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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, authored and curated by David P. Stern, 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.

Mendez, J.

3

Interplanetary magnetic field data book  

NASA Technical Reports Server (NTRS)

An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

King, J. H.

1975-01-01

4

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

5

Average high latitude magnetic field: Variations with interplanetary sector and with season. 2: Comparison of disturbance levels and discussion of ionospheric currents  

NASA Technical Reports Server (NTRS)

Average high latitude magnetic field data from northern observatories are examined for three ranges of magnetic disturbance level, Kp = 1 minus to 1+,2 minus to 3+, and or = 4 minus. Except for 0-8h MLT, 55-78 deg invariant latitude, during away interplanetary magnetic field sectors, the variations between season and sector have the the same characteristics at all Kp ranges. Because the amplitude of sector differences is much larger at sunlit local times than in the midnight sector, it is concluded that the current system of Svalgaard (1973) is not adequate to describe the sector variations in magnetic disturbance, other current systems are discussed briefly. The disturbance morphology and seasonal variation at all Kp levels confirms the results of previous studies which indicate that latitudinally broad current systems and non-ionospheric sources are present in addition to latitudinally narrow electrojet currents. Comparison of data between Kp levels indicates that the Harang discontinuity shifts toward earlier MLT with increasing Kp level.

Langel, R. A.; Brown, N.

1973-01-01

6

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

7

Evolution of the interplanetary magnetic field  

SciTech Connect

Remote observations of magnetic field topologies in the solar corona and in situ observations of the solar wind and interplanetary magnetic field (IMF) in interplanetary space are used to examine the temporal evolution of the spatial distribution of open and closed field regions emanating from the Sun. The simple ``open`` configuration of inward and outward pointing sectors in the IMF is periodically disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from previously closed magnetic field regions in the corona into interplanetary space. At 1 AU, CMEs contain counterstreaming halo electrons which indicate their distinct magnetic topologies. This topology is generally thought to be: plasmoids that are completely disconnected from the Sun; magnetic ``bottles,`` still tied to the corona at both ends; or flux ropes which are only partially disconnected. Fully disconnected plasmoids would have no long term effect on the amount of open flux; however, both in situ observations of details of the halo electron distributions and remote coronagraph observations of radial fields following CMEs indicate that CMEs generally do retain at least partial attached to the Sun. Both the magnetic-bottle and flux rope geometries require some mitigating process to close off previously open fields in order to avoid a flux catastrophe. In addition, the average amount of magnetic flux observed in interplanetary space varies over the solar cycle, also indicating that there must be ways in which new flux is opened and previously open flux is closed off. The most likely scenario for closing off open magnetic fields is for reconnection to occurs above helmet streamers, where oppositely directed field regions are juxtaposed in the corona. These events would serve to return closed field arches to the Sun and release open, U-shaped structures into the solar wind.

McComas, D.J.

1993-05-01

8

Evolution of the interplanetary magnetic field  

SciTech Connect

Remote observations of magnetic field topologies in the solar corona and in situ observations of the solar wind and interplanetary magnetic field (IMF) in interplanetary space are used to examine the temporal evolution of the spatial distribution of open and closed field regions emanating from the Sun. The simple open'' configuration of inward and outward pointing sectors in the IMF is periodically disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from previously closed magnetic field regions in the corona into interplanetary space. At 1 AU, CMEs contain counterstreaming halo electrons which indicate their distinct magnetic topologies. This topology is generally thought to be: plasmoids that are completely disconnected from the Sun; magnetic bottles,'' still tied to the corona at both ends; or flux ropes which are only partially disconnected. Fully disconnected plasmoids would have no long term effect on the amount of open flux; however, both in situ observations of details of the halo electron distributions and remote coronagraph observations of radial fields following CMEs indicate that CMEs generally do retain at least partial attached to the Sun. Both the magnetic-bottle and flux rope geometries require some mitigating process to close off previously open fields in order to avoid a flux catastrophe. In addition, the average amount of magnetic flux observed in interplanetary space varies over the solar cycle, also indicating that there must be ways in which new flux is opened and previously open flux is closed off. The most likely scenario for closing off open magnetic fields is for reconnection to occurs above helmet streamers, where oppositely directed field regions are juxtaposed in the corona. These events would serve to return closed field arches to the Sun and release open, U-shaped structures into the solar wind.

McComas, D.J.

1993-01-01

9

Magnetic sails and interplanetary travel  

SciTech Connect

A new concept, the magnetic sail, or 'magsail' is proposed which propels spacecraft by using the magnetic field generated by a loop of superconducting cable to deflect interplanetary or interstellar plasma winds. The performance of such a device is evaluated using both a plasma particle model and a fluid model, and the results of a series of investigations are presented. It is found that a magsail sailing on the solar wind at a radius of one astronautical unit can attain accelerations on the order of 0.01 m/sec squared, much greater than that available from a conventional solar lightsail, and also greater than the acceleration due to the sun's gravitational attraction. A net tangential force, or 'lift' can also be generated. Lift to drag ratios of about 0.3 appear attainable. Equations are derived whereby orbital transfers using magsail propulsion can be calculated analytically.

Zubrin, R.M.; Andrews, D.G.

1989-01-01

10

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

11

Interplanetary Magnetic Field Guiding Relativistic Particles  

NASA Technical Reports Server (NTRS)

The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth.

Masson, S.; Demoulin, P.; Dasso, S.; Klein, K. L.

2011-01-01

12

Power spectra of the interplanetary magnetic field  

Microsoft Academic Search

Power spectra based on Pioneer 6 interplanetary magnetic field data in early 1966 exhibit a frequency dependence of f-2 in the range 2.8 × 10-4 to 1.6 × 10-2 cps for periods of both quiet and disturbed field conditions. Both the shape and power levels of these spectra are found to be due to the presence of directional discontinuities in

James W. Sari; Norman F. Ness

1969-01-01

13

Magnetic shielding for interplanetary spacecraft  

SciTech Connect

The protection of spacecraft crews from the radiation produced by high energy electrons, protons and heavier ions in the space environment is a major health concern on long duration missions. Conventional approaches to radiation shielding in space have relied on thicker spacecraft walls to stop the high energy charged particles and to absorb the resulting gamma and bremsstrahlung photons. The shielding concept described here uses superconducting magnets to deflect charged particles before they collide with the spacecraft, thus avoiding the production of secondary particles. A number of spacecraft configurations and sizes have been analyzed, ranging from a small ``storm cellar`` for use during solar flares to continuous shielding for space stations having a crew of 15--25. The effectiveness of the magnetic shielding has been analyzed using a Monte Carlo program with incident proton energies from 0.5 to 1000 MeV. Typically the shield deflects 35--99 percent of the incident particles, depending, of course on particle energy and magnetic field strength. Further evaluation studies have been performed to assess weight comparisons between magnetic and conventional shielding; to determine magnet current distributions which minimize the magnetic field within the spacecraft itself; and to assess the potential role of ceramic superconductors. 2 figs., 8 tabs.

Herring, J.S.; Merrill, B.J.

1991-12-01

14

Magnetic shielding for interplanetary spacecraft  

SciTech Connect

The protection of spacecraft crews from the radiation produced by high energy electrons, protons and heavier ions in the space environment is a major health concern on long duration missions. Conventional approaches to radiation shielding in space have relied on thicker spacecraft walls to stop the high energy charged particles and to absorb the resulting gamma and bremsstrahlung photons. The shielding concept described here uses superconducting magnets to deflect charged particles before they collide with the spacecraft, thus avoiding the production of secondary particles. A number of spacecraft configurations and sizes have been analyzed, ranging from a small storm cellar'' for use during solar flares to continuous shielding for space stations having a crew of 15--25. The effectiveness of the magnetic shielding has been analyzed using a Monte Carlo program with incident proton energies from 0.5 to 1000 MeV. Typically the shield deflects 35--99 percent of the incident particles, depending, of course on particle energy and magnetic field strength. Further evaluation studies have been performed to assess weight comparisons between magnetic and conventional shielding; to determine magnet current distributions which minimize the magnetic field within the spacecraft itself; and to assess the potential role of ceramic superconductors. 2 figs., 8 tabs.

Herring, J.S.; Merrill, B.J.

1991-01-01

15

Geometry of interplanetary magnetic clouds  

NASA Technical Reports Server (NTRS)

Two dimensional magnetohydrodynamic simulations are presented of the distortion of a magnetic flux rope that is being accelerated through ambient solar wind plasma. The flux rope magnetic field has an axial component parallel to the solar wind field and an azimuthal component, which lies in the simulation plane. As the flux rope moves through the solar wind plasma, vortices form on its trailing edge and couple strongly to its interior. If the flux rope azimuthal field is weak, it deforms into an elongated banana-like shape a few Alfven transit times. A strong azimuthal field component tends to inhibit this distortion. If the flux rope is taken to model a magnetic cloud, it is suggested that the shape of the cloud at 1 AU is determined by its distortion in the inner solar wind. Distortion timescales beyond 1 AU are estimated as many days. It is estimated that effective drag coefficients somewhat greater than unity are appropriate for modelling flux rope propagation.

Cargill, P. J.; Chen, J.; Spicer, D. S.; Zalesak, S. T.

1995-01-01

16

EULERIAN DECORRELATION OF FLUCTUATIONS IN THE INTERPLANETARY MAGNETIC FIELD  

SciTech Connect

A method is devised for estimating the two-time correlation function and the associated Eulerian decorrelation timescale in turbulence. With the assumptions of a single decorrelation time and a frozen-in flow approximation for the single-point analysis, the method compares two-point correlation measurements with single-point correlation measurements at the corresponding spatial lag. This method is applied to interplanetary magnetic field measurements from the Advanced Composition Explorer and Wind spacecraft. An average Eulerian decorrelation time of 2.9 hr is found. This measures the total rate of distortion of turbulent fluid elements-including sweeping, nonlinear distortion, and wave propagation.

Matthaeus, W. H.; Osman, K. T. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, DE (United States); Dasso, S. [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA) and Departamento de Fisica (FCEN-UBA), Buenos Aires (Argentina); Weygand, J. M.; Kivelson, M. G. [Institute for Geophysics and Planetary Physics, University of California, Los Angeles, CA (United States)

2010-09-20

17

Large-scale properties of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Early theoretical work of Parker is presented along with the observational evidence supporting his Archimedes spiral model. Variations present in the interplanetary magnetic field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. Coronal magnetic models are related to the connection between the solar magnetic field and the interplanetary magnetic field. Direct extension of the solar field-magnetic nozzle controversy is discussed along with the coronal magnetic models. Effects of active regions on the interplanetary magnetic field is discussed with particular reference to the evolution of interplanetary sectors. Interplanetary magnetic field magnitude variations are shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 gamma is shown to closely parallel sunspot number. The sun's polar field influence on the interplanetary field and alternative views of the magnetic field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discussed.

Schatten, K. H.

1972-01-01

18

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

19

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided and are continuing to provide 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 are observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions.

Kenneth W. Behannon

1978-01-01

20

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

21

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

22

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

23

A survey of long term interplanetary magnetic field variations  

NASA Technical Reports Server (NTRS)

Interplanetary magnetic field data from 10 IMP, AIMP, and HEOS spacecraft were merged into a composite data set spanning 1963 to 1974. A consideration of the mutual consistency of the individual data sets reveals agreement typically to within 0.2 gamma. Composite data set analysis reveals: (1) whereas the yearly averaged magnitudes of all field vectors show virtually no solar cycle variation, the yearly averaged magnitudes of positive- and negative-polarity field vectors show separate solar cycle variations, consistent with variations in the average azimuthal angles of positive- and negative-polarity field vectors, (2) there is no heliolatitude dependence of long time average field magnitudes, (3) field vectors parallel to the earth-sun line are on the average 1 gamma less in magnitude than field vectors perpendicular to this line, and (4) the heliolatitude-dependent dominant polarity effect exhibits a complex sign reversal in the 1968 to 1971 period and a measure of symmetry in 1972 to 1974 not found in earlier data.

King, J. H.

1975-01-01

24

The regular interplanetary magnetic field during the 1980s  

NASA Technical Reports Server (NTRS)

The regular magnetic field in the interplanetary space for 1980-1990 is calculated using the results of the Hoeksema-Zhao model for the radial magnetic field on the source surface. The unsteady radial component gives birth to the latitudinal and longitudinal components which could be of importance for, e.g., the galactic cosmic ray modulation.

Kalinin, M. S.; Krainev, M. B.

1995-01-01

25

Interplanetary magnetic field effects on high latitude ionospheric convection  

NASA Technical Reports Server (NTRS)

Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

Heelis, R. A.

1985-01-01

26

A model of interplanetary and coronal magnetic fields  

Microsoft Academic Search

A model of the large-scale magnetic field structure above the photosphere uses a Green's function solution to Maxwell's equations. Sources for the magnetic field are related to the observed photospheric field and to the field computed at a ‘source’ surface about 0.6 R? above the photosphere. The large-scale interplanetary magnetic field sector pattern is related to the field pattern at

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

1969-01-01

27

SIGNATURES OF MAGNETIC RECONNECTION AT BOUNDARIES OF INTERPLANETARY SMALL-SCALE MAGNETIC FLUX ROPES  

SciTech Connect

The interaction between interplanetary small-scale magnetic flux ropes and the magnetic field in the ambient solar wind is an important topic in the understanding of the evolution of magnetic structures in the heliosphere. Through a survey of 125 previously reported small flux ropes from 1995 to 2005, we find that 44 of them reveal clear signatures of Alfvenic fluctuations and thus classify them as Alfven wave trains rather than flux ropes. Signatures of magnetic reconnection, generally including a plasma jet of {approx}30 km s{sup -1} within a magnetic field rotational region, are clearly present at boundaries of about 42% of the flux ropes and 14% of the wave trains. The reconnection exhausts are often observed to show a local increase in the proton temperature, density, and plasma beta. About 66% of the reconnection events at flux rope boundaries are associated with a magnetic field shear angle larger than 90{sup 0} and 73% of them reveal a decrease of 20% or more in the magnetic field magnitude, suggesting a dominance of anti-parallel reconnection at flux rope boundaries. The occurrence rate of magnetic reconnection at flux rope boundaries through the years 1995-2005 is also investigated and we find that it is relatively low around the solar maximum and much higher when approaching solar minima. The average magnetic field depression and shear angle for reconnection events at flux rope boundaries also reveal a similar trend from 1995 to 2005. Our results demonstrate for the first time that boundaries of a substantial fraction of small-scale flux ropes have properties similar to those of magnetic clouds, in the sense that both of them exhibit signatures of magnetic reconnection. The observed reconnection signatures could be related either to the formation of small flux ropes or to the interaction between flux ropes and the interplanetary magnetic fields.

Tian Hui; Yao Shuo; Zong Qiugang; Qi Yu [School of Earth and Space Sciences, Peking University, 100871 Beijing (China); He Jiansen, E-mail: tianhui924@pku.edu.c [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany)

2010-09-01

28

The interplanetary magnetic structure that guides solar relativistic particles  

NASA Astrophysics Data System (ADS)

Context. Relating in-situ measurements of relativistic solar particles to their parent activity in the corona requires understanding the magnetic structures that guide them from their acceleration site to the Earth. Relativistic particle events are observed at times of high solar activity, when transient magnetic structures such as interplanetary coronal mass ejections (ICMEs) often shape the interplanetary magnetic field (IMF). They may introduce interplanetary paths that are longer than nominal, and magnetic connections rooted far from the nominal Parker spiral. Aims: We present a detailed study of the IMF configurations during ten relativistic solar particle events of the 23rd activity cycle to elucidate the actual IMF configuration that guides the particles to the Earth, where they are measured by neutron monitors. Methods: We used magnetic field (MAG) and plasma parameter measurements (SWEPAM) from the ACE spacecraft and determined the interplanetary path lengths of energetic particles through a modified version of the velocity dispersion analysis based on energetic particle measurements with SoHO/ERNE. Results: We find that the majority (7/10) of the events is detected in the vicinity of an ICME. Their interplanetary path lengths are found to be longer (1.5-2.6 AU) than those of the two events propagating in the slow solar wind (1.3 AU). The longest apparent path length is found in an event within the fast solar wind, probably caused by enhanced pitch angle scattering. The derived path lengths imply that the first energetic and relativistic protons are released at the Sun at the same time as electron beam emitting type III radio bursts. Conclusions: The timing of the first high-energy particle arrival on Earth is mainly determined by the type of IMF in which the particles propagate. Initial arrival times are as expected from Parker's model in the slow solar wind, and significantly longer in or near transient structures such as ICMEs.

Masson, S.; Démoulin, P.; Dasso, S.; Klein, K.-L.

2012-02-01

29

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

30

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

31

Interplanetary magnetic clouds at 1 AU  

Microsoft Academic Search

Magnetic clouds are defined as regions;with a radial dimension roughly-equal0.25 AU (at 1 AU) in which the magnetic field strength is high and the magnetic field direction changes appreciably by means of rotation of one component of B> nearly parallel to a plane. The magnetic field geometry in such a magnetic cloud is consistent with that of a magnetic loop,

L. W. Klein; L. F. Burlaga

1982-01-01

32

Profile of an Average Magnetic Cloud at 1 au for the Quiet Solar Phase: Wind Observations  

Microsoft Academic Search

Using WIND magnetic field (MFI) and plasma (SWE) data, an `average' profile of an interplanetary magnetic cloud was developed in terms of five physical (scalar) quantities based on appropriately selected individual clouds. The period of study was from early 1995 to late in 1998, primarily during the quiet part of a solar cycle. The physical quantities are: magnetic field magnitude,

R. P. Lepping; D. B. Berdichevsky; A. Szabo; C. Arqueros; A. J. Lazarus

2003-01-01

33

Studies of the interplanetary magnetic field: IMP's to Voyager  

NASA Technical Reports Server (NTRS)

During the last two decades, spacecraft projects and individual experiments for which Frank McDonald was a leader have contributed very significantly to the current understanding of the structure of interplanetary space and the correlation between solar and interplanetary disturbances. Studies on the IMP, HELIOS, and Pioneer spin-stabilized spacecraft and the larger attitude-stabilized Voyager spacecraft have provided data sets from which the modern view of the heliosphere has evolved. That concept in which the inner solar system is shown to be dominated by individual streams associated with specific source regions on the Sun is illustrated. As these high-speed streams overtake the preexisting solar plasma, they coalesce and modify the characteristics so that at larger heliocentric distances, these disturbances appear as radially propagating concentric shells of compressed magnetic fields and enhanced fluctuations

Ness, Norman F.

1987-01-01

34

Magnetic Reconnection in the Interior of Interplanetary Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

Recent in situ observations of interplanetary coronal mass ejections (ICMEs) found signatures of reconnection exhausts in their interior or trailing edge. Whereas reconnection on the leading edge of an ICME would indicate an interaction with the coronal or interplanetary environment, this result suggests that the internal magnetic field reconnects with itself. In light of this data, we consider the stability properties of flux ropes first developed in the context of astrophysics, then further elaborated upon in the context of reversed field pinches (RFPs). It was shown that the lowest energy state of a flux rope corresponds to ?×B=?B with ? a constant, the so-called Taylor state. Variations from this state will result in the magnetic field trying to reorient itself into the Taylor state solution, subject to the constraints that the toroidal flux and magnetic helicity are invariant. In reversed field pinches, this relaxation is mediated by the reconnection of the magnetic field, resulting in a sawtooth crash. If we likewise treat the ICME as a flux rope, any deviation from the Taylor state will result in reconnection within the interior of the flux tube, in agreement with the observations by Gosling et al. Such a departure from the Taylor state takes place as the flux tube cross section expands in the latitudinal direction, as seen in magnetohydrodynamic (MHD) simulations of flux tubes propagating through the interplanetary medium. We show analytically that this elongation results in a state which is no longer in the minimum energy Taylor state. We then present magnetohydrodynamic simulations of an elongated flux tube which has evolved away from the Taylor state and show that reconnection at many surfaces produces a complex stochastic magnetic field as the system evolves back to a minimum energy state configuration.

Fermo, R. L.; Opher, M.; Drake, J. F.

2014-07-01

35

The Interplanetary Magnetic Field and Solar Wind Driven Magnetospheric Reconfiguration  

E-print Network

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

Eugene Savov

2003-01-02

36

Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study  

NASA Technical Reports Server (NTRS)

The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the 2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

Szabo, A.; Koval, A.; Merka, J.; Narock, T.

2011-01-01

37

Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study  

NASA Technical Reports Server (NTRS)

The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions . The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

Szabo, A.; Koval, A.; Merka, J.; Narock, T.

2010-01-01

38

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

39

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

Microsoft Academic Search

An observed influence of the interplanetary magnetic-sector structure on the geomagnetic variations in the polar cap appears to be due to the component of the interplanetary magnetic field near the ecliptic perpendicular to the earth-sun direction. This suggests that the observed effect on the ground originates in the front of the magnetosphere. A clear correspondence between the sector polarity of

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

1972-01-01

40

Dayside convection and auroral morphology during an interval of northward interplanetary magnetic eld  

E-print Network

Dayside convection and auroral morphology during an interval of northward interplanetary magnetic and ionospheric convection during an interval when the interplanetary magnetic ®eld (IMF) had predominantly radar. For an interval of IMF By 0 nT, these convection ¯ow measurements suggest the presence

Boyer, Edmond

41

Radial and latitudinal variations of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

This paper presents observations of the radial and latitudinal variations of the interplanetary magnetic field measured by the Voyager 1 (V1) and Voyager 2 (V2) spacecraft from mid-1977 to mid-1985. Observations of the radial variation of the large-scale magnetic field strength in the ecliptic agree with the predictions of Parker's (1958, 1963) model when temporal variations in the magnetic field and bulk speed are taken into account. The latitudinal variation of the magnetic field observed by V1 is in agreement with the predictions of Parker's model to first approximation. The magnetic field strength at higher latitudes is somewhat lower than expected on the basis of observations made in the ecliptic, but this could be due to an increase in bulk speed and/or a decrease of solar magnetic field strength with latitude. Fluctuations in the strength of the magnetic field are small compared to the large-scale field itself, and they decrease in amplitude with increasing distance approximately as R exp -1/4 . Fluctuations in the components are relatively large, and they make a significant contribution to the mean field that is not described by Parker's model.

Klein, Larry W.; Burlaga, L. F.; Ness, N. F.

1987-01-01

42

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

43

Helioseismology with Seismometers: II Coherence with the Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

Since the discovery of seismic "hum'' in 1998 unexpected lines have been observed in terrestrial seismology.In this talk we give further evidence that these lines originate as normal modes of the Sun. Frequencies observed in terrestrial seismic and geomagnetic data are often split by multiples of a cycle/day and, unexpectedly, by multiples of one-half cycle per sidereal day.There is coherence between the interplanetary magnetic field (IMF) at ACE (located at L_1) and terrestrial geomagnetic and seismic data. There are slight frequency offsets between colocated geomagnetic and seismic data similar to those observed in normal modes excited by earthquakes. These have been attributed to dispersion from large-scale structure in the Earth.Both the splitting and coherence with the IMF give further confirmation that solar modes propagatethrough interplanetary space and are sufficiently strong to literally shake the Earth. This gives another method to detect and possibly identify solar gravity and low--frequency P-modes.

Thomson, David J.; Vernon, Frank L.

2015-04-01

44

Interplanetary magnetic field dependence of the suprathermal energetic neutral atoms originated in subsolar magnetopause  

NASA Astrophysics Data System (ADS)

Using energetic neutral atom (ENA) emission observations of the subsolar magnetopause measured by the Interstellar Boundary Explorer (IBEX), we study the correlation between the upstream interplanetary magnetic field (IMF) conditions and the spectral index of the source ion population. Our ENA data set includes hour-averaged ENA measurements at energies between ˜0.5 and ˜6 keV obtained by the IBEX High Energy ENA imager from January 2009 to May 2011. Under the condition of quiet geomagnetic activity (SYM-H index >-20 nT), we find that the shallower spectra in the suprathermal tail of the ion population of the subsolar magnetopause is weakly correlated (correlation coefficient of -0.30) with the shock angle of the Earth's bow shock, but not correlated with parameters related to magnetic reconnection (i.e., elevation and clock angle of the interplanetary magnetic field orientation). The observed correlation suggests suprathermal ion energization from diffusive shock acceleration and thus that the suprathermal ions in the subsolar magnetopause are of shocked solar wind origin. We also argue that the roles of magnetospheric ion leakage or ion acceleration by magnetic reconnection are reduced in the magnetopause emissions compared to shock acceleration processes.

Ogasawara, K.; Dayeh, M. A.; Funsten, H. O.; Fuselier, S. A.; Livadiotis, G.; McComas, D. J.

2015-02-01

45

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

46

Evidence linking coronal mass ejections with interplanetary magnetic clouds  

NASA Technical Reports Server (NTRS)

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients.

Wilson, R. M.; Hildner, E.

1983-01-01

47

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

48

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

49

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

50

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

51

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

52

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

53

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

54

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

55

Microstructure of the interplanetary magnetic field near 4 and 5 AU  

Microsoft Academic Search

Interplanetary magnetic field fluctuations near 4 and 5 AU are investigated on the basis of Pioneer 10 and 11 vector magnetic field measurements in order to identify extant wave modes and propagation directions as functions of frequency in the range 0.00004 to 0.009 Hz. Analysis of the approximately 500 spectral matrices as functions of frequency obtained from each spacecraft indicates

G. D. Parker

1980-01-01

56

Interplanetary magnetic field control of the Mars bow shock - Evidence for Venuslike interaction  

NASA Technical Reports Server (NTRS)

The Mars bow shock location and shape have been determined by examining the Phobos spacecraft magnetometer data. Observations show that the position of the terminator bow shock varies with interplanetary magnetic field orientation in the same way as at Venus. The shock is farthest from Mars in the direction of the interplanetary electric field, consistent with the idea that mass loading plays an important role in the solar wind interaction with Mars. The shock cross section at the terminator plane is asymmetric and is controlled by the interplanetary magnetic field. The shock is farther from Mars during solar maximum. Thus the solar wind interaction with Mars appears to be Venuslike, with a magnetic moment too small to affect significantly the solar wind interaction.

Zhang, T. L.; Schwingenschuh, K.; Lichtenegger, H.; Riedler, W.; Russell, C. T.

1991-01-01

57

Interplanetary magnetic field control of the Mars bow shock: Evidence for Venuslike interaction  

SciTech Connect

The Mars bow shock location and shape have been determined by examining the PHOBOS spacecraft magnetometer data. Observations show that the position of the terminator bow shock varies with interplanetary magnetic field orientation in the same way as at Venus. The shock is farthest from Mars in the direction of the interplanetary electric field, consistent with the idea that mass loading plays an important role in the solar wind interaction with Mars. The authors also find that the shock cross section at the terminator plane is asymmetric and is controlled by the interplanetary magnetic field as expected from the asymmetric propagation velocity of the fast magnetosonic wave. Comparing with earlier mission data, they show that the Mars shock location varies with solar activity. The shock is farther from Mars during solar maximum. Thus the solar wind interaction with Mars appears to be Venuslike, with a magnetic moment too small to affect significantly the solar wind interaction.

Zhang, T.L.; Schwingenschuh, K.; Lichtenegger, H.; Riedler, W. (Space Research Inst. of the Austrian Academy, Graz (Austria)); Russell, C.T.; Luhmann, J.G. (Univ. of California, Los Angeles (USA))

1991-07-01

58

Interplanetary Magnetic Field Line Mixing Deduced from Impulsive Solar Flare Particles.  

PubMed

We have studied fine-scale temporal variations in the arrival profiles of approximately 20 keV nucleon-1 to approximately 2 MeV nucleon-1 ions from impulsive solar flares using instrumentation on board the Advanced Composition Explorer spacecraft at 1 AU between 1997 November and 1999 July. The particle events often had short-timescale ( approximately 3 hr) variations in their intensity that occurred simultaneously across all energies and were generally not in coincidence with any local magnetic field or plasma signature. These features appear to be caused by the convection of magnetic flux tubes past the observer that are alternately filled and devoid of flare ions even though they had a common flare source at the Sun. Thus, we have used the particles to study the mixing of the interplanetary magnetic field that is due to random walk. We deduce an average timescale of 3.2 hr for these features, which corresponds to a length of approximately 0.03 AU. PMID:10702137

Mazur; Mason; Dwyer; Giacalone; Jokipii; Stone

2000-03-20

59

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

60

Interplanetary medium data book  

NASA Technical Reports Server (NTRS)

Unresolved questions on the physics of solar wind and its effects on magnetospheric processes and cosmic ray propagation were addressed with hourly averaged interplanetary plasma and magnetic field data. This composite data set is described with its content and extent, sources, limits of validity, and the mutual consistency studies and normalizations to which the input data were subjected. Hourly averaged parameters were presented in the form of digital listings and 27-day plots. The listings are contained in a separately bound appendix.

King, J. H.

1977-01-01

61

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

Microsoft Academic Search

The energetic charged particle, interplanetary magnetic field, and plasma characteristics of the `Bastille Day' shock and\\u000a ejecta\\/magnetic cloud events at 1 AU occurring over the days 14–16 July 2000 are described. Profiles of MeV (WIND\\/LEMT) energetic\\u000a ions help to organize the overall sequence of events from the solar source to 1 AU. Stressed are analyses of an outstanding\\u000a magnetic cloud (MC2) starting

R. P. Lepping; D. B. Berdichevsky; L. F. Burlaga; A. J. Lazarus; J. Kasper; M. D. Desch; C.-C. Wu; D. V. Reames; H. J. Singer; C. W. Smith; K. L. Ackerson

2001-01-01

62

An interplanetary magnetic field enhancement observed by five spacecraft: Deducing the magnetic structure, size and mass  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) were discovered almost 30 years ago in the PVO magnetic-field records and attributed to the interaction between solar wind and dust particles from comets or asteroids, but the physics of this interaction remained obscure. Our current understanding is that IFEs result from collisions of small interplanetary bodies that produce electrically charged nanometer-scale dust particles possibly enhanced by tribo-electric charging in the collision. These charged dust particles in turn interact with the magnetized solar wind. Momentum is transferred from the solar wind to the dust cloud via the collective effect of the formation of a magnetic barrier. This momentum transfer accelerates the particles to near the solar wind speed and moves the dust outward through the solar gravitational potential well. Multi-spacecraft observations can help us to determine the speed of the IFE and the orientation of the current sheet. They enable us to reconstruct the pressure profile of an IFE in three dimensions and estimate the mass contained in the IFE. We have done these reconstructions with an IFE observed on March 3, 2011 with Wind, ACE, ARTEMIS P1 and P2 and Geotail. We find that the magnetic field near the center of the IFE is highly twisted indicating a complicated magnetic topology as expected in a plasma-charged dust interaction. The magnetic field and plasma properties during this event distinguish it from a typical flux rope. Based on the statistical results obtained at 1 AU and the assumption that all the IFEs are self-similar, we find that this IFE has a radial scale length several times longer than the cross flow radius and contains a mass of about 108 kg. The rates of collisions expected for objects of this size are consistent with the observed rates of these disturbances.

Lai, H.; Russell, C. T.; Delzanno, G.; Angelopoulos, V.

2012-12-01

63

Statistical study of low-frequency magnetic field fluctuations near Venus under the different interplanetary magnetic field orientations  

Microsoft Academic Search

The magnetic field fluctuations near Venus are investigated in the frequency range 0.03–0.3 Hz on the basis of the measurements observed by Venus Express from April 2006 to December 2008. The data are sorted by the angle between interplanetary magnetic field (IMF) and solar wind flow. The spatial distributions of fluctuation properties under the different IMF orientations are presented and

J. Du; T. L. Zhang; W. Baumjohann; C. Wang; M. Volwerk; Z. Vörös; L. Guicking

2010-01-01

64

Properties of interplanetary magnetic sector boundaries based on electron heat-flux flow directions  

NASA Astrophysics Data System (ADS)

We have used the solar wind electron heat flux flow directions to determine the interplanetary magnetic field polarities for the ISEE 3 period from 1978 to 1982. This technique assumes that the heat flux electrons flow away from the Sun along magnetic field lines. It provides the field polarities independently of the field directions. The resulting distribution of sector durations and the changes in that distribution with solar activity cycle are presented for four 1-year periods. The large-scale sectors expected from extrapolation of the Stanford source surface maps are present along with a population of small-scale sectors with a peak in the time range of 9 hour to 1 day. About half the small-scale sectors contain bidirectional electron (BDE) flows, suggesting their origins in coronal mass ejections. We also examine cases of false polarities, in which the directions of the fields imply polarities opposite to those determined from the heat-flux directions. These constitute only 6 to 8% of all the hourly averages of the data. The majority (78%) of these false polarity regions were not associated with BDEs, and 75% were of only 1 or 2 hour durations. False polarity regions tended to lie nearly orthogonal to the spiral field angles and at relatively high latitudinal angles. While multiple (>=3 in 24 hours) current sheet crossings are common, we find no cases consistent with a wavy current sheet.

Kahler, S.; Crooker, N. U.; Gosling, J. T.

1998-09-01

65

The Earth's Response to the Interplanetary Small-scale Magnetic Flux Ropes  

NASA Astrophysics Data System (ADS)

We analyze interplanetary small-scale magnetic flux ropes (ISMFRs) observed by multi-satellites propagating from 1 AU to the Earth to understand their geomagnetic effectiveness. We use ACE, WIND, GEOTAIL, CLUSTER, THEMIS, and several geosynchronous spacecraft. Using published criteria for identification of ISMFR, we selected 15 events during 2007-2008. The duration of these events average about 90 mins. We analyzed each event using both in situ and ground data and found that significant perturbations in the inner magnetosphere, like substorms and enhanced ULF wave activity, are often triggered by ISMFR. Combined with the ISMFR database (1995-2005) from previous work, 97 ISMFRs are identified. Of these 49 ISMFR have signatures of magnetic reconnection (MR) at one or two of their boundaries based on the 3-s WIND data. Furthermore, based on the 1-min AE/AL indices and time-shifted IMF data from OMNI website, substorms were triggered during more than half of these flux ropes. The superposed epoch analysis shows that the solar wind electric field (Ey) is the most correlated parameter of the flux ropes with the Earth's geomagnetic activity. It also indicates that the geomagnetic field responds differently to the events with different polarity sequences (i.e., ISMFR with north then south turning compared to south then north turning).

Zhang, X.; Moldwin, M.; Cartwright, M. L.

2011-12-01

66

Polar cap bifurcation during steady-state northward interplanetary magnetic field with |BY| ~ BZ  

Microsoft Academic Search

In this paper, for steady-state northward interplanetary magnetic field (IMF) with |BY| ~ BZ, we describe a new merging sequence that results in polar cap bifurcation and accompanying paired ``exchange cells'' in the ionospheric convection pattern. Although the IMF is northward, it reconnects with the closed geomagnetic field on the dayside high-latitude magnetopause, creating two types of open geomagnetic field

Masakazu Watanabe; George J. Sofko; Dieter A. André; Takashi Tanaka; Marc R. Hairston

2004-01-01

67

Polar cap bifurcation during steady-state northward interplanetary magnetic field with ?BY? ? BZ  

Microsoft Academic Search

In this paper, for steady-state northward interplanetary magnetic field (IMF) with ?BY? ? BZ, we describe a new merging sequence that results in polar cap bifurcation and accompanying paired “exchange cells” in the ionospheric convection pattern. Although the IMF is northward, it reconnects with the closed geomagnetic field on the dayside high-latitude magnetopause, creating two types of open geomagnetic field

Masakazu Watanabe; George J. Sofko; Dieter A. André; Takashi Tanaka; Marc R. Hairston

2004-01-01

68

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.

69

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

70

Saturation of transpolar potential for large Y component interplanetary magnetic field  

Microsoft Academic Search

This study examines the response of the transpolar potential to a large Y component interplanetary magnetic field (IMF By). The transpolar potential responds nonlinearly and saturates for large IMF By in the Lyon-Fedder-Mobarry (LFM) global MHD simulation, just as it does for large southward IMF (?Bz). Data from Defense Meteorological Satellite Program (DMSP) satellites and Assimilative Mapping of Ionospheric Electrodynamics

E. J. Mitchell; R. E. Lopez; R. J. Bruntz; M. Wiltberger; J. G. Lyon; R. C. Allen; S. J. Cockrell; P. L. Whittlesey

2010-01-01

71

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

72

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.

73

Magnetic Flux Circulation During Dawn-Dusk Oriented Interplanetary Magnetic Field  

NASA Technical Reports Server (NTRS)

Magnetic flux circulation is a primary mode of energy transfer from the solar wind into the ionosphere and inner magnetosphere. For southward interplanetary magnetic field (IMF), magnetic flux circulation is described by the Dungey cycle (dayside merging, night side reconnection, and magnetospheric convection), and both the ionosphere and inner magnetosphere receive energy. For dawn-dusk oriented IMF, magnetic flux circulation is not well understood, and the inner magnetosphere does not receive energy. Several models have been suggested for possible reconnection patterns; the general pattern is: dayside merging; reconnection on the dayside or along the dawn/dusk regions; and, return flow on dayside only. These models are consistent with the lack of energy in the inner magnetosphere. We will present evidence that the Dungey cycle does not explain the energy transfer during dawn-dusk oriented IMF. We will also present evidence of how magnetic flux does circulate during dawn-dusk oriented IMF, specifically how the magnetic flux reconnects and circulates back.

Mitchell, E. J.; Lopez, R. E.; Fok, M.-C.; Deng, Y.; Wiltberger, M.; Lyon, J.

2010-01-01

74

Response of ionosphere and thermosphere during radial interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The configurations of ionosphere and thermosphere have been investigated by using high-resolution measurements of CHAMP satellite. During the period IMF By and Bz components are weak and Bx keeps pointing to the Earth for almost 10 hours. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average during the interest period. The CPCP (cross polar cap potential) output by AMIE and calculated from DMSP observations have average values of 15-20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the dayside and nightside. In the south pole FACs diminish in intensity with magnitudes below 0.25 µA/m2, the plasma convection retains its quiet time two cell flow pattern, and the air density is quiet low. However, there are obvious activities in the north cusp FACs. One pair of FACs emerges in the north cusp region, which shows opposite polarities to DPY FACs. The new type of currents is accompanied by sunward plasma flow channels. These ionospheric features might be manifestations of the magnetic reconnection processes occurring in the north magnetospheric flanks. The enhanced ionospheric current systems have deposited large amount of energies into the thermosphere, causing enhanced air densities in the cusp region, which subsequently propagate equatorward both on the dayside and nightside. Although the radial IMF is considered as geomagnetic quiet condition, the present study has demonstrated for the first time there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the polar cusp region.

Wang, Hui; Luehr, Hermann; Shue, Jihong

2014-05-01

75

Magnetic field directional discontinuities. 2: Characteristics between 0.46 and 1.0 AU. [interplanetary magnetic fields  

NASA Technical Reports Server (NTRS)

The characteristics of directional discontinuities (DD's) in the interplanetary magnetic field are studied using data from the Mariner 10 primary mission between 1.0 and 0.46 AU. Statistical and visual survey methods for DD identification resulted in a total of 644 events. Two methods were used to estimate the ratio of the number of tangential discontinuities (TD's) to the number of rotational discontinuities (RD's). Both methods show that the ratio of TD's to RD's varied with time and decreased with decreasing radial distance. A decrease in average discontinuity thickness of approx. 40 percent was found between 1.0 and 0.72 AU and approx. 54 percent between 1.0 and 0.46 AU, independent of type (TD or RD). This decrease in thickness for decreasing r is in qualitative agreement with Pioneer 10 observations between 1 and 5 AU. When the individual DD thickness are normalized with respect to the estimated local proton gyroradius (RA sub L), the average thickness at the three locations is nearly constant, 43 + or - 6 R sub L. This also holds true for both RD's and TD's separately. Statistical distributions of other properties, such as normal components and discontinuity plane angles, are presented.

Lepping, R. P.; Benhannon, K. W.

1980-01-01

76

CME-related dimmings as a signature of interplanetary magnetic cloud footpoints  

NASA Astrophysics Data System (ADS)

Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyse several events, flares and coronal mass ejections (CMEs), for which we can find their interplanetary counterpart. We combine SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model the associated clouds and compute their magnetic flux using in situ observations. We find that the magnetic fluxes of the dimmings and magnetic clouds are compatible in some cases; though this is not the case for large-scale events and eruptions that occur in regions that are not isolated from other flux concentrations. We conclude that the interpretation of dimmings requires a deeper analysis of the global magnetic field configuration, since at least a fraction of the dimmed regions could be formed by reconnection between the erupting field and the surrounding magnetic structures.

Mandrini, Cristina H.; Soledad Nakwacki, Ms Maria; Attrill, Gemma; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Demoulin, Pascal

77

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

78

Dense and stagnant ions in the low-latitude boundary region under northward interplanetary magnetic field  

Microsoft Academic Search

The ion behavior in the low-latitude boundary region is studied based on Geotail data accumulated over several years, toward understanding the formation mechanism of the cold-dense plasma sheet under prolonged northward interplanetary magnetic field (IMF). A statistical survey shows that, during extended northward IMF, (1) dense magnetosheath-like ions appear far more often, especially on the flanks, (2) the dense ions

H. Hasegawa; M. Fujimoto; Y. Saito; T. Mukai

2004-01-01

79

Interplanetary magnetic field power spectra: Mean field radial or perpendicular to radial  

Microsoft Academic Search

Power spectral, correlation, and coherency analyses have been made for selected periods of Pioneer 6 interplanetary magnetic field data for the frequency range of 5 x 10⁻⁴ to 1.6 x 10⁻² Hz. The periods are chosen for times when the mean field was either radial or perpendicular to the heliocentric radius. At such times, some of the interpretive ambiguities which

James W. Sari; George C. Valley

1976-01-01

80

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

81

Are Polar Field Magnetic Flux Concentrations Responsible for Missing Interplanetary Flux?  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) simulations are now routinely used to produce models of the solar corona and inner heliosphere for specific time periods. These models typically use magnetic maps of the photospheric magnetic field built up over a solar rotation, available from a number of ground-based and space-based solar observatories. The line-of-sight field at the Sun's poles is poorly observed, and the polar fields in these maps are filled with a variety of interpolation/extrapolation techniques. These models have been found to frequently underestimate the interplanetary magnetic flux (Riley et al., 2012, in press, Stevens et al., 2012, in press) near the minimum part of the cycle unless mitigating correction factors are applied. Hinode SOT observations indicate that strong concentrations of magnetic flux may be present at the poles (Tsuneta et al. 2008). The ADAPT flux evolution model (Arge et al. 2010) also predicts the appearance of such concentrations. In this paper, we explore the possibility that these flux concentrations may account for a significant amount of magnetic flux and alleviate discrepancies in interplanetary magnetic flux predictions. Research supported by AFOSR, NASA, and NSF.

Linker, Jon A.; Downs, C.; Mikic, Z.; Riley, P.; Henney, C. J.; Arge, C. N.

2012-05-01

82

Magnetic Field-line Twist and Length Distributions inside Interplanetary Magnetic Flux Ropes  

NASA Astrophysics Data System (ADS)

?We report on the detailed and systematic study of field-line twist and length distributions within magnetic flux ropes embedded in Interplanetary Coronal Mass Ejections (ICMEs). The Grad-Shafranov reconstruction method is utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model and the commonly known Lundquist (linear force-free) model to reveal the close relation between the field-line twist and length in cylindrical flux ropes, based on in-situ spacecraft magnetic field and plasma measurements. In particular, we utilize energetic electron burst observations at 1 AU together with associated type III radio emissions detected by the Wind spacecraft to provide unique measurements of magnetic field-line lengths within selected ICME events. These direct measurements are compared with flux-rope model calculations to help assess the fidelity of different models and to provide diagnostics of internal structures. We show that our initial analysis of field-line twist indicates clear deviation from the Lundquist model, but better consistency with the Gold-Hoyle model. By using the different flux-rope models, we conclude that the in-situ direct measurements of field-line lengths are consistent with a flux-rope structure with spiral field lines of constant and low twist, largely different from that of the Lundquist model, especially for relatively large-scale flux ropes. We will also discuss the implications of our analysis of flux-rope structures on the origination and evolution processes in their corresponding solar source regions.

Hu, Qiang; Qiu, Jiong; Krucker, Sam

2015-04-01

83

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

84

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

85

The interaction of a very large interplanetary magnetic cloud with the magnetosphere and with cosmic rays  

NASA Technical Reports Server (NTRS)

The observation of one of the largest magnetic clouds ever observed at a distance of 1 AU, with a diameter of greater than about 0.4 AU, is reported. The cloud is shown to be almost unchanged structurally by interaction with the earth bow shock. The first observations are reported of an auroral activity response to the passage of a magnetic cloud, with a nearly immediate increase in auroral activity when the IMF theta(B) angle reversed polarity to negative near the cloud center. The results provide strong evidence that turbulent magnetic fields behind interplanetary shocks are a possible cause of Forbush decreases, but contest the idea that relatively smooth, strong fields in clouds are a cause of such decreases. The cloud field modeling supports the existence of magnetic force-free fields in describing cloud structure.

Lepping, R. P.; Burlaga, L. F.; Ogilvie, K. W.; Tsurutani, B. T.; Lazarus, A. J.

1991-01-01

86

Mercury's plasma belt under different Interplanetary Magnetic Field: hybrid simulations results compared to in-situ measurements  

NASA Astrophysics Data System (ADS)

The presence of plasma belt and trapped charged particles region in the Mercury's inner magnetosphere has been questionable due to small dimensions of the magnetosphere of Mercury compared to Earth, where these regions are formed. However, early and recent numerical simulations of the solar wind interaction with Mercury's magnetic field suggested that a similar structure, consisting rather of quasi-trapped charged particles could be found also in the vicinity of Mercury. These simulated results have been recently confirmed by MESSENGER in-situ observations. We present a detailed analysis of the plasma belt structure of quasi-trapped plasma near the Mercury's surface and its characteristics and behaviour under different orientations of the interplanetary magnetic field. The plasma belt region is constantly supplied with solar wind protons via magnetospheric flanks and tail current sheet region. Protons inside the plasma belt region are quasi-trapped in the magnetic field of Mercury and perform westward drift along the planet. This region is well separated by a magnetic shell and has higher average temperatures and lower bulk proton current densities than surrounding area. On the day side the population exhibits loss cone distribution function matching the theoretical loss cone angle. Simulations results are also compared to in-situ measurements acquired by MESSENGER MAG and FIPS instruments.

Travnicek, Pavel M.; Hercik, David; Schriver, David; Hellinger, Petr; Anderson, Brian J.; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H.

2013-04-01

87

Contributions to the Fourth Solar Wind Conference. [interplanetary magnetic fields and medium  

NASA Technical Reports Server (NTRS)

Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed.

Acuna, M. H.; Behannon, K. W.; Burlaga, L. F.; Lepping, R.; Ness, N.; Ogilvie, K.; Pizzo, J.

1979-01-01

88

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

89

Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere  

NASA Technical Reports Server (NTRS)

We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere.

Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J.

2002-01-01

90

Interplanetary magnetic field and solar cycle dependence of Northern Hemisphere F region joule heating  

NASA Astrophysics Data System (ADS)

Joule heating in the ionosphere takes place through collisions between ions and neutrals. Statistical maps of F region Joule heating in the Northern Hemisphere polar ionosphere are derived from satellite measurements of thermospheric wind and radar measurements of ionospheric ion convection. Persistent mesoscale heating is observed near postnoon and postmidnight magnetic local time and centered around 70° magnetic latitude in regions of strong relative ion and neutral drift. The magnitude of the Joule heating is found to be largest during solar maximum and for a southeast oriented interplanetary magnetic field. These conditions are consistent with stronger ion convection producing a larger relative flow between ions and neutrals. The global-scale Joule heating maps quantify persistent (in location) regions of heating that may be used to provide a broader context compared to small-scale studies of the coupling between the thermosphere and ionosphere.

Bjoland, L. M.; Chen, X.; Jin, Y.; Reimer, A. S.; Skjæveland, Å.; Wessel, M. R.; Burchill, J. K.; Clausen, L. B. N.; Haaland, S. E.; McWilliams, K. A.

2015-02-01

91

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

92

Analysis of the interplanetary magnetic field observations at different heliocentric distances  

NASA Astrophysics Data System (ADS)

Multi-spacecraft measurements of the interplanetary magnetic field (IMF) from 0.29 AU to 5 AU along the ecliptic plane have demonstrated systematic deviations of the observed IMF strength from the values predicted on the basis of the Parker-like radial extension models (Khabarova, Obridko, 2012). In particular, it was found that the radial IMF component |Br| decreases with a heliocentric distance r with a slope of -5/3 (instead of r-2 expansion law). The current investigation of multi-point observations continues the analysis of the IMF (and, especially, Br) large-scale behaviour, including its latitudinal distribution. Additionally, examples of the mismatches between the expected IMF characteristics and observations at smaller scales are discussed. It is shown that the observed effects may be explained by not complete IMF freezing-in to the solar wind plasma. This research was supported by the Russian Fund of Basic Researches' grants Nos.11-02-00259-a, and 12-02-10008-K. Khabarova Olga, and Obridko Vladimir, 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

Khabarova, Olga

2013-04-01

93

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

94

Multiple-X reconnection at high latitudes under northward interplanetary magnetic field condition  

NASA Astrophysics Data System (ADS)

The stability and quasi-periodic variations of the high latitude reconnection sites are presented by performing global MHD simulation under due northward interplanetary magnetic field (IMF) condition. Numerical results demonstrate that the high latitude reconnection is multiple-x line reconnection, accompanied by the formation of magnetic islands (or plasmoids). Among the multiple reconnection sites, position of the one closest to the cusp seems stable. Whereas, the X-line tail-ward of it moves anti-sunward rapidly after the formation, and a new X-line reforms near its initial location a few minutes later, completing a cycle of the quasi-periodic evolution process. Alfven Mach number near the X-lines is analyzed to reveal the reason for this scenario. Finally, we conclude that the above mentioned model combining different types of reconnection site variations provides reasonable explanations for most observed features concerning the high latitude reconnection.

Sun, T.; Wang, C.

2013-12-01

95

Spatial distribution of large-scale solar magnetic fields and their relation to the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The spatial organization of the observed photospheric magnetic field as well as its relation to the polarity of the IMF have been studied using high resolution magnetograms from the Kitt Peak National Observatory. Systematic patterns in the large scale field are due to contributions from both concentrated flux and more diffuse flux. The polarity of the photospheric field, determined on various spatial scales, correlates with the polarity of the IMF. Analyses based on several spatial scales in the photosphere suggest that new flux in the interplanetary medium is often due to relatively small photospheric features which appear in the photosphere up to one month before they are manifest at the earth.

Levine, R. H.

1979-01-01

96

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

97

Saturn's dayside ultraviolet auroras: Evidence for morphological dependence on the direction of the upstream interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We examine a unique data set from seven Hubble Space Telescope (HST) "visits" that imaged Saturn's northern dayside ultraviolet emissions exhibiting usual circumpolar "auroral oval" morphologies, during which Cassini measured the interplanetary magnetic field (IMF) upstream of Saturn's bow shock over intervals of several hours. The auroras generally consist of a dawn arc extending toward noon centered near ~15° colatitude, together with intermittent patchy forms at ~10° colatitude and poleward thereof, located between noon and dusk. The dawn arc is a persistent feature, but exhibits variations in position, width, and intensity, which have no clear relationship with the concurrent IMF. However, the patchy postnoon auroras are found to relate to the (suitably lagged and averaged) IMF Bz, being present during all four visits with positive Bz and absent during all three visits with negative Bz. The most continuous such forms occur in the case of strongest positive Bz. These results suggest that the postnoon forms are associated with reconnection and open flux production at Saturn's magnetopause, related to the similarly interpreted bifurcated auroral arc structures previously observed in this local time sector in Cassini Ultraviolet Imaging Spectrograph data, whose details remain unresolved in these HST images. One of the intervals with negative IMF Bz however exhibits a prenoon patch of very high latitude emission extending poleward of the dawn arc to the magnetic/spin pole, suggestive of the occurrence of lobe reconnection. Overall, these data provide evidence of significant IMF dependence in the morphology of Saturn's dayside auroras.

Meredith, C. J.; Alexeev, I. I.; Badman, S. V.; Belenkaya, E. S.; Cowley, S. W. H.; Dougherty, M. K.; Kalegaev, V. V.; Lewis, G. R.; Nichols, J. D.

2014-03-01

98

Role of periodic loading-unloading in the magnetotail versus interplanetary magnetic field Bz flipping in the ring current buildup  

Microsoft Academic Search

Introducing kinetic corrections into the to BATSRUS code in the magnetotail region leads to fast reconnection rates observed in kinetic simulations and quasi-periodic loading-unloading cycles in the magnetotail during a long period of steady southward interplanetary magnetic field (IMF) Bz (Kuznetsova et al., 2006, 2007). We use the global MHD code BATSRUS output to drive the Fok Ring Current (FRC)

A. Taktakishvili; M. M. Kuznetsova; M. Hesse; M.-C. Fok; L. Rastätter; M. Maddox; A. Chulaki; G. Tóth; T. I. Gombosi; D. L. De Zeeuw

2008-01-01

99

Interplanetary Magnetic Field Power Spectrum Variations in the Inner Heliosphere: A Wind and MESSENGER Study  

NASA Technical Reports Server (NTRS)

The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the similar observations made by the MESSENGER spacecraft in the inner heliosphere affords an opportunity to compare magnetic field power spectral density variations as a function of radial distance from the Sun under different solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The powe'r spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. Wind and MESSENGER magnetic fluctuations are compared for times when the two spacecraft are close to radial and Parker field alignment. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed.

Szabo, Adam; Koval, A.

2011-01-01

100

Are CME-Related Dimmings Always a Simple Signature of Interplanetary Magnetic Cloud Footpoints?  

NASA Astrophysics Data System (ADS)

Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyze the event, flare, and coronal mass ejection (CME) that occurred in active region 10486 on 28 October 2003. The CME on this day is associated with large-scale dimmings, located on either side of the main flaring region. We combine SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model the associated cloud and compute its magnetic flux using in situ observations from the Magnetometer Instrument and the Solar Wind Electron Proton Alpha Monitor aboard the Advance Composition Explorer. We find that the magnetic fluxes of the dimmings and magnetic cloud are incompatible, in contrast to what has been found in previous studies. We conclude that, in certain cases, especially in large-scale events and eruptions that occur in regions that are not isolated from other flux concentrations, the interpretation of dimmings requires a deeper analysis of the global magnetic configuration, since at least a fraction of the dimmed regions is formed by reconnection between the erupting field and the surrounding magnetic structures.

Mandrini, C. H.; Nakwacki, M. S.; Attrill, G.; van Driel-Gesztelyi, L.; Démoulin, P.; Dasso, S.; Elliott, H.

2007-08-01

101

Characteristics of the association between the interplanetary magnetic field and substorms  

NASA Technical Reports Server (NTRS)

The geomagnetic response to changes in the orientation of the interplanetary magnetic field (IMF) has been investigated for 18 IMF events. These events consisted of clear southward shifts of the IMF when the IMF Bz(GSM) component had been northward for more than two hours. It was found that when the IMF thus shifted southward and remained southward for at least two hours, a magnetospheric substorm always ensued. Several properties of this subsequent geomagnetic activity were determined to be associated with IMF parameters. The amplitude of auroral negative bays was confirmed to be a function of the southward IMF flux preceding the onsets. Auroral bay activity was also observed to cease abruptly coincident with permanent northward recoveries in the IMF. Finally, it was observed that many of the ground expansion onsets were associated with either IMF northward fluctuations or partial northward recoveries, which is interpreted as indicative of the existence of a class of IMF-triggered substorms.

Caan, M. N.; Mcpherron, R. L.; Russell, C. T.

1977-01-01

102

ISEE 3 observations of low-energy proton bidirectional events and their relation to isolated interplanetary magnetic structures  

NASA Technical Reports Server (NTRS)

The paper represents the results of a comprehensive survey of low-energy proton bidirectional anisotropies and associated transient magnetic structures as observed in the 35-1600 keV energy range on ISEE-3 during the last solar maximum. The majority of observed bidirectional flow (BDF) events (more than 70 percent) are associated with isolated magnetic structures which are postulated to be an interplanetary manifestation of coronal mass ejection (CME) events. The observed BDF events can be qualitatively grouped into five classes depending on the field signature of the related magnetic structure and the association (or lack of association) with an interplanetary shock. Concerning the topology of the CME-related magnetic structures, the observations are interpreted as being consistent with a detached bubble, comprising closed loops or tightly wound helices.

Marsden, R. G.; Sanderson, T. R.; Tranquille, C.; Wenzel, K.-P.; Smith, E. J.

1987-01-01

103

Interplanetary flux rope ejected from an X-ray bright point. The smallest magnetic cloud source-region ever observed  

Microsoft Academic Search

Using multi-instrument and multi-wavelength observations (SOHO\\/MDI and EIT, TRACE and Yohkoh\\/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of Wind in situ data, we provide evidences for the smallest event ever observed which links a sigmoid eruption to an interplanetary magnetic cloud (MC). The tiny bipole, which was observed very close to

C. H. Mandrini; S. Pohjolainen; S. Dasso; L. M. Green; P. Démoulin; L. van Driel-Gesztelyi; C. Copperwheat; C. Foley

2005-01-01

104

Magnetospheric convection on the presence of interplanetary magnetic gield B{sub y}: A conceptual model and simulations  

Microsoft Academic Search

Existing observations from ISEE 3 and new observations from Galileo show that when the interplanetary magnetic field (IMF) has a B{sub y} component, a B{sub y} component also develops in the Earth`s magnetotail, but only in those quadrants in which the addition of the newly opened magnetic flux tubes occurs. The presence of B{sub y} on the closed field lines

K. K. Khurana; R. J. Walker; Tatsuki Ogino

1996-01-01

105

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

106

The chain response of the magnetospheric and ground magnetic field to interplanetary shocks  

NASA Astrophysics Data System (ADS)

In response to interplanetary (IP) shocks, magnetic field may decrease/increase (negative/positive response) in nightside magnetosphere, while at high latitudes on the ground it has two-phase bipolar variations: preliminary impulse and main impulse (MI). Using global MHD simulations, we investigate the linkage between the MI phase variation on the ground and the magnetospheric negative response to an IP shock. It is revealed that although the two phenomena occur at largely separated locations, they are physically related and form a response chain. The velocity disturbances near the flanks of the magnetopause cause the magnetic field to decrease, resulting in a dynamo which thus powers the transient field-aligned currents (FACs). These FACs further generate a pair of ionospheric current vortex, leading to MI variations on the ground. Therefore, we report here the intrinsic physically related chain response of the magnetospheric and ground magnetic field to IP shocks, and thus link the magnetospheric sudden impulse (SI) and ground SI together.

Sun, T. R.; Wang, C.; Zhang, J. J.; Pilipenko, V. A.; Wang, Y.; Wang, J. Y.

2015-01-01

107

A global simulation of the magnetosphere with a long tail: No interplanetary magnetic field  

SciTech Connect

A global simulation of the magnetosphere with a long tail ({approximately}1,000 R{sub E}) is performed. A magnetosphere with a neutral sheet is constructed from a dipole field by solar wind dynamic pressure (no interplanetary magnetic field (IMF)). Concentration of the plasma sheet current occurs preferentially at 14-18 R{sub E} on the tail side of the Earth, which is an indication that, magnetically, this is the most fragile region of the tail structure. It is the demarcation region between the dipolar and streaming field line structures. Therefore, in the presence of resistivity, magnetic reconnection can be preferentially driven here by a compression disturbance of some sort. In the present initial-value problem, reconnection occurs at 15-20 R{sub E} in the tail and develops into a large lump of plasma surrounded by reconnected field lines, a plasmoid, which is ejected tailward. The time scale of the plasmoid formation and ejection process is very slow, of the order of several hours, when no IMF exists. After ejecting one plasmoid, reconnection occurs again in the plasma sheet, and a second plasmoid is formed and ejected. This result shows that a magnetosphere that has a sufficiently long tail and a neutral sheet is fragile and subject to plasmoid formation. The authors also show that the hot plasma, when mapped down to the ionosphere along the field lines, encompasses the auroral oval in agreement with the DE satellite observations.

Kageyama, A. (Hiroshima Univ. (Japan)); Watanabe, K.; Sato, T. (National Inst. for Fusion Science, Nagoya (Japan))

1992-04-01

108

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

109

Can Streamer Blobs Prevent the Buildup of the Interplanetary Magnetic Field?  

NASA Astrophysics Data System (ADS)

Coronal mass ejections continuously drag closed magnetic field lines away from the Sun, adding new flux to the interplanetary magnetic field (IMF). We propose that the outward-moving blobs that have been observed in helmet streamers are evidence of ongoing, small-scale reconnection in streamer current sheets, which may play an important role in the prevention of an indefinite buildup of the IMF. Reconnection between two open field lines from both sides of a streamer current sheet creates a new closed field line, which becomes part of the helmet, and a disconnected field line, which moves outward. The blobs are formed by plasma from the streamer that is swept up in the trough of the outward-moving field line. We show that this mechanism is supported by observations from Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph. Additionally, we propose a thorough statistical study to quantify the contribution of blob formation to the reduction of the IMF and indicate how this mechanism may be verified by observations with SOHO/Ultraviolet Coronagraph Spectrometer and the proposed NASA Solar Terrestrial Relations Observatory and ESA Polar Orbiter missions.

van Aalst, M. K.; Martens, P. C. H.; Beliën, A. J. C.

1999-02-01

110

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

111

Comparing generic models for interplanetary shocks and magnetic clouds axis configurations at 1 AU  

E-print Network

Interplanetary Coronal Mass Ejections are the manifestation of solar transient eruptions, which can significantly modify the plasma and magnetic conditions in the heliosphere. They are often preceded by a shock, and a magnetic flux rope is detected in situ in a third to half of them. The main aim of this study is to obtain the best quantitative shape for the flux rope axis and for the shock surface from in situ data obtained during spacecraft crossings of these structures. We first compare the orientation of the flux ropes axes and shock normals obtained from independent data analyses of the same events, observed in situ at 1AU from the Sun. Then, we carry out an original statistical analysis of axes/shock normals by deriving the statistical distributions of their orientations. We fit the observed distributions using the distributions derived from several synthetic models describing these shapes. We show that the distributions of axis/shock orientations are very sensitive to their respective shape. One classi...

Janvier, Miho; Demoulin, Pascal; Masias-Meza, Jimmy; Lugaz, Noe

2015-01-01

112

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

113

The B-dot Earth Average Magnetic Field  

NASA Technical Reports Server (NTRS)

The average Earth's magnetic field is solved with complex mathematical models based on mean square integral. Depending on the selection of the Earth magnetic model, the average Earth's magnetic field can have different solutions. This paper presents a simple technique that takes advantage of the damping effects of the b-dot controller and is not dependent of the Earth magnetic model; but it is dependent on the magnetic torquers of the satellite which is not taken into consideration in the known mathematical models. Also the solution of this new technique can be implemented so easily that the flight software can be updated during flight, and the control system can have current gains for the magnetic torquers. Finally, this technique is verified and validated using flight data from a satellite that it has been in orbit for three years.

Capo-Lugo, Pedro A.; Rakoczy, John; Sanders, Devon

2013-01-01

114

Twenty years of interplanetary magnetic field variations with periods in the range of 10 days to 3 years  

NASA Technical Reports Server (NTRS)

Twenty years of interplanetary magnetic field data collected primarily by the IMP-8 spacecraft near Earth has been analyzed by a dynamic periodogram method in search of significant periodicities in the range of 10 days to 3 years. The method has the advantage of detecting variations with time in the periodicities besides determining the power and phase of the dominant variations. It has been found that the well known periodicities near 1 year and 27 days are strongly modulated by the solar cycle. Both of these periodicities are only detected during solar minimum. During solar maximum. a number of unusual variations are observed. Special emphasis will be placed on the recently reported 1.3 year variation in solar wind parameters besides periods in the interplanetary magnetic field near 51, 73 and 154 days. Correlations with solar wind plasma and solar index variations will also be presented.

Szabo, A.; Lepping, R. P.; King, J. H.

1995-01-01

115

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

116

The magnetic flux excess effect as a consequence of non-Parker radial evolution of interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The “magnetic flux excess” effect is exceeding of magnetic flux Fs=4?|Br|r2 measured by distant spacecraft over the values obtained through measurements at the Earth’s orbit (Owens et al., JGR, 2008). Theoretically, its conservation should take place at any heliocentric distance r further than 10 solar radii, which means that the difference between the flux measured at 1 AU and Fs observed in another point in the heliosphere should be zero. However, the difference is negative closer to the Sun and increasingly positive at larger heliocentric distances. Possible explanations of this effect are continuously discussed, but the consensus is yet not reached.It is shown that a possible source of this effect is the solar wind expansion not accordingly with the Parker solution at least at low heliolatitudes. The difference between the experimentally found (r?5/3) and commonly used (r?2) radial dependence of the radial component of the IMF Br may lead to mistakes in the IMF point-to-point recalculations (Khabarova & Obridko, ApJ, 2012; Khabarova, Astronomy Reports, 2013). Using the observed Br (r) dependence, it is easy to find the variation of difference between the magnetic flux Fs(r) at certain heliocentric distance r and Fs_1AU at 1 AU, which can be calculated as Fs(r)-Fs_1AU =4?·(B1AU /[1AU]-5/3) (r2-5/3 –[1AU]2-5/3) (Khabarova, Astronomy Reports, 2013).The possible influence of presence of the heliospheric current sheet near the ecliptic plane on the picture of magnetic field lines and consequent deviation from the Parker's model is discussed.- Khabarova Olga, and Obridko Vladimir, 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- Olga V. Khabarova, The interplanetary magnetic field: radial and latitudinal dependences. Astronomy Reports, 2013, Vol. 57, No. 11, pp. 844–859, http://arxiv.org/ftp/arxiv/papers/1305/1305.1204.pdf

Khabarova, Olga

2015-04-01

117

Geophysical phenomena in the polar cap during northward interplanetary magnetic field; IUGG General Assembly, 20th, Vienna, Austria, August 1991  

NASA Technical Reports Server (NTRS)

The interaction of the Earth's magnetosphere with the solar wind and northward interplanetary magnetic field (IMF) continues to raise scientific interest and controversy. A selected group of papers from a conference on this topic discuss the following subjects: electric field generation, theoretical models of polar-cap convection, polar-cap distributions, dependencies of the polar-cap auroral distribution, and boundary populations in the polar-caps. Also discussed are satellite observations of polar arcs and mapping of the ionospheric convection response.

Troshichev, O. A. (editor); Burke, W. J. (editor)

1994-01-01

118

Correlated particle and magnetic field observations of a large-scale magnetic loop structure behind an interplanetary shock  

NASA Technical Reports Server (NTRS)

From a survey of observations on ISEE-3, an example of correlated particle and magnetic field observations of a large-scale magnetic loop structure is presented. Bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35-1600 keV approximately 12 hours after the passage of the interplanetary shock of December 11, 1980, and directly after the passage of a discontinuity. For each of the eight logarithmically spaced energy channels, a three-dimensional anisotropy analysis reveals streaming along both directions of the magnetic field. The magnetic field rotated slowly but steadily through approximately 180 deg during this same 40-hour period; this is consistent with the existence of a large-scale loop with extent greater than 0.5 AU. The observations suggest that the particles are being injected into the loop sunward of the spacecraft; they appear as bidirectional fluxes in the outermost regions of the loop arising from a combination of focusing and near scatter-free transport.

Sanderson, T. R.; Marsden, R. G.; Reinhard, R.; Wenzel, K.-P.; Smith, E. J.

1983-01-01

119

Magnetohydrodynamic Simulation of the Earth's Magnetotail Response to the Interplanetary Magnetic Field Variations  

NASA Astrophysics Data System (ADS)

In the present work, a study of the dynamical response of the macroscopic parameters, den-sity, pressure, and velocity, of the Earth's magnetotail, was carried out. The goal of this work was to study the variation of such parameters as a response to the different topologies of the Interplanetary Magnetic Field (IMF) present in some of the geoeffective solar wind magnetic structures. We used Magnetohydrodynamic simulation in order to approach this problem. The bi-dimensional Magnetohydrodynamic code was originally developed by Ogino et al. (1986), being restricted to the formation of the terrestrial magnetosphere with a stationary IMF. After we performed the necessary modifications in the original code, the magnetospheric dynamics was observed. Based on that, we investigated the response of the different regions of the magne-tosphere (specially the magnetotail) to different IMF conditions. Four different configurations of the IMF were analyzed when interacting with the Earth's magnetosphere. Among these different topologies, one could find a representative for a positive shock, i.e, a shock with a pos-itive Bz , another for a negative shock, i.e, a shock with a negative Bz , an idealized HILDCAA event with a Bz squared fluctuation similar to an Alfvénic one, and, finally, a structure similar to a Magnetic Cloud. The considered changes in the IMF configuration favored the observation of different physical processes. Among these processes, it was possible to observe the forma-tion of the Near-Earth Neutral Line for the IMF configuration representative of a negative Bz (negative shock). Furthermore, a plasmoid release was observed, which is associated with one of the most dynamics phenomena in the terrestrial magnetosphere: the substorm.

Jauer, Paulo Ricardo; Echer, Ezequiel; Alves, Maria Virginia

120

The field-aligned currents in the magnetotail response to the interplanetary magnetic field orientation  

NASA Astrophysics Data System (ADS)

The influences of the interplanetary magnetic field (IMF) cone angle theta and clock angle phi on the field-aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle, and has two peaks at -90º and +110º clock angle, respectively. The peak at +110º is distinctly larger than that at -90º. Overall, there are more FACs between 0º

Cheng, Zhengwei; Dunlop, Malcolm; Liu, Zhenxing; Shi, Jiankui

121

Observation of a retreating x line and magnetic islands poleward of the cusp during northward interplanetary magnetic field conditions  

NASA Astrophysics Data System (ADS)

When the interplanetary magnetic field is northward, reconnection occurs in each hemisphere on lobe field lines, poleward of the cusp. We have identified a case where the Cluster spacecraft crossed the magnetopause and encountered a tailward retreating x line. The x line is identified by the encounter of both a tailward and sunward jet, as well as Hall magnetic field signatures in the out-of-plane direction. Additionally, we find no signatures of electron heating and hypothesize that the spacecraft is too close to the x line to observe the accelerated electrons. Using two spacecraft, we are able to resolve the velocity of the structure, which moves near the magnetosheath speed. The speed of the x line is also consistent with the asymmetric reconnection theory. To our knowledge, this is the first time the speed of a retreating x line has been measured directly. Additionally, we observe ion distribution functions with counterstreaming populations, suggesting that a second x line formed sunward of the original one, leading to a magnetic island.

Wilder, F. D.; Eriksson, S.; Trattner, K. J.; Cassak, P. A.; Fuselier, S. A.; Lybekk, B.

2014-12-01

122

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

123

Interhemispherical asymmetry of substorm onset locations and the Interplanetary Magnetic Field  

E-print Network

angle, c organizes11 the average substorm onset locations in both hemispheres. The IMF c control is a12 the IMF and Z-axis in the YZ plane of the Geocentric Solar Magnetoispheric31 (GSM) reference system [Ã?stgaard et al., 2005]. We suggested33 that the IMF c control can be understood as the magnetic stress

Ã?stgaard, Nikolai

124

Interhemispherical asymmetry of substorm onset locations and the interplanetary magnetic field  

E-print Network

, c, organizes the average substorm onset locations in both hemi- spheres. The IMF c control between the IMF and Zaxis in the YZ plane of the Geocentric Solar Magnetospheric (GSM) reference system [Ã?stgaard et al., 2005]. [4] We suggested that the IMF c control can be under- stood as the magnetic stress

Bergen, Universitetet i

125

Magnetic Field-line Lengths in Interplanetary Coronal Mass Ejections Inferred from Energetic Electron Events  

NASA Astrophysics Data System (ADS)

About one quarter of the observed interplanetary coronal mass ejections (ICMEs) are characterized by enhanced magnetic fields that smoothly rotate in direction over timescales of about 10-50 hr. These ICMEs have the appearance of magnetic flux ropes and are known as "magnetic clouds" (MCs). The total lengths of MC field lines can be determined using solar energetic particles of known speeds when the solar release times and the 1 AU onset times of the particles are known. A recent examination of about 30 near-relativistic (NR) electron events in and near 8 MCs showed no obvious indication that the field-line lengths were longest near the MC boundaries and shortest at the MC axes or outside the MCs, contrary to the expectations for a flux rope. Here we use the impulsive beamed NR electron events observed with the Electron Proton and Alpha Monitor instrument on the Advanced Composition Explorer spacecraft and type III radio bursts observed on the Wind spacecraft to determine the field-line lengths inside ICMEs included in the catalog of Richardson & Cane. In particular, we extend this technique to ICMEs that are not MCs and compare the field-line lengths inside MCs and non-MC ICMEs with those in the ambient solar wind outside the ICMEs. No significant differences of field-line lengths are found among MCs, ICMEs, and the ambient solar wind. The estimated number of ICME field-line turns is generally smaller than those deduced for flux-rope model fits to MCs. We also find cases in which the electron injections occur in solar active regions (ARs) distant from the source ARs of the ICMEs, supporting CME models that require extensive coronal magnetic reconnection with surrounding fields. The field-line lengths are found to be statistically longer for the NR electron events classified as ramps and interpreted as shock injections somewhat delayed from the type III bursts. The path lengths of the remaining spike and pulse electron events are compared with model calculations of solar wind field-line lengths resulting from turbulence and found to be in good agreement.

Kahler, S. W.; Haggerty, D. K.; Richardson, I. G.

2011-08-01

126

Magnetic Field-Line Lengths in Interplanetary Coronal Mass Ejections Inferred from Energetic Electron Events  

NASA Technical Reports Server (NTRS)

About one quarter of the observed interplanetary coronal mass ejections (ICMEs) are characterized by enhanced magnetic fields that smoothly rotate in direction over timescales of about 10-50 hr. These ICMEs have the appearance of magnetic flux ropes and are known as "magnetic clouds" (MCs). The total lengths of MC field lines can be determined using solar energetic particles of known speeds when the solar release times and the I AU onset times of the particles are known. A recent examination of about 30 near-relativistic (NR) electron events in and near 8 MCs showed no obvious indication that the field-line lengths were longest near the MC boundaries and shortest at the MC axes or outside the MCs, contrary to the expectations for a flux rope. Here we use the impulsive beamed NR electron events observed with the Electron Proton and Alpha Monitor instrument on the Advanced Composition Explorer spacecraft and type III radio bursts observed on the Wind spacecraft to determine the field-line lengths inside ICMEs included in the catalog of Richardson & Cane. In particular, we extend this technique to ICMEs that are not MCs and compare the field-line lengths inside MCs and non-MC ICMEs with those in the ambient solar wind outside the ICMEs. No significant differences of field-line lengths are found among MCs, ICMEs, and the ambient solar wind. The estimated number of ICME field-line turns is generally smaller than those deduced for flux-rope model fits to MCs. We also find cases in which the electron injections occur in solar active regions CARs) distant from the source ARs of the ICMEs, supporting CME models that require extensive coronal magnetic reconnection with surrounding fields. The field-line lengths are found to be statistically longer for the NR electron events classified as ramps and interpreted as shock injections somewhat delayed from the type III bursts. The path lengths of the remaining spike and pulse electron events are compared with model calculations of solar wind field-line lengths resulting from turbulence and found to be in good agreement.

Kahler, S. W.; Haggerty, D. K.; Richardson, I. G.

2011-01-01

127

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

128

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

129

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

130

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

131

IMF By-controlled field-aligned currents in the magnetotail during northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The influence of the interplanetary magnetic field (IMF) By component on the field-aligned currents (FACs) in the plasma sheet boundary layer (PSBL) in the magnetotail during the northward IMF were investigated using the data from Cluster. There are 748 FACs cases selected to do analysis. We present that the IMF By component plays a very important role in controlling the flow direction of the FACs in the PSBL in the magnetotail. In the northern hemisphere, the influence of the positive (negative) IMF By is an earthward (tailward) FACs. To the contrary, in the southern hemisphere, the effect of the positive (negative) IMF By is a tailward (earthward) FACs. There is a clear north-south asymmetry of the polarity of the FACs in the PSBL when IMF By is positive or negative, and this asymmetry of the polarity is more distinct when IMF By is positive. The FAC density is controlled by IMF By only when |IMF By| is large. When |IMF By| is more than 10 nT the absolute FAC density in the PSBL has an obvious positive correlation with the |IMF By|. When |IMF By| is less than 10 nT, there is no correlation between the absolute FAC density and |IMF By|. There is a clear dusk-dawn asymmetry in the current densities for the FACs in the PSBL, with the dawn currents appearing larger than the dusk currents. The FAC with the largest (smallest) density is located in the range of 0100?MLT<0200 (2100?MLT<2200).

Cheng, Z. W.; Shi, J. K.; Dunlop, M.; Liu, Z. X.

2014-08-01

132

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

133

An Alternative Interpretation of the Relationship between the Inferred Open Solar Flux and the Interplanetary Magnetic Field  

NASA Technical Reports Server (NTRS)

Photospheric observations at the Wilcox Solar Observatory (WSO) represent an uninterrupted data set of 32 years and are therefore unique for modeling variations in the magnetic structure of the corona and inner heliosphere over three solar cycles. For many years, modelers have applied a latitudinal correction factor to these data, believing that it provided a better estimate of the line-of-sight magnetic field. Its application was defended by arguing that the computed open flux matched observations of the interplanetary magnetic field (IMF) significantly better than the original WSO correction factor. However, no physically based argument could be made for its use. In this Letter we explore the implications of using the constant correction factor on the value and variation of the computed open solar flux and its relationship to the measured IMF. We find that it does not match the measured IMF at 1 AU except at and surrounding solar minimum. However, we argue that interplanetary coronal mass ejections (ICMEs) may provide sufficient additional magnetic flux to the extent that a remarkably good match is found between the sum of the computed open flux and inferred ICME flux and the measured flux at 1 AU. If further substantiated, the implications of this interpretation may be significant, including a better understanding of the structure and strength of the coronal field and I N providing constraints for theories of field line transport in the corona, the modulation of galactic cosmic rays, and even possibly terrestrial climate effects.

Riley, Pete

2007-01-01

134

Three-Dimensional Simulation of High-Latitude Ionospheric Neutral and Ion Outflows During Magnetic Storm Conditions, and Northward Turnings of the Interplanetary Magnetic Field  

Microsoft Academic Search

Ion outflow from high-latitudes occurs along geomagnetic field lines that are connected to the interplanetary magnetic field (IMF) and is associated with thermal ions of ionospheric origin. The horizontal motion of ions in the polar wind depends on the high-latitude convection electric fields, and their field-aligned outflow dynamics are modified by the heat input due to precipitating electrons in the

L. C. Gardner; R. W. Schunk

2005-01-01

135

Interplanetary Charged Dust Magnetic Clouds Striking the Magnetosphere: Coordinated Space-based and Ground-based Observations  

NASA Astrophysics Data System (ADS)

In general, asteroids, meteoroids and dust do not interact with the plasma structures in the solar system, but after a collision between fast moving bodies the debris cloud contains nanoscale dust particles that are charged and behave like heavy ions. Dusty magnetic clouds are then accelerated to the solar wind speed. While they pose no threat to spacecraft because of the particle size, the coherency imposed by the magnetization of the cloud allows the cloud to interact with the Earth’s magnetosphere as well as the plasma in the immediate vicinity of the cloud. We call these clouds Interplanetary Field Enhancements (IFEs). These IFEs are a unique class of interplanetary field structures that feature cusp-shaped increases and decreases in the interplanetary magnetic field and a thin current sheet. The occurrence of IFEs is attributed to the interaction between the solar wind and dust particles produced in inter-bolide collisions. Previous spacecraft observations have confirmed that IFEs move with the solar wind. When IFEs strike the magnetosphere, they may distort the magnetosphere in several possible ways, such as producing a small indentation, a large scale compression, or a glancing blow. In any event if the IFE is slowed by the magnetosphere, the compression of the Earth’s field should be seen in the ground-based magnetic records that are continuously recorded. Thus it is important to understand the magnetospheric response to IFE arrival. In this study, we investigate the IFE structure observed by spacecraft upstream of the magnetosphere and the induced magnetic field perturbations observed by networks of ground magnetometers, including the THEMIS, CARISMA, McMAC arrays in North America and the IMAGE array in Europe. We find that, in a well-observed IFE event on December 24, 2006, all ground magnetometer stations observed an impulse at approximately 1217 UT when the IFE was expected to arrive at the Earth’s magnetopause. These ground stations spread across many latitudes and local times, indicating that the impulse can penetrate magnetic shells as well as propagate along field lines. The equivalent currents in the ionosphere inferred from ground magnetometer measurements show a single vortex with a center located in the morning sector where the IFE impacted the magnetopause. Our observations suggest that the IFE-induced current system in the magnetosphere differs from those caused by sudden impulses.

Russell, C. T.; Chi, Peter; Lai, Hairong

136

The Fraction of Interplanetary Coronal Mass Ejections That Are Magnetic Clouds: Evidence for a Solar Cycle Variation  

NASA Technical Reports Server (NTRS)

"Magnetic clouds" (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized by enhanced magnetic fields with an organized rotation in direction, and low plasma beta. Though intensely studied, MCs only constitute a fraction of all the ICMEs that are detected in the solar wind. A comprehensive survey of ICMEs in the near- Earth solar wind during the ascending, maximum and early declining phases of solar cycle 23 in 1996 - 2003 shows that the MC fraction varies with the phase of the solar cycle, from approximately 100% (though with low statistics) at solar minimum to approximately 15% at solar maximum. A similar trend is evident in near-Earth observations during solar cycles 20 - 21, while Helios 1/2 spacecraft observations at 0.3 - 1.0 AU show a weaker trend and larger MC fraction.

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

2004-01-01

137

Magnetohydrodynamic simulation of the interaction between interplanetary strong shock and magnetic cloud and its consequent geoeffectiveness: 2. Oblique collision  

NASA Astrophysics Data System (ADS)

Numerical studies of the interplanetary "shock overtaking magnetic cloud (MC)" event are continued by a 2.5-dimensional magnetohydrodynamic (MHD) model in heliospheric meridional plane. Interplanetary direct collision (DC)/oblique collision (OC) between an MC and a shock results from their same/different initial propagation orientations. For radially erupted MC and shock in solar corona, the orientations are only determined respectively by their heliographic locations. OC is investigated in contrast with the results in DC (Xiong, 2006). The shock front behaves as a smooth arc. The cannibalized part of MC is highly compressed by the shock front along its normal. As the shock propagates gradually into the preceding MC body, the most violent interaction is transferred sideways with an accompanying significant narrowing of the MC's angular width. The opposite deflections of MC body and shock aphelion in OC occur simultaneously through the process of the shock penetrating the MC. After the shock's passage, the MC is restored to its oblate morphology. With the decrease of MC-shock commencement interval, the shock front at 1 AU traverses MC body and is responsible for the same change trend of the latitude of the greatest geoeffectiveness of MC-shock compound. Regardless of shock orientation, shock penetration location regarding the maximum geoeffectiveness is right at MC core on the condition of very strong shock intensity. An appropriate angular difference between the initial eruption of an MC and an overtaking shock leads to the maximum deflection of the MC body. The larger the shock intensity is, the greater is the deflection angle. The interaction of MCs with other disturbances could be a cause of deflected propagation of interplanetary coronal mass ejection (ICME).

Xiong, Ming; Zheng, Huinan; Wang, Yuming; Wang, Shui

2006-11-01

138

Interplanetary shock waves associated with solar flares  

NASA Technical Reports Server (NTRS)

The interaction of the earth's magnetic field with the solar wind is discussed with emphasis on the influence of solar flares. The geomagnetic storms are considerered to be the result of the arrival of shock wave generated by solar flares in interplanetary space. Basic processes in the solar atmosphere and interplanetary space, and hydromagnetic disturbances associated with the solar flares are discussed along with observational and theoretical problems of interplanetary shock waves. The origin of interplanetary shock waves is also discussed.

Chao, J. K.; Sakurai, K.

1974-01-01

139

Charts of joint Kelvin-Helmholtz and Rayleigh-Taylor instabilites at the dayside magnetopause for strongly northward interplanetary magnetic field  

Microsoft Academic Search

We present maximum growth rate charts of the Kelvin-Helmholtz (KH) and Rayleigh-Taylor (RT) instabilities at the dayside magnetopause (MP), considering two orientations of the interplanetary magnetic field (IMF) (due north and 30° west of north). We input parameters in the plasma depletion layer calculated from an MHD code. We study both a sharp MP transition and an MP with an

C. J. Farrugia; F. T. Gratton; L. Bender; H. K. Biernat; N. V. Erkaev; J. M. Quinn; R. B. Torbert; V. Dennisenko

1998-01-01

140

Particle entry into the magnetosphere with a southward interplanetary magnetic field studied by a three-dimensional electromagnetic particle code  

NASA Astrophysics Data System (ADS)

We report progress in the long-term effort to represent the interaction of the solar wind with the Earth's magnetosphere using a three-dimensional electromagnetic particle code. A new run that includes an interplanetary magnetic field yields results that are encouragingly consistent with established features of the solar wind-magnetosphere interaction. After a quasi-steady state is established with an unmagnetized solar wind we switch on a southward interplanetary magnetic field (IMF), which causes the magnetosphere to stretch and allows particles to enter the cusps and nightside magnetosphere. Analysis of magnetic fields near the Earth confirms a signature of magnetic reconnection at the dayside magnetopause, and the plasma sheet in the near-Earth magnetotail clearly thins. Later magnetic reconnection also takes place in the near-Earth magnetotail. Arrival of southward IMF near the front of the magnetosphere causes a sunward velocity in the dayside magnetosphere, as required to feed flux tubes into the dayside reconnection process. Sunward flow near the equatorial plane of the magnetosphere implies a dawn-to-dusk electric field. Initially, the velocity in the distant tail is not much affected by the southward turning. Therefore the dawn-dusk electric field increases in the sunward direction, which causes Bz to decrease with time in the near-Earth magnetotail. The cross-field current also thins and intensifies, which excites a kinetic (drift kink) instability along the dawn-dusk direction. As a result of this instability the electron compressibility effect appears to be reduced and to allow the collisionless tearing to grow rapidly with the reduced Bz component. At the same time the nightside magnetic fields are dipolarized and a plasmoid is formed tailward. We find that due to the reconnection particles were injected toward the Earth from the neutral line (X line). Consistent with this dawn-dusk electric field and magnetic reconnection at the dayside magnetopause, both ions and electrons enter the magnetospheric interior easily. In our simulations, kinetic effects self-consistently determine the dissipation rate in the magnetopause associated with reconnection.

Nishikawa, K.-I.

1997-08-01

141

Influences of the interplanetary magnetic field clock angle and cone angle on the field-aligned currents in the magnetotail  

NASA Astrophysics Data System (ADS)

The influences of the interplanetary magnetic field (IMF) cone angle ? and clock angle ? on the field-aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle and has two peaks at -90° and +110° clock angle, respectively. The peak at +110° is distinctly larger than that at -90°. Overall, there are more FACs between 0° < ? < 180°, indicating that FACs occurrence is closely associated with duskward IMF. More FACs occur when 90° < |?| < 180°, implying that FAC is closely associated with southward IMF. The large FAC densities occur when 60° < |?| < 120°. The density also has two peaks and the peak at +90° clock angle (duskward IMF) is larger than that at -90° (dawnward IMF). These results indicate that the IMF influence on the FACs is from all IMF components and not only from a single component.

Cheng, Z. W.; Shi, J. K.; Dunlop, M.; Liu, Z. X.

2013-10-01

142

Galactic Cosmic Ray Intensity Response to Interplanetary Coronal Mass Ejections/Magnetic Clouds in 1995-2009  

NASA Technical Reports Server (NTRS)

We summarize the response of the galactic cosmic ray (CGR) intensity to the passage of the more than 300 interplanetary coronal mass ejections (ICMEs) and their associated shocks that passed the Earth during 1995-2009, a period that encompasses the whole of Solar Cycle 23. In approx.80% of cases, the GCR intensity decreased during the passage of these structures, i.e., a "Forbush decrease" occurred, while in approx.10% there was no significant change. In the remaining cases, the GCR intensity increased. Where there was an intensity decrease, minimum intensity was observed inside the ICME in approx.90% of these events. The observations confirm the role of both post-shock regions and ICMEs in the generation of these decreases, consistent with many previous studies, but contrary to the conclusion of Reames, Kahler, and Tylka (Astrophys. 1. Lett. 700, L199, 2009) who, from examining a subset of ICMEs with flux-rope-like magnetic fields (magnetic clouds) argued that these are "open structures" that allow free access of particles including GCRs to their interior. In fact, we find that magnetic clouds are more likely to participate in the deepest GCR decreases than ICMEs that are not magnetic clouds.

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

2011-01-01

143

Interplanetary magnetic field connection to the sun during electron heat flux dropouts in the solar wind  

NASA Technical Reports Server (NTRS)

The paper discusses observations of 2- to 8.5-keV electrons, made by measurements aboard the ISEE 3 spacecraft during the periods of heat flux decreases (HFDs) reported by McComas et al. (1989). In at least eight of the total of 25 HFDs observed, strong streaming of electrons that were equal to or greater than 2 keV outward from the sun was recorded. In one HFD, an impulsive solar electron event was observed with an associated type III radio burst, which could be tracked from the sun to about 1 AU. It is concluded that, in many HFDs, the interplanetary field is still connected to the sun and that some energy-dependent process may produce HFDs without significantly perturbing electrons of higher energies.

Lin, R. P.; Kahler, S. W.

1992-01-01

144

Kelvin-Helmholtz vortices observed by THEMIS at the duskside of the magnetopause under southward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The Time History of Events and Macroscale Interactions during Substorms (THEMIS) observed several magnetopause crossings periodically at the duskside of magnetopause under southward interplanetary magnetic field (IMF), with significant sunward returning flows inside the magnetopause. The vortex features of the flows and the periodic enhancements in the calculated vorticity normal to the spacecraft plane could be found in the observation. The distortion of the magnetopause, the periodic features of vortex flows, the tailward propagation, and the evaluation of Kelvin-Helmholtz instability (KHI) condition support the evidence of the Kelvin-Helmholtz vortices produced by the velocity shear at the duskside of magnetopause. Based on three-point simultaneous observations of the flow, the vorticity was calculated to be about 0.15 s-1, similar to previous results. The tailward propagation of the vortices along the flank magnetopause was estimated to be about 292 km/s. The circular-induced electric field of several mV/m was deduced perpendicular to the magnetic field when the magnetic field compression occurred at the edges of the vortices.

Yan, G. Q.; Mozer, F. S.; Shen, C.; Chen, T.; Parks, G. K.; Cai, C. L.; McFadden, J. P.

2014-07-01

145

Chang’E-1 observations of pickup ions near the Moon under different interplanetary magnetic field conditions  

NASA Astrophysics Data System (ADS)

Detailed features of the near-Moon pickup ions under different interplanetary magnetic field (IMF) conditions are investigated using data obtained from the solar wind ion detector (SWID-B) onboard Chang'E-1. In the event studied, Chang'E-1 was on a noon-midnight meridian orbit and the field-of-view of the SWID-B was in the satellite orbital plane. The observations show that the pickup energy detected depends not only on where these particles are detected but also on their incident angles. As the spacecraft moved into the wake from the South Pole along the midnight meridian, wider incident angle distributions were measured. When IMF Bx was significant, the pickup ions had a strong velocity component parallel to the magnetic field, and the efficiency of acceleration was reduced when the IMF By decreased. The back tracking calculations show that the possible source of the pickup ions is solar wind ions scattered/reflected on the lunar surface in a wide area over the dayside of the Moon, from both magnetic and nonmagnetic anomaly regions. A three dimensional analysis performed on the asymmetric properties of the pick-up ions can explain most of the particle behavior observed near the Moon under different IMF conditions.

Zhong, J.; Xie, L.; Zhang, H.; Li, J. X.; Pu, Z. Y.; Nowada, M.; Wang, X. D.; Wang, X. Y.; Parks, G. K.; Zong, Q. G.; Fu, S. Y.; Guo, R. L.; Yao, Z. H.; Zhang, X. G.; Reme, H.; Wang, S. J.

2013-05-01

146

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

PubMed

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 spaceship there are extrapolations and guesses, but no data, on the angular distribution of SCR's, an information that is necessary for establishing whatever defence strategy. It was therefore proposed of sending to Mars a measurement device, that should continuously collect data during the travel, and possibly also in the orbit around Mars and on the Mars surface. The device should identify the particle and privilege the completeness in the measurement of its parameters. In fact the high energy electrons travel at speed of the light and could be used in the and future dangerous proton component. Also the much less abundant but individually more dangerous ions should be identified. The device should indeed include a magnetic spectrometer and a high granularity range telescope, and a good time of flight measurement. ASI is supporting an assessment study of a possible mission of such a device on board of the 2005 probe to Mars. A parallel technical study is also in progress to define the workable techniques and the possible configurations of a system of magnetic lenses for protecting the crew of a spaceship. PMID:11776989

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

2001-01-01

147

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

NASA Technical Reports Server (NTRS)

In a consideration of only those periods when the delay time from the interplanetary observing position to the magnetosphere is less than 5 minutes, it is found that, irrespective of substorm activity: (1) The 45 minute average value of interplanetary B(z) predicts the latitudes of the poleward and equatorward boundaries of polar cusp electron precipitation with rms errors of 1.34 deg and 1.16 deg respectively; (2) Both boundaries more equatorward by about 5 deg as B(z) varies from 1 to -6 gammas, the cusp remaining about 40 deg wide; (3) The amount of flux added to the polar cap is about 9.2 percent of the total southward flux impingent on the magnetosphere in the previous 45 minutes; (4) As B(z) becomes more positive, the equatorward boundary moves only slightly more poleward (1/2 deg between B(z) = 2 gammas and B(z) = 6 gammas, while the poleward boundary moves significantly toward higher latitudes, resulting in a cusp approximately 7 deg wide for B(z) = 6 gammas.

Burch, J. L.

1973-01-01

148

Microstructure of the interplanetary magnetic field near 4 and 5 AU  

Microsoft Academic Search

Seventy-two days of vector magnetic field measurements from Pioneer 10 and 11 are analyzed for information about magnetic field fluctuations in the quiet solar wind near 4 and 5 AU. Calculated as functions of frequency over the range 4 x 10⁻⁵ to 9 x 10⁻³ Hz, directional properties of magnetic field fluctuations are presented and are discussed with reference to

G. D. Parker

1980-01-01

149

Buildup of the ring current during periodic loading-unloading cycles in the magnetotail driven by steady southward interplanetary magnetic field  

Microsoft Academic Search

During prolonged intervals of negative interplanetary magnetic field (IMF) B z the magnetosphere often enters a state in which quasi-periodic, large-amplitude oscillations of energetic particle fluxes are observed at the geosynchronous orbit. We use the global magnetosphere MHD code BATS-R-US output during a long period of steady southward IMF B z to drive the Fok Ring Current Model. Previous simulations

A. Taktakishvili; M. M. Kuznetsova; M. Hesse; M.-C. Fok; L. Rastätter; M. Maddox; A. Chulaki; T. I. Gombosi; D. L. De Zeeuw

2007-01-01

150

Effect of the Global Topology of the Interplanetary Magnetic Field on the Properties of Impulsive Acceleration Processes in Distant Regions of the Earth's Magnetospheric Tail  

SciTech Connect

The paper is devoted to a statistical study of high-speed ion beams (beamlets) observed by the Interball-1 and Interball-2 satellites in the boundary region of the plasma sheet of the geomagnetic tail and in the high-latitude auroral regions of the Earth's magnetosphere. Beamlets result from nonlinear acceleration processes occurring in the current sheet in the distant regions of the geomagnetic tail. They propagate toward the Earth along the magnetic field lines and are detected in the boundary region of the plasma sheet and near the high-latitude boundary of the plasma sheet in the auroral region in the form of short (with a duration of 1-2 min) bursts of high-energy (with energies of about several tens of keV) ions. The sizes of the latitudinal zones where the beamlets are localized in the tail and in the auroral region are determined using the epoch superposition method. The relationship between the frequency of beamlet generation in the boundary region of the plasma sheet and the prehistory of the direction of the interplanetary magnetic field (the magnitude of a clock angle) is investigated. It was established that this direction exerts a global effect on the beamlet generation frequency; moreover, it was found that the beamlet generation frequency in the midnight local time sector of the tail and at the flanks depends differently on the direction of the interplanetary magnetic field. In the midnight sector, the beamlets are observed at almost all directions of the interplanetary field, whereas the frequency of their generation at the flanks is maximal only when the interplanetary magnetic field has a large y component.

Grigorenko, E.E. [Skobeltsyn Institute of Nuclear Physics, Moscow State University, Vorob'evy gory, Moscow, 119899 (Russian Federation); Institute for Space Research, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117810 (Russian Federation); Zelenyi, L.M. [Institute for Space Research, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117810 (Russian Federation); Fedorov, A.O.; Sauvaud, J.-A. [Centre d'Etude Spatiale des Rayonnements, 4346 31028 Toulouse (France)

2005-03-15

151

Magnetohydrodynamic simulation of the interaction between interplanetary strong shock and magnetic cloud and its consequent geoeffectiveness  

Microsoft Academic Search

Numerical studies have been performed to interpret the observed “shock overtaking magnetic cloud (MC)” event by a 2.5 dimensional magnetohydrodynamic (MHD) model in the heliospheric meridional plane. Results of an individual MC simulation show that the MC travels with a constant bulk flow speed. The MC is injected with a very strong inherent magnetic field over that in the ambient

Ming Xiong; Huinan Zheng; Yuming Wang; Shui Wang

2006-01-01

152

Influence of the interplanetary magnetic field orientation on polar cap ion trajectories - Energy gain and drift effects  

NASA Technical Reports Server (NTRS)

The influence of the interplanetary magnetic field (IMF) orientation on the transport of low-energy ions injected from the ionosphere is investigated using three-dimensional particle codes. It is shown that, unlike the auroral zone outflow, the ions originating from the polar cap region exhibit drastically different drift paths during southward and northward IMF. During southward IMF orientation, a 'two-cell' convection pattern prevails in the ionosphere, and three-dimensional simulations of ion trajectories indicate a preferential trapping of the light ions H(+) in the central plasma sheet, due to the wide azimuthal dispersion of the heavy ions, O(+). In contrast, for northward IMF orientation, the 'four-cell' potential distribution predicted in the ionosphere imposes a temporary ion drift toward higher L shells in the central polar cap. In this case, while the light ions can escape into the magnetotail, the heavy ions can remain trapped, featuring more intense acceleration (from a few electron volts up to the keV range) followed by precipitation at high invariant latitudes, as a consequence of their further travel into the tail.

Delcourt, D. C.; Horwitz, J. L.; Swinney, K. R.

1988-01-01

153

Field-aligned current reconfiguration and magnetospheric response to an impulse in the interplanetary magnetic field BY component  

NASA Astrophysics Data System (ADS)

the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, flow channels in the ionosphere with velocities in excess of 2 km/s have been observed, which can deposit large amounts of energy into the high-latitude thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from the Sondrestrom incoherent scatter radar and the Defense Meteorological Satellite Program spacecraft were used to investigate ionospheric convection during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field-Aligned Current (FAC) system. Additionally, data from AMPERE were used to investigate the time response of the dawnside FAC pair. We find there is a delay of approximately 1.25 h between the arrival of the dawnward IMF impulse at the magnetopause and strength of the dawnward FAC pair, which is comparable to substorm growth and expansion time scales under southward IMF. Additionally, we find at the time of the peak FAC, there is evidence of a reconfiguring four-sheet FAC system in the morning local time sector of the ionosphere. Additionally, we find an inverse correlation between the dawn FAC strength and both the solar wind Alfvénic Mach number and the SYM-H index. No statistically significant correlation between the FAC strength and the solar wind dynamic pressure was found.

Wilder, F. D.; Eriksson, S.; Korth, H.; Baker, J. B. H.; Hairston, M. R.; Heinselman, C.; Anderson, B. J.

2013-06-01

154

Field-Aligned Current Reconfiguration and Magnetospheric Response to an Impulse in the Interplanetary Magnetic Field BY Component  

NASA Astrophysics Data System (ADS)

When the interplanetary magnetic field (IMF) is dawnward or duskward, magnetic merging between the IMF and the geomagnetic field occurs near the cusp on the dayside flanks of the magnetosphere. During these intervals, flow channels in the ionosphere with velocities in excess of 2 km/s have been observed, which can deposit large amounts of energy into the high-latitude thermosphere. In this study, we analyze an interval on 5 April 2010 where there was a strong dawnward impulse in the IMF, followed by a gradual decay in IMF magnitude at constant clock angle. Data from the Sondrestrom incoherent scatter radar and the DMSP spacecraft were used to investigate ionospheric convection during this interval, and data from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) were used to investigate the associated Field-Aligned Current (FAC) system. Additionally, data from AMPERE were used to investigate the time response of the dawn-side FAC pair. We find there is a delay of approximately 1.25 hours between the arrival of the dawnward IMF impulse at the magnetopause and strength of the dawnward FAC pair, which is comparable to substorm growth and expansion time scales under southward IMF. Additionally, we find at the time of the peak FAC, there is evidence of a reconfiguring four-sheet FAC system in the morning local time sector of the ionosphere. Additionally, we find an inverse correlation between the dawn FAC strength and both the solar wind Alfvénic Mach number and the SYM-H index. No statistically significant correlation between the FAC strength and the solar wind dynamic pressure was found.

Wilder, F. D.; Eriksson, S.; Korth, H.; Hairston, M. R.; Baker, J. B.; Heinselman, C. J.

2013-12-01

155

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

E-print Network

interplanetary ejecta Vasyl Yurchyshyn Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314, USA Crimean Astrophysical

Yurchyshyn, Vasyl

156

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

157

Electron heat flux dropouts in the solar wind - Evidence for interplanetary magnetic field reconnection?  

NASA Technical Reports Server (NTRS)

An examination of ISEE-3 data from 1978 reveal 25 electron heat flux dropout events ranging in duration from 20 min to over 11 hours. The heat flux dropouts are found to occur in association with high plasma densities, low plasma velocities, low ion and electron temperatures, and low magnetic field magnitudes. It is suggested that the heat flux dropout intervals may indicate that the spacecraft is sampling plasma regimes which are magnetically disconnected from the sun and instead are connected to the outer heliosphere at both ends.

Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.; Bame, S. J.; Luhmann, J. G.; Smith, E. J.

1989-01-01

158

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

NASA Technical Reports Server (NTRS)

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, David A.; King, Joseph H.

1986-01-01

159

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

Microsoft Academic Search

The Helios, IMP 8, ISEE 3, and Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here they show that this evolution

D. A. Roberts

1990-01-01

160

Simulation of pitch angle diffusion of charged particles in a disordered magnetic field. [in interplanetary space  

NASA Technical Reports Server (NTRS)

Results are reported for computer simulation experiments in which a statistical ensemble of random magnetic field realizations is generated, orbits of charged particles in the random fields are followed, and a pitch-angle diffusion coefficient is derived from the temporal evolution of the orbits. Diffusion coefficients predicted by three nonlinear theories are compared with the derived coefficients for the standard quasilinear theory of velocity diffusion, and the goals of future simulations are outlined.

Kaiser, T. B.

1974-01-01

161

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

162

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

NASA Astrophysics Data System (ADS)

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 (FR) 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- ? 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 continuous 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- ?, CME width, and the ratio O 7/ O 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.

2013-05-01

163

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

164

Mean Interplanetary Magnetic Field Measurement Using the ARGO-YBJ Experiment  

E-print Network

The sun blocks cosmic ray particles from outside the solar system, forming a detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ experiment in Tibet. Because the cosmic ray particles are positive charged, the magnetic field between the sun and the earth deflects them from straight trajectories and results in a shift of the shadow from the true location of the sun. Here we show that the shift measures the intensity of the field which is transported by the solar wind from the sun to the earth.

G. Aielli; C. Bacci; B. Bartoli; P. Bernardini; X. J. Bi; C. Bleve; P. Branchini; A. Budano; S. Bussino; A. K. Calabrese Melcarne; P. Camarri; Z. Cao; A. Cappa; R. Cardarelli; S. Catalanotti; C. Cattaneo; P. Celio; S. Z. Chen; T. L. Chen; Y. Chen; P. Creti; S. W. Cui; B. Z. Dai; G. D'Alí Staiti; Danzengluobu; M. Dattoli; I. De Mitri; B. D'Ettorre Piazzoli; M. De Vincenzi; T. Di Girolamo; X. H. Ding; G. Di Sciascio; C. F. Feng; Z. Y. Feng; Zhenyong Feng; F. Galeazzi; P. Galeotti; R. Gargana; Q. B. Gou; Y. Q. Guo; H. H. He; Haibing Hu; Hongbo Hu; Q. Huang; M. Iacovacci; R. Iuppa; I. James; H. Y. Jia; Labaciren; H. J. Li; J. Y. Li; X. X. Li; B. Liberti; G. Liguori; C. Liu; C. Q. Liu; M. Y. Liu; J. Liu; H. Lu; X. H. Ma; G. Mancarella; S. M. Mari; G. Marsella; D. Martello; S. Mastroianni; X. R. Meng; P. Montini; C. C. Ning; A. Pagliaro; M. Panareo; L. Perrone; P. Pistilli; X. B. Qu; E. Rossi; F. Ruggieri; L. Saggese; P. Salvini; R. Santonico; P. R. Shen; X. D. Sheng; F. Shi; C. Stanescu; A. Surdo; Y. H. Tan; P. Vallania; S. Vernetto; C. Vigorito; B. Wang; H. Wang; C. Y. Wu; H. R. Wu; Z. G. Yao; B. Xu; L. Xue; Y. X. Yan; Q. Y. Yang; X. C. Yang; A. F. Yuan; M. Zha; H. M. Zhang; JiLong Zhang; JianLi Zhang; L. Zhang; P. Zhang; X. Y. Zhang; Y. Zhang; Zhaxisangzhu; Zhaxiciren; X. X. Zhou; F. R. Zhu; Q. Q. Zhu; G. Zizzi

2011-01-22

165

Mean Interplanetary Magnetic Field Measurement Using the ARGO-YBJ Experiment  

E-print Network

The sun blocks cosmic ray particles from outside the solar system, forming a detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ experiment in Tibet. Because the cosmic ray particles are positive charged, the magnetic field between the sun and the earth deflects them from straight trajectories and results in a shift of the shadow from the true location of the sun. Here we show that the shift measures the intensity of the field which is transported by the solar wind from the sun to the earth.

Aielli, G; Bartoli, B; Bernardini, P; Bi, X J; Bleve, C; Branchini, P; Budano, A; Bussino, S; Melcarne, A K Calabrese; Camarri, P; Cao, Z; Cappa, A; Cardarelli, R; Catalanotti, S; Cattaneo, C; Celio, P; Chen, S Z; Chen, T L; Chen, Y; Creti, P; Cui, S W; Dai, B Z; Staiti, G D'Alí; Danzengluobu,; Dattoli, M; De Mitri, I; Piazzoli, B D'Ettorre; De Vincenzi, M; Di Girolamo, T; Ding, X H; Di Sciascio, G; Feng, C F; Feng, Z Y; Feng, Zhenyong; Galeazzi, F; Galeotti, P; Gargana, R; Gou, Q B; Guo, Y Q; He, H H; Hu, Haibing; Hu, Hongbo; Huang, Q; Iacovacci, M; Iuppa, R; James, I; Jia, H Y; Labaciren,; Li, H J; Li, J Y; Li, X X; Liberti, B; Liguori, G; Liu, C; Liu, C Q; Liu, M Y; Liu, J; Lu, H; Ma, X H; Mancarella, G; Mari, S M; Marsella, G; Martello, D; Mastroianni, S; Meng, X R; Montini, P; Ning, C C; Pagliaro, A; Panareo, M; Perrone, L; Pistilli, P; Qu, X B; Rossi, E; Ruggieri, F; Saggese, L; Salvini, P; Santonico, R; Shen, P R; Sheng, X D; Shi, F; Stanescu, C; Surdo, A; Tan, Y H; Vallania, P; Vernetto, S; Vigorito, C; Wang, B; Wang, H; Wu, C Y; Wu, H R; Yao, Z G; Xu, B; Xue, L; Yan, Y X; Yang, Q Y; Yang, X C; Yuan, A F; Zha, M; Zhang, H M; Zhang, JiLong; Zhang, JianLi; Zhang, L; Zhang, P; Zhang, X Y; Zhang, Y; Zhaxisangzhu,; Zhaxiciren,; Zhou, X X; Zhu, F R; Zhu, Q Q; Zizzi, G

2011-01-01

166

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

167

Hourly average values of solar wing parameters (flow rate and ion temperatures) according to data of measurements of the Venera-9 and Venera-10 automatic interplanetary stations on an Earth-Venus during the period June 1975 - April 1976  

NASA Technical Reports Server (NTRS)

Four electrostatic analyzers with channel electron multipliers as detectors were used to measure solar wind ionic flow. The axes of the fields of vision of two of these analyzers were directed along the axis of the automatic interplanetary station, oriented towards the Sun, while the other two were turned in one plane at angles of +15 deg and -15 deg. The full hemisphere of the angular diagram of each analyzer was approximately 5 deg. The energetic resolution was approximately 6%, and the geometric energy was 0.002 sq cm ave. keV. Each analyzer covered an energetic range of approximately 10 in eight energetic intervals. Spectral distributions were processed in order to obtain the velocity and temperature of the protons. Tabular data show the hour interval (universal time) and the average solar wind velocity in kilometers per second.

Vaysberg, O. L.; Dyachkov, A. V.; Smirnov, V. N.; Tsyrkin, K. B.; Isaeva, R. A.

1980-01-01

168

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

169

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

170

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

NASA Technical Reports Server (NTRS)

The Helios, IMP 8, ISEE 3, ad Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. Previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here it is shown that this evolution is not a solar cycle effect, and that the correlations become even more strongly negative at heliocentric distance larger than 9.5 AU. There is considerable variability in the distributions of the correlations at a given heliocentric distance, but this is not simply related to the solar cycle. Examination of the evolution of correlations between density and speed suggest that most of the structures responsible for evolution in the anticorrelation between n and B are not slow-mode waves, but rather pressure balance structures. The latter consist of both coherent structures such as tangential discontinuities and the more generally pervasive 'pseudosound' which may include the coherent structures as a subset.

Roberts, D. A.

1990-01-01

171

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

172

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

173

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

174

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

175

The interplanetary modulation and transport of Jovian electrons  

NASA Technical Reports Server (NTRS)

Based on simultaneous measurements by Pioneer 11 of the 3-6 MeV Jovian electron flux, interplanetary magnetic field magnitude, and solar wind speed, the interplanetary transport of energetic particles is studied. It is found that corotating interaction regions (CIR's) greatly inhibit electron transport across the average field direction. Cross-field transport is also influenced by the degree of compression of the solar wind since CIR's are areas of compressed solar wind plasma. The propagation of Jovian electrons is studied by a model that includes the effects of CIR's. The model tests whether or not the three-dimensional convection-diffusion theory adequately describes the cross-field transport of electrons. The model is also valid for Jovian electron observations from earth-orbiting satellites. The model may be further applied to 1 AU from the sun where it is found that the cross-field diffusion of electrons explains why Jovian electrons are detected at the earth even during periods when the interplanetary magnetic field does not connect the earth directly to Jupiter.

Conlon, T. F.

1978-01-01

176

Average daily variations in the magnetic field as observed by ATS-5  

NASA Technical Reports Server (NTRS)

Hourly averages of the magnetic field components are determined and analyzed using the measurements of the magnetic field monitor aboard the ATS-5. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.

Skillman, T. L.

1974-01-01

177

Average daily variations in the magnetic field as observed by ATS-5  

NASA Technical Reports Server (NTRS)

Hourly averages of the magnetic field components are determined and analyzed using the measurements, by the magnetic field monitor (MFM) aboard the ATS-5 satellite. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.

Skillman, T. L.

1972-01-01

178

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

179

The average magnetic field draping and consistent plasma properties of the Venus magnetotail  

NASA Technical Reports Server (NTRS)

The detailed average draping pattern of the magnetic field in the deep Venus magnetotail is examined. The variability of the data ordered by spatial location is studied, and the groundwork is laid for developing a coordinate system which measured locations with respect to the tail structures. The reconstruction of the tail in the presence of flapping using a new technique is shown, and the average variations in the field components are examined, including the average field vectors, cross-tail current density distribution, and J x B forces as functions of location across the tail. The average downtail velocity is derived as a function of distance, and a simple model based on the field variations is defined from which the average plasma acceleration is obtained as a function of distance, density, and temperature.

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

1986-01-01

180

Spherical volume averages of static electric and magnetic fields using Coulomb and Biot-Savart laws  

E-print Network

We present derivations of the expressions for the spherical volume averages of static electric and magnetic fields that are virtually identical. These derivations utilize the Coulomb and Biot-Savart laws, and make no use of vector calculus identities or potentials.

Ben Yu-Kuang Hu

2009-01-31

181

Properties of a large-scale interplanetary loop structure as deduced from low-energy proton anisotropy and magnetic field measurements  

NASA Technical Reports Server (NTRS)

Correlated particle and magnetic field measurements by the ISEE 3 spacecraft are presented for the loop structure behind the interplanetary traveling shock event of Nov. 12, 1978. Following the passage of the turbulent shock region, strong bidirectional streaming of low-energy protons is observed for approximately 6 hours, corresponding to a loop thickness of about 0.07 AU. This region is also characterized by a low relative variance of the magnetic field, a depressed proton intensity, and a reduction in the magnetic power spectral density. Using quasi-linear theory applied to a slab model, a value of 3 AU is derived for the mean free path during the passage of the closed loop. It is inferred from this observation that the proton regime associated with the loop structure is experiencing scatter-free transport and that either the length of the loop is approximately 3 AU between the sun and the earth or else the protons are being reflected at both ends of a smaller loop.

Tranquille, C.; Sanderson, T. R.; Marsden, R. G.; Wenzel, K.-P.; Smith, E. J.

1987-01-01

182

The solar wind upstream of Saturn - a comparison of pre- and post-SOI interplanetary magnetic field structure.  

NASA Astrophysics Data System (ADS)

The interplanetary medium upstream of Saturn can have a very strong impact on magnetospheric dynamics. During the declining phase of the solar cycle, the heliosphere is highly structured by Corotating Interaction Regions (CIRs), while this pattern breaks down somewhat closer to solar minimum. We compare Cassini magnetometer data from the cruise to Saturn, and from a period after Saturn Orbit Insertion (SOI) where Cassini had a prolonged excursion into the solar wind. We present the predicted and observed values for the Parker Spiral angle over this long time interval upstream of Saturn and discuss the implications of this. The pre-SOI data encompass an interval where the solar wind was highly disturbed by the "Halloween Storms", a period of extreme solar activity during October/November 2003. The effects of these storms have been widely studied in the vicinity of the Earth, where some of the highest solar wind speeds ever were recorded. We examine how this unusual solar wind evolved by the time it reached Cassini, and discuss the expected magnetospheric response. This is then in turn contrasted with the more typical solar wind conditions, and solar cycle effects taken into account.

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

2007-12-01

183

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

184

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

185

Effects of Interplanetary Transport on SEPs with Differing Charge-to-Mass ratios  

NASA Astrophysics Data System (ADS)

In large SEP events that are well-connected to the observer it is often observed that particles with different charge-to-mass ratios (e.g, O vs. Fe) have different time-intensity histories, and different event-averaged spectral shapes. Several explanations for this behavior have been suggested, such as a sequence of occurrences as an initial “flare” followed by acceleration in a CME-associated interplanetary shock. Another mechanism may be differing responses of ions to waves generated by the streaming SEP protons. In this paper we investigate the possible role of interplanetary transport in such effects by modeling the ion propagation using an advanced numerical transport model in which the particle pitch angle scattering is determined by the turbulence spectrum of the interplanetary magnetic field. Because the turbulence level is a function of particle gyro-frequency, particles with the same speed but different charge-to-mass ratios will sample different portions of the turbulence spectrum and therefore can have different transport histories. We examine sample calculations for O and Fe ions to explore the transport induced effects on time-intensity profiles, spectral shape, and event-averaged abundances for differing levels of interplanetary turbulence. We will compare calculated time-intensity profiles with SEP observations from ACE instruments.

Mason, G. M.; Li, G.; Mewaldt, R. A.; Cohen, C. M.; Leske, R. A.; Desai, M. I.; Dayeh, M. A.; Haggerty, D. K.; Verkhoglyadova, O. P.; Zank, G. P.

2010-12-01

186

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

187

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

188

Turbulent Spectra of Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

We have used a newly developed automated detection algorithm for recognition of interplanetary (IP) shocks which is planned to be implemented on board the future Solar Orbiter mission. We have identified more than 800 IP shocks in the Wind measurements during a prolonged time interval (1995 - 2013) with this algorithm. In order to investigate the magnetic field fluctuations in the IP medium we use the Morlet wavelet transform. The fluxgate magnetometer on-board Wind with a sampling frequency of 10 Hz allows us to analyze both inertial ranges and kinetic scales. We have statistically compared turbulent spectra in upstream and downstream of IP shocks.

Kruparova, Oksana; Krupar, Vratislav; Nemecek, Zdenek; Safrankova, Jana

189

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

190

Geoeffectiveness of High-Speed Streams, Coronal Mass Ejections, and Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

Corotating high-speed solar wind streams, coronal mass ejections, and interplanetary shocks are common causes of geomagnetic storms in Earth's magnetosphere and ionosphere. Epoch analysis is performed for events associated with three types of interplanetary structures during the period of 1995-2003, including 17 events of high-speed streams (HSSs), 18 events of interplanetary shocks followed by complex ejecta, and 18 events of shocks followed by magnetic clouds. It is found that, on average, the HHS events resemble a weak geomagnetic storm with a minimum Dst value of -40 nT. The average behavior of the shock/ejecta and shock/cloud events possess the characteristics of a two-step main phase storm, showing the first dip in the sheath region and the second dip in the following cloud or ejecta. Amongst the 53 events studied there are 8 superstorms with the minimum Dst < -250 nT. Four of them are associated with the sheath region and 4 are associated with either clouds or ejecta, which makes the sheath region as "geoeffective" as magnetic clouds or ejecta in producing superstorms.

Lu, G.

2006-12-01

191

The effects of reflected protons on the plasma environment of the moon for parallel interplanetary magnetic fields  

NASA Astrophysics Data System (ADS)

For the unique case of magnetic field parallel to the solar wind flow, a column of reflected protons can accumulate upstream from the Moon. We investigate observations from the ARTEMIS probes for an extended period with this geometry. During this time, P2 observes strong wave turbulence in two frequency bands above and below the ion cyclotron frequency near the Moon, not seen by P1 farther from the Moon. The lower frequency oscillations prove consistent with kinetic magnetosonic waves resonantly generated by reflected protons, and test particle calculations confirm that a significant column of reflected protons lies upstream when the waves occur. The reflected protons perturb a large volume of plasma around the Moon, extending upstream as well as into the wake. The waves observed near the Moon during this time period have many similarities to those found in the terrestrial foreshock and at comets, suggesting the potential for comparative studies.

Halekas, J. S.; Poppe, A. R.; McFadden, J. P.; Glassmeier, K.-H.

2013-09-01

192

Magnetic field measurements at Jupiter by Voyagers 1 and 2: Daily plots of 48 second averages  

NASA Technical Reports Server (NTRS)

A series of 24 hour summary plots of the magnetic field, in 48-s average form, measured in the vicinity of Jupiter by the magnetometers onboard Voyagers 1 and 2 are presented. The Voyager 1 data cover the period from 27 February 1979 (day = 58) to 23 March (day = 82) inclusive, and the Voyager 2 data cover the period from 2 July 1979 (day = 183) to 14 August (day = 226) inclusive. Closest approach to the planet occurred on days 64 (AT 1205 UT) and 190 (AT 2230 UT) for Voyagers 1 and 2, respectively. Also included are: a description of the characteristics of the magnetometers, a brief description of the near-planet trajectories of the two spacecraft, a listing of the bow shock and magnetopause crossing times, and a bibliography containing Voyager-Jupiter related papers and reports.

Lepping, R. P.; Silverstein, M. J.; Ness, N. F.

1981-01-01

193

Short-term periodicities in interplanetary, geomagnetic and solar phenomena during solar cycle 24  

NASA Astrophysics Data System (ADS)

In this paper we study the quasi-periodic variations of sunspot area/number, 10.7 cm solar radio flux, Average Photospheric Magnetic Flux, interplanetary magnetic field ( B z ) and the geomagnetic activity index A p during the ascending phase of the current solar cycle 24. We use both Lomb-Scargle periodogram and wavelet analysis technique and find evidence for a multitude of quasi-periodic oscillations in all the data sets. In high frequency range (10 days to 100 days), both methods yield similar significance periodicities around 20-35 days and 45-60 days in all data sets. In the case of intermediate range, the significant periods were around 100-130 days, 140-170 days and 180-240 days The Morlet wavelet power spectrum shows that all of the above-mentioned periods are intermittent in nature. We find that the well-known "Rieger period" of (150-160 days) and near Rieger periods (130-190 days) were significant in both solar, interplanetary magnetic field and geomagnetic activity data sets during cycle 24. The geomagnetic activity is the result of the solar wind-magnetosphere interaction. Thus the variations in the detected periodicity in variety of solar, interplanetary and geomagnetic indices could be helpful to improve our knowledge of the inter-relationship between various processes in the Sun-Earth-Heliosphere system.

Chowdhury, Partha; Choudhary, D. P.; Gosain, S.; Moon, Y.-J.

2015-03-01

194

Evolution of interplanetary slow shocks  

SciTech Connect

The possible existence of traveling forward slow shocks, their global geometry and their transition to forward fast shocks have been discussed in a recent paper. The decrease in the Alfven speed at increasing heliocentric distance causes the evolution of a forward slow shock into a forward fast shock. During the transition the shock system consists of a slow shock, a fast shock, and a rotational discontinuity. This paper continues to discuss three aspects about the evolution of interplanetary slow shocks. The authors first presents a survey of slow shock solutions in a three-dimensional A,{theta},{beta} parameter space. Here A=U{sub n}/(a cos {theta}) is the shock Alfven number, U{sub n} the normal component of the relative shock speed, a the Alfven speed, {theta} the acute angle between the shock normal and the magnetic field, and {beta} the ratio of the thermal pressure p to the magnetic pressure B{sup 2}/8{pi}. In a region where the plasma {beta} value is on the order of 1 or greater, the jumps in thermodynamic properties across a slow shock are small but the directional changes for the magnetic field and the relative flow velocity are not necessarily small. On the other hand, in the region where the plasma {beta} value is on the order of 0.1 or less, the jumps of all physical properties across a slow shock may vary over a wide range of magnitudes. Next, the authors discuss that at the onset of the transition process an interplanetary slow shock smoothly converts to a system consisting of a slow shock, a very weak rotational discontinuity (an Alfven wave), and a very weak fast shock (a fast MHD wave). The authors also show that during the transition, the amplitude of fluctuations in flow velocity and magnetic fields are large in the turbulent region behind the fast shock.

Whang, Y.C. (Catholic Univ. of America, Washington, DC (United States))

1988-01-01

195

Control of the Polarity of the Interplanetary Magnetic Field on the Dawn-Dusk Symmetry of the Magnetopause  

NASA Astrophysics Data System (ADS)

The solar wind dynamic pressure is reduced when the solar wind flows around the magnetosphere due to the diversion of the flows. The magnetopause is the boundary where the reduced dynamic pressure is balanced with the magnetic pressure of the compressed magnetosphere by the solar wind. The size and shape of the magnetopause have long been considered among the most important parameters in Solar Terrestrial physics. Previous models of the size and shape of the magnetopause often assumed the axis- symmetry of the magnetopause with respect to the Sun-Earth line. With a large number of magnetopause crossings by ISEE-1 and -2, AMPTE/IRM, Hawkeye, Geotail, Interball-1, and Magion-4, we are able to consider the asymmetry of the magnetopuase. In the Shue et al. [1997] model, the magnetopause was modeled by two parameters, r0 and alpha, representing the subsolar standoff distance and the flaring level of the magnetopause, respectively. Parameter alpha was assumed to be independent of phi in the Shue et al. [1997] model, where phi is the angle between the Z axis and the mapping of the radial vector of the magnetopause on the YZ plane. In the present study we allow alpha to be a function of phi. We separate crossings with different phis and fit them in each bin to the new functional form proposed by Shue et al. [1997]. We find that the magnetopause is symmetric in the dawn-dusk direction for northward IMF. However, its size on the dawnside becomes larger when the IMF is southward. The function of alpha in terms of phi can be combined with the 2-D Shue et al. [1997] model into a 3-D magnetopause model. (Shue, J.-H., J. K. Chao, H. C. Fu, C. T. Russell, P. Song, K. K. Khurana, and H. J. Singer, A new functional form to study the solar wind control of the magnetopause size and shape, J. Geophys. Res., 102, 9497, 1997.)

Shue, J.; Jhuang, B.; Song, P.; Safrankova, J.; Nemecek, Z.; Russell, C. T.; Chen, S.

2008-12-01

196

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

197

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

198

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.

199

Elevated residential exposure to power frequency magnetic field associated with greater average age at diagnosis for patients with brain tumors.  

PubMed

To explore whether the age at cancer diagnosis was associated with residential exposure to magnetic field, we compared average ages at diagnosis for cases of leukemia, brain tumor, or female breast cancer with elevated exposure (magnetic flux density >or= 0.2 microT, or residential distance from major power lines average ages at diagnosis for cancer cases with same diagnoses but with a background exposure (< 0.2 microT or > 100 m from major power lines). Comparing with brain tumor cases with background magnetic field exposure (n = 506), brain tumor cases with elevated exposure (n = 71) were 6 years older on average at diagnosis (P = 0.01). The difference was greater for males (45.2 vs. 52.1 years, P = 0.01) than for females (44.3 vs. 48.2 years, P = 0.27). No such phenomena at a significant level was observed for leukemia, female breast cancer, or a random sample of general population. We noted an association between magnetic field exposure and a greater mean age at diagnosis for brain tumors. Whether or not these phenomena suggest a delayed occurrence of brain tumors following a higher than background residential magnetic field exposure deserves further investigation. PMID:12669307

Li, Chung-Yi; Lin, Ruey S; Sung, Fung-Chang

2003-04-01

200

Interplanetary Field Enhancements: The Interaction between Solar Wind and Interplanetary Dusty Plasma Released by Interplanetary Collisions  

NASA Astrophysics Data System (ADS)

Interplanetary field enhancements (IFEs) are unique large-scale structures in the solar wind. During IFEs, the magnetic-field strength is significantly enhanced with little perturbation in the solar-wind plasma. Early studies showed that IFEs move at nearly the solar-wind speed and some IFEs detected at 0.72AU by Pioneer Venus Orbiter (PVO) are associated with material co-orbiting with asteroid Oljato. To explain the observed IFE features, we develop and test an IFE formation hypothesis: IFEs result from interactions between the solar wind and clouds of nanoscale charged dust particles released in interplanetary collisions. This hypothesis predicts that the magnetic field drapes and the solar wind slows down in the upstream. Meanwhile the observed IFE occurrence rate should be comparable with the detectable interplanetary collision rate. Based on this hypothesis, we can use the IFE occurrence to determine the spatial distribution and temporal variation of interplanetary objects which produce IFEs. To test the hypothesis, we perform a systematic survey of IFEs in the magnetic-field data from many spacecraft. Our datasets cover from 1970s to present and from inner than 0.3AU to outer than 5 AU. In total, more than 470 IFEs are identified and their occurrences show clustering features in both space and time. We use multi-spacecraft simultaneous observations to reconstruct the magnetic-field geometry and find that the magnetic field drapes in the upstream region. The results of a superposed epoch study show that the solar wind slows down in the upstream and there is a plasma depletion region near the IFE centers. In addition, the solar-wind slowdown and plasma depletion feature are more significant in larger IFEs. The mass contained in IFEs can be estimated by balancing the solar-wind pressure force exerted on the IFEs against the solar gravity. The solar-wind slowdown resultant from the estimated mass is consistent with the result in superposed epoch study. The interplanetary collision rate is estimated based on the flux model of Ceplecha [1992] and collision model of Grun [et al., 1985]. A debris distribution model of Fujiwara [et al., 1977] is modified to estimate the mass carried by nanoscale dust particles. The integrated collision rate inside a detectable volume, which is a truncated cone starting from 0.2AU, is used to compare with the observed IFE rate. At 1AU, we find that in the same mass range, the two rates are comparable. Inside 1AU, both rates increase slowly as the heliocentric distance increases. We reanalyze the PVO observations and confirm the association between IFEs and co-orbiting material of asteroid 2201 Oljato. An analogous study is performed at 1AU and we find that material co-orbiting with asteroid 138175 produces many IFEs there. We then compare the earlier PVO observations with the present Venus Express (VEX) observation and find that the IFE production rate of the material co-orbiting with Oljato has decreased in the past three decades. A comparison between earlier IMP 8 observations and current observations shows a similar decrease in the rate of IFEs associated with asteroid 138175. Such a rate decrease can be explained by the gravitational scattering of co-orbiting material accompanying both asteroids, as they make occasional close passes of the Earth and Venus. Simulations show that due to the gravitational perturbations from the Earth and Venus, gaps can be formed in the otherwise continuous debris trails in periods of decades [Connors et al.,2014a]. The importance of this IFE study is discussed in this thesis. We now have a better understanding of a previous mysterious phenomenon, sufficient to use the IFE occurrence to identify small interplanetary objects. Material of tens of meters across co-orbiting with near-Earth objects is too small to detect by traditional survey methods, but still can cause great property and civilian damage once it enters the Earth's atmosphere. In addition, due to gravitational perturbations, the co-orbiting material can be spread along and across the orbits of t

Lai, Hairong

201

Multi-Spacecraft Observations of Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

Using multi-spacecraft observations primarily from ACE and WIND and from IMP 8 and Geotail when available, the 3-dimensional structure of interplanetary shocks on the hundred Earth radii scale will be discussed. The complete magnetic field, and solar wind ion and electron data sets were used to fit the shocks with a full non-linear least squares fitting "Rankine-Hugoniot" technique yielding the local shock surface normals and speeds with associated uncertainties. Multi-spacecraft results reveal that on the distance scale of ACE's L1 halo orbit the shocks deviate from a simple planar geometry. This result has important consequences for the prediction of the exact arrival times of interplanetary shocks at the Earth's magnetosphere, and hence, on the reliability of space weather predictions. It also has implications on the coherence scale of solar wind structures and their evolution from the Sun to Earth.

Smith, C. W.; Tokar, R. L.; Skoug, R. M.; Szabo, A.

1999-01-01

202

Multi-Spacecraft Observations of Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

Using multi-spacecraft observations primarily from ACE and WIND, and from IMP 8 and Geotail when available, the 3-dimensional structure of interplanetary shocks on the hundred Earth radii scale will be discussed. The complete magnetic field, and solar wind ion and electron data sets were used to fit the shocks with a full non-linear least squares fit "Rankine-Hugoniot" technique yielding the local shock surface normals and speeds with associated uncertainties. Multi-spacecraft results reveal that on the distance scale of ACE's L1 halo orbit the shocks deviate significantly from a simple planar geometry. This result has important consequences for the prediction of the exact arrival times of interplanetary shocks at the Earth's magnetosphere, and hence, on the reliability of space weather predictions. It also has implications on the coherence scale of solar wind structures and their evolution from the Sun to Earth.

Szabo, A.; Smith, C. W.; Tokar, R. L.; Skoug, R. M.

1999-01-01

203

Gone with the solar wind: A study of protons accelerated by interplanetary shocks  

Microsoft Academic Search

The availability of high time resolution spacecraft data has made possible in-situ and detailed study of plasma processes in the interplanetary medium. One important process that has received a lot of attention is the energization of charged particles due to the interaction with traveling interplanetary shock waves. The specific goal is to make use of observed magnetic fields, plasma density

Ramona Louise Kessel

1987-01-01

204

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

205

Effect of the solar wind and interplanetary magnetic field parameter variations to the enhancement and dynamics of auroral electrojet during superstrong magnetic storms  

NASA Astrophysics Data System (ADS)

According to the global ground geomagnetic observations in the six meridian chains and analysis of satellite measurements the auroral elektrojet features at various conditions in the solar wind (SW) and the IMF: during a sharp rise of dynamic pressure up to 15-60 nPa and variations in the intensity and sign of the IMF Bz-component to -40 --50 nT. The data obtained during super strong magnetic storms of October 29-30, 2003, November 20-21, 2003, November 07-08, 2004 and November 09-10, 2004 (Dst = -300 --400 nT) are analysed. The following scientific results are obtained: • It is shown that a sharp increase of the SW dynamic pressure (Pd) and the excitation of a sudden impulse (SC) during IMF Bz negative (Bz<0) leads to a simultaneous (with accuracy 1-3 min) increase of DP2 current system and the intensity of the western elec-trojet (Jw) in a broad sector of longitudes and expansion of Jw to the pole up to the polar cap latitudes with the velocity of VN = 1-3 km/s. • It is found that during the sharp rise of Pd up to 60 nPa for IMF Bz positive (Bz>0) 35 nT is the amplification of eastward magnetopause currents and DP2 current system are observed. Strengthening and dynamics of the westward electrojet is not observed. • We find that during periods of intensity growth of negative values of IMF Bz to -50 nT within a few hours there is a shift of the centers of auroral electrojet to the equator up to latitudes about 10-20 degrees along the meridian with a speed of 1-4 km/s with a simultaneous amplifications of Jw repeated in 1-2 hours with a duration of 1-2 hours at latitudes from low to auroral latitudes and with a possible extension to electrojets up to the polar cap latitudes and the abrupt extension of the subsequent Jw electrojets localization region by azimuth. • It is shown that after the electrojet displacement to the equator during southward direc-tion of IMF Bz and enhancement of the SW electric field the IMF Bz turning to the north accompanied by the poleward expansion of Jw electrojet at a speed of 1 km/s in a wide range of longitudes is observed. • It is found that the electrojet expansion to the pole during superstorms often occurs up to the polar cap latitudes due to the extension of the precipitating particles and increased ionospheric conductivity region from the low and auroral latitudes, but not due to the movement of localized westward electrojet along the meridian, as is the case in the substorm. The report discusses the possible causes of the dynamics of auroral electrojets under different geophysical conditions. This work was supported by the Presidium of the Russian Academy of Sciences (program 16, part 3), by the RFBR grant No.09-05-98546 and also supported by the SB RAS project No.69.

Solovyev, Stepan; Boroev, Roman; Moiseyev, Alexey; Du, Aimin; Yumoto, Kiyohumi

206

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

207

ULYSSES out-of-ecliptic observations of interplanetary shocks  

Microsoft Academic Search

Interplanetary shocks observed at the Ulysses spacecraft as it traveled from the ecliptic plane to the southern solar pole have been identified and analyzed using both magnetic field and plasma measurements. The latitude dependences of various parameters associated with the shocks (beta, theta_BN_ and Mach number) have been investigated. The direction of shock propagation of forward and reverse corotating shocks

M. E. Burton; E. J. Smith; A. Balogh; R. J. Forsyth; S. J. Bame; J. L. Phillips; B. E. Goldstein

1996-01-01

208

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

209

Laser-fusion rocket for interplanetary propulsion  

SciTech Connect

A rocket powered by fusion microexplosions is well suited for quick interplanetary travel. Fusion pellets are sequentially injected into a magnetic thrust chamber. There, focused energy from a fusion Driver is used to implode and ignite them. Upon exploding, the plasma debris expands into the surrounding magnetic field and is redirected by it, producing thrust. This paper discusses the desired features and operation of the fusion pellet, its Driver, and magnetic thrust chamber. A rocket design is presented which uses slightly tritium-enriched deuterium as the fusion fuel, a high temperature KrF laser as the Driver, and a thrust chamber consisting of a single superconducting current loop protected from the pellet by a radiation shield. This rocket can be operated with a power-to-mass ratio of 110 W gm/sup -1/, which permits missions ranging from occasional 9 day VIP service to Mars, to routine 1 year, 1500 ton, Plutonian cargo runs.

Hyde, R.A.

1983-09-27

210

Autonomous interplanetary constellation design  

NASA Astrophysics Data System (ADS)

According to NASA's integrated space technology roadmaps, space-based infrastructures are envisioned as necessary ingredients to a sustained effort in continuing space exploration. Whether it be for extra-terrestrial habitats, roving/cargo vehicles, or space tourism, autonomous space networks will provide a vital communications lifeline for both future robotic and human missions alike. Projecting that the Moon will be a bustling hub of activity within a few decades, a near-term opportunity for in-situ infrastructure development is within reach. This dissertation addresses the anticipated need for in-space infrastructure by investigating a general design methodology for autonomous interplanetary constellations; to illustrate the theory, this manuscript presents results from an application to the Earth-Moon neighborhood. The constellation design methodology is formulated as an optimization problem, involving a trajectory design step followed by a spacecraft placement sequence. Modeling the dynamics as a restricted 3-body problem, the investigated design space consists of families of periodic orbits which play host to the constellations, punctuated by arrangements of spacecraft autonomously guided by a navigation strategy called LiAISON (Linked Autonomous Interplanetary Satellite Orbit Navigation). Instead of more traditional exhaustive search methods, a numerical continuation approach is implemented to map the admissible configuration space. In particular, Keller's pseudo-arclength technique is used to follow folding/bifurcating solution manifolds, which are otherwise inaccessible with other parameter continuation schemes. A succinct characterization of the underlying structure of the local, as well as global, extrema is thus achievable with little a priori intuition of the solution space. Furthermore, the proposed design methodology offers benefits in computation speed plus the ability to handle mildly stochastic systems. An application of the constellation design methodology to the restricted Earth-Moon system, reveals optimal pairwise configurations for various L1, L2, and L5 (halo, axial, and vertical) periodic orbit families. Navigation accuracies, ranging from O (10+/-1) meters in position space, are obtained for the optimal Earth-Moon constellations, given measurement noise on the order of 1 meter.

Chow, Cornelius Channing, II

211

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

212

Proceedings of the Symposium on the Study of the Sun and Interplanetary Medium in Three Dimensions. [space mission planning and interplanetary trajectories by NASA and ESA to better observe the sun and solar system  

NASA Technical Reports Server (NTRS)

A series of papers are presented from a symposium attended by over 200 European and American scientists to examine the importance of exploring the interplanetary medium and the sun by out-of-the-ecliptic space missions. The likely scientific returns of these missions in the areas of solar, interplanetary, and cosmic ray physics is examined. Theoretical models of the solar wind and its interaction with interplanetary magnetic fields are given.

Fisk, L. A. (editor); Axford, W. I. (editor)

1976-01-01

213

Interplanetary Microlaser Transponders  

NASA Technical Reports Server (NTRS)

The feasibility of an asynchronous (i.e. independently firing) interplanetary laser transponder, capable of ranging between Earth and Mars and using the automated SLR2000 Satellite Laser Ranging (SLR) system as an Earth base station, has been suggested. Since that time, we have received a small amount of discretionary funding to further explore the transponder concept and to develop and test an engineering breadboard. Candidate operational scenarios for acquiring and tracking the opposite laser terminal over interplanetary distances have been developed, and breadboard engineering parameters were chosen to reflect the requirements of an Earth-Mars link Laboratory tests have been devised to simulate the Earth- Mars link between two independent SLR2000 transceivers and to demonstrate the transfer of range and time in single photon mode. The present paper reviews the concept of the asynchronous microlaser transponder, the transponder breadboard design, an operational scenario recently developed for an asteroid rendezvous, and the laboratory test setup. The optical head of the transponder breadboard fits within a cylinder roughly 15 cm in diameter and 32 cm in length and is mounted in a commercial two axis gimbal driven by two computer-controlled stepper motors which allows the receiver optical axis to be centered on a simulated Earth image. The optical head is built around a small optical bench which supports a 14.7 cm diameter refractive telescope, a prototype 2 kHz SLR2000 microlaser transmitter, a quadrant microchannel plate photomultiplier (MCP/PMT), a CCD array camera, spatial and spectral filters, assorted lenses and mirrors, and protective covers and sun shields. The microlaser is end-pumped by a fiber-coupled diode laser array. An annular mirror is employed as a passive transmit/receive (T/R) switch in an aperture-sharing arrangement wherein the transmitted beam passes through the central hole and illuminates only the central 2.5 cm of the common telescope (adequate to achieve a 10 arcsecond full laser beam divergence) while the receiver uses the remainder of the 14.7 cm aperture. Additional electronic instrumentation includes the diode pump array and associated heat sink and current drivers, rubidium frequency standard, timing distribution module, range gate generator, a recently developed all-digital correlation range receiver, and system computer. Acquisition of the opposite transponder terminal requires a search within a three-dimensional volume determined by the initial pointing uncertainty and a maximum 500 microsecond uncertainty in the laser time of fire at the opposite terminal for totally uncorrelated Earth and spacecraft clocks. The angular search is aided by a sensitive CCD array capable of imaging the Earth, Moon, and surrounding stars within the nominal + 0.5 degree cone of uncertainty associated with the initial pointing of a spacecraft body or microwave communications dish.

Degnan, John J.

1999-01-01

214

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

215

Multi-Spacecraft Observations of Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

Multi-spacecraft solar wind observations reveal that many interplanetary shocks deviate significantly from exact planarity on scale length of the magnetospheric cross section. A number of different IP shock observations with four spacecraft will be presented to demonstrate quantitatively the angular deviations between shock normals obtained from 4-spacecraft methods, using only the time and position information of shock observations but assuming a exactly planar geometry, and those obtained from a non-linear least squares fitting of the "Rankine-Hugoniot" conservation equations at each spacecraft. Moreover, the curvature of the shock fronts is strongly related to its driver, typically magnetic clouds. It will be demonstrated that small and slower moving magnetic clouds drive shocks with significantly more irregular surface geometries.

Szabo, Adam

2005-01-01

216

An In Vivo Three-Dimensional Magnetic Resonance Imaging-Based Averaged Brain Collection of the Neonatal Piglet (Sus scrofa)  

PubMed Central

Due to the fact that morphology and perinatal growth of the piglet brain is similar to humans, use of the piglet as a translational animal model for neurodevelopmental studies is increasing. Magnetic resonance imaging (MRI) can be a powerful tool to study neurodevelopment in piglets, but many of the MRI resources have been produced for adult humans. Here, we present an average in vivo MRI-based atlas specific for the 4-week-old piglet. In addition, we have developed probabilistic tissue classification maps. These tools can be used with brain mapping software packages (e.g. SPM and FSL) to aid in voxel-based morphometry and image analysis techniques. The atlas enables efficient study of neurodevelopment in a highly tractable translational animal with brain growth and development similar to humans. PMID:25254955

Conrad, Matthew S.; Sutton, Bradley P.; Dilger, Ryan N.; Johnson, Rodney W.

2014-01-01

217

An in vivo three-dimensional magnetic resonance imaging-based averaged brain collection of the neonatal piglet (Sus scrofa).  

PubMed

Due to the fact that morphology and perinatal growth of the piglet brain is similar to humans, use of the piglet as a translational animal model for neurodevelopmental studies is increasing. Magnetic resonance imaging (MRI) can be a powerful tool to study neurodevelopment in piglets, but many of the MRI resources have been produced for adult humans. Here, we present an average in vivo MRI-based atlas specific for the 4-week-old piglet. In addition, we have developed probabilistic tissue classification maps. These tools can be used with brain mapping software packages (e.g. SPM and FSL) to aid in voxel-based morphometry and image analysis techniques. The atlas enables efficient study of neurodevelopment in a highly tractable translational animal with brain growth and development similar to humans. PMID:25254955

Conrad, Matthew S; Sutton, Bradley P; Dilger, Ryan N; Johnson, Rodney W

2014-01-01

218

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

NASA Astrophysics Data System (ADS)

The fast coronal mass ejection (CME) on 23 July 2012 caused attention because of its extremely short transit time from the Sun to 1 AU, which was shorter 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 measured the 3D kinematics of the CME using the graduated cylindrical shell model and obtained a maximum speed of 2580±280 km s-1 for the CME shock and 2270±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, the ambient flow speed needs to have an average value close to the slow solar wind speed (450 km s-1), and the initial shock speed at a distance of 30 R ? should not exceed ? 2300 km s-1, otherwise it would arrive much too early at STEREO-A. The model results indicate that an extremely small aerodynamic drag force is exerted on the shock, smaller by one order of magnitude than 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 the density of the ambient solar wind flow, in which the fast CME propagates, is decreased to ? sw=1 - 2 cm-3 at the distance of 1 AU. This result is consistent with the preconditioning of interplanetary space by a previous CME.

Temmer, M.; Nitta, N. V.

2015-03-01

219

Adaptive interplanetary orbit determination  

NASA Astrophysics Data System (ADS)

This work documents the development of a real-time interplanetary orbit determination monitoring algorithm for detecting and identifying changes in the spacecraft dynamic and measurement environments. The algorithm may either be utilized in a stand-alone fashion as a spacecraft monitor and hypothesis tester by navigators or may serve as a component in an autonomous adaptive orbit determination architecture. In either application, the monitoring algorithm serves to identify the orbit determination filter parameters to be modified by an offline process to restore the operational model accuracy when the spacecraft environment changes unexpectedly. The monitoring algorithm utilizes a hierarchical mixture-of-experts to regulate a multilevel bank organization of extended Kalman filters. Banks of filters operate on the hierarchy top-level and are composed of filters with configurations representative of a specific environment change called a macromode. Fine differences, or micromodes, within the macromodes are represented by individual filter configurations. Regulation is provided by two levels of single-layer neural networks called gating networks. A single top-level gating network regulates the weighting among macromodes and each bank uses a gating network to regulate member filters internally. Experiments are conducted on the Mars Pathfinder cruise trajectory environment using range and Doppler data from the Deep Space Network. The experiments investigate the ability of the hierarchical mixture-of-experts to identify three environment macromodes: (1) unmodeled impulsive maneuvers, (2) changes in the solar radiation pressure dynamics, and (3) changes in the measurement noise strength. Two methods of initializing the gating networks are examined in each experiment. One method gives the neurons associated with all filters equivalent synaptic weight. The other method places greater weight on the operational filter initially believed to model the spacecraft environment. The results will show that the equal synaptic weight initialization method is superior to the one favoring the operational filter and that processing range and Doppler data together is superior to processing Doppler data alone. When processing range and Doppler with an equally initialized hierarchy, all three macromodes are definitively identified by the top-level gating network weights. Additionally, in the case of multiple successive macromode changes, the hierarchy is generally able to recover from one macromode and identify a change to another macromode.

Crain, Timothy Price

220

CAWSES November 7–8, 2004, superstorm: Complex solar and interplanetary features in the post-solar maximum phase  

Microsoft Academic Search

The complex interplanetary structures during 7 to 8 Nov 2004 are analyzed to identify their properties as well as resultant geomagnetic effects and the solar origins. Three fast forward shocks, three directional discontinuities and two reverse waves were detected and analyzed in detail. The three fast forward shocks “pump” up the interplanetary magnetic field from a value of ?4 nT

Bruce T. Tsurutani; Ezequiel Echer; Fernando L. Guarnieri; J. U. Kozyra

2008-01-01

221

Information processing for interplanetary exploration  

Microsoft Academic Search

Payload limitations, environmental constraints, ignorance of the relevant human factors, cost and the generally hazardous conditions surrounding manned vehicles in interplanetary space have combined to elect machines as the probable predecessors of men in the exploration of the Solar System. This, of course, is not to deny that man will soon follow--we may rest assured that he will. Indeed, manned

T. B. Steel Jr.

1962-01-01

222

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

223

Interplanetary circumstances of quasi-perpendicular interplanetary shocks in 1996-2005  

NASA Astrophysics Data System (ADS)

The angle ($\\theta$Bn) between the normal to an interplanetary shock front and the upstream magnetic field direction, though often thought of as a property “of the shock,” is also determined by the configuration of the magnetic field immediately upstream of the shock. We investigate the interplanetary circumstances of 105 near-Earth quasi-perpendicular shocks during 1996-2005 identified by $\\theta$Bn ? 80° and/or by evidence of shock drift particle acceleration. Around 87% of these shocks were driven by interplanetary coronal mass ejections (ICMEs); the remainder were probably the forward shocks of corotating interaction regions. For around half of the shocks, the upstream field was approximately perpendicular to the radial direction, either east-west or west-east or highly inclined to the ecliptic. Such field directions will give quasi-perpendicular configurations for radially propagating shocks. Around 30% of the shocks were propagating through, or closely followed, ICMEs at the time of observation. Another quarter were propagating through the heliospheric plasma sheet (HPS), and a further quarter occurred in slow solar wind that did not have characteristics of the HPS. Around 11% were observed in high-speed streams, and 7% in the sheaths following other shocks. The fraction of shocks found in high-speed streams is around a third of that expected based on the fraction of the time when such streams were observed at Earth. Quasi-perpendicular shocks are found traveling through ICMEs around 2-3 times more frequently than expected. In addition, shocks propagating through ICMEs are more likely to have larger values of $\\theta$Bn than shocks outside ICMEs.

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

2010-07-01

224

Interplanetary Circumstances of Quasi-Perpendicular Interplanetary Shocks in 1996-2005  

NASA Technical Reports Server (NTRS)

The angle (theta(sub Bn)) between the normal to an interplanetary shock front and the upstream magnetic field direction, though often thought of as a property "of the shock," is also determined by the configuration of the magnetic field immediately upstream of the shock. We investigate the interplanetary circumstances of 105 near-Earth quasi-perpendicular shocks during 1996-2005 identified by theta(sub Bn) greater than or equal to 80 degrees and/or by evidence of shock drift particle acceleration. Around 87% of these shocks were driven by interplanetary coronal mass ejections (ICMEs); the remainder were probably the forward shocks of corotating interaction regions. For around half of the shocks, the upstream field was approximately perpendicular to the radial direction, either east-west or west-east or highly inclined to the ecliptic. Such field directions will give quasi-perpendicular configurations for radially propagating shocks. Around 30% of the shocks were propagating through, or closely followed, ICMEs at the time of observation. Another quarter were propagating through the heliospheric plasma sheet (HPS), and a further quarter occurred in slow solar wind that did not have characteristics of the HPS. Around 11% were observed in high-speed streams, and 7% in the sheaths following other shocks. The fraction of shocks found in high-speed streams is around a third of that expected based on the fraction of the time when such streams were observed at Earth. Quasi-perpendicular shocks are found traveling through ICMEs around 2-3 times more frequently than expected. In addition, shocks propagating through ICMEs are more likely to have larger values of theta(sub Bn) than shocks outside ICMEs.

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

2010-01-01

225

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

226

Plasma wave levels and IMF orientations preceding observations of interplanetary shocks by ISEE-3  

Microsoft Academic Search

Some interplanetary shocks detected by ISEE-3 are preceded by many hours of strongly-enhanced plasma wave noise at a few kHz, while others have essentially no wave precursors above background. It has been shown that these extremes correspond to quasi-parallel and quasi-perpendicular shocks, respectively, based on the instantaneous orientation angle theta\\/sub B\\/n of the interplanetary magnetic field (IMF) to the shock

E. W. Greenstadt; F.L. Scarf; C. F. Kennel; E. J. Smith; R. W. Fredricks

1982-01-01

227

Plasma wave levels and IMF orientations preceding observations of interplanetary shocks by ISEE-3  

Microsoft Academic Search

Some interplanetary shocks detected by ISEE-3 are preceded by many hours of strongly enhanced plasma wave noise at a few kHz, while others have essentially no wave precursors above background. It has been shown that these extremes correspond to quasi-parallel and quasi-perpendicular shocks, respectively, based on the instantaneous orientation angle of the interplanetary magnetic field (IMF) to the shock normal

E. W. Greenstadt; F. L. Scarf; R. W. Fredricks; C. F. Kennel; E. J. Smith

1982-01-01

228

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

229

Interplanetary sector boundaries 1971-1973  

NASA Technical Reports Server (NTRS)

The large-scale morphology and internal structure of sector boundaries (SB) are investigated, using observations at 1 AU of interplanetary SB crossings. It was found that the durations of the SBs were either relatively short (less than about 10 min) or relatively long (longer than about 3 hours). Using the minimum variance technique, it was found that the SB surfaces were inclined appreciably with respect to the ecliptic at this epoch of the solar cycle (1971-1973). Magnetic holes were found in thick SBs at a rate about three times that elsewhere. In addition, an analysis of tangential discontinuities showed that their orientations were generally not related to the orientations of the SB surface, but their characteristics were very similar to those for discontinuities outside the SBs.

Klein, L.; Burlaga, L. F.

1980-01-01

230

Interplanetary Dust Particles  

NASA Astrophysics Data System (ADS)

One of the fundamental goals of the study of meteorites is to understand how the solar system and planetary systems around other stars formed. It is known that the solar system formed from pre-existing (presolar) interstellar dust grains and gas. The grains originally formed in the circumstellar outflows of other stars. They were modified to various degrees, ranging from negligible modification to complete destruction and reformation during their ˜108 yr lifetimes in the interstellar medium (ISM) (Seab, 1987; Mathis, 1993). Finally, they were incorporated into the solar system. Submicrometer-sized silicates and carbonaceous material are believed to be the most common grains in the ISM ( Mathis, 1993; Sandford, 1996), but it is not known how much of this presolar particulate matter was incorporated into the solar system, to what extent it has survived, and how it might be distinguished from solar system grains. In order to better understand the process of solar system formation, it is important to identify and analyze these solid grains. Since all of the alteration processes that modified solids in the solar nebula presumably had strong radial gradients, the logical place to find presolar grains is in small primitive bodies like comets and asteroids that have undergone little, if any, parent-body alteration.Trace quantities of refractory presolar grains (e.g., SiC and Al2O3) survive in the matrices of the most primitive carbon-rich chondritic meteorites (Anders and Zinner, 1993; Bernatowicz and Zinner, 1996; Bernatowicz and Walker, 1997; Hoppe and Zinner, 2000; see Chapter 1.02). Chondritic meteorites are believed to be from the asteroid belt, a narrow region between 2.5 and 3.5 astronomical units (AU) that marks the transition from the terrestrial planets to the giant gas-rich planets. The spectral properties of the asteroids suggest a gradation in properties with some inner and main belt C and S asteroids (the source region of most meteorites and polar micrometeorites) containing layer silicates indicative of parent-body aqueous alteration and the more distant anhydrous P and D asteroids exhibiting no evidence of (aqueous) alteration (Gradie and Tedesco, 1982). This gradation in spectral properties presumably extends several hundred AU out to the Kuiper belt, the source region of most short-period comets, where the distinction between comets and outer asteroids may simply be one of the orbital parameters ( Luu, 1993; Brownlee, 1994; Jessberger et al., 2001). The mineralogy and petrography of meteorites provides direct confirmation of aqueous alteration, melting, fractionation, and thermal metamorphism among the inner asteroids ( Zolensky and McSween, 1988; Farinella et al., 1993; Brearley and Jones, 1998). Because the most common grains in the ISM (silicates and carbonaceous matter) are not as refractory as those found in meteorites, it is unlikely that they have survived in significant quantities in meteorites. Despite a prolonged search, not a single presolar silicate grain has yet been identified in any meteorite.Interplanetary dust particles (IDPs) are the smallest and most fine-grained meteoritic objects available for laboratory investigation (Figure 1). In contrast to meteorites, IDPs are derived from a broad range of dust-producing bodies extending from the inner main belt of the asteroids to the Kuiper belt (Flynn, 1996, 1990; Dermott et al., 1994; Liou et al., 1996). After release from their asteroidal or cometary parent bodies the orbits of IDPs evolve by Poynting-Robertson (PR) drag (the combined influence of light pressure and radiation drag) ( Dermott et al., 2001). Irrespective of the location of their parent bodies nearly all IDPs under the influence of PR drag can eventually reach Earth-crossing orbits. IDPs are collected in the stratosphere at 20-25 km altitude using NASA ER2 aircraft ( Sandford, 1987; Warren and Zolensky, 1994). Laboratory measurements of implanted rare gases, solar flare tracks ( Figure 2), and isotope abundances have confirmed that the collected particles are indeed extraterrestrial

Bradley, J. P.

2003-12-01

231

Global three-dimensional MHD simulation of a space weather event: CME formation, interplanetary propagation, and interaction with the magnetosphere  

NASA Astrophysics Data System (ADS)

A parallel adaptive mesh refinement (AMR) finite-volume scheme for predicting ideal MHD flows is used to simulate the initiation, structure, and evolution of a coronal mass ejection (CME) and its interaction with the magnetosphere-ionosphere system. The simulated CME is driven by a local plasma density enhancement on the solar surface with the background initial state of the corona and solar wind represented by a newly devised ``steady state'' solution. The initial solution has been constructed to provide a reasonable description of the time-averaged solar wind for conditions near solar minimum: (1) the computed magnetic field near the Sun possesses high-latitude polar coronal holes, closed magnetic field flux tubes at low latitudes, and a helmet streamer structure with a neutral line and current sheet; (2) the Archimedean spiral topology of the interplanetary magnetic field is reproduced; (3) the observed two-state nature of the solar wind is also reproduced with the simulation yielding fast and slow solar wind streams at high and low latitudes, respectively; and (4) the predicted solar wind plasma properties at 1 AU are consistent with observations. Starting with the generation of a CME at the Sun, the simulation follows the evolution of the solar wind disturbance as it evolves into a magnetic cloud and travels through interplanetary space and subsequently interacts with the terrestrial magnetosphere-ionosphere system. The density-driven CME exhibits a two-step release process, with the front of the CME rapidly accelerating following the disruption of the near-Sun closed magnetic field line structure and then moving at a nearly constant speed of ~560 km/s through interplanetary space. The CME also produces a large magnetic cloud (>100RS across) characterized by a magnetic field that smoothly rotates northward and then back again over a period of ~2 days at 1 AU. The cloud does not contain a sustained period with a strong southward component of the magnetic field, and, as a consequence, the simulated CME is somewhat ineffective in generating strong geo-magnetic activity at Earth. Nevertheless, the simulation results illustrate the potential, as well as current limitations, of the MHD-based space weather model for enhancing the understanding of coronal physics, solar wind plasma processes, magnetospheric physics, and space weather phenomena. Such models will provide the foundation for future, more comprehensive space weather prediction tools.

Groth, Clinton P. T.; De Zeeuw, Darren L.; Gombosi, Tamas I.; Powell, Kenneth G.

2000-11-01

232

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

233

Interplanetary origin of multiple-dip geomagnetic storms  

Microsoft Academic Search

In this paper, we have systematically investigated the interplanetary drivers of major dips during intense (Dst ? ?100 nT) geomagnetic storms in 1996–2006. A major dip is defined as a temporary decrease in Dst index with amplitude larger than 14.5 nT. Multiple dips result in a storm if regions of geoeffective solar wind with strong southward magnetic fields are separated

J. Zhang; I. G. Richardson; D. F. Webb

2008-01-01

234

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

235

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

NASA Astrophysics Data System (ADS)

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 ? 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 Ivpropr -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 sheath and the mass of plasma at that position M sheath can be inferred from the polarization of the shock-associated enhancement in WL radiance. From the FR measurements, the local B ?sheath at r 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; Davies, Jackie A.; Feng, Xueshang; Owens, Mathew J.; Harrison, Richard A.; Davis, Chris J.; Liu, Ying D.

2013-11-01

236

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

237

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

238

Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

239

On Relation of the Rigidity Spectrum of 11-YEAR Variation of the Galactic Cosmic Ray Intensity and the Interplanetary Magnetic Field Turbulence  

NASA Astrophysics Data System (ADS)

We use data of neutron monitors and IMF components Bx, By and Bz to study a dependence of the rigidity spectrum exponent gamma (deltaD(R)/D(R)=AR (-gamma) ) of the Galactic Cosmic Rays (GCR) intensity variations on IMF turbulence, characterized by the exponent ? of the power spectral density (PSD) of the IMF turbulence (PSD =af (-nu) , f is frequency). A high inversely correlations between temporal changes of (gamma and nu _{x}), (gamma and nu _{y}), and (gamma and nu _{z}) observed in 1977-1989 (A>0) do not depend whether the nu _{x} , nu _{y} and nu _{z} are calculated for alternated of resonant frequency of the IMF turbulence versus solar activity or for constant B and V _{sw} corresponding to average resonant frequency range responsible for scattering of GCR particles to which neutron monitors respond; consequently, nu _{x} , nu _{y} and nu _{z} are basically unchangeable when a range of frequency Deltaf=3x10 (-6) Hz is sliding versus time corresponding to the changes of resonant frequency of the IMF’s turbulence during 1977-1989. At the same time for the solar cycles 20 and 22 a clear inverse correlation between gamma and nu _{y} takes place for shifted frequency range versus solar activity corresponding to the alternation of resonant frequencies of turbulence of the IMF. For A<0 epochs a dependence of gamma upon nu _{y}is sharp comparing with A>0 epochs. Similar relationship is observed for regression of (gamma on nu _{z}) and (gamma on nu _{x})

Iskra, Krzysztof; Siluszyk, Marek

240

THREE-DIMENSIONAL FEATURES OF THE OUTER HELIOSPHERE DUE TO COUPLING BETWEEN THE INTERSTELLAR AND INTERPLANETARY MAGNETIC FIELDS. IV. SOLAR CYCLE MODEL BASED ON ULYSSES OBSERVATIONS  

SciTech Connect

The solar cycle has a profound influence on the solar wind (SW) interaction with the local interstellar medium (LISM) on more than one timescales. Also, there are substantial differences in individual solar cycle lengths and SW behavior within them. The presence of a slow SW belt, with a variable latitudinal extent changing within each solar cycle from rather small angles to 90 Degree-Sign , separated from the fast wind that originates at coronal holes substantially affects plasma in the inner heliosheath (IHS)-the SW region between the termination shock (TS) and the heliopause (HP). The solar cycle may be the reason why the complicated flow structure is observed in the IHS by Voyager 1. In this paper, we show that a substantial decrease in the SW ram pressure observed by Ulysses between the TS crossings by Voyager 1 and 2 contributes significantly to the difference in the heliocentric distances at which these crossings occurred. The Ulysses spacecraft is the source of valuable information about the three-dimensional and time-dependent properties of the SW. Its unique fast latitudinal scans of the SW regions make it possible to create a solar cycle model based on the spacecraft in situ measurements. On the basis of our analysis of the Ulysses data over the entire life of the mission, we generated time-dependent boundary conditions at 10 AU from the Sun and applied our MHD-neutral model to perform a numerical simulation of the SW-LISM interaction. We analyzed the global variations in the interaction pattern, the excursions of the TS and the HP, and the details of the plasma and magnetic field distributions in the IHS. Numerical results are compared with Voyager data as functions of time in the spacecraft frame. We discuss solar cycle effects which may be reasons for the recent decrease in the TS particles (ions accelerated to anomalous cosmic-ray energies) flux observed by Voyager 1.

Pogorelov, N. V.; Zank, G. P. [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Suess, S. T. [National Space Science and Technology Center, Huntsville, AL 35805 (United States); Borovikov, S. N. [Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, 320 Sparkman Dr., Huntsville, AL 35805 (United States); Ebert, R. W.; McComas, D. J., E-mail: np0002@uah.edu [Southwest Research Institute, San Antonio, TX 78227 (United States)

2013-07-20

241

Three-dimensional Features of the Outer Heliosphere due to Coupling between the Interstellar and Interplanetary Magnetic Fields. IV. Solar Cycle Model Based on Ulysses Observations  

NASA Astrophysics Data System (ADS)

The solar cycle has a profound influence on the solar wind (SW) interaction with the local interstellar medium (LISM) on more than one timescales. Also, there are substantial differences in individual solar cycle lengths and SW behavior within them. The presence of a slow SW belt, with a variable latitudinal extent changing within each solar cycle from rather small angles to 90°, separated from the fast wind that originates at coronal holes substantially affects plasma in the inner heliosheath (IHS)—the SW region between the termination shock (TS) and the heliopause (HP). The solar cycle may be the reason why the complicated flow structure is observed in the IHS by Voyager 1. In this paper, we show that a substantial decrease in the SW ram pressure observed by Ulysses between the TS crossings by Voyager 1 and 2 contributes significantly to the difference in the heliocentric distances at which these crossings occurred. The Ulysses spacecraft is the source of valuable information about the three-dimensional and time-dependent properties of the SW. Its unique fast latitudinal scans of the SW regions make it possible to create a solar cycle model based on the spacecraft in situ measurements. On the basis of our analysis of the Ulysses data over the entire life of the mission, we generated time-dependent boundary conditions at 10 AU from the Sun and applied our MHD-neutral model to perform a numerical simulation of the SW-LISM interaction. We analyzed the global variations in the interaction pattern, the excursions of the TS and the HP, and the details of the plasma and magnetic field distributions in the IHS. Numerical results are compared with Voyager data as functions of time in the spacecraft frame. We discuss solar cycle effects which may be reasons for the recent decrease in the TS particles (ions accelerated to anomalous cosmic-ray energies) flux observed by Voyager 1.

Pogorelov, N. V.; Suess, S. T.; Borovikov, S. N.; Ebert, R. W.; McComas, D. J.; Zank, G. P.

2013-07-01

242

Long-Term Observations of Stream Interaction Regions and Interplanetary Coronal Mass Ejections: Venus, Earth, and Jupiter Orbits  

NASA Astrophysics Data System (ADS)

Two types of large-scale solar wind structures, stream interaction regions (SIRs) and interplanetary coronal mass ejections (ICMEs), can drive interplanetary shocks, generate or accelerate energetic particles, and affect the planetary ionosphere and/or magnetosphere. To quantify the properties of SIRs and ICMEs at different heliocentric distances, we have identified and characterized these structures based on consistent criteria using the in situ plasma and magnetic field observations. The data sets used are Pioneer Venus Orbiter at 0.72 AU (1979 - 1988), Wind/ACE at 1 AU (1995 - 2006), and three Ulysses aphelion passes at 5.3 AU (partial 1992, 1997 - 1998, 2003 - 2005, representing slices at different phases of the solar cycle). The long-term observations enable us to study the solar cycle variations of these two structures. The parameters relevant to space weather modeling, such as the structure duration, width, maximum dynamic pressure, maximum magnetic field intensity, average speed, speed variation, and other properties of SIRs and ICMEs are all examined at each distance. ICMEs can generally affect the planetary environment more than SIRs at Venus and Earth, especially around solar maximum. However, when they propagate to 5.3 AU, some ICMEs and SIRs merge and form hybrid events at Jupiter. In general, SIRs have greater dynamic pressure, interaction strength and field intensity than ICMEs at Jupiter, and therefore they affect the space environment more than ICMEs there.

Jian, L. K.; Russell, C. T.; Luhmann, J. G.; Skoug, R. M.; Steinberg, J. T.

2009-04-01

243

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

244

Plasma Depletion and Mirror Waves Ahead of Interplanetary Coronal Mass Ejections  

Microsoft Academic Search

We find that the sheath regions between fast interplanetary coronal mass ejections (ICMEs) and their preceding shocks are often characterized by plasma depletion and mirror wave structures, analogous to planetary magnetosheaths. A case study of these signatures in the sheath of a magnetic cloud (MC) shows that a plasma depletion layer (PDL) coincides with magnetic field draping around the MC.

Ying D. Liu; J. D. Richardson; J. W. Belcher; J. C. Kasper; R. M. Skoug

2006-01-01

245

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

246

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

247

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

SciTech Connect

The Venus box shock location has been measured at nearly 2,000 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 box shock cross section is circular and only weakly sensitive to changing EUV flux.

Russell, C.T.; Chou, E.; Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Gazis, P. (NASA Ames Research Center, Moffett Field, CA (USA)); Brace, L.H.; Hoegy, W.R. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1988-06-01

248

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

249

Propagation of normal and faster CMEs in the interplanetary medium  

NASA Astrophysics Data System (ADS)

We have analyzed 101 Coronal Mass Ejection (CME) events and their associated interplanetary CMEs (ICMEs) and interplanetary (IP) shocks observed during the period 1997-2005 from the list given by Mujiber Rahman et al. (2012). The aim of the present work is to correlate the interplanetary parameters such as, the speeds of IP shocks and ICMEs, CME transit time and their relation with CME parameters near the Sun. Mainly, a group of 10 faster CME events (VINT > 2200 km/s) are compared with a list of 91 normal events of Manoharan et al. (2004). From the distribution diagrams of CME, ICME and IP shock speeds, we note that a large number of events tends to narrow towards the ambient (i.e., background) solar wind speed (?500 km/s) in agreement with the literature. Also, we found that the IP shock speed and the average ICME speed measured at 1 AU are well correlated. In addition, the IP shock speed is found to be slightly higher than the ICME speed. While the normal events show CME travel time in the range of ?40-80 h with a mean value of 65 h, the faster events have lower transit time with a mean value of 40 h. The effect of solar wind drag is studied using the correlation of CME acceleration with interplanetary (IP) acceleration and with other parameters of ICMEs. While the mean acceleration values of normal and faster CMEs in the LASCO FOV are 1 m/s2, 18 m/s2, they are -1.5 m/s2 and -14 m/s2 in the interplanetary medium, respectively. The relation between CME speed and IP acceleration for normal and faster events are found to agree with that of Lindsay et al. (1999) and Gopalswamy et al. (2001) except slight deviations for the faster events. It is also seen that the faster events with less travel time face higher negative acceleration (>-10 m/s2) in the interplanetary medium up to 1 AU.

Mujiber Rahman, A.; Shanmugaraju, A.; Umapathy, S.

2013-09-01

250

Location of the radio emitting regions of interplanetary shocks  

NASA Technical Reports Server (NTRS)

Twenty interplanetary type II radio bursts are analyzed to determine the location of the type II source region relative to the interplanetary shock. The first determination of a density-distance relationship (density model) appropriate for interplanetary type II source regions is reported. To determine source location, densities in type II source regions, derived from observed type II emission frequencies, are compared to ambient solar wind densities to determine whether source regions are in the ambient, upstream solar wind or in the compressed plasma behind the shock. Densities in the ambient solar wind upstream of each shock are computed by using a simple model to extrapolate solar wind plasma densities measured at 1 AU back to the shock front. Densities in the type II source regions are found to be enhanced relative to densities in the ambient solar wind by a factor which is close to the average shock density compression ratio. The simplest interpretation of this result is that the source is located in the compressed plasma within or behind the shock. Although it is possible that the emission is produced in enhanced density regions of the upstream solar wind, it is argued that the weight of evidence favors the compressed postshock plasma as the source site.

Lengyel-Frey, D.

1992-01-01

251

Solar events and their influence on the interplanetary medium  

NASA Technical Reports Server (NTRS)

Aspects of a workshop on Solar events and their influence on the interplanetary medium, held in September 1986, are reviewed, the goal of which was to foster interactions among colleagues, leading to an improved understanding of the unified relationship between solar events and interplanetary disturbances. The workshop consisted of three working groups: (1) flares, eruptives, and other near-Sun activity; (2) coronal mass ejections; and (3) interplanetary events. Each group discussed topics distributed in advance. The flares-eruptives group members agreed that pre-event energy is stored in stressed/sheared magnetic fields, but could not agree that flares and other eruptive events (e.g., eruptive solar prominences) are aspects of the same physical phenomenon. In the coronal mass ejection group, general agreement was reached on the presence of prominences in CMEs, and that they have a significant three-dimensional structure. Some topics identified for further research were the aftermath of CMEs (streamer deflections, transient coronal holes, possible disconnections), identification of the leading edge of CMEs, and studies of the range and prevalence of CME mass sizes and energies.

Joselyn, Joann

1987-01-01

252

Direct Measurements of Interplanetary Dust Particles in the Vicinity of Earth  

NASA Technical Reports Server (NTRS)

The direct measurements made by the Explorer VIII satellite provide the first sound basis for analyzing all available direct measurements of the distribution of interplanetary dust particles. The model average distribution curve established by such an analysis departs significantly from that predicted by the (uncertain) extrapolation of results from meteor observations. A consequence of this difference is that the daily accretion of interplanetary particulate matter by the earth is now considered to be mainly dust particles of the direct measurements range of particle size. Almost all the available direct measurements obtained with microphone systems on rockets, satellites, and spacecraft fit directly on the distribution curve defined by Explorer VIII data. The lack of reliable datum points departing significantly from the model average distribution curve means that available direct measurements show no discernible evidence of an appreciable geocentric concentration of interplanetary dust particles.

McCracken, C. W.; Alexander, W. M.; Dubin, M.

1961-01-01

253

Infrared emission from interplanetary dust  

SciTech Connect

Standard models of the interplanetary dust emission fail to account satisfactorily for IR observations. A new model of the dust, based on very simple assumptions on the grain structure (spherical and homogeneous) and chemical composition (astronomical silicates, graphite, blackbodies) is developed. Updated values of the refractive indexes have been included in the analysis. The predictions of the model (absolute values of the fluxes, spectral shape, elongation dependence of the emission) have then been compared with all the available IR observations performed by the ARGO (balloon-borne experiment by University of Rome), AFGL and Zodiacal Infrared Project (ZIP) (rocket experiments by Air Force Geophysics Laboratory, Bedford, Mass.), and IRAS satellite. Good agreement is found when homogeneous data sets from single experiments (e.g., ZIP and ARGO) are considered separately. 19 references.

Temi, P.; De Bernardis, P.; Masi, S.; Moreno, G.; Salama, A.

1989-02-01

254

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

255

Modeling Interplanetary Coronal Mass Ejections  

NASA Technical Reports Server (NTRS)

Heliospheric models of Coronal Mass Ejection (CME) propagation and evolution provide an important insight into the dynamics of CMEa and are a valuable tool for interpreting interplanetary in situ observations. Moreover, they represent a virtual laboratory for exploring conditions and regions of space that are not conveniently or currently accessible by spacecraft. In this review I summarize recent advances in modeling the properties and evolution of CMEs in the solar wind. In particular, I will focus on: (1) the types of ICME models; (2) the boundary conditions that are imposed, (3) the role of the ambient solar wind; (4) predicting new phenomena; and (5) distinguishing between competing CME initiation mechanisms. I will conclude by discussing what topics will likely be important for models to address in the future.

Riley, Pete

2004-01-01

256

Impact angle control of interplanetary shock geoeffectiveness  

NASA Astrophysics Data System (ADS)

We use Open Geospace General Circulation Model global MHD simulations to study the nightside magnetospheric, magnetotail, and ionospheric responses to interplanetary (IP) fast forward shocks. Three cases are presented in this study: two inclined oblique shocks, hereafter IOS-1 and IOS-2, where the latter has a Mach number twice stronger than the former. Both shocks have impact angles of 30° in relation to the Sun-Earth line. Lastly, we choose a frontal perpendicular shock, FPS, whose shock normal is along the Sun-Earth line, with the same Mach number as IOS-1. We find that, in the IOS-1 case, due to the north-south asymmetry, the magnetotail is deflected southward, leading to a mild compression. The geomagnetic activity observed in the nightside ionosphere is then weak. On the other hand, in the head-on case, the FPS compresses the magnetotail from both sides symmetrically. This compression triggers a substorm allowing a larger amount of stored energy in the magnetotail to be released to the nightside ionosphere, resulting in stronger geomagnetic activity. By comparing IOS-2 and FPS, we find that, despite the IOS-2 having a larger Mach number, the FPS leads to a larger geomagnetic response in the nightside ionosphere. As a result, we conclude that IP shocks with similar upstream conditions, such as magnetic field, speed, density, and Mach number, can have different geoeffectiveness, depending on their shock normal orientation.

Oliveira, D. M.; Raeder, J.

2014-10-01

257

Relationship of ground level enhancements with solar, interplanetary and geophysical parameters  

NASA Astrophysics Data System (ADS)

Cosmic rays registered by Neutron Monitor on the surface of the Earth are believed to originate from outer space, and sometimes also from the exotic objects of the Sun. Whilst the intensities of the cosmic rays are observed to be enhanced with sudden, sharp and short-lived increases, they are termed as ground level enhancements (GLEs). They are the occurrences in solar cosmic ray intensity variations on short-term basis, so different solar factors erupted from the Sun can be responsible for causing them. In this context, an attempt has been made to determine quantitative relationships of the GLEs having peak increase >5% with simultaneous solar, interplanetary and geophysical factors from 1997 through 2006, thereby searching the responsible factors which seem to cause the enhancements. Results suggest that GLE peaks might be caused by solar energetic particle fluxes and solar flares. The proton fluxes which seemed to cause GLE peaks were also supported by their corresponding fluences. For most of the flares, the time integrated rising portion of the flare emission refers to the strong portion of X-ray fluxes which might be the concern to GLE peak. On an average, GLE peak associated X-ray flux (0.71×10-4 w/m2) is much stronger than GLE background associated X-ray flux (0.11×10-6 w/m2). It gives a general consent that the GLE peak is presumably caused by the solar flare. Coronal mass ejection alone does not seem to cause GLE. Coronal mass ejection presumably causes geomagnetic disturbances characterized by geomagnetic indices and polarities of interplanetary magnetic fields.

Firoz, K. A.; Hwang, J.; Dorotovi?, I.; Pintér, T.; Kaushik, Subhash C.

2011-02-01

258

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

259

Interplanetary Physics Laboratory (IPL): A concept for an interplanetary mission in the mid-eighties  

NASA Technical Reports Server (NTRS)

A concept for a near-earth interplanetary mission in the mid-eighties is described. The proposed objectives would be to determine the composition of the interplanetary constituents and its dependence on source-conditions and to investigate energy and momentum transfer processes in the interplanetary medium. Such a mission would accomplish three secondary objectives: (1) provide a baseline for deep space missions, (2) investigate variations of the solar wind with solar activity, and (3) provide input functions for magnetospheric studies.

Burlaga, L. F.; Ogilvie, K. W.; Feldman, W.

1977-01-01

260

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

261

Evolution of Fourier spectra through interplanetary shocks  

NASA Astrophysics Data System (ADS)

Well established nearly isothermic solar wind expansion requires an additional heating. A dissipation of large scale variations of the solar wind kinetic energy into the thermal energy via turbulence cascades is thought to be an important source of this heating, although the exact mechanism is yet to be found. For this reason, the turbulence in the solar wind is a subject of extensive theoretical and experimental studies on different time scales ranging from years to minutes. The frequency spectrum of magnetic field fluctuations can be divided into several domains differing by spectral indices - the lowest frequencies are controlled by the solar activity, MHD activity shapes the spectrum at higher (up to 0.1 Hz) frequencies, whereas the ion and electron kinetic effects dominate at the high frequency end of the spectra. Interplanetary shocks of various origins are a part of solar wind turbulence naturally occurring in the solar wind and the BMSW instrument onboard the Spektr-R spacecraft has detected tens of them in course of the 2011-2013 years. Based on its high-time resolution of the ion flux, density and velocity measurements reaching 31 ms, we study an evolution of the frequency spectra on MHD and kinetic scales across fast forward low Mach number shocks. We have found that the power of downstream fluctuations rises by an order of magnitude in a broad range of frequencies independently of its upstream value but the slope of the spectrum on the kinetic scale (?3-8 Hz) has been found to be statistically steeper downstream than upstream of the shock. The time needed to a full relaxation to the pre-shock spectral shape is as long as several hours. A combination of the ion flux power spectra obtained by BMSW with fast magnetic field observations of other spacecraft enhances our understanding of dissipation mechanisms.

Pitna, Alexander; Safrankova, Jana; Nemecek, Zdenek; Nemec, Frantisek; Goncharov, Oleksandr

2014-05-01

262

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

263

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3  

SciTech Connect

Plasma fluid parameters calculated from solar wind and magnetic field data obtained on ISEE 3 were studied to determine the characteristic properties of driver gas following interplanetary shocks. Of 54 shocks observed from August 1978 to February 1980, 9 contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature across a tangential discontinuity. While helium enhancements were present in all of 9 of these events, only about half of them contained simultaneous changes in the two quantities. Often the He/H ratio changed over a period of minutes. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance and by an increase in the ratio of parallel to perpendicular temperature. The drive gas usually displayed a bi-directional flow of suprathermal solar wind electrons at higher energies (>137 eV).

Zwickl, R.D.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.; Gosling, J.T.; Smith, E.J.

1982-01-01

264

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

265

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

266

The amplitudes of interplanetary fluctuations: Stream structure, heliocentric distance, and frequency dependence  

Microsoft Academic Search

The authors present a study of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. The results constrain theories of the acceleration of the solar wind and of the evolution of fluctuation

D. A. Roberts; M. L. Goldstein; L. W. Klein

1990-01-01

267

Transverse flow deflections associated with fast coronal mass ejecta in interplanetary space  

SciTech Connect

Using a bidirectional electron heat flux signature to identify coronal mass ejections, CMEs, in the solar wind at 1 AU, we find that the fast CMEs which drive interplanetary shocks are preferentially deflected eastward in transit outward from the sun. A corresponding westward deflection usually occurs in the compressed ambient solar wind plasma ahead of these CMEs. We suggest that this preferential pattern of deflections is caused primarily by the asymmetrical draping of the ambient interplanetary magnetic field about fast CMEs. 10 refs., 7 figs.

Gosling, J.T.; Thomsen, M.F.; Bame, S.J.; Zwickl, R.D.

1987-01-01

268

Interplanetary sector boundaries, 1971 - 1973  

NASA Technical Reports Server (NTRS)

Eighteen interplanetary sector boundary crossings observed at 1 AU by the magnetometer on the IMP-6 spacecraft are discussed. The events were examined on many different time scales ranging from days on either side of the boundary to high resolution measurements of 12.5 vectors per second. Two categories of boundaries were found, one group being relatively thin and the other being thick. In many cases the field vector rotated in a plane from one polarity to the other. Only two of the transitions were null sheets. Using the minimum variance analysis to determine the normals to the plane of rotation, and assuming that this is the same as the normal to the sector boundary surface, it was found that the normals were close to the ecliptic plane. An analysis of tangential discontinuities contained in 4-day periods about the events showed that their orientations were generally not related to the orientations of the sector boundary surface, but rather their characteristics were about the same as those for discontinuities outside the sector boundaries.

Klein, L.; Burlaga, L. F.

1979-01-01

269

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

270

Propagation and Evolution of CMEs in the Interplanetary Medium: Analysis of Remote Sensing and In situ Observations  

NASA Technical Reports Server (NTRS)

EUV disk imagers and white light coronagraphs have provided for many years information on the early formation and evolution of corona) mass ejections (CMEs). More recently, the novel heliospheric imaging instruments aboard the STEREO mission are providing crucial remote sensing information on the interplanetary evolution of these events while in situ instruments complete the overall characterization of the interplanetary CMEs. In this work, we present an analysis of CMEs from the Sun to the interplanetary medium using combined data from THE SOHO, STEREO, WIND, and ACE spacecraft. The events were selected to cover the widest possible spectrum of different ambient solar wind, magnetic field configurations, plasma parameters, etc. to allow uncovering those aspects that are important in understanding the propagation and evolution mechanisms of CMEs in the interplanetary medium.

Figueroa-Vinas, Adolfo; Nieves-Chinchilla, Teresa; Vourlidas, Angelos; Gomez-Herrero, Raul; Malandraki, Olga; Szabo, Adam; Dresing, Nina; Davila, Joseph M.

2010-01-01

271

The Heliocentric Variation of the Properties of Interplanetary Field Enhancement  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) are increases of the interplanetary magnetic field usually to a sharp maximum and containing a current sheet near the center of the event. They have been observed at Helios and MESSENGER as close as 0.3 AU to the Sun, at VEX and PVO at 0.72 AU; at STEREO, ACE, Wind, Geotail, ARTEMIS at 1 AU and Ulysses from 1 to 5 AU. Our model for the physical mechanism for creating these disturbances is that collisions of bodies in the size range 10 - 1000m are catastrophically disrupted by a collision with a fast moving smaller object. The rate of detection of IFEs is dependent on heliocentric range increasing closer to the Sun. There are several possible reasons for this increase which we explore. The mass of the dust cloud that is picked up is significant about 108kg. The magnetic gradient force of the IFE is large enough to lift this mass through the Sun's gravitational potential wall. The momentum transfer that enables this outward transport is a small fraction of the solar wind momentum flux but this transfer can be detected using superposed epoch studies of the solar wind, and is consistent with the hypothesis. We note that the rate of IFE observations in the Helios and MESSENGER data at 0.3 AU is less than expected from extrapolating the observations at and beyond 0.7 AU. This result can soon be extended closer to the Sun with Solar Orbiter and Solar Probe Plus.

Lai, H.; Russell, C. T.; Wei, H.; Zhang, T.

2013-05-01

272

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

273

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

274

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

275

Performance of a Bounce-Averaged Global Model of Super-Thermal Electron Transport in the Earth's Magnetic Field  

NASA Technical Reports Server (NTRS)

In this paper, we report the results of our recent research on the application of a multiprocessor Cray T916 supercomputer in modeling super-thermal electron transport in the earth's magnetic field. In general, this mathematical model requires numerical solution of a system of partial differential equations. The code we use for this model is moderately vectorized. By using Amdahl's Law for vector processors, it can be verified that the code is about 60% vectorized on a Cray computer. Speedup factors on the order of 2.5 were obtained compared to the unvectorized code. In the following sections, we discuss the methodology of improving the code. In addition to our goal of optimizing the code for solution on the Cray computer, we had the goal of scalability in mind. Scalability combines the concepts of portabilty with near-linear speedup. Specifically, a scalable program is one whose performance is portable across many different architectures with differing numbers of processors for many different problem sizes. Though we have access to a Cray at this time, the goal was to also have code which would run well on a variety of architectures.

McGuire, Tim

1998-01-01

276

Noise reduction of nuclear magnetic resonance (NMR) transversal data using improved wavelet transform and exponentially weighted moving average (EWMA).  

PubMed

NMR logging and core NMR signals acts as an effective way of pore structure evaluation and fluid discrimination, but it is greatly contaminated by noise for samples with low magnetic resonance intensity. Transversal relaxation time (T2) spectrum obtained by inversion of decay signals intrigued by Carr-Purcell-Meiboom-Gill (CPMG) sequence may deviate from the truth if the signal-to-noise ratio (SNR) is imperfect. A method of combing the improved wavelet thresholding with the EWMA is proposed for noise reduction of decay data. The wavelet basis function and decomposition level are optimized in consideration of information entropy and white noise estimation firstly. Then a hybrid threshold function is developed to avoid drawbacks of hard and soft threshold functions. To achieve the best thresholding values of different levels, a nonlinear objective function based on SNR and mean square error (MSE) is constructed, transforming the problem to a task of finding optimal solutions. Particle swarm optimization (PSO) is used to ensure the stability and global convergence. EWMA is carried out to eliminate unwanted peaks and sawtooths of the wavelet denoised signal. With validations of numerical simulations and experiments, it is demonstrated that the proposed approach can reduce the noise of T2 decay data perfectly. PMID:25574595

Ge, Xinmin; Fan, Yiren; Li, Jiangtao; Wang, Yang; Deng, Shaogui

2015-02-01

277

LDEF Interplanetary Dust Experiment (IDE) results  

NASA Technical Reports Server (NTRS)

The Interplanetary Dust Experiment (IDE) provided high time resolution detection of microparticle impacts on the Long Duration Exposure Facility satellite. Particles, in the diameter range from 0.2 microns to several hundred microns, were detected impacting on six orthogonal surfaces of the gravity-gradient stabilized LDEF spacecraft. The total sensitive surface area was about one square meter, distributed between LDEF rows 3 (Wake or West), 6 (South), 9 (Ram or East), 12 (North), as well as the Space and Earth ends of LDEF. The time of each impact is known to an accuracy that corresponds to better than one degree in orbital longitude. Because LDEF was gravity-gradient stabilized and magnetically damped, the direction of the normal to each detector panel is precisely known for each impact. The 11 1/2 month tape-recorded data set represents the most extensive record gathered of the number, orbital location, and incidence direction for microparticle impacts in low Earth orbit. Perhaps the most striking result from IDE was the discovery that microparticle impacts, especially on the Ram, South, and North surfaces, were highly episodic. Most such impacts occurred in localized regions of the orbit for dozens or even hundreds of orbits in what we have termed Multiple Orbit Event Sequences (MOES). In addition, more than a dozen intense and short-lived 'spikes' were seen in which impact fluxes exceeded the background by several orders of magnitude. These events were distributed in a highly non-uniform fashion in time and terrestrial longitude and latitude.

Oliver, John P.; Singer, S. F.; Weinberg, J. L.; Simon, C. G.; Cooke, W. J.; Kassel, P. C.; Kinard, W. H.; Mulholland, J. D.; Wortman, J. J.

1995-01-01

278

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

NASA Technical Reports Server (NTRS)

Ten transient magnetic structures in Earth's magnetotail, as observed in GEOTAIL measurements, selected for early 1993 (at (-) X(sub GSM) = 90 - 130 Earth radii), 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 approximately = 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 are seen to be typically aligned with the Y(sub GSM) axis and the average diameter of these structures is approximately = 15 Earth radii.

Lepping, R. P.; Fairfield, D. H.; Jones, J.; Frank, L. A.; Paterson, W. R.; Kokubun, S.; Yamamoto, T.

1995-01-01

279

Interplanetary Origin of Geomagnetic Activity in the Declining Phase of the Solar Cycle  

Microsoft Academic Search

Interplanetary magnetic field (IMF) and plasma data are contpared with ground-based geomagnetic Dsr and AE indices to determine the causes of magnetic storms, substor-(ns, and quiet during the descending phase of the solar cycle. In this paper we focus pJ imarily on 1974 when the AZ index is anomalously high (~ = 283 nT). This year is characterized by the

Bruce T. Tsurutani; Walter D. Gonzalez; Alicia L. C. Gonzalez; Frances Tang; John K. Arballo; Masaki Okada

1995-01-01

280

Average Names  

NSDL National Science Digital Library

In this activity, learners compare the number of letters in the names of the people in their families or group of friends. Learners write out the names in graph paper, with one letter in each square, and cut out the names. Learners sort the names from shortest to longest and then find the average length of the names by cutting and scrambling up the letters. This activity guide contains sample questions to ask, literary connections, extensions, and alignment to local and national standards.

2014-09-19

281

Observations of electromagnetic whistler precursors at supercritical interplanetary shocks  

E-print Network

identified as a right-hand polarized wave with fci species waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search interplanetary (IP) shocks observed by the Wind spacecraft. We also present evidence for wave heating

California at Berkeley, University of

282

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

283

The solar/interplanetary event of 14 April 1994 observed by Yohkoh/SXT  

NASA Technical Reports Server (NTRS)

The polar crown event of April 14 1994 is one of the largest scale eruptive events observed by the Yohkoh/SXT. Associated with the formation of an arcade of soft X-ray loops at the Sun was the detection of an interplanetary forward/reverse shock event by the Ulysses spacecraft some 4-7 days later. The relationship between the coronal and interplanetary signatures of these events is important if we are to address fully the initialization and consequent acceleration of interplanetary phenomena, such as CMEs and counter-streaming electrons, originating at the Sun. From detailed analysis of the energetics of the arcade formed during the eruption of April 14 1994, we find peak temperatures and emission measures of approximately 5MK and approximately 10(exp 48)cm(exp -3) respectively. The total thermal content of the arcade loop structure observed in soft X-rays is calculated to be some 5 x 10(exp 29) ergs. The development of these parameters as the event proceeds and their relationship to the dynamics of the eruption are investigated. Although spanning a longitudinal range of some 150 degrees the April 14 event displayed the typical helmet streamer structure normally associated with coronal mass ejections These helmet streamers are thought to be related to the global solar magnetic field through the heliospheric current sheet (HCS). The arcade formation, together with the eruption of material into interplanetary space, signifies a large-scale reconfiguration of the coronal magnetic field. We examine the effects of the formation of such a coronal arcade structure on the HCS and discuss the dynamics involved with the passage of a large scale disturbance through the interplanetary magnetic field.

Alexander, D.; Harvey, K. L.; Hudson, H. S.; Hoeksema, J. T.; Zhao, X.

1995-01-01

284

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

285

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

286

Mass ejections from the sun and their interplanetary counterparts  

SciTech Connect

Since the first observations of solar mass ejection events in the early seventies from OSO 7 and Skylab a few thousand of these remarkable dynamic incidents have been observed by now, covering about two full solar activity cycles. The mass ejecta include mainly hot coronal plasma, plus cold prominence material in variable amounts. The ejecta are often recognised in the form of interplanetary plasma clouds detected in the distant solar wind by appropriately located spacecraft. Clouds which have been energetic enough to drive large scale interplanetary shock waves can be identified most readily, but clouds without associated shocks do also occur. The plasma clouds are characterized by a variety of signatures indicating that they actually originate from injections of different material into the ambient solar wind. Usually only a few of the signatures are found simultaneously. Apparently the bidirectional streaming of halo electrons is a most reliable criterion, indicating a magnetic bottle or plasmoid topology of the clouds. The discussion of the most recent discoveries in this context will show that quite a few crucial problems still remain to be addressed by the upcoming SOHO mission.

Schwenn, R.

1995-06-01

287

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

288

A new propulsion concept for interplanetary missions  

Microsoft Academic Search

When tons of payload must be brought back from the planets to Earth, the current launch-system technology hits size limitations. The huge Saturn-V launcher that enabled the Apollo missions to go to the Moon would be dwarfed by a single launcher capable of sending men to a destination like Mars and bringing them back. Keeping interplanetary missions within a reasonable

C. Dujarric

2001-01-01

289

Dynamic Model Development for Interplanetary Navigation  

NASA Astrophysics Data System (ADS)

In this paper, the dynamic model development for interplanetary navigation has been discussed. The Cowell method for special perturbation theories was employed to develop an interplanetary trajectory propagator including the perturbations due to geopotential, the Earth's dynamic polar motion, the gravity of the Sun, the Moon and the other planets in the solar system, the relativistic effect of the Sun, solar radiation pressure, and atmospheric drag. The equations of motion in dynamic model were numerically integrated using Adams-Cowell 11th order predictor-corrector method. To compare the influences of each perturbation, trajectory propagation was performed using initial transfer orbit elements of the Mars Express mission launched in 2003, because it can be the criterion to choose proper perturbation models for navigation upon required accuracy. To investigate the performance of dynamic model developed, it was tested whether the spacecraft can reach the Mars. The interplanetary navigation tool developed in this study demonstrated the spacecraft entering the Mars SOI(Sphere of Influence) and its velocity relative to the Mars was less than the escape velocity of the Mars, hence, the spacecraft can arrive at the target planet. The obtained results were also verified by using the AGI Satellite Tool Kit. It is concluded that the developed program is suitable for supporting interplanetary spacecraft mission for a future Korean Mars mission.

Park, Eun-Seo; Song, Young-Joo; Yoo, Sung-Moon; Park, Sang-Young; Choi, Kyu-Hong; Yoon, Jae-Cheol; Yim, Jo Ryeong; Choi, Joon-Min; Kim, Byung-Kyo

2005-12-01

290

Interplanetary proton fluence model - JPL 1991  

Microsoft Academic Search

We describe an updated predictive engineering model for the interplanetary fluence of protons with energies respectively greater than 1, 4, 10, 30, and 60 MeV. This has been the first opportunity to derive a model from a data set that has been collected in space over a long enough period of time to produce a valid sample of solar proton

J. Feynman; G. Spitale; J. Wang; S. Gabriel

1993-01-01

291

Interplanetary space transport using inertial fusion propulsion  

Microsoft Academic Search

In this paper, we indicate how the great advantages that ICF offers for interplanetary propulsion can be accomplished with the VISTA spacecraft concept. The performance of VISTA is expected to surpass that from other realistic technologies for Mars missions if the energy gain achievable for ICF targets is above several hundred. Based on the good performance expected from the U.

Orth

1998-01-01

292

End-to-End over Interplanetary  

E-print Network

planet. Several probes are now shooting toward Mars, including the British Bea- gle 2 lander and NASANetworked End-to-End over Interplanetary Networks T he planets have aligned. This is usually of more interest to astrologers than engineers, but the current planetary alignment brings Mars closer

Filman, Robert E.

293

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

294

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

295

Apollo and the Space Race! Interplanetary Travel!  

E-print Network

Seminar 6! Apollo and the Space Race! Interplanetary Travel! FRS 104, Princeton University! Robert" !! Project Rover, 1960s "" !! Nuclear rockets" !! High specific impulse" !! Safety concerns" !! Atmospheric contamination" !! Reactor re-entry in launch failure" Project Rover, 1960s" Resurgent interest in nuclear

Stengel, Robert F.

296

Statistical study of magnetic cloud erosion by magnetic reconnection  

NASA Astrophysics Data System (ADS)

recent studies suggest that magnetic reconnection is able to erode substantial amounts of the outer magnetic flux of interplanetary magnetic clouds (MCs) as they propagate in the heliosphere. We quantify and provide a broader context to this process, starting from 263 tabulated interplanetary coronal mass ejections, including MCs, observed over a time period covering 17 years and at a distance of 1 AU from the Sun with Wind (1995-2008) and the two STEREO (2009-2012) spacecraft. Based on several quality factors, including careful determination of the MC boundaries and main magnetic flux rope axes, an analysis of the azimuthal flux imbalance expected from erosion by magnetic reconnection was performed on a subset of 50 MCs. The results suggest that MCs may be eroded at the front or at rear and in similar proportions, with a significant average erosion of about 40% of the total azimuthal magnetic flux. We also searched for in situ signatures of magnetic reconnection causing erosion at the front and rear boundaries of these MCs. Nearly ~30% of the selected MC boundaries show reconnection signatures. Given that observations were acquired only at 1 AU and that MCs are large-scale structures, this finding is also consistent with the idea that erosion is a common process. Finally, we studied potential correlations between the amount of eroded azimuthal magnetic flux and various parameters such as local magnetic shear, Alfvén speed, and leading and trailing ambient solar wind speeds. However, no significant correlations were found, suggesting that the locally observed parameters at 1 AU are not likely to be representative of the conditions that prevailed during the erosion which occurred during propagation from the Sun to 1 AU. Future heliospheric missions, and in particular Solar Orbiter or Solar Probe Plus, will be fully geared to answer such questions.

Ruffenach, A.; Lavraud, B.; Farrugia, C. J.; Démoulin, P.; Dasso, S.; Owens, M. J.; Sauvaud, J.-A.; Rouillard, A. P.; Lynnyk, A.; Foullon, C.; Savani, N. P.; Luhmann, J. G.; Galvin, A. B.

2015-01-01

297

On the average configuration of the geomagnetic tail  

NASA Technical Reports Server (NTRS)

Over 3000 hours of IMP-6 magnetic field data obtained between 20 and 33 R sub E in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5 minute averages of B sub Z as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight. The tail field projected in the solar magnetospheric equatorial plane deviates from the X axis due to flaring and solar wind aberration by an angle alpha = -0.9 y sub SM - 1.7 where Y sub SM is in earth radii and alpha is in degrees. After removing these effects the Y component of the tail field is found to depend on interplanetary sector structure. During an away sector the B sub Y component of the tail field is on average 0.5 gamma greater than that during a toward sector, a result that is true in both tail lobes and is independent of location across the tail.

Fairfield, D. H.

1978-01-01

298

Cosmic-ray streaming perpendicular to the mean magnetic field  

NASA Technical Reports Server (NTRS)

Starting from a quasi-linear approximation for the ensemble-averaged particle distribution function in a random magnetic field, the complete diffusion tensor is derived. This is done by assuming a simple form for the ensemble-averaged distribution function, explicitly retaining all components of the streaming flux. This derivation obtains the antisymmetric terms in a natural manner. The necessary dropping of higher-order terms gives a criterion for the lower-energy limit of validity of the perpendicular and antisymmetric diffusion coefficients. The limit for the assumed distribution function is about 0.8 GV rigidity in the interplanetary field near 1 AU.

Forman, M. A.; Jokipii, J. R.; Owens, A. J.

1974-01-01

299

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

300

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

301

ULYSSES out-of-ecliptic observations of interplanetary shocks.  

NASA Astrophysics Data System (ADS)

Interplanetary shocks observed at the Ulysses spacecraft as it traveled from the ecliptic plane to the southern solar pole have been identified and analyzed using both magnetic field and plasma measurements. The latitude dependences of various parameters associated with the shocks (beta, ?_BN_ and Mach number) have been investigated. The direction of shock propagation of forward and reverse corotating shocks is qualitatively consistent with the global 3-D model of Pizzo [1991] which predicts that forward shocks will propagate equatorward while reverse shocks propagate poleward. The strongest shocks, are observed at mid-latitudes and are from the south polar coronal hole. These shocks are shown to be supercritical in contrast to the lower latitude sub-critical shocks. This change in character of the shocks is likely related to the intensity of the shock-accelerated energetic particles which also peaks in the same latitude range.

Burton, M. E.; Smith, E. J.; Balogh, A.; Forsyth, R. J.; Bame, S. J.; Phillips, J. L.; Goldstein, B. E.

1996-12-01

302

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

303

Toroidal Plasma Thruster for Interplanetary and Interstellar Space Flights  

SciTech Connect

This work involves a conceptual assessment for using the toroidal fusion reactor for deep space interplanetary and interstellar missions. Toroidal thermonuclear fusion reactors, such as tokamaks and stellarators, are unique for space propulsion, allowing for a design with the magnetic configuration localized inside toroidal magnetic field coils. Plasma energetic ions, including charged fusion products, can escape such a closed configuration at certain conditions, a result of the vertical drift in toroidal rippled magnetic field. Escaping particles can be used for direct propulsion (since toroidal drift is directed one way vertically) or to create and heat externally confined plasma, so that the latter can be used for propulsion. Deuterium-tritium fusion neutrons with an energy of 14.1 MeV also can be used for direct propulsion. A special design allows neutrons to escape the shield and the blanket of the tokamak. This provides a direct (partial) conversion of the fusion energy into the directed motion of the propellant. In contrast to other fusion concepts proposed for space propulsion, this concept utilizes the natural drift motion of charged particles out of the closed magnetic field configuration.

N.N. Gorelenkov; L.E. Zakharov; and M.V. Gorelenkova

2001-07-11

304

Identification of Interplanetary Coronal Mass Ejections at 1 AU Using Multiple Solar Wind Plasma Composition Anomalies  

NASA Technical Reports Server (NTRS)

We investigate the use of multiple simultaneous solar wind plasma compositional anomalies, relative to the composition of the ambient solar wind, for identifying interplanetary coronal mass ejection (ICME) plasma. We first summarize the characteristics of several solar wind plasma composition signatures (O(+7)/O(+6), Mg/O, Ne/O, Fe charge states, He/p) observed by the ACE and WIND spacecraft within the ICMEs during 1996 - 2002 identsed by Cane and Richardson. We then develop a set of simple criteria that may be used to identify such compositional anomalies, and hence potential ICMEs. To distinguish these anomalies from the normal variations seen in ambient solar wind composition, which depend on the wind speed, we compare observed compositional signatures with those 'expected' in ambient solar wind with the same solar wind speed. This method identifies anomalies more effectively than the use of fixed thresholds. The occurrence rates of individual composition anomalies within ICMEs range from approx. 70% for enhanced iron and oxygen charge states to approx. 30% for enhanced He/p (> 0.06) and Ne/O, and are generally higher in magnetic clouds than other ICMEs. Intervals of multiple anomalies are usually associated with ICMEs, and provide a basis for the identification of the majority of ICMEs. We estimate that Cane and Richardson, who did not refer to composition data, probably identitied approx. 90% of the ICMEs present. However, around 10% of their ICMEs have weak compositional anomalies, suggesting that the presence of such signatures does not provide a necessary requirement for an ICME. We note a remarkably similar correlation between the Mg/O and O(7)/O(6) ratios in hourly-averaged data both within ICMEs and the ambient solar wind. This 'universal' relationship suggests that a similar process (such as minor ion heating by waves inside coronal magnetic field loops) produces the first-ionization potential bias and ion freezing-in temperatures in the source regions of both ICMEs and the ambient solar wind.

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

2004-01-01

305

Characteristics of the Region of Interaction between the Interplanetary Plasma and the Geomagnetic Field: Pioneer 5  

Microsoft Academic Search

Measurements of the magnetic fields in the distant geomagnetic cavity and in the region of interaction between the solar wind and the magnetosphere are described. These measurements were' Obtained on March 11, 1960, with instruments aboard the interplanetary probe Pioneer 5 in the'region between 5.2 and 15.4 Re and between 1500 and 1700 local time. The observations obtained between 5.2

Paul J. Coleman

1964-01-01

306

Requirements for predictions and real-time monitoring for the study of travelling interplanetary phenomena  

NASA Technical Reports Server (NTRS)

Physical processes within quiescent as well as disturbed flows of solar wind plasma, energetic particles, and magnetic and electric fields from the Sun are considered. Specifically, travelling interplanetary phenomena to be studied during the years of the solar maximum of solar cycle 21 are covered. It is noted that predictions, while needed for long range, logistical planning, is secondary to the requirements of synoptic real time monitoring over a wide range of particle energies and spectral bandwidths.

Dryer, M.; Shea, M. A.

1979-01-01

307

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

Microsoft Academic Search

The Venus box shock location has been measured at nearly 2,000 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

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

1988-01-01

308

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

309

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

310

Magnetospheric response to solar wind dynamic pressure variations: Interaction of interplanetary tangential discontinuities with the bow shock  

NASA Technical Reports Server (NTRS)

Some magnetic impulse events observed in the polar region are related to vortices associated with plasma convection in the ionosphere. Recent analyses of satellite and ground data suggest that the interaction of solar wind dynamic pressure pulses and the magnetosphere may lead to the formation of velocity vortices in the magnetopause boundary layer region. This can in turn lead to the presence of vortices in the polar ionosphere. However, before reaching the Earth's magnetopause, these interplanetary pressure pulses must interact with and pass through the bow shock. A variation of the solar wind dynamic pressure may be associated with shocks, magnetic holes, or tangential discontinuities (TDs) in the interplanetary medium. We study the interaction of interplanetary TDs with the Earth's bow shock (BS) using both theoretical analysis and MHD computer simulations. It is found that as a result of the collision between a TD and the BS, the jump in the solar wind dynamic pressure associated with the TD is significantly modified, the bow shock moves, and a new fast shock or fast rarefaction wave, which propagates in the downstream direction, is excited. Our theoretical analysis shows that the change in the plasma density across the interplanetary TD plays the most important role in the collision process. In the case with an enhanced dynamic pressure behind the interplanetary TD, the bow shock is intensified in strength and moves in the earthward direction. The dynamic pressure jump associated with the transmitted TD is generally reduced from the value before the interaction. A fast compressional shock is excited ahead of the transmitted TD and propagates toward the Earth's magnetosphere. For the case in which the dynamic pressure is reduced behind the interplanetary TD, the pressure jump across the transmitted TD is substantially weakened, the bow shock moves in the sunward direction, and a rarefaction wave which propagates downstream is excited. We also simulate and discuss the interaction of a pair of tangential discontinuities, which may correspond to a magnetic hole, with the BS.

Wu, Bor-Han; Mandt, M. E.; Lee, L. C.; Chao, J. K.

1993-01-01

311

The Study of a Solar Storm and Its Interplanetary and Geomagnetic Effects  

NASA Astrophysics Data System (ADS)

We present a detailed study of a solar storm occurred on 2014 January 7. By using the remote-sensing solar observations from the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO), the eruptions of the solar flare and the coronal mass ejection (CME) are investigated. Based on the particle measurement from the Geostationary Operational Environmental Satellites (GOES) and the in-situ plasma measurement from the Advanced Composition Explorer (ACE), the solar energetic particle (SEP) event, the interplanetary CME (ICME), and its driven shock are analyzed. The influence of the solar storm on the geomagnetic fields is also analyzed. The results show that: (1) The impulsive eruption of the solar flare and the lift of the CME are temporally in accordance with each other. (2) The solar protons are mainly accelerated by the CME-driven shock when the CME travels to 7.7 solar radius, rather than by the magnetic reconnection in the flare. (3) The widths of the interplanetary shock sheath and the ICME itself are derived to be 0.22 AU and 0.26 AU, respectively. (4) The interplanetary shock and the ICME give rise to substorms and aurora, whereas no obvious geomagnetic storm is detected. The reason is that the ICME does not include a structure of the magnetic cloud (MC) or southward magnetic fields.

Qiu, B. H.; Li, C.

2015-01-01

312

Acceleration of electrons by interplanetary shocks  

NASA Technical Reports Server (NTRS)

Ion acceleration is a well known phenomenon at both interplanetary shocks, while there have been only a few reports concerning an acceleration of electrons at interplanetary shocks. The considered investigation reports that electron acceleration occurs at many shocks. The instrumentation used is discussed, taking into account the ISEE 3 (International Sun Earth Explorer) spacecraft and the electrostatic analyzer employed for the measurement of electrons. Changes in the electron distribution function caused by shocks are found to be quite varied. Some events show a simple step to a higher flux level, some show fluctuations as the flux rises, and some have one or more pulses at the time of the shock. Attention is given to data obtained on July 26, 1979, December 25, 1978, and November 12, 1978. A calculation of shock geometries is also reported.

Potter, D. W.

1981-01-01

313

Tin in a chondritic interplanetary dust particle  

NASA Technical Reports Server (NTRS)

Submicron platey Sn-rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029 A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Sn-rich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend toward nonchondritic volatile element abundances in chondritic IDPs. The observation confirms small-scale mineralogical heterogeneity in fine-grained chondritic porous interplanetary dust.

Rietmeijer, Frans J. M.

1989-01-01

314

Meteor matter in the interplanetary space. ????????? ???????? ? ???????????? ????????????  

NASA Astrophysics Data System (ADS)

Proceedings of the All-USSR symposium "Meteor matter in the interplanetary space" held in Kazan, USSR, Sept. 9-11, 1980. The 39 papers included cover the following topics: structure of the meteoroid complex in the vicinity of the Earth, observed structure of meteor showers, index of mass distribution in meteor showers, meteoroid streams and their evolution, densities and fragmentation of meteor bodies, meteor spectrums etc. The Proceedings are published in Russian, but includes the Contents and Abstracts in English.

Bel'kovich, O. I.; Babadzhanov, P. B.; Bronshten, V. A.; Sulejmanov, N. I.

1982-05-01

315

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

316

Integrated shielding systems for manned interplanetary spaceflight  

NASA Astrophysics Data System (ADS)

The radiation environment encountered by manned interplanetary missions can have a severe impact on both vehicle design and mission performance. This study investigates the potential impact of radiation protection on interplanetary vehicle design for a manned Mars mission. A systems approach was used to investigate the radiation protection requirements of the sum interplanetary environment. Radiation budgets were developed which result in minimum integrated shielding system masses for both nuclear and non-nuclear powered missions. A variety of system configurations and geometries were assessed over a range of dose constraints. For an annual dose equivalent rate limit of 50 rem/yr, an environmental shielding system composed of a habitat shield and storm shelter was found to result in the lowest total mass. For a limit of 65 rem/yr, a system composed of a sleeping quarters shield was least massive, and resulted in significantly reduced system mass. At a limit of 75 rem/yr, a storm shelter alone was found to be sufficient, and exhibited a further mass reduction. Optimal shielding system results for 10 MWe nuclear powered missions were found to follow along similar lines, with the addition of a reactor shadow shield. A solar minimum galactic cosmic ray spectrum and one anomalously large solar particle event during the course of a two year mission were assumed. Water was assumed for environmental radiation shielding.

George, Jeffrey A.

1992-01-01

317

Preliminary Analysis on the Interplanetary Cause of Geomagnetically Induced Current and Its Effect on Power Systems  

NASA Astrophysics Data System (ADS)

Using the detected events of geomagnetically induced current (GIC) in the Ling'ao nuclear power plant from 2004 to 2005, and focusing on the interplanetary cause of GIC and its effect on power systems, we have analyzed the corresponding solar driving sources and interplanetary solar wind structures, and performed spectral analysis on the most intense GIC event by means of wavelet transform. The results of this study show that: (1) Most GIC events were driven mainly by the halo coronal mass ejections, the interplanetary cause of GIC events includes the shock sheath, magnetic cloud, and multiplex interplanetary solar wind structure. (2) Based on the strongest GIC event on 2001 November 9, we find that the fluctuation of GIC in the earlier stage was related to the magnetic cloud boundary layer, and the variation of GIC intensity in the later stage was caused by magnetic cloud itself. (3) Compared to the frequency of the power system (50 Hz), the GIC can be equivalent to a quasi direct current. The energy of the GIC is embodied in the two time intervals in the wavelet power spectrum: the first interval is shown as an impulsive type and with a weaker intensity, and the second one is stronger. Regarding to the cumulative time of the transformer temperature rise caused by GIC, the second interval has a longer duration than the first one. Hence, during the second interval, it is more harmful to the power systems and devices. (4) With a correlation analysis, the correlations of the SYM-H index and dBx/dt with the GIC are significantly stronger than those of other geomagnetic indices with the GIC.

Kai-rang, WANG; Lian-guang, LIU; Yan, LI

2015-01-01

318

Inter-Relationship of Solar and interplanetary Phenomena During Solar Cycles 23 and 24  

NASA Astrophysics Data System (ADS)

We examine the variation of various phenomena, for example, the sunspot number and area, occurrence rate of solar energetic particle events, coronal mass ejections and interplanetary coronal mass ejections, the interplanetary magnetic field, solar magnetic field (“Sun as a star”), geomagnetic activity and the cosmic ray intensity during solar cycles 23 to 24. As we have discussed for previous cycles, there is a close association between these phenomena. For example, the onset of long-term cosmic ray modulation in cycle 24 is closely associated with not only an increase in the tilt angle of the heliospheric current sheet but also with abrupt increases in the solar and interplanetary magnetic field intensity at the Earth and the STEREO spacecraft, a temporary increase in the rate of interplanetary coronal mass ejections, an increase in the occurrence of corotating streams and solar energetic particle events, including the first 25 MeV proton event observed at both STEREO spacecraft and at Earth, and increases in geomagnetic activity (e.g., Dst, Kp, aa). Subsequent “steps down” in the cosmic ray intensity are associated with increases in the IMF strength, as is typical for the rising phases of cycles when the global solar field has A< 0. We also note the remarkably different time development of activity in the northern and southern hemispheres during cycle 24 compared to cycle 23, and evidence of short term (?6 month) quasi-periodicities in several of these phenomena that appear to characterize the development of this solar cycle, with periods of enhanced activity separated by intervals of lower activity.

Richardson, Ian; von Rosenvinge, Tycho; Cane, Hilary

2015-04-01

319

Influence of Temperature Anisotropy and Alpha-Particle Parameters on Calculated Interplanetary Shock Parameters  

NASA Astrophysics Data System (ADS)

In order to determine interplanetary shock parameters, we use Wind and ACE observations of shock passages in the solar wind. Magnetic field and plasma measurements by individual spacecraft are used with the nonlinear least squares fitting technique of Szabo [1994] with an improved error analysis to calculate the local shock parameters. Further improvement of the technique includes taking into account proton temperature anisotropy and alpha-particle parameters which results in higher accuracy of the calculated shock parameters. The shock parameters calculated at the locations of both spacecraft are then compared to estimate the global shapes of the observed shocks. We present statistics of the influence of proton temperature anisotropy and alpha particle parameters on the calculated shock parameters and discuss deviation of the shock global shape from the widely used planar assumption. The improved technique can be used to analyze STEREO and near-Earth observations of interplanetary shocks.

Koval, A.; Szabo, A.

2007-12-01

320

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

321

The interplanetary transport of solar cosmic rays  

NASA Technical Reports Server (NTRS)

Numerical solutions are presented for the propagation of solar cosmic rays in interplanetary space, including the effects of pitch-angle scattering and adiabatic focusing. The intensity-time profiles can be well fitted by a simple radial spatial diffusion equation with scattering mean-free path lambda(fit). The radial mean-free path so obtained is significantly larger than the true scattering mean-free path for low-rigidity particles due to both adiabatic focusing and the inapplicability of the diffusive approximation early in the event. The well-known discrepancy between lambda(fit) and the theoretical predictions may be resolved by these calculations.

Gombosi, T. I.; Owens, A. J.

1980-01-01

322

Magnetohydrodynamic modelling of interplanetary disturbances between the sun and earth  

NASA Technical Reports Server (NTRS)

A time-dependent, nonplanar, two-dimensional magnetohydrodynamic computer model is used to simulate a series, separately examined, of solar flare-generated shock waves and their subsequent disturbances in interplanetary space between the sun and the earth's magnetosphere. The 'canonical' or ansatz series of shock waves include initial velocities near the sun over the range 500 to 3500 km/s. The ambient solar wind, through which they propagate, is taken to be a steady state homogeneous plasma (that is, independent of heliolongitude) with a representative set of plasma and magnetic field parameters. Complete sets of solar wind plasma and magnetic field parameters are presented and discussed. Particular attention is addressed to the MHD model's ability to address fundamental operational questions vis-a-vis the long-range forecasting of geomagnetic disturbances. These questions are: (1) will a disturbance (such as the present canonical series of solar flare shock waves) produce a magnetospheric and ionospheric disturbance, and, if so, (2) when will it start, (3) how severe will it be, and (4) how long will it last? The model's output is used to compute various solar wind indices of current interest as a demonstration of the model's potential for providing 'answers' to these questions.

Dryer, M.; Smith, Z. K.; Wu, S. T.; Wang, J. F.; Gislason, G.; Han, S. M.; Smart, D. F.; Shea, M. A.

1984-01-01

323

Heliospheric Solar Wind Parameter Forecasting Using Interplanetary Scintillation (IPS) Observations  

NASA Astrophysics Data System (ADS)

At the University of California, San Diego (UCSD), remote-sensing analyses of the inner heliosphere have been regularly carried out using radio interplanetary scintillation (IPS) data for almost two decades employing data from the Solar-Terrestrial Environment Laboratory (STELab), Japan, IPS arrays. More recently, several other world locations have planned to join in this effort in order to provide more complete coverage at times other than those above the celestial meridian of the observing station. These analyses have measured and reconstructed three-dimensional (3D) solar wind structure throughout the time period when data are available. This enables a real-time forecast of solar wind density and velocity outward from the observations that is nearly complete over the whole heliosphere with a time cadence of about one day. When using the IPS velocity analyses, we can accurately convect outwards the solar surface background magnetic fields and thus can provide values of the field (radial and tangential components) throughout the global volume. In the inner heliosphere the results of these 3D analyses of density, velocity, and vector magnetic field have been forecast and compared successfully with in-situ measurements obtained near Earth, at STEREO, at Mars, at Venus, at MESSENGER, and at the Ulysses spacecraft. The resulting precise time-dependent results can also be used to provide an inner boundary of these parameters that can be further extrapolated outward to the edge of the heliosphere using current 3D-MHD modeling techniques.

Jackson, B. V.; Hick, P.; Buffington, A.; Yu, H.; Mejia-Ambriz, J. C.; Luckett, N.; Bisi, M. M.

2013-05-01

324

Multi-Spacecraft Observations of Interplanetary Shock Parameters  

NASA Astrophysics Data System (ADS)

We are presenting a study of interplanetary shock parameters (orientation, propagation speed, Mach number, and ?Bn, the angle between the shock normal and magnetic field) observed by multiple spacecraft in the solar wind. These parameters are calculated locally from the magnetic field and plasma (proton and alpha-particle) measurements of the Wind and ACE spacecraft by applying the modified Koval and Szabo [2008] technique that uses the anisotropic Rankine-Hugoniot conservation equations. The calculated local shock orientations and speeds are consequently used to predict the times of the shock arrival to the locations of the other spacecraft available in the solar wind assuming shock planarity and constant speed. We compare the predicted times with those observed as well as directly compare the Wind and ACE local shock normals and speeds with each other and with the global shock normal and speed determined from the four-spacecraft times and locations of the shock passages (when available). The agreement of the shock’s shape with the planar assumption is discussed based on the shock Mach number, ?Bn angle, and the shock driver. We also discuss the discrepancy of the other shock local parameters as a function of the inter-spacecraft separation.

Koval, A.; Szabo, A.

2009-12-01

325

Multi-spacecraft observations of interplanetary shock parameters  

NASA Astrophysics Data System (ADS)

We are presenting a study of interplanetary shock parameters (orientation, propagation speed, Mach number, and ?Bn, the angle between the shock normal and magnetic field) observed by multiple spacecraft in the solar wind. These parameters are calculated locally from the magnetic field and plasma (proton and alpha-particle) measurements of the Wind and ACE spacecraft by applying the modified Koval and Szabo [2008] technique that uses the anisotropic Rankine-Hugoniot conservation equations. The calculated local shock orientations and speeds are consequently used to predict the times of the shock arrival to the locations of the other spacecraft available in the solar wind assuming shock planarity and constant speed. We compare the predicted times with those observed as well as directly compare the Wind and ACE local shock normals and speeds with each other and with the global shock normal and speed determined from the four-spacecraft times and locations of the shock passages (when available). The agreement of the shock's shape with the planar assumption is discussed based on the shock Mach number, ?Bn angle, and the shock driver. We also discuss the discrepancy of the other shock local parameters as a function of the inter-spacecraft separation.

Koval, Andriy; Szabo, Adam

2010-05-01

326

Observations of Electromagnetic Whistler Precursors at Supercritical Interplanetary Shocks  

NASA Technical Reports Server (NTRS)

We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. They have rest frame frequencies f(sub ci) < f much < f(sub ce) and wave numbers 0.02 approx < k rho (sub ce) approx <. 5.0. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves. Al though the precursors can have delta B/B(sub o) as large as 2, fluxgate magnetometer measurements show relatively laminar shock transitions in three of the four events.

Wilson, L. B., III; Koval, A.; Szabo, Adam; Breneman, A.; Cattell, C. A.; Goetz, K.; Kellogg, P. J.; Kersten, K.; Kasper, J. C.; Maruca, B. A.; Pulupa, M.

2012-01-01

327

The Magnetic Helicity Budget of Solar Active Regions: from the Photosphere to Magnetic Clouds  

NASA Astrophysics Data System (ADS)

Magnetic helicity is one of the few solar physical magnitudes which is conserved even in non-ideal magnetohydrodynamics on time scales shorter than the global diffusion time. Magnetic helicity is generated in the solar interior, buoyant flux tubes transport it through the convective zone and inject it into the solar corona, where photospheric large scale (differential rotation) and small scale motions also contribute. Increasing observational evidence indicates that magnetic helicity of a given dominant sign is injected in each solar hemisphere and that this sign does not change during the solar cycle. Being this so, magnetic helicity would accumulate incensantly unless the Sun finds a way the get rid of it. Coronal mass ejections (CMEs) are the phenomena through which magnetic helicity can be ejected from the Sun into the interplanetary medium. Twisted magnetic plasma structures, of which magnetic clouds are a subset, are frequently observed in the near Earth environment. Based on observations and modelling of two well studied CME productive active regions (ARs), we evaluate the relative importance of the different sources of coronal magnetic helicity in these ARs. We compute the helicity ejected in CMEs associating every one of them to an interplanetary magnetic cloud. For this computation we use observational averaged values for the cloud parameters, together with standard cloud models. We find that the ejected magnetic helicity can only come from the twist (subphotospheric origin) inherent to the flux tube forming the AR. This kind of studies is aimed to characterize the CME ejection mechanism and to improve our forescasting ability of CMEs.

Mandrini, C. H.

328

Planetary Science Decadal Survey White Paper: Interplanetary Dust  

Microsoft Academic Search

The goal of the interplanetary dust decadal survey white paper is to define the main questions facing the field over the next 10 years and determine what focus of reasearch, technology, and mission resources will best address these questions. Interplanetary dust particles (IDPs), largely collected near the Earth's orbit and on the Earth itself, represent the most inexpensive sample return

Ashley J. Espy; A. Graps; N. Altobelli; J. Blum; D. Brownlee; H. Campins; S. Close; W. Cooke; S. Dermott; G. Drolshagen; E. Grün; M. Horányi; M. Hedman; P. Jenniskens; T. Kehoe; S. Kortenkamp; H. Krüger; M. Kuchner; J. Liou; C. Lisse; G. Madsen; I. Mann; B. May; N. Meyer-Vernet; D. Nesvorny; P. Palumbo; W. Reach; C. Russell; R. Srama; M. Sykes; J. Trigo-Rodríguez; J. Vaubaillon; H. Weaver; M. Zolensky

2009-01-01

329

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.

330

CME Magnetic Structure and Magnetic Cloud Signature  

Microsoft Academic Search

An interplanetary coronal mass ejection (ICME) is the counterpart of a coronal mass ejection by definition. However, the relationship between the magnetic structures of the CMEs and that of the situ observations of ICMEs is still quite far from clear, due to observational gaps and the state of our understanding of CMEs. Some studies suggested that the magnetic cloud (MC,

Yan Li; J. Luhmann

2006-01-01

331

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

332

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

333

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

334

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

335

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

336

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

337

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

338

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

339

Interplanetary approach optical navigation with applications  

NASA Technical Reports Server (NTRS)

The use of optical data from onboard television cameras for the navigation of interplanetary spacecraft during the planet approach phase is investigated. Three optical data types were studied: the planet limb with auxiliary celestial references, the satellite-star, and the planet-star two-camera methods. Analysis and modelling issues related to the nature and information content of the optical methods were examined. Dynamic and measurement system modelling, data sequence design, measurement extraction, model estimation and orbit determination, as relating optical navigation, are discussed, and the various error sources were analyzed. The methodology developed was applied to the Mariner 9 and the Viking Mars missions. Navigation accuracies were evaluated at the control and knowledge points, with particular emphasis devoted to the combined use of radio and optical data. A parametric probability analysis technique was developed to evaluate navigation performance as a function of system reliabilities.

Jerath, N.

1978-01-01

340

Interplanetary space transport using inertial fusion propulsion  

SciTech Connect

In this paper, we indicate how the great advantages that ICF offers for interplanetary propulsion can be accomplished with the VISTA spacecraft concept. The performance of VISTA is expected to surpass that from other realistic technologies for Mars missions if the energy gain achievable for ICF targets is above several hundred. Based on the good performance expected from the U. S. National Ignition Facility (NIF), the requirements for VISTA should be well within the realm of possibility if creative target concepts such as the fast ignitor can be developed. We also indicate that a 6000-ton VISTA can visit any planet in the solar system and return to Earth in about 7 years or less without any significant physiological hazards to astronauts. In concept, VISTA provides such short-duration missions, especially to Mars, that the hazards from cosmic radiation and zero gravity can be reduced to insignificant levels. VISTA therefore represents a significant step forward for space-propulsion concepts.

Orth, C.D.

1998-04-20

341

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

342

Multi-spacecraft observations of interplanetary coronal mass ejections  

NASA Astrophysics Data System (ADS)

I present an overview of interplanetary coronal mass ejections (ICMEs) observed during the first two years of the Solar TErrestrial RElation Observatory (STEREO) mission. The multi-view capability of the STEREO spacecraft combined with the spacecraft observations at L1 (ACE, Wind) provides unprecedented opportunity to study the large-scale properties of ICMEs. From the beginning of the STEREO science mission (January 2007) 18 large-scale ICMEs (radial diameter > 0.1 AU and/or the peak magnetic field magnitude > 10 nT) have been observed by the STEREO and/or the L1 spacecraft. The ICME on June 2007 was the last ICME that was encountered by all spacecraft in consideration. At that time the STEREO spacecraft were separated by about 12 degrees. For the majority of cases the typical ICME signatures were clearly identified only at one of the observing sites implying that the longitudinal scale sizes of the ICMEs are relatively small at solar minimum. I will discuss the general properties of the identified ICMEs and the differences in their characteristics when collected by distant spacecraft. In particular, I will discuss how two-point measurements can be used to increase our understanding of the global ICME geometry and to improve the flux rope models.

Kilpua, E.

2009-04-01

343

Interplanetary shock shapes: comparison of local and global parameters  

NASA Astrophysics Data System (ADS)

We are presenting a study of the shapes of interplanetary shocks observed by multiple spacecraft. The shock normal orientation and propagation speed are calculated locally from the magnetic field and plasma measurements of the Wind spacecraft by applying the Koval and Szabo [2008] technique which uses the isotropic Rankine-Hugoniot (RH) conservation equations. We have modified the technique by applying the anisotropic and multi-ion RH conservation equations in order to improve the accuracy of the calculated parameters. These local parameters are consequently used to predict the times of the shock arrival to the locations of the other spacecraft available in the solar wind assuming shock planarity and constant propagation speed. We compare the predicted times with those observed as well as compare the Wind local shock normal orientation and propagation speed with the corresponding global parameters determined from the four-spacecraft locations and times of the shock passages (when available). The agreement of the shock shapes with the planar assumption is discussed based on the shock drivers. We also discuss the influence of temperature anisotropy and alpha-particle parameters on the accuracy of the locally calculated shock parameters. Determining the true orientation of CME-driven shocks is important for a better understanding of particle acceleration processes.

Koval, A.; Szabo, A.

2008-12-01

344

Using dynamic AMR to simulate geoeffective interplanetary transients  

NASA Astrophysics Data System (ADS)

It is of fundamental importance for solar, heliospheric, and magnetospheric physics to explore the complex dynamic evolution and geoeffectiveness of coronal transients, commonly known as CMEs, all the way from their origin at the Sun, through the interplanetary space, to Earth. In this light, three-dimensional (3D) magnetohydrodynamic (MHD) simulations provide excellent grounds for studying the complexity in dynamics of this and other solar phenomena. We present some results on state-of-art numerical experiments of CME propagation, including dynamic Adaptive Mesh Refinement (AMR). All computations presented here are carried out using the BATS-R-US (Block Adaptive Tree Solarwind Roe Upwind Scheme) code and involve 3D time-dependent MHD. The CME is initiated through an eruption of double-twisted magnetic flux rope originating from the solar corona. The MHD shock formed ahead of the solar transient is essential in determining geoeffective events. The physics based AMR allows us to examine in great detail the complexity of the CME development and propagation on the particular ray Sun-Earth. The applied numerical algorithm is designed to use optimal computational resources for the sake of tracing CMEs with very high spatial resolution all the way from Sun to Earth, and beyond. We further discuss the differences in using various criteria for mesh refinement on the overall physical picture of the CME dynamics.

Roussev, I.; Manchester, W.; Gombosi, T.; de Zeeuw, D.; Sokolov, I.; Toth, G.

345

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

346

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

347

Topological quantization of ensemble averages  

Microsoft Academic Search

We define the current of a quantum observable and, under well-defined conditions, we connect its ensemble average to the index of a Fredholm operator. The present work builds on a formalism developed by Kellendonk and Schulz-Baldes (2004 J. Funct. Anal. 209 388) to study the quantization of edge currents for continuous magnetic Schrödinger operators. The generalization given here may be

Emil Prodan

2009-01-01

348

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

349

Differences in the quasi-biennial oscillation and quasi-triennial oscillation characteristics of the solar, interplanetary, and terrestrial parameters  

Microsoft Academic Search

The 12-month running means (12 m) and the parameter (12–36 m) representing the quasi-biennial oscillation (QBO) and quasi-triennial oscillation (QTO) were examined and spectrally analyzed for several solar, interplanetary, and terrestrial parameters. Solar indices (including solar open magnetic flux in solar latitudes <45°) had a QBO in the form of double peaks separated by ?2–3 years during sunspot maximum years

R. P. Kane

2005-01-01

350

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

351

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

352

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

353

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

354

Magnetosheath parameter profiles under different magnetic field orientations  

NASA Astrophysics Data System (ADS)

We used 6-year Themis measurements of plasma and magnetic field parameters in the magnetosheath and constructed a map of their averaged values. To creation of map profiles, the Jelinek et al. (2012) model of both the bow shock and magnetopause was applied. We present the changes of the magnetosheath spatial profiles under various interplanetary magnetic field orientations. An advantage of the procedure is that the same spacecraft measurements were used for construction of model boundaries and for determination of averaged profiles of plasma parameters and that our large data set includes one-half of solar cycle. Moreover, we compare profiles of the plasma density, velocity and temperature with those obtained from the Spreiter et al. (1966) and MHD (BATS-R-US) models. We discuss deviations between experimental and predicted profiles for different conditions along one-half solar cycle.

Jelinek, Karel; Nemecek, Zdenek; Safrankova, Jana; Samsonov, Andrey

355

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

356

Origins and Dynamics of Interplanetary Dust Particles  

NASA Technical Reports Server (NTRS)

This is a final report for research supported by the National Aeronautics and Space Administration issued through the Office of Space Science Planetary Geology and Geophysics Program, covering all relevant activities during its 3-year period of funding from 02/01/2002 through to 01/31/2005. The ongoing aim of the research supported through this grant, and now through a successor award, is to investigate the origin of interplanetary dust particles (IDPs) and their dynamical and collisional evolution, in order to: (1) understand the provenance of zodiacal cloud particles and their transport from their source regions to the inner solar system; (2) produce detailed models of the zodiacal cloud and its constituent components; (3) determine the origin of the dust particles accreted by the Earth; (4) ascertain the level of temporal variations in the dust environment of the inner solar system and the accretion rate of IDPs by the Earth, and evaluate potential effects on global climate; and to (5) exploit this research as a basis for interpreting the structure observed in exozodiacal clouds that may result from the collisional evolution of planetesimals and the presence of unseen planets.

Dermott, Stanley F.

2005-01-01

357

Evolution of MHD turbulence through interplanetary shocks  

NASA Astrophysics Data System (ADS)

It is well established that as the solar wind expands into outer parts of our planetary system, an additional heating is observed. Many mechanisms have been proposed to account, at least partially, for this phenomenon. One of them is a dissipation of large scale variations of all solar wind parameters into the thermal energy via turbulent cascades. Thus, a study of the frequency spectra of plasma parameters in the so-called kinetic range where the ion and electron kinetic effects dominate is of high importance. The BMSW instrument onboard the Spektr-R spacecraft provides a high-time resolution data (31 ms) of the ion flux, velocity, density, and temperature suitable for an analysis of the frequency spectra up to 10 Hz. The paper focuses on the statistical analysis of fast forward low-Mach number interplanetary shocks. We discuss the upstream and downstream plasma parameters that encode the properties of the turbulence such as spectral slopes and breaks in the frequency spectra. We have found that the power of downstream fluctuations rises by an order of magnitude in a broad range of frequencies independently of its upstream value but the slope of the spectrum on the kinetic scale (?3-8 Hz) has been found to be statistically steeper downstream than upstream of the shock. The time needed to a full relaxation to the pre-shock spectral shape is as long as several hours.

Pitna, Alexander; Nemecek, Zdenek; Safrankova, Jana; Goncharov, Oleksandr; Nemec, Frantisek

358

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

359

Magnetospheric Response to Interplanetary Field Enhancements: Coordinated Space-based and Ground-based Observations  

NASA Astrophysics Data System (ADS)

In general, asteroids, meteoroids and dust do not interact with the plasma structures in the solar system, but after a collision between fast moving bodies the debris cloud contains nanoscale dust particles that are charged and behave like heavy ions. Dusty magnetic clouds are then accelerated to the solar wind speed. While they pose no threat to spacecraft because of the particle size, the coherency imposed by the magnetization of the cloud allows the cloud to interact with the Earth's magnetosphere as well as the plasma in the immediate vicinity of the cloud. We call these clouds Interplanetary Field Enhancements (IFEs). These IFEs are a unique class of interplanetary field structures that feature cusp-shaped increases and decreases in the interplanetary magnetic field and a thin current sheet. The occurrence of IFEs is attributed to the interaction between the solar wind and dust particles produced in inter-bolide collisions. Previous spacecraft observations have confirmed that IFEs move with the solar wind. When IFEs strike the magnetosphere, they may distort the magnetosphere in several possible ways, such as producing a small indentation, a large scale compression, or a glancing blow. In any event if the IFE is slowed by the magnetosphere, the compression of the Earth's field should be seen in the ground-based magnetic records that are continuously recorded. Thus it is important to understand the magnetospheric response to IFE arrival. In this study, we investigate the IFE structure observed by spacecraft upstream of the magnetosphere and the induced magnetic field perturbations observed by networks of ground magnetometers, including the THEMIS, CARISMA, McMAC arrays in North America and the IMAGE array in Europe. We find that, in a well-observed IFE event on December 24, 2006, all ground magnetometer stations observed an impulse at approximately 1217 UT when the IFE was expected to arrive at the Earth's magnetopause. These ground stations spread across many latitudes and local times, indicating that the impulse can penetrate magnetic shells as well as propagate along field lines. The equivalent currents in the ionosphere inferred from ground magnetometer measurements show a single vortex with a center located in the morning sector where the IFE impacted the magnetopause. Our observations suggest that the IFE-induced current system in the magnetosphere differs from those caused by sudden impulses.

Chi, Peter; Russell, Christopher; Lai, Hairong

2014-05-01

360

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

361

Magnetic Flux Conservation in the Heliosheath Including Solar Cycle Variations of Magnetic Field Intensity  

NASA Astrophysics Data System (ADS)

In the heliosheath (HS), Voyager 2 has observed a flow with constant radial velocity and magnetic flux conservation. Voyager 1, however, has observed a decrease in the flow’s radial velocity and an order of magnitude decrease in magnetic flux. We investigate the role of the 11 yr solar cycle variation of the magnetic field strength on the magnetic flux within the HS using a global 3D magnetohydrodynamic model of the heliosphere. We use time and latitude-dependent solar wind velocity and density inferred from Solar and Heliospheric Observatory/SWAN and interplanetary scintillations data and implemented solar cycle variations of the magnetic field derived from 27 day averages of the field magnitude average of the magnetic field at 1 AU from the OMNI database. With the inclusion of the solar cycle time-dependent magnetic field intensity, the model matches the observed intensity of the magnetic field in the HS along both Voyager 1 and 2. This is a significant improvement from the same model without magnetic field solar cycle variations, which was over a factor of two larger. The model accurately predicts the radial velocity observed by Voyager 2; however, the model predicts a flow speed ?100 km s?1 larger than that derived from LECP measurements at Voyager 1. In the model, magnetic flux is conserved along both Voyager trajectories, contrary to observations. This implies that the solar cycle variations in solar wind magnetic field observed at 1 AU does not cause the order of magnitude decrease in magnetic flux observed in the Voyager 1 data.

Michael, A. T.; Opher, M.; Provornikova, E.; Richardson, J. D.; Tóth, G.

2015-04-01

362

Orientations of LASCO Halo CMEs and Their Connection to the Flux Rope Structure of Interplanetary CMEs  

E-print Network

Coronal mass ejections (CMEs) observed near the Sun via LASCO coronographic imaging are the most important solar drivers of geomagnetic storms. ICMEs, their interplanetary, near-Earth counterparts, can be detected in-situ, for example, by the Wind and ACE spacecraft. An ICME usually exhibits a complex structure that very often includes a magnetic cloud (MC). They can be commonly modelled as magnetic flux ropes and there is observational evidence to expect that the orientation of a halo CME elongation corresponds to the orientation of the flux rope. In this study, we compare orientations of elongated CME halos and the corresponding MCs, measured by Wind and ACE spacecraft. We characterize the MC structures by using the Grad-Shafranov reconstruction technique and three MC fitting methods to obtain their axis directions. The CME tilt angles and MC fitted axis angles were compared without taking into account handedness of the underlying flux rope field and the polarity of its axial field. We report that for about 64% of CME-MC events, we found a good correspondence between the orientation angles implying that for the majority of interplanetary ejecta their orientations do not change significantly (less than 45 deg rotation) while travelling from the Sun to the near Earth environment.

V. Yurchyshyn; Q. Hu; R. P. Lepping; B. J. Lynch; J. Krall

2007-03-23

363

Interplanetary Coronal Mass Ejections, Associated Features, and Transient Modulation of Galactic Cosmic Rays  

NASA Astrophysics Data System (ADS)

Interplanetary structures such as shocks, sheaths, interplanetary counterparts of coronal mass ejections (ICMEs), magnetic clouds, and corotating interaction regions (CIRs) are of special interest for the study of the transient modulation of galactic cosmic rays (GCRs). These structures modulate the GCR intensity with varying amplitudes and recovery-time profiles. It is known that ICMEs are mainly responsible for Forbush decreases in the GCR intensity. However, not all of the ICMEs produce such decreases in GCR intensity. We utilize GCR intensity data recorded by neutron monitors and solar-wind plasma/field data during the passage of ICMEs with different features and structures, and we perform a superposed-epoch analysis of the data. We also adopt the best-fit approach with suitable functions to interpret the observed similarities and differences in various parameters. Using the GCR-effectiveness as a measure of the cosmic-ray response to the passage of ICMEs, about half of the ICMEs identified during 1996 - 2009 are found to produce moderate to very large intensity depressions in GCR intensity. The ICMEs associated with halo CMEs, magnetic-cloud (MC) structures, bidirectional superthermal electron (BDE) signatures, and those driving shocks are 1.5 to 4 times more GCR effective than the ICMEs not associated with these structures/features. Further, the characteristic recovery time of GCR intensity due to shock/BDE/MC/halo-CME-associated ICMEs is larger than those due to ICMEs not associated with these structures/features.

Kumar, Anand; Badruddin

2014-06-01

364

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

365

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

366

Medusa: Nuclear explosive propulsion for interplanetary travel  

NASA Astrophysics Data System (ADS)

Because of the deleterious effects of galactic cosmic radiation, solar flares, zero gravity and psychological stress, there is strong motivation to develop high-specific-impulse and high-thrust spacecraft for rapid transport of astronauts between planets. A novel spacecraft design is presented using a large lightweight sail (spinnaker) driven by pressure pulses from a series of nuclear explosions. The spacecraft appears to be a singularly competent and economical vehicle for high-speed interplanetary travel. The mass of the spinnaker is theoretically independent of the size of its canopy or the length of its tethers. Consequently, the canopy can be made very large to minimize radiation damage from the nuclear explosions and the tethers can be made very long to mitigate radiation hazard to the crew. The pressure from the nuclear explosion imparts a large impulsive acceleration to the lightweight spinnaker, which must be translated to a small smooth acceleration of the space capsule either by using the elasticity of the tethers or a servo winch in the space capsule, or a combination of the two. If elasticity alone is used, the maximum acceleration suffered by the space capsule is inversely propotional to the tether length. The use of very long tethers allows the spacecraft to achieve high velocities without using an exceedingly large number of bombs, a feature unavailable to previous forms of nuclear-explosive propulsion. Should the political questions connected with an unconventional use of nuclear explosives be favorably resolved, the proposal will be a good candidate for propulsion in the Mars mission.

Solem, Johndale C.

1993-01-01

367

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

368

DIRECT OBSERVATION OF THE INTERPLANETARY PLASMA  

Microsoft Academic Search

Results obtained with the satellite Explorer X, which was designed to ; measure properties of the magnetic field and of the ionized gas over a region ; starting close to the earth and extending to a polnt where effects of the earth's ; magnetic field should be negligible, are presented. Instrumentation and the ; experimental conditions for the measure ments

H. S. Bridge; C. Dilworth; A. J. Lazarus; E. F. Lyons; B. Rossi; F. Scherb

1961-01-01

369

Hydromagnetic waves, turbulence, and collisionless processes in the interplanetary medium  

NASA Technical Reports Server (NTRS)

An extended discussion is conducted concerning the origin and evolution of interplanetary hydromagnetic waves and turbulence, and their influence on the large scale dynamics of the solar wind. The solar wind is at present the preeminent medium for the study of hydromagnetic waves and turbulence, providing an opportunity for advancement of understanding of the most fundamental processes of the astrophysical plasmas. All interplanetary fluctuations whose time scale is observed to be greater than 1 sec can be regarded as hydromagnetic fluctuations. It has been found to be simplest, and generally very satisfactory, to model interplanetary variations as fluctuations in an MHD fluid. Attention is given to the classification of wave modes, geometrical hydromagnetics, Alfven wave pressure, rugged invariants, and the kinetic theory of collisionless processes.

Barnes, A.

1983-01-01

370

Interplanetary Program to Optimize Simulated Trajectories (IPOST). Volume 3: Programmer's manual  

NASA Technical Reports Server (NTRS)

The Interplanetary Program to Optimize Space Trajectories (IPOST) is intended to support many analysis phases, from early interplanetary feasibility studies through spacecraft development and operations. Here, information is given on the IPOST code.

Hong, P. E.; Kent, P. D.; Olson, D. W.; Vallado, C. A.

1992-01-01

371

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

372

Theoretical interpretation of Traveling Interplanetary Phenomena and their solar origins  

NASA Technical Reports Server (NTRS)

A review is made of recent theoretical studies on Traveling Interplanetary Phenomena (TIP) and their possible solar origins in the context of mathematical methods and physical processes. Flare-generated interplanetary shocks are used as examples to illustrate the following set of contrasting approaches to the phenomena: analytical vs numerical, hydrodynamic vs magnetohydrodynamic, dissipative vs non-dissipative, continuum/macroscopic vs kinetic/microscopic. It is suggested in conclusion that future research should emphasize continuum/macroscopic physical processes together with the kinetic approach to deepen understanding of microscopic interactions.

Wu, S. T.

1980-01-01

373

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

374

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

375

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

376

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

377

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

378

Effects on the Mars-Solar Wind Interaction of Interplanetary Field Sector  

NASA Astrophysics Data System (ADS)

One of the goals of the upcoming MAVEN mission to Mars is to investigate the effects of the crustal remanent fields on the solar wind plasma interaction and the upper atmosphere. The MGS Electron Reflectometer and magnetometer observations can be used to test the idea that, if the future data from the electron spectrometer (SWEA) are separated for the two prevalent interplanetary field orientations (Parker spirals 'toward' and 'away' from the Sun), one may be able to detect specific differences in the patterns of locations of open magnetic fields (where photoelectrons can escape from Mars' ionosphere into space, or sheath electrons get in). We use pairs of BATS-R-US MHD models of the Mars-solar wind interaction, in a manner similar to that tested by Liemohn et al. in 2007 on Mars Express ELS electron data, to define these patterns of expected photo-electron detections on a global scale. The models used have the strongest southern hemisphere crustal fields at noon or midnight, a matter of importance in such investigations because these patterns will be sensitive to the local time of those fields. We compare some MGS data-based maps of the time periods selected for their open field signatures in the pitch angle distributions and energy spectra, and separated by interplanetary field orientation inferred from Mars magnetosheath observations. This exercise illustrates the power (and necessity) of the global model comparisons as a means of interpreting the very complex Mars-solar wind interaction and its effects.

Ulusen, D.; Ma, Y.; Brain, D.; Luhmann, J. G.; Mitchell, D.; Lillis, R.

2013-09-01

379

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

380

Relationship of Interplanetary Shock Micro and Macro Characteristics: A Wind Study  

NASA Astrophysics Data System (ADS)

The non-linear least squared MHD fitting technique of Szabo [1994] has been recently further refined to provide realistic confidence regions for interplanetary shock normal directions and speeds. Analyzing Wind observed interplanetary shocks from 1995 to 2001, macro characteristics such as shock strength, Theta Bn and Mach numbers can be compared to the details of shock micro or kinetic structures. The now commonly available very high time resolution (11 or 22 vectors/sec) Wind magnetic field data allows the precise characterization of shock kinetic structures, such as the size of the foot, ramp, overshoot and the duration of damped oscillations on either side of the shock. Detailed comparison of the shock micro and macro characteristics will be given. This enables the elucidation of shock kinetic features, relevant for particle energization processes, for observations where high time resolution data is not available. Moreover, establishing a quantitative relationship between the shock micro and macro structures will improve the confidence level of shock fitting techniques during disturbed solar wind conditions.

Szabo, A.; Koval, A.

2008-12-01

381

Relationship of Interplanetary Shock Micro and Macro Characteristics: A Wind Study  

NASA Technical Reports Server (NTRS)

The non-linear least squared MHD fitting technique of Szabo 11 9941 has been recently further refined to provide realistic confidence regions for interplanetary shock normal directions and speeds. Analyzing Wind observed interplanetary shocks from 1995 to 200 1, macro characteristics such as shock strength, Theta Bn and Mach numbers can be compared to the details of shock micro or kinetic structures. The now commonly available very high time resolution (1 1 or 22 vectors/sec) Wind magnetic field data allows the precise characterization of shock kinetic structures, such as the size of the foot, ramp, overshoot and the duration of damped oscillations on either side of the shock. Detailed comparison of the shock micro and macro characteristics will be given. This enables the elucidation of shock kinetic features, relevant for particle energization processes, for observations where high time resolution data is not available. Moreover, establishing a quantitative relationship between the shock micro and macro structures will improve the confidence level of shock fitting techniques during disturbed solar wind conditions.

Szabo, Adam; Koval, A

2008-01-01

382

Observations of possible injection of interplanetary oxygen into the inner magnetosphere  

NASA Astrophysics Data System (ADS)

With the Advanced Composition Explorer's (ACE) Electron Proton and Alpha Monitor (EPAM) instrument being in a halo orbit about L1 and the Van Allen Probe's Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument being in an eccentric orbit through the inner magnetosphere, the two instruments are situated perfectly for observing the inner magnetospheric response to energetic interplanetary particle events. Both instruments are designed to measure electrons and ions with energies between tens of keV and a few MeV, depending upon particle species. Using a new data analysis technique we've developed, the EPAM instrument can provide high energy-resolution, species-resolved energy spectra for a number of ion species including helium and oxygen which RBSPICE is designed to observe. Between May 22nd and 26th of 2013, EPAM observed an energetic particle event with a nearly flat energy spectra and greatly enhanced helium and oxygen composition. RBSPICE measured a strong surge in oxygen flux, but saw no correspondingly strong increase in the helium flux. We present a detailed analysis and comparison of the energetic ion spectra, composition, and timing measured by the ACE and the Van Allen Probes instruments in conjunction with magnetic field and energetic particle measurements from other spacecraft for this event, and provide a discussion on the injection of interplanetary oxygen into the inner magnetosphere.

Patterson, James Douglas; Manweiler, Jerry Wayne; Gerrard, Andrew; Bonnell, John; Bounds, Scott; Gkioulidou, Matina; Mitchell, Donald G.; Lanzerotti, Louis J.

2015-04-01

383

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.

California Energy Commission

384

Coupled Hydromagnetic Wave Excitation and Ion Acceleration at an Evolving Coronal/Interplanetary Shock  

NASA Astrophysics Data System (ADS)

An analytical quasilinear theory is presented for the evolution of a ``gradual'' event consisting of solar energetic particles (SEPs) accelerated at an evolving coronal/interplanetary shock. The upstream ion transport is described by the two-stream moments of the focused transport equation, which accommodate the large streaming anisotropies observed near event onset. The proton transport equations and a wave kinetic equation are solved together for the coupled behavior of the hydromagnetic waves and the energetic protons. The theory includes diffusive shock acceleration, ion advection with the solar wind, spatial diffusion upstream of the shock, magnetic focusing, wave excitation by the energetic protons, and minor ions as test particles. A number of approximations are made for analytical tractability. The predictions reproduce the observed phases of most gradual SEP events: onset, a ``plateau'' with large streaming anisotropy, an ``energetic storm particle'' (ESP) enhancement prior to shock passage, and the decaying ``invariant spectra'' after shock passage. The theory treats naturally the transition from a scatter-dominated sheath adjacent to the shock where the wave intensity is enhanced to the nearly scatter-free ion transport in interplanetary space. The plateau is formed by ions that are extracted from the outer edge of the scatter-dominated sheath by magnetic focusing and escape into interplanetary space; it corresponds quantitatively to the ``streaming limit'' identified and interpreted in gradual events by D. V. Reames and C. K. Ng. The ion energy spectra at the shock have the standard power-law form dependent on shock strength, which is expected for diffusive shock acceleration, with a high-energy cutoff whose form is determined self-consistently by the ion escape rate. The increased shock strength, magnetic field magnitude, and injection energies close to the Sun account for the observed predominance of high-energy ions early in the event. The downstream ion transport is determined under two extreme assumptions: (i) vanishing diffusive transport and (ii) effective diffusive transport leading to small ion spatial gradients. The latter assumption reproduces the invariant spectra, spatial gradients, and exponential temporal decay observed in the late phase of many events. The minor ion distributions exhibit fractionation due to rigidity-dependent transport and acceleration. However, their energy spectra, spatial gradients, and high-energy cutoffs do not reproduce observed forms and lead to excessive fractionation. The origin of these discrepancies is probably the neglect of nonlinear processes. Although not easily incorporated in the theory, these processes could substantially modify the predicted wave intensity. An illustrative calculation assuming an arbitrary power-law form for the wave intensity demonstrates the sensitive dependence of ion fractionation on the power-law index.

Lee, Martin A.

2005-05-01

385

Theoretical MHD (magnetohydrodynamic) simulations of coronal transients and interplanetary observations  

Microsoft Academic Search

A major long-range goal of theoretical simulations of solar-generated disturbances (transients, coronal holes, etc.) is the realistic modeling of a propagating disturbance from the sun into and throughout interplanetary space. Simulations of this kind, using MHD fluid theory, must always be confronted with observations in order to assess the degree to which one or the other is inadequate. We describe

M. Dryer; R. S. Steinolfson; Z. K. Smith

1982-01-01

386

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

Microsoft Academic Search

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

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

2006-01-01

387

DESIGN AND TEST OF A BREADBOARD INTERPLANETARY LASER TRANSPONDER  

Microsoft Academic Search

At the last SLR Workshop in Shanghai, the feasibility of an asynchronous (i.e. independently firing) interplanetary laser transponder, capable of ranging between Earth and Mars and using the automated SLR2000 system as an Earth base station, was suggested. Since that time, we have received a small amount of discretionary funding to further explore the transponder concept and to develop and

John Degnan; Jan McGarry; Phillip Dabney; Thomas Zagwodzki; Michael Tierney; Matthew Weatherly

2000-01-01

388

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

389

Congestion Aware Routing Strategies for DTN-Based Interplanetary Networks  

Microsoft Academic Search

The networking and communication challenges posed by interplanetary environments make the design and the deployment of complex telecommunication infrastructures particularly difficult, especially with regard to routing and congestion control issues. To this end, the paper proposes a congestion-aware routing paradigm that applies multi attribute decision making (MADM) concepts for next-hop selection, by formulating an optimisation problem and proposing some possible

Igor Bisio; Mario Marchese; Tomaso De Cola

2008-01-01

390

Pioneer 10 studies of interplanetary shocks at large heliocentric distances  

Microsoft Academic Search

Pioneer 10 Ames plasma analyzer data collected in the 6.1 to 12.6 AU range of heliocentric distances (November 1974 to April 1977) have been examined for interplanetary shock waves. Eighteen shock signatures have been identified, with four of these being of the reverse type and the remainder the forward type. Sonic Mach numbers in the range from 3 to 10

J. D. Mihalov; J. H. Wolfe

1979-01-01

391

Interplanetary Lyman $?$ line profiles: variations with solar activity cycle  

E-print Network

Interplanetary Lyman alpha line profiles are derived from the SWAN H cell data measurements. The measurements cover a 6-year period from solar minimum (1996) to after the solar maximum of 2001. This allows us to study the variations of the line profiles with solar activity. These line profiles were used to derive line shifts and line widths in the interplanetary medium for various angles of the LOS with the interstellar flow direction. The SWAN data results were then compared to an interplanetary background upwind spectrum obtained by STIS/HST in March 2001. We find that the LOS upwind velocity associated with the mean line shift of the IP \\lya line varies from 25.7 km/s to 21.4 km/s from solar minimum to solar maximum. Most of this change is linked with variations in the radiation pressure. LOS kinetic temperatures derived from IP line widths do not vary monotonically with the upwind angle of the LOS. This is not compatible with calculations of IP line profiles based on hot model distributions of interplanetary hydrogen. We also find that the line profiles get narrower during solar maximum. The results obtained on the line widths (LOS temperature) show that the IP line is composed of two components scattered by two hydrogen populations with different bulk velocities and temperature. This is a clear signature of the heliospheric interface on the line profiles seen at 1 AU from the sun.

Eric Quémerais; Rosine Lallement; Jean-Loup Bertaux; Dimitra Koutroumpa; John Clarke; Erkki Kyrola; Walter Schmidt

2006-09-11

392

Interplanetary space-A new laboratory for rarefied gas dynamics  

NASA Technical Reports Server (NTRS)

Interplanetary space provides simultaneously the best vacuum available to man and, because of the solar wind, a tenuous and unsteady high-speed outflow of predominantly hydrogen gas from the sun, a remarkable variety of rarefied gasdynamics phenomena, to observe. A review is provided of these phenomena, and of the way in which the present level of understanding has been achieved.

Spreiter, J. R.; Rizzi, A. R.

1974-01-01

393

An Interplanetary Rapid Transit System Between Earth and Mars  

Microsoft Academic Search

A revolutionary interplanetary rapid transit concept for transporting scientists and explorers between Earth and Mars is presented by Global Aerospace Corporation under funding from the NASA Institute for Advanced Concepts (NIAC) with support from the Colorado School of Mines (CSM), Science Applications International Corporation (SAIC), and others. We describe an innovative architecture that uses highly autonomous, solar-powered, xenon ion-propelled spaceships,

Kerry Nock; Michael Duke; Robert King; Mark Jacobs; Lee Johnson; Angus McRonald; Paul Penzo; Jerry Rauwolf; Chris Wyszkowski

2003-01-01

394

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

395

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

396

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

397

Bi-directional streaming of solar wind electrons greater than 80 eV - ISEE evidence for a closed-field structure within the driver gas of an interplanetary shock  

NASA Technical Reports Server (NTRS)

In near time coincidence with the arrival of helium enriched plasma driving the shock wave disturbance of November 12-13, 1978, strong bi-directional streaming of solar wind electrons greater than about 80 eV was observed with Los Alamos instrumentation on ISEE 3. The streaming persisted for many hours simultaneously parallel and anti-parallel to the interplanetary magnetic field which was directed roughly perpendicular to the sun-satellite line. This example of bidirectional streaming cannot be explained by field line connection to the earth's bow shock or the outward propagating interplanetary shock which passed ISEE 3 approximately 16 hours earlier. The event is explained if the local interplanetary field was a part of a magnetic bottle rooted at the sun or a disconnected loop propagating outward.

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

1981-01-01

398

Magnetic Correlation Lengths in the Turbulent Solar Wind  

NASA Astrophysics Data System (ADS)

We analyze the evolution of the interplanetary magnetic field spatial structure by examining the heliospheric autocorrelation functions (R) based on "in situ" observations and using classical single-spacecraft techniques. Correlation lengths (?) derived from R can be viewed as a measured of the integral scale of the turbulence. We focus on how evolves the anisotropy of ? with respect to the aging of fluid parcels traveling away from the Sun, and according to the anisotropy of the measured ?, distinguishing mainly the values parallel (??) or perpendicular (??) to the direction of the local average magnetic field B0. We find that close to the Sun, ?? < ??, supporting a slab-like spectral model, and a progressive isotropization of ? with a trend to reach an inverted relation, while moving towards higher heliodistances, supporting dynamical spectral transfer of energy. We also present preliminary results on the probability distribution functions (PDFs) of ? from an analysis at different heliodistances from the Sun using observations from Helios, ACE and Ulysses. Advances made to better characterize the nature of interplanetary fluctuations, as those presented here, has significant implications in space and astrophysical plasmas, including scattering and transport of charged energetic particles, and theories of MHD turbulence.

Ruiz, M. E.; Dasso, S.; Matthaeus, W. H.; Weygand, J. M.; Marsch, E.

2012-12-01

399

Variability in Martian magnetic field topology  

NASA Astrophysics Data System (ADS)

Martian crustal magnetic fields form localized mini-magnetosphere structures that extend in some regions well above the Martian ionosphere, interacting directly with the draped external interplanetary magnetic field (IMF). In some regions the crustal magnetic field lines are closed, locally shielding the ionosphere from external plasma. In other locations the crustal field lines are open, allowing exchange of plasma between the ionosphere and the surrounding plasma interaction region. The average magnetic topology as a function of geographic location has been mapped previously, using ~7 years of Mars Global Surveyor electron observations recorded at constant altitude and local time. In this previous work, pitch angle distributions of suprathermal electrons were examined for the presence of loss cones to determine whether field lines were open or closed. Here we apply the same technique to describe how magnetic topology varies with four external drivers: solar wind pressure, IMF orientation, solar EUV flux, and Martian season. We see that some locations on Mars change topology frequently depending upon external conditions, while others have a relatively static field topology.

Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.

2013-12-01

400

Magnetic flux pileup and plasma depletion in Mercury's subsolar magnetosheath  

NASA Astrophysics Data System (ADS)

from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft during 40 orbits about Mercury are used to characterize the plasma depletion layer just exterior to the planet's dayside magnetopause. A plasma depletion layer forms at Mercury as a result of piled-up magnetic flux that is draped around the magnetosphere. The low average upstream Alfvénic Mach number (MA ~3-5) in the solar wind at Mercury often results in large-scale plasma depletion in the magnetosheath between the subsolar magnetopause and the bow shock. Flux pileup is observed to occur downstream under both quasi-perpendicular and quasi-parallel shock geometries for all orientations of the interplanetary magnetic field (IMF). Furthermore, little to no plasma depletion is seen during some periods with stable northward IMF. The consistently low value of plasma ?, the ratio of plasma pressure to magnetic pressure, at the magnetopause associated with the low average upstream MA is believed to be the cause for the high average reconnection rate at Mercury, reported to be nearly 3 times that observed at Earth. Finally, a characteristic depletion length outward from the subsolar magnetopause of ~300 km is found for Mercury. This value scales among planetary bodies as the average standoff distance of the magnetopause.

Gershman, Daniel J.; Slavin, James A.; Raines, Jim M.; Zurbuchen, Thomas H.; Anderson, Brian J.; Korth, Haje; Baker, Daniel N.; Solomon, Sean C.

2013-11-01

401

THE IRRADIATION-INDUCED OLIVINE TO AMORPHOUS PYROXENE TRANSFORMATION PRESERVED IN AN INTERPLANETARY DUST PARTICLE  

SciTech Connect

Amorphization of crystalline olivine to glass with a pyroxene composition is well known from high-energy irradiation experiments. This report is on the first natural occurrence of this process preserved in a chondritic aggregate interplanetary dust particle. The Fe-rich olivine grain textures and compositions and the glass grain compositions delineate this transformation that yielded glass with Fe-rich pyroxene compositions. The average glass composition, (Mg, Fe){sub 3}Si{sub 2}O{sub 7}, is a serpentine-dehydroxylate with O/Si = 3.56 +- 0.25, (Mg+Fe)/Si = 1.53 +- 0.24, and Mg/(Mg+Fe) = 0.74 +- 0.1. These measured atomic ratios match the ratios that have been proposed for amorphous interstellar silicate grains very well, albeit the measured Mg/(Mg+Fe) ratio is lower than was proposed for amorphous interstellar silicate grains, Mg/(Mg+Fe) > 0.9.

Rietmeijer, Frans J. M., E-mail: fransjmr@unm.ed [Department of Earth and Planetary Sciences, MSC 03-2040, 1-University of New Mexico, Albuquerque, NM 87131-0001 (United States)

2009-11-01

402

Averaging the spectral shapes  

E-print Network

The methods of obtaining the average spectral shape in a low statistics regime are presented. Different approaches to averaging are extensively tested with simulated spectra, based on the ASCA responses. The issue of binning up the spectrum before fitting is discussed together with the choice of statistic used to model the spectral shape. The best results are obtained with methods in which input data are represented by probability density functions. Application of weights, representing the coverage between the input and output bins, slightly improves the resolution of averaging.

Piotr Lubinski

2004-01-27

403

A temporary earth co-orbital linked to interplanetary field enhancements  

NASA Astrophysics Data System (ADS)

Near-Earth asteroid 138175 (2000 EE104) will soon be temporarily resonant with Earth, but has a much longer residence in an orbit which features a trapping behaviour with frequent Earth and Venus encounters. The object has been identified as a possible source of material for interplanetary field enhancements, a magnetic phenomenon in the solar wind inferred to be due to dust arising from secondary collisions with 10-m scale objects injected into its path. Its horseshoe libration will be reversed by a very close encounter with Venus in 2251 CE. We characterize the orbit of this asteroid, model the dispersion of the primary collision products along its path, and discuss the non-gravitational motion of secondary dust in the solar wind.

Connors, M.; Russell, C. T.; Lai, H. R.

2014-09-01

404

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

405

The Pioneer Jupiter magnetic control program.  

NASA Technical Reports Server (NTRS)

The Pioneer Jupiter spacecraft was required to have a sufficiently small magnetic field that accurate interplanetary-magnetic field measurements would not be compromised. In order to control the magnetic field throughout the program a running account of spacecraft magnetic fields was maintained by means of a periodically updated magnetic model. This model was used to make economic tradeoffs in subsystem magnetic moments within the allowed magnetic budget. The program was culminated with a measurement of the magnetic field of the spacecraft. A description of the magnetic tests and a comparison with estimates made with the magnetic model are also presented.

Sanders, N. L.; Broce, R. D.; Inouye, G. T.

1972-01-01

406

Interplanetary particles and fields, November 22 - December 6, 1977: Helios, Voyager, and IMP observations between 0.6 AU and 1.6 AU  

NASA Technical Reports Server (NTRS)

The principal interplanetary events observed are described and analyzed. Three flow systems were observed: (1) a corotating stream and a stream interface associated with a coronal hole; (2) a shock wave and an energetic particle event associated with a 2-B flare; and (3) an isolated shock wave of uncertain origin. Data from 28 experiments and 6 spacecraft provide measurements of solar wind plasma, magnetic fields, plasma waves, radio waves, energetic electrons, and low energy protons.

Burlaga, L. F.; Lepping, R. P.; Weber, R.; Armstrong, T.; Goodrich, C.; Sullivan, J.; Gurnett, D.; Kellogg, P.; Keppler, E.; Mariani, F.

1979-01-01

407

Global Dayside Ionospheric Uplift and Enhancement Associated with Interplanetary Electric Fields  

NASA Technical Reports Server (NTRS)

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 electric field was initially 33 mV/m just after the forward shock (IMF BZ = -48 nT) and later reached a peak value of 54 mV/m 1 hour and 40 min later (BZ = -78 nT). The electric field was 45 mV/m (BZ = -65 nT) 2 hours after the shock. This electric field generated a magnetic storm of intensity DST = -275 nT. The dayside satellite GPS receiver data plus ground-based GPS data indicate that the entire equatorial and midlatitude (up to +/-50(deg) magnetic latitude (MLAT)) dayside ionosphere was uplifted, significantly increasing the electron content (and densities) at altitudes greater than 430 km (CHAMP orbital altitude). This uplift peaked 2 1/2 hours after the shock passage. The effect of the uplift on the ionospheric total electron content (TEC) lasted for 4 to 5 hours. Our hypothesis is that the interplanetary electric field ''promptly penetrated'' to the ionosphere, and the dayside plasma was convected (by E x B) to higher altitudes. Plasma upward transport/convergence led to a 55-60% increase in equatorial ionospheric TEC to values above 430 km (at 1930 LT). This transport/convergence plus photoionization of atmospheric neutrals at lower altitudes caused a 21% TEC increase in equatorial ionospheric TEC at 1400 LT (from ground-based measurements). During the intense electric field interval, there was a sharp plasma ''shoulder'' detected at midlatitudes by the GPS receiver and altimeter satellites. This shoulder moves equatorward from -54(deg) to -37(deg) MLAT during the development of the main phase of the magnetic storm. We presume this to be an ionospheric signature of the plasmapause and its motion. The total TEC increase of this shoulder is 80%. Part of this increase may be due to a "superfountain effect." The dayside ionospheric TEC above 430 km decreased to values 45% lower than quiet day values 7 to 9 hours after the beginning of the electric field event. The total equatorial ionospheric TEC decrease was 16%. This decrease occurred both at midlatitudes and at the equator. We presume that thermospheric winds and neutral composition changes produced by the storm-time Joule heating, disturbance dynamo electric fields, and electric fields at auroral and subauroral latitudes are responsible for these decreases.

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

2004-01-01

408

Average pattern of auroral particle precipitation, its associated conductivity and field aligned currents. (Reannouncement with new availability information)  

SciTech Connect

A series of statistical studies has been completed to determine the global pattern of auroral electron and ion precipitation and their resultant Hall and Pedersen conductivities as a function of geomagnetic activity, solar wind velocity, the orientation of the Interplanetary Magnetic Field (IMF) and season. In addition, studies were performed relating these global patterns in particle precipitation to similar global determinations of the average delta beta vector produced by the auroral field aligned currents. The data for these studies were from instruments flown on the satellites of the Defense Meteorological Satellite Program (DMSP). In all cases the studies were performed by dividing the high latitude region into a series spatial bins in Magnetic Local Time (MLT) and corrected geomagnetic latitude (CGL). One such matrix of spatial bins was created for each different value or range of values of chosen sort parameter. For geomagnetic activity the sort parameter was one of seven levels of Kp. For the IMF and solar wind velocity the sort parameters consisted of 30 paired ranges of the solar wind velocity and the beta z component of the IMF. A rough separation by the IMF beta was performed by using the IMF sector structure and Kp together as the sort parameter. Seasonal separations were made with Kp and for time periods centered on the summer and winter solstices and the equinoxes. In all cases the large DMSP data sets were used to determine the average spectrum of precipitating electrons and ions and the average delta beta vector for each spatial bin and for each sort parameter used. In this paper the authors review the results of these studies.

Hardy, D.A.; Gussenhoven, M.S.; Rich, F.J.; Brautigam, D.H.

1991-12-31

409

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

410

Interaction of Strong Transient Interplanetary Disturbances with the Dayside Magnetosphere  

NASA Technical Reports Server (NTRS)

The objective of the investigation was to gain an understanding of the complex response of the magnetosphere to strong transient interplanetary disturbances. Because the project was only funded for a year, the investigation focused on only one of the three topics proposed in the original three year proposal. We investigated the response of the dayside auroral region to strong transient interplanetary disturbances. The method of the investigation was to use three-dimensional magnetohydrodynamic (MHD) simulations that employ measurements of the solar wind conditions upstream the bow shock to model actual events and then to compare the simulation results with observations from spacecraft located at downstream locations. We modeled an event that occurred on July 14,2000, for which both CLUSTER and IMAGE simultaneous observations were available. The event was marked by high solar wind dynamic pressure and a strong IMF By component. Comparisons showed a very good agreement between intensifications in the auroral emissions measured by IMAGE

Berchem, Jean

2004-01-01

411

LDEF (Postflight), AO201 : Interplanetary Dust Experiment, Tray H11  

NASA Technical Reports Server (NTRS)

LDEF (Postflight), AO201 : Interplanetary Dust Experiment, Tray H11 The Interplanetary Dust Experiment hardware has a thin brown stain on the exposed surfaces. A deeper brown stain, probably from the material underneath the small electrical cover plate of the detector frame, can be seen in the upper right corner of some of the detectors. Stain that was seen on the solar sensor base plate in the flight photograph cannot be seen because of reflected light. The colors seen in the detector's mirror like surface are reflections of the surrounding area. A dark spot seen on a detector in the third row from the top in the flight photograph, was not found in a postflight inspection. A close inspection of this photograph does reveal several impact damage locations.

1990-01-01

412

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

413

Type 2 radio bursts, interplanetary shocks and energetic particle events  

NASA Technical Reports Server (NTRS)

Using the ISEE-3 radio astronomy experiment data 37 interplanetary (IP) type II bursts have been identified in the period September 1978 to December 1981. These events and the associated phenomena are listed. The events are preceded by intense, soft X ray events with long decay times (LDEs) and type II and/or type IV bursts at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range results in the occurrence of a shock accelerated (SA) event. The majority of the interplanetary type II bursts are associated with energetic particle events. These results support other studies which indicate that energetic solar particles detected at 1 A.U. are generated by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients.

Cane, H. V.; Stone, R. G.

1982-01-01

414

Propagation of inclined interplanetary shock through the magnetosheath  

Microsoft Academic Search

Normals of most interplanetary shocks are nearly aligned with the Sun–Earth line. But some shocks, especially those connected with corotating interaction regions, are sufficiently diverted from the typical orientation near 1AU. We obtain that shocks with normal lying in the XY plane and inclined at an angle about 40°or more from the Sun–Earth line can result in sudden impulse variations

A. A. Samsonov

2011-01-01