3 Hz, and D(0) = 44.4+/-1.6 kcal/mol. The vibrationally averaged bond lengths matched closely the experimental values of five excited vibrational states, furnishing a highly dependable basis for correct band assignments. An adiabatic separation of high- (nu(3)) and low-frequency (nu(1)) stretching modes was examined and found to explain semiquantitatively the appearance of a nu(1) progression on nu(3). Our calculations predicted a value of 186 Hz for experimentally inaccessible (2)J(0)(FF). PMID:18537420

Hirata, So; Yagi, Kiyoshi; Perera, S Ajith; Yamazaki, Shiori; Hirao, Kimihiko

2008-06-01

172

High-precision, longitudinal, disc-averaged magnetic field measurements of ? Canis Minoris and ? Leporis.  

NASA Astrophysics Data System (ADS)

High-precision longitudinal, disc-averaged magnetic field measurements have been made on two late-type stars, ? CMi (HR 2943) and ? Lep (HR 1829). A magneto-optical filter has been used to measure the degree of circular polarization in the wings of a line of neutral potassium (7699 A) formed in the atmosphere of the target star. From 10 nights of data taken on ? CMi on the 1.9-m reflector at the South African Astronomical Observatory (SAAO) in 1993 January, an upper limit to any net longitudinal field component present - assuming the field to be constant over the period of observation - of -0.40+/-0.26G was established. Similarly, upper limits for ? Lep of -4.3+/-6.4G and -0.7+/-1.6G were established, from 4 and 10 nights of data taken in 1992 and 1993 January respectively. No significant, periodic, day-to-day variations were seen in the three time series of data.

Bedford, D. K.; Chaplin, W. J.; Davies, A. R.; Innis, J. L.; Isaak, G. R.; Speake, C. C.

1995-01-01

173

Interplanetary scintillation and Jovian DAM emission  

NASA Astrophysics Data System (ADS)

The influence of interplanetary scintillations (IPS) on Jovian decametric (DAM) emission (10-40 MHz) is studied on broad-band dynamic spectra, for the whole range of solar elongations. L-bursts are confirmed to be the result of IPS, and it is shown that they are broad-band bursts. This implies that IPS are correlated on the whole frequency range of observation. It is concluded from observations at conjunction that the intrinsic time scale of Jovian emission is either some milliseconds (S-bursts) or some minutes (arcs). On the other hand, when the elongation is about 130 deg east, a clear decrease in scintillation appears, which has already been observed by Erskine (1976). It is shown that this is a permanent feature of IPS. It could be interpreted as an effect of the interplanetary magnetic field in IPS.

Genova, F.; Leblanc, Y.

1981-05-01

174

Mercury's Time-Averaged and Induced Magnetic Fields from MESSENGER Observations  

NASA Astrophysics Data System (ADS)

Observations from MESSENGER's Magnetometer (MAG) have allowed the construction of a baseline, time-averaged model for Mercury's magnetosphere. The model, constructed with the approximation that the magnetospheric shape can be represented as a paraboloid, includes two external (magnetopause and magnetotail) current systems and an internal (dipole) field. We take advantage of the geometry of the orbital MAG data to constrain all but one of the model parameters, and their ranges, directly from the observations. These parameters are then used as a priori constraints in the magnetospheric model, and the remaining parameter, the dipole moment, is estimated from a grid search. The model provides an excellent fit to the MAG observations, with a root-mean-square misfit of less than 20 nT globally. The mean distance from the planetary dipole origin to the magnetopause subsolar point, RSS, is 1.45 RM (where RM = 2440 km) and the mean planetary dipole moment is 190 nT- RM3. Temporal variations in the global-scale magnetic fields result from changes in solar wind ram pressure, Pram, at Mercury that arise from the planet's 88-day eccentric orbit around the Sun and from transient, rapid changes in solar wind conditions. For a constant planetary dipole moment, RSS varies as Pram-1/6. However, magnetopause crossings obtained from several Mercury years of MESSENGER observations indicate that RSS is proportional to Pram-1/a where a is greater than 6, suggesting induction in Mercury's highly conducting metallic interior. We obtain an effective dipole moment that varies by up to ?15% about its mean value. We further investigate the periodic 88-day induction signature and use the paraboloid model to describe the spatial structure in the inducing magnetopause field, together with estimates for the outer radius of Mercury's liquid core and possible overlying solid iron sulfide layer, to calculate induced core fields. The baseline magnetospheric model is adapted to include the 88-day periodic induction signature, and residuals to this time-varying global model from magnetically quiet orbits are then used to investigate structure at higher degree and order in the internal and external fields.

Johnson, C. L.; Winslow, R. M.; Anderson, B. J.; Purucker, M. E.; Korth, H.; Al Asad, M. M.; Slavin, J. A.; Baker, D. N.; Hauck, S. A.; Phillips, R. J.; Zuber, M. T.; Solomon, S. C.

2012-12-01

175

Cosmic ray scintillations. II - General theory of interplanetary scintillations  

NASA Technical Reports Server (NTRS)

The motion of charged particles in a stochastic magnetic field with nonzero mean is considered via a generalized quasi-linear expansion of Liouville's equation. The general result is an equation relating cosmic ray scintillations to magnetic fluctuations and to cosmic ray gradients. The resonant interaction between particles and the random magnetic field is considered in detail, and the effect of nonlinear terms in the equations is considered. The nonlinear terms are important in damping out initial conditions and in determining conditions near cyclotron resonances. The application of the theory to the propagation of cosmic rays during quiet times in interplanetary space is considered. It is concluded that cosmic ray scintillations in interplanetary space may provide useful information about interplanetary particles and fields and also about nonlinear plasma interactions.

Owens, A. J.

1974-01-01

176

Interplanetary medium dust - dusty plasma ?  

Microsoft Academic Search

Measurements from spacecraft provide the only opportunity for in-situ studies of cosmic dusty plasmas and the most extended target for measurements is the interplanetary medium filled with cosmic dust and solar wind plasma Though the interplanetary medium does not provide a dusty plasma according to its proper definition dusty plasma conditions may locally apply Moreover dust plasma interactions in the

I. Mann

2006-01-01

177

Radio tracking of solar energetic particles through interplanetary space.  

NASA Technical Reports Server (NTRS)

Satellite observations of traveling solar radio bursts provide information about the propagation of energetic solar particles through interplanetary space. This information leads to data on the solar wind density and gross magnetic field configuration over distances of 1 AU. By placing a radio telescope well above the ionosphere it is possible to observe the radio emission down to frequencies that correspond to emission at distances of the order of 1 AU. The observations reported provide the first 'radio picture' over 1 AU of the spiral magnetic field configuration in interplanetary space.

Fainberg, J.; Evans, L. G.; Stone, R. G.

1972-01-01

178

Whistler Waves Associated with Weak Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

We analyze the properties of 98 weak interplanetary shocks measured by the dual STEREO spacecraft over approximately 3 years during the past solar minimum. We study the occurrence of whistler waves associated with these shocks, which on average are high beta shocks (0.2 < Beta < 10). We have compared the waves properties upstream and downstream of the shocks. In the upstream region the waves are mainly circularly polarized, and in most of the cases (approx. 75%) they propagate almost parallel to the ambient magnetic field (<30 deg.). In contrast, the propagation angle with respect to the shock normal varies in a broad range of values (20 deg. to 90 deg.), suggesting that they are not phase standing. We find that the whistler waves can extend up to 100,000 km in the upstream region but in most cases (88%) are contained in a distance within 30,000 km from the shock. This corresponds to a larger region with upstream whistlers associated with IP shocks than previously reported in the literature. The maximum amplitudes of the waves are observed next to the shock interface, and they decrease as the distance to the shock increases. In most cases the wave propagation direction becomes more aligned with the magnetic field as the distance to the shock increases. These two facts suggest that most of the waves in the upstream region are Landau damping as they move away from the shock. From the analysis we also conclude that it is likely that the generation mechanism of the upstream whistler waves is taking place at the shock interface. In the downstream region, the waves are irregularly polarized, and the fluctuations are very compressive; that is, the compressive component of the wave clearly dominates over the transverse one. The majority of waves in the downstream region (95%) propagate at oblique angles with respect to the ambient magnetic field (>60 deg.). The wave propagation with respect to the shock-normal direction has no preferred direction and varies similarly to the upstream case. It is possible that downstream fluctuations are generated by ion relaxation as suggested in previous hybrid simulation shocks.

Velez, J. C. Ramirez; Blanco-Cano, X.; Aguilar-Rodriguez, E.; Russell, C. T.; Kajdic, P.; Jian,, L. K.; Luhmann, J. G.

2012-01-01

179

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

Microsoft Academic Search

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

P. Wintoft; H. Lundstedt

1997-01-01

180

FAST TRACK COMMUNICATION: Kinematic magnetic dynamo in a random flow with strong average shear  

NASA Astrophysics Data System (ADS)

We analyze the kinematic dynamo in a conducting fluid where the stationary shear flow is accompanied by relatively weak random velocity fluctuations. The diffusionless and diffusion regimes are described. The growth rates of the magnetic field moments are related to the statistical characteristics of the flow describing the divergence of Lagrangian trajectories. A degree of anisotropy of the magnetic field is estimated. We demonstrate that Zeldovich's 'antidynamo theorem' is wrong.

Kogan, V. R.; Kolokolov, I. V.; Lebedev, V. V.

2010-05-01

181

Magnetic Resonance Colonography in the Detection of Colonic Neoplasm in High-Risk and Average-Risk Individuals  

Microsoft Academic Search

OBJECTIVES:Magnetic resonance colonography (MRC) is a new noninvasive diagnostic modality for colorectal cancer. However, the use of MRC in the detection of colorectal neoplasm in average-risk individuals remains unknown. This study determined the performance and the patient's preference of MRC in the detection of colorectal neoplasm.METHODS:Both high-risk (i.e., symptoms suggestive of colorectal neoplasm, positive fecal occult blood test, history of

Wai K. Leung; Wynnie W. M. Lam; Justin C. Y. Wu; Nina M. C. So; Sara S. L. Fung; Francis K. L. Chan; Deacons T. K. Yeung; Joseph J. Y. Sung

2004-01-01

182

The Solar and Interplanetary Causes of Geomagnetic Activity and Quiet  

NASA Technical Reports Server (NTRS)

This presentation will show that the three distinct phases of magnetic storms (initial, main, recovery) can each have considerably different characteristics during solar minimum and solar maximum. Illustrated will be the interplanetary causes of these differences; and, that a year during the descending phase of the solar cycle had significantly greater auroral activity than a year of solar maximum.

Gonzalez, W. D.; Tsurutani, B. T.; Tang, F.

1995-01-01

183

Large-amplitude Alfvén waves in the interplanetary medium, 2  

Microsoft Academic Search

An extensive study of the dynamic nonshock properties of the microscale fluctuations (scale lengths of 0.01 AU and less) in the interplanetary medium was made by using plasma and magnetic field data from Mariner 5 (Venus 1967). The observational results of the study-are: (1) Large- amplitude, nonsinusoidal Mfvn waves propagating outward from the sun with a broad wave- length range

J. W. Belcher; Leverett Davis

1971-01-01

184

Search Coil vs. Fluxgate Magnetometer Measurements at Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

We present magnetic field observations at interplanetary shocks comparing two different sample rates showing significantly different results. Fluxgate magnetometer measurements show relatively laminar supercritical shock transitions at roughly 11 samples/s. Search coil magnetometer measurements at 1875 samples/s, however, show large amplitude (dB/B as large as 2) fluctuations that are not resolved by the fluxgate magnetometer. We show that these fluctuations, identified as whistler mode waves, would produce a significant perturbation to the shock transition region changing the interpretation from laminar to turbulent. Thus, previous observations of supercritical interplanetary shocks classified as laminar may have been under sampled.

Wilson, L.B., III

2012-01-01

185

Interplanetary Shocks and "Suprathermal" Flare Particles  

NASA Technical Reports Server (NTRS)

We use ion-composition data from ACE/ULEIS, low energy electrons from ACE/EPAM, high energy protons from SoHO/ERNE, radio data from Wind/WAVES, and solar wind data from ACE/SWEPAM and ACE/MAG to investigate the solar and interplanetary circumstances near the times of passage of near-Earth shocks. We are particularly interested in claims that local acceleration by some interplanetary shocks produces Fe/O > 0.3 ('Fe-rich' shocks). The choice of the specific interval used to calculate the Fe/O ratio is extremely important because shock-accelerated particles can be masked by particles from flare events, related or unrelated to the shock, that have Fe/O > 0.3. We conclude that shock- accelerated populations have Fe/0<0.3. We illustrate 5 events which have been reported to be Fe-rich and for which Fe/O increases with energy in the 0.5-2 MeV/nuc range. We find that in each case there are direct flare particles included in the averaging time interval. We also demonstrate that the Fe/O ratio increases as a result of the averaging time interval being too large.

Cane, H. V.; Richardson, I. G.; vonRosenvinge, T. T.

2006-01-01

186

Fine-scale characteristics of interplanetary sector  

NASA Technical Reports Server (NTRS)

The structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions was studied. Such regions consist of intermediate (nonspiral) average field orientations in some cases, as well as a number of large angle directional discontinuities (DD's) on the fine scale (time scales 1 hour). Such DD's are found to be more similar to tangential than rotational discontinuities, to be oriented on average more nearly perpendicular than parallel to the ecliptic plane to be accompanied usually by a large dip ( 80%) in B and, with a most probable thickness of 3 x 10 to the 4th power km, significantly thicker previously studied. It is hypothesized that the observed structures represent multiple traversals of the global heliospheric current sheet due to local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05 - 0.1 AU superimposed on the large scale structure.

Behannon, K. W.; Neubauer, F. M.; Barnstoff, H.

1980-01-01

187

Stability of force-free Taylor states in a new version of magnetic flux-averaged magnetohydrodynamics  

SciTech Connect

It is observed that the recently developed magnetic flux-averaged magnetohydrodynamics (AMHD) [Phys. Plasmas {bold 1}, 2488 (1994)] is incompatible with Taylor{close_quote}s theorem, which states that the lowest-energy state of force-free equilibria based on the conservation of the helicity integral is absolutely stable for vanishingly small resistivity. By a modification of the Lagrangian from which AMHD is derived, a modified version of AMHD that is compatible with Taylor{close_quote}s theorem is obtained. It also provides an energy principle for examining the linear instability of resistive equilibria, which has a great advantage over resistive MHD. {copyright} {ital 1996 American Institute of Physics.}

Pfirsch, D. [Max-Planck-Insitut fur Plasmaphysik, EURATOM Association, D-8046, Garching (Germany)] [Max-Planck-Insitut fur Plasmaphysik, EURATOM Association, D-8046, Garching (Germany); Sudan, R.N. [Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States)] [Laboratory of Plasma Studies, Cornell University, Ithaca, New York 14853 (United States)

1996-01-01

188

Determination of the Average Aromatic Cluster Size of Fossil Fuels by Solid-State NMR at High Magnetic Field  

SciTech Connect

We show that the average aromatic cluster size in complex carbonaceous materials can be accurately determined using fast magic-angle spinning (MAS) NMR at a high magnetic field. To accurately quantify the nonprotonated aromatic carbon, we edited the 13C spectra using the recently reported MAS-synchronized spin–echo, which alleviated the problem of rotational recoupling of 1H-13C dipolar interactions associated with traditional dipolar dephasing experiments. The dependability of this approach was demonstrated on selected Argonne Premium coal standards, for which full sets of basic structural parameters were determined with high accuracy.

Mao, Kanmi [ExxonMobile Research and Engineering Co.; Kennedy, Gordon J. [ExxonMobile Research and Engineering Co.; Althaus, Stacey M. [Ames Laboratory; Pruski, Marek [Ames Laboratory

2013-01-07

189

STEREO Observations of Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

STEREO observations have been very valuable to study the characteristics of interplanetary (IP) shocks. These shocks can be driven in the heliosphere by fast interplanetary coronal mass ejections (CME) and by solar wind stream interaction (SI). In this work we will discuss the properties of IP shocks and the upstream and downstream regions associated to them. These regions are perturbed due to shock effects. Upstream from the shock a foreshock can develop and be permeated by suprathermal ions and electromagnetic waves. Downstream the plasma is heated and compressed. In this region the magnetic field is also very perturbed. Shocks play a very important role in particle acceleration. During the years 2007-2010 STEREO observed around 80 IP forward shocks driven by stream interactions, and 19 shocks driven by ICMEs. Most of the SI shocks were locally quasi-perpendicular (?Bn >45°) with only 20 quasi-parallel (?Bn < 45°) shocks. In all cases the Mach number was moderate with values 1.1< Mms < 3.8, and the plasma beta reached values up to 29. During the same years the shocks driven by ICMEs have Mach numbers 1.2-4, and plasma beta up to 15. Observations upstream from the shocks have revealed a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. In contrast to planetary bow shocks, most of the waves upstream of the quasi-parallel forward SI shocks observed to date by STEREO are mainly transverse and no steepening occurs. Another difference with Earth's bow shock is the fact that many locally quasi-perpendicular shocks can be accompanied by wave and ion foreshocks. This indicates that at an earlier time the geometry of the shock was quasi-parallel. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. Downstream fluctuations associated with quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr ?0.05 AU. This is smaller than foreshock extensions for ICME driven shocks (dr ? 0.1 AU). The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at ~1 AU and have been producing suprathermal particles for a shorter time. It is possible that stronger shocks driven by fast ICMEs are observed in the following months as the solar cycle of activity reaches maximum. Stronger IP shocks may be able to drive more complex foreshocks, where steepened waves such as shocklets may be present.

Blanco-Cano, X.

2013-05-01

190

Pollution potentials in interplanetary space  

NASA Astrophysics Data System (ADS)

Members of several Commissions in the Planetary Systems Division of the International Astronomical Union have become increasingly concerned at the harmful potentials of a number of proposed space missions, particularly those intending to utilise either nuclear or kinetic energy disruption of comets and small asteroids. This concern has led to the establishment of a Working Group on the Prevention of Pollution in Interplanetary Space, which involves six IAU Commissions. The aim of the Working Group is to identify sensitive issues in the interplanetary environment and draw attention to the harmful consequences of ignoring them, rather than adopting a legalistic regulatory approach.

Keay, C. S. L.

191

Interplanetary Propagation Behavior of the Fast Coronal Mass Ejection on 23 July 2012  

NASA Astrophysics Data System (ADS)

The fast coronal mass ejection (CME) from 23 July 2012 raised attention due to its extremely short transit time from Sun to 1 AU of less than 21 h. In-situ data from STEREO-A revealed the arrival of a fast forward shock with a speed of more than 2200 km s$^{-1}$ followed by a magnetic structure moving with almost 1900 km s$^{-1}$. We investigate the propagation behavior of the CME shock and magnetic structure with the aim to reproduce the short transit time and high impact speed as derived from in-situ data. We carefully measure the 3D kinematics of the CME using the graduated cylindrical shell model, and obtain a maximum speed of 2580$\\pm$280 km s$^{-1}$ for the CME shock and of 2270$\\pm$420 km s$^{-1}$ for its magnetic structure. Based on the 3D kinematics, the drag-based model (DBM) reproduces the observational data reasonably well. To successfully simulate the CME shock, we find that the ambient flow speed should be of average value close to the slow solar wind speed (450 km s$^{-1}$), and the initial shock speed at a distance of 30 $R_{\\odot}$ should not exceed $\\approx$2300 km s$^{-1}$, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely low aerodynamic drag force is exerted on the shock, smaller by one order of magnitude compared to the average. As a consequence, the CME hardly decelerates in interplanetary space and maintains its high initial speed. The low aerodynamic drag can only be reproduced when reducing the density of the ambient solar wind flow, in which the massive CME propagates, to $\\rho_{\\rm sw}$=1-2 cm$^{-3}$ at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space owing to a previous CME.

Temmer, M.; Nitta, N. V.

2015-01-01

192

Interplanetary Trajectories, Encke Method (ITEM)  

NASA Technical Reports Server (NTRS)

Modified program has been developed using improved variation of Encke method which avoids accumulation of round-off errors and avoids numerical ambiguities arising from near-circular orbits of low inclination. Variety of interplanetary trajectory problems can be computed with maximum accuracy and efficiency.

Whitlock, F. H.; Wolfe, H.; Lefton, L.; Levine, N.

1972-01-01

193

Interplanetary shock waves: Recent developments  

Microsoft Academic Search

Direct and indirect observations of interplanetary shock waves have been extended to the study of (i) the shock structure itself; (ii) the disturbed solar wind in its wake; (iii) additional discontinuities such as reverse shocks and pistons; and (iv) the shock's kinematic behavior. The last item — the trajectory — has benefited by the procedure (suggested by Pintér) of matching

Murray Dryer

1975-01-01

194

Interplanetary Field Enhancements: Observations from 0.3 AU to 1 AU  

E-print Network

. Interplanetary Field Enhancements are rare but very distinct increases in the magnetic field strength, reaching studied by Helios 1 and 2. The ponderomotive force exerted by the magnetic field strength decreases enhancement, solar wind disturbance. PACS: 96.50.Bh, 96.50.Dj INTRODUCTION The magnetic field is an agent

California at Berkeley, University of

195

MAGNETOHYDRODYNAMIC SIMULATIONS OF INTERPLANETARY CORONAL MASS EJECTIONS  

SciTech Connect

We describe a new MHD model for the propagation of interplanetary coronal mass ejections (ICMEs) in the solar wind. Accurately following the propagation of ICMEs is important for determining space weather conditions. Our model solves the MHD equations in spherical coordinates from a lower boundary above the critical point to Earth and beyond. On this spherical surface, we prescribe the magnetic field, velocity, density, and temperature calculated typically directly from a coronal MHD model as time-dependent boundary conditions. However, any model that can provide such quantities either in the inertial or rotating frame of the Sun is suitable. We present two validations of the technique employed in our new model and a more realistic simulation of the propagation of an ICME from the Sun to Earth.

Lionello, Roberto; Downs, Cooper; Linker, Jon A.; Török, Tibor; Riley, Pete; Miki?, Zoran, E-mail: lionel@predsci.com, E-mail: cdowns@predsci.com, E-mail: linker@predsci.com, E-mail: tibor@predsci.com, E-mail: pete@predsci.com, E-mail: mikic@predsci.com [Predictive Science, Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121-2910 (United States)

2013-11-01

196

Alfven waves in spiral interplanetary field  

NASA Technical Reports Server (NTRS)

A theoretical study is presented of the Alfven waves in the spiral interplanetary magnetic field. The Alfven waves under consideration are arbitrary, large amplitude, non-monochromatic, microscale waves of any polarization. They superpose on a mesoscale background flow of thermally anisotropic plasma. Using WKB approximation, an analytical solution for the amplitude vectors is obtained as a function of the background flow properties: density, velocity, Alfven speed, thermal anisotropy, and the spiral angel. The necessary condition for the validity of the WKB solution is discussed. The intensity of fluctuations is calculated as a function of heliocentric distance. Relative intensity of fluctuations as compared with the magnitude of the background field has its maximum in the region near l au. Thus outside of this region, the solar wind is less turbulent.

Whang, Y. C.

1973-01-01

197

THREE-DIMENSIONAL FEATURES OF THE OUTER HELIOSPHERE DUE TO COUPLING BETWEEN THE INTERSTELLAR AND INTERPLANETARY MAGNETIC FIELDS. III. THE EFFECTS OF SOLAR ROTATION AND ACTIVITY CYCLE  

SciTech Connect

We investigate the effects of the 11 year solar cycle and 25 day rotation period of the Sun on the interaction of the solar wind (SW) with the local interstellar medium (LISM). Our models take into account the partially ionized character of the LISM and include momentum and energy transfer between the ionized and neutral components. We assume that the interstellar magnetic field vector belongs to the hydrogen deflection plane as discovered in the SOHO SWAN experiment. This plane is inclined at an angle of about 60 deg. toward the ecliptic plane of the Sun, as suggested in recent publications relating the local interstellar cloud properties to the radio emission observed by Voyager 1. It is assumed that the latitudinal extent of the boundary between the slow and fast SW regions, as well as the angle between the Sun's rotation and magnetic-dipole axes, are periodic functions of time, while the polarity of the interstellar magnetic field changes sign every 11 years at the solar maximum. The global variation of the SW-LISM interaction pattern, the excursions of the termination shock and the heliopause, and parameter distributions in certain directions are investigated. The analysis of the behavior of the wavy heliospheric current sheet in the supersonic SW region shows the importance of neutral atoms on its dynamics.

Pogorelov, Nikolai V.; Borovikov, Sergey N.; Zank, Gary P. [Physics Department and Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, 320 Sparkman Dr., Huntsville, AL 35805 (United States); Ogino, Tatsuki [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601 (Japan)], E-mail: Nikolai.Pogorelov@uah.edu, E-mail: snb0003@uah.edu, E-mail: zank@cspar.uah.edu, E-mail: ogino@stelab.nagoya-u.ac.jp

2009-05-10

198

The emergence of different polarity photospheric flux as the cause of CMEs and interplanetary shocks  

NASA Technical Reports Server (NTRS)

Here we discuss the effect that the emergence of flux with a polarity opposed to that previously established in a certain photospheric region. can have on the magnetic structure of the solar atmosphere. We show that such a flux emergence may lead to the ejection of coronal material into the interplanetary medium (a CME) and also to a rapid change in the velocity of the solar wind from the region, which may eventually lead to the formation of an interplanetary shock.

Bravo, S.

1995-01-01

199

An Empirical Relationship Between Interplanetary Conditions and Dst  

Microsoft Academic Search

An algorithm is presented for predicting the ground-based Dst index solely from a knowledge of the velocity and density of the solar wind and the north-south solar magnetospheric component of the interplanetary magnetic field. The three key elements of this model are an adjustment for solar wind dynamic pressure, an injection rate linearly proportional to the dawn-to-dusk component of the

R. K. Burton; R. L. McPherron; C. T. Russell

1975-01-01

200

Helicity transport from solar convection zone to interplanetary space  

NASA Astrophysics Data System (ADS)

Magnetic helicity is a physical quantity that describes field topology. It is also a conserved quantity as Berger in 1984 demonstrated that the total magnetic helicity is still conserved in the corona even when there is a fast magnetic reconnection. It is generally believed that solar magnetic fields, together with their helicity, are created in the convection zone by various dynamo processes. These fields and helicity are transported into the corona through solar photosphere and finally released into the interplanetary space via various processes such as coronal mass ejections (CMEs) and solar winds. Here I will give a brief review on our recent works, first on helicity observations on the photosphere and how to understand these observations via dynamo models. Mostly, I will talk about what are the possible consequences of magnetic helicity accumulation in the corona, namely, the formation of magnetic flux ropes, CMEs taking place as an unavoidable product of coronal evolution, and flux emergences as a trigger of CMEs. Finally, I will address on in what a form magnetic field in the interplanetary space would accommodate a large amount of magnetic helicity that solar dynamo processes have been continuously producing.

Zhang, Mei

2013-07-01

201

Observations of the interplanetary plasma  

Microsoft Academic Search

Observations bearing on the nature and properties of the interplanetary plasma are reviewed, and consideration is given to possible fruitful directions for further work. The observations are classified according as they involve traditional (comet tail, optical, geomagnetic, cosmic ray), radio (solar noise, radar, radio-source scattering and scintillation, space-probe transmission) or direct (space-probe) measurements. A fairly complete set of references up

W. I. Axford

1968-01-01

202

Using Coordinated Observations in Polarised White Light and Faraday Rotation to Probe the Spatial Position and Magnetic Field of an Interplanetary Sheath  

E-print Network

Coronal mass ejections (CMEs) can be continuously tracked through a large portion of the inner heliosphere by direct imaging in visible and radio wavebands. White-light (WL) signatures of solar wind transients, such as CMEs, result from Thomson scattering of sunlight by free electrons, and therefore depend on both the viewing geometry and the electron density. The Faraday rotation (FR) of radio waves from extragalactic pulsars and quasars, which arises due to the presence of such solar wind features, depends on the line-of-sight magnetic field component $B_\\parallel$, and the electron density. To understand coordinated WL and FR observations of CMEs, we perform forward magnetohydrodynamic modelling of an Earth-directed shock and synthesise the signatures that would be remotely sensed at a number of widely distributed vantage points in the inner heliosphere. Removal of the background solar wind contribution reveals the shock-associated enhancements in WL and FR. While the efficiency of Thomson scattering depen...

Xiong, Ming; Feng, Xueshang; Owens, Mathew J; Harrison, Richard A; Davis, Chris J; Liu, Ying D

2013-01-01

203

USING COORDINATED OBSERVATIONS IN POLARIZED WHITE LIGHT AND FARADAY ROTATION TO PROBE THE SPATIAL POSITION AND MAGNETIC FIELD OF AN INTERPLANETARY SHEATH  

SciTech Connect

Coronal mass ejections (CMEs) can be continuously tracked through a large portion of the inner heliosphere by direct imaging in visible and radio wavebands. White light (WL) signatures of solar wind transients, such as CMEs, result from Thomson scattering of sunlight by free electrons and therefore depend on both viewing geometry and electron density. The Faraday rotation (FR) of radio waves from extragalactic pulsars and quasars, which arises due to the presence of such solar wind features, depends on the line-of-sight magnetic field component B{sub ?} and the electron density. To understand coordinated WL and FR observations of CMEs, we perform forward magnetohydrodynamic modeling of an Earth-directed shock and synthesize the signatures that would be remotely sensed at a number of widely distributed vantage points in the inner heliosphere. Removal of the background solar wind contribution reveals the shock-associated enhancements in WL and FR. While the efficiency of Thomson scattering depends on scattering angle, WL radiance I decreases with heliocentric distance r roughly according to the expression I?r {sup –3}. The sheath region downstream of the Earth-directed shock is well viewed from the L4 and L5 Lagrangian points, demonstrating the benefits of these points in terms of space weather forecasting. The spatial position of the main scattering site r{sub sheath} and the mass of plasma at that position M{sub sheath} can be inferred from the polarization of the shock-associated enhancement in WL radiance. From the FR measurements, the local B{sub ?sheath} at r{sub sheath} can then be estimated. Simultaneous observations in polarized WL and FR can not only be used to detect CMEs, but also to diagnose their plasma and magnetic field properties.

Xiong, Ming; Feng, Xueshang; Liu, Ying D. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing (China); Davies, Jackie A.; Harrison, Richard A. [Rutherford-Appleton Laboratory (RAL) Space, Harwell Oxford (United Kingdom); Owens, Mathew J.; Davis, Chris J., E-mail: mxiong@spacweather.ac.cn [Reading University, Reading (United Kingdom)

2013-11-01

204

A Floor in the Solar Wind Magnetic Field  

Microsoft Academic Search

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

L. Svalgaard; E. W. Cliver

2007-01-01

205

Atypical Particle Heating at a Supercritical Interplanetary Shock  

NASA Technical Reports Server (NTRS)

We present the first observations at an interplanetary shock of large amplitude (> 100 mV/m pk-pk) solitary waves and large amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

Wilson, Lynn B., III

2010-01-01

206

Propagation of Interplanetary Disturbances in the Outer Heliosphere  

NASA Technical Reports Server (NTRS)

Contents include the following: 1. We have developed a one-dimensional, spherically symmetric, multi-fluid MHD model that includes solar wind protons and electrons, pickup ions, and interstellar neutral hydrogen. This model advances the existing solar wind models for the outer heliosphere in two important ways: one is that it distinguishes solar wind protons from pickup ions, and the other is that it allows for energy transfer from pickup ions to the solar wind protons. Model results compare favorably with the Voyager 2 observations. 2. 2. Solar wind slowdown and interstellar neutral density. The solar wind in the outer heliosphere is fundamentally different from that in the inner heliosphere since the effects of interstellar neutrals become significant. 3. ICME propagation from the inner to outer heliosphere. Large coronal mass ejections (CMEs) have major effects on the structure of the solar wind and the heliosphere. The plasma and magnetic field can be compressed ahead of interplanetary CMEs. 4. During the current solar cycle (Cycle 23), several major CMEs associated with solar flares produced large transient shocks which were observed by widely-separated spacecraft such as Wind at Earth and Voyager 2 beyond 60 AU. Using data from these spacecraft, we use the multi-fluid model to investigate shock propagation and interaction in the heliosphere. Specifically, we studied the Bastille Day 2000, April 2001 and Halloween 2003 events. 5. Statistical properties of the solar wind in the outer heliosphere. In a collaboration with L.F. Burlaga of GSFC, it is shown that the basic statistical properties of the solar wind in the outer heliosphere can be well produced by our model. We studied the large-scale heliospheric magnetic field strength fluctuations as a function of distance from the Sun during the declining phase of a solar cycle, using our numerical model with observations made at 1 AU during 1995 as input. 6. Radial heliospheric magnetic field events. The heliospheric magnetic field (HMF) direction, on average, conforms well to the Parker spiral.

Wang, Chi

2005-01-01

207

Solar and interplanetary control of the location of the Venus bow shock  

NASA Technical Reports Server (NTRS)

The Venus bow shock location has been measured at nearly 2000 shock crossings, and its dependence on solar EUV, solar wind conditions, and the interplanetary magnetic field determined. The shock position at the terminator varies from about 2.14 Venus radii at solar minimum to 2.40 Venus radii at solar maximum. The location of the shock varies little with solar wind dynamic pressure but strongly with solar wind Mach number. The shock is farthest from Venus on the side of the planet in which newly created ions gyrate away from the ionosphere. When the interplanetary magnetic field is perpendicular to the flow, the cross section of the shock is quite elliptical. This effect appears to be due to the anisotropic propagation of the fast magnetosonic wave. When the interplanetary magnetic field is aligned with the flow, the bow shock cross section is circular and only weakly sensitive to changing EUV flux.

Russell, C. T.; Chou, E.; Luhmann, J. G.; Gazis, P.; Brace, L. H.; Hoegy, W. R.

1988-01-01

208

STEREO observations of waves near the ramp region of interplanetary shocks  

NASA Astrophysics Data System (ADS)

We present a study of wave modes observed at interplanetary shocks by the STEREO spacecraft. Electric field waveform captures from the STEREO Time Domain Sampler ('TDS') were examined throughout the shock with special emphasis on waves in the ramp region. Magnetic field data at 8 samples per second allowed ramp regions as short as 0.25 seconds to be identified. This study represents a major improvement in coverage of the ramp region compared to previous WIND studies and will lead to a better understanding of the microphysics in the ramp region. For example, STEREO sees many shocks where more than half of the ramp region is sampled by TDS captures through a combination of short duration ramps and multiple TDS captures in a single ramp. When STEREO's TDS captures occurred during the ramp an average of ~25% of the ramp duration was sampled. This increased coverage is a significant improvement over the average ~1% coverage seen by WIND TDS captures at interplanetary shocks in Wilson et al., 2007. Additionally, the longer TDS captures on STEREO (66 and 131 ms) compared to WIND (17 ms) had several advantages: observation of lower frequency waves, comparison of multiple ~20 ms wave packets within a single capture, and detection of lower amplitude waves (~5mV/m) that persist throughout some TDS captures and would have been hidden on WIND due to superimposed ~25 mV/m wave packets that last for over 20 ms. An automated program, to identify when one wave mode dominated the TDS capture, identified ion acoustic, Langmuir, and whistler waves in TDS captures in/near the ramp region. Dust captures and/or multiple wave modes prevented identifying a singular dominant wave mode in some TDS captures. Our results agree with Wilson et al., 2007 both in terms of ion acoustic wave amplitude (10s of mV/m) and in showing a dominance of ion acoustic waves in shock ramps. In addition, our study shows that when a dominant wave could be identified in TDS captures during the ramp, shocks with longer (shorter) duration ramps showed a slight dominance of whistler (ion acoustic) waves. Additionally, when only one TDS capture was taken in the ramp region and no other captures were taken near the shock there was a preference towards ion acoustic wave dominance in the TDS capture. The STEREO TDS captures in this study also found multiple distinct ion acoustic wave packets longer than the WIND TDS samples used in previous studies, which suggests ion acoustic waves could be an intermittent rather than a constant dissipation mechanism in interplanetary shocks.

Hupach, A. J.; Cattell, C. A.; Breneman, A. W.; Kersten, K.; Wilson, L. B.; Goetz, K.

2012-12-01

209

On the performance enhancement of adaptive signal averaging: A means for improving the sensitivity and rate of data acquisition in magnetic resonance and other analytical measurements  

NASA Astrophysics Data System (ADS)

A few years back, our lab developed a signal averaging technique that greatly reduces the number of scans required to achieve a comparable signal-to-noise ratio to that of conventional signal averaging for continuous wave magnetic resonance measurements. We utilize an adaptive filter in a signal averaging scheme without any prior knowledge of the signal under observation. We termed this technique adaptive signal averaging (ASA). The technique was successful in reducing the noise variance by a factor of at least 10 in a single trace and is shown to converge in time by the same factor. ASA can also be useful in many other applications where signal averaging is utilized, such as medical imaging, electrocardiography, or electroencephalography. The purpose of this paper is to describe the advancements made to the technique, present a derivation of its performance enhancement, and illustrate the power of the technique through a set of simulations.

Cochrane, C. J.

2012-10-01

210

CFDP for Interplanetary Overlay Network  

NASA Technical Reports Server (NTRS)

The CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol for Interplanetary Overlay Network (CFDP-ION) is an implementation of CFDP that uses IO' s DTN (delay tolerant networking) implementation as its UT (unit-data transfer) layer. Because the DTN protocols effect automatic, reliable transmission via multiple relays, CFDP-ION need only satisfy the requirements for Class 1 ("unacknowledged") CFDP. This keeps the implementation small, but without loss of capability. This innovation minimizes processing resources by using zero-copy objects for file data transmission. It runs without modification in VxWorks, Linux, Solaris, and OS/X. As such, this innovation can be used without modification in both flight and ground systems. Integration with DTN enables the CFDP implementation itself to be very simple; therefore, very small. Use of ION infrastructure minimizes consumption of storage and processing resources while maximizing safety.

Burleigh, Scott C.

2011-01-01

211

Ion bombardment of interplanetary dust  

NASA Technical Reports Server (NTRS)

It is thought that a fraction of the interplanetary dust particles (IDP's) collected in the stratosphere by high-flying aircraft represent materials ejected from comets. An investigation is conducted regarding the effects of ion bombardment on these particles, taking into account information on ion tracks and carbon in IDP's and laboratory data on charged particle bombardment of surfaces. It is found that the observational discovery of particle tracks in certain IDP's clearly indicates the exposure of these particles to approximately 10,000 years of 1-AU equivalent solar-particle fluences. If some erasure of the tracks occurs, which is likely when an IDP enters the upper atmosphere, then somewhat longer times are implied. The effects of the erosion and enhanced adhesion produced by ions are considered.

Johnson, R. E.; Lanzerotti, L. J.

1986-01-01

212

Unusual wave activity near interplanetary shocks  

SciTech Connect

It has been reported that quasiparallel (Q{sub parallel}) shocks are generally characterized by hours of upstream ion-acoustic-like wave activity and that quasiperpendicular (Q{sub perpendicular}) shocks show only minimal upstream wave activity. However, many exceptions to these trends have been observed by the ULYSSES Unified Radio and Plasma wave (URAP) Experiment near interplanetary shocks. These exceptions include: (1) Q{sub perpendicular} shocks with extended periods of high-frequency ion-acoustic-like wave activity in the upstream regions and (2) Q{sub parallel} shocks with minimal wave activity upstream. Moreover, the peak amplitudes of the upstream, transition and downstream ion-acoustic-like waves are not highly correlated with the angle between the magnetic field and the shock normal, {theta}{sub Bn}. These observations do not indicate any systematic difference in the ion-acoustic-like wave activity associated with Q{sub perpendicular} and Q{sub parallel} shocks. The implications of the present observations for the generally accepted scenarios of upstream wave and particle phenomena and the theories of the origin of diffuse ion distributions are discussed.

Thejappa, G.; MacDowall, R. J.; Stone, R. G. [Department of Astronomy, University of Maryland, College Park, Maryland 20742 (United States); Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

1996-07-20

213

Shielding Structures for Interplanetary Human Mission  

NASA Astrophysics Data System (ADS)

Since the end of Apollo missions, human spaceflight has been limited to the Low Earth Orbit (LEO), inside the protective magnetic field of the Earth, because astronauts are, to the largest degree, protected from the harsh radiation environment of the interplanetary space. However, this situation will change when space exploration missions beyond LEO will become the real challenge of the human exploration program. The feasibility of these missions in the solar system is thus strongly connected to the capability to mitigate the radiation-induced biological effects on the crew during the journey and the permanence on the intended planet surface. Inside the International Space Station (ISS), the volumes in which the crew spends most of the time, namely the crew quarters are the only parts that implement dedicated additional radiation shielding made of polyethylene tiles designed for mitigating SPE effects. Furthermore, specific radiation shielding materials are often added to the described configuration to shield crew quarters or the entire habitat example of these materials are polyethylene, liquid hydrogen, etc. but, increasing the size of the exploration vehicles to bring humans beyond LEO, and without the magnetosphere protection, such approach is unsustainable because the mass involved is a huge limiting factor with the actual launcher engine technology. Moreover, shielding against GCR with materials that have a low probability of nuclear interactions and in parallel a high ionizing energy loss is not always the best solution. In particular there is the risk to increase the LET of ions arriving at the spacecraft shell, increasing their Radio-Biological Effectiveness. Besides, the production of secondary nuclei by projectile and target fragmentation is an important issue when performing an engineering assessment of materials to be used for radiation shielding. The goal of this work is to analyze different shielding solutions to increase as much as possible the radiation shielding power of the interplanetary habitat structures, like the spacecraft shell, minimizing the amount of mass used. From the radiation protection point of view the spacecraft shell is an interesting spacecraft system because it surrounds almost homogeneously all the habitat and it is typically composed by the Micrometeorites and Debris Protection Systems (MDPS), the Multilayer Insulation (MLI) for thermal control purposes, and the primary structure that offers the pressure containment functionality. Nevertheless, the spacecraft internal outfitting is important to evaluate the different shielded areas in the habitat. Using Geant4 Monte Carlo simulations toolkit through GRAS (Geant4 Radiation Analysis for Space) tool, different spacecraft structures will be analyzed for their shielding behavior in terms of fluxes, dose reduction and radiation quality, and for their implementation in a real pressurized module. Effects on astronauts and electronic equipments will be also assessed with respect to the standard aluminum structures.

Tracino, Emanuele; Lobascio, Cesare

2012-07-01

214

Interplanetary medium data book, supplement 4, 1985-1988  

NASA Technical Reports Server (NTRS)

An extension is presented of the series of Interplanetary Medium Data Books and supplements which have been issued by the National Space Science Data Center since 1977. This volume contains solar wind magnetic field (IMF) and plasma data from the IMP 8 spacecraft for 1985 to 1988, and 1985 IMF data from the Czechoslovakian Soviet Prognoz 10 spacecraft. The normalization of the MIT plasma density and temperature, which has been discussed at length in previous volumes, is implemented as before, using the same normalization constants for 1985 to 1988 data as for the earlier data.

King, Joseph H.

1989-01-01

215

Operating CFDP in the Interplanetary Internet  

NASA Technical Reports Server (NTRS)

This paper examines the design elements of CCSDS File Delivery Protocol and Interplanetary Internet technologies that will simplify their integration and discusses the resulting new capabilities, such as efficient transmission of large files via multiple relay satellites operating in parallel.

Burleigh, S.

2002-01-01

216

A near-IR line of Mn I as a diagnostic tool of the average magnetic energy in the solar photosphere  

E-print Network

We report on spectropolarimetric observations of a near-IR line of Mn I located at 15262.702 A whose intensity and polarization profiles are very sensitive to the presence of hyperfine structure. A theoretical investigation of the magnetic sensitivity of this line to the magnetic field uncovers several interesting properties. The most important one is that the presence of strong Paschen-Back perturbations due to the hyperfine structure produces an intensity line profile whose shape changes according to the absolute value of the magnetic field strength. A line ratio technique is developed from the intrinsic variations of the line profile. This line ratio technique is applied to spectropolarimetric observations of the quiet solar photosphere in order to explore the probability distribution function of the magnetic field strength. Particular attention is given to the quietest area of the observed field of view, which was encircled by an enhanced network region. A detailed theoretical investigation shows that the inferred distribution yields information on the average magnetic field strength and the spatial scale at which the magnetic field is organized. A first estimation gives ~250 G for the mean field strength and a tentative value of ~0.45" for the spatial scale at which the observed magnetic field is horizontally organized.

A. Asensio Ramos; M. J. Martinez Gonzalez; A. Lopez Ariste; J. Trujillo Bueno; M. Collados

2006-12-14

217

Spectral analysis of magnetohydrodynamic fluctuations near interplanetary schocks  

NASA Technical Reports Server (NTRS)

Evidence for two types of relatively large amplitude MHD waves upstream and downstream of quasi-parallel forward and reverse interplanetary shocks is presented. The first mode is an Alfven wave with frequencies (in the spacecraft frame) in the range of 0.025 to 0.07 Hz. This is a left-hand polarized mode and propagates within a few degrees of the ambient magnetic field. The second is a fast MHD mode with frequencies in the range of 0.025 to 0.17 Hz, right-hand polarization and propagating along the magnetic field. These waves are detected principally in association with quasi-parallel shock. The Alfven waves are found to have plasma rest frame frequencies in the range of 1.1 to 6.3 mHz with wavelengths in the order of 4.8 x 10 to the 8th power to 2.7 x 10 to the 9th power cm. Similarly, the fast MHD modes have rest frame frequencies in the range 1.6 to 26 mHz with typical wavelengths about 2.19 x 10 to the 8th power cm. The magnetic field power spectrum in the vicinity of these interplanetary shocks is much steeper than f to the -s/3 at high frequencies. The observed spectra have a high frequency dependence of f to the -2/5 to f to the -4.

Vinas, A. F.; Goldstein, M. L.; Acuna, M. H.

1983-01-01

218

Interplanetary dust particles - Disintegration and orbital motion  

NASA Astrophysics Data System (ADS)

Abrupt or gradual disintegration of the interplanetary dust particle causes increase of its distance from the sun due to the solar radiation pressure. The problem of the orbital evolution of the interplanetary dust particles under such disintegration processes is discussed. The process of gradual disintegration due to the solar wind particles is calculated in detail. Obtained results represent corrections to the changes of orbital elements for the Poynting-Robertson effect and effect of the solar wind.

Klacka, J.

1993-01-01

219

On the high correlation between long-term averages of solar wind speed and geomagnetic activity  

NASA Technical Reports Server (NTRS)

Six-month and yearly averages of solar-wind speed from 1962 to 1975 are shown to be highly correlated with geomagnetic activity as measured by averages of the Ap index. On the same time scale the correlation between the southward component of the interplanetary magnetic field and geomagnetic activity is poor. Previous studies with hourly averages gave opposite results. The better correlation with the southward component on an hourly time scale is explained by its large variation compared with the relatively constant solar-wind speed. However, on a yearly time scale the magnitude of the variations in both parameters are about the same. This problem can be solved by invoking an energy transfer mechanism which is proportional to the first power of the southward component and a higher power of the solar-wind speed.

Crooker, N. U.; Feynman, J.; Gosling, J. T.

1977-01-01

220

Interplanetary coronal mass ejections in the near-Earth solar wind during 1996-2002  

Microsoft Academic Search

We summarize the occurrence of interplanetary coronal mass ejections (ICMEs) in the near-Earth solar wind during 1996-2002, corresponding to the increasing and maximum phases of solar cycle 23. In particular, we give a detailed list of such events. This list, based on in situ observations, is not confined to subsets of ICMEs, such as ``magnetic clouds'' or those preceded by

H. V. Cane; I. G. Richardson

2003-01-01

221

Ogo 5 Observations of Upstream Waves in the Interplanetary Medium: Discrete Wave Packets  

Microsoft Academic Search

One class of waves observed in the interplanetary medium within several earth radii of the earth's bow shock consists of discrete wave packets with amplitudes that are a significant fraction of the background magnetic field. In the spacecraft frame, these wave packets have periods of about 2.5 sec, grow rapidly in time and decay more slowly, and are left-handed with

C. T. Russell; D. D. Childers; P. J. Coleman

1971-01-01

222

The source of interplanetary dust  

NASA Astrophysics Data System (ADS)

Interplanetary dust particles can provide a wealth of information about the history and environment of the solar system. Unfortunately, it has not yet been clear whether their parent objects were primarily asteroidal or cometary. This situation seriously limits the applicability of the information gained form dust studies. I present here five experiments intended to reveal the source of interplanetary dust. First, I examine the IRAS asteroidal dust bands to find the fraction of the zodiacal dust contributed by single asteroid sources. The bands studied here contain approximately 1% of the zodiacal emission, insufficient to assign parent objects to most of the material. Gravitational focussing effects may boost the dust band contribution in terrestrial IDP collections to as high as 15%. The second and third experiments address micrometeoroid collisions, which appear to forbid delivery of particles larger than about 10-5 g from the asteroid belt to the Earth, in turn implying a cometary or near-Earth source for large dust motes. I test the assumed meteoroid of realistic porous materials. The result is that the previous collisional model is essentially correct. The verified break in the slope of the meteoroid mass distribution is consistent with collisional removal of greater than 10-5 g particles on a timescale similar to their Poynting-Robertson orbit decay lifetimes, if most originate in the asteroid belt. The fourth and fifth experiments turn to atmospheric entry heating effects as velocity diagnostic to separate fast cometary particles from slower asteroidal ones. I develop a new, physically realistic numerical simulation of particle entry. This model provides general results on particle origins, but is most useful when coupled with accurate measurements (based on the release of solar wind implant helium) of the peak entry temperatures of individual particles. It is found that most particles enter at low speeds. The few high-temperature particles imply a cometary fraction near 20%. Taking these results together, and considering previous work such as the meteoroid velocity distribution, I find an asteroid:comet dust ratio of approximately 4:1.

Love, Stanley Glen

1993-01-01

223

Radial speeds of an extreme Interplanetary Coronal Mass Ejection and its shock  

NASA Astrophysics Data System (ADS)

During the current solar cycle, our star has been less active when compared to the previous cycles. This is reflected in lower sunspot numbers but also in a lesser number of observed Coronal Mass Ejections (CME) and their interplanetary counterparts (ICME). However, lower solar activity does not necessarily mean less powerful events. Here we study propagation of an ICME that was detected by the STEREO A spacecraft on July 23, 2012. This was the most extreme event observed since the beginning of the space era. The magnetic field inside this ICME reached maximum value of 109 nT. The average ICME transit speed at 1 AU was 1910 kms-1, while its average speed on the way to 1 AU was 2125 kms-1. The ICME drove a fast-mode shock that preceded it. At the shock the plasma speed rose to 2250 kms-1. We study the propagation of the shock and of the ICME itself by using the radio data from the STEREO WAVES (S/WAVES) onboard of the STEREO A spacecraft. Since the shock emitted Type II radio emission, we are able to reconstruct its speed at various heliocentric distances. We also compare the measured velocities and arrival times of the shock and of the ejecta with predictions from numerical models.

Kajdic, Primoz; Gonzalez Esparza, Juan-Americo; Aguilar Rodriguez, Ernesto; Corona-Romero, Pedro

2014-05-01

224

Statistical comparison of interplanetary conditions causing intense geomagnetic storms (Dst ? -100 nT)  

NASA Astrophysics Data System (ADS)

It is well known that intense southward magnetic field and convection electric field (V × B) in the interplanetary medium are key parameters that control the magnitude of geomagnetic storms. By investigating the interplanetary conditions of 82 intense geomagnetic storms from 1998 to 2006, we have compared many different criteria of interplanetary conditions for the occurrence of the intense geomagnetic storms (Dst ? -100 nT). In order to examine if the magnetosphere always favors such interplanetary conditions for the occurrence of large geomagnetic storms, we applied these conditions to all the interplanetary data during the same period. For this study, we consider three types of interplanetary conditions as follows: Bz conditions, Ey conditions, and their combination. As a result, we present contingency tables between the number of events satisfying the condition and the number of observed geomagnetic storms. Then we obtain their statistical parameters for evaluation such as probability of detection yes, false alarm ratio, bias, and critical success index. From a comparison of these statistical parameters, we suggest that three conditions are promising candidates to trigger an intense storm: Bz ? -10 nT for >3 h, Ey ? 5 mV/m for >2 h, and Bz ? -15 nT or Ey ? 5 mV/m for >2 h. Also, we found that more than half of the “miss” events, when an intense storm occurs that was not expected, are associated with sheath field structures or corotating interacting regions. Our conditions can be used for not only the real-time forecast of geomagnetic storms but also the survey of interplanetary data to identify candidate events for producing intense geomagnetic storms.

Ji, Eun-Young; Moon, Y.-J.; Kim, K.-H.; Lee, D.-H.

2010-10-01

225

Interplanetary sources of space weather disturbances in 1997 to 2000  

NASA Astrophysics Data System (ADS)

Seventy-five disturbed intervals from 1997 through 2000 were analyzed and selected on the basis of space weather effect occurrences such as significant compression of the dayside magnetosphere, strong magnetic storms, ionospheric perturbations, relativistic electron enhancements, and increases in the rate of data failures and radiation doses on board the Mir station. Solar wind disturbances were considered as the main factor influencing the Earth's magnetosphere. We distinguished four geoeffective interplanetary (IP) phenomena: interplanetary coronal mass ejections (ICME), interplanetary forward shocks with compressed region (IS), fast solar wind streams from coronal holes (CH), and corotating interaction regions (CIR) between the CH and relatively slow ambient solar wind. Each selected interval was studied and classified under the IP phenomena that it was a direct consequence of. It was found that IP phenomena ``containing'' ISs, ICMEs, and CIRs were mostly responsible for geosynchronous magnetopause crossings, strong geomagnetic storms, and intensification of geomagnetically induced currents. The fast solar wind streams from coronal holes controlled mainly geosynchronous relativistic electron enhancements. The rate of data failures and variations of the radiation dose on board the Mir station were related to both IS-ICME and CIR-CH phenomena. Such a relationship was interpreted in terms of (1) decrease of cutoff threshold for solar energetic particles due to the magnetospheric compression and/or ring current intensification on the main phase of geomagnetic storms and (2) intensive relativistic electron precipitation from the outer radiation belt and its contribution to the radiation conditions at low altitudes during recovery phase of recurrent magnetic storms.

Dmitriev, A. V.; Crosby, N. B.; Chao, J.-K.

2005-03-01

226

New interplanetary proton fluence model  

NASA Technical Reports Server (NTRS)

A new predictive engineering model for the interplanetary fluence of protons with above 10 MeV and above 30 MeV is described. The data set used is a combination of observations made from the earth's surface and from above the atmosphere between 1956 and 1963 and observations made from spacecraft in the vicinity of earth between 1963 and 1985. The data cover a time period three times as long as the period used in earlier models. With the use of this data set the distinction between 'ordinary proton events' and 'anomalously large events' made in earlier work disappears. This permitted the use of statistical analysis methods developed for 'ordinary events' on the entire data set. The greater than 10 MeV fluences at 1 AU calculated with the new model are about twice those expected on the basis of models now in use. At energies above 30 MeV, the old and new models agree. In contrast to earlier models, the results do not depend critically on the fluence from any one event and are independent of sunspot number. Mission probability curves derived from the fluence distribution are presented.

Feynman, Joan; Armstrong, T. P.; Dao-Gibner, L.; Silverman, S.

1990-01-01

227

Quaternion Averaging  

NASA Technical Reports Server (NTRS)

Many applications require an algorithm that averages quaternions in an optimal manner. For example, when combining the quaternion outputs of multiple star trackers having this output capability, it is desirable to properly average the quaternions without recomputing the attitude from the the raw star tracker data. Other applications requiring some sort of optimal quaternion averaging include particle filtering and multiple-model adaptive estimation, where weighted quaternions are used to determine the quaternion estimate. For spacecraft attitude estimation applications, derives an optimal averaging scheme to compute the average of a set of weighted attitude matrices using the singular value decomposition method. Focusing on a 4-dimensional quaternion Gaussian distribution on the unit hypersphere, provides an approach to computing the average quaternion by minimizing a quaternion cost function that is equivalent to the attitude matrix cost function Motivated by and extending its results, this Note derives an algorithm that deterniines an optimal average quaternion from a set of scalar- or matrix-weighted quaternions. Rirthermore, a sufficient condition for the uniqueness of the average quaternion, and the equivalence of the mininiization problem, stated herein, to maximum likelihood estimation, are shown.

Markley, F. Landis; Cheng, Yang; Crassidis, John L.; Oshman, Yaakov

2007-01-01

228

A study of spacecraft charging due to exposure to interplanetary protons  

NASA Technical Reports Server (NTRS)

The interplanetary space environment is composed mostly of plasma from the solar wind and high energy protons from solar events such as coronal mass ejections. Satellites orbiting Earth are shielded to some degree from these events by the Earth's magnetic field but spacecraft traveling between planets are exposed to these solar protons directly. A major concern for spacecraft is internal electrostatic discharge (IESD), a form of spacecraft charging. The majority of research regarding IESD has been concerned with the electrons in the space environment around the Earth and at Jupiter; little research has been done on the charging of spacecraft in interplanetary space due to solar event protons. This paper reviews the work done so far on IESD due to protons and provides a possible example of an anomaly due to a proton induced discharge in interplanetary space on the Galileo spacecraft.

Green, Nelson W.; Frederickson, A. Robb

2005-01-01

229

Solar and Interplanetary Disturbances Causing Moderate Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

The effect of solar and interplanetary disturbances on geomagnetospheric conditions leading to one hundred twenty one moderate geomagnetic storms (MGSs) with planetary index, Ap ? 20 and horizontal component of earth's magnetic field, H ? 250? have been investigated using solar geophysical data (SGD), solar wind plasma (SWP) and interplanetary magnetic field (IMF) data during the period 1978-99. It is observed statistically that 64%, 36%, MGSs have occurred during maximum and minimum phase of solar cycle 21st and 22nd respectively. Further, it is observed that H?, X-ray solar flares and active prominences and disapp earing filaments (APDFs) have occurred within lower helio latitude region associated with larger number of MGSs. No significant correlation between the intensity of GMSs and importance of H?, X-ray solar flares have been observed. Maximum number of MGSs are associated with solar flares of lower importance of solar flare faint (SF). The lower importance in association with some specific characteristics i.e. location, region, duration of occurrence of event may also cause MGSs. The correlation coefficient between MGSs and sunspot numbers (SSNs) using Karl Pearson method, has been obtained 0.37 during 1978-99.

Pratap Yadav, Mahendra; Kumar, Santosh

2003-07-01

230

Interplanetary Shocks Lacking Type 2 Radio Bursts  

NASA Technical Reports Server (NTRS)

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (approximately 34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed approximately 535 km/s) and only approximately 40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km/s and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration approximately +6.8 m/s (exp 2)), while those associated with RL shocks were decelerating (average acceleration approximately 3.5 m/s (exp 2)). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant in the rise phase and decreases through the maximum and declining phases of solar cycle 23. About 18% of the IP shocks do not have discernible ejecta behind them. These shocks are due to CMEs moving at large angles from the Sun-Earth line and hence are not blast waves. The solar sources of the shock-driving CMEs follow the sunspot butterfly diagram, consistent with the higher-energy requirement for driving shocks.

Gopalswamy, N.; Xie, H.; Maekela, P.; Akiyama, S.; Yashiro, S.; Kaiser, M. L.; Howard, R. A.; Bougeret, J.-L.

2010-01-01

231

INTERPLANETARY SHOCKS LACKING TYPE II RADIO BURSTS  

SciTech Connect

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks ({approx}34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed {approx}535 km s{sup -1}) and only {approx}40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km s{sup -1} and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration {approx}+6.8 m s{sup -2}), while those associated with RL shocks were decelerating (average acceleration {approx}-3.5 m s{sup -2}). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant in the rise phase and decreases through the maximum and declining phases of solar cycle 23. About 18% of the IP shocks do not have discernible ejecta behind them. These shocks are due to CMEs moving at large angles from the Sun-Earth line and hence are not blast waves. The solar sources of the shock-driving CMEs follow the sunspot butterfly diagram, consistent with the higher-energy requirement for driving shocks.

Gopalswamy, N.; Kaiser, M. L. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Xie, H.; Maekelae, P.; Akiyama, S. [Catholic University of America, Washington, DC 20064 (United States); Yashiro, S. [Interferometrics, Herndon, VA 20170 (United States); Howard, R. A. [Naval Research Laboratory, Washington, DC 20375 (United States); Bougeret, J.-L., E-mail: nat.gopalswamy@nasa.go [Paris Observatory, Meudon (France)

2010-02-20

232

Effects of drift on the transport of cosmic rays. IV - Modulation by a wavy interplanetary current sheet  

Microsoft Academic Search

The effect of a wavy interplanetary current sheet on the solar modulation of galactic cosmic rays is studied. A simple model of the heliospheric magnetic field is employed in which there is an Archimedean spiral magnetic field directed in one direction above the current sheet and another direction below. The current sheet itself is taken to be the extension by

J. R. Jokipii; B. Thomas

1981-01-01

233

Average Speed  

NSDL National Science Digital Library

This lab is not an inquiry activity but will help students understand the meaning of average velocity. Students do not easily understand from a textbook that an object's velocity changes over a period of acceleration. They have difficulty understanding wh

Horton, Michael

2009-05-30

234

Interplanetary drivers of ionospheric prompt penetration electric fields  

NASA Astrophysics Data System (ADS)

In this paper we discussed the penetration effects of common interplanetary magnetic cloud (MC) structures like sheath region, both sheath and magnetic cloud boundary layer (MCBL), MC body, and shock-running into a preceding MC on the equatorial ionosphere during intense (SYM-H ?-100 nT) geomagnetic storms. Using solar wind data obtained from the ACE and WIND spacecraft, we have identified these four types of MC structures responsible for the electric field penetration events detected by Jicamarca incoherent scatter radar. After elimination of the propagation delay, the observations show that the equatorial electric field (EEF) was changed immediately following the arrival of solar wind disturbance. Moreover, the duration of EEF corresponded well with that of the corresponding MC structure interval. We suggest that identifying the solar wind structures associated with penetration electric field may shed light on the understanding of the penetration processes and further help exploring their effects on the ionospheric plasma.

Guo, Jianpeng; Feng, Xueshang; Zuo, Pingbing; Zhang, Jie; Wei, Yong; Zong, Qiugang

2011-01-01

235

International Launch Vehicle Selection for Interplanetary Travel  

NASA Technical Reports Server (NTRS)

In developing a mission strategy for interplanetary travel, the first step is to consider launch capabilities which provide the basis for fundamental parameters of the mission. This investigation focuses on the numerous launch vehicles of various characteristics available and in development internationally with respect to upmass, launch site, payload shroud size, fuel type, cost, and launch frequency. This presentation will describe launch vehicles available and in development worldwide, then carefully detail a selection process for choosing appropriate vehicles for interplanetary missions focusing on international collaboration, risk management, and minimization of cost. The vehicles that fit the established criteria will be discussed in detail with emphasis on the specifications and limitations related to interplanetary travel. The final menu of options will include recommendations for overall mission design and strategy.

Ferrone, Kristine; Nguyen, Lori T.

2010-01-01

236

Quiet time particle acceleration in interplanetary space  

E-print Network

We propose a model for the acceleration of charged particles in interplanetary space that appear during quiet time periods, that is, not associated with solar activity events like intense flares or coronal mass ejections. The interaction of charged particles with modeled turbulent electromagnetic fields, which mimic the fields observed in the interplanetary medium, is studied. The turbulence is modeled by means of a dynamical system,the Gledzer-Ohkitani-Yamada (GOY) shell model, which describes the gross features of the Navier-Stokes equations. The GOY model is used to build a 3-D velocity field, which in turn is used to numerically solve the ideal magneto-hydrodynamic (MHD) induction equation, while the electric field is calculated from the ideal Ohm's law. Particle acceleration in such an environment is investigated by test particle simulations, and the resulting energy distributions are discussed and compared to observations of suprathermal electrons and ions during quiet periods in interplanetary space.

F. Lepreti; H. Isliker; K. Petraki; L. Vlahos

2004-12-09

237

Interplanetary Space Weather and Its Planetary Connection  

NASA Astrophysics Data System (ADS)

Interplanetary travel is not just a science fiction scenario anymore, but a goal as realistic as when our ancestors started to cross the oceans. With curiosity driving humans to visit other planets in our solar system, the understanding of interplanetary space weather is a vital subject today, particularly because the physical conditions faced during a space vehicle's transit to its targeted solar system object are crucial to a mission's success and vital to the health and safety of spacecraft crew, especially when scheduling planned extravehicular activities.

Crosby, Norma; Bothmer, Volker; Facius, Rainer; Grießmeier, Jean-Mathias; Moussas, Xenophon; Panasyuk, Mikhail; Romanova, Natalia; Withers, Paul

2008-01-01

238

Cross-tail magnetic flux ropes as observed by the GEOTAIL spacecraft  

SciTech Connect

Ten transient magnetic structures in Earth`s magnetotail, as observed in GEOTAIL measurements, selected for early 1993 [at({minus}) X{sub GSM}=90-130 R{sub E}], are shown to have helical magnetic field configurations similar to those of interplanetary magnetic clouds at 1 AU but smaller in size by a factor of {approx} 700. Such structures are shown to be well approximated by a comprehensive magnetic force-free flux-rope model. For this limited set of 10 events the rope axes and the average diameter of these structures is {approx} 15 R{sub E}. 18 refs., 2 figs., 1 tab.

Leppintg, R.P.; Fairfield, D.H. [NASA/GSFC, Greenbelt, MD (United States)] [NASA/GSFC, Greenbelt, MD (United States); Jones, J. [Hughes STX Corporation, Greenbelt, MD (United States)] [and others] [Hughes STX Corporation, Greenbelt, MD (United States); and others

1995-05-15

239

Performance of interplanetary shock prediction models: STOA and ISPM  

Microsoft Academic Search

The shock time of arrival (STOA) model and the interplanetary shock propagation model (ISPM) give predictions of the time of arrival and strength of solar-initiated interplanetary shocks. This paper presents the first operational predictions made of interplanetary shocks that follow solar events. The time interval of this study was February 1997–March 1999 (the rise of Solar Cycle 23). The results

Z. Smith; M. Dryer; E. Ort; W. Murtagh

2000-01-01

240

Active shielding for long duration interplanetary manned missions  

NASA Astrophysics Data System (ADS)

The problem of protecting astronauts from the cosmic rays action in unavoidable and was therefore preliminary studied by many space agencies. In Europe, in the years 2002-2004, ESA supported two works on this thematic: a topical team in the frame of the ‘life and physical sciences' and a study, assigned by tender, of the ‘radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars'. In both studies it was concluded that, while the protection from solar cosmic rays can relay on the use of passive absorbers, for long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole duration of the mission. This requires the protection of a large habitat where they could live and work, and not a temporary small volume shelter, and the use of active shielding is therefore mandatory. The possibilities offered by using superconducting magnets were discussed, and the needed R&D recommended. The technical development occurred in the meantime and the evolution of the panorama of the possible interplanetary missions in the near future require to revise these pioneer studies and think of the problem at a scale allowing long human permanence in ‘deep' space, and not for a relatively small number of dedicated astronauts but also for citizens conducting there ‘normal' activities.

Spillantini, Piero

241

Interaction of an interplanetary shock with the heliospheric plasma sheet  

NASA Technical Reports Server (NTRS)

Interplanetary shocks often propagate along the heliospheric plasma sheet (HPS) where the interplanetary magnetic field (IMF) changes its polarity. This problem is investigated by the time-dependent 2.5-D MHD numerical model in the meridional plane. An example of computation is shown in the figure using density (log) contours and IMF vectors. Values of plasma parameters along the HPS fluctuate in time due to the Kelvin-Helmholtz instability. The HPS with its decreased intensity of the IMF as well as with its increased mass density causes a dimple in the shock structure (relatively weak for the forward shock, significant for the reverse shock, and very large for the contact discontinuity). Beyond the forward shock, the HPS is slightly compressed due to the post-shock increase of the azimuthal IMF component. Then follows expansion of the HPS surrounded by the highly-deformed contact discontinuity. A significant draping of IMF lines occurs around this structure that increases the meridional component of the IMF. This can cause a favorable condition for initiation of a geomagnetic storm.

Odstrcil, D.; Dryer, M.; Smith, Z.

1995-01-01

242

Interplanetary shocks preceded by solar filament eruptions  

NASA Technical Reports Server (NTRS)

The solar and interplanetary characteristics of six interplanetary shock and energetic particle events associated with the eruptions of solar filaments lying outside active regions are discussed. The events are characterized by the familiar double-ribbon H-alpha brightenings observed with large flares, but only very weak soft X-ray and microwave bursts. Both impulsive phases and metric type II bursts are absent in all six events. The energetic particles observed near the earth appear to be accelerated predominantly in the interplanetary shocks. The interplanetary shock speeds are lower and the longitudinal extents considerably less than those of flare-associated shocks. Three of the events were associated with unusual enhancements of singly-ionized helium in the solar wind following the shocks. These enhancements appear to be direct detections of the cool filament material expelled from the corona. It is suggested that these events are part of a spectrum of solar eruptive events which include both weaker events and the large flares. Despite their unimpressive and unreported solar signatures, the quiescent filament eruptions can result in substantial space and geophysical disturbances.

Cane, H. V.; Kahler, S. W.; Sheeley, N. R., Jr.

1986-01-01

243

Interplanetary monitoring platform engineering history and achievements  

NASA Technical Reports Server (NTRS)

In the fall of 1979, last of ten Interplanetary Monitoring Platform Satellite (IMP) missions ended a ten year series of flights dedicated to obtaining new knowledge of the radiation effects in outer space and of solar phenomena during a period of maximum solar flare activity. The technological achievements and scientific accomplishments from the IMP program are described.

Butler, P. M.

1980-01-01

244

INTERPLANETARY TYPE III RADIOBURSTS AND RELATIVISTIC ELECTRONS  

E-print Network

INTERPLANETARY TYPE III RADIOBURSTS AND RELATIVISTIC ELECTRONS S. HUCKE*, M.-B. KALLENRODE, and compared the antenna temperature TA of the 466 kHz type III bursts measured by the SBH instrument on ISEE 3 with the fluxes of ~ 0.5 MeV electrons measured by HELIOS. For 51 flare-associated kilometric type III bursts

Steinhoff, Heinz-Jürgen

245

Interplanetary shock waves generated by solar flares  

Microsoft Academic Search

Recent observational and theoretical studies of interplanetary shock waves associated with solar flares are reviewed. An attempt is made to outline the framework for the genesis, life and demise of these shocks. Thus, suggestions are made regarding their birth within the flare generation process, MHD wave propagation through the chromosphere and inner corona, and maturity to fully-developed coronal shock waves.

Murray Dryer

1974-01-01

246

Intensity of tropospheric circulation associated with solar magnetic sector boundary transits  

NASA Technical Reports Server (NTRS)

The fractional decrease in the vorticity area index associated with transits past the earth of interplanetary magnetic sector boundaries increase as the value of vorticity used to compute the index increases. This suggests that after the boundary transit there is an approximately uniform reduction in all the values of vorticity that are not less than 0.00020/sec. In low altitudes and large absolute vorticities not less than 0.00020/sec the average change in the vorticity area index approaches 50%.

Wilcox, J. M.; Scherrer, P. H.; Svalgaard, L.

1979-01-01

247

Relationship between the growth of the ring current and the interplanetary quantity. [solar wind energy-magnetospheric coupling parameter correlation with substorm AE index  

NASA Technical Reports Server (NTRS)

Akasofu (1979) has reported that the interplanetary parameter epsilon correlates reasonably well with the magnetospheric substorm index AE; in the first approximation, epsilon represents the solar wind coupled to the magnetosphere. The correlation between the interplanetary parameter, the auroral electrojet index and the ring current index is examined for three magnetic storms. It is shown that when the interplanetary parameter exceeds the amount that can be dissipated by the ionosphere in terms of the Joule heat production, the excess energy is absorbed by the ring current belt, producing an abnormal growth of the ring current index.

Akasofu, S.-I.

1979-01-01

248

Planetary and Interplanetary Environmental Models for Radiation Analysis  

NASA Technical Reports Server (NTRS)

The essence of environmental modeling is presented as suited for radiation analysis purposes. The variables of fundamental importance for radiation environmental assessment are discussed. The characterization is performed by dividing modeling into three areas, namely the interplanetary medium, the circumplanetary environment, and the planetary or satellite surface. In the first area, the galactic cosmic rays (GCR) and their modulation by the heliospheric magnetic field as well as and solar particle events (SPE) are considered, in the second area the magnetospheres are taken into account, and in the third area the effect of the planetary environment is also considered. Planetary surfaces and atmospheres are modeled based on results from the most recent targeted spacecraft. The results are coupled with suited visualization techniques and radiation transport models in support of trade studies of health risks for future exploration missions.

DeAngelis, G.; Cucinotta, F. A.

2005-01-01

249

Interplanetary fast shock diagnosis with the radio receiver on Ulysses  

NASA Technical Reports Server (NTRS)

The radio receiver on Ulysses records the quasi-thermal noise which allows a determination of the density and temperature of the cold (core) electrons of the solar wind. Seven interplanetary fast forward or reverse shocks are identified from the density and temperature profiles, together with the magnetic field profile from the Magnetometer experiment. Upstream of the three strongest shocks, bursts of nonthermal waves are observed at the electron plasma frequency f(peu). The more perpendicular the shock, the longer the time interval during which these upstream bursts are observed. For one of the strongest shocks we also observe two kinds of upstream electromagnetic radiation: radiation at 2 f(peu), and radiation at the downstream electron plasma frequency, which propagates into the less dense upstream regions.

Hoang, S.; Pantellini, F.; Harvey, C. C.; Lacombe, C.; Mangeney, A.; Meuer-Vernet, N.; Perche, C.; Steinberg, J.-L.; Lengyel-Frey, D.; Macdowall, R. J.

1992-01-01

250

An electrodynamic model of electric currents and magnetic fields in the dayside ionosphere of Venus  

NASA Technical Reports Server (NTRS)

The electric current configuration induced in the ionosphere of Venus by the interaction of the solar wind has been calculated in previous papers (Cloutier and Daniell, 1973; Daniell and Cloutier, 1977; Cloutier and Daniell, 1979) for average steady-state solar wind conditions and interplanetary magnetic field. This model is generalized to include the effects of (1) plasma depletion and magnetic field enhancement near the ionopause, (2) velocity-shear-induced MHD instabilities of the Kelvin-Helmholtz type within the ionosphere, and (3) variations in solar wind parameters and interplanetary magnetic field. It is shown that the magnetic field configuration resulting from the model varies in response to changes in solar wind and interplanetary field conditions, and that these variations produce magnetic field profiles in excellent agreement with those seen by the Pioneer-Venus Orbiter. The formation of flux-ropes by the Kelving-Helmholtz instability is shown to be a natural consequence of the model, with the spatial distribution and size of the flux-ropes determined by the magnetic Reynolds number.

Cloutier, P. A.; Tascione, T. F.; Danieli, R. E., Jr.

1981-01-01

251

Coronal Mass Ejections Near the Sun and in the Interplanetary Medium  

NASA Technical Reports Server (NTRS)

Coronal mass ejections (CMEs) are the most energetic phenomenon in the heliosphere. During solar eruptions, the released energy flows out from the Sun in the form of magnetized plasma and electromagnetic radiation. The electromagnetic radiation suddenly increases the ionization content of the ionosphere, thus impacting communication and navigation systems. The plasma clouds can drive shocks that accelerate charged particles to very high energies in the interplanetary space, which pose radiation hazard to astronauts and space systems. The plasma clouds also arrive at Earth in about two days and impact Earth's magnetosphere, producing geomagnetic storms. The magnetic storms result in a number of effects including induced currents that can disrupt power grids, railroads, and underground pipelines. This lecture presents an overview of the origin, propagation, and geospace consequences of CMEs and their interplanetary counterparts.

Gopalswamy, Nat

2012-01-01

252

Plasma wave phenomena observed at interplanetary shocks by the Ulysses URAP experiment  

NASA Technical Reports Server (NTRS)

Results of a study of 24 interplanetary shocks observed by the Unified Radio and Plasma Wave Experiment (URAP) on the Ulysses spacecraft are presented. These shocks, observed between approximately 1 and 4 AU, display a variety of wave phenomena similar to those detected in earlier studies of shocks near 1 AU. The correspondence of the observed low frequency magnetic and electric field waves with the parallel index of refraction for whistler waves was investigated. Observed B/E ratios are found to be typically about a factor of 0.7 times the computed index of refraction, supporting the whistler interpretation of these waves, but also implying a prevalent electrostatic wave component which may be due to whistlers propagating at an angle to the interplanetary magnetic field. A statistical correlation of the amplitudes of the various types of waves with shock and solar wind properties is presented.

Lengyel-Frey, D.; Macdowall, R. J.; Stone, R. G.; Hoang, S.; Pantellini, F.; Canu, P.; Cornilleau-Wehrlin, N.; Balogh, A.; Forsyth, R.

1992-01-01

253

An analytic solar magnetic field model  

Microsoft Academic Search

We describe a simple analytic model for the magnetic field in the solar corona and interplanetary space which is appropriate to solar minimum conditions. The model combines an azimuthal current sheet in the equatorial plane with an axisymmetric multipole field representing the internal magnetic field of the Sun. The radial component of the field filling interplanetary space is approximately monopolar

M. Banaszkiewicz; W. I. Axford; J. F. McKenzie

1998-01-01

254

Interplanetary-magnetospheric relationships: Data for Bartels rotation N. 1825 to 1974  

NASA Astrophysics Data System (ADS)

The 27-day average values for the isotropic nucleonic intensity (mean cosmic-ray energy = 15 GeV) and Ap index are reported for the period December 10, 1966 to January 10, 1978, to study medium term variations during one solar activity cycle. Fifteen parameters involved in the interplanetary - magnetospheric relationships were selected so as to present them on hourly basis in a series of data plots. Potential applications of these physical quantities are discussed.

Parisi, M.; Pase, S.; Storini, M.; Buccellato, R.; Felici, A.

1988-06-01

255

Microbeam analysis of four chondritic interplanetary dust particles for major elements, carbon and oxygen  

NASA Technical Reports Server (NTRS)

Chemical compositions determined using electron excited X-rays are reported for four interplanetary dust particles collected in the stratosphere. These analyses include measurements of carbon and oxygen abundances which are important elements in these primitive materials. Spot analyses show very heterogeneous compositions on a micrometer scale although average composition approaches that of C1 carbonaceous chondrites. While the spot analyses show intermediate compositions between cometary dust and carbonaceous chondrites, the heterogeneity more closely resembles that of comet Halley dust particles.

Blanford, G. E.; Thomas, K. L.; Mckay, D. S.

1988-01-01

256

Coupled hydromagnetic wave excitation and ion acceleration at interplanetary traveling shocks and Earth's bow shock revisited  

NASA Astrophysics Data System (ADS)

A revised version of the self-consistent theory of ion diffusive shock acceleration and the associated generation of hydromagnetic waves is presented. The theory generalizes and corrects the theory of Lee [1982, 1983]. Lee assumed a linear dependence of the anisotropic part of the ion distribution function on the cosine of the ion pitch angle. Here the wave growth or damping rate is again calculated using linear theory, but a more general ion anisotropy is calculated using the pitch angle diffusion equation. The wave intensity satisfies a wave kinetic equation, and the ion omnidirectional distribution function satisfies the energetic particle transport equation. These coupled equations are solved numerically and compared with an analytical approximation similar to that derived by Lee. The analytical approximation provides an accurate representation of both the proton distribution and the wave intensity. A comparison is made between the predicted wave magnetic power spectral density adjacent to the shock as a function of frequency and the wave spectrum measured by ISEE 3 at the November 11-12, 1978, interplanetary traveling shock. There is excellent agreement between the predicted and measured power spectral density in the frequency range of 0.03-0.3 Hz. A comparison is also made between the predicted total wave energy density and that observed upstream of Earth's bow shock by the AMPTE/IRM satellite for a statistical survey of ~400 near-to-nose events from late 1984 and 1985. This comparison revises the result presented by Trattner et al. [1994]. The correlation between the observed wave power and that predicted, based on the observed energetic proton energy density, is very good with a correlation coefficient of 0.92. However, the average observed wave magnetic energy density is ~63% of that predicted, suggesting possible wave dissipation which is not included in the theory.

Gordon, B. E.; Lee, M. A.; Möbius, E.; Trattner, K. J.

257

Bi-directional streaming of halo electrons in interplanetary plasma clouds observed between 0.3 and 1 AU  

NASA Technical Reports Server (NTRS)

The solar wind data obtained from the two Helios solar probes in the years 1974 to 1986 were systematically searched for the occurrence of bi-directional electron events. Most often these events are found in conjunction with shock associated magnetic clouds. The implications of these observations for the topology of interplanetary plasma clouds are discussed.

Ivory, K.; Schwenn, R.

1995-01-01

258

A New Look at Jupiter: Results at the Now Frontier. [Pioneer 10, interplanetary space, and Jupiter atmosphere  

NASA Technical Reports Server (NTRS)

Pioneer 10's encounter with Jupiter is discussed along with the interplanetary space beyond the orbit of Mars. Other topics discussed include the size of Jupiter, the Galilean satellites, the magnetic field of Jupiter, radiation belts, Jupiter's weather and interior, and future exploration possibilities. Educational projects are also included.

1975-01-01

259

Dusty Plasma Effects in the Interplanetary Medium?  

NASA Astrophysics Data System (ADS)

Cosmic dust particles exist in a variety of compositions and sizes in the interplanetary medium. There is little direct information on the composition, but those interplanetary dust particles that are collected in the upper Earth’s atmosphere and can be studied in the laboratory typically have an irregular, sometimes porous structure on scales <100 nm. They contain magnesium-rich silicates and silicon carbide, iron-nickel and iron-sulfur compounds, calcium- and aluminum oxides, and chemical compounds that contain a large mass fraction of carbon (e.g. carbonaceous species). A fraction of the dust originates from comets, but because of their bulk material temperature of about 280 K near 1 AU, most icy compounds have disappeared. The dust particles are embedded in the solar wind, a hot plasma with at 1 AU kinetic temperatures around 100 000 K and flow direction nearly radial outward from the Sun at supersonic bulk velocities around 400 km/s. Since the dust particles carry an electric surface charge they are subject to electromagnetic forces and the nanodust particles are efficiently accelerated to velocities of order of solar wind speed. The acceleration of the nanodust is similar, but not identical to the formation of pick-up ions. The S/WAVES radio wave instrument on STEREO measured a flux of nanodust at 1 AU [1]. The nanodust probably forms in the region inward of 1 AU and is accelerated by the solar wind as discussed. We also discuss the different paths of dust - plasma interactions in the interplanetary medium and their observations with space experiments. Comparing these interactions we show that the interplanetary medium near 1 AU can in many cases be described as “dust in plasma" rather than "dusty plasma”. [1] S. Belheouane, N. Meyer-Vernet, K. Issautier, G. Le Chat, A. Zaslavsky, Y. Zouganelis, I. Mann, A. Czechowski: Dynamics of nanoparticles detected at 1 AU by S/WAVES onboard STEREO spacecraft, in this session.

Mann, Ingrid; Issautier, Karine; Meyer-Vernet, Nicole; Le Chat, Gaétan; Czechowski, Andrzej; Zaslavsky, Arnaud; Zouganelis, Yannis; Belheouane, Soraya

260

Diffusive Acceleration of Ions at Interplanetary Shocks  

E-print Network

Heliospheric shocks are excellent systems for testing theories of particle acceleration in their environs. These generally fall into two classes: (1) interplanetary shocks that are linear in their ion acceleration characteristics, with the non-thermal ions serving as test particles, and (2) non-linear systems such as the Earth's bow shock and the solar wind termination shock, where the accelerated ions strongly influence the magnetohydrodynamic structure of the shock. This paper explores the modelling of diffusive acceleration at a particular interplanetary shock, with an emphasis on explaining in situ measurements of ion distribution functions. The observational data for this event was acquired on day 292 of 1991 by the Ulysses mission. The modeling is performed using a well-known kinetic Monte Carlo simulation, which has yielded good agreement with observations at several heliospheric shocks, as have other theoretical techniques, namely hybrid plasma simulations, and numerical solution of the diffusion-convection equation. In this theory/data comparison, it is demonstrated that diffusive acceleration theory can, to first order, successfully account for both the proton distribution data near the shock, and the observation of energetic protons farther upstream of this interplanetary shock than lower energy pick-up protons, using a single turbulence parameter. The principal conclusion is that diffusive acceleration of inflowing upstream ions can model this pick-up ion-rich event without the invoking any seed pre-acceleration mechanism, though this investigation does not rule out the action of such pre-acceleration.

Matthew G. Baring; Errol J. Summerlin

2005-06-08

261

A statistical survey of 5-MeV proton events at transient interplanetary shocks  

NASA Astrophysics Data System (ADS)

Between 1974 and 1985 the two Helios spacecraft observed 351 transient interplanetary shocks. For 5-MeV protons the particle events associated with these shocks can be divided into three groups: (1) events without intensity increase above quiet time or increased background (47%), (2) solar and interplanetary particle (SIP) events consisting of particles accelerated on or close to the Sun (solar or near-Sun component) as well as at the interplanetary shock (24%), and (3) pure interplanetary particle (PIP) events (29%) which consist of particles accelerated at the shock in interplanetary space but do not show evidence for significant or even excess particle acceleration on the Sun. This classification shows that (1) only about half of the shocks accelerate MeV protons in interplanetary space and (2) MeV protons accelerated on the Sun are neither a necessary nor a sufficient condition for the acceleration of MeV protons in interplanetary space. Shock parameters such as speed or shock strength alone do not give an indication for the class of the associated particle event, because in the parameter range which covers most of the shocks, all three classes are distributed rather evenly. However, the shocks strongest in these parameters tend to accelerate particles. The intensity at the time of shock-passage, which can be used as a crude measure for the local acceleration efficiency, is correlated with the local shock speed and the magnetic compression. The correlation coefficients are small but statistically significant, indicating that (1) the correlations are real and (2) the intensity is influenced by additional parameters, which are not necessarily shock inherent. As an example I will show that the local acceleration at the shock decreases roughly symmetrically with increasing distance from the nose of the shock with a median e-folding angle of 10°. Occasionally, larger e-folding angles are observed close to the nose of the shock. The question of how the shock accelerates protons in the MeV range could not be answered here, but I will suggest future studies that could shed a new light on this problem.

Kallenrode, May-Britt

1996-11-01

262

Effect of Interplanetary Shocks on AL and Dst Indices  

NASA Astrophysics Data System (ADS)

Analytic solar wind signals are constructed using data from the ACE satellite for the 3-6 October 2000 and 15-24 April 2002 geomagnetic storm events, which included interplanetary shocks and magnetic clouds. The WINDMI model is used to analyze the relative importance of the magnetic and pressure pulse structures in the solar wind on the AL and Dst geomagnetic indices. WINDMI is a well documented eight dimensional physics model of the solar wind driven magnetosphere-ionosphere system. The role of the shocks is shown by using analytic signals in which the shock feature in the density, solar wind velocity, and magnetic field magnitude are tested individually. WINDMI results from the analytic inputs show that the shock events strongly impacted the AL index values but only produced small changes in the Dst. In particular the first large -AL > 1300 nT spike during the October 2000 storm was triggered by the shock front (compression ratio: 2.3, shock speed: 530 km/s), and particularly by the jump in B\\perp from 7 nT to 16 nT. The three AL peaks during the April 2002 storm are associated with three shock events. The second shock on 19 April at 0801 UT which produced an -AL peaks of -1824 nT and -1851 nT is most effective of the three shocks. The work is supported by NSF-ATM grant 0539099.

Horton, W.; Mays, L.; Spencer, E.; Kozyra, J.; Huang, C.

2006-12-01

263

Solar rotating magnetic dipole?. [around axis perpendicular to rotation axis of the sun  

NASA Technical Reports Server (NTRS)

A magnetic dipole rotating around an axis perpendicular to the rotation axis of the sun can account for the characteristics of the surface large-scale solar magnetic fields through the solar cycle. The polarity patterns of the interplanetary magnetic field, predictable from this model, agree with the observed interplanetary magnetic sector structure.

Antonucci, E.

1974-01-01

264

Dual spacecraft observations of energetic particles in the vicinity of the magnetopause, bow shock, and the interplanetary medium  

NASA Technical Reports Server (NTRS)

Particle data obtained during a few orbits when the ISEE 1 and 2 spacecraft were on the front side of the magnetosphere are presented. Observations near the magnetopause and the bow-shock regions based on 32-sec averaged particle data are summarized. A more detailed picture of the particle features near these boundaries is given on the basis of 0.25-sec averages. Observations of low-energy particles in the upstream interplanetary medium are also examined.

Parks, G. K.; Gurgiolo, C.; Lin, C. S.; Anderson, K. A.; Lin, R. P.; Martel, F.; Reme, H.

1978-01-01

265

Laboratory simulation of interplanetary ultraviolet radiation (broad spectrum) and its effects on Deinococcus radiodurans  

NASA Astrophysics Data System (ADS)

The radiation-resistant bacterium Deinococcus radiodurans was exposed to a simulated interplanetary UV radiation at the Brazilian Synchrotron Light Laboratory (LNLS). Bacterial samples were irradiated on different substrates to investigate the influence of surface relief on cell survival. The effects of cell multi-layers were also investigated. The ratio of viable microorganisms remained virtually the same (average 2%) for integrated doses from 1.2 to 12 kJ m -2, corresponding to 16 h of irradiation at most. The asymptotic profiles of the curves, clearly connected to a shielding effect provided by multi-layering cells on a cavitary substrate (carbon tape), means that the inactivation rate may not change significantly along extended periods of exposure to radiation. Such high survival rates reinforce the possibility of an interplanetary transfer of viable microbes.

Paulino-Lima, Ivan Gláucio; Pilling, Sérgio; Janot-Pacheco, Eduardo; de Brito, Arnaldo Naves; Barbosa, João Alexandre Ribeiro Gonçalves; Leitão, Alvaro Costa; Lage, Claudia de Alencar Santos

2010-08-01

266

Bimodal abundances in the energetic particles of solar and interplanetary origin  

NASA Technical Reports Server (NTRS)

This letter reports the first results from an examination of the daily-averaged abundances of the elements from H through Fe as well as electrons and isotopes of He in energetic particles observed in interplanetary space by the ISEE 3 spacecraft over an 8.5 yr period. The abundances of heavy elements such as Fe/O show, for the first time, clear evidence of the presence of two distinct populations of particles. Earlier observations could be interpreted as extreme variations within a single population. The population with enhanced Fe/O shows correlated enhancements in He-3/He-4, p/e, and He/H. This population is consistent with material that has been processed to high temperatures in the impulsively heated regions of solar flares. The second population, with more normal abundances, is probably accelerated from ambient material by coronal and interplanetary shocks.

Reames, Donald V.

1988-01-01

267

Emission of whistler-mode waves and diffusion of electrons around interplanetary shocks  

SciTech Connect

We present a study of whistler-mode wave generation and wave particle interaction in the vicinity of interplanetary shocks in the ecliptic plane, as observed by the Ulysses spacecraft. Generally the whistler-mode waves (measured in the frequency range 0.22-448 Hz) are observed downstream of the shocks where they persist for some hours. From the electron distribution functions (EDF) in the energy range 1.6 to 862 eV, we compute the temperature anisotropy and the wave growth rate of the electromagnetic electron cyclotron instability for the case of parallel propagation of the waves with respect to the interplanetary magnetic field (IMF) B. In general, in agreement with the wave measurements, the instability grows only downstream of the shock fronts. Following the wave activity, velocity space diffusion of the electrons results in a marginally stable state with sporadic fluctuations.

Pierre, F.; Solomon, J.; Cornilleau-Wehrlin, N.; Canu, P.; Scime, E. E.; Phillips, J. L.; Balogh, A.; Forsyth, R. J. [IAS/CNRS/Univ. Paris 11, Orsay (France); CETP/CNRS, Velizy (France); CETP/CNRS, Velizy (France); Physics Dpt., West Virginia University, Morgantown, West Virginia (United States); Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Imperial College of Science and Technology, London (United Kingdom)

1996-07-20

268

Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock  

NASA Technical Reports Server (NTRS)

We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.

2010-01-01

269

Observations of quiet-time interplanetary electron enhancements of Jovian origin  

NASA Technical Reports Server (NTRS)

Electron data from Explorer 47 show a number of quiet-time enhancements in the intensity of interplanetary electrons over the energy range 0.22-2.5 MeV, lasting from 3 to 20 days both in the interplanetary medium and inside the magnetotail. The observed enhancements differ from those associated with solar electron events or magnetospheric bursts in their energy-time profiles and energy spectra, and in the presence of possible intensity fluctuations suggesting a periodicity. The energy spectra are not unlike those obtained in the vicinity of Jupiter by Pioneer 10. These observations, together with the fact that enhancements occurred during times when the earth could be magnetically connected to the magnetosphere of Jupiter, lead to the suggestion that the observed electrons may be of Jovian origin.

Krimigis, S. M.; Sarris, E. T.; Armstrong, T. P.

1975-01-01

270

Measurements of line-averaged electron density of pulsed plasmas using a He-Ne laser interferometer in a magnetized coaxial plasma gun device  

NASA Astrophysics Data System (ADS)

In next step of fusion devices such as ITER, lifetime of plasma-facing materials (PFMs) is strongly affected by transient heat and particle loads during type I edge localized modes (ELMs) and disruption. To clarify damage characteristics of the PFMs, transient heat and particle loads have been simulated by using a plasma gun device. We have performed simulation experiments by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The line-averaged electron density measured by a He-Ne interferometer is 2x10^21 m-3 in a drift tube. The plasma velocity measured by a time of flight technique and ion Doppler spectrometer was 70 km/s, corresponding to the ion energy of 100 eV for helium. Thus, the ion flux density is 1.4x10^26 m-2s-1. On the other hand, the MCPG is connected to a target chamber for material irradiation experiments. It is important to measure plasma parameters in front of target materials in the target chamber. In particular, a vapor cloud layer in front of the target material produced by the pulsed plasma irradiation has to be characterized in order to understand surface damage of PFMs under ELM-like plasma bombardment. In the conference, preliminary results of application of the He-Ne laser interferometer for the above experiment will be shown.

Iwamoto, D.; Sakuma, I.; Kitagawa, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2012-10-01

271

Propagation of solar flare-associated interplanetary shock waves in the heliospheric meridional plane  

NASA Technical Reports Server (NTRS)

An analysis is conducted for 149 flare-associated shock wave events based on interplanetary scintillation observational data. All of the flare-associated shock waves tend to propagate toward the low latitude region near the solar equator for flares that are located in both the solar Northern and Southern Hemispheres. Also, the fastest propagation directions tend toward the heliospheric current sheet near 1 AU. This tendency is caused by the dynamic action of near-sun magnetic forces on the ejected coronal plasma that traverses the helmet-like magnetic topologies near the sun outward to the classical topology that is essentially parallel to the heliospheric current sheet.

Wei, Fengsi; Dryer, Murray

1991-01-01

272

Nonthermal Radiation Processes in Interplanetary Plasmas  

NASA Astrophysics Data System (ADS)

RESUMEN. En la interacci6n de haces de electrones energeticos con plasmas interplanetarios, se excitan ondas intensas de Langmuir debido a inestabilidad del haz de plasma. Las ondas Langmuir a su vez interaccio nan con fluctuaciones de densidad de baja frecuencia para producir radiaciones. Si la longitud de las ondas de Langmujr exceden las condicio nes del umbral, se puede efectuar la conversi5n de modo no lineal a on- das electromagneticas a traves de inestabilidades parametricas. As se puede excitar en un plasma inestabilidades parametricas electromagneticas impulsadas por ondas intensas de Langmuir: (1) inestabilidades de decaimiento/fusi5n electromagnetica impulsadas por una bomba de Lang- muir que viaja; (2) inestabilidades dobles electromagneticas de decai- miento/fusi5n impulsadas por dos bombas de Langrnuir directamente opues- tas; y (3) inestabilidades de dos corrientes oscilatorias electromagne- ticas impulsadas por dos bombas de Langmuir de corrientes contrarias. Se concluye que las inestabilidades parametricas electromagneticas in- ducidas por las ondas de Langmuir son las fuentes posibles de radiacio- nes no termicas en plasmas interplanetarios. ABSTRACT: Nonthermal radio emissions near the local electron plasma frequency have been detected in various regions of interplanetary plasmas: solar wind, upstream of planetary bow shock, and heliopause. Energetic electron beams accelerated by solar flares, planetary bow shocks, and the terminal shock of heliosphere provide the energy source for these radio emissions. Thus, it is expected that similar nonthermal radiation processes may be responsible for the generation of these radio emissions. As energetic electron beams interact with interplanetary plasmas, intense Langmuir waves are excited due to a beam-plasma instability. The Langmuir waves then interact with low-frequency density fluctuations to produce radiations near the local electron plasma frequency. If Langmuir waves are of sufficiently large amplitude to exceed the thresfiold conditions, nonlinear mode conversion electromagnetic waves can be effected through parametric instabilities. A number of electromagnetic parametric instabilities driven by intense Langmuir waves can be excited in a plasma: (1) electromagnetic decay/fusion instabilities driven by a traveling Langmuir pump; (2) double electromagnetic decay/fusion instabilities driven by two oppositely directed Langmuir pumps; and (3) electromagnetic oscillating two-stream instabilities driven by two counterstreaming Langmuir pumps. It is concluded that the electromagnetic parametric instabilities induced by Langmuir waves are likely sources of nonthermal radiations in interplanetary plasmas. Keq ( : INTERPLANETARY MEDIUM - PLASMAS

Chian, A. C. L.

1990-11-01

273

Discovery of nuclear tracks in interplanetary dust  

NASA Technical Reports Server (NTRS)

Nuclear tracks have been identified in interplanetary dust particles (IDP's) collected from the stratosphere. The presence of tracks unambiguously confirms the extraterrestrial nature of IDP's, and the high track densities (10 to the 10th to 10 to the 11th per square centimeter) suggest an exposure age of approximately 10,000 years within the inner solar system. Tracks also provide an upper temperature limit for the heating of IDP's during atmospheric entry, thereby making it possible to distinguish between pristine and thermally modified micrometeorites.

Bradley, J. P.; Brownlee, D. E.; Fraundorf, P.

1984-01-01

274

Interplanetary exploration-A challenge for photovoltaics  

NASA Technical Reports Server (NTRS)

Future U.S. interplanetary missions will be less complex and costly than past missions such as Voyager and the soon to be launched, Galileo. This is required to achieve a balanced exploration program that can be sustained within the context of a limited budget. Radioisotope thermoelectric generators (RTGs) have served as the power source for missions beyond the orbit of Mars. It is indicated that the cost to the user of these power sources will significantly increase. Solar arrays can provide a low cost alternative for a number of missions. Potential missions are identified along with concerns for implementation, and some array configurations under present investigation are reviewed.

Stella, P. M.

1985-01-01

275

ACE Observations of Energetic Particles Associated with Transient Interplanetary Shocks  

E-print Network

ACE Observations of Energetic Particles Associated with Transient Interplanetary Shocks D. Lario a survey of the effects of interplanetary shocks on energetic >47 keV ions and >38 keV electrons as observed by the field (MAG), plasma (SWEPAM) and energetic particle (EPAM) experiments on the ACE

Sanahuja, Blai

276

Delay-tolerant networking: an approach to interplanetary Internet  

Microsoft Academic Search

Increasingly, network applications must communicate with counterparts across disparate networking environments characterized by significantly different sets of physical and operational constraints; wide variations in transmission latency are particularly troublesome. The proposed Interplanetary Internet, which must encompass both terrestrial and interplanetary links, is an extreme case. An architecture based on a \\

S. Burleigh; A. Hooke; L. Torgerson; K. Fall; V. Cerf; B. Durst; K. Scott; H. Weiss

2003-01-01

277

Modeling Interplanetary Logistics: A Mathematical Model for Mission Planning  

E-print Network

The President has tasked NASA with the development of a sustainable space transportation system that will enable to develop a sustainable space transportation architecture it is critical that interplanetary supply chainModeling Interplanetary Logistics: A Mathematical Model for Mission Planning Christine Taylor, Miao

de Weck, Olivier L.

278

The Interplanetary Overlay Networking Protocol Accelerator  

NASA Technical Reports Server (NTRS)

A document describes the Interplanetary Overlay Networking Protocol Accelerator (IONAC) an electronic apparatus, now under development, for relaying data at high rates in spacecraft and interplanetary radio-communication systems utilizing a delay-tolerant networking protocol. The protocol includes provisions for transmission and reception of data in bundles (essentially, messages), transfer of custody of a bundle to a recipient relay station at each step of a relay, and return receipts. Because of limitations on energy resources available for such relays, data rates attainable in a conventional software implementation of the protocol are lower than those needed, at any given reasonable energy-consumption rate. Therefore, a main goal in developing the IONAC is to reduce the energy consumption by an order of magnitude and the data-throughput capability by two orders of magnitude. The IONAC prototype is a field-programmable gate array that serves as a reconfigurable hybrid (hardware/ firmware) system for implementation of the protocol. The prototype can decode 108,000 bundles per second and encode 100,000 bundles per second. It includes a bundle-cache static randomaccess memory that enables maintenance of a throughput of 2.7Gb/s, and an Ethernet convergence layer that supports a duplex throughput of 1Gb/s.

Pang, Jackson; Torgerson, Jordan L.; Clare, Loren P.

2008-01-01

279

Solar Protons above 500 MeV in the Sun's Atmosphere and in Interplanetary Space  

NASA Astrophysics Data System (ADS)

At least two distinct acceleration mechanisms produce energetic particles at or near the Sun: (1) acceleration at coronal sites of magnetic reconnection, generally associated with flares and (2) acceleration at shocks driven by fast coronal mass ejections (CMEs). Both mechanisms can accelerate protons to well beyond 500 MeV. Moreover, when a very large solar energetic particle (SEP) event is observed in interplanetary space, both a large flare and the launch of a fast CME are observed nearly simultaneously (unless the flare occurs behind a limb). Numerous studies have tried to sort out how these two phenomena contribute to the energetic particle population. To date, there is no consensus on this issue, particularly at the highest energies, where the release of particles from the neighborhood of the Sun generally persists for only a short period of time. Although the maximum of Cycle 24 has been notably deficient in producing high-energy SEPs, new instrumentation has provided powerful new insights into these questions. Fermi provides routine measurements of solar gamma-rays above 100 MeV, from which the number of >500 MeV protons interacting in the solar-atmosphere can be deduced, separately in the impulsive phase of the flare (lasting minutes and coincident with hard x-ray emission) and in the frequently observed extended phase (which can persist for many hours and whose origin is under debate). Simultaneously, other satellites and ground-based neutron monitors provide measurements of these high-energy protons in interplanetary space, the modeling of which is greatly strengthened by the STEREO's observations of the large-scale heliospheric distribution of SEPs. We report results for seven events in which the time-integrated number of >500 MeV protons at the Sun and in interplanetary space have been independently extracted. We find that >500 MeV protons in the impulsive phase of the flare typically constitute a percent or less of the protons in IP space, without any clear correlation to the number of >500 MeV protons in interplanetary space. By contrast, the number of >500 MeV protons in the extended phase of the flare is typically ~5-10% of the number in interplanetary space and is well correlated with it. These results suggest that (1) the impulsive phase of the flare does not make a significant contribution to the interplanetary population at these very high energies and (2) the extended-phase gamma-ray emissions are likely due to shock-accelerated protons precipitating down onto the solar atmosphere.

Tylka, Allan J.; Share, Gerald H.; Dietrich, William F.; Murphy, Ronald J.; Keong Ng, Chee; Shea, Margaret A.; Smart, Don F.

2014-05-01

280

LDEF (Prelaunch), AO201 : Interplanetary Dust Experiment, Tray B12  

NASA Technical Reports Server (NTRS)

LDEF (Prelaunch), AO201 : Interplanetary Dust Experiment, Tray B12 The prelaunch photograph shows the six (6) inch deep Interplanetary Dust Experiment (IDE) master control tray. The tray has three (3) mounting/cover plates elevated on fiberglass stand-offs to provide clearance and protection for hardware and electronics located underneath. The stand-offs also raise the plates to a level that minimizes shading of detectors by the tray sidewalls. The mounting plate located at the left hand end of the tray is populated with eighty (80) metaloxide-silicon (MOS) capacitor-type impact sensors and one (1) solar sensor that is located approximately in the center of the mounting plate. The IDE sensors are two (2) inch diameter MOS capacitor structures approximately 250 um thick. The detectors are formed by growing either 0.4um or 1.0um thick silicon oxide, SiO2, layer on the 250um thick, B-doped polished silicon wafer. The top metal contact, the visible surface, was formed by vapor deposition of 1000A of aluminum on the SiO2 surface. Aluminum was also vapor deposited on the backside to form the contact with the silicon substrate. Gold wires are bonded to the front and back aluminum layers for use in connecting the detectors to the circuits. The complete wafers, IDE detectors, are mounted on chromic anodized aluminum frames by bonding the detector backside to the aluminum frame with a space qualified RTV silicon adhesive, de-volatized RTV-511. The difference in colors of the detectors is caused by reflections in the metallized surfaces. A reflection of one of the technicians is visible in the three (3) rows of detector on the left hand side of the mounting plate. The solar sensor, located at the mounting plate center, consist of four (4) silicon solar cells connected in series and associated circuity bonded to an aluminum baseplate. The solar sensor registered each orbital sunrise independant of LDEF orientation at the time of sunrise. When IDE solar sensor data from the six (6) orthogonal faces of the LDEF was correlated, the Interplanetary Dust Experiment clock could be precisely calibrated. The center 1/3rd tray cover is a chromic anodized aluminum plate that protects the IDE data conditioning and control electronics mounted underneath. The cover plate also serves as a mounting platform for ten (10) individual specimen holders provided by one of the IDE investigators.The material specimen, consisting of germanium, sapphire and zinc sulfide of different sizes, shapes and colors, are bonded to the specimen holders with an RTV adhesive. The specimen holders are attached to the cover plate with stainless steel non-magnetic fasteners. The 1/3rd tray cover plate in the right hand end of the experiment tray is an aluminum plate painted white with Chemglaze II A-276 paint and used as a thermal cover for the Experiment Power and Data System (EPDS). The EPDS is a system provided by the LDEF Project Office that processes and stores, on magnetic tape, the orbital experiment and housekeeping data from six (6) experiment locations on the LDEF.

1984-01-01

281

Jovian modulation of interplanetary electrons as observed with Voyagers 1 and 2  

NASA Technical Reports Server (NTRS)

The release of magnetospheric electrons from Jupiter into interplanetary space is modulated by the Jovian rotation period. The Voyager 1 and 2 observations showed that the modulation period agrees on the average with the synodic period of Jupiter (9h 55m 33.12s), but over intervals of weeks it can differ from the synodic period by several minutes. The lack of exact synchronization is attributed to changes of the plasma population in the Jovian magnetosphere. The Jovian modulation appears to be a persistent feature of the interaction between the solar wind and the magnetosphere and the disappearance of the modulation away from Jupiter is attributed to interplanetary propagation conditions. This leads to the following limits on the diffuse coefficient for interplanetary electrons: kappa perpendicular is or = 8 x 10 to the 19th power sq cm/s and kappa parallel is or = 10 to the 21st power sq cm/s. Modulation was still detectable at 3.8 A.U. behind Jupiter in the far magnetotail. This requires a mean free path in the tail 0.75 A.U. and good field connection along the tail to Jupiter.

Schardt, A. W.; Mcdonald, F. B.; Trainor, J. H.

1982-01-01

282

The interplanetary electric field, cleft currents and plasma convection in the polar caps  

NASA Technical Reports Server (NTRS)

The relationship between the pattern of plasma convection in the polar cleft and the dynamics of the interplanetary electric field (IEF) is examined theoretically. It is shown that owing to the geometrical properties of the magnetosphere, the East-West component of the IEF will drive field-aligned currents which connect to the ionosphere at points lying on either side of noon, while currents associated with the North-South component of the IEF will connect the two polar caps as sheet currents, also centered at 12 MLT. In order to describe the consequences of the Interplanetary Magnetic Field (IMF) effects upon high-latitude electric fields and convection patterns, a series of numerical simulations was carried out. The simulations were based on a solution to the steady-state equation of current continuity in a height-integrated ionospheric current. The simulations demonstrate that a simple hydrodynamical model can account for the narrow 'throats' of strong dayside antisunward convection observed during periods of southward interplanetary IMF drift, as well as the sunward convection observed during periods of strongly northward IMF drift.

Banks, P. M.; Clauer, C. R.; Araki, T.; St. Maurice, J. P.; Foster, J. C.

1984-01-01

283

PROPAGATION AND EVOLUTION OF THE JUNE 1st 2008 CME IN THE INTERPLANETARY MEDIUM  

NASA Astrophysics Data System (ADS)

In this work we present a study of the coronal mass ejection (CME) of June 1st of 2008 in the interplanetary medium. This event has been extensively studied by others because of its favorable geometry and the possible consequences of its peculiar initiation for space weather forecasting. We show an analysis of the evolution of the CME in the interplanetary medium in order to shed some light on the propagation mechanism of the ICME. We have determined the typical shock associated characteristics of the ICME in order to understand the propagation properties. Using two different non force-free models of the magnetic cloud allows us to incorporate expansion of the cloud. We use in-situ measurements from STEREO B/IMPACT to characterize the ICME. In addition, we use images from STEREO A/SECCHI-HI to analyze the propagation and visual evolution of the associated flux rope in the interplanetary medium. We compare and contrast these observations with the results of the analytical models.

Nieves-Chinchilla, T.; Lamb, D. A.; Davila, J. M.; Vinas, A. F.; Moestl, C.; Hidalgo, M. A.; Farrugia, C. J.; Malandraki, O.; Dresing, N.; Gómez-Herrero, R.

2009-12-01

284

Superposed epoch analyses of HILDCAAs and their interplanetary drivers: Solar cycle and seasonal dependences  

NASA Astrophysics Data System (ADS)

We study the solar cycle and seasonal dependences of high-intensity, long-duration, continuous AE activity (HILDCAA) events and associated solar wind/interplanetary external drivers for ~ 3 1/2 solar cycle period, from 1975 to 2011. 99 HILDCAAs which had simultaneous solar wind/interplanetary data are considered in the present analyses. The peak occurrence frequency of HILDCAAs was found to be in the descending phase of the solar cycle. These events had the strongest time-integrated AE intensities and were coincident with peak occurrences of high-speed solar wind streams. The event initiations were statistically coincident with high-to-slow speed stream interactions, compressions in the solar wind plasma and interplanetary magnetic field (IMF). The latter were corotating interaction regions (CIRs). The signatures of related CIRs were most prominent for the events occurring during the descending and solar minimum phases of the solar cycles. For these events, the solar wind speed increased by ~41% and ~57% across the CIRs, respectively. There was weak or no stream-stream interaction or CIR structure during the ascending and solar maximum phases. HILDCAAs occurring during spring and fall seasons were found to occur preferentially in negative and positive IMF sector regions (toward and away from the Sun), respectively.

Hajra, Rajkumar; Echer, Ezequiel; Tsurutani, Bruce T.; Gonzalez, Walter D.

2014-12-01

285

On the Effect of the Interplanetary Medium on Nanodust Observations by the Solar Terrestrial Relations Observatory  

E-print Network

New measurements using radio and plasma-wave instruments in interplanetary space have shown that nanometer-scale dust, or nanodust, is a significant contributor to the total mass in interplanetary space. Better measurements of nanodust will allow us to determine where it comes from and the extent to which it interacts with the solar wind. When one of these nanodust grains impacts a spacecraft, it creates an expanding plasma cloud, which perturbs the photoelectron currents. This leads to a voltage pulse between the spacecraft body and the antenna. Nanodust has a high charge/mass ratio, and therefore can be accelerated by the interplanetary magnetic field to speeds up to the speed of the solar wind: significantly faster than the Keplerian orbital speeds of heavier dust. The amplitude of the signal induced by a dust grain grows much more strongly with speed than with mass of the dust particle. As a result, nanodust can produce a strong signal, despite their low mass. The WAVES instruments on the twin Solar TErre...

Chat, G Le; Zaslavsky, A; Pantellini, F; Meyer-Vernet, N; Belheouane, S; Maksimovic, M

2015-01-01

286

Optical Studies of Zero-Field Magnetization of CdMnTe Quantum Dots: Influence of Average Size and Composition of Quantum Dots  

E-print Network

We show that through the resonant optical excitation of spin-polarized excitons into CdMnTe magnetic quantum dots, we can induce a macroscopic magnetization of the Mn impurities. We observe very broad (4 meV linewidth) emission lines of single dots, which are consistent with the formation of strongly confined exciton magnetic polarons. Therefore we attribute the optically induced magnetization of the magnetic dots results to the formation of spin-polarized exciton magnetic polarons. We find that the photo-induced magnetization of magnetic polarons is weaker for larger dots which emit at lower energies within the QD distribution. We also show that the photo-induced magnetization is stronger for quantum dots with lower Mn concentration, which we ascribe to weaker Mn-Mn interaction between the nearest neighbors within the dots. Due to particular stability of the exciton magnetic polarons in QDs, where the localization of the electrons and holes is comparable to the magnetic exchange interaction, this optically induced spin alignment persists to temperatures as high as 160 K.

T. Gurung; S. Mackowski; H. E. Jackson; L. M. Smith; W. Heiss; J. Kossut; G. Karczewski

2004-08-30

287

Interplanetary meteoroid debris in LDEF metal craters  

NASA Technical Reports Server (NTRS)

The extraterrestrial meteoroid residue found lining craters in the Long Duration Exposure Facility (LDEF) aluminum and gold targets is highly variable in both quantity and type. In typical craters only a minor amount of residue is found and for these craters it is evident that most of the impacting projectile was ejected during crater formation. Less than 10 percent of the craters greater than 100 microns contain abundant residue consistent with survival of a major fraction of the projectile. In these cases the residue can be seen optically as a dark liner and it can easily be analyzed by SEM-EDX techniques. Because they are rare, the craters with abundant residue must be a biased sampling of the meteoroids reaching the earth. Factors that favor residue retention are low impact velocity and material properties such as high melting point. In general, the SEM-EDX observations of crater residues are consistent with the properties of chondritic meteorites and interplanetary dust particles collected in the stratosphere. Except for impacts by particles dominated by single minerals such as FeS and olivine, most of the residue compositions are in broad agreement with the major element compositions of chondrites. In most cases the residue is a thin liner on the crater floor and these craters are difficult to quantitatively analyze by EDX techniques because the electron beam excites both residue and underlying metal substrate. In favorable cases, the liner is thick and composed of vesicular glass with imbedded FeNi, sulfide and silicate grains. In the best cases of meteoroid preservation, the crater is lined with large numbers of unmelted mineral grains. The projectiles fragmented into micron sized pieces but the fragments survived without melting. In one case, the grains contain linear defects that appear to be solar flare tracks. Solar flare tracks are common properties of small interplanetary particles and their preservation during impact implies that the fragments were not heated above 600 C. We are investigating the meteoroid fragments in LDEF metal craters to determine the properties of interplanetary dust and to determine if there are meteoroid types that are overlooked or otherwise undetected in cosmic dust collections obtained from the stratosphere and polar ice.

Brownlee, D. E.; Horz, F.; Bradley, J.

1992-01-01

288

What Controls the Classification of Interplanetary Mass Ejections  

NASA Astrophysics Data System (ADS)

In this paper we address a question what controls the classification of interplanetary mass ejections (ICMEs): magnetic cloud (MC) or ejecta (EJ). Using 186 shock-associated ICMEs from 1997 to 2006, we have examined three possible causes : (1) magnetic complexity with a proxy of sunspot number, (2) CME direction as a proxy of cone angle (the angle between the CME cone axis and the plane of sky), and (3) ICME-ICME interaction with a proxy of the number of halo CMEs. First, the fraction of MC is poorly anti-correlated (R=-0.36) with annual sunspot number. Second, the distribution of CME cone angle for 38 EJs is not much different from that for 16 MCs. Third, the annual fraction of magnetic cloud is well anti-correlated (R=-0.78) with the annual number of halo CMEs. To demonstrate such a relationship, we consider all halo CMEs during the same period and statistically searched the candidate of interacting ICMEs according to temporal and spatial closeness. As a result, we find that the annual fraction of interacting ICME candidates is well correlated (R=0.87) with the annual number of the halo CMEs as well as anti-correlated (R=-0.85) with the annual fraction of MCs. The contingency table between ICME-ICME interaction and MC occurrence also shows a good statistical result: Hit (110), False Alarm (53), Prediction of detection 'yes' (0.88), and Critical Success Index (0.62). Our results imply that the interaction of ICMEs is mainly responsible for their classification.

Moon, Yong-Jae; Gopalswamy, N.; Kim, R.; Xie, H.; Yashiro, S.

2011-05-01

289

Oxygen production for interplanetary return missions  

NASA Technical Reports Server (NTRS)

Interplanetary missions with extraterrestrial returns are limited by large propulsion mass requirements. The injected mass landed on an extraterrestrial body can be reduced substantially by utilizing indigenous materials for the production of propellant on the extraterrestrial body. Analyses reported show that for Mars return missions, in situ production of oxygen during the wait between landing and the next low-energy return opportunity reduces the Earth-launch mass requirements to the allowable limit for direct entry and direct return missions. A small chemical processor using radioisotope thermal energy can extract oxygen several times its own mass from carbon dioxide, during the several-hundred-days wait on Mars. The fundamental element of the concept is the electrolytic process. Solid electrolyte cells for extracting oxygen from gaseous feedstock are identified. The basic physical principles underlying the extraction process are analyzed, and the relations between the major parameters established. The laboratory equipment for experimental investigation of the process is presented.

Richter, R.; Ash, R.; Dowler, W.

1980-01-01

290

The spectral properties of interplanetary dust particles  

NASA Technical Reports Server (NTRS)

The observed spectral and mineralogical properties of interplanetary dust particles (IDP) allows the conclusion that: (1) the majority of IDP infrared spectra are dominated by olivine, pyroxene, or layer lattice silicate minerals, (2) to the first order the emission spectra of comets Halley and Kohoutek can be matched by mixtures of these IDP infrared types, implying that comets contain mixtures of these different crystalline silicates and may vary from comet to comet and perhaps even within a single comet, (3) do not expect to observe a single 20 micron feature in cometary spectra, (4) carbonaceous materials dominate the visible spectra properties of the IDPs even though the mass in these particles consists primarily of silicates, and (5) the particle characteristics summarized need to be properly accounted for in future cometary emission models.

Sandford, Scott A.

1988-01-01

291

Infrared Spectroscopy of Anhydrous Interplanetary Dust Particles  

NASA Technical Reports Server (NTRS)

Infrared (IR) spectroscopy is the primary means of mineralogical analysis of materials outside our solar system. The identity and properties of circumstellar grains are inferred from spectral comparisons between astronomical observations and laboratory data from natural and synthetic materials. These comparisons have been facilitated by the Infrared Space Observatory (ISO), which obtained IR spectra from numerous astrophysical objects over a wide spectral range (out to 50/cm) where crystalline silicates and other phases have distinct features. The anhydrous interplanetary dust particles (IDPs) are particularly important comparison materials because some IDPs contain carbonaceous material with non-solar D/H and N-15/N-14 ratios and amorphous and crystalline silicates with non-solar 0- isotopic ratios, demonstrating that these IDPs contain preserved interstellar material. Here, we report on micro- Fourier transform (FT) IR spectrometry of IDPs, focusing on the inorganic components of primitive IDPs (FTIR spectra from the organic/carbonacecous materials in IDPs are described elsewhere).

Keller, L. P.; Flynn, G. J.

2003-01-01

292

Interplanetary navigation using pulsating radio sources  

NASA Technical Reports Server (NTRS)

Radio beacons with distinguishing signatures exist in nature as pulsating radio sources (pulsars). These objects radiate well determined pulse trains over hundreds of megahertz of bandwidth at radio frequencies. Since they are at known positions, they can also be used as navigation beacons in interplanetary space. Pulsar signals are weak and dispersive when viewed from earth. If an omnidirectional antenna is connected to a wideband receiver (200 MHz bandwidth centered at 200 MHz) in which dispersion effects are removed, nominal spacecraft position errors of 1500 km can be obtained after 24 h of signal integration. An antenna gain of 10 db would produce errors as low as 150 km. Since the spacecraft position is determined from the measurement of the phase of a periodic signal, ambiguities occur in the position measurement. Simultaneous use of current spacecraft navigation schemes eliminates these ambiguities.

Downs, G. S.

1974-01-01

293

Interplanetary Particle Environment. Proceedings of a Conference  

NASA Technical Reports Server (NTRS)

A workshop entitled the Interplanetary Charged Particle Environment was held at the Jet Propulsion Laboratory (JPL) on March 16 and 17, 1987. The purpose of the Workshop was to define the environment that will be seen by spacecraft operating in the 1990s. It focused on those particles that are involved in single event upset, latch-up, total dose and displacement damage in spacecraft microelectronic parts. Several problems specific to Magellan were also discussed because of the sensitivity of some electronic parts to single-event phenomena. Scientists and engineers representing over a dozen institutions took part in the meeting. The workshop consisted of two major activities, reviews of the current state of knowledge and the formation of working groups and the drafting of their reports.

Feynman, Joan (editor); Gabriel, Stephen (editor)

1988-01-01

294

Interplanetary medium data book, supplement 5, 1988-1993  

NASA Technical Reports Server (NTRS)

This publication represents an extension of the series of Interplanetary Medium Data Books and supplements that have been issued by the National Space Science Data Center since 1977. This volume contains solar wind magnetic field and plasma data from the IMP 8 spacecraft for 1988 through the end of 1993. The normalization of the MIT plasma density and temperature, which has been discussed at length in previous volumes, is implemented as before, using the same normalization constants for 1988-1993 data as for the earlier data. Owing to a combination of non-continuity of IMP 8 telemetry acquisition and IMP's being out of the solar wind for about 40 percent of its orbit, the annual solar wind coverage for 1988-1993 is 40 plus or minus 5 percent. The plots and listings of this supplement are in essentially the same format as in previous supplements. Days for which neither IMF nor plasma data were available for any hours are omitted from the listings.

King, Joseph H.; Papitashvili, Natalia E.

1994-01-01

295

Multi-Spacecraft Observations of Interplanetary Shock Accelerated Particle Events  

NASA Technical Reports Server (NTRS)

We use simultaneous measurements from the Wind and ACE spacecraft to determine the spatial properties of both interplanetary (IP) shocks and the shock-associated energetic particle events. We combine plasma, magnetic field and energetic particle data from ACE and Wind for 124 energetic storm particle (ESP) events from 1998 to 2003 and examine the spatial and temporal variations of these events in the Earth's vicinity. We find that even though the two spacecraft were occasionally separated by more than 400 RE, the plasma, field, and energetic particle time-intensity profiles during the events were very similar. In addition, we find that the ion composition and energy spectra in individual IP shock events are identical at the two spacecraft locations. We also use the fitted shock velocity along the normal from ACE and estimate the shock transit time to Wind location. In general, there is poor agreement between the estimated transit time and the actual measured transit time. Hence, our assumptions that a) the IP shock at 1 AU propagates radially, and/or b) the IP shock is spherically symmetric at 1 AU are not valid. In this paper, we will also study, for the first time, the anisotropy measurements of low-energy IP shock-associated ions at both ACE and Wind. We will then compare these new anisotropy analyses with locally measured shock parameters and identify possible signatures of different shock acceleration processes as predicted by the first-order Fermi and shock-drift models.

Ho, G. C.; Lario, D.; Decker, R. B.; Desai, M. I.; Hu, Q.; Kasper, J.

2006-01-01

296

PARTICLE ENERGY SPECTRA AT TRAVELING INTERPLANETARY SHOCK WAVES  

SciTech Connect

We have searched for evidence of significant shock acceleration of He ions of {approx}1-10 MeV amu{sup -1} in situ at 258 interplanetary traveling shock waves observed by the Wind spacecraft. We find that the probability of observing significant acceleration, and the particle intensity observed, depends strongly upon the shock speed and less strongly upon the shock compression ratio. For most of the 39 fast shocks with significant acceleration, the observed spectral index agrees with either that calculated from the shock compression ratio or with the spectral index of the upstream background, when the latter spectrum is harder, as expected from diffusive shock theory. In many events the spectra are observed to roll downward at higher energies, as expected from Ellison-Ramaty and from Lee shock-acceleration theories. The dearth of acceleration at {approx}85% of the shocks is explained by (1) a low shock speed, (2) a low shock compression ratio, and (3) a low value of the shock-normal angle with the magnetic field, which may cause the energy spectra that roll downward at energies below our observational threshold. Quasi-parallel shock waves are rarely able to produce measurable acceleration at 1 AU. The dependence of intensity on shock speed, seen here at local shocks, mirrors the dependence found previously for the peak intensities in large solar energetic-particle events upon speeds of the associated coronal mass ejections which drive the shocks.

Reames, Donald V., E-mail: dvreames@umd.edu [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States)

2012-09-20

297

The accretion of interplanetary dust by Ap and Am stars  

NASA Technical Reports Server (NTRS)

Accretion of interplanetary dust and comets by A-type stars is investigated to see whether this process can explain the overabundances of heavy elements in Ap and Am stars. The dust particles spiral in by the Poynting-Robertson effect and evaporate above the star. This process is evaluated by considering the evolution of silicate and graphite particles in the radiation field of Alpha Leo (B7 V). It is found that graphite particles evaporate above 20 stellar radii and silicate dust grains above 50 stellar radii. The evaporated atoms will be quickly ionized. In the case of Am stars the ions will wander off and not reach the photosphere, but in the case of Ap stars they can be trapped by the magnetic field of the star and reach the surface. The magnetosphere of a typical Ap star is modeled, and the fate of the ions is studied. The efficiency of accretion from the magnetosphere is sensitive to the presence of any plasma in the magnetosphere. The comet impact process is found capable of producing the abundance anomalies in Ap as well as Am stars, assuming that the comet impact rate is 0.03/yr, nearly the same as in the solar system.

Kumar, C. Krishna; Davila, Joseph M.; Rajan, R. Sundar

1989-01-01

298

Particle Energy Spectra at Traveling Interplanetary Shock Waves  

NASA Astrophysics Data System (ADS)

We have searched for evidence of significant shock acceleration of He ions of ~1-10 MeV amu-1 in situ at 258 interplanetary traveling shock waves observed by the Wind spacecraft. We find that the probability of observing significant acceleration, and the particle intensity observed, depends strongly upon the shock speed and less strongly upon the shock compression ratio. For most of the 39 fast shocks with significant acceleration, the observed spectral index agrees with either that calculated from the shock compression ratio or with the spectral index of the upstream background, when the latter spectrum is harder, as expected from diffusive shock theory. In many events the spectra are observed to roll downward at higher energies, as expected from Ellison-Ramaty and from Lee shock-acceleration theories. The dearth of acceleration at ~85% of the shocks is explained by (1) a low shock speed, (2) a low shock compression ratio, and (3) a low value of the shock-normal angle with the magnetic field, which may cause the energy spectra that roll downward at energies below our observational threshold. Quasi-parallel shock waves are rarely able to produce measurable acceleration at 1 AU. The dependence of intensity on shock speed, seen here at local shocks, mirrors the dependence found previously for the peak intensities in large solar energetic-particle events upon speeds of the associated coronal mass ejections which drive the shocks.

Reames, Donald V.

2012-09-01

299

The Radiation, Interplanetary Shocks, and Coronal Sources (RISCS) Toolset  

NASA Technical Reports Server (NTRS)

We outline a plan to develop a physics based predictive toolset RISCS to describe the interplanetary energetic particle and radiation environment throughout the inner heliosphere, including at the Earth. To forecast and "nowcast" the radiation environment requires the fusing of three components: 1) the ability to provide probabilities for incipient solar activity; 2) the use of these probabilities and daily coronal and solar wind observations to model the 3D spatial and temporal heliosphere, including magnetic field structure and transients, within 10 AU; and 3) the ability to model the acceleration and transport of energetic particles based on current and anticipated coronal and heliospheric conditions. We describe how to address 1) - 3) based on our existing, well developed, and validated codes and models. The goal of RISCS toolset is to provide an operational forecast and "nowcast" capability that will a) predict solar energetic particle (SEP) intensities; b) spectra for protons and heavy ions; c) predict maximum energies and their duration; d) SEP composition; e) cosmic ray intensities, and f) plasma parameters, including shock arrival times, strength and obliquity at any given heliospheric location and time. The toolset would have a 72 hour predicative capability, with associated probabilistic bounds, that would be updated hourly thereafter to improve the predicted event(s) and reduce the associated probability bounds. The RISCS toolset would be highly adaptable and portable, capable of running on a variety of platforms to accommodate various operational needs and requirements.

Zank, G. P.; Spann, J.

2014-01-01

300

The average solar wind in the inner heliosphere: Structures and slow variations  

NASA Technical Reports Server (NTRS)

Measurements from the HELIOS solar probes indicated that apart from solar activity related disturbances there exist two states of the solar wind which might result from basic differences in the acceleration process: the fast solar wind (v 600 kms(-)1) emanating from magnetically open regions in the solar corona and the "slow" solar wind (v 400 kms(-)1) correlated with the more active regions and its mainly closed magnetic structures. In a comprehensive study using all HELIOS data taken between 1974 and 1982 the average behavior of the basic plasma parameters were analyzed as functions of the solar wind speed. The long term variations of the solar wind parameters along the solar cycle were also determined and numerical estimates given. These modulations appear to be distinct though only minor. In agreement with earlier studies it was concluded that the major modulations are in the number and size of high speed streams and in the number of interplanetary shock waves caused by coronal transients. The latter ones usually cause huge deviations from the averages of all parameters.

Schwenn, R.

1983-01-01

301

Modeling solar near-relativistic electron events. Insights into solar injection and interplanetary transport conditions  

NASA Astrophysics Data System (ADS)

Context: Solar near-relativistic electrons (>30 keV) are observed as discrete events in the inner heliosphere following different types of solar transient activity. Several mechanisms have been proposed for the production of these electrons. One candidate is related to solar flare activity. Other candidates include shocks driven by fast coronal mass ejections (CMEs) or processes of magnetic reconnection in the aftermath of CMEs. Aims: We study eleven near-relativistic (NR) electron events observed by the Advanced Composition Explorer (ACE) between 1998 and 2005 with the aim of estimating the roles played by solar flares, CME-driven shocks, and processes of magnetic restructuring in the aftermath of the CMEs in the injection of NR electrons. The main goal is to infer the underlying injection profile from particle observations at 1 AU, as well as the interplanetary transport conditions. Methods: We used Monte Carlo simulations to model the transport of particles along the interplanetary magnetic field. By taking the angular response of the LEFS60 telescope of the EPAM instrument onboard ACE into account, we were able to deconvolve the transport effects from the observed intensities, and thus infer the solar injection profile. Results: In this set of events, we have identified two types of injection episodes: short (<15 min) and time-extended (>1 h). Short injection episodes seem to be associated with the flare processes and/or the reconnection phenomena in the aftermath of the CME, while time-extended episodes seem to be consistent with injection from CME-driven shocks. Conclusions: We find that there is no single scenario that operates in all the events. The interplanetary propagation of NR electrons can occur both under strong scattering and under almost scatter-free propagation conditions and several injection phases (related to flares and/or CMEs) are possible.

Agueda, N.; Lario, D.; Vainio, R.; Sanahuja, B.; Kilpua, E.; Pohjolainen, S.

2009-11-01

302

Interplanetary shocks observed by STEREO during 2007-2012  

NASA Astrophysics Data System (ADS)

STEREO data have been very valuable to study the characteristics of interplanetary (IP) shocks. These shocks can be driven by fast interplanetary coronal mass ejections (CME) and by solar wind stream interactions (SI). In this work we discuss the properties of IP shocks and the upstream and downstream regions associated to them. These regions are perturbed due to shock effects. Upstream from the shock a foreshock can develop and be permeated by suprathermal ions and electromagnetic waves. Downstream the plasma is heated and compressed. In this region the magnetic field is also very perturbed. Shocks play a very important role in particle acceleration. During the years of the extended solar minimum (2007-2010) STEREO observed around 80 IP forward shocks driven by stream interactions, and 19 shocks driven by ICMEs. Most of the SI shocks were locally quasi-perpendicular (?Bn >45°) with only 20 quasi-parallel (?Bn < 45°) shocks. In all cases the Mach number was moderate with values 1.1< Mms < 3.8, and the plasma beta reached values up to 29. During the same years the shocks driven by ICMEs have Mach numbers 1.2-4, and plasma beta up to 15. Measurements upstream from the shocks have revealed a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. In contrast to planetary bow shocks, most of the waves upstream of the quasi-parallel forward SI shocks observed until 2010 by STEREO are mainly transverse and no steepening occurs. Another difference with Earth's bow shock is the fact that many locally quasi-perpendicular shocks can be accompanied by wave and ion foreshocks. This indicates that at an earlier time the geometry of the shock was quasi-parallel. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. Downstream fluctuations associated with quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr ?0.05 AU. This is smaller than foreshock extensions for ICME driven shocks (dr ? 0.1 AU). The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at ~1 AU and have been producing suprathermal particles for a shorter time. During the last two years (2011-2012) the rate of interplanetary shock observations increased dramatically with around 140 events. In this work we extend our study to include these IP shocks and determine if stronger shocks lead to significant changes in wave spectra, shock profile and foreshock extensions.

Blanco-Cano, X.; Kajdic, P.; Aguilar-Rodriguez, E.; Russell, C. T.; Jian, L.; Luhmann, J. G.

2013-12-01

303

Direct penetration of the interplanetary electric field to low geomagnetic latitudes and its effect on magnetotelluric sounding  

NASA Astrophysics Data System (ADS)

Long-term monitoring of geoelectromagnetic fields, recorded with a network of nine stations covering an area of approximately 25,000 km2 at low geomagnetic latitudes in northern Chile, reveals systematic and seasonally modulated variations of geomagnetic field properties. The observed seasonal variation affects almost exclusively the east-west magnetic field component for periods between 100 and 3000 s. The ground-based measurements of magnetic and electric fields show statistically significant coherences with the interplanetary electric field derived from solar wind and interplanetary magnetic field data of the Advanced Composition Explorer satellite. The interplanetary electric field (IEF) penetrates the polar ionosphere from where it propagates toward equatorial latitudes by waveguide transmission, with ionosphere and solid Earth acting as conducting boundaries. Signal coherence between IEF and ground data peaks at periods of approximately 90 min and up to the four harmonics. Coherence values reach 0.4 at these periods and depend on the electromagnetic field component. They vary with season and local time. Transfer functions computed between IEF and ground-based electric and magnetic fields show local maxima at similar periods (90 min and harmonics). The coupling between the east-west magnetic field component and the IEF shows significant seasonal variability, much larger than the other electromagnetic field components. We conclude that the IEF drives primarily a global circuit of Pedersen currents in the ionosphere. Resulting time-varying magnetic fields induce electric currents in the ground. Related ground-based magnetic (primarily north-south) and electric (primarily east-west) signals vary coherently at all local times and seasons. Conversely, magnetic signals caused by the IEF-driven Hall currents depend much on local time and season. We show for the first time that these ionospheric Hall currents cause no induction in the ground, but they generate magnetic signatures that are confined to the waveguide between ionosphere and Earth's surface.

Brändlein, Dirk; Lühr, Hermann; Ritter, Oliver

2012-11-01

304

Heat conduction in a turbulent magnetic field, with application to solar-wind electrons.  

NASA Technical Reports Server (NTRS)

Consideration of random, long-wavelength fluctuations in a turbulent magnetic field, showing that they can appreciably decrease the heat conductivity of a plasma along the magnetic field. In simple cases of interest, the reduction along the average field is approximately by the factor (cos delta theta) squared, where delta theta is the angle of the local magnetic field relative to the average field. Application to solar-wind electrons indicates that this reduction in heat conductivity due to observed fluctuations in the interplanetary magnetic field may be of the order of a factor of 2. This may help to explain recent measurements which indicate a rather low electron heat flux in the solar wind.

Hollweg, J. V.; Jokipii, J. R.

1972-01-01

305

Solar magnetic fields - Extended.  

NASA Technical Reports Server (NTRS)

Spacecraft observations of the interplanetary magnetic field have revealed that almost always each solar rotation can be divided into sectors, within each of which the field has a predominant polarity toward the sun or away from the sun. Comparisons of this interplanetary magnetic sector pattern with observations of the photospheric magnetic field have revealed a similar solar magnetic pattern. The boundaries between solar magnetic sectors are approximately in the north-south direction over a wide range of latitudes on both sides of the equator. This solar magnetic sector structure can be described as a rotating dipole whose magnetic axis makes an angle of approximately 90 deg with the axis of rotation. Possible similarities between this solar-sector magnetism and the models derived from observations of stellar magnetism are discussed.

Wilcox, J. M.

1971-01-01

306

Overview of cosmic rays, solar and interplanetary physics research (1987-1990)  

SciTech Connect

A brief survey of recent U.S. investigations in the field of heliospheric plasmas and their manifestations is presented, introducing the following collection of detailed reviews (accessions A91-46959 to A91-46964). Topics examined include the large-scale structure of interplanetary plasmas, models of Galactic cosmic-ray production and propagation, solar-wind turbulence, long-period solar-terrestrial variability, the possible relation between solar-neutrino counts and the sunspot cycle, X-ray studies of solar flares and their implications for solar processes, and the near-sun magnetic field.

Jokipii, J.R. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

307

On the use of Godhavn H-component as an indicator of the interplanetary sector polarity  

NASA Technical Reports Server (NTRS)

An objective method of inferring the polarity of the interplanetary magnetic field using the H-component at Godhavn is presented. The objectively inferred polarities are compared with a subjective index inferred earlier. It is concluded that no significant difference exists between the two methods. The inferred polarities derived from Godhavn H is biased by the (slp) sub q signature in the sense that during summer prolonged intervals of geomagnetic calm will result in inferred Away polarity regardless of the actual sector polarity. This bias does not significantly alter the large scale structure of the inferred sector structure.

Svalgaard, L.

1974-01-01

308

On the use of Godhavn H component as an indicator of the interplanetary sector polarity  

NASA Technical Reports Server (NTRS)

An objective method of inferring the polarity of the interplanetary magnetic field using the H component at Godhavn is presented. The objectively inferred polarities are compared with a subjective index inferred earlier (Svalgaard, 1972b). It is concluded that no significant difference exists between the two methods. The inferred polarities derived from Godhavn H are biased by the Sq-p signature in the sense that during summer, prolonged intervals of geomagnetic calm will result in inferred away polarity regardless of the actual sector polarity. This bias does not significantly alter the large-scale structure of the inferred sector structure.

Svalgaard, L.

1975-01-01

309

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS)  

E-print Network

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS) Patrick C. Crane 12 January scintillation (IPS) is the random fluctuation in the intensity and phase of electromagnetic waves passing

Ellingson, Steven W.

310

Nano-Diamonds in Chondritic Interplanetary Dust Particles  

NASA Technical Reports Server (NTRS)

In-situ acid etching of ultramicrotomed thin sections has lead to the identification of nano-diamonds in interplanetary dust particles. Additional information is contained in the original extended abstract.

Dai, Z. R.; Joswiak, D. J.; Bradley, J. P.; Brownlee, D. E.; Hill, H. G. M.

2001-01-01

311

Application of ion electrospray propulsion to lunar and interplanetary missions  

E-print Network

High specific impulse electric propulsion systems enable ambitious lunar and interplanetary missions that return a wealth of scientific data. Many of these technologies are difficult to scale down, meaning the spacecraft ...

Whitlock, Caleb W. (Caleb Wade)

2014-01-01

312

CME Interaction with Coronal Holes and Their Interplanetary Consequences  

NASA Technical Reports Server (NTRS)

A significant number of interplanetary (IP) shocks (-17%) during cycle 23 were not followed by drivers. The number of such "driverless" shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the central meridian of the Sun (within approx.15deg), which is quite unexpected. More interestingly, all the driverless shocks with their solar sources near the solar disk center occurred during the declining phase of solar cycle 23. When we investigated the coronal environment of the source regions of driverless shocks, we found that in each case there was at least one coronal hole nearby suggesting that the coronal holes might have deflected the associated coronal mass ejections (CMEs) away from the Sun-Earth line. The presence of abundant low-latitude coronal holes during the declining phase further explains why CMEs originating close to the disk center mimic the limb CMEs, which normally lead to driverless shocks due to purely geometrical reasons. We also examined the solar source regions of shocks with drivers. For these, the coronal holes were located such that they either had no influence on the CME trajectories. or they deflected the CMEs towards the Sun-Earth line. We also obtained the open magnetic field distribution on the Sun by performing a potential field source surface extrapolation to the corona. It was found that the CMEs generally move away from the open magnetic field regions. The CME-coronal hole interaction must be widespread in the declining phase, and may have a significant impact on the geoeffectiveness of CMEs.

Gopalswamy, N.; Makela, P.; Xie, H.; Akiyama, S.; Yashiro, S.

2008-01-01

313

Relationship between PC index and interplanetary electric field EKL under actual conditions of varying solar wind  

NASA Astrophysics Data System (ADS)

The PC index was introduced as an indicator of magnetic activity in the polar caps generated by the geoeffective interplanetary electric field E _{KL} determined in accordance with Kan and Lee [1979]. The PC index is calculated basing on magnetic data (?F) from near-pole stations Thule and Vostok with use of the statistically justified coefficients of regression ? and ? linking the polar cap magnetic disturbance vectors ?F with the electric field E _{KL}. As a result, the PC index is defined as a value of the polar cap magnetic disturbance standardized with the intensity of the interplanetary electric field EKL regardless of season, UT and hemisphere. Statistically the appropriate values PC and E _{KL} well correlate, however in concrete situations PC and E _{KL} may be quite differ, because E _{KL} characterizes the state of the solar wind far upstream of the magnetosphere, whereas PC characterizes the energy that entered into magnetosphere, Analysis of consistencies and discrepancies between PC and E _{KL} under conditions of different solar wind parameters was carried for all events with magnetic substorms (N=1798) and magnetic storms (N=203) observed in epoch of maximal solar activity (1998-2001). Thus, the solar wind geoefficiency was estimated by independent indicators, such as AL and Dst indices characterizing magnetic activity within the magnetosphere. The essential attention was given also to geoefficiency of sudden pulses of the solar wind dynamic pressure. The results of the analysis were applied to derive the method to nowcast the magnetosphere state, including estimation of the “model PC, AL and Dst” indices calculated by actual measurement of E _{KL} in the point L1 under conditions of varying solar wind. It is demonstrated that the PC index can be successfully used to monitor space weather and the readiness of the magnetosphere to producing substorm or storm.

Troshichev, Oleg; Smirnov, Michael

314

Interhemispheric comparison of average substorm onset locations: evidence for deviation from conjugacy  

NASA Astrophysics Data System (ADS)

Based on 2760 well-defined substorm onsets in the Northern Hemisphere and 1432 in the Southern Hemisphere observed by the FUV Imager on board the IMAGE spacecraft, a detailed statistical study is performed including both auroral regions. This study focuses on the hemispheric comparisons. Southward pointing interplanetary magnetic field (IMF) is favorable for substorm to occur, but still 30% of the events are preceded by northward IMF. The magnetic latitude (MLat) of substorm onset depends mainly on the merging electric field (Em) with a relationship of |dMLat|= -5.2 Em0.5, where dMLat is the deviation from onset MLat. In addition, seasonal effects on onset MLat are also detected, with about 2 degrees higher latitudes during solstices than equinoxes. Both IMF By and solar illumination have a significant influence on the magnetic local time (MLT) of onsets. An average relation, dMLT=0.25 By between IMF By and the deviation from onset MLT, was found. The By dependence varies slightly with the onset latitude. At lower latitudes (higher activity) it is reduced. After removal of the relationship with IMF By a linear relationships remains between the solar zenith angle and onset MLT with dMLT=1 min/deg. Therefore, both solar illumination and IMF By can contribute to hemispheric longitudinal displacements of substorm onset locations from conjugacy. No indications for systematic latitudinal displacements between the hemispheres have been found.

Wang, H.; Lühr, H.; Ma, S. Y.; Frey, H. U.

2007-05-01

315

Magnetic field sector structure and origins of solar wind streams in 2012  

NASA Astrophysics Data System (ADS)

The origins of the solar wind and the interplanetary magnetic field sector structure in the beginning of the magnetic polarity reversal of 24th solar cycle were investigated using the Wilcox Solar Observatory magnetic field measurements and their products as well as the solar wind data from ACE and the SDO/AIA EUV images. The dominance of the quadrupole harmonics in the solar magnetic field in this period resulted in a four-sector structure of the interplanetary magnetic field. The dominating source of recurrent high-speed solar wind stream was a large trans-equatorial coronal hole of negative polarity evolving in the course of the polarity reversal process. The contribution of ICMEs to the high-speed solar wind did not exceed 17% of the total flux. The solar wind density flux averaged over the year amounted to 1 × 108 cm-2 s-1 which is considerably lower than the typical long-term value (2-4 × 108 cm-2 s-1). The slow-speed component of solar wind density flux constituted in average more than 68% of the total flux, the high-speed component was about 10%, reaching the maximum of 32% in some Carrington rotations.

Shugay, Yulia; Slemzin, Vladimir; Veselovsky, Igor

2014-08-01

316

Global Magnetospheric Response to an Interplanetary Shock: THEMIS Observations  

NASA Technical Reports Server (NTRS)

We investigate the global response of geospace plasma environment to an interplanetary shock at approx. 0224 UT on May 28, 2008 from multiple THEMIS spacecraft observations in the magnetosheath (THEMIS B and C) and the mid-afternoon (THEMIS A) and dusk magnetosphere (THEMIS D and E). The interaction of the transmitted interplanetary shock with the magnetosphere has global effects. Consequently, it can affect geospace plasma significantly. After interacting with the bow shock, the interplanetary shock transmitted a fast shock and a discontinuity which propagated through the magnetosheath toward the Earth at speeds of 300 km/s and 137 km/s respectively. THEMIS A observations indicate that the plasmaspheric plume changed significantly by the interplanetary shock impact. The plasmaspheric plume density increased rapidly from 10 to 100/ cubic cm in 4 min and the ion distribution changed from isotropic to strongly anisotropic distribution. Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are most likely excited by the anisotropic ion distributions caused by the interplanetary shock impact. To our best knowledge, this is the first direct observation of the plasmaspheric plume response to an interplanetary shock's impact. THEMIS A, but not D or E, observed a plasmaspheric plume in the dayside magnetosphere. Multiple spacecraft observations indicate that the dawn-side edge of the plasmaspheric plume was located between THEMIS A and D (or E).

Zhang, Hui; Sibeck, David G.; Zong, Q.-G.; McFadden, James P.; Larson, Davin; Glassmeier, K.-H.; Angelopoulos, V.

2011-01-01

317

BACODINE/3rd Interplanetary Network burst localization  

SciTech Connect

Even with only two widely separated spacecraft (Ulysses and GRO), 3rd Interplanetary Network (IPN) localizations can reduce the areas of BATSE error circles by two orders of magnitude. Therefore it is useful to disseminate them as quickly as possible following BATSE bursts. We have implemented a system which transmits the light curves of BACODINE/BATSE bursts directly by e-mail to UC Berkeley immediately after detection. An automatic e-mail parser at Berkeley watches for these notices, determines the Ulysses crossing time window, and initiates a search for the burst data on the JPL computer as they are received. In ideal cases, it is possible to retrieve the Ulysses data within a few hours of a burst, generate an annulus of arrival directions, and e-mail it out to the astronomical community by local nightfall. Human operators remain in this loop, but we are developing a fully automated routine which should remove them, at least for intense events, and reduce turn-around times to an absolute minimum. We explain the current operations, the data types used, and the speed/accuracy tradeoffs.

Hurley, K.; Barthelmy, S.; Butterworth, P.; Cline, T.; Sommer, M.; Boer, M.; Niel, M.; Kouveliotou, C.; Fishman, G.; Meegan, C. [University of California Space Sciences Laboratory Berkeley, California 94720-7450 (United States); NASA Goddard Space Flight Center Greenbelt, Maryland 20771 (United States); Max-Planck Institut fuer Extraterrestrische Physik, 85740 Garching (Germany); Centre d'Etude Spatiale des Rayonnements, 31029 Toulouse Cedex (France); NASA Marshall Space Flight Center Huntsville, Alabama 35812 (United States)

1996-08-01

318

Inward electrostatic precipitation of interplanetary particles  

NASA Technical Reports Server (NTRS)

An inward precipitator collects particles initially dispersed in a gas throughout either a cylindrical or spherical chamber onto a small central planchet. The instrument is effective for particle diameters greater than about 1 micron. One use is the collection of interplanetary dust particles (IDPs) which are stopped in a noble gas (xenon) by drag and ablation after perforating the wall of a thin-walled spacecraft-mounted chamber. First, the particles are positively charged for several seconds by the corona production of positive xenon ions from inward facing needles placed on the chamber wall. Then an electric field causes the particles to migrate toward the center of the instrument and onto the planchet. The collection time (on the order of hours for a 1 m radius spherical chamber) is greatly reduced by the use of optimally located screens which reapportion the electric field. Some of the electric field lines terminate on the wires of the screens so a fraction of the total number of particles in the chamber is lost. The operation of the instrument is demonstrated by experiments which show the migration of carbon soot particles with radius of approximately 1 micron in a 5 cm diameter cylindrical chamber with a single field enhancing screen toward a 3.2 mm central collection rod.

Rulison, Aaron J.; Flagan, Richard C.; Ahrens, Thomas J.

1993-01-01

319

Volatiles in interplanetary dust particles and aerogels  

NASA Technical Reports Server (NTRS)

Volatiles measured in 25 interplanetary dust particles (IDPs) are a mixture of both indigenous materials and contaminants associated with the collection and processing of the ODPs prior to analysis. Most IDPs have been collected in the stratosphere using a silicone oil/freon mixture (20:1 ratio) coated on collector plates. Studies have shown that silicone oil, freon and hexane residues remain with the ODPs, despite attempts to clean the IDPs. Analysis of the IDPs with the LMMS-technique produces spectra with a mixture of indigeneous and contaminants components. The contamination signal can be identified and removed; however, the contamination signal may obscure some of the indigeneous component's signal. Employing spectra stripping techniques, the indigenous volatile constituents associated with the IDPs can be identified. Volatiles are similar to those measured in CI or CM carbonaceous chondrites. Collection of IDPs in low-Earth orbit utilizing a Cosmic Dust Collection Facility attached to Space Station Freedom has been proposed. The low-density material aerogel has been proposed as a collection substrate for IDPs. Our studies have concentrated on identifying volatile contaminants that are associated with aerogel. We have found that solvents used for the preparation of aerogel remain in aerogel and methods must be developed for removing the entrapped solvents before aerogels can be used for an IDP collection substrate.

Gibson, E. K., Jr.; Harmetz, C. P.

1991-01-01

320

Mars interplanetary trajectory design via Lagrangian points  

NASA Astrophysics Data System (ADS)

With the increase in complexities of interplanetary missions, the main focus has shifted to reducing the total delta-V for the entire mission and hence increasing the payload capacity of the spacecraft. This paper develops a trajectory to Mars using the Lagrangian points of the Sun-Earth system and the Sun-Mars system. The whole trajectory can be broadly divided into three stages: (1) Trajectory from a near-Earth circular parking orbit to a halo orbit around Sun-Earth Lagrangian point L2. (2) Trajectory from Sun-Earth L2 halo orbit to Sun-Mars L1 halo orbit. (3) Sun-Mars L1 halo orbit to a circular orbit around Mars. The stable and unstable manifolds of the halo orbits are used for halo orbit insertion. The intermediate transfer arcs are designed using two-body Lambert's problem. The total delta-V for the whole trajectory is computed and found to be lesser than that for the conventional trajectories. For a 480 km Earth parking orbit, the total delta-V is found to be 4.6203 km/s. Another advantage in the present approach is that delta-V does not depend upon the synodic period of Earth with respect to Mars.

Eapen, Roshan Thomas; Sharma, Ram Krishan

2014-09-01

321

Raman observations on individual interplanetary dust particles  

NASA Astrophysics Data System (ADS)

A Raman study of 20 representative interplanetary dust particles (IDPs) belonging to different infrared spectral classes is discussed. Six different groups of Raman spectra were discerned among the IDPs studied. Groups 1-5 exhibit the Raman signature of poorly crystallized carbonaceous material, with the degree of disorder of this material increasing from group 1 (most ordered) to group 5 (least ordered). Group 1 contains IDPs that have infrared spectra characteristic of olivines, and are deuterium depleted, while those in groups 2, 3, and 4 contain less ordered carbonaceous material and are deuterium enriched, suggesting different carbonaceous carrier phases for deuterium depletions and enrichments. Groups 5 and 6 contain little or no carbonaceous material, with an abundance of deuterium. No obvious relationship was found between Raman groups and infrared classes based on the 10 micron absorption band due to silicates. Because silicates are known to be present, but are not seen, it is presumed that silicate grains are coated with and/or imbedded in carbonaceous material. Several IDPs show broad visible laser-induced photoluminescence, probably produced by a carbonaceous component.

Wopenka, B.

1988-05-01

322

The WIND magnetic field investigation  

Microsoft Academic Search

The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and

R. P. Lepping; M. H. Ac?na; L. F. Burlaga; W. M. Farrell; J. A. Slavin; K. H. Schatten; F. Mariani; N. F. Ness; F. M. Neubauer; Y. C. Whang; J. B. Byrnes; R. S. Kennon; P. V. Panetta; J. Scheifele; E. M. Worley

1995-01-01

323

THE LONGITUDINAL TRANSPORT OF ENERGETIC IONS FROM IMPULSIVE SOLAR FLARES IN INTERPLANETARY SPACE  

SciTech Connect

We present a study of the longitudinal spread of energetic charged particles from a localized instantaneous compact source on the Sun. Our study utilizes a diffusive-transport model for the propagation of energetic ions in interplanetary space. We show that even for very small values of the ratio of perpendicular to parallel diffusion coefficients-a few percent-the particles spread significantly in longitude. Spatial diffusion and adiabatic energy loss of ions in the interplanetary plasma cause impulsive particle events at Earth's orbit to last a few days. In this time, the combination of transport both along and across the local Parker-spiral magnetic field and the longitudinal motion of the magnetic lines of forces rooted at the Sun as it rotates leads to substantial longitudinal transport of the particles. We show that spacecraft separated by as much as 180 Degree-Sign or more may observe events associated with compact solar sources, such as those from impulsive solar flares. Our results are qualitatively consistent with recent multi-spacecraft observations.

Giacalone, J.; Jokipii, J. R. [Department of Planetary Sciences, University of Arizona, Tucson, AZ (United States)

2012-06-01

324

The Longitudinal Transport of Energetic Ions from Impulsive Solar Flares in Interplanetary Space  

NASA Astrophysics Data System (ADS)

We present a study of the longitudinal spread of energetic charged particles from a localized instantaneous compact source on the Sun. Our study utilizes a diffusive-transport model for the propagation of energetic ions in interplanetary space. We show that even for very small values of the ratio of perpendicular to parallel diffusion coefficients—a few percent—the particles spread significantly in longitude. Spatial diffusion and adiabatic energy loss of ions in the interplanetary plasma cause impulsive particle events at Earth's orbit to last a few days. In this time, the combination of transport both along and across the local Parker-spiral magnetic field and the longitudinal motion of the magnetic lines of forces rooted at the Sun as it rotates leads to substantial longitudinal transport of the particles. We show that spacecraft separated by as much as 180° or more may observe events associated with compact solar sources, such as those from impulsive solar flares. Our results are qualitatively consistent with recent multi-spacecraft observations.

Giacalone, J.; Jokipii, J. R.

2012-06-01

325

Interplanetary Overlay Network Bundle Protocol Implementation  

NASA Technical Reports Server (NTRS)

The Interplanetary Overlay Network (ION) system's BP package, an implementation of the Delay-Tolerant Networking (DTN) Bundle Protocol (BP) and supporting services, has been specifically designed to be suitable for use on deep-space robotic vehicles. Although the ION BP implementation is unique in its use of zero-copy objects for high performance, and in its use of resource-sensitive rate control, it is fully interoperable with other implementations of the BP specification (Internet RFC 5050). The ION BP implementation is built using the same software infrastructure that underlies the implementation of the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) built into the flight software of Deep Impact. It is designed to minimize resource consumption, while maximizing operational robustness. For example, no dynamic allocation of system memory is required. Like all the other ION packages, ION's BP implementation is designed to port readily between Linux and Solaris (for easy development and for ground system operations) and VxWorks (for flight systems operations). The exact same source code is exercised in both environments. Initially included in the ION BP implementations are the following: libraries of functions used in constructing bundle forwarders and convergence-layer (CL) input and output adapters; a simple prototype bundle forwarder and associated CL adapters designed to run over an IPbased local area network; administrative tools for managing a simple DTN infrastructure built from these components; a background daemon process that silently destroys bundles whose time-to-live intervals have expired; a library of functions exposed to applications, enabling them to issue and receive data encapsulated in DTN bundles; and some simple applications that can be used for system checkout and benchmarking.

Burleigh, Scott C.

2011-01-01

326

INITIAL RESULTS OF THE IMP I MAGNETIC FIELD EXPERIMENT  

Microsoft Academic Search

The interplanetary monitoring platform Imp 1, or Explorer 18, launched on No- vember 27, 1963, has provided the first accurate measurements of interplanetary magnetic fields. The initial apogee of the satellite was 197,616 km on the sunlit side of the earth, with an apogee-earth-sun angle of 26 ø . This paper presents the initial results of the detailed meas- urements

Norman F. Ness; Clell S. Scearce; Joseph B. Seek

1964-01-01

327

Dayside Global Ionospheric Response to the Major Interplanetary Events of October 29-30, 2003 ''Halloween Storms''  

NASA Technical Reports Server (NTRS)

We demonstrate extreme ionospheric response to the large interplanetary electric fields during the "Halloween" storms that occurred on October 29 and 30, 2003. Within a few (2 - 5) hours of the time when the enhanced interplanetary electric field impinged on the magnetopause, dayside total electron content increases of approx.40% and approx.250% are observed for the October 29 and 30 events, respectively. During the Oct 30 event, approx.900% increases in electron content above the CHAMP satellite (approx.400 km altitude) were observed at mid-latitudes (+/-30 degrees geomagnetic). The geomagnetic storm-time phenomenon of prompt penetration electric fields is a possible contributing cause of these electron content increases, producing dayside ionospheric uplift combined with equatorial plasma diffusion along magnetic field lines to higher latitudes, creating a "daytime super-fountain" effect.

Mannucci, A. J.; Tsurutani, B. T.; Iijima, B. A.; Komjathy, A.; Saito, A.; Gonzalez, W. D.; Guarnieri, F. L.; Kozyra, J. U.; Skoug, R.

2005-01-01

328

Interhemispheric comparison of average substorm onset locations: evidence for deviation from conjugacy  

Microsoft Academic Search

Based on 2760 well-defined substorm onsets in the Northern Hemisphere and 1432 in the Southern Hemisphere observed by the FUV Imager on board the IMAGE spacecraft, a detailed statistical study is performed including both auroral regions. This study focuses on the hemispheric comparisons. Southward pointing interplanetary magnetic field (IMF) is favorable for substorm to occur, but still 30% of the

H. Wang; H. Lühr; S. Y. Ma; H. U. Frey

2007-01-01

329

Interplanetary MeV electrons of Jovian origin  

NASA Technical Reports Server (NTRS)

Observations of low energy electron increases observed in interplanetary space on Pioneer 10 are reported as it approached Jupiter. These discrete bursts were several hundred times the normal quiet-time electron flux, and became more frequent as one approached Jupiter resulting in the quasi-continuous presence of large fluxes of these electrons in interplanetary space. It is noted that the integrated flux from quiet-time electrons is comparable to the integrated ambient electron flux itself. In addition, the spectrum of electrons observed in Jupiter's magnetosphere, on Pioneer 10 in interplanetary space near Jupiter, for the quiet-time increases near the earth, and for the ambient electron spectrum are all remarkably similar. These two lines of evidence suggest the possibility that Jupiter could be the source of most of the ambient electrons at low energies.

Teegarden, B. J.; Mcdonald, F. B.; Trainor, J. H.; Webber, W. R.; Roelof, E. C.

1974-01-01

330

Conceptual Design For Interplanetary Spaceship Discovery  

NASA Astrophysics Data System (ADS)

With the recently revived national interest in Lunar and Mars missions, this design study was undertaken by the author in an attempt to satisfy the long-term space exploration vision of human travel ``to the Moon, Mars, and beyond'' with a single design or family of vehicles. This paper describes a conceptual design for an interplanetary spaceship of the not-to-distant future. It is a design that is outwardly similar to the spaceship Discovery depicted in the novel ``2001 - A Space Odyssey'' and film of the same name. Like its namesake, this spaceship could one day transport a human expedition to explore the moons of Jupiter. This spaceship Discovery is a real engineering design that is capable of being implemented using technologies that are currently at or near the state-of-the-art. The ship's main propulsion and electrical power are provided by bi-modal nuclear thermal rocket engines. Configurations are presented to satisfy four basic Design Reference Missions: (1) a high-energy mission to Jupiter's moon Callisto, (2) a high-energy mission to Mars, (3) a low-energy mission to Mars, and (4) a high-energy mission to the Moon. The spaceship design includes dual, strap-on boosters to enable the high-energy Mars and Jupiter missions. Three conceptual lander designs are presented: (1) Two types of Mars landers that utilize atmospheric and propulsive braking, and (2) a lander for Callisto or Earth's Moon that utilizes only propulsive braking. Spaceship Discovery offers many advantages for human exploration of the Solar System: (1) Nuclear propulsion enables propulsive capture and escape maneuvers at Earth and target planets, eliminating risky aero-capture maneuvers. (2) Strap-on boosters provide robust propulsive energy, enabling flexibility in mission planning, shorter transit times, expanded launch windows, and free-return abort trajectories from Mars. (3) A backup abort propulsion system enables crew aborts at multiple points in the mission. (4) Clustered NTR engines provide ``engine out'' redundancy. (5) The design efficiently implements galactic cosmic ray shielding using main propellant liquid hydrogen. (6) The design provides artificial gravity to mitigate crew physiological problems on long-duration missions. (7) The design is modular and can be launched using the proposed upgrades to the Evolved Expendable Launch Vehicles or Shuttle-derived heavy lift launch vehicles. (8) High value modules are reusable for Mars and Lunar missions. (9) The design has inherent growth capability, and can be tailored to satisfy expanding mission requirements to enable an in-family progression ``to the Moon, Mars, and beyond.''

Benton, Mark G.

2006-01-01

331

Linked Autonomous Interplanetary Satellite Orbit Navigation  

NASA Technical Reports Server (NTRS)

A navigation technology known as LiAISON (Linked Autonomous Interplanetary Satellite Orbit Navigation) has been known to produce very impressive navigation results for scenarios involving two or more cooperative satellites near the Moon, such that at least one satellite must be in an orbit significantly perturbed by the Earth, such as a lunar halo orbit. The two (or more) satellites track each other using satellite-to-satellite range and/or range-rate measurements. These relative measurements yield absolute orbit navigation when one of the satellites is in a lunar halo orbit, or the like. The geometry between a lunar halo orbiter and a GEO satellite continuously changes, which dramatically improves the information content of a satellite-to-satellite tracking signal. The geometrical variations include significant out-of-plane shifts, as well as inplane shifts. Further, the GEO satellite is almost continuously in view of a lunar halo orbiter. High-fidelity simulations demonstrate that LiAISON technology improves the navigation of GEO orbiters by an order of magnitude, relative to standard ground tracking. If a GEO satellite is navigated using LiAISON- only tracking measurements, its position is typically known to better than 10 meters. If LiAISON measurements are combined with simple radiometric ground observations, then the satellite s position is typically known to better than 3 meters, which is substantially better than the current state of GEO navigation. There are two features of LiAISON that are novel and advantageous compared with conventional satellite navigation. First, ordinary satellite-to-satellite tracking data only provides relative navigation of each satellite. The novelty is the placement of one navigation satellite in an orbit that is significantly perturbed by both the Earth and the Moon. A navigation satellite can track other satellites elsewhere in the Earth-Moon system and acquire knowledge about both satellites absolute positions and velocities, as well as relative positions and velocities in space. The second novelty is that ordinarily one requires many satellites in order to achieve full navigation of any given customer s position and velocity over time. With LiAISON navigation, only a single navigation satellite is needed, provided that the satellite is significantly affected by the gravity of the Earth and the Moon. That single satellite can track another satellite elsewhere in the Earth- Moon system and obtain absolute knowledge of both satellites states.

Parker, Jeffrey S.; Anderson, Rodney L.; Born, George H.; Leonard, Jason M.; McGranaghan, Ryan M.; Fujimoto, Kohei

2013-01-01

332

Effect of Lunar Gravity Assist on interplanetary trajectories  

NASA Astrophysics Data System (ADS)

The concept of utilizing Lunar Gravity Assist to improve interplanetary missions was outlined circa 1957. Performance improvements are small, and guidance requirements are severe, but achievable. Low Energy interplanetary missions benefit the most, for example, trips to Mars and Venus. The previous analysis is extended to precursor Delta V EGA type trajectories, and comet and asteroid flybys. Single and double lunar swingbys are considered. Total mission flight times increase by 3-60 days, or more. Alternative launch windows become available. Payloads may be increased by 5-15 percent, to Mars.

Vaning, Walker S.; Fay, John F.

1991-08-01

333

Optical spectroscopy of interplanetary dust collected in the earth's stratosphere  

NASA Technical Reports Server (NTRS)

Optical absorption spectra of interplanetary dust particles 2-30 microns in size collected in the atmosphere at an altitude of 20 km by inertial impactors mounted on NASA U-2 aircraft are reported. Fourier transform absorption spectroscopy of crushed samples of the particles reveals a broad feature in the region 1300-800 kaysers which has also been found in meteorite and cometary dust spectra, and a weak iron crystal field absorption band at approximately 9800 kaysers, as is observed in meteorites. Work is currently in progress to separate the various components of the interplanetary dust particles in order to evaluate separately their contributions to the absorption.

Fraundorf, P.; Patel, R. I.; Shirck, J.; Walker, R. M.; Freeman, J. J.

1980-01-01

334

The Radiation, Interplanetary Shocks, and Coronal Sources (RISCS) Toolset  

NASA Technical Reports Server (NTRS)

The goal of this project is to serve the needs of space system designers and operators by developing an interplanetary radiation environment model within 10 AU:Radiation, Interplanetary Shocks, and Coronal Sources (RISCS) toolset: (1) The RISCS toolset will provide specific reference environments for space system designers and nowcasting and forecasting capabilities for space system operators; (2) We envision the RISCS toolset providing the spatial and temporal radiation environment external to the Earth's (and other planets') magnetosphere, as well as possessing the modularity to integrate separate applications (apps) that can map to specific magnetosphere locations and/or perform the subsequent radiation transport and dosimetry for a specific target.

Zank, G. P.; Spann, James F.

2014-01-01

335

Interplanetary Overlay Network (ION) for Long-Delay Communications with Asymmetric Channel Rates  

Microsoft Academic Search

Interplanetary Overlay Network (ION) is an implementation of delay\\/disruption tolerant networking (DTN) developed as infrastructure for space communications in interplanetary flight mission systems. To date, no work has been done in evaluating the effectiveness of ION when it is applied to an interplanetary Internet involving very long link delay and highly asymmetric channel rates. In this paper, we present an

Ruhai Wang; Vivek Dave; Bin Ren; Ramakrishna Bhavanthula; Qinyu Zhang; Jia Hou; Liulei Zhou

2011-01-01

336

Carbon abundances, major element chemistry, and mineralogy of hydrated interplanetary dust particles  

NASA Technical Reports Server (NTRS)

Hydrated interplanetary dust particles (IDP's) comprise a major fraction of the interplanetary dust particles collected in the stratosphere. While much is known about the mineralogy and chemistry of hydrated IDP's, little is known about the C abundance in this class of IDP's, the nature of the C-bearing phases, and how the C abundance is related to other physical properties of hydrated IDP's. Bulk compositional data (including C and O) for 11 hydrated IDP's that were subsequently examined by the transition electron microscopy (TEM) to determine their mineralogy and mineral chemistry are reported. Our analysis indicates that these hydrated IDP's are strongly enriched in C relative to the most C-rich meteorites. The average abundance of C in these hydrated IDP's is 4X CI chondrite values. The bulk compositions (including C and O) of 11 hydrated IDP's were determined by thin-window, energy-dispersive x ray (EDX) spectroscopy of the uncoated IDP's on Be substrates in the scanning electron microscopy (SEM). As a check on our C measurements, one of the IDP's (L2006H5) was embedded in glassy S, and microtome thin sections were prepared and placed onto Be substrates. Thin-film EDX analyses of multiple thin sections of L2006H5 show good agreement with the bulk value determined in the SEM. Following EDX analysis, the mineralogy and mineral chemistry of each IDP was determined by analyzing ultramicrotome thin sections in a TEM equipped with an EDX spectrometer.

Keller, L. P.; Thomas, K. L.; Mckay, D. S.

1993-01-01

337

Design of the VISITOR Tool: A Versatile ImpulSive Interplanetary Trajectory OptimizeR  

NASA Technical Reports Server (NTRS)

The design of trajectories for interplanetary missions represents one of the most complex and important problems to solve during conceptual space mission design. To facilitate conceptual mission sizing activities, it is essential to obtain sufficiently accurate trajectories in a fast and repeatable manner. To this end, the VISITOR tool was developed. This tool modularly augments a patched conic MGA-1DSM model with a mass model, launch window analysis, and the ability to simulate more realistic arrival and departure operations. This was implemented in MATLAB, exploiting the built-in optimization tools and vector analysis routines. The chosen optimization strategy uses a grid search and pattern search, an iterative variable grid method. A genetic algorithm can be selectively used to improve search space pruning, at the cost of losing the repeatability of the results and increased computation time. The tool was validated against seven flown missions: the average total mission (Delta)V offset from the nominal trajectory was 9.1%, which was reduced to 7.3% when using the genetic algorithm at the cost of an increase in computation time by a factor 5.7. It was found that VISITOR was well-suited for the conceptual design of interplanetary trajectories, while also facilitating future improvements due to its modular structure.

Corpaccioli, Luca; Linskens, Harry; Komar, David R.

2014-01-01

338

On the correlation between interplanetary nano dust particles and solar wind properties from STEREO/SWAVES  

NASA Astrophysics Data System (ADS)

Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 AU being comparable to the one of the solar wind. Among them, dusts of nanometer size-scale can be detected using radio and plasma waves instruments because they move at roughly the solar wind speed. The high velocity impact of a dust particle generates a small crater on the spacecraft: the dust particle and the crater material are vaporized. This produces a plasma cloud whose associated electrical charge induces an electric pulse measured with radio and plasma instruments. Since their first detection in the interplanetary medium (Meyer-Vernet et al. 2009), nanodusts have been routinely measured using STEREO/WAVES instrument (Zaslavsky et al. 2012) We present the nanodust properties during the 2007-2012 period on STEREO. Since the maximum size of the plasma cloud is larger for smaller local solar wind density, we expect to observe an anticorrelation between the detected voltage amplitude and the ambient solar wind density, as suggested recently by Le Chat et al. (2012). Moreover, the variations in solar wind speed and magnetic field are expected to affect the nano dust dynamics. Using STEREO/WAVES/Low Frequency Receiver (LFR) data, we study correlations of in situ solar wind properties and detection of nanodust impacts as well as some possible effects of Coronal Mass Ejections (CME) on nanodusts acceleration.

Issautier, K.; LE CHAT, G.; Meyer-Vernet, N.; Belheouane, S.; Zaslavsky, A.; Zouganelis, I.; Mann, I.; Maksimovic, M.

2012-12-01

339

Diffusive Shock Acceleration of High-energy Charged Particles at Fast Interplanetary Shocks: A Parameter Survey  

NASA Astrophysics Data System (ADS)

We present results from numerical simulations of the acceleration of solar energetic particles (SEPs) associated with strong, fast, and radially propagating interplanetary shocks. We focus on the phase of the SEP event at the time of the shock passage at 1 AU, which is when the peak intensity at energies below a few MeV is the highest. The shocks in our study start between 2 and 10 solar radii and propagate beyond 1 AU. We study the effect of various shock and particle input parameters, such as the spatial diffusion coefficient, shock speed, solar wind speed, initial location of the shock, and shock deceleration rate, on the total integrated differential intensity, I, of SEPs with kinetic energies > 10 MeV. I is the integral over energy of the differential intensity spectrum at the time of the shock passage at 1 AU. We find that relatively small changes in the parameters can lead to significant event-to-event changes in I. For example, a factor of 2 increase in the diffusion coefficient at a given energy and spatial location, can lead to a decrease in I by as much as a factor of 50. This may help explain why there are fewer large SEP events seen during the current solar maximum compared to previous maxima. It is known that the magnitude of the interplanetary magnetic field is noticeably weaker this solar cycle than it was in the previous cycle and this will naturally lead to a somewhat larger diffusion coefficient of SEPs.

Giacalone, Joe

2015-01-01

340

A scale-free analysis of magnetic holes in the solar wind  

E-print Network

Magnetic holes are isolated intervals of depleted interplanetary magnetic field (IMF) strength on timescales of several seconds to several hours. These intervals have been seen as often as several times per day in the ...

Stevens, M. L. (Michael Louis)

2006-01-01

341

3-D model of ICME in the interplanetary medium  

NASA Astrophysics Data System (ADS)

We developed a method that describes with simply geometry the coordinates of intersection between the leading edge of an ICME and the position of an arbitrary satellite. When a fast CME is ejected from the Sun to the interplanetary space in most of the cases drives a shock. As the CME moves in the corona and later in the interplanetary space more material is stacking in the front and edges of the ejecta. In a first approximation, it is possible to assume the shape of these structures, the CME and the stacked material as a cone of revolution, (the ice-cream model [Schwenn et al., (2005)]). The interface may change due to the interaction of the structure and the non-shocked material in front of the ICME but the original shape of a cone of revolution is preserved. We assume, in a three dimensional geometry, an ice-cream cone shape for the ICME and apply an analytical model for its transport in the interplanetary medium. The goal of the present method is to give the time and the intersection coordinates between the leading edge of the ICME and any satellite that may be in the path of the ICME. With this information we can modelate the travel of the ICME in the interplanetary space using STEREO data.

Borgazzi, A.; Lara, A.; Niembro, T.

2011-12-01

342

Space Travel is Utter Bilge: Early Ideas on Interplanetary Exploration  

Microsoft Academic Search

Until a few decades ago, interplanetary travel was the stuff of dreams but the dreamers often turned out to be farsighted while the predictions of some eminent scientists were far too conservative. The prescient dreamers include the Russian schoolteacher, Konstanin Tsiolkovsky who, in 1883, was the first to note that only rockets could serve the needs of space travel. In

D. K. Yeomans

2003-01-01

343

Dynamical models of coronal transients and interplanetary disturbances  

Microsoft Academic Search

The mutual benefits of dynamic MHD models for solar coronal transients and interplanetary disturbances for theoreticians and observers are explored. The effects of flare leg motion, a large depletion region beneath the loop, and an off-axis location for peak loop brightness on simulation fidelity relative to observational data are discussed. A two-dimensional MHD model of disturbances on the solar ecliptic

M. Dryer; D. F. Smart

1984-01-01

344

Towards an interplanetary internet: a proposed strategy for standardization  

NASA Technical Reports Server (NTRS)

This paper reviews the current set of standard data communications capabilities that exist to support advanced missions, discusses the architectural concepts for the future Interplanetary Internet, and suggests how a standardized set of space communications protocols that can grow to support future scenarios where human intelligence is widely distributed across the Solar System.

Hooke, A. J.

2002-01-01

345

Neutron resonance averaging  

SciTech Connect

The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

Chrien, R.E.

1986-10-01

346

Interplanetary acceleration of coronal mass ejections  

Microsoft Academic Search

Using an observed relation between speeds of CMEs near the Sun and in the solar wind, we determine an ``effective'' acceleration acting on the CMEs. We found a linear relation between this effective acceleration and the initial speed of the CMEs. The acceleration is similar to that of the slow solar wind in magnitude. The average solar wind speed naturally

N. Gopalswamy; A. Lara; R. P. Lepping; M. L. Kaiser; D. Berdichevsky; O. C. St. Cyr

2000-01-01

347

Comparison of the Characteristics of Magnetic Clouds and Magnetic Cloud-Like Structures for the Events of 1995 - 2003  

NASA Astrophysics Data System (ADS)

Using nine years of solar wind plasma and magnetic field data from the Wind mission, we investigated the characteristics of both magnetic clouds (MCs) and magnetic cloud-like structures (MCLs) during 1995 - 2003. A MCL structure is an event that is identified by an automatic scheme (Lepping, Wu, and Berdichevsky, Ann. Geophys. 23, 2687, 2005) with the same criteria as for a MC, but it is not usually identifiable as a flux rope by using the MC (Burlaga et al., J. Geophys. Res. 86, 6673, 1981) fitting model developed by Lepping, Jones, and Burlaga ( Geophys. Res. Lett. 95(11), 957, 1990). The average occurrence rate is 9.5 for MCs and 13.6 for MCLs per year for the overall period of interest, and there were 82 MCs and 122 MCLs identified during this period. The characteristics of MCs and MCL structures are as follows: (1) The average duration, ? t, of MCs is 21.1 h, which is 40% longer than that for MCLs (? t=15 h); (2) the average B_{z_{min}} (minimum B z found in MC/MCL measured in geocentric solar ecliptic coordinates) is -10.2 nT for MCs and -6 nT for MCLs; (3) the average Dstmin (minimum Dst caused by MCs/MCLs) is -82 nT for MCs and -37 nT for MCLs; (4) the average solar wind velocity is 453 km s-1 for MCs and 413 km s-1 for MCLs; (5) the average thermal speed is 24.6 km s-1 for MCs and 27.7 km s-1 for MCLs; (6) the average magnetic field intensity is 12.7 nT for MCs and 9.8 nT for MCLs; (7) the average solar wind density is 9.4 cm-3 for MCs and 6.3 cm-3 for MCLs; and (8) a MC is one of the most important interplanetary structures capable of causing severe geomagnetic storms. The longer duration, more intense magnetic field and higher solar wind speed of MCs, compared to those properties of the MCLs, are very likely the major reasons for MCs generally causing more severe geomagnetic storms than MCLs. But the fact that a MC is an important interplanetary structure with respect to geomagnetic storms is not new ( e.g., Zhang and Burlaga, J. Geophys. Res. 93, 2511, 1988; Bothmer, ESA SP-535, 419, 2003).

Wu, Chin-Chun; Lepping, R. P.

2007-05-01

348

Solar cycle variations of heliospheric magnetic flux  

NASA Astrophysics Data System (ADS)

We extend previous studies of BR, the radial component of the heliospheric magnetic field and a measure of heliospheric magnetic flux, to include the maximum in cycle 23 so that most of 4 cycles are covered. Solar rotation averages reveal that BR systematically increases from a minimum value at sunspot minimum to a maximum value during the declining phase. This increase is interrupted by a temporary decrease associated with the disappearance and reversal of the Sun's polar cap fields. We examine variations in BR and field strength, B, and find a close correspondence consistent with the Parker model when allowance is made for the ever-present fluctuations in the heliospheric magnetic field. The solar cycle variation in BR and B is consistent with the widely accepted model of the solar field in which bipolar sunspot fields emerging at solar maximum are responsible for the erosion and reversal of the polar cap fields. Although the solar cycle change in heliospheric magnetic flux is less than a factor of 2, it is very large compared with the average flux transported into the heliosphere by an interplanetary coronal mass ejection (ICME). If the increases in B and BR at solar maximum are attributed to closed ICME fields, several hundred ICMEs must connect to the Sun for about two solar rotations before disconnecting, consistent with a recent model that attributes the increase in heliospheric flux at solar maximum to ICMEs. Future studies must distinguish between the open and closed topologies in order to evaluate their relative contributions.

Zhou, Xiaoyan; Smith, Edward J.

2009-03-01

349

Seed population for about 1 MeV per nucleon heavy ions accelerated by interplanetary shocks  

NASA Technical Reports Server (NTRS)

Data obtained between 1977 and 1982 by the ISEE 1 and ISEE 3 satellites on the composition of heavy ions of about 1 MeV per nucleon, accelerated in interplanetary shock events which followed solar flare events, are examined. It was found that the average relative abundances for C, O, and Fe in the shock events were very close to those found for energetic ions in the solar flares, suggesting that, at these energies, the shock accelerated particles have the solar energetic particles as their seed population. This hypothesis is supported by the fact that the Fe/O ratio in the solar particle events is very strongly correlated with the Fe/O ratio in associated diffusive shock events.

Tan, L. C.; Mason, G. M.; Klecker, B.; Hovestadt, D.

1989-01-01

350

Upstream and downstream wave packets associated with low-Mach number interplanetary shocks  

NASA Astrophysics Data System (ADS)

Wave packets are frequently observed upstream and/or downstream of shocks in a magnetized plasma. We present a comparison of Wind and Spektr-R observations of 27 interplanetary low-Mach number (<5.5) shocks that reveals that (1) the wavelengths of both upstream and downstream waves conserve over the spacecraft separation, (2) in the frequency range of 0.5-5 Hz, their wavelengths are directly proportional to the shock ramp thickness that is controlled by the ion thermal gyroradius, and (3) the phase shift between density and temperature variations within downstream wave packets is about 90°. These results emphasize a role of kinetic processes in the formation of low-Mach number shocks.

Goncharov, O.; Å afránková, J.; N?me?ek, Z.; P?ech, L.; PitÅa, A.; Zastenker, G. N.

2014-11-01

351

Ion scales of quasi-perpendicular low-Mach-number interplanetary shocks  

NASA Astrophysics Data System (ADS)

A formation of low-Mach-number quasi-perpendicular shocks is expected to be well understood. From theoretical considerations as well as from observations, it follows that the shock ramp thickness would scale with the ion inertial length. We present analysis of 12 subcritical or marginally critical interplanetary shocks that reveals that (1) the ion transition scale determined from direct measurements of plasma moments (speed, temperature, and density) are of the same order as the ramp thickness determined from the magnetic field and (2) the ion transition scale is directly proportional to the ion thermal gyroradius, Rth; it was found to be ?3.2 Rth in a broad range of solar wind and shock parameters. These results stress a role of the ion kinetics in the shock formation.

N?Me?Ek, Z.; Å AfráNková, J.; Goncharov, O.; P?Ech, L.; Zastenker, G. N.

2013-08-01

352

Use of magnetic sails for advanced exploration missions  

NASA Technical Reports Server (NTRS)

The magnetic sail, or magsail, is a field effect device which interacts with the ambient solar wind or interstellar medium over a considerable volume of space to generate drag and lift forces. Two theories describing the method of thrust generation are analyzed and data results are presented. The techniques for maintaining superconductor temperatures in interplanetary space are analyzed and low risk options presented. Comparisons are presented showing mission performance differences between currently proposed spacecraft using chemical and electric propulsion systems, and a Magsail propelled spacecraft capable of generating an average thrust of 250 Newtons at a radius of one A.U. The magsail also provides unique capabilities for interstellar missions, in that at relativistic speeds the magnetic field would ionize and deflect the interstellar medium producing a large drag force. This would make it an ideal brake for decelerating a spacecraft from relativistic speeds and then maneuvering within the target star system.

Andrews, Dana G.; Zubrin, Robert M.

1990-01-01

353

The Interplanetary Internet: A Communications Infrastructure for Mars Exploration  

NASA Astrophysics Data System (ADS)

A successful program of Mars Exploration will depend heavily on a robust and dependable space communications infrastructure that is well integrated with the terrestrial Internet. In the same way that the underpinnings of the Internet are the standardized "TCP/IP" suite of protocols, an "Interplanetary Internet" will need a similar set of capabilities that can support reliable communications across vast distances and highly stressed communications environments. For the past twenty years, the Consultative Committee for Space Data Systems (CCSDS) has been developing standardized long- haul space link communications techniques that are now in use by over two hundred missions within the international space community. New CCSDS developments, shortly to be infused into Mars missions, include a proximity link standard and a store-and- forward file transfer protocol. As part of its `Next Generation Internet' initiative, the U.S. Defense Advanced Projects Agency (DARPA) recently supported an architectural study of a future "InterPlaNetary Internet" (IPN). The IPN architecture assumes that in short-delay environments - such as on and around Mars - standard Internet technologies will be adapted to the locally harsh environment and deployed within surface vehicles and orbiting relays. A long-haul interplanetary backbone network that includes Deep Space Network (DSN) gateways into the terrestrial Internet will interconnect these distributed internets that are scattered across the Solar System. Just as TCP/IP unites the Earth's "network of networks" to become the Internet, a new suite of protocols known as "Bundling" will enable the IPN to become a "network of internets" to support true interplanetary dialog. An InterPlaNetary Internet Research Group has been established within the Internet community to coordinate this research and NASA has begun to support the further development of the IPN architecture and the Bundling protocols. A strategy is being developed whereby the current set of standard CCSDS data communications protocols can be incrementally evolved so that true InterPlaNetary Internet operations are feasible by the end of the decade. The strategy - which is already in progress via the deployment of Mars relay links - needs individual missions to each contribute increments of capability so that a standard communications infrastructure can rapidly accrete. This paper will describe the IPN architectural concepts, discuss the current set of standard data communications capabilities that exist to support Mars exploration and review the proposed new developments. We will also postulate that the concept is scalable and can grow to support future scenarios where human intelligence is widely distributed across the Solar System and day-to-day communications dialog among planets is routine. 1 2 3 4 5

Burleigh, S.; Cerf, V.; Durst, R.; Fall, K.; Hooke, A.; Scott, K.; Weiss, H.

2002-01-01

354

Temperature: Decadal Averages Map  

NSDL National Science Digital Library

This interactive map allows students to experiment with decadal average temperature projections. Overall temperatures are expected to rise throughout the century and this tool demonstrates those projected measurements.

Commission, California E.

355

Solar Mass Ejection Imager (SMEI) 3-D reconstruction of density enhancements behind interplanetary shocks: In-situ comparison near Earth and at STEREO  

Microsoft Academic Search

SMEI and IPS remotely observe increased brightness and velocity enhancements behind interplanetary shocks that are also seen in situ. We use the UCSD time-dependent 3-D reconstruction technique to map these enhancements, and compare them with measurements at the SOHO, Wind, ACE, and STEREO spacecraft. The analyses of these shocks from hour-averaged in-situ data show that the enhanced density column associated

B. V. Jackson; M. S. Hamilton; P. P. Hick; A. Buffington; M. M. Bisi; J. M. Clover; M. Tokumaru; K. Fujiki

2011-01-01

356

Martian magnetic morphology: Contributions from the solar wind and crust  

E-print Network

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

California at Berkeley, University of

357

Lesson Summary Students will learn about the magnetic fields of  

E-print Network

Knowledge & Skills Understanding of: · Magnetic field lines · Magnetic field strength decreases. Introducing the Interplanetary Magnetic Field (IMF) and Solar Wind 1. First have the students answerLesson Summary Students will learn about the magnetic fields of the Sun and Earth. This activity

Mojzsis, Stephen J.

358

The solar origins of two high-latitude interplanetary disturbances  

SciTech Connect

Two extremely similar interplanetary forward/reverse shock events, with bidirectional electron streaming were detected by Ulysses in 1994. Ground-based and Yohkoh/SXT observations show two strikingly different solar events that could be associated with them: an LDE flare on 20 Feb. 1994, and a extremely large-scale eruptive event on 14 April 1994. Both events resulted in geomagnetic storms and presumably were associated with coronal mass ejections. The sharply contrasting nature of these solar events argues against an energetic causal relationship between them and the bidirectional streaming events observed by Ulysses during its S polar passage. The authors suggest instead that for each pair of events. a common solar trigger may have caused independent instabilities leading to the solar and interplanetary phenomena.

Hudson, H.S.; Acton, L.W.; Alexander, D.; Harvey, K.L.; Kurokawa, H.; Kahler, S.; Lemen, J.R. [Montana State Univ., Bozeman, MT (United States); [Solar Physics Research Corp., Tucson, AZ (United States); [Kyoto Univ. (Japan); [Phillips Lab., Hanscom AFB, MA (United States); [Lockheed Aircraft Corp., Palo Alto, CA (United States)

1995-06-01

359

Fractal Signatures in Analogs of Interplanetary Dust Particles  

E-print Network

Interplanetary dust particles (IDPs) are an important constituent of the earth's stratosphere, interstellar and interplanetary medium, cometary comae and tails, etc. Their physical and optical characteristics are significantly influenced by the morphology of silicate aggregates which form the core in IDPs. In this paper we reinterpret scattering data from laboratory analogs of cosmic silicate aggregates created by Volten et al. \\cite{volten2007}, to extract their morphological features. By evaluating the structure factor, we find that the aggregates are mass fractals with a mass fractal dimension $d_{m} \\simeq 1.75$. The same fractal dimension also characterizes clusters obtained from {\\it diffusion limited aggregation} (DLA). This suggests that the analogs are formed by an irreversible aggregation of stochastically-transported silicate particles

Katyal, Nisha; Puri, Sanjay

2014-01-01

360

Study of Travelling Interplanetary Phenomena (STIP) workshop travel  

NASA Technical Reports Server (NTRS)

Thirty six abstracts are provided from the SCOSTEP/STIP Symposium on Retrospective Analyses and Future Coordinated Intervals held in Switzerland on June 10 to 12, 1985. Six American scientists participated in the symposium and their abstracts are also included. The titles of their papers are: (1) An analysis of near surface and coronal activity during STIP interval 12, by T. E. Gergely; (2) Helios images of STIP intervals 6, B. V. Jackson; (3) Results from the analysis of solar and interplanetary observations during STIP interval 7, S. R. Kane; (4) STIP interval 19, E. Cliver; (5) Hydrodynamic buoyancy force in the solar atmosphere, T. Yeh; and (6) A combined MHD modes for the energy and momentum transport from solar surface to interplanetary space, S. T. Wu.

Wu, S. T.

1986-01-01

361

Development of coronal mass ejections and association with interplanetary events  

NASA Technical Reports Server (NTRS)

Results are presented on the development of two coronal mass ejections (CMEs) obtained by comparing the observations of the large angle spectroscopic coronagraph (LASCO) and the extreme ultraviolet imaging telescope (EIT) instrument onboard the SOHO with those of the Nancay radioheliograph. The radioheliograph provides images at five levels in the corona. An excellent spatial association is found between the position and extent of the type 4 radio sources and the CMEs seen by LASCO. One result is the existence for these two events of discrete successive phases in their development. For these events, Ulysses and SOHO missions measured interplanetary particles of coronal origin. The coronal acceleration site was attempted to be identified, as well as the path of these particles from the corona to the interplanetary medium.

Pick, M.; Maia, D.; Howard, R.; Thompson, B.; Lanzerotti, L. J. L.; Bothmer, V.; Lamy, P.

1997-01-01

362

Energetic solar flare particles and interplanetary shock waves  

NASA Technical Reports Server (NTRS)

Estimates from hard X-ray measurements show that for many flares the bulk of the flare energy is released in the form of approximately 10-100-keV energy electrons. The interaction of these electrons with the solar atmosphere can produce the optical, UV, EUV, and radio emissions observed during the flare impulsive phase. In addition, explosive heating and evaporation of the chromosphere by these electrons can produce the roughly 10 million K soft X-ray plasma. For the large solar flares which produce interplanetary shock waves, the accelerated approximately 10-100-keV electron population may produce the heating and mass motion required for mass ejection and the formation of the shock wave. The shock wave can in turn accelerate ions and electrons to higher energy as it travels through the corona and interplanetary medium.

Lin, R. P.

1977-01-01

363

Infrared spectroscopy of interplanetary dust in the laboratory  

NASA Technical Reports Server (NTRS)

A mount containing three crushed chondritic interplanetary dust particles (IDPs) collected in the earth's stratosphere and subjected to infrared spectroscopic measurements shows features near 1000 and 500/cm, suggesting crystalline pyroxene rather than crystalline olivine, amorphous olivine, or meteoritic clay minerals. Chondritic IDP structural diversity and atmospheric heating effects must be considered when comparing this spectrum with interplanetary and cometary dust astrophysical spectra. TEM and infrared observations of one member of the rare subset of IDPs resembling hydrated carbonaceous chondrite matrix material shows a close infrared spectrum resemblance between 4000 and 400/cm to the C2 meteorite Murchison. TEM observations suggest that this class of particles may be used as an atmospheric entry heating-process thermometer.

Fraundorf, P.; Patel, R. I.; Freeman, J. J.

1981-01-01

364

Thirty Years of Interplanetary Background Data: A Global View  

NASA Astrophysics Data System (ADS)

This chapter compares results of models of the interplanetary background, such as the one presented in Chap.1, to different datasets obtained in the outer heliosphere (Voyager-UVS, Alice New-Horizons) and in the inner heliosphere (SWAN-SOHO, STIS-HST). The aim of this work is to combine these datasets and the models and to derive calibration factors that give a coherent picture of the various instruments and the interplanetary background. These datasets do not overlap and the models are used to bridge the gaps in distance or in time. In the case of Voyager 1 and 2 UVS instruments, the calibration factors derived here are significantly different from the values published by Hall (Ultraviolet resonance radiation and the structure of the heliosphere. Dissertation, University of Arizona, 1992).

Quémerais, Eric; Sandel, Bill R.; Izmodenov, Vladislav V.; Gladstone, G. Randall

365

Asynchronous Laser Transponders for Precise Interplanetary Ranging and Time Transfer  

NASA Technical Reports Server (NTRS)

The feasibility of a two-way asynchronous (i.e. independently firing) interplanetary laser transponder pair, capable of decimeter ranging and subnanosecond time transfer from Earth to a spacecraft anywhere within the inner Solar System, is discussed. In the Introduction, we briefly discuss the current state-of-the-art in Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) which use single-ended range measurements to a passive optical reflector, and the limitations of this approach in ranging beyond the Moon to the planets. In Section 2 of this paper, we describe two types of transponders (echo and asynchronous), introduce the transponder link equation and the concept of "balanced" transponders, describe how range and time can be transferred between terminals, and preview the potential advantages of photon counting asynchronous transponders for interplanetary applications. In Section 3, we discuss and provide mathematical models for the various sources of noise in an interplanetary transponder link including planetary albedo, solar or lunar illumination of the local atmosphere, and laser backscatter off the local atmosphere. In Section 4, we introduce the key engineering elements of an interplanetary laser transponder and develop an operational scenario for the acquisition and tracking of the opposite terminal. In Section 5, we use the theoretical models of th previous sections to perform an Earth-Mars link analysis over a full synodic period of 780 days under the simplifying assumption of coaxial, coplanar, circular orbits. We demonstrate that, using slightly modified versions of existing space and ground based laser systems, an Earth-Mars transponder link is not only feasible but quite robust. We also demonstrate through analysis the advantages and feasibility of compact, low output power (<300 mW photon-counting transponders using NASA's developmental SLR2000 satellite laser ranging system as the Earth terminal. Section 6 provides a summary of the results and some concluding remarks regarding future applications.

Degnan, John J.; Smith, David E. (Technical Monitor)

2001-01-01

366

Interplanetary MeV electrons of Jovian origin  

Microsoft Academic Search

In this paper we report observations of low-energy (0.2- to 8-MeV) electron increases observed in interplanetary space on Pioneer 10 as it approached within 1 AU of Jupiter. These discrete bursts or increases were typically several hundred times the normal quiet time electron flux and became much more frequent as one approached Jupiter, the result being the quasi-continuous presence of

B. J. Teegarden; F. B. McDonald; J. H. Trainor; W. R. Webber; E. C. Roelof

1974-01-01

367

MHD solution of interplanetary disturbances generated by simulated velocity perturbations  

Microsoft Academic Search

An MHD time-dependent numerical simulation, restricted to the solar equatorial plane, is used to demonstrate the interplanetary disturbances caused by several simplified coronal holes. Each 'hole' is assumed to have a configuration such that the higher solar wind velocity produced within their longitudinal extent is Gaussian over a 7-day period at the inner boundary (0.3 AU) of the numerical simulation.

Murray Dryer; R. S. Steinolfson

1976-01-01

368

Partially ejected flux ropes: Implications for interplanetary coronal mass ejections  

Microsoft Academic Search

Connecting interplanetary coronal mass ejections (ICMEs) to their solar pre-eruption source requires a clear understanding of how that source may have evolved during eruption. Gibson and Fan (2006a) have presented a three-dimensional numerical magnetohydrodynamic simulation of a CME, which showed how, in the course of eruption, a coronal flux rope may writhe and reconnect both internally and with surrounding fields

S. E. Gibson; Y. Fan

2008-01-01

369

GEO debris and interplanetary dust: fluxes and charging behavior  

E-print Network

In September 1996, a dust/debris detector: GORID was launched into the geostationary (GEO) region as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris to interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. While the physical characteristics of the GORID impacts alone are insufficient for a reliable distinction between debris and interplanetary dust, the temporal behavior of the impacts are strong enough indicators to separate the populations based on clustering. Non-cluster events are predominantly interplanetary, while cluster events are debris. The GORID mean flux distributions (at mass thresholds which are impact speed dependent) for IDPs, corrected for dead time, are 1.35x10^{-4} m^{-2} s^{-1} using a mean detection rate: 0.54 d^{-1}, and for space debris are 6.1x10^{-4} m^{-2} s^{-1} using a mean detection rate: 2.5 d^{-1}. Beta-meteoroids were not detected. Clusters could be a closely-packed debris cloud or a particle breaking up due to electrostatic fragmentation after high charging.

Amara L. Graps; Simon F. Green; Neil McBride; J. A. M. McDonnell; Kalle Bunte; Hakan Svedhem; Gerhard Drolshagen

2006-09-13

370

Interplanetary Electric Propulsion Uranus Mission Trades Supporting the Decadal Survey  

NASA Technical Reports Server (NTRS)

The Decadal Survey Committee was tasked to develop a comprehensive science and mission strategy for planetary science that updates and extends the National Academies Space Studies Board s current solar system exploration decadal survey. A Uranus orbiter mission has been evaluated as a part of this 2013-2022 Planetary Science Decadal Survey. A comprehensive Uranus orbiter mission design was completed, including a broad search of interplanetary electric propulsion transfer options. The scope of interplanetary trades was limited to electric propulsion concepts, both solar and radioisotope powered. Solar electric propulsion offers significant payloads to Uranus. Inserted mass into the initial science orbit due is highly sensitive to transfer time due to arrival velocities. The recommended baseline trajectory is a 13 year transfer with an Atlas 551, a 1+1 NEXT stage with 15 kW of power using an EEJU trajectory and a 1,000km EGA flyby altitude constraint. This baseline delivers over 2,000kg into the initial science orbit. Interplanetary trajectory trades and sensitivity analyses are presented herein.

Dankanich, John W.; McAdams, James

2011-01-01

371

Features of the Martian Magnetic Field Structure  

Microsoft Academic Search

Based on the single-fluid MHD model of Mars space simulation, this paper has studied the magnetic field structure in the near-Mars space and investigated the influence of Martian crustal magnetic anomalies on the magnetic field structure. In the process of the solar wind interaction with Mars, the bow shock and magnetic pile-up region are produced. The interplanetary magnetic lines are

Yi-Teng Zhang; Lei Li

2009-01-01

372

Interplanetary missions with the GDM propulsion system  

SciTech Connect

The Gasdynamic Mirror (GDM) fusion propulsion system utilizes a magnetic mirror machine in which a hot dense plasma is confined long enough to produce fusion energy while allowing a fraction of its charged particle population to escape from one end to generate thrust. The particles escaping through the opposite end have their energy converted to electric power which can be used to sustain the system in a steady state operation. With the aid of a power flow diagram the minimum demands on energy production can be established and the propulsive capability of the system can be determined by solving an appropriate set of governing equations. We apply these results to several missions within the solar system and compute the trip time by invoking a continuous burn, acceleration/deceleration type of trajectory with constant thrust and specific impulse. Ignoring gravitational effects of the planets or the sun, and neglecting the change in the Earth's position during the flight we compute the round trip time for missions from Earth to Mars, Jupiter, and Pluto using linear distances and certain payload fractions. We find that a round trip to Mars with the GDM rocket takes about 170 days while those to Jupiter and Pluto take 494 and 1566 days respectively.

Kammash, T.; Emrich, W. Jr. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Marshall Space Flight Center, Huntsville, Alabama 35812 (United States)

1998-01-15

373

Global dayside ionospheric uplift and enhancement associated with interplanetary electric fields  

Microsoft Academic Search

The interplanetary shock\\/electric field event of 5–6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP and SAC-C satellites and altimeter data from the TOPEX\\/Poseidon satellite. Data from ?100 ground-based GPS receivers as well as Brazilian Digisonde and Pacific sector magnetometer data are also used. The dawn-to-dusk interplanetary

Bruce Tsurutani; Anthony Mannucci; Byron Iijima; Mangalathayil Ali Abdu; Jose Humberto A. Sobral; Walter Gonzalez; Fernando Guarnieri; Toshitaka Tsuda; Akinori Saito; Kiyohumi Yumoto; Bela Fejer; Timothy J. Fuller-Rowell; Janet Kozyra; John C. Foster; Anthea Coster; Vytenis M. Vasyliunas

2004-01-01

374

Global dayside ionospheric uplift and enhancement associated with interplanetary electric fields  

Microsoft Academic Search

The interplanetary shock\\/electric field event of 5-6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP and SAC-C satellites and altimeter data from the TOPEX\\/Poseidon satellite. Data from ~100 ground-based GPS receivers as well as Brazilian Digisonde and Pacific sector magnetometer data are also used. The dawn-to-dusk interplanetary

Bruce Tsurutani; Anthony Mannucci; Byron Iijima; Mangalathayil Ali Abdu; Jose Humberto A. Sobral; Walter Gonzalez; Fernando Guarnieri; Toshitaka Tsuda; Akinori Saito; Bela Fejer; Timothy J. Fuller-Rowell; Janet Kozyra; John C. Foster; Anthea Coster; Vytenis M. Vasyliunas

2004-01-01

375

Coronal Transient Events During Two Solar Minima: Their Solar Source Regions and Interplanetary Counterparts  

NASA Astrophysics Data System (ADS)

In the frame of two coordinated observational and research efforts, two full solar rotations were investigated in the times of two distinct solar minima. These two campaigns were dubbed Whole Sun Month (WSM; 10 August - 8 September 1996) and Whole Heliosphere Interval (WHI; 20 March - 16 April 2008). The nearly uninterrupted gathering of solar coronal data since the beginning of the Solar and Heliospheric Observatory (SOHO) era offers the exceptional possibility of comparing two solar minima for the first time, with regard to the coronal transient aspect. This study characterizes the variety of outward-traveling transients observed in the solar corona during both time intervals, from very narrow jet-like events to coronal mass ejections (CMEs). Their solar source regions and ensuing interplanetary structures were identified and characterized as well, toward a global-scale description of their role in determining the heliosphere’s conditions. Multi-wavelength images provided by the space missions SOHO, Yohkoh (only WSM), and Solar-Terrestrial Relations Observatory (STEREO; only WHI) and ground-based observatories were analyzed for coronal ejecta and their solar sources, while data registered by the Advanced Composition Explorer (ACE) spacecraft were inspected for interplanetary CMEs and magnetic clouds. Notable differences arise from the analysis of the detailed survey of events: more (fewer) ejecta during WHI (WSM), 12% (40%) were produced by active regions during WHI (WSM), and nearly no (high) deflection from the radial direction was observed during WHI (WSM). Instrumental aspects such as dissimilar resolution, cadence, and fields of view are considered in order to discern instrumentally driven disparities from inherent differences between solar minima.

Cremades, H.; Mandrini, C. H.; Dasso, S.

2011-12-01

376

INFLUENCE OF THE AMBIENT SOLAR WIND FLOW ON THE PROPAGATION BEHAVIOR OF INTERPLANETARY CORONAL MASS EJECTIONS  

SciTech Connect

We study three coronal mass ejection (CME)/interplanetary coronal mass ejection (ICME) events (2008 June 1-6, 2009 February 13-18, and 2010 April 3-5) tracked from Sun to 1 AU in remote-sensing observations of Solar Terrestrial Relations Observatory Heliospheric Imagers and in situ plasma and magnetic field measurements. We focus on the ICME propagation in interplanetary (IP) space that is governed by two forces: the propelling Lorentz force and the drag force. We address the question: which heliospheric distance range does the drag become dominant and the CME adjust to the solar wind flow. To this end, we analyze speed differences between ICMEs and the ambient solar wind flow as a function of distance. The evolution of the ambient solar wind flow is derived from ENLIL three-dimensional MHD model runs using different solar wind models, namely, Wang-Sheeley-Arge and MHD-Around-A-Sphere. Comparing the measured CME kinematics with the solar wind models, we find that the CME speed becomes adjusted to the solar wind speed at very different heliospheric distances in the three events under study: from below 30 R{sub Sun }, to beyond 1 AU, depending on the CME and ambient solar wind characteristics. ENLIL can be used to derive important information about the overall structure of the background solar wind, providing more reliable results during times of low solar activity than during times of high solar activity. The results from this study enable us to obtain greater insight into the forces acting on CMEs over the IP space distance range, which is an important prerequisite for predicting their 1 AU transit times.

Temmer, Manuela; Rollett, Tanja; Moestl, Christian; Veronig, Astrid M. [Kanzelhoehe Observatory-IGAM, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, Bojan [Hvar Observatory, Faculty of Geodesy, University of Zagreb, Kaciceva 26, HR-10000 Zagreb (Croatia); Odstrcil, Dusan [Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO (United States)

2011-12-20

377

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

NASA Astrophysics Data System (ADS)

We do a statistical survey of solar wind dynamic pressure (Pd) pulses and geosynchronous magnetic fields observed between 1998 and 2005. In geomagnetic quiet times with Dst>-50nT, we find 111 solar wind dynamic pressure pulses which produce geosynchronous magnetic field responses. These responses are often observed by two or three GOES spacecraft at different local times in geosynchronous orbit. The magnitudes of the geosynchronous magnetic field changes (dBz) have a peak near the noon meridian, similar to the results obtained in the study of the response of the geosynchronous field to the large and sharp solar wind dynamic pressure variations. However, the relative change of the geosynchronous magnetic field dBz/AV-Bz (where AV-Bz is the average of the geosynchronous magnetic field Bz observed during the response to the pressure pulse) depends weakly on the local time, thus the change of Bz(dBz) is proportional to the average field (AV-Bz). As the magnitude of the relative change of solar wind dynamic pressure (dPd/Pd) increases, the rate of geosynchronous magnetic field variation increases correspondingly. These results imply that the magnitude of the geosynchronous magnetic field response could be determined by AV-Bz. In addition, the interplanetary field orientation does not affect the response significantly. Using an MHD code which models the global behavior of the solar wind-magnetosphere-ionosphere system, we reproduce the main characteristics of the observations.

Wang, C.; Liu, J.; Huang, Z.; Richardson, J. D.

2007-12-01

378

On the Relationship Between Transit Velocity of Interplanetary Shocks and Solar Active Processes  

NASA Technical Reports Server (NTRS)

Recently, it was reported that preferential relationships exist between the transit velocity V(sub T) of earthward-directed interplanetary shocks and solar active processes, in particular, eruptive filaments outside active regions (the size of the erupting filament L(sub f)) and solar flares (the value of the X-ray characteristic J). Unfortunately, statistical testing of the proposed associations was not accomplished, nor was the 'geo-effectiveness' of the events adequately described. Reported here are the results of a re-examination of the 21 eruptive filaments (SSC-EF events) and 26 X-ray flares (SSC-F events) that have been associated with storm sudden commencements (SSCs) at Earth. Simple statistical testing refutes the claim that a preferential relationship exists between V(sub T) and L(sub F), while it supports the claim that one exists between V(sub T) and J. More importantly, the inferred relationship between V(sub T) and J is found to be more complicated than previously thought. In particular, it now appears that SSC-F events may be separable into two groups, based on the value of J: a low-J group (J less than 56), in which V(sub T) varies directly with J, and a high-J group (J greater than 56), in which V(sub T) varies inversely with J. As a whole, high-J events are associated with shocks of higher average transit velocity than those of low-J events, and SSC-F events with shocks of higher average transit velocity than those of SSC-EF events. Further, high-J events tend to be of greater X-ray class ( greater than M3), longer duration (greater then 80 min), and are more likely to be associated with type II/IV radio emission (9 of 12) than low-J events. They also tend to occur in magnetically complex (gamma/delta configuration) active regions (10 of 12) that are large in area extent (area greater than 445 millionths of a solar hemisphere) on the day of flaring (9 of 12). Of the 9 solar proton events that affected the Earth's environment that were found to be associated with SSC-F events, six were high-J events. Concerning 'geo-effectiveness', there appears to be no preferential relationship between the value of the J-parameter and the most negative value of the Dst geomagnetic index Dst(min) following the SSC, which is found to usually occur at 6-14 h after SSC onset (18 of 26) and which ranged in value from -1 to -249 (having a median value of about -75). Of the 26 SSC-F events, only 14 can be associated with a Dst(min) less than or equal to -75, and of these only 7 were high-J events. Of the 14 storm-related events (i.e. Dst(min) less than or equal to -75), three have previously been identified as being either 'magnetic clouds' or 'bidirectional flows', both manifestations of earthward-directed coronal mass ejections (CMEs). Superposed epoch analyses of selected solar wind parameters and Dst during the interval of storm-related SSC-F events demonstrate that geoeffective SSC-F events tend to be associated with solar wind flows that are faster, greater in magnetic field strength, and have a rotating field which has a strong southward component shortly after SSC onset, in comparison to SSC-F events that do not have Dst(min) less than or equal to 75. Therefore, it is inferred that geoeffective SSC-F events are probably fast earthward-directed CMEs. Although no single parameter is found that can serve as a predictor of high-skill level for determining the geoeffectiveness of an SSC-F event prior to its occurrence at Earth, one finds that knowledge of the flare's hemispheric location and appearance or lack of appearance of a two-ribbon structure is sufficient to correctly predict the geoeffectiveness of 20 out of 25 of the SSC-F events (80%). Surprisingly, the association or lack of association of metric type II/IV radio emission as a characteristic for determining the geoeffectiveness of the SSC-F events proved unfruitful, as did, to a lesser extent, the duration of the X-ray emission.

Wilson, Robert M.

1996-01-01

379

Average Rate of Change  

NSDL National Science Digital Library

This demo provides students with a concrete understanding of the average rate of change for physical situations and for functions described in tabular or graphic form. Animations in gif and Quicktime format are available, as well as Excel programs for classroom or student use.

Roberts, Lila F.

2005-04-21

380

Your Average Nigga  

ERIC Educational Resources Information Center

"Your Average Nigga" contends that just as exaggerating the differences between black and white language leaves some black speakers, especially those from the ghetto, at an impasse, so exaggerating and reifying the differences between the races leaves blacks in the impossible position of either having to try to be white or forever struggling to…

Young, Vershawn Ashanti

2004-01-01

381

Monitoring the solar-terrestrial environment using interplanetary scintillation  

NASA Astrophysics Data System (ADS)

Before being detected on Earth, radio waves from a celestial source pass through the interplanetary medium, where they undergo diffraction by plasma density variations in the solar wind, making them appear to scintillate. The amount of scintillation observed can be used to infer the electron density along the line-of-sight to the source. Therefore, when observing many sources across the sky, the solar wind can be mapped out daily. Observations taken over a 5 year period (1990-94) with the Cambridge IPS array are now being analysed at Glasgow. Man-made interference, from sources such as domestic appliances and car engines, is a significant problem in much of these data. Obviously, to get the most out of the data, this noise must be dealt with properly. Another problem is caused by scintillation in the ionosphere. We must be able to distinguish between scintillation caused by the ionosphere, and that caused by the interplanetary medium. Using a model for the expected scintillation profile and timescale for each radio source, it is possible to cut out noise, and to identify periods of ionospheric scintillation in the data. The fitting procedure returns an estimate of both the scintillating power of the source, and the scintillation frequency, which can in turn be used to measure both the density and speed of the solar wind over the whole sky. From this, it's possible to track transient events in the interplanetary medium, such as Coronal Mass Ejections. This whole-sky picture has several advantages over a localised measurement given by an in-situ spacecraft.

Daly, N.

382

INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS  

SciTech Connect

Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the Interplanetary Network (IPN) consisted of up to 11 spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, {approx}18 yr{sup -1}, exceeds that of many individual experiments.

Pal'shin, V. D.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Oleynik, P. P.; Ulanov, M. V. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Cline, T.; Trombka, J.; McClanahan, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Boynton, W.; Fellows, C.; Harshman, K., E-mail: val@mail.ioffe.ru [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); and others

2013-08-15

383

Gamma ray burst source locations with the new interplanetary network  

NASA Technical Reports Server (NTRS)

The celestial source fields of gamma ray bursts can now be determined with precision considerably greater than that provided by earlier interplanetary networks. A new burst timing array consists of the Ulysses mission and the Pioneer-Venus Orbiter at great distances and the Compton Observatory, Granat, and other burst-observing spacecraft near the Earth. With Ulysses providing a baseline approaching five astronomical units in its progress towards Jupiter, and given the timing resolution of the Compton Burst and Transient Source Experiment, source fields with dimensions as small as several arc seconds by less than one arc minute will be determined for many of the events to be studied within this network.

Cline, T. L.; Fishman, Gerald; Hurley, Kevin; Laros, John; Lund, Neils; Sommer, Michael

1992-01-01

384

Analysis of Interplanetary Dust Experiment Detectors and Other Witness Plates  

NASA Technical Reports Server (NTRS)

The development of analytical procedures for identifying the chemical composition of residue from impacts that occurred on the Interplanetary Dust Experiment (IDE) detectors during the flight of Long Duration Exposure Facility (LDEF) and the carrying out of actual analysis on IDE detectors and other witness plates are discussed. Two papers on the following topics are presented: (1) experimental analysis of hypervelocity microparticle impact sites on IDE sensor surfaces; and (2) contaminant interfaces with secondary Ion Mass Spectrometer (SIMS) analysis of microparticle impactor residues on LDEF surfaces.

Griffis, D. P.; Wortman, J. J.

1992-01-01

385

A decametric wavelength radio telescope for interplanetary scintillation observations  

NASA Technical Reports Server (NTRS)

A phased array, electrically steerable radio telescope (with a total collecting area of 18 acres), constructed for the purpose of remotely sensing electron density irregularity structure in the solar wind, is presented. The radio telescope is able to locate, map, and track large scale features of the solar wind, such as streams and blast waves, by monitoring a large grid of natural radio sources subject to rapid intensity fluctuation (interplanetary scintillation) caused by the irregularity structure. Observations verify the performance of the array, the receiver, and the scintillation signal processing circuitry of the telescope.

Cronyn, W. M.; Shawhan, S. D.

1975-01-01

386

Hydrated interplanetary dust particle linked with carbonaceous chondrites?  

NASA Technical Reports Server (NTRS)

The results of transmission electron microscope observations of a hydrated interplanetary dust particle (IDP) containing Fe-, Mg-rich smectite or mica as a major phase are reported. The sheet silicate appears to have formed by alteration of anhydrous silicates. Fassaite, a Ca, Al clinopyroxene, also occurs in this particle, and one of the crystals exhibits solar-flare tracks, clearly indicating that it is extraterrestrial. Fassaite is a major constituent of the Ca-, Al-rich refractory inclusions found in the carbonaceous chondrites, so its presence in this particle suggests that there may be a link between hydrated IDPs and carbonaceous chondrites in the early history of the solar system.

Tomeoka, K.; Buseck, P. R.

1985-01-01

387

Interplanetary scintillation observations with the Cocoa Cross radio telescope  

NASA Technical Reports Server (NTRS)

Physical and electrical parameters for the 34.3-MHz Cocoa Cross radio telescope are given. The telescope is dedicated to the determination of solar-wind characteristics in and out of the ecliptic plane through measurement of electron-density irregularity structure as determined from IPS (interplanetary scintillation) of natural radio sources. The collecting area (72,000 sq m), angular resolution (0.4 deg EW by 0.6 deg NS), and spatial extent (1.3 km EW by 0.8 km NS) make the telescope well suited for measurements of IPS index and frequency scale for hundreds of weak radio sources without serious confusion effects.

Cronyn, W. M.; Shawhan, S. D.; Erskine, F. T.; Huneke, A. H.; Mitchell, D. G.

1976-01-01

388

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

389

The difference between the ion ramp structure of interplanetary and bow shocks  

NASA Astrophysics Data System (ADS)

Collisionless shocks play a significant role in the solar wind interaction with the planets, and their studies are important for understanding of physical processes in the vicinity of astrophysical objects. The main process that takes place at the collisionless shock is the redistribution of the energy of the directed plasma motion to the plasma thermalization and acceleration of a part of particles to high energies. The energy redistribution at the shock front is related to its structure because interactions with electromagnetic fields and waves act as particle collisions and form a magnetic field shock profile. It has been shown that the principal changes of magnetic and electric fields and electron moments take place on a scale comparable with the ion gyroradius. On the other hand, the time resolution of ion spectrometers prevents similar studies of the ion component. In the paper, we are analyzing differences in the ion structure of low-Mach number fast forward interplanetary shocks and bow shocks (as representatives of fast reverse shocks). The comparison is focused on the formation mechanism of both types of shocks and on a role that the ion gyromotion plays. The analysis is based on measurements of the BMSW solar wind monitor that provides the basic ion parameters with the 32 ms time resolution.

Goncharov, Oleksandr; Zastenker, Georgy; Nemecek, Zdenek; Safrankova, Jana; Prech, Lubomir; Pitna, Alexander

390

THE SOLAR WIND AND INTERPLANETARY FIELD DURING VERY LOW AMPLITUDE SUNSPOT CYCLES  

SciTech Connect

Cosmogenic isotope records indicate that a solar-cycle modulation persists through extended periods of very low sunspot activity. One immediate implication is that the photospheric field during such grand minima did not consist entirely of ephemeral regions, which produce a negligible amount of open magnetic flux, but continued to have a large-scale component originating from active regions. Present-day solar and heliospheric observations show that the solar wind mass flux and proton density at the coronal base scale almost linearly with the footpoint field strength, whereas the wind speed at Earth is uncorrelated with the latter. Thus a factor of {approx}4-7 reduction in the total open flux, as deduced from reconstructions of the interplanetary magnetic field (IMF) during the Maunder Minimum, would lead to a similar decrease in the solar wind densities, while leaving the wind speeds largely unchanged. We also demonstrate that a decrease in the strengths of the largest active regions during grand minima will reduce the amplitude of the Sun's equatorial dipole relative to the axial component, causing the IMF strength to peak near sunspot minimum rather than near sunspot maximum, a result that is consistent with the phase shift observed in the {sup 10}Be record during the Maunder Minimum. Finally, we discuss the origin of the 5 yr periodicity sometimes present in the cosmogenic isotope data during low and medium amplitude cycles.

Wang, Y.-M.; Sheeley, N. R. Jr., E-mail: yi.wang@nrl.navy.mil, E-mail: neil.sheeley@nrl.navy.mil [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)

2013-02-10

391

Effect of Interplanetary Shocks on AL and Dst Indices and Real-Time WINDMI  

NASA Astrophysics Data System (ADS)

Analytic solar wind signals are constructed using data from the ACE satellite for the 3-6 October 2000 and 15-24 April 2002 geomagnetic storm events, which included interplanetary shocks and magnetic clouds. The response of the WINDMI model, an eight dimensional model of the solar wind driven magnetosphere-ionosphere system, to the analytic signals was examined for these events. The role of the shocks are examined by using analytic signals in which the shock feature in the density, solar wind velocity, and magnetic field magnitude are tested individually. WINDMI results from the analytic inputs show that the shock events strongly impacted the AL index values but changed the Dst very little. Analysis of both the October 2000 and April 2002 storms showed that AL peaks associated with the shocks during these storms significantly depend on the jump in B. Real-time WINDMI downloads real-time data from ACE to predict the AL and Dst about 1-2 hours before the data is available for these indices from the Quicklook WDC-Kyoto website. Every ten minutes real-time AL and Dst data and WINDMI predictions are shown on this website: http://orion.ph.utexas.edu/˜windmi/realtime/. We show WINDMI real-time predictions that were captured for a recent storm on 14-15 April 2006. The work is supported by NSF-ATM grant 0539099.

Mays, Mona; Spencer, Edmund; Horton, Wendell

2006-10-01

392

Cosmic ray modulation and the solar magnetic field  

Microsoft Academic Search

We show that the variations of the interplanetary magnetic field strength (B) over a 22-year period are tracked by the inverted profile of the cosmic ray density measured by neutron monitors. We suggest that global changes in the Sun's magnetic field are more important for longterm modulation than magnetic field enhancements resulting from the merging of high-speed flows and coronal

H. V. Cane; G. Wibberenz; I. G. Richardson; T. T. von Rosenvinge

1999-01-01

393

A statistical survey of 5MeV proton events at transient interplanetary shocks  

Microsoft Academic Search

Between 1974 and 1985 the two Helios spacecraft observed 351 transient interplanetary shocks. For 5-MeV protons the particle events associated with these shocks can be divided into three groups: (1) events without intensity increase above quiet time or increased background (47%), (2) solar and interplanetary particle (SIP) events consisting of particles accelerated on or close to the Sun (solar or

May-Britt Kallenrode

1996-01-01

394

Covariant approximation averaging  

E-print Network

We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.

Eigo Shintani; Rudy Arthur; Thomas Blum; Taku Izubuchi; Chulwoo Jung; Christoph Lehner

2014-02-02

395

An Average Lunch?  

NSDL National Science Digital Library

This statistics activity requires students to find the mean using their TI-10 or TI-15 Explorer calculators. The task asks students to read part of Sideways Stories of Wayside School by Louis Sachar and find different combinations of lunches that would give an average price of $1.85. This resource includes a three-page PDF lesson plan with guiding questions, data collection page, and calculator instructions.

2008-06-09

396

Interplanetary Fast Shocks and Associated Drivers Observed through the Twenty-Third Solar Minimum by WIND Over its First 2.5 Years  

NASA Technical Reports Server (NTRS)

A list of the interplanetary (IP) shocks observed by WIND from its launch (in November 1994) to May 1997 is presented. Forty two shocks were identified. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using a practical scheme which combines two techniques. These techniques are a combination of the "pre-averaged" magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, on the one hand, and the Vinas and Scudder [1986] technique for solving the non-linear least-squares Rankine-Hugoniot shock equations, on the other. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. It is found that the mean strength and rate of occurrence of the shocks appears to correlated with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and start of solar cycle 23, which began around June 1996. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The distribution of their shock normals showed a mean direction peaking in the ecliptic plane and with a longitude (phi(sub n)) in that plane between perpendicular to the Parker spiral and radial from the Sun. When grouped according to the sense of the direction of propagation of the shocks the mean azimuthal (longitude) angle in GSE coordinates was approximately 194 deg for the fast-forward and approximately 20 deg for the fast-reverse shocks. Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These shocks had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientation well off the ecliptic plane. No shock propagated with longitude phi(sub n) >= 220 +/- 10 deg, this would suggest strong hindrance to the propagation of shocks contra a rather tightly winding Parker spiral. Examination of the obliquity angle theta(sub Bn) (that between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% was quasi-perpendicular, and some were very nearly perpendicular. About 32% of the shocks were oblique, and the rest (only 10%) were quasi-parallel, with one on Dec. 9, 1996 that showed field pulsations. Small uncertainty in the estimated angle theta(sub Bn) was obtained for about 10 shocks with magnetosonic Mach numbers between 1 and 2, hopefully significantly contributing to studies researching particle acceleration mechanisms at IP shocks, and to investigations where accurate values of theta(sub Bn) are crucial.

Mariani, F.; Berdichevsky, D.; Szabo, A.; Lepping, R. P.; Vinas, A. F.

1999-01-01

397

Typical and Unusual Properties of Magnetic Clouds during the WIND Era  

NASA Technical Reports Server (NTRS)

A list of 33 magnetic clouds as identified in WIND magnetic field and plasma data has been compiled. The intervals for these events are provided as part of NASA/GSFC, WIND-MFI's Website under the URL http://lepmfi.qsfc.nasa.gov/mfi/mag_cloud publ.html#table The period covered in this study is from early 1995 to November 1998 which primarily occurs in the quiet part of the solar cycle. A force free, cylindrically symmetric, magnetic field model has been applied to the field data in 1-hour averaged form for all of these events (except one small event where 10 min avg's were used) and the resulting fit-parameters examined. Each event was provided a semi-quantitatively determined quality factor (excellent, good or poor). A set of 28 good or better cases, spanning a surprisingly large range of values for its various properties, was used for further analysis. These properties are, for example, durations, attitudes, sizes, asymmetries, axial field strengths, speeds, and relative impact parameters. They will be displayed and analyzed, along with some related derived quantities, with emphasis on typical vs unusual properties and on the magnetic fields magnetic clouds' relationships to the Sun and to upstream interplanetary shocks, where possible. For example, it is remarkable how narrowly distributed the speeds of these clouds are, and the overall average speed (390 techniques km/s) is less than that normally quoted for the average solar wind speed (420 km/s) despite the fact that many of these clouds are d"drivers" of interplanetary shocks. On average, a cloud appears to be a little less symmetric when the spacecraft is able to pass close to the cloud's axis as compared to a farther out passage. The average longitude and latitude (in GSE) of the axes of the clouds are 85 degrees and 8 degrees, respectively, with standard deviations near 40 degrees. Also, the half=yearly averaged axial magnetic flux has approximately tripled. almost monotonically, from about 6 to 17 X 10(exp 29) Mx over the first 3.5 years of consideration, but with a large uncertainty on each of the half-year estimates, because of small sampling. If true,this finding implies an approximate tripling of the events' solar fluxes over this period as it goes into solar maximum.

Lepping, R. P.; Berdichevsky, D.; Szabo, A.; Burlaga, L. F.; Thompson, B. J.; Mariani, F.; Lazarus, A. J.; Steinberg, J. T.

1999-01-01

398

Interplanetary dust flux to the outer planet atmospheres  

NASA Astrophysics Data System (ADS)

It is now well established that an influx of external material is depositing significant amounts of oxygen into the atmospheres of the giant planets and Titan, which in turn impacts the energy budget, photochemistry, and structure of each body's atmosphere. While other sources (ie. Enceladus and/or the main ring system at Saturn, cometary impacts, etc.) also contribute, interplanetary dust grains are a significant source of external material to the outer planet atmospheres. In this talk, we present results from an interplanetary dust dynamics model used to calculate the distribution(s) of dust grains in the outer solar system that arise from Edgeworth-Kuiper Belt objects, Jupiter-family comets, and Halley-type comets. We constrain the densities of these distributions using in-situ measurements by the Pioneer meteoroid detectors and the New Horizons Student Dust Counter. In turn, we calculate the total dust influx distribution to each outer planet atmosphere, including any temporal or compositional variability and spatial anisotropies. Finally, we compare our influx estimates with those derived from extrapolating dust fluxes at 1 AU to the outer solar system and discuss implications for the outer planet atmospheres.

Poppe, A. R.; Moses, J. I.

2013-12-01

399

Interplanetary dust fluxes measurements using the Waves instrument on STEREO  

NASA Astrophysics Data System (ADS)

Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 A.U. being comparable to the one of the solar wind. The impact of a dust particle on a spacecraft produces a plasma cloud whose associated electric field is detected by the on-board electric antennas. The signal measured by the wave instruments thus reveals the dust properties. We analyse the dust particle impacts on the STEREO spacecraft during the 2007-2010 period. We use the TDS waveform sampler of the STEREO/WAVES instrument, which enables us to deduce considerably more informations than in a previous study based on the LFR spectral analyzer [Meyer-Vernet et al., 2009]. We observe two distinct populations of dust that we infer to be nano and micron sized dust particles and we derive their fluxes at 1 AU and the evolution of these fluxes with time (and solar longitude). The observations are also in accord with the dynamics of nanometer-sized and micrometer-sized dust particles in the interplanetary medium.

Zaslavsky, A.; Meyer-Vernet, N.; Mann, I.; Czechowski, A.; Issautier, K.; Le Chat, G.; Maksimovic, M.; Kasper, J. C.

2010-12-01

400

Interplanetary dust influx to the Pluto-Charon system  

NASA Astrophysics Data System (ADS)

The influx of interplanetary dust grains (IDPs) to the Pluto-Charon system is expected to drive several physical processes, including the formation of tenuous dusty rings and/or exospheres, the deposition of neutral material in Pluto's atmosphere through ablation, the annealing of surface ices, and the exchange of ejecta between Pluto and its satellites. The characteristics of these physical mechanisms are dependent on the total incoming mass, velocity, variability, and composition of interplanetary dust grains; however, our knowledge of the IDP environment in the Edgeworth-Kuiper Belt has, until recently, remained rather limited. Newly-reported measurements by the New Horizons Student Dust Counter combined with previous Pioneer 10 meteoroid measurements and a dynamical IDP tracing model have improved the characterization of the IDP environment in the outer Solar System, including at Pluto-Charon. Here we report on this modeling and data comparison effort, including a discussion of the IDP influx to Pluto and its moons, and the implications thereof.

Poppe, Andrew R.

2015-01-01

401

Observational Evidence for Double Helix Structure in CMEs and Magnetic Clouds  

NASA Astrophysics Data System (ADS)

We compare recent observations of a solar eruptive prominence as seen in extreme UV light on March 30, 2010 by the Solar Dynamics Observatory (SDO) with the multi-tube model for interplanetary magnetic clouds (Osherovich et al., GRL 26, 2597, 1999). Our model is based on an exact analytical solution of the plasma equilibrium with magnetic force balanced by a gradient of scalar gas pressure. Topologically this solution describes two magnetic helices with equal absolute value of magnetic flux, but with opposite magnetic polarity embedded in a cylindrical magnetic flux tube which creates magnetic flux inequality between the two helices by enhancing one helix and suppressing the other. This also leads to a difference in the gas pressure deficit associated with each helix. The magnetic field in this model is continuous everywhere and has finite magnetic energy per unit length of the cylindrical tube. Such configurations have been introduced by Osherovich (Soln. Dann., 5, 70, 1975) as MHD bounded states. It appears that the SDO observations depict two non-equal magnetically interacting helices described by the ground state solution of this analytical model. We consider magnetic and thermodynamic signatures of multiple magnetic flux ropes inside the same magnetic cloud, using electron and proton in situ observations. The ratio of magnetic energy density to bulk speed solar wind energy density has been defined as a solar wind quasi-invariant (QI) (Osherovich et al. 1999). For most of the solar wind, QI << 1, but for magnetic clouds, QI has anomalously large values of more than an order of magnitude greater than that of the average solar wind. In this paper, we analyze the structure of the QI profiles for 12 clouds observed by Ulysses to probe their internal topology with results consistent with our double helix model.

Osherovich, V.; Fainberg, J.; Webb, A.

2012-12-01

402

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

403

Journal of Atmospheric and Solar-Terrestrial Physics 67 (2005) 17341743 Tracing magnetic helicity from the solar corona to the  

E-print Network

and higher magnetic field strength than the surrounding solar wind. Typically, the magnetic field vector, the Solar Wind Experiment and the Magnetic Field Instrument (MFI) on board the Wind spacecraft registered magnetic fields; Solar activity; Interplanetary magnetic clouds 1. Introduction Coronal mass ejections

Dasso, Sergio

404

Quiet-time average auroral configuration  

Microsoft Academic Search

The spatial pattern of auroral electron precipitation during magnetically quiet intervals was studied. The result is compared with the Feldstein (1963) auroral oval and other reported configurations of auroral optical emission. The precipitation of auroral electrons takes place in an irregularly shaped annular belt encircling the pole. The belt is composed of two parts: the equatorial part (average energy greater

K. Lassen; C. Danielsen; C.-I. Meng

1988-01-01

405

Geomagnetic storm intensity forecast caused by magnetic clouds of solar wind  

NASA Astrophysics Data System (ADS)

Method of short-term forecast intensity of geomagnetic storms, expected by effect Solar wind magnetic clouds in the Earth's magnetosphere is developed. The method is based calculation of the magnetic field clouds distribution, suitable to the Earth, the initial satellite measurements therein components of the interplanetary magnetic field in the solar ecliptic coordinate system. Conclusion about the magnetic storm intensity is expected on the basis of analysis of the dynamics of the reduced magnetic field Bz component clouds and established communication intensity of geomagnetic storms on Dst-index values and Bz component of the interplanetary magnetic field vector.

Barkhatov, N. A.; Levitin, A. E.; Revunova, E. A.

2014-11-01

406

Acceleration of Solar Wind Ions by Nearby Interplanetary Shocks: Comparison of Monte Carlo Simulations with Ulysses Observations  

E-print Network

The most stringent test of theoretical models of the first-order Fermi mechanism at collisionless astrophysical shocks is a comparison of the theoretical predictions with observational data on particle populations. Such comparisons have yielded good agreement between observations at the quasi-parallel portion of the Earth's bow shock and three theoretical approaches, including Monte Carlo kinetic simulations. This paper extends such model testing to the realm of oblique interplanetary shocks: here observations of proton and alpha particle distributions made by the SWICS ion mass spectrometer on Ulysses at nearby interplanetary shocks are compared with test particle Monte Carlo simulation predictions of accelerated populations. The plasma parameters used in the simulation are obtained from measurements of solar wind particles and the magnetic field upstream of individual shocks. Good agreement between downstream spectral measurements and the simulation predictions are obtained for two shocks by allowing the the ratio of the mean-free scattering length to the ionic gyroradius, to vary in an optimization of the fit to the data. Generally small values of this ratio are obtained, corresponding to the case of strong scattering. The acceleration process appears to be roughly independent of the mass or charge of the species.

Matthew G. Baring; Keith Ogilvie; Donald Ellison; Robert Forsyth

1996-10-02

407

Cluster observations on linear magnetic decreases in the solar wind at 1 AU  

NASA Astrophysics Data System (ADS)

Magnetic decreases (MDs) are structures observed in interplanetary space with significant decreases in the magnetic field magnitude, of which the events with no or little change in the field direction are linear magnetic decreases (LMDs). Xiao et al., (2010) have reported that the geometrical shape of LMDs observed in the solar wind at 1 AU was consistent with rotational ellipsoid, and the occurrence rate was about 3.7 LMDs/d. It was found that not only the occurrence rate but also the geometrical shape of LMDs had no significant change from 0.72 AU to 1 AU in comparison with Zhang et al., (2008)'s results, which may infer that most of LMDs observed at 1 AU were formed and fully developed before 0.72 AU. Recently, we have focused on the magnetic field and plasma (e.g. ion density and velocity) characteristics of those LMD structures observed during the period of 2001 to 2009. Compared with the average solar wind condition, it is shown that the LMDs prefer to be observed in the region with relatively lower magnetic field magnitude, higher ion density, larger plasma ? (ratio of the thermal pressure to the magnetic pressure) and slower solar wind velocity. We also investigated the LMDs which located in the interplanetary coronal mass ejections (ICME) or the sheath of the ICME. It is found that the events related to ICMEs could account for more than 20% of LMDs during solar maximum. Therefore, the ICME should be an important source of the LMDs during the solar maximum. However, other mechanisms during the solar minimum may be more important, because the occurrence rate of LMDs during the solar minimum is higher than that of the solar maximum. We also calculate the propagation speed of the structures in the solar wind frame to infer the generation mechanism of these structures.

Xiao, T.; Shi, Q.; Tian, A.; Fu, S.; Pu, Z.; Zong, Q.; Sun, W.; Lucek, E. A.; Reme, H.

2013-12-01

408

Analysis of the three intense geomagnetic storm observed on july 20-31, 2004: solar, interplanetary and cosmic ray effects near the Earth.  

NASA Astrophysics Data System (ADS)

Geomagnetic storms are geomagnetic field disturbances caused by gusts in the solar wind injecting a substantial quantity of energy into the magnetosphere intensifying the ring current becoming strong enough to exceed some key threshold of the quantifying storm time Dst index In this work we analyze three intense geomagnetic storms Dst -100nT occurred in period of July 22nd 24th and 27th 2004 We use images of solar corona made by Large Angle and Spectroscopic Coronagraph LASCO and the solar disk made by the Extreme Ultraviolet Imaging Telescope EIT aboard the Solar and Heliospheric Observatory SOHO Observations of plasma and interplanetary magnetic field obtained by the Advanced Composition Explorer ACE were also used We analyze high energy cosmic ray observations obtained using the Muon Telescope of the Brazilian Southern Space Observatory-SSO of the INPE s Southern Regional Space Research Center at 29o26 24 S 53o48 38 W for identify Forbush decreases in the cosmic ray intensity The main objective of this work is study three intense geomagnetic storms Dst - 100 nT that occurred in a relatively small time interval in order to identify their solar origin interplanetary counterparts and cosmic ray modulation near the Earth This study is important for the study of energetic cosmic rays modulation due to a subsequent chain of interplanetary disturbances and in the near future it will help the understanding of space weather cosmic ray variability

Savian, J. F.; da Silva, M. R.; Dal Lago, A.; Braga, C. R.; da Silva, C. W.; Dos Santos, L. C.; da Silva, S. M.; Munakata, K.; Kuwabara, T.; Schuch, N. J.

409

Porosity of an Anhydrous Chondritic Interplanetary Dust Particle  

NASA Astrophysics Data System (ADS)

Determination of the density and porosity of Interplanetary Dust Particles (IDPs) is important in the dynamics of collisional and orbital evolution of small-sized particles. These measurements are also useful to suggest possible sources for IDPs based on comparisons with known extraterrestrial materials (e.g., chondrites). Previous work on IDPs shows a wide range of densities from very low (0.08 g/cm3 [1]) through low (0.3 g/cm3 [2]) to high (6.2 g/cm3 [3]), with an average density at 2.0 g/cm3 for 150 particles [2]. In another study, IDPs fall into two distinct density groups with mean values of 0.6 g/cm3 and 1.9g/cm3 [3]. In general, chondritic IDPs with lower density values most likely have appreciable porosity, suggesting they are primitive, uncompacted particles. It is believed that porosities greater than 70% are rare [2]. Sample In this study, porosity measurements were determined for one IDP, Clu17. This chondritic particle is a fragment of a large-sized IDP (L2008#5) known as a cluster particle. The cluster is composed of 53 fragments >5 micrometers in diameter; a detailed description of the cluster is given in [4]. IDP Clu17 has ~12 wt.% C and contains chondritic abundances (within 2xCI) for major elements. This fragment is dominated by fine-grained aggregates, also known as GEMS (glass with embedded metal and sulfide [5]), and contains some olivine, pyroxene, Fe-Ni sulfides, and carbonaceous material. Methods IDP Clu17 was analyzed for light elements quantitatively analysis using scanning electron microscopy and thin-window energy dispersive spectrometry [details of technique in 4]. Following the initial bulk chemical analysis, the particle was embedded in epoxy, thin sectioned using an ultramicrotome, and examined with a JEOL 2000 FX transmission electron microscope. Many of the sections were not complete; individual grains in some sections are lost during microtoming. Photos from nine of the best sections were digitized by scanning at 1200 dpi. The images were cropped and reduced in size to fit the memory capabilities of the computer analysis program. The digitized images were measured using NIH Image on a Macintosh computer. Results Using a combination of tools, including density slicing, area selection and a graphics tablet, to measure porosity, the sections give values from 9 to 15% porosity. There are a variety of errors that can enter into the measurement process: (1) defining exterior surface boundaries, which can vary between sections, (2) presence of holes in the sections where grains fell out during microtoming, and (3) differentiation between the mounting medium (epoxy) and extraterrestrial components (carbonaceous material can look similar to epoxy). As noted in earlier work [6], image processing is somewhat subjective and requires careful judgment in setting the conditions for electron microscopy and digital scanning. Conclusions Typical published anhydrous IDP porosities are in the 40% range [2], a value significantly higher than the 9-15% porosity range for IDP Clu17. The porosity values for cluster particles may be more difficult to determine because both the inter- and intra-fragment porosities must be considered. The inter-fragment porosity of ~10% for Clu17 is probably much lower than the intra-fragment porosity for cluster L2008#5 because this IDP remained intact on the collection surface while the cluster particle was fragmented into hundreds of smaller units, likely reflecting an high initial cluster porosity and low coherence. We conclude that image analysis combined with microtome sectioning offers a useful new tool for porosity measurements of IDPs and other kinds of extraterrestrial materials. Acknowledgments: This work was supported by NASA/JOVE Grant #NAG8-999. References: [1] Rietmeijer F. (1993) EPSL, 117, 609. [2] Love S. et al. (1994) Icarus, 111, 227. [3] Flynn G. and Sutton S. (1991) Proc. LPS, Vol. 21, 541. [4] Thomas K. et al. (1995) GCA, in press. [5] Bradley J. (1994) Science, 265, 925. [6] Strait M. et. al. (1994) Meteoritics, 29, 537.

Strait, M. M.; Thomas, K. L.; McKay, D. S.

1995-09-01

410

Orbit-averaged guiding-center Fokker-Planck operator  

SciTech Connect

A general orbit-averaged guiding-center Fokker-Planck operator suitable for the numerical analysis of transport processes in axisymmetric magnetized plasmas is presented. The orbit-averaged guiding-center operator describes transport processes in a three-dimensional guiding-center invariant space: the orbit-averaged magnetic-flux invariant {psi}, the minimum-B pitch-angle coordinate {xi}{sub 0}, and the momentum magnitude p.

Brizard, A. J. [Department of Chemistry and Physics, Saint Michael's College, Colchester, Vermont 05439 (United States); Decker, J.; Peysson, Y.; Duthoit, F.-X. [CEA, IRFM, Saint-Paul-lez-Durance F-13108 (France)

2009-10-15

411

Analysis of the contact graph routing algorithm: Bounding interplanetary paths  

NASA Astrophysics Data System (ADS)

Interplanetary communication networks comprise orbiters, deep-space relays, and stations on planetary surfaces. These networks must overcome node mobility, constrained resources, and significant propagation delays. Opportunities for wireless contact rely on calculating transmit and receive opportunities, but the Euclidean-distance diameter of these networks (measured in light-seconds and light-minutes) precludes node discovery and contact negotiation. Propagation delay may be larger than the line-of-sight contact between nodes. For example, Mars and Earth orbiters may be separated by up to 20.8 min of signal propagation time. Such spacecraft may never share line-of-sight, but may uni-directionally communicate if one orbiter knows the other's future position. The Contact Graph Routing (CGR) approach is a family of algorithms presented to solve the messaging problem of interplanetary communications. These algorithms exploit networks where nodes exhibit deterministic mobility. For CGR, mobility and bandwidth information is pre-configured throughout the network allowing nodes to construct transmit opportunities. Once constructed, routing algorithms operate on this contact graph to build an efficient path through the network. The interpretation of the contact graph, and the construction of a bounded approximate path, is critically important for adoption in operational systems. Brute force approaches, while effective in small networks, are computationally expensive and will not scale. Methods of inferring cycles or other librations within the graph are difficult to detect and will guide the practical implementation of any routing algorithm. This paper presents a mathematical analysis of a multi-destination contact graph algorithm (MD-CGR), demonstrates that it is NP-complete, and proposes realistic constraints that make the problem solvable in polynomial time, as is the case with the originally proposed CGR algorithm. An analysis of path construction to complement hop-by-hop forwarding is presented as the CGR-EB algorithm. Future work is proposed to handle the presence of dynamic changes to the network, as produced by congestion, link disruption, and errors in the contact graph. We conclude that pre-computation, and thus CGR style algorithms, is the only efficient method of routing in a multi-node, multi-path interplanetary network and that algorithmic analysis is the key to its implementation in operational systems.

Birrane, Edward; Burleigh, Scott; Kasch, Niels

2012-06-01

412

Some Peculiar Properties of Magnetic Clouds as Observed by the WIND Spacecraft  

NASA Technical Reports Server (NTRS)

We aimed at understanding the common characteristics of magnetic clouds, relevant to solar-interplanetary connections, but exceptional ones were noted and are stressed here through a short compendium. The study is based on analyses of 28 good or better events (Out of 33 candidates) as identified in WIND magnetic field and plasma data. These cloud intervals are provided by WIND-MFI's Website under the URL (http://lepmfi.gsfc.nasa.gov/mfi/mag_cloud_publ.html#table). The period covered is from early 1995 to November 1998. A force free, cylindrically symmetric, magnetic field model has been applied to the field data in usually 1-hour averaged form for the cloud analyses. Some of the findings are: (1) one small duration event turned out to have an approximately normal size which was due to a distant almost "skimming" passage by the spacecraft; (2) One truly small event was observed, where 10 min averages had to be used in the model fitting; it had an excellent model fit and the usual properties of a magnetic cloud, except it possessed a small axial magnetic flux; (3) One cloud ha a dual axial-field-polarity, in the sense that the "core" had one polarity and the annular region around it had an opposite polarity. This event also satisfied the model and with a ve3ry good chi-squared value. Some others show a hint of this dual polarity; (4) The temporal distribution of occurrence clouds over the 4 years show a dip in 1996; (5) About 50 % of the clouds had upstream shocks; any others had upstream pressure pulses; (6) The overall average speed (390 km/s) of the best 28 events is less than the normally quoted for the average solar wind speed (420 km/s) The average of central cloud speed to the upstream solar wind speed was not much greater than one (1.08), even though many of these clouds were drivers of interplanetary shocks. Cloud expansion is partly the reason for the existence of upstream shocks; (7) The cloud axes often (about 50 % of the time) revealed reasonable attitudes with respect to the interpreted solar source, from simple geometry, but many bore no relationship, suggesting that their observations at 1 AU were probably those of the legs of the global cloud often having near-radial axes; (8) many clouds appear to have magnetic holes at or their their boundaries.

Berdichevsky, D.; Lepping, R. P.; Szabo, A.; Burlaga, L. F.; Thompson, B. J.; Lazarus, A. J.; Steinburg, J. T.; Mariani, F.

1999-01-01

413

Modeling a space weather event from the Sun to the Earth: CME generation and interplanetary propagation  

NASA Astrophysics Data System (ADS)

We present a three-dimensional (3-D) numerical ideal magnetohydrodynamics (MHD) model describing the time-dependent expulsion of a coronal mass ejection (CME) from the solar corona propagating to 1 astronomical unit (AU). The simulations are performed using the Block Adaptive Tree Solar-Wind Roe Upwind Scheme (BATS-R-US) code. We begin by developing a global steady-state model of the corona that possesses high-latitude coronal holes and a helmet streamer structure with a current sheet at the equator. The Archimedean spiral topology of the interplanetary magnetic field is reproduced along with fast and slow speed solar wind. Within this model system, we drive a CME to erupt by the introduction of a Gibson-Low magnetic flux rope that is anchored at both ends in the photosphere and embedded in the helmet streamer in an initial state of force imbalance. The flux rope rapidly expands and is ejected from the corona with maximum speeds in excess of 1000 km/s. Physics-based adaptive mesh refinement (AMR) allows us to capture the structure of the CME focused on a particular Sun-Earth line with high spatial resolution given to the bow shock ahead of the flux rope as well as to the current sheet behind. The CME produces a large magnetic cloud at 1 AU (>100 R?) in which Bz undergoes a full rotation from north to south with an amplitude of 20 nT. In a companion paper, we find that the CME is very effective in generating strong geomagnetic activity at the Earth in two ways. First, through the strong sustained southward Bz (lasting more than 10 hours) and, second, by a pressure increase associated with the CME-driven shock that compresses the magnetosphere.

Manchester, Ward B.; Gombosi, Tamas I.; Roussev, Ilia; Ridley, Aaron; de Zeeuw, Darren L.; Sokolov, I. V.; Powell, Kenneth G.; Tóth, GáBor

2004-02-01

414

The interplanetary shock impact on the Earth's magnetotail  

NASA Astrophysics Data System (ADS)

We present multispacecraft observations of the Earth's magnetotail motion and deformation as a result of an interplanetary (IP) shock arrival. Since April 2011, two Artemis spacecraft spend about four days in the near lunar orbit at the Earth's magnetotail and the BMSW instrument onboard the Spektr-R project is located three months per year at the same region. During this period, a lot of CMEs and IP shocks were observed in the solar wind. We trace the IP shock propagation from the L1 point (Wind and ACE) to the tail where shock arrival is registered by Themis/Artemis and Spektr-R. We discuss large-scale dynamic changes of the magnetotail motion as well as the IP shock influence on the reconnection process.

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

2014-05-01

415

The spectral properties of collected interplanetary dust particles  

NASA Technical Reports Server (NTRS)

The observed spectral and mineralogical properties of interplanetary dust particles (IDP) allows the conclusion that: (1) the majority of IDP infrared spectra are dominated by olivine, pyroxene, or layer lattice silicate minerals, (2) to the first order the emission spectra of comets Halley and Kohoutek can be matched by mixtures of these IDP infrared types, implying that comets contain mixtures of these different crystalline silicates and may vary from comet to comet and perhaps even within a single comet, (3) do not expect to observe a single 20 micron feature in cometary spectra, (4) carbonaceous materials dominate the visible spectra properties of the IDPs even though the mass in these particles consists primarily of silicates, and (5) the particle characteristics summarized need to be properly accounted for in future cometary emission models.

Sandford, S. A.

1988-01-01

416

The far magnetotail response to an interplanetary shock arrival  

NASA Astrophysics Data System (ADS)

We present a study of the impact of the December 7, 2003 fast forward interplanetary (IP) shock on the distant tail of the Earth's magnetosphere. Using the data from the several spacecraft located in the solar wind/magnetosheath upstream to the Earth, we monitor a propagation of the IP shock from the L1 point to the magnetosphere. A behavior of the far magnetotail is inferred from the Wind observations at XGSM?-230 RE. Shortly after the shock arrival, Wind crossed consequentially southern and northern lobes and observed a flux rope and the tailward fast plasma flow (?780 km/s) within the plasmasheet. Moreover, a change of the solar wind VZ component across the shock creates a huge kink of the tail magnetosphere that propagates down the tail with the IP shock.

Grygorov, K.; P?ech, L.; Šafránková, J.; N?me?ek, Z.; Goncharov, O.

2014-11-01

417

Carbon Raman Spectroscopy of 36 Inter-Planetary Dust Particles  

NASA Technical Reports Server (NTRS)

Carbon Raman spectroscopy is a useful tool to determine the degree of order of organic material (OM) in extra-terrestrial matter. As shown for meteoritic OM [e.g., 2], peak parameters of D and G bands are a measure of thermal alteration, causing graphitization (order), and amorphization, e.g. during protoplanetary irradiation, causing disorder. Th e most pristine interplanetary dust particles (IDPs) may come from comets. However, their exact provenance is unknown. IDP collection during Earth?s passage through comet Grigg-Skjellerup?s dust stream ("GSC" collectors) may increase the probability of collecting fresh IDPs from a known, cometary source. We used Raman spectroscopy to compare 21 GSC-IDPs with 15 IDPs collected at different periods, and found that the variation among GSC-IDPs is larger than among non-GSC IDPs, with the most primitive IDPs being mostly GSC-IDPs.

Busemann, H.; Nittler, L. R.; Davidson, J.; Franchi, I. A.; Messenger, S.; Nakamura-Messenger, K.; Palma, R. L.; Pepin, R. O.

2009-01-01

418

Cometary evolution: Clues from chondritic interplanetary dust particles  

NASA Technical Reports Server (NTRS)

Cometary and interplanetary dust particles (IDP) are compared, and the mineralogical evolution of comet nuclei is discussed. Chondritic IDP have properties consistent with properties expected for cometary dust. The complex and varied mineralogy of these particles may indicate mineral alteration processes that occur in comet nuclei. Depending on the thermal budget of a comet, the upper few meters of nucleus material may maintain temperatures within regimes of hydrocryogenic (200 to 237 K) and low-temperature aqueous (274 to 400 K) alteration. Thus, layer silicates, carbonates, and sulfates may be important components of cometary dust and, correspondingly are common constituents of chondritic IDPs. Alteration of comet starting materials may be a common occurrence, and depends on the specific physical and chemical properties of each individual comet.

Reitmeijer, F. J. M.; Mackinnon, I. D. R.

1987-01-01

419

Solar flare nuclear gamma rays and interplanetary proton events  

NASA Technical Reports Server (NTRS)

We compared flare gamma ray line (GRL) events and solar energetic proton (SEP) events for the period from Feb. 1980 - Jan. 1985 and substantiated earlier results showing a lack of correlation between gamma-ray-producing ions and interplanetary protons. This poor correlation results primarily from several large SEP events that originated in flares without detectable gamma ray emission. The converse case of GRL events unassociated with SEP events is rare. We present evidence which suggests that the ratio of trapped to escaping protons in GRL/SEP flares depends on the spatial scale size of the flare. We affirm the result of Bai and Dennis (1985) that GRL flares are generally accompanied (75 percent) by metric Type 2 bursts.

Cliver, E. W.; Forrest, D. J.; Mcguire, R. E.; Vonrosenvinge, T. T.; Reames, D. V.; Cane, H. V.; Kane, S. R.

1987-01-01

420

Multielement analysis of interplanetary dust particles using TOF-SIMS  

NASA Technical Reports Server (NTRS)

Sections of three stratospheric particles (U2015G1, W7029*A27, and L2005P9) were analyzed with TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectrometry) continuing our efforts to investigate the element distribution in interplanetary dust particles (IDP's) with high lateral resolution (approximately 0.2 micron), to examine possible atmospheric contamination effects, and to further explore the abilities of this technique for element analysis of small samples. The samples, previously investigated with SXRF (synchrotron X-ray fluorescence analysis), are highly enriched in Br (Br/Fe: 59 x CI, 9.2 x CI, and 116 x CI, respectively). U2015G1 is the IDP with the by far highest Zn/Fe-ratio (81 x CI) ever reported in chondritic particles.

Stephan, T.; Kloeck, W.; Jessberger, E. K.; Rulle, H.; Zehnpfenning, J.

1993-01-01