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1

Interplanetary Magnetic Field Lines  

NSDL National Science Digital Library

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

Stern, David

2005-04-27

2

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

3

On the Interplanetary Magnetic Storm: Pioneer V  

Microsoft Academic Search

During a period of intense solar activity between March 26 and April 6, 1960, meas- urements of the magnetic fields in interplanetary space were obtained with the space probe, Pioneer V. The measured component of the fields, associated with the solar plasma ejected during this period, attained strengths of 40 or more gammas (compared to an average value of 2.7

P. J. Coleman; C. P. Sonett; Leverett Davis

1961-01-01

4

The interplanetary magnetic field. Solar origin and terrestrial effects  

Microsoft Academic Search

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

John M. Wilcox

1968-01-01

5

Magnetic Storms and Associated Interplanetary Phenomena  

NASA Technical Reports Server (NTRS)

The physical mechanism for energy transfer from the solar wind to the magnetosphere is magnetic reconnection between the interplanetary field and the Earth's field. From Intro: It is the purpose of this paper to review the sources of such interplanetary magnetic fields distinguishing between the solar maximum and the declining phases of the solar cycle.

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

1996-01-01

6

Interplanetary Causes of Great Magnetic Storms: Further Insights  

NASA Technical Reports Server (NTRS)

We discuss possible interplanetary mechanisms for the creation of the great magnetic storms at the Earth. We consider the effects of interplanetary shock events on magneic cloud and sheath plasma, leading to potentially stronger interplanetary magnetic field magnitudes.

Tsurutani, B. T.

1997-01-01

7

Interplanetary stream magnetism - Kinematic effects  

NASA Technical Reports Server (NTRS)

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

Burlaga, L. F.; Barouch, E.

1976-01-01

8

Directional discontinuities in the interplanetary magnetic field  

Microsoft Academic Search

It is shown that the interplanetary magnetic field has different characteristics on different scales, and it is noted that a given physical theory may not be applicable or relevant on all scales. Four scales are defined in terms of time intervals on which the data may be viewed. Many discontinuities in the magnetic-field direction are seen on the mesoscale (˜

Leonard F. Burlaga

1969-01-01

9

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

10

Dynamics of magnetic clouds in interplanetary space  

NASA Technical Reports Server (NTRS)

Magnetic clouds observed in interplanetary space may be regarded as extraneous bodies immersed in the magnetized medium of the solar wind. The interface between a magnetic cloud and its surrounding medium separates the internal and external magnetic fields. Polarization currents are induced in the peripheral layer to make the ambient magnetic field tangential. The motion of a magnetic cloud through the interplanetary medium may be partitioned into a translational motion of the magnetic cloud as a whole and an expansive motion of the volume relative to the axis of the magnetic cloud. The translational motion is determined by two kinds of forces, i.e., the gravitational force exerted by the Sun, and the hydromagnetic buoyancy force exerted by the surrounding medium. On the other hand, the expansive motion is determined by the pressure gradient sustaining the gross difference between the internal and external pressures and by the self-induced magnetic force that results from the interaction among the internal currents. The force resulting from the internal and external currents is a part of the hydromagnetic buoyancy force, manifested by a thermal stress caused by the inhomogeneity of the ambient magnetic pressure.

Yeh, Tyan

1987-01-01

11

Periodicities in the interplanetary magnetic field polarity  

Microsoft Academic Search

The daily data of the polarity of the interplanetary magnetic field for the years 1926-1982 were studied by means of a power spectrum analysis in order to determine prevailing structures of this polarity as well as to search for recurrences in those structures. On a global scale, the presence of significant peaks at about 27.5, 13.5, 9.1 and 6.8 days

A. L. C. Gonzalez; W. D. Gonzalez

1987-01-01

12

Fractal structure of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Under some conditions, time series of the interplanetary magnetic field strength and components have the properties of fractal curves. Magnetic field measurements made near 8.5 AU by Voyager 2 from June 5 to August 24, 1981 were self-similar over time scales from approximately 20 sec to approximately 3 x 100,000 sec, and the fractal dimension of the time series of the strength and components of the magnetic field was D = 5/3, corresponding to a power spectrum P(f) approximately f sup -5/3. Since the Kolmogorov spectrum for homogeneous, isotropic, stationary turbulence is also f sup -5/3, the Voyager 2 measurements are consistent with the observation of an inertial range of turbulence extending over approximately four decades in frequency. Interaction regions probably contributed most of the power in this interval. As an example, one interaction region is discussed in which the magnetic field had a fractal dimension D = 5/3.

Burlaga, L. F.; Klein, L. W.

1985-01-01

13

Substorm and interplanetary magnetic field effects on the geomagnetic tail lobes  

Microsoft Academic Search

The average relationship of the tail lobe magnetic energy density to the north-south component of the interplanetary magnetic field (!MF) and substorm expansion phase is investigated by using a superposed epoch, analysis method. An enhanced average lobe energy density is observed to be associated with a southward component of the IMF prior to substorm breakup. Coincident with the expansion onset,

Michael N. Caan; Robert L. McPherron; Christopher T. Russell

1975-01-01

14

Solar cycle variations in the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

ISEE 3 interplanetary magnetic field measurements have been used to extend the NSSDC hourly averaged IMF composite data set through mid-1982. Most of sunspot cycle 20 (start:1964) and the first half of cycle 21 (start:1976) are now covered. The average magnitude of the field was relatively constant over cycle 20 with approx. 5-10% decreases in 1969 and 1971, when the Sun's polar regions changed polarity, and a 20% decrease in 1975-6 around solar minimum. Since the start of the new cycle, the total field strength has risen with the mean for the first third of 1982 being about 40% greater than the cycle 20 average. As during the previous cycle, an approx. 10% drop in IMF magnitude accompanied the 1980 reversal of the solar magnetic field. While the interplanetary magnetic field is clearly stronger during the present solar cycle, another 5-7 years of observations will be needed to determine if cycle 21 exhibits the same modest variations as the last cycle. Accordingly, it appears at this time that intercycle changes in IMF magnitude may be much larger than the intracycle variations.

Slavin, J. A.; Smith, E. J.

1983-01-01

15

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

16

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

17

Solar origin of long-term variations of the interplanetary magnetic field strength  

Microsoft Academic Search

Spacecraft measurements over the past two sunspot cycles have shown that the average strength of the interplanetary magnetic field (IMF) undergoes surprisingly modest long-term variation, unlike the total magnetic flux observed on the Sun. Our attempt to model the IMF during sunspot cycle 21, based on a current-free extrapolation of the observed photospheric field out to a fixed source surface

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

1988-01-01

18

Latitudinal dependence of the interplanetary magnetic field spectrum  

Microsoft Academic Search

Magnetic field data of Helios 1 in 1975 and Helios 2 in 1976 have been used to investigate the dependence of the interplanetary magnetic field power spectrum upon the angular displacement from the magnetic equator. At low wave numbers the magnetic field convected by the slow solar wind (associated to low latitudes) has spectral signatures different from those of the

R. Bruno; B. Bavassano

1987-01-01

19

Multi-scale Modeling of the Interplanetary Magnetic Field  

Microsoft Academic Search

\\u000a Models for heavy-tailed data with applications to the study of multi-scale behaviour of the interplanetary magnetic field\\u000a are presented. Numerical aspects are given in the case of the data obtained by Ulysses mission (magnetometer VHM\\/FGM). This\\u000a approach yields probabilistic predictions of the dynamics and multiscale behaviour of the interplanetary magnetic field.

N. A. Popescu; E. Popescu

20

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

Microsoft Academic Search

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

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

2010-01-01

21

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

NASA Technical Reports Server (NTRS)

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

Svalgaard, L.; Wilcox, J. M.

1974-01-01

22

The interplanetary magnetic field environment at Mercury's orbit  

Microsoft Academic Search

Mercury is exposed to the most dynamic heliospheric space environment of any planet in the solar system. The magnetosphere is particularly sensitive to variations in the interplanetary magnetic field (IMF), which control the intensity and geometry of the magnetospheric current systems that are the dominant source of uncertainty in determinations of the internal planetary magnetic field structure. The Magnetometer on

Haje Korth; Brian J. Anderson; Thomas H. Zurbuchen; James A. Slavin; Silvia Perri; Scott A. Boardsen; Daniel N. Baker; Sean C. Solomon; Ralph L. McNutt

2010-01-01

23

Multifractal analysis of interplanetary magnetic field obtained during CME events  

NASA Astrophysics Data System (ADS)

In this paper, we have analyzed the interplanetary magnetic field (IMF) obtained by ACE satellite during the coronal mass ejection events. The characterization of the IMF fluctuations was performed using the singular power spectra deviations obtained from a wavelet transform modulus maxima (WTMM) approach. The results suggest the existence of different multifractal processes driving the intermittency during and after the CME events on the IMF time series. The characteristic time scales found, using the WTMM, and possible related physical mechanisms are discussed in the context of nonlinear interplanetary magnetic field response.

Bolzan, M. J. A.; Rosa, R. R.

2012-08-01

24

Interplanetary magnetic fields, their fluctuations, and cosmic ray variations  

NASA Technical Reports Server (NTRS)

The cause of Forbush decreases is examined using neutron monitor data and measurements of the interplanetary magnetic field. It is found that for the period examined (Dec. 15, 1965 to April 23, 1966) large enhancements of the interplanetary magnetic field correlate well with decreases in cosmic ray intensity, while various parameters connected with the fluctuations in the field do not display such good correlation. The inference is drawn that Forbush decreases are not related to the turbulence or random motions in the field but to the large scale features of the field.

Barouch, E.; Sari, J. W.

1975-01-01

25

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

26

Comparison of the mean photospheric magnetic field and the interplanetary magnetic field  

Microsoft Academic Search

The mean photospheric magnetic field of the sun seen as a star has been compared with the interplanetary magnetic field observed with spacecraft near the earth. Each change in polarity of the mean solar field is followed about 4 1\\/2 days later by a change in polarity of the interplanetary field (sector boundary). The scaling of the field magnitude from

A. Severny; J. M. Wilcox; P. H. Scherrer; D. S. Colburn

1970-01-01

27

Search for long term variations of the interplanetary magnetic field  

Microsoft Academic Search

A statistical study is made of the long term variations of the interplanetary magnetic field parameters collected in the years 1964 to 1973 by 12 spacecraft (IMP's, Pioneers and HEOS). Although temporal fluctuations are observed on field components and magnitudes no clear solar cycle variation is found. The same conclusion holds for the statistical distributions and variances of these parameters.

F. Mariani; L. Diodato; G. Moreno

1975-01-01

28

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

29

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

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

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

32

Magnetic reconnection in the interior of interplanetary coronal mass ejections.  

PubMed

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. PMID:25083630

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

2014-07-18

33

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

34

Substorms under northward interplanetary magnetic field: Statistical study  

NASA Astrophysics Data System (ADS)

It is recently noted that substorms can occur even under prolonged north ward interplanetary magnetic field (IMF) conditions. Based on the substorm list obtained from IMAGE spacecraft, we perform a statistical study on the features of substorms during northward IMF interval. The strength of the substorm is represented by the AL index decrease and the total intensity of the auroral bulge. Four main features have been found as follows. (1) Most substorms occur soon after a southward IMF, and intense substorms are more likely to occur for short duration of northward IMF period (2 ˜ 5 h), whereas no intense substorms occur after prolonged northward IMF condition. (2) There is a positive correlation between the strength of the substorm and the two solar wind parameters (the IMF |By| and the solar wind dynamic pressure Pd). (3) The average strength of the substorms during the storm period is much larger than that of the substorms during the period without storm. Meanwhile, nearly all strong storm time substorms occurred either during the intense storm period, or during the late main phase or the early recovery phase of the storm. (4) About half of substorms, either an increase or a decrease in the solar wind dynamic pressure is found within 30 min pre- ceding to each onset time. Such features indicate that the energy stored in the magnetotail during a previous southward IMF period is the main energy source for substorms under northward IMF condition, especially for intense substorms, and both the IMF |By| and the solar wind dynamic pressure play an important role in the energy accumulation during the northward IMF period.

Peng, Z.; Wang, C.; Yang, Y.; Li, H.; Hu, Y.; Du, J.

2013-12-01

35

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

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

Forecasting the Intensity of Magnetic Storms Caused by N-->S Type of Interplanetary Magnetic Clouds  

Microsoft Academic Search

A scheme developed to forecast in near real time the value of minimum Dst, and its time of occurrence, during a magnetic storm caused by the passage of a N-->S type of magnetic cloud (MC) is described. [N-->S refers to the Bz component of the interplanetary magnetic field within a MC going from north (+) to south (-) in GSE

R. P. Lepping; C. Wu; D. B. Berdichevsky; T. Narock

2005-01-01

38

Power spectra of the interplanetary magnetic field near the earth  

NASA Technical Reports Server (NTRS)

Power spectra of the interplanetary magnetic field measured by near-earth satellites upstream from the earth's bow shock are free from terrestrial contamination provided the field at the satellite does not intersect the bow shock. Considerable spectral enhancement for the range of frequencies 0.01 to 1.00 Hz, due to turbulence caused by the shock, may occur if the field observed at the satellite intersects the shock. This turbulence occurs frequently in both the morning and afternoon quadrants. In the frequency band from 0.07 to 1 Hz, this noise decreases in amplitude with radial distance from the shock with an attenuation length of 4 R sub E.

Childers, D. D.; Russell, C. T.

1972-01-01

39

Ground state alignment as a tracer of interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

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

Yan, H.

2012-12-01

40

The Spectrum of Fluctuations of the Interplanetary Magnetic Field during an 11Year Solar Activity Cycle  

Microsoft Academic Search

In this work, 5-min data on magnitudes of the interplanetary magnetic field, measured by the IMP 8 spacecraft between 1980 and 1991, are used. Time variations in the power spectra of interplanetary-magnetic- field fluctuations in the frequency range from 104 to 1.67 × 103 Hz during the solar activity cycle are studied, taking into account the sunspot numbers RZ and

S. A. Starodubtsev

2000-01-01

41

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

42

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

43

Interplanetary magnetic field variations and the electromagnetic state of the equatorial ionosphere  

NASA Technical Reports Server (NTRS)

The Esq phenomena were selected in order to examine the effect of the interplanetary magnetic field (IMF) on the ionospheric plasma and to obtain insight into the interplanetary ionospheric coupling processes. January-March 1973 interplanetary magnetic field data of Explorer 43, Huancayo ionograms, and surface equatorial magnetograms were used. The IMF observations from Explorer 43 in the form of 15-sec averages were examined around the time of disappearance of the Esq. The IMF z-component was observed to change from a negative to a positive value before the disappearance of the Esq in four events where simultaneous data were available. The general explanation is that the induced electric field becomes westward from a previous eastward direction, coinciding with the IMF z-component reversal. Thus, just before the Esq disappears, the magnetosphere is subjected to the westward electric field. If this field is impressed to the low-latitude ionosphere, the resultant electric field in the equatorial ionosphere changes from eastward (westward) to westward (eastward) in the daytime (nighttime).

Patel, V. L.

1978-01-01

44

Polar cap magnetic variations and their relationship with the interplanetary magnetic sector structure  

Microsoft Academic Search

The relationship between polar geomagnetic variations and the polarity of the interplanetary magnetic sectors' has been studied for the quiet year 1965. It is found that during the day hours a system of ionospheric currents encircles the magnetic poles on every day. The current system may extend up to 15 ø from the pole but is strongest at 8ø-10 ø

Leif Svalgaard

1973-01-01

45

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

46

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

Microsoft Academic Search

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

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

1985-01-01

47

Dependence of pitch angle scattering of cosmic rays on slope of power spectra of magnetic field fluctuations in interplanetary space  

Microsoft Academic Search

A numerical study is presented of the dependence of cosmic ray pitch-angle scattering coefficients on the power spectrum of interplanetary magnetic field fluctuations and particle rigidity. Monte-Carlo pitch angle scattering calculations are performed for random magnetic fields with power law indexes of 1.7, 2.0 and 2.3 governing fluctuations in the average field direction in a slab model. Results show the

M. Kato; T. Sakai; E. Tamai

1981-01-01

48

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

Microsoft Academic Search

Simultaneous ISEE-3 field and plasma data were used to examine interplanetary phenomena associated with 10 major magnetic storms detected from August 16, 1978, to December 28, 1979, in a study of Gonzalez and Tsurutani (1987), and, in particular to determine the origins of the southward magnetic fields which caused the storms. In nine of the 10 cases, the responsible interplanetary

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

1988-01-01

49

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

50

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

51

Observations of an interplanetary slow shock associated with magnetic cloud boundary layer  

Microsoft Academic Search

(1) The observations of the slow shocks associated with the interplanetary coronal mass ejections near 1 AU have seldom been reported in the past several decades. In this paper we report the identification of an interplanetary slow shock observed by Wind on September 18, 1997. This slow shock is found to be just the front boundary of a magnetic cloud

P. B. Zuo; F. S. Wei; X. S. Feng

2006-01-01

52

Observations of an interplanetary slow shock associated with magnetic cloud boundary layer  

Microsoft Academic Search

The observations of the slow shocks associated with the interplanetary coronal mass ejections near 1 AU have seldom been reported in the past several decades. In this paper we report the identification of an interplanetary slow shock observed by Wind on September 18, 1997. This slow shock is found to be just the front boundary of a magnetic cloud boundary

P. B. Zuo; F. S. Wei; X. S. Feng

2006-01-01

53

Advanced Propulsion for Interplanetary Flights using Magnetized Target Fusion  

NASA Astrophysics Data System (ADS)

Magnetized target fusion is an approach in which a magnetized target plasma is compressed inertially by an imploding material wall. The use of a high energy plasma liner to provide the required implosion was recently proposed by Thio, et al. The plasma liner is formed by the merging of a number (nominally 60) of high momentum plasma jets converging towards the center of a sphere where two compact toroids have been introduced. Preliminary 3-D hydrodynamics modeling results using the SPHINX code of LANL have been very encouraging and confirm earlier theoretical expectations. The concept appears ready for experimental exploration, and plans for doing so are being pursued. In this talk, we explore conceptually how this innovative fusion approach could be packaged for space propulsion for interplanetary travel. We discuss the critical componenets of a baseline propulsion concept including the fusion engine, high velocity plasma accelerators, generators of compact toroids using conical theta pinches, magnetic nozzle, neutron absorption blanket, tritium reprocessing system, shock absorber, MHD generator, capacitor pulsed power system, thermal management system, and micrometeorite shields.

Thio, Y. C. F.; Freeze, B.; Gerrish, H.; Kirkpatrick, R. C.; Landrum, D. B.; Schmidt, G. R.

1998-11-01

54

Recovery phase of magnetic storms induced by different interplanetary drivers  

E-print Network

Statistical analysis of Dst behaviour during recovery phase of magnetic storms induced by different types of interplanetary drivers is made on the basis of OMNI data in period 1976-2000. We study storms induced by ICMEs (including magnetic clouds (MC) and Ejecta) and both types of compressed regions: corotating interaction regions (CIR) and Sheaths. The shortest, moderate and longest durations of recovery phase are observed in ICME-, CIR-, and Sheath-induced storms, respectively. Recovery phases of strong ($Dst_{min} magnetic storms are well approximated by hyperbolic functions $Dst(t)= a/(1+t/\\tau_h)$ with constant $\\tau_h$ times for all types of drivers while for moderate ($-100 storms $Dst$ profile can not be approximated by hyperbolic function with constant $\\tau_h$ because hyperbolic time $\\tau_h$ increases with increasing time of recovery phase. Relation between duration and value $Dst_{min}$ for storms induced by ICME and Sheath has 2 parts: $Dst_{min}$ and d...

Yermolaev, Yu I; Nikolaeva, N S; Yermolaev, M Yu

2011-01-01

55

Magnetic field directional discontinuities. I - Minimum variance errors. [of interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The paper deals with a statistical analysis of the errors associated with a minimum variance analysis of directional discontinuities by use of an idealized model of these discontinuities and various simulations, and also by an examination of actual Mariner 10 interplanetary magnetic field data. An empirical expression is derived for the magnitude of the error in an estimated discontinuity normal component, relative to the total field across the directional discontinuity. The analysis was performed primarily to aid in differentiating between interplanetary tangential and rotational discontinuities observed by Mariner 10.

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

1980-01-01

56

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

57

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

58

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

59

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

NASA Astrophysics Data System (ADS)

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

Khabarova, O.

2013-12-01

60

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

61

Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere  

NASA Astrophysics Data System (ADS)

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

Khabarova, Olga; Obridko, Vladimir

2012-12-01

62

Magnetospheric convection induced by the positive and negative Z components of the interplanetary magnetic field - Quantitative analysis using polar cap magnetic records  

Microsoft Academic Search

The dependence of the polar cap magnetic disturbance on the polarity and magnitude of the Z component of the interplanetary magnetic field is investigated by regression analysis using hourly values. The Svalgaard-Mansurov effect has been eliminated by assuming a linear dependence on the Y component of the interplanetary field. It is shown that as the northward component of the interplanetary

Kiyoshi Maezawa

1976-01-01

63

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

64

UPSTREAM SHOCKS AND INTERPLANETARY MAGNETIC CLOUD SPEED AND EXPANSION: SUN, WIND, AND EARTH  

E-print Network

UPSTREAM SHOCKS AND INTERPLANETARY MAGNETIC CLOUD SPEED AND EXPANSION: SUN, WIND, AND EARTH, of the magnetic clouds observed by WIND near Earth over the span of about 4 years (1995-1998), i.e., mainly during of transit times from the Sun to Earth for a set of 20 magnetic clouds with the result that acceleration

Richardson, John

65

Solar sources of interplanetary southward Bz events responsible for major magnetic storms (1978-1979)  

NASA Technical Reports Server (NTRS)

The solar sources of interplanetary southward Bz events responsible for major magnetic storms observed in the August 1978-December 1979 period were studied using a full complement of solar wind plasma and field data from ISEE 3. It was found that, of the ten major storms observed, seven were initiated by active region flares, and three were associated with prominence eruptions in solar quiet regions. Nine of the storms were associated with interplanetary shocks. However, a comparison of the solar events' characteristics and those of the resulting interplanetary shocks indicated that standard solar parameters did not correlate with the strengths of the resulting shocks at 1 AU.

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

1989-01-01

66

Coronal holes, solar diurnal anisotropy of cosmic rays and off-ecliptic interplanetary magnetic fields  

NASA Technical Reports Server (NTRS)

The information regarding the electromagnetic states of the interplanetary medium, derived from the analyses of the cosmic ray intensity variations observed with a global network of cosmic ray detectors such as neutron monitors and muon telescopes, is reviewed. The relation of the temporal characteristics of the cosmic ray solar diurnal anisotropy to the large scale characteristics of the interplanetary magnetic field, far away from the ecliptic plane, is addressed. A model for the phenomenon is described.

Ahluwalia, H. S.

1980-01-01

67

Characteristics of ion velocity structure at high latitudes during steady southward interplanetary magnetic field conditions  

NASA Astrophysics Data System (ADS)

Variability or structure in the ion velocity at high latitudes in the F region is an important consideration when calculating an accurate Joule heating rate. Velocity structure in time and space may contribute significantly to heating of the F region and its inclusion could help improve our understanding of the energy budget of the atmosphere. In this paper we neglect temporal changes over periods less than 16 s and discuss the characteristic spatial structure in the ion drift in the F region ionosphere and how it relates to the bulk ion flow, the gradient on the bulk ion flow, and the ion temperature in the polar cap and auroral zone. This investigation uses data from the Dynamics Explorer 2 satellite and is limited to times of stable southward interplanetary magnetic field. Under these conditions time averaged enhancements in the Joule heating rate from the presence of spatial structure in the auroral zones have minimum values ranging from 4% to 13% depending on season.

Johnson, E. S.; Heelis, R. A.

2005-12-01

68

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

69

Relationships of the Solar Wind Parameters with the Magnetic Storm Magnitude and their Association with the Interplanetary Shock  

Microsoft Academic Search

It is investigated quantitative relations between the magnetic storm magnitude and the solar wind parameters such as the Interplanetary Magnetic Field (hereinafter, IMF) magnitude (B), the southward component of IMF (Bz), and the dynamic pressure during the main phase of the magnetic storm with focus on the role of the interplanetary shock (hereinafter, IPS) in order to build the space

Su Yeon Oh; Yu Yi

2004-01-01

70

nUMERICAL Study of Magnetic Reconnection Process Near Interplanetary Current Sheet  

NASA Astrophysics Data System (ADS)

The third order accurate upwind compact difference scheme has been applied to the numerical study of the magnetic reconnection process possibly occurring near the interplanetary current sheet, under the framework of the two-dimensional compressible magnetohydrodynamics (MHD). Our results here show that the driven reconnection near the current sheet can occur within 10-30 min for the interplanetary high magnetic Reynolds number, RM=2 000--10 000, a stable magnetic reconnection structure can be formed in hour-order of magnitude, and there are some basic properties such as the multiple X-line reconnections, vortex velocity structures, fila ment current systems, splitting and collapse of the high-density plasma bulk. These results are helpful in understanding and identifying the magnetic reconnection phenomena near the interplanetary current sheets.

Wei, F.; Hu, Q.; Feng, X.

71

Observational constraints on the dynamics of the interplanetary magnetic field dissipation range  

Microsoft Academic Search

The dissipation range for interplanetary magnetic field fluctuations is formed by those fluctuations with spatial scales comparable to the gyroradius or ion inertial length of a thermal ion. It is reasonable to assume that the dissipation range represents the final fate of magnetic energy that is transferred from the largest spatial scales via nonlinear processes until kinetic coupling with the

Robert J. Leamon; Charles W. Smith; Norman F. Ness; William H. Matthaeus; Hung K. Wong

1998-01-01

72

A method simulating random magnetic field in interplanetary space by an autoregressive method  

Microsoft Academic Search

The generation of random magnetic fields is important in connection with the problem to obtain the scattering coefficients of cosmic rays in interplanetary space. The present study is concerned with the development of a method for generating random magnetic fields corresponding to a power spectrum having an arbitrary spectral index gamma, taking into account the utilization of the autoregressive process.

M. Kato; T. Sakai

1985-01-01

73

Observations of reconnection of interplanetary and lobe magnetic field lines at the high-latitude magnetopause  

Microsoft Academic Search

Measurements made with the Fast Plasma Experiment on ISEE 2 in the vicinity of the high-latitude, dusk magnetopause near the terminator plane, at a time when the local magnetosheath and tail lobe magnetic fields were nearly oppositely directed, provide direct evidence for the reconnection of the open field lines of the tail lobes with the interplanetary magnetic field (IMF). The

J. T. Gosling; M. F. Thomsen; S. J. Bame; R. C. Elphic; C.T. Russell

1991-01-01

74

Quantitative model for the potential resulting from reconnection with an arbitrary interplanetary magnetic field  

Microsoft Academic Search

Considerable evidence has accumulated to suggest that many features of magnetospheric dynamics are controlled by the interaction between the interplanetary and terrestrial magnetic fields. Dungey [1961] suggested that the mechanism responsible for this interaction is magnetic field reconnection taking place at the magnetopause, where the two fields meet. The general properties of this interaction are a change in the topology

W. D. Gonzalez; F. S. Mozer

1974-01-01

75

Dependence of the high-latitude thermospheric densities on the interplanetary magnetic field  

Microsoft Academic Search

The systematic analysis of the interplanetary magnetic field (IMF) B y and B z influences on observed thermospheric density is presented. For this purpose, the high-latitude southern summer thermospheric total mass density near 400 km altitude, derived from the high-accuracy accelerometer on board the Challenging Minisatellite Payload (CHAMP) spacecraft, is statistically analyzed in magnetic coordinates. The difference density distributions, which

Y.-S. Kwak; A. D. Richmond; Y. Deng; J. M. Forbes; K.-H. Kim

2009-01-01

76

Dependence of the high-latitude thermospheric densities on the interplanetary magnetic field  

Microsoft Academic Search

The systematic analysis of the interplanetary magnetic field (IMF) By and Bz influences on observed thermospheric density is presented. For this purpose, the high-latitude southern summer thermospheric total mass density near 400 km altitude, derived from the high-accuracy accelerometer on board the Challenging Minisatellite Payload (CHAMP) spacecraft, is statistically analyzed in magnetic coordinates. The difference density distributions, which are obtained

Y.-S. Kwak; A. D. Richmond; Y. Deng; J. M. Forbes; K.-H. Kim

2009-01-01

77

Plasma and magnetic field structure of a slow shock: Wind observations in interplanetary space  

Microsoft Academic Search

This paper reports on the observation of an interplanetary slow shock on May 23, 1995 using 3-s plasma and magnetic field data from the Wind spacecraft. Since the time to traverse the shock (?15 s) is much greater than the 3-s temporal resolution of the data, this observation can reveal the plasma and magnetic field structure through the interior of

Y. C. Whang; D. Larson; R. P. Lin; R. P. Lepping; A. Szabo

1998-01-01

78

Plasma and magnetic field structure of a slow shock: Wind observations in interplanetary space  

Microsoft Academic Search

This paper reports on the observation of an interplanetary slow shock on May 23, 1995 using 3-s plasma and magnetic field data from the Wind spacecraft. Since the time to traverse the shock (~15 s) is much greater than the 3-s temporal resolution of the data, this observation can reveal the plasma and magnetic field structure through the interior of

Y. C. Whang; D. Larson; R. P. Lin; R. P. Lepping; A. Szabo

1998-01-01

79

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

80

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

81

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

82

Characteristics of the association between the interplanetary magnetic field and substorms  

Microsoft Academic Search

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 B\\/sub z\\/(GSM) component had been northward for more than 2 hours. It was found that when the IMF thus shifted southward and remained southward for at

Michael N. Caan; Robert L. McPherron; Christopher T. Russell

1977-01-01

83

Sudden impulses at low latitude stations: Steady state response for southward interplanetary magnetic field  

Microsoft Academic Search

When the interplanetary field is northward and the solar wind dynamic pressure suddenly increases, the increase in the H component magnetic field on the surface of the Earth at low and mid-latitudes is governed principally by the currents on the magnetopause. Currents in the tail, which act in the opposite sense to the magnetopause currents, are also enhanced. These currents

C.T. Russell; M. Ginskey; S. M. Petrinec

1994-01-01

84

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

Microsoft Academic Search

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

J. P. Heppner

1972-01-01

85

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

86

Manifestation of the Jupiter's synodic period in the solar wind, interplanetary magnetic field and geophysical parameters  

Microsoft Academic Search

Studying by the authors of paper of solar wind parameters, namely: density, speed and temperature and also a module of interplanetary magnetic field (IMF) intensity has allowed to find out in them fluctuations with the period of 399 days. From references it is known that this period coincidence with the synodic period of Jupiter. So long as close by the

S. N. Samsonov; N. G. Skryabin

2010-01-01

87

Effect of the Interplanetary Magnetic Field on the Thermospheric Density at High Latitude  

Microsoft Academic Search

The high-latitude thermospheric total mass density near 400 km altitude, derived from the high-accuracy accelerometer on board the Challenging Minisatellite Payload (CHAMP) spacecraft in November 2001 through February 2002, is statistically analyzed as a function of the direction and strength of the interplanetary magnetic field (IMF) for southern hemisphere. The difference densities, which are obtained by subtracting values for zero

Y. Kwak; A. D. Richmond; Y. Deng; J. M. Forbes; K. Kim; K. Cho

2007-01-01

88

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.

89

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

NASA Technical Reports Server (NTRS)

Simultaneous ISEE-3 field and plasma data were used to examine interplanetary phenomena associated with 10 major magnetic storms detected from August 16, 1978, to December 28, 1979, in a study of Gonzalez and Tsurutani (1987), and, in particular to determine the origins of the southward magnetic fields which caused the storms. In nine of the 10 cases, the responsible interplanetary events were found, as expected, to be associated with the high magnetic fields in the stream-stream interaction regions (sheaths) or driver gases, with the events following the interplanetary shocks. The tenth event was found to be associated not with a high-speed stream, but with a noncompressional density-enhancement event. The results of this study indicate the equal importance of both the sheath fields or draped fields and the driver gas fields for the generation of major geomagnetic storms.

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

1988-01-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

91

Power spectra of the interplanetary magnetic field, 0.7-1.6 AU  

NASA Technical Reports Server (NTRS)

Power spectra of the fluctuations in the interplanetary magnetic field have been obtained from a number of spacecraft. Russell (1972) and Childers and Russell (1972) have recently reviewed published power spectra of the interplanetary field. In the present paper the computation of power spectra in the frequency range from .0000116 to .0000296 Hz, corresponding to periods from 1 day to 5.86 min, is described. The data used for these spectra were taken during the Mariner 4 and Mariner 5 missions and cover a radial distance from 0.7 to 1.6 AU.

Blake, D. H.; Belcher, J. W.

1974-01-01

92

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

93

Comments on the measurement of power spectra of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Examination of possible noise sources in the measurement of the power spectrum of fluctuations in the interplanetary magnetic field shows that most measurements by fluxgate magnetometers are limited by digitization noise whereas the search coil magnetometer is limited by instrument noise. The folding of power about the Nyquist frequency or aliasing can be a serious problem at times for many magnetometers, but it is not serious during typical solar wind conditions except near the Nyquist frequency. Waves in the solar wind associated with the presence of the earth's bow shock can contaminate the interplanetary spectrum in the vicinity of the earth. However, at times the spectrum in this region is the same as far from the earth. Doppler shifting caused by the convection of waves by the solar wind makes the interpretation of interplanetary spectra difficult.

Russell, C. T.

1972-01-01

94

Polar cap currents for different directions of the interplanetary magnetic field in the Y-Z plane  

Microsoft Academic Search

During intervals of a steady state condition of the interplanetary ; magnetic field the geomagnetic variations at the polar cap have been examined as ; a function of the direction of the interplanetary field in the Y-Z plane of the ; geocentric solar magnetospheric coordinate system. A prominent feature of the ; equivalent current patterns during a positive B\\/sub z\\/

E. Friis-Christensen; J. Wilhjelm

1975-01-01

95

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

E-print Network

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

California at Berkeley, University of

96

Long-term variations of interplanetary magnetic field spectra with implications for cosmic ray modulation  

NASA Technical Reports Server (NTRS)

The paper calculates yearly averaged power spectra of interplanetary magnetic field turbulence at 1 AU over the period 1965-1988 for fluctuations in the frequency range 5.8 x 10 exp -6 to 4.6 x 10 exp -5 Hz, corresponding to periods of 6-48 hr. The amplitudes of the spectra vary with the sunspot cycle and are inversely correlated with the intensity of about 10-GeV cosmic rays. The observed spectra are used to calculate a lower limit to the cosmic ray scattering mean free path employing resonant magnetostatic quasi-linear theory for both 'slab' and isotropic geometries of the turbulence. The mean free paths thus obtained are typically about 0.1 AU in the slab model and about 0.3 AU in the isotropic model, but they are not significantly correlated with the modulated galactic cosmic ray intensity recorded by neutron monitors. It is inferred that the scattering processes described by resonant magnetostatic theory play, at best, a very minor role in the solar modulation of about 10-GeV cosmic rays.

Bieber, John W.; Chen, Jiasheng; Matthaeus, William H.; Smith, Charles W.; Pomerantz, Martin A.

1993-01-01

97

Magnetic pulsations as a probe of the interplanetary magnetic field: a test of the Borok B Index  

Microsoft Academic Search

A magnetic pulsation index based on the periods of Pc 2--4 pulsations as recorded in earth current measurements at the Borok Geophysical Observatory has been claimed to be a measure of the interplanetary field. Tests of this index for the period 1972 to June 1974 show only a 27% success rate. However, a simple recalibration of the index improves the

Christopher T. Russell; Barbara K. Fleming

1976-01-01

98

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

99

Influence of the interplanetary driver type on the durations of the main and recovery phases of magnetic storms  

NASA Astrophysics Data System (ADS)

We study the durations of the main and recovery phases of magnetic storms induced by different types of large-scale solar-wind streams (Sheath, magnetic cloud (MC), Ejecta, and corotating interaction region (CIR)) on the basis of OMNI data for 1976-2000. The durations of both the main and recovery phases depend on the type of interplanetary drivers. On average, the duration of the main phase of storms induced by compressed regions (CIR and Sheath) is shorter than for MC and Ejecta, while the duration of the recovery phase of CIR- and Sheath-induced storms is longer. Analysis of the durations of individual storms shows that the durations of the main and recovery phases anticorrelate for CIR- and Sheath-induced storms and there is no dependence between them for (MC + Ejecta)-induced storms.

Yermolaev, Yu. I.; Lodkina, I. G.; Nikolaeva, N. S.; Yermolaev, M. Yu.

2014-10-01

100

Influence of the interplanetary driver type on the durations of main and recovery phases of magnetic storms  

E-print Network

We study durations of main and recovery phases of magnetic storms induced by different types of large-scale solar-wind streams (Sheath, magnetic cloud (MC), Ejecta and CIR) on the basis of OMNI data base during 1976-2000. Durations of both main and recovery phases depend on types of interplanetary drivers. On the average, duration of main phase of storms induced by compressed regions (CIR and Sheath) is shorter than by MC and Ejecta while duration of recovery phase of CIR- and Sheath-induced storms is longer. Analysis of durations of individual storms shows that durations of main and recovery phases anti-correlate for CIR- and Sheath-induced storms and there is not dependence between them for (MC+Ejecta)-induced storms.

Yermolaev, Yu I; Nikolaeva, N S; Yermolaev, M Yu

2013-01-01

101

On the use of a sunward libration-point-orbiting spacecraft as an interplanetary magnetic field monitor for magnetospheric studies  

NASA Technical Reports Server (NTRS)

In order to test the accuracy of using magnetometer data from a spacecraft orbiting the sunward libration point to determine the orientation of the interplanetary magnetic field (IMF), the angle between the IMF at ISEE 3, when it was positioned around the libration point, and at ISEE 1, orbiting the earth, has been calculated for a data set of 1-hour periods covering four months. For each period, a 10-minute average of ISEE 1 data is compared with 10-minute averages of ISEE 3 data at successively lagged intervals. It is concluded that the IMF orientation at a libration-point-orbiting spacecraft, lagged by the time required for the solar wind to convect to the earth, is a convenient predictor of IMF orientation near the earth, to within about 20-degree accuracy.

Kelly, T. J.; Crooker, N. U.; Siscoe, G. L.; Russell, C. T.; Smith, E. J.

1986-01-01

102

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

NSDL National Science Digital Library

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

Stern, David

103

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

SciTech Connect

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 near-equatorial D/sub s//sub t/ index, are used in this analysis. It is found that the origins of the interplanetary southward B/sub z/ events are quite varied. If it is defined that the B/sub z/ event which leads to D/sub s//sub t/<-100 nT is ''the cause'' of the storm, then one of the storm intensifications is caused by shock compression of preexisting southward interplanetary magnetic fields, four (or five) are related to driver gas magnetic fields, one (or two) are caused by shocked kinky heliospheric current sheets, two (or three) by turbulence or waves behind interplanetary shocks, and one possibly by draped fields associated with a noncompressive density enhancement event (without a shock or a high-speed stream).

Tsurutani, B.T.; Gonzalez, W.D.; Tang, F.; Akasofu, S.I.; Smith, E.J.

1988-08-01

104

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

Microsoft Academic Search

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

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

1994-01-01

105

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

Microsoft Academic Search

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

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

1994-01-01

106

Correlation of the 27-day variation of cosmic rays to the interplanetary magnetic field strength  

Microsoft Academic Search

We analyze cosmic ray data as well as interplanetary magnetic field (IMF) data, to examine the relation and correlation between their 27-day variations during the time interval 1965-1995. The amplitude of the 27day variation of galactic cosmic rays is linearly correlated with: the IMF strength (B), the z-component (Bz) of the IMF vector and the product of the solar wind

I. Sabbah

2001-01-01

107

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

NASA Technical Reports Server (NTRS)

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

Ng, C. K.

1988-01-01

108

Dependence of Magnetic Storm Intensity on Interplanetary Electric Field Variability  

Microsoft Academic Search

Recent studies have shown that magnetic storms are relatively weak when the solar wind dawn-dusk electric field (Ey) is smooth and accordingly there is a lack of substorm expansion phases over intervals as long as several hours during ring current intensification. This suggests that magnetic storm intensity is controlled not only by the strength, but also by the variability of

X. Zhou; G. Rostoker; W. Sun

2006-01-01

109

SEPs Dropout Events Associated with Advected Interplanetary Magnetic Structures  

NASA Astrophysics Data System (ADS)

The intensity profile of energetic particles from impulsive solar flares (SEP) often shows abrupt dropouts affecting all energies simultaneously, without time-dispersion. Part of the community thinks that these modulations are directly related to the presence of magnetic structures with a different magnetic topology advected by the wind, a sort of magnetic flux tubes. During the expansion, following the dynamical interaction between plasma regions travelling at different speed, these structures would be partially tangled up in a sort of spaghetti-like bundle. These flux tubes would be alternatively connected or not connected with the flare site and, consequently, they would be filled or devoid of SEPs. When the observer passes through them, he would observe clear particles dropout signatures. We will report about results from a detailed analysis of SEP events which showed several signatures in the local magnetic field and/or plasma parameters associated with SEP modulations. These findings corroborate the idea of a possible link between these particles events observed at the Earth's orbit and magnetic connection or disconnection of the ambient magnetic field with the flare region at the Sun. We will also discuss the advantages represented by future Solar Orbiter in-situ observations. As a matter of fact, Solar Orbiter, from its orbital vantage point during the quasi corotation phase, will be a priviledged observer of this kind of phenomenon since it will observe the advected structure of the solar wind not yet reprocessed by dynamical interaction due to wind expansion.

Bruno, R.; Trenchi, L.; Telloni, D.; D'Amicis, R.; Marcucci, F.; Zurbuchen, T.; Weberg, M. J.

2013-05-01

110

Magnetic Field-line Twist in Interplanetary Flux Ropes and its Implications for Their Solar Sources  

NASA Astrophysics Data System (ADS)

Interplanetary flux ropes, embedded within interplanetary coronal mass ejections (ICMEs), are often detected in-situ by spacecraft ACE, Wind, and STEREO. Both magnetic field and plasma measurements sampled along the spacecraft path across the ICME structure are available for quantitative analysis. We apply the Grad-Shafranov reconstruction technique to examine the configuration of the flux ropes and to derive relevant physical quantities, such as magnetic flux content, relative magnetic helicity, and the field-line twist. We select recent events during the rising phase of enhanced solar activity, and utilize additional imaging observations from STEREO and SDO spacecraft. Both detailed analyses of solar source region characteristics including flaring and magnetic reconnection sequence, and the corresponding flux rope structures will be presented. In particular, we examine the distribution of magnetic field-line twist in flux ropes on nested cylindrical iso-surfaces of the magnetic flux function. We compare the in-situ characterization of these flux-rope structures with their corresponding solar source region properties. We discuss the implications of such comparison for the origination of flux ropes on the Sun.

Hu, Q.; Qiu, J.

2013-12-01

111

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

112

Auroral boundary variations and the interplanetary magnetic field  

Microsoft Academic Search

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

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

1984-01-01

113

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

NASA Technical Reports Server (NTRS)

An analysis of ISEE-3 field and plasma data shows that 10 intense magnetic storms that occurred in 1979 were caused by long-duration, large-amplitude (13-30 nT) and negative (less than -10 nT) IMF Bz events associated with interplanetary duskward-electric fields of greater than 5 mV/m. The results suggest that these criteria may be used as predictors of intense storms. A study of opposite polarity (northward) Bz events with the same criteria shows that their occurrence is similar both in number and in their relationship to interplanetary disturbances. The amplitudes of the storms were not found to vary with shock strengths.

Gonzalez, Walter D.; Tsurutani, Bruce T.

1987-01-01

114

Comparison of isee-1 and -3 interplanetary magnetic field observations  

Microsoft Academic Search

Three hourly correlation coefficients and the lag at maximum correlation are computed using one minute averages of ISEE-1 and -3 magnetometer data during the period in which ISEE-3 moved from the earth to its halo orbit around the libration point. The maximum correlation coefficients are highly variable ranging from close to zero to almost unity. The lags, while on the

C.T. Russell; G. L. Siscoe; E. J. Smith

1980-01-01

115

EFFECT OF FINITE LARMOR RADIUS ON COSMIC-RAY PENETRATION INTO AN INTERPLANETARY MAGNETIC FLUX ROPE  

SciTech Connect

We discuss a mechanism for cosmic-ray penetration into an interplanetary magnetic flux rope, particularly the effect of the finite Larmor radius and magnetic field irregularities. First, we derive analytical solutions for cosmic-ray behavior inside a magnetic flux rope, on the basis of the Newton-Lorentz equation of a particle, to investigate how cosmic rays penetrate magnetic flux ropes under an assumption of there being no scattering by small-scale magnetic field irregularities. The results show that the behavior of a particle is determined by only one parameter f{sub 0}, that is, the ratio of the Larmor radius at the flux rope axis to the flux rope radius. The analytical solutions show that cosmic rays cannot penetrate into the inner region of a flux rope by only gyration and gradient-curvature drift in the case of small f{sub 0}. Next, we perform a numerical simulation of a cosmic-ray penetration into an interplanetary magnetic flux rope by adding small-scale magnetic field irregularities. The results show that cosmic rays can penetrate into a magnetic flux rope even in the case of small f{sub 0} because of the effect of small-scale magnetic field irregularities. This simulation also shows that a cosmic-ray density distribution is greatly different from that deduced from a guiding center approximation because of the effect of the finite Larmor radius and magnetic field irregularities for the case of a moderate to large Larmor radius compared to the flux rope radius.

Kubo, Yuki [Space Environment Group, National Institute of Information and Communications Technology, Tokyo 184-8795 (Japan); Shimazu, Hironori, E-mail: kubo@nict.go.j [Department of Information System Fundamentals, University of Electro-Communications, Tokyo 182-8585 (Japan)

2010-09-01

116

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

117

Equatorial distributions of the plasma sheet ions, their electric and magnetic drifts, and magnetic fields under different interplanetary magnetic field Bz conditions  

Microsoft Academic Search

To understand the nightside plasma sheet structure under different interplanetary magnetic field (IMF) Bz conditions, we have investigated statistically the equatorial distributions of ions and magnetic fields from Geotail when the IMF has been continuously northward or southward for shorter or longer than 1 hour. A dawn-dusk density (temperature) asymmetry with higher density (temperature) on the dawn (dusk) side is

Chih-Ping Wang; Larry R. Lyons; James M. Weygand; Tsugunobu Nagai; Richard W. McEntire

2006-01-01

118

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

119

Auroral boundary variations and the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

A DMSP satellite data set of 150 auroral images, obtained during magnetically quiet times, has been analyzed in corrected geomagnetic local time and latitudinal coordinates, and fit to offset circles whose parameters can be compared to the hourly IMF prior to the time of the satellite scans of the aurora. The results for variation of circle radius with the north-south component of the IMF B(z) agree with previously published results, and generally show a 1 deg radius increase when the B(z) component increases southward by 1 nT. The location of the circle center also has a clear statistical shift in the Southern Hemisphere with IMF B(y), such that the southern polar cap moves toward dusk or dawn with B(y) values greater than zero or less than zero, respectively.

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

1984-01-01

120

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

121

The effects of 8 Helios observed solar proton events of interplanetary magnetic field fluctuations  

NASA Technical Reports Server (NTRS)

There have been recent suggestions that large fluxes during solar energetic particle events may produce their own turbulence. To verify this argument it becomes essential to find out whether these flows cause an enhancement of interplanetary magnetic field fluctuations. In the present work, power and helicity spectra of the IMF before, during and after 8 Helios-observed solar proton events in the range 0.3 - 1 AU are analyzed. In order to detect proton self generated waves, the time evolution of spectra are followed.

ValdezGalicia, J. F.; Alexander, P.; Otaola, J. A.

1995-01-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

123

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

124

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

E-print Network

magnetic fields associ- ated with the storms in October ­ November 2003. We used space and ground basedStructure of magnetic fields in NOAA active regions 0486 and 0501 and in the associated consecutive days, caused intense ge- omagnetic storms. In this paper we analyze solar and interplanetary

Yurchyshyn, Vasyl

125

The Entropy Index (EI): an Auxiliary Tool to Identify the Occurrence of Interplanetary Magnetic Clouds  

E-print Network

By the study of the dynamical processes related to entropy, this work aims to create a mathematical tool to identify magnetic clouds (MCs) in the interplanetary space using only interplanetary magnetic field (IMF) data. Used as basis for an analysis methodology, the spatio-temporal entropy (STE) measures the image (recurrence plots) "structuredness" in both space and time domains. Initially we worked with the Huttunen et al. 2005's dataset and studied the 41 MCs presenting a shock wave identified before the cloud. The STE values for each Bx, By, Bz IMF time series, with dimension and time delay equal to one, were respectively calculated. We found higher STE values in the sheaths and zero STE values in some of the three components in most of the MCs (30 among 41 events). In a physically consistent manner, data windows of 2500 magnetic records were selected as the calculation interval for the time series. As not all MCs have zero STE simultaneously, we created a standardization index (an entropy index, called a...

Ojeda, G A; Calzadilla, M A; Domingues, M O

2011-01-01

126

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

127

Evolution of interplanetary coronal mass ejections and magnetic clouds in the heliosphere  

NASA Astrophysics Data System (ADS)

Interplanetary Coronal Mass Ejections (ICMEs), and more specifically Magnetic Clouds (MCs), are detected with in situ plasma and magnetic measurements. They are the continuation of the CMEs observed with imagers closer to the Sun. A review of their properties is presented with a focus on their magnetic configuration and its evolution. Many recent observations, both in situ and with imagers, point to a key role of flux ropes, a conclusion which is also supported by present coronal eruptive models. Then, is a flux rope generically present in an ICME? How to quantify its 3D physical properties when it is detected locally as a MC? Is it a simple flux rope? How does it evolve in the solar wind? This paper reviews our present answers and limited understanding to these questions.

Démoulin, Pascal

2014-01-01

128

Small-scale electrodynamics of the cusp with northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Possible low-altitude field signatures of merging occurring at high latitudes during a period of strong northward directed interplanetary magnetic field are reported. Large electric and magnetic field spikes detected at the poleward edge of the magnetosheathlike particle precipitation are interpreted as field signatures of the low-altitude footprint of such merging line locations. A train of phase-shifted, almost linearly polarized electric and magnetic field fluctuations was detected just equatorward of the large electromagnetic spike. It is argued that these may be due to either ion cyclotron waves excited by penetrating magnetosheath ions or transient oscillations in the frame of convecting plasma, brought about by the sudden change in the flow at the magnetospheric end of the field line.

Basinska, Ewa M.; Burke, William J.; Maynard, Nelson C.; Hughes, W. J.; Winningham, J. D.; Hanson, W. B.

1992-01-01

129

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

130

Properties of Kelvin-Helmholtz waves at the magnetopause under northward interplanetary magnetic field: Statistical study  

NASA Astrophysics Data System (ADS)

We search the plasma and magnetic field data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes B and C during 2008 and 2009 for observation evidences of the Kelvin-Helmholtz instability (KHI). Fourteen KHI events with rolled-up vortices are identified under the northward interplanetary magnetic field (IMF) at the low-latitude boundary layer (LLBL). We collect another 42 events reported from the observations of the Geotail, Double Star TC-1, and Cluster for a statistical study of the KH wave properties. All the 56 rolled-up KH wave events are quantitatively characterized by the dominant period, phase velocity, and the wavelength. We further explore the relationship between the KH wave period and the solar wind velocity (VSW) and the IMF clock angle. It is found that the KH period tends to be shorter under a higher VSW, and longer with a larger IMF clock angle. The spatial distribution of the KH wavelength shows a longitudinal growth with increasing distance from the subsolar point along the flank magnetopause. The statistical results provide new insights for the development of KH waves and their connection with the interplanetary conditions and deepen our understanding of the KHI at the magnetopause.

Lin, Dong; Wang, Chi; Li, Wenya; Tang, Binbin; Guo, Xiaocheng; Peng, Zhong

2014-09-01

131

Dependence of the durations of main and recovery phases of magnetic storms on the interplanetary driver type  

NASA Astrophysics Data System (ADS)

One of the main space weather phenomena is the magnetic storm. In this paper the durations of main and recovery phases of magnetic storms induced by different types of large-scale solar-wind streams (Sheath, magnetic cloud (MC), Ejecta and CIR) are studied on the basis of OMNI data base during 1976-2000. Though the main phase depends on external sources, and the recovery phase depends on internal processes, both durations depend on types of interplanetary drivers. On the average, duration of main phase of storms induced by compressed regions (CIR and Sheath) is shorter than by MC and Ejecta while duration of recovery phase of CIR- and Sheath-induced storms is longer. Analysis of durations of individual storms shows that durations of main and recovery phases anti-correlate for CIR- and Sheath-induced storms and there is not dependence between them for (MC+Ejecta)-induced storms. This work was supported by the Russian Foundation for Basic Research, project 13-02-00158, and by Program 22 of Presidium of the Russian Academy of Sciences.

Yermolaev, Yuri; Lodkina, Irina; Nikolaeva, Nadezhda; Yermolaev, Mikhail

2014-05-01

132

AN ANALYSIS OF MAGNETOHYDRODYNAMIC INVARIANTS OF MAGNETIC FLUCTUATIONS WITHIN INTERPLANETARY FLUX ROPES  

SciTech Connect

A statistical analysis of magnetic flux ropes, identified by large-amplitude, smooth rotations of the magnetic field vector and a low level of both proton density and temperature, has been performed by computing the invariants of the ideal magnetohydrodynamic (MHD) equations, namely the magnetic helicity, the cross-helicity, and the total energy, via magnetic field and plasma fluctuations in the interplanetary medium. A technique based on the wavelet spectrograms of the MHD invariants allows the localization and characterization of those structures in both scales and time: it has been observed that flux ropes show, as expected, high magnetic helicity states (|?{sub m}| in [0.6: 1]), but extremely variable cross-helicity states (|?{sub c}| in [0: 0.8]), which, however, are not independent of the magnetic helicity content of the flux rope itself. The two normalized MHD invariants observed within the flux ropes tend indeed to distribute, neither trivially nor automatically, along the ?(?{sub m}{sup 2}+?{sub c}{sup 2})=1 curve, thus suggesting that some constraint should exist between the magnetic and cross-helicity content of the structures. The analysis carried out has further showed that the flux rope properties are totally independent of their time duration and that they are detected either as a sort of interface between different portions of solar wind or as isolated structures embedded in the same stream.

Telloni, D. [National Institute for Astrophysics, Astrophysical Observatory of Torino, Via Osservatorio 20, I-10025 Pino Torinese (Italy); Perri, S.; Carbone, V. [Department of Physics, University of Calabria, Ponte P. Bucci Cubo 31C, I-87036 Rende (Italy); Bruno, R.; D Amicis, R. [National Institute for Astrophysics, Institute for Space Astrophysics and Planetology, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy)

2013-10-10

133

Dependence of the polar cusp on the north--south component of the interplanetary magnetic field  

Microsoft Academic Search

Ogo 5 observations of the polar cusp on November 1, 1968. show that the ; north-south component of the interplanetary field exhibits control over both the ; location of and the physical processes occurring in the polar cusp. When the ; interplanetary field turned from north to south, the polar cusp moved equatorward. ; During intervals when the interplanetary field

Margaret G. Kivelson; Christopher T. Russell; Marcia Neugebauer; Frederick L. Scarf; Robert W. Fredricks

1973-01-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

135

Large-Scale Variations of the Interplanetary Magnetic Field: Voyager 1 and 2 Observations Between 1-5 au.  

National Technical Information Service (NTIS)

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 ...

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

1981-01-01

136

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

137

Substorm aurora and magnetic tail dynamics during interplanetary shock compression: THEMIS observations  

NASA Astrophysics Data System (ADS)

Fast and forward interplanetary shocks compress and squeeze the Earth magnetosphere and cause a series of magnetospheric and ionospheric reactions. In addition to the enhancement of chorus, electromagnetic ion cyclotron (EMIC) waves and magnetospheric hiss, the ionospheric convection is enhanced as well. Shock aurora is generated, which is a phenomenon first an auroral brightness onset near local noon right after the shock impingement then followed by a fast anti-sunward auroral propagation along the oval. It has been found that substorm auroral activity can be significantly intensified by the shock compression when the shock upstream magnetic field was in southward in a certain period of time. This paper will present recent results based on the THEMIS spacecraft and ground-based observations. With multiple spacecraft in the magnetotail, the complex dynamics of the compressed tail is identified and analyzed. Correlations between the tail dynamics and substorm auroral variations will be discussed. *On-leave from Jet Propulsion Laboratory

Angelopoulos, Vassilis; Zhou, Xiaoyan

2012-07-01

138

Global features of Kelvin-Helmholtz waves at the magnetopause for northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We investigate the global features of Kelvin-Helmholtz waves (KHW) at the low-latitude magnetopause for constant northward interplanetary magnetic field conditions, using global magnetohydrodynamic simulations. The root-integrated power (RIP) of X component of bulk velocity is employed to analyze the magnetopause mode of KHW along the boundary layer. The RIP distribution of the outer KHW is much broader than that of the inner one, and the maximum amplitude of global KHW occurs near the dawn/dusk terminator regions. In the dayside magnetopause, the phase of the waveform at middle latitudes leads to that at low latitudes, while the situation reversed in the nightside. The global evolution of KHW phases is a representation of an interesting feature that the axis of the Kelvin-Helmholtz vortex aligns with the geomagnetic field lines. We suggest that the reported features may also exist in other KHW active regions with flow-sheared plasma.

Li, Wenya; Wang, Chi; Tang, Binbin; Guo, Xiaocheng; Lin, Dong

2013-08-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

141

ULF cusp pulsations: Diurnal variations and interplanetary magnetic field correlations with ground-based observations  

SciTech Connect

In this paper the authors establish the Pc 5 magnetic pulsation signatures of the cusp and boundary regions for the high-latitude dayside cusp region. These signatures were determined by comparing spectrograms of the magnetic pulsations with optical observations of particle precipitation regions observed at the cusp. The ULF pulsations have a diurnal variation, and a cusp discriminant is proposed using a particular narrow-band feature in the pulsation spectrograms. The statistical distribution of this pattern over a 253-day period resembles the statistical cusp description using particle precipitation data from the Defense Meterological Satellite Program (DMSP). The distribution of the ground-based cusp discriminant is found to peak 1 hour earlier than the DMSP cusp distribution. This offset is due to the interplanetary magnetic field (IMF) being predominantly negative B{sub y} for the period when the data were collected. The authors find the diurnal variations so repeatable that only three main categories have statistically different IMF distributions. The identification of the signatures in the magnetic spectrograms of the boundary regions and central cusp allows the spectrogram to be used as a {open_quotes}time line{close_quotes} that shows when the station passed under different regions of the dayside oval. 36 refs., 11 figs., 1 tab.

McHarg, M.G. [Air Force Academy, Colorado Springs, CO (United States)] [Air Force Academy, Colorado Springs, CO (United States); Olson, J.V. [Univ. of Alaska, Fairbanks, AK (United States)] [Univ. of Alaska, Fairbanks, AK (United States); Newell, P.T. [Johns Hopkins Univ., Laurel, MD (United States)] [Johns Hopkins Univ., Laurel, MD (United States)

1995-10-01

142

On the relationship between interplanetary coronal mass ejections and magnetic clouds  

NASA Astrophysics Data System (ADS)

The relationship of magnetic clouds (MCs) to interplanetary coronal mass ejections (ICMEs) is still an open issue in space research. The view that all ICMEs would originate as magnetic flux ropes has received increasing attention, although near the orbit of the Earth only about one-third of ICMEs show clear MC signatures and often the MC occupies only a portion of the ICME. We have performed a systematic comparison of the cases where ICME and MC signatures coincided and where ICME signatures extended significantly beyond the MC boundaries. We found clear differences in the ICME properties (eg., speed, magnetic field magnitude), in the ambient solar wind structure, and in the solar cycle dependence for these two event types. We show that the MC and the regions of ICME-related plasma in front and behind the MC have all distinct characteristics enforcing the conception that they have intrinsically different origin or evolve differently. Erosion of magnetic flux in front of the ICME may also reconfigure the initial three-part CME seen in white-light images to a more complex ICME, but the geometrical effect (i.e. the encounter through the CME leg and/or far from the flux rope center) has little contribution to the observed mismathch in the MC and ICME boundary times. We will also discuss ramifications to CME and space weather research.

Kilpua, Emilia; Isavnin, Alexey; Vourlidas, Angelos; Koskinen, Hannu; Rodriguez, Luciano

2013-04-01

143

Magnetospheric convection in the presence of interplanetary magnetic field By: A conceptual model and simulations  

NASA Astrophysics Data System (ADS)

Existing observations from ISEE 3 and new observations from Galileo show that when the interplanetary magnetic field (IMF) has a By component, a By 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 By on the closed field lines (which is in the same direction as the IMF By) is also seen. We suggest that for a positive IMF By, the magnetopause is open only in the north dawn and south dusk quadrants of the magnetotail. The continuity of magnetic field across the open boundary then requires that a By component be present in the magnetosphere in these quadrants but not in the other two quadrants. We present a model of the magnetospheric convection that postulates cross-tail flows in the mantle/lobe system and the plasma sheet. We suggest that shear flows between the northern and the southern halves of the plasma sheet generate a By component on the closed magnetic field lines. The model is consistent with the two-cell ionospheric convection models constructed from electric field observations by Heppner and Maynard [1987]. Results from global MHD simulations confirm the main features of the proposed model.

Khurana, Krishan K.; Walker, Raymond J.; Ogino, Tatsuki

1996-03-01

144

DETECTION OF CURRENT SHEETS AND MAGNETIC RECONNECTIONS AT THE TURBULENT LEADING EDGE OF AN INTERPLANETARY CORONAL MASS EJECTION  

SciTech Connect

The relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection detected by four Cluster spacecraft on 2005 January 21 is studied. We report the observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer with the following characteristics: (1) a Kolmogorov power spectrum in the inertial subrange of the magnetic turbulence, (2) the scaling exponent of structure functions of magnetic fluctuations exhibiting multi-fractal scaling predicted by the She-Leveque magnetohydrodynamic model, and (3) bifurcated current sheets with the current density computed by both single-spacecraft and multi-spacecraft techniques.

Chian, Abraham C.-L. [California Institute of Technology, Pasadena, CA 91125 (United States); Munoz, Pablo R., E-mail: abraham.chian@gmail.com, E-mail: pablocus@gmail.com [National Institute for Space Research (INPE) and World Institute for Space Environment Research (WISER), P.O. Box 515, Sao Jose dos Campos SP 12227-010 (Brazil)

2011-06-01

145

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

146

Survey of Potential Impactors at 1AU Using Interplanetary Magnetic Field Data  

NASA Astrophysics Data System (ADS)

Near-Earth Objects (NEOs) in the size range of 10m to 1000m could cause significant damage if they entered the Earth's atmosphere. However, objects in the lower end of the size range are below the detectability limit of terrestrial optical telescopes. In addition, detection of potential impactors is difficult when the NEOs come to the Earth from the direction of the Sun, such occurred with the Chelyabinsk bolide. However, by identifying so-called interplanetary field enhancements (IFEs) at 1AU, we are able to identify meteoroid streams that contain enhanced densities of potential impactors. We make our detections when these impactors strike other bodies in space. When these rates of impact rise significantly above the average we can identify the parent body for the stream thus identifying their approximate orbits and issue a warning.

Lai, H. R.; Russell, C. T.; Delzanno, G. L.; Wei, H. Y.

2013-09-01

147

Parameterization of the Defense Meterological Satellite Program ionospheric electrostatic potentials by the interplanetary magnetic field strength and direction  

Microsoft Academic Search

In this study we applied a linear regression analysis technique to the interplanetary magnetic field (IMF) data and the ionospheric electrostatic potentials obtained from thermal ion drift measurements made by the Defense Meterological Satellite Program (DMSP) satellites F8 and F10-F13 in 1993-1996. The ionospheric potentials are binned by every 1° of the corrected geomagnetic latitude and 0.5 hour of magnetic

V. O. Papitashvili; F. J. Rich; M. A. Heinemann; M. R. Hairston

1999-01-01

148

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

149

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

150

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

Microsoft Academic Search

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

Leif Svalgaard; Edward W. Cliver; Philippe Lesager

2003-01-01

151

Reliability of prediction of the magnetosheath BZ component from interplanetary magnetic field observations  

NASA Astrophysics Data System (ADS)

In the present statistical study, we discuss a probability of simultaneous observations of the same sign of the magnetic field BZ component in the solar wind and magnetosheath. The analysis is based on 5 min data from four spacecraft (Interball-1, IMP 8, Cluster, and THEMIS) operating in different phases of the solar cycle in the magnetosheath. Their measurements are compared with Wind interplanetary magnetic field (IMF) observations, and other available upstream monitors (ACE, THEMIS B, and OMNI database) are tested for some sets. We can conclude that the probability of observations of the same BZ sign in the solar wind and in the magnetosheath is surprisingly very low from a general point of view. The probability changes through the solar cycle, being larger at the solar minimum. Regardless of the solar cycle phase, this probability is close to 0.5 (random coincidence) for IMF ?BZ? < 1 nT, and it is a rising function of the BZ value. Distant solar wind monitors do not guarantee the same sign of the BZ component, even for values of IMF BZ exceeding ±9 nT, but such large values are observed about 3-5% of the time. A better probability profile is reached for a monitor located just upstream (less than 30 RE), as is demonstrated for the THEMIS project.

Šafránková, J.; Hayosh, M.; Gutynska, O.; N?me?ek, Z.; P?ech, L.

2009-12-01

152

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

153

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

NASA Astrophysics Data System (ADS)

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

Muñoz, P. R.; Chian, A. C.

2013-12-01

154

Solar sources of interplanetary southward B/sub z/ events responsible for major magnetic storms (1978--1979)  

SciTech Connect

Tsurutani et al. (1988) analyzed the 10 intense interplanetary southward B/sub z/ events that led to major magnetic storms (Dst<-100 nT) during the 500-day interval, August 16, 1978, through December 28, 1979. In this paper we report solar sources of the major storms and discuss their interplanetary effects. Seven of the sources of the 10 major storms are flares and 3 are prominence eruptions. The ratio is consistent with frequency of these two types of events occurring on the Sun during this period. The flares range from M1 to X2 in peak soft X ray emissions. However, the largest of the 10 storms (Dst = -220 nT) as well as the two strongest shocks (M>3.0) are associated with prominence eruptions. For three of the five southward B/sub z/ events in which the driver gases are the causes of the intense southward field leading to magnetic storms, the photospheric fields of the solar sources have no dominant southward component, indicating the driver gas fields do not always result from a simple outward convection of solar magnetic fields. Finally we compare the solar events and their resulting interplanetary shocks and find that the standard solar parameters do not correlate with the strengths of the resulting shocks at 1 AU. The implications are discussed. copyright American Geophysical Union 1989

Tang, F.; Tsurutani, B.T.; Gonzalez, W.D.; Akasofu, S.I.; Smith, E.J.

1989-04-01

155

Precipitation of low energy electrons at high latitudes: Effects of substorms, interplanetary magnetic field and dipole tilt angle  

NASA Technical Reports Server (NTRS)

Data from the auroral particles experiment on OGO-4 were used to study effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons. It was found that: (1) The high-latitude zone of 700 eV electron precipitation in late evening and early morning hours moves equatorward by 5 to 10 deg during substorms. (2) The low-latitude boundary of polar cusp electron precipitation at 9 to 15 hours MLT also moves equatorward by several degrees during substorms and, in the absence of significant substorm activity, after a period of southward interplanetary magnetic field. (3) With times containing substorm activity or a southward interplanetary magnetic field eliminated, the low-latitude boundary of polar cusp electron precipitation is found to move by approximately 4 deg over the total yearly range of tilt angles. At maximum winter and summer conditions the invariant latitude of the boundary is shown to shift by approximately -3 deg and +1 deg respectively from its equinox location.

Burch, J. L.

1972-01-01

156

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

157

The interplanetary magnetic field influences middle-latitude surface atmospheric pressure  

NASA Astrophysics Data System (ADS)

Results have been published over several decades that indicate a meteorological response in the polar regions to fluctuations in the east-west component of the interplanetary magnetic field (IMF), By. There is evidence that this Sun-weather coupling occurs via the global atmospheric electric field. It has been assumed that the effect maximises at high latitudes and is negligible at low and mid latitudes because the IMF-induced convection electric field is concentrated in the polar ionospheres. However, the spatial variation of the IMF-weather coupling has not previously been investigated in detail, neither have the global consequences of such forcing on the atmosphere. Here we demonstrate a previously unrecognised influence of IMF By on mid-latitude surface pressure. The difference between the mean surface pressure for high positive and high negative values of IMF By possesses a statistically-significant mid-latitude wave structure, similar in location and form to the cyclones and anti-cyclones produced by the action of atmospheric Rossby waves on the jet stream. Thus our results indicate that a mechanism that is known to produce atmospheric responses to the IMF in the polar regions is also able to modulate pre-existing weather patterns at mid-latitudes. A relatively localised and small amplitude solar influence on the upper atmosphere could therefore have an important effect, via the nonlinear evolution of storm tracks, on critical processes such as European climate and the breakup of Arctic sea ice.

Lam, Mai Mai; Chisham, Gareth; Freeman, Mervyn

2013-04-01

158

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

159

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

160

Analysis and synthesis of coronal and interplanetary energetic particle, plasma, and magnetic field observations over three solar rotations.  

NASA Technical Reports Server (NTRS)

In a previous paper (Krimigis et al., 1971), simultaneous observations in 1967 of solar particle events at low (less than 1 MeV) energies were presented. In the present paper, the full complement of simultaneous plasma, magnetic field, and energetic particle data is combined, and a complete analysis is made of all the events discussed in the original paper. The essential concept of 'collimated convection' is introduced, whereby the bulk velocity along the field lines of low-energy solar particles is independent of solar local plasma velocity, and the particles are strongly collimated along the field line with no transverse velocity component other than that of the field line itself. Collimated convection effects are shown to exist in small-scale convection and large-scale evolution of particle fluxes; the particle fluxes are, in turn, used to delineate the small-scale and large-scale evolution of the interplanetary magnetic field. Use of collimated convection is made in demonstrating a technique whereby energetic particle intensity profiles in the interplanetary medium can be related to equatorial high coronal magnetic field structures, by using the instantaneous solar wind velocity. This technique is applied in mapping particle intensities from Mariner 5 onto H alpha synoptic charts of chromospheric magnetic field structures for Carrington rotations 1523 to 1525.

Roelof, E. C.; Krimigis, S. M.

1973-01-01

161

Interplanetary medium data book, supplement, 1975 - 1978  

NASA Technical Reports Server (NTRS)

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

King, J. H.

1979-01-01

162

Response of the F Region Zonal Electricfield at the Magnetic Equator to the Interplanetary Electric Filed Fluctuations during Disturbed Days  

NASA Astrophysics Data System (ADS)

The interplanetary magnetic field plays a prominent role in the transfer of energy from solar wind to the magnetosphere there after into the lower atmosphere. During magnetically dis-turbed periods, significant perturbations occur at equatorial as well as at higher latitudes. The fluctuations in the equatorial F-region electric field are thought to be due to the perturbations in the neutral air due to the presence of a variety of waves or due to the penetration of in-terplanetary electric field into the low latitude ionosphere. The simultaneous observation of electric field at the equatorial F-region (Ey) and at magnetopause (Eyy) enables us to study the relationship between them. The zonal component of the equatorial dynamo electric field Ey causes vertical plasma drifts. Large and rapid southward and northward reversals of Bz component of interplanetary magnetic field impose an east-west electric field which penetrate through the magnetosphere down to the equatorial ionosphere. The induced electric field is given by E = -V x Bz, V is the solar wind velocity and B is the IMF and would be opposite to the normal Sq electric field. In this work, the effect of the interplanetary electric field on the equatorial ionospheric zonal electric field during magnetically disturbed days has been dis-cussed. The HF radar system operated at 5.5MHz and a Multi frequency Radar operated at 2.5, 3.5 and 4.5 MHz at the Kerala University have been used for measuring vertical drifts in the equatorial F region. The interplanetary magnetic field components and solar wind velocity are obtained from IMP-8 and WIND satellites .The comparison of the fluctuations in EYY and EY presented in this work reveals that the fluctuations simultaneously present in both EYY and EY are different in magnitude and they are in anti-phase during the day-time and in phase at night. In the time interval between connection and reconnection, geomagnetic field lines are open and IEF can penetrate to the polar ionosphere causing sudden changes in cross polar cap potential. This electric field can be instantaneously mapped to low latitudes adopting a transverse magnetic (TM) mode of propagation through the Earth -Ionosphere waveguide. It is found that the southward excursion of IMF Bz during both day and night enhances the vertical plasma drift (upward during day and downward at night). But the northward excursion of IMF Bz produces an eastward electric field at night and hence the it suppresses the drift. The com-parison of the spectra of fluctuations in Eyy and Ey reveals that the low frequency fluctuations are simultaneously present in both Eyy and Ey and the difference in magnitude of their power suggest the frequency response of the magnetosphere and ionosphere to the fluctuations in the interplanetary medium.

Bhuvanendran, C. Bhuvanendran; Prabhakaran Nayar, S. R.; Mathew, Tiju Joseph

163

Response of ionospheric convection to changes in the interplanetary magnetic field: Lessons from a MHD simulation  

NASA Astrophysics Data System (ADS)

Characteristics of magnetospheric and high-latitude ionospheric convection pattern responses to abrupt changes in the interplanetary magnetic field (IMF) orientation have been investigated using an MHD model with a step function reversal of IMF polarity (positive to negative BY) in otherwise steady solar wind conditions. By examining model outputs at 1 min intervals, we have tracked the evolution of the IMF polarity reversal through the magnetosphere, with particular attention to changes in the ionosphere and at the magnetopause. For discussion, times are referenced relative to the time of first contact (t=0) of the IMF reversal with the subsolar nose of the magnetopause at ~10.5 RE. The linear change in large-scale ionospheric convection pattern begins at t=8min, reproducing the difference pattern results of Ridley et al. [1997, 1998]. Field-aligned current difference patterns, similarly derived, show an initial two-cell pattern earlier, at t=4min. The current difference two-cell pattern grows slowly at first, then faster as the potential pattern begins to change. The first magnetic response to the impact of the abrupt IMF transition at the magnetopause nose is to reverse the tilt of the last-closed field lines and of the ``first''-open field lines. This change in tilt occurs within the boundary layer before merging of IMF with closed magnetospheric field lines starts. In the case of steady state IMF BY, IMF field lines undergo merging or ``changing partners'' with other IMF field lines, as they approach the nose and tilt in response to currents. When the BY reversal approaches the magnetopause nose, IMF field lines from behind the reversal overtake and merge with those in front of the reversal, thus puncturing the reversal front and uncoupling the layer of solar wind plasma in the reversal zone from the magnetosphere. The uncoupled layer propagates tailward entirely within the magnetosheath. Merging of closed magnetospheric field lines with the new polarity IMF begins at t=3min and starts to affect local currents near the cusp 1 min later. While merging starts early and controls the addition of open flux to the polar cap, large-scale convection pattern changes are tied to the currents, which are controlled in the boundary layers. The resulting convection pattern is an amalgamation of these diverse responses. These results support the conclusion of Maynard et al. [2001b], that the small convection cell is driven from the opposite hemisphere in BY-dominated situations.

Maynard, N. C.; Siscoe, G. L.; Sonnerup, B. U. Ö.; White, W. W.; Siebert, K. D.; Weimer, D. R.; Erickson, G. M.; Schoendorf, J. A.; Ober, D. M.; Wilson, G. R.

2001-10-01

164

Solar wind and interplanetary magnetic field features before magnetic storm onset  

Microsoft Academic Search

The presented results, concerning the features of the sola r wind plasma structure as observed by spacecraft upstream of Earth, could be used for development of middle-term forecasts of magnetic storms. We have analyzed 1-hour data for 1995-2005 and a whole year of 1-min data during solar minimum (1995) and during solar maximum (2000) with 48 and 60 storms, respectively.

O. Khabarova; V. Pilipenko; M. J. Engebretson; E. Rudenchik

2007-01-01

165

THE BASTILLE DAY MAGNETIC CLOUDS AND UPSTREAM SHOCKS: NEAR-EARTH INTERPLANETARY OBSERVATIONS  

E-print Network

.8 nT on the axis) and the large radius (R0 = 0.189 AU) of the flux tube. MC2's average speed, Delaware 19716, U.S.A. 5Department of Physics and Astronomy, University of Iowa, IO 52242, U.S.A. 6Emergent of observation. The estimated axial magnetic flux carried by MC2 was 52 Ã? 1020 Mx, which is about 5 times

Richardson, John

166

Observations of solar-wind-driven progression of interplanetary magnetic field B{sub Y}-related dayside ionospheric disturbances  

SciTech Connect

Observations from August 2, and 3, 1991, of poleward progressing, dayside convection disturbances accompanied by geomagnetic perturbations and ionospheric radio wave absorption have been analyzed and compared to variations in the solar wind parameters as observed from the IMP 8 satellite. The convection disturbances appear to start at dayside cusp latitudes from where they progress antisunward to high latitudes. The reported observations have enabled calculations of the progression directions and velocities and precise estimates of the delays between solar wind variations as measured by the IMP 8 satellite and ionospheric convection changes as observed from an array of polar magnetic observatories. The progressing ionospheric disturbance events occur during intervals of southward interplanetary magnetic fields (negative interplanetary magnetic field (IMF) B{sub Z} component); they are found to be closely related to variations of the east-west component B{sub Y} of the IMF. The close coupling between the solar wind and the polar ionosphere(s) is explained in an open magnetospheric model in which the geomagnetic field extending from a localized region of the dayside polar cap merges with the southward interplanetary field. Variations in the IMF B{sub Y} component are reproduced in corresponding modulations of the east-west component of the plasma flow at the ionospheric foot points of the connecting `open` field lines. The perturbations of the plasma flow persist while the open field lines are convected with the ionospheric plasma across part of the dayside polar cap. The observed geomagnetic perturbations result from the combined effects of field-aligned currents and horizontal ionospheric currents, notably the convection-related Hall currents. The associated radio wave absorption events are explained as the result of E region electron heating by the horizontal electric fields associated with the convection enhancements. 48 refs., 16 figs., 3 tabs.

Stauning, P.; Friis-Christensen, E. [Danish Meterological Institute, Copenhagen (Denmark)] [Danish Meterological Institute, Copenhagen (Denmark); Clauer, C.R. [Univ. of Michigan, Ann Arbor, MI (United States)] [Univ. of Michigan, Ann Arbor, MI (United States)

1995-05-01

167

Modulation of trapped energetic electrons at 6.6 earth radii by the direction of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Energetic (energies greater than 1.6 and 3.9 MeV) trapped electron fluxes observed at the synchronous altitude during 1974 and 1975 by an experiment aboard ATS-6 exhibit a modulation in intensity which is correlated with the passage of sector-structure boundaries of the interplanetary magnetic field past the earth. The electron fluxes reach equilibrium intensities during the time the magnetosphere is in a given IMF sector; these fluxes are highest in the fall for (+) sectors and highest in the spring for (-) sectors.

Paulikas, G. A.; Blake, J. B.

1976-01-01

168

Dependence of solar wind velocity and interplanetary magnetic field on Pc4 magnetic pulsations at low latitudes in India  

NASA Astrophysics Data System (ADS)

Employing an array of three low latitude stations situated in India at Hanley (HAN) (L=1.178 R_{E}), Nagpur (NAG) (L=0.974 R_{E}) and Pondicherry (PON) (L=0.910 R_{E} ), a recent study has been carried out for Ultra Low Frequency (ULF) Magneto-hydrodynamic (MHD) waves in the 6.7 to 22.2 mHz frequency range, designated as Pc4 Magnetic Pulsations. These are observed mainly in the dayside (0400-2000 hrs LT) magnetosphere. The present research has been undertaken for describing the dependence of low latitude Pc4 occurrence (with time resolution of 1 minute) on the Solar Wind Velocity (V_{SW}) (hourly data) and the Interplanetary Magnetic Field (IMF) (hourly data) for the period range 01 January to 31 December, 2005. The mean measured frequency ranges of occurrence for HAN, NAG and PON were determined as 12.9 to 14.6 mHz, 12.7 to 14.2 mHz and 12.0 to 15.0 mHz respectively. The results for the whole year 2005 provided similar patterns of Pc4 occurrence for V_{SW} at all the three stations. Although Pc4 occurrence was reported for V_{SW} ranging from 250 to 1000 km/s, yet the major Pc4 events occurred for a V_{SW} range of 300-700 km/sec. Even though at all the three stations, the IMF magnitude spread up to 22 nT, yet the majority of Pc4 events occurred for a narrower range of 2-10 nT. However, it is important to note that the peak in the Pc4 occurrence was observed for IMF range of 3 to 6 nT. The implications of these results are reported in this study.

Ansari, I. A.; Nafees, K. A.; Sinha, A. K.; Pathan, B. M.

169

Optical Auroral Observations at High Latitudes to Investigate Processes at the Foot of Magnetic Field Lines That Map Into the Interplanetary Medium  

Microsoft Academic Search

At high magnetic latitudes the magnetic field lines, are open and they map from the ground into the interplanetary medium. Due to the larger offset between the geographic and geomagnetic poles in the Southern hemisphere the Antarctic Continent is especially suitable for making visible wavelength optical observations of the foot of such field lines. Near the Austral winter solstice the

S. B. Mende

2005-01-01

170

Density and temperature evolution of the plasma sheet during a simulated interval of northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We investigate the evolution of the hot component of plasma sheet ions during an extended interval of northward interplanetary magnetic field and assess whether transport can explain the observed cooling of the hot component ions reported by Wing et al. (2005). Our approach is to trace the guiding center particle drift of protons in a magnetic field from the Tsyganenko 2001 (T01) model and in an electric field from the Weimer 2000 model. We then map the phase space distributions to realistic source distributions based on Time History of Events and Macroscale Interactions during Substorms observations. Our simulation results show that magnetic drift is not a significant cooling mechanism for the hot component ions of the plasma sheet on the duskside of the magnetopause, but gradient drift does cool the hot component plasma on the dawnside of the magnetopause.

Mata, Wendy J.; Lemon, Colby; Wang, Chih-Ping; Lyons, Larry R.

2014-06-01

171

Predictions of substorms following northward turnings of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Substorms are often observed to occur when the interplanetary magnetic field (IMF) turns northward at the end of intervals of southward IMF. Despite the significant correlation between northward turnings and substorms, a direct causal relationship between northward turnings and substorms has not been demonstrated. If such a causal relationship exists, then we should be able to predict that substorms will occur within a particular interval following the observation of a northward turning in the IMF. We have searched Wind IMF data and identified 16 strong northward turnings that following intervals of steady, southward IMF. To enhance the chances that the selected northward turnings impacted the magnetosphere, we required that each of them be also observed at either Geotail or IMP 8 while the separation of the second spacecraft from Wind was more that 10RE in the y direction. Additionally, we required that either the second satellite was on the opposite side of the y=0 plane from Wind or that one of the satellites was near y=0. These two spacecraft observations also allowed us to more accurately predict the arrival times of the northward turnings at the Earth than we could by using data only from one spacecraft. Of the predicted substorms, 10 predictions were clearly successful to within +/-8 min. Five predictions failed, but these failures reveal important new criteria that must be satisfied for a northward turning to cause a substorm. Three of the failures were caused by an increase in |BYGSM| that occurred simultaneously with the northward turning. This suggests that the triggering is associated with sharp reductions in the magnetospheric electric field, since increases in |BYGSM| negate the convection reduction associated with northward turnings. Two of the failures occurred for cases with the weakest southward IMF preceding the northward turning, which improves our criteria for the strength of the southward IMF that must precede a substorm. The final northward turning resulted in unusual auroral activity. These results establish the predictability of substorms following sharp northward turnings of the IMF and demonstrate that a direct causal relationship between northward turnings and substorm onset exists.

Blanchard, G. T.; Lyons, L. R.; Spann, J.

2000-01-01

172

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

SciTech Connect

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

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

1994-04-01

173

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

174

Interplanetary origin of geomagnetic storms  

Microsoft Academic Search

Around solar maximum, the dominant interplanetary phenomena causing intense magnetic storms (Dstinterplanetary\\u000a manifestations of fast coronal mass ejections (CMEs). Two interplanetary structures are important for the development of storms,\\u000a involving intense southward IMFs: the sheath region just behind the forward shock, and the CME ejecta itself. Whereas the\\u000a initial phase of a storm is caused by the

Walter D. Gonzalez; Bruce T. Tsurutani; Alicia L. Clúa de Gonzalez

1999-01-01

175

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

176

A statistical study of the spatial structure of interplanetary magnetic field substorm triggers and their associated magnetic response  

NASA Astrophysics Data System (ADS)

An outstanding question in magnetospheric physics is whether substorms are always triggered externally by changes in the interplanetary magnetic field (IMF) or solar wind plasma, or whether they sometimes occur spontaneously as a result of internal processes. An apparent association between northward turnings of the IMF and substorm onset has been frequently demonstrated, but it is also found that not all substorms are triggered. Previous studies have shown that the ratio of triggered and nontriggered substorms is about 60/40. A surprising finding is that substorms classified as triggered exhibit a stronger response than nontriggered substorms. It has been suggested that this may be due to undetected small-scale structures in the IMF which presumably have weak driving fields of short duration and hence transfer less energy to the magnetosphere. In this work we use a large database of 1978~1985 ISEE 2 and IMP 8 IMF observations to investigate whether small-scale structures occur frequently enough to account for the 40% nontriggered substorms. We find that the probability of observing IMF small-scale structures is less than 13%. This low probability (13%) does not match the occurrence frequency of 40% for nontriggered substorm onsets. It is thus unlikely that all nontriggered substorms can be attributed to small-scale IMF structures missed by an upstream monitor. Another interesting finding is that the small-scale IMF B z triggers do not seem to create significant AL response but the large-scale IMF B z triggers do. The median curve shows a sudden sharp drop of the AL index at the time the IMF trigger is expected to arrive at the magnetopause. This suggests that some substorms must be associated with the IMF triggers.

Hsu, Tung-Shin; McPherron, Robert L.

2009-02-01

177

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

178

PROPAGATION OF SOLAR ENERGETIC PARTICLES IN THREE-DIMENSIONAL INTERPLANETARY MAGNETIC FIELDS: IN VIEW OF CHARACTERISTICS OF SOURCES  

SciTech Connect

In this paper, a model of solar energetic particle (SEP) propagation in the three-dimensional Parker interplanetary magnetic field is calculated numerically. We study the effects of the different aspects of particle sources on the solar surface, which include the source location, coverage of latitude and longitude, and spatial distribution of source particle intensity, on propagation of SEPs with both parallel and perpendicular diffusion. We compute the particle flux and anisotropy profiles at different observation locations in the heliosphere. From our calculations, we find that the observation location relative to the latitudinal and longitudinal coverage of particle source has the strongest effects on particle flux and anisotropy profiles observed by a spacecraft. When a spacecraft is directly connected to the solar sources by the interplanetary magnetic field lines, the observed particle fluxes are larger than when the spacecraft is not directly connected. This paper focuses on the situations when a spacecraft is not connected to the particle sources on the solar surface. We find that when the magnetic footpoint of the spacecraft is farther away from the source, the observed particle flux is smaller and its onset and maximum intensity occur later. When the particle source covers a larger range of latitude and longitude, the observed particle flux is larger and appears earlier. There is east-west azimuthal asymmetry in SEP profiles even when the source distribution is east-west symmetric. However, the detail of particle spatial distribution inside the source does not affect the profile of the SEP flux very much. When the magnetic footpoint of the spacecraft is significantly far away from the particle source, the anisotropy of particles in the early stage of an SEP event points toward the Sun, which indicates that the first arriving particles come from outside of the observer through perpendicular diffusion at large radial distances.

He, H.-Q.; Qin, G. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, M., E-mail: hqhe@spaceweather.ac.cn, E-mail: gqin@spaceweather.ac.cn, E-mail: mzhang@fit.edu [Department of Physics and Space Science, Florida Institute of Technology, Melbourne, FL 32901 (United States)

2011-06-20

179

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

NASA Astrophysics Data System (ADS)

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

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

1994-04-01

180

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

181

Magnetic fields on the sun and the north-south component of transient variations of the interplanetary magnetic field at 1 AU  

NASA Technical Reports Server (NTRS)

In order to study the relationship between solar magnetic fields and the transient variations of the north-south component B(Z) of the interplanetary magnetic field (IMF) at 1 AU, flares from unusual north-south oriented active regions, large IMF B(Z) events, and large flares with comprehensive flare index higher than 12 were collected. The associated IMF B(Z) changes or the magnetic field of the initiating flares are investigated. For those cases where an association between a transient B(Z) variation and an initiating flare is plausible, it is found that, for a given flare field, the orientation of the corresponding transient variation of B(Z) may be in agreement with the flare field, opposite to it, or more often, fluctuating in both magnitude and direction. Conversely, an IMF B(Z) event may originate in a flare field in the same magnetic orientation, opposite to it, or in the east-west orientation.

Tang, F.; Akasofu, S.-I.; Smith, E.; Tsurutani, B.

1985-01-01

182

On the Relationship of the Energy Spectrum Indexes of the 11Year Variation of Galactic Cosmic Rays and the Interplanetary Magnetic Field Strength Fluctuations  

Microsoft Academic Search

Data of neutron super monitors and interplanetary magnetic field (IMF) have been used to find a relationship between the temporal changes of galactic cosmic rays (GCR) isotropic intensity variations energy spectrum index gamma (delta D\\/D(R) ? R-gamma , where R is the rigidity of GCR particles) and the exponent ( of the power spectral density (PSD) of the IMF's strength

M. V. Alania; K. Iskra; R. Modzelewska; M. Siluszyk

2003-01-01

183

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

184

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

SciTech Connect

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 (which is in the same direction as the IMF B{sub y}) is also seen. The authors suggest that for a positive IMF B{sub y}, the magnetopause is open only in the north dawn and south dusk quadrants of the magnetotail. The continuity of magnetic field across the open boundary then requires that a B{sub y} component be present in the magnetosphere in these quadrants but not in the other two quadrants. They present a model of the magnetospheric convection that postulates cross-tail flows in the mantle/lobe system and the plasma sheet. They suggest that shear flows between the northern and southern halves of the plasma sheet generate a B{sub y} component on the closed magnetic field lines. The model is consistent with the two cell ionospheric convection models constructed from electric field observations by Heppner and Maynard. Results from global MHD simulations confirm the main features of the proposed model. 34 refs., 13 fig.

Khurana, K.K.; Walker, R.J. [Univ. of California, Los Angeles, CA (United States)] [Univ. of California, Los Angeles, CA (United States); Ogino, Tatsuki [Nagoya Univ., Toyokawa (Japan)] [Nagoya Univ., Toyokawa (Japan)

1996-03-01

185

Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail: The 20012005 Cluster  

E-print Network

Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail (2010), Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail; published 14 August 2010. [1] Magnetic reconnection plays a key role in the circulation of plasma through

California at Berkeley, University of

186

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

187

Complex interplanetary ejecta and their association to multi-step magnetic storm main phase development  

Microsoft Academic Search

It was observed long time ago that, although the classical definition of magnetic storms is quite simple, a magnetic storm could evolves in a much more complex way. It was recently shown that the main phase of intense magnetic storms usually develops in two or more steps. It occurs as a consequence of several energy injections during the main phase

L. E. Vieira; W. D. Gonzalez; A. L. Clua de Gonzalez; A. dal Lago; E. Echer; F. L. Guarnieri; L. Balmaceda; N. J. Schuch

2003-01-01

188

Parameterization of the Defense Meterological Satellite Program ionospheric electrostatic potentials by the interplanetary magnetic field strength and direction  

NASA Astrophysics Data System (ADS)

In this study we applied a linear regression analysis technique to the interplanetary magnetic field (IMF) data and the ionospheric electrostatic potentials obtained from thermal ion drift measurements made by the Defense Meterological Satellite Program (DMSP) satellites F8 and F10-F13 in 1993-1996. The ionospheric potentials are binned by every 1° of the corrected geomagnetic latitude and 0.5 hour of magnetic local time over both the northern and southern polar regions. The regression analyses are applied to the DMSP data in each bin in a similar way to what was done with the ground magnetometer data in the IZMIRAN Electrodynamic Model (IZMEM). This allowed us to parameterize the DMSP ionospheric potentials by the IMF strength and direction, as well as to recalibrate the IZMEM model against experimental satellite data. From the analysis it is calculated that the ``background'' cross-polar potential drop estimated from DMSP data equals ~33 kV if IMF~0. The calculated ionospheric potential responses to changes in the southward and northward IMF components are 11.5 kV/nT and -5.0 kV/nT, respectively.

Papitashvili, V. O.; Rich, F. J.; Heinemann, M. A.; Hairston, M. R.

1999-01-01

189

Power-spectrum dynamics of the interplanetary magnetic field behind the front of the shock wave of February 1-2, 1982  

Microsoft Academic Search

Venera 13 and 15 data are used to study the magnetic structure of the interplanetary stream behind the shock wave of February 1-2, 1982 as well as the power-spectrum dynamics of the IMF corresponding to this structure at frequencies ranging from 0.0001 to 0.1 Hz. It is shown that the level of MHD turbulence (the slope of the fluctuation spectrum

E. I. Morozova; L. V. Evdokimova; E. Iu. Budnik; E. G. Eroshenko; I. P. Besrodnykh

1986-01-01

190

Solar Energetic Particle Events in the 23rd Solar Cycle: Interplanetary Magnetic Field Configuration and Statistical Relationship with Flares and CMEs  

E-print Network

We study the influence of the large-scale interplanetary magnetic field configuration on the solar energetic particles (SEPs) as detected at different satellites near Earth and on the correlation of their peak intensities with the parent solar activity. We selected SEP events associated with X and M-class flares at western longitudes, in order to ensure good magnetic connection to Earth. These events were classified into two categories according to the global interplanetary magnetic field (IMF) configuration present during the SEP propagation to 1AU: standard solar wind or interplanetary coronal mass ejections (ICMEs). Our analysis shows that around 20% of all particle events are detected when the spacecraft is immersed in an ICME. The correlation of the peak particle intensity with the projected speed of the SEP-associated coronal mass ejection is similar in the two IMF categories of proton and electron events, $\\approx 0.6$. The SEP events within ICMEs show stronger correlation between the peak proton inten...

Miteva, R; Malandraki, O; Dorrian, G

2014-01-01

191

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

192

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

193

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

194

Electron heat flux dropouts in the solar wind: evidence for interplanetary magnetic field reconnection  

Microsoft Academic Search

Electron heat flux dropout events have been observed in the solar wind using the ISEE 3 plasma electron data set. These events manifest themselves as dropouts of the solar wind halo electrons which are normally found streaming outward along the local magnetic field. These dropouts leave nearly isotropic distributions of solar wind halo electrons, and consequently, the heat flux in

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

1989-01-01

195

Manifestation of the Jupiter's influence on the interplanetary magnetic field and cosmic rays  

Microsoft Academic Search

Based on extended set of observational data we study some peculiarities in the distribution of Jovian relativistic electrons along the Earth s orbit It is shown that the maximum in electron intensity appears 243 day after the Jupiter-Earth opposition This corresponds to the magnetic field line of IMF which passes throughout the Jupiter and Earth simultaneously It seems that Jupiter

V. Timofeev; L. Miroshnichenko; S. Samsonov; N. Skryabin

2006-01-01

196

Synoptic maps of polar caps for stable interplanetary magnetic field intervals during January 1992 geospace environment modeling campaign  

NASA Astrophysics Data System (ADS)

Observations from January 27-28, 1992, when four polar-orbiting DMSP satellites were in operation, are used to construct synoptic maps of convective flows and particle regions within the polar ionosphere. We chose periods of relative steady interplanetary magnetic field (IMF) and use data from multiple satellite passes during each period to obtain unprecedented two-dimensional coverage. For strongly negative IMF By, convection patterns are similar to those that have been previously obtained but also show significant. IMF Bz effects. For Bz>>|By|, we see strong sunward flow near the pole, but antisunward convection on open field lines at lower latitudes on the nightside. The particle observations reveal the two-dimensional structure of the cusp/mantle region and the existence of a strong polar arc within the circular convection cell that has a negative electric field divergence on open field lines. The particle observations also readily identify the magnetic separatrix when a satellite crosses the inner edge of the cusp or the boundary between the plasma sheet and polar rain. However, on the morningside and often on the afternoonside, we find a distinct and well-defined region of soft-electron and magnetosheath-like ion precipitation [(the ``soft- electron zone'' (SEZ)] lying between the plasma sheet and the region of polar rain. Separatrix identification is uncertain at local times where the SEZ is present; however, it appears that large portions of the SEZ are on open field lines. Dawn-dusk displacements of the open field line regions in the two polar caps are seen that are consistent with IMF By effects. Additionally, the dayside separatrix is observed to be further poleward for positive than for negative IMF Bz, whereas Bz is not observed to have a significant effect on the location of the nightside separatrix. Also, we consistently find larger cross polar-cap potential drops in the southern hemisphere than in the northern hemisphere. This suggests that there are significant (tens of kV) magnetic-field-aligned potential drops along high-altitude regions of open field lines where the magnetic field is weak and particle motion strongly violates the guiding center approximation.

Lyons, L. R.; Lu, G.; de la Beaujardière, O.; Rich, F. J.

1996-12-01

197

An advanced magnetometric system for precise measurements of the interplanetary and near earth magnetic fields  

Microsoft Academic Search

A three-component flux-gate magnetometric system is described for precise magnetic field investigations in a wide dynamic range with a high resolution. To allow inflight measurements of the spacecraft stray field, the system contains two flux-gate sensor triads, located 5 and 7 m from the spacecraft body. The outer triad is supplied with a double flipper system, allowing zero-offset determination of

I. S. Arshinkov; A. Z. Bochev; N. S. Abadzhiev; E. G. Zakharieva; K. I. Arshinkova

1985-01-01

198

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

199

Spectral signatures of jumps and turbulence in interplanetary speed and magnetic field data  

NASA Technical Reports Server (NTRS)

It is shown here that, consistent with a suggestion of Burlaga and Mish (1987), the f exp -2 spectra in the magnitudes of the magnetic and velocity fields in the solar wind result from jumps due to various rapid changes in the time series for these quantities. If these jumps are removed from the data, the spectra of the resulting 'difference' time series have the f exp -5/3 form. It is concluded that f exp -2 spectra in these magnitudes arise from phase coherent structures that can be distinguished clearly from incoherent turbulent fluctuations.

Roberts, D. A.; Goldstein, M. L.

1987-01-01

200

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

201

Hale cycle effects in cosmic ray east-west anisotropy and interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

We have reanalyzed diurnal anisotropy data obtained with the shielded ion chamber (IC) at Cheltenham/Fredericksburg and the neutron monitor (NM) at Swarthmore/Newark. IC data are for the 1936-1977 period and NM data are for the 1965-1988 period. We have corrected IC data for the diurnal temperature effect. Application of this correction results in a better agreement between IC and other data sets, thereby making it possible to study the long-term changes in the diurnal anisotropy using IC data. The behavior of the annual mean east-west anisotropy is studied for 53 years of observations. The period encompasses more than two solar magnetic (Hale) cycles. Its amplitude undergoes the expected 11 and 22 year variations, with the largest changes occurring near solar activity minima. Moreover, the data indicate the presence of the subsidiary maxima for the entire 53-year period, following the solar polar field reversals, during the declining phases of activity cycles when high-speed solar wind streams are present in the heliosphere. The data suggest that the amplitude of the subsidiary maximum is large when the solar polar magnetic field points toward the sun in the Northern Hemisphere, and radial anisotropy is absent.

Ahluwalia, H. S.

1993-01-01

202

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

203

SOURCE REGIONS OF THE INTERPLANETARY MAGNETIC FIELD AND VARIABILITY IN HEAVY-ION ELEMENTAL COMPOSITION IN GRADUAL SOLAR ENERGETIC PARTICLE EVENTS  

SciTech Connect

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. However, 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 potential-field source-surface 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 a correlation between SEP composition (as measured by Wind and Advanced Composition Explorer at ?2-30 MeV nucleon{sup –1}) and characteristics of the identified IMF source regions. The study is based on 24 SEP events, identified as a statistically significant increase in ?20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly emergent solar magnetic flux and CMEs was lower than in solar-maximum years, and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF source, with the largest enhancements occurring when the footpoint field is strong due to the nearby presence of an active region (AR). 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. Such results lead us to suggest that magnetic reconnection in footpoint regions near ARs 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; Wang, Yi-Ming [Space Science Division, Naval Research Laboratory, Code 7680, Washington, DC 20375 (United States); Tylka, Allan J. [NASA Goddard Space Flight Center, Code 672, Greenbelt, MD 20771 (United States); Ng, Chee K. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Dietrich, William F., E-mail: yko@ssd5.nrl.navy.mil [Praxis, Inc., Alexandria, VA 22303 (United States)

2013-10-20

204

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

205

Energetic solar particles in the interplanetary medium.  

NASA Technical Reports Server (NTRS)

Models which describe the diffusion of energetic solar particles in the interplanetary medium are reviewed. Most attention is paid to the case of impulsive emission from solar flares, taking into account the effects of the interplanetary magnetic field, diffusion near the sun, convection, and energy losses associated with the expansion of the solar wind. The case of continuous emission is also considered briefly.

Axford, W. I.

1972-01-01

206

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

207

Qualitative study of the reconnection between the Earth's magnetic field and an interplanetary field of arbitrary orientation  

Microsoft Academic Search

S>To the present date only the reconnection process for exac ; antiparallel fields has been discussed in detail. In magnetospheric terms this ; restricts us to the consideration only of southward interplanetary fields. The ; qualitative study presented shows how reconnection takes place between ; arbitrarily oriented fields in infinite and finite geometries. The process may ; best be thought

S. W. H. Cowley

1973-01-01

208

Formation of polar cap patches associated with north-to-south transitions of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

On January 15, 1991, the Sondrestrom incoherent scatter radar probed the midday high-latitude ionosphere to gather evidence for the formation and entry of polar cap patches. During the experiment the interplanetary magnetic field (IMF) Bz was positive and steady for few hours until 1548 UT when a short negative excursion of Bz occurred. Prior to the Bz excursion, and when this parameter was directed northward, the Sondrestrom radar detected a quasi-stationary density feature situated near the poleward boundary of the oval. Convergent electric fields and slightly elevated Te values were seen accompanying the F region density feature. A numerical model of the high-latitude ionosphere that uses a steady north Bz Heppner and Maynard convection pattern suggests that under these IMF conditions a tongue of ionization (TOI) can be formed near the midday sector, but it is confined to the poleward boundary of the auroral oval. It does not traverse into the polar cap. This simulated Bz northward TOI resembles the density feature seen in the radar data prior to the Bz negative excursion. When the Bz value was oriented southward, the radar detected the density feature moving poleward and then disappearing to the north of the radar field of view. At this time of Bz negative the radar data also displayed elevated Ti values and a new pattern of line-of-sight velocities. Nearly 34 min after the density feature departed from the field of view of the Sondrestrom radar, the Qaanaaq digisonde measured a factor of 2 increase in the f0F2 values. Similar enhancements are typically attributed to the passage of a patch. We also conducted a numerical simulation of the transit of the density feature from its initial location near the polar cap boundary up to its passage through the Qaanaaq station. The time that the density feature reaches Qaanaaq in our simulations is in good agreement with the actual time that the enhanced patch-like number density was observed at Qaanaaq. The Bz switching mechanism does not dispute the validity of other patch formation mechanisms; it merely suggests that a Bz northward TOI can end up as a polar cap patch if a timely reversal of Bz occurs.

Valladares, C. E.; Decker, D. T.; Sheehan, R.; Anderson, D. N.; Bullett, T.; Reinisch, B. W.

1998-07-01

209

Microstructure of the interplanetary medium  

NASA Technical Reports Server (NTRS)

High time resolution measurements of the interplanetary magnetic field and plasma reveal a complex microstructure which includes hydromagnetic wave and discontinuities. The identification of hydromagnetic waves and discontinuities, their statistical properties, their relation to large-scale structure, and their relative contribution to power spectra are discussed.

Burlaga, L. F.

1972-01-01

210

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

211

Observations of interplanetary shocks - Recent progress  

NASA Technical Reports Server (NTRS)

Attention is given to interplanetary shock observations conducted since 1978, with emphasis on shocks associated with such solar transient phenomena as coronal transients and eruptive prominences, as well as with flares. A correlation between shocks and Storm Sudden Commencements is found to persist into the recent maximum, and shocks associated with disappearing filaments and coronal transients rather than with flares have been identified. Preliminary results on the thickness of interplanetary shocks have been obtained, and several quasi-parallel shocks have been identified which propagate along, rather than across, the magnetic field. The plasma drivers that accompany interplanetary shocks exhibit distinctive features in electric, ion and magnetic field data.

Smith, E. J.

1983-01-01

212

Signal injection and averaging for position estimation of Permanent-Magnet Synchronous Motors  

E-print Network

Sensorless control of Permanent-Magnet Synchronous Motors at low velocity remains a challenging task. A now well-established method consists in injecting a high-frequency signal and use the rotor saliency, both geometric and magnetic-saturation induced. This paper proposes a clear and original analysis based on second-order averaging of how to recover the position information from signal injection; this analysis blends well with a general model of magnetic saturation. It also experimentally demonstrates the relevance for position estimation of a simple parametric saturation model recently introduced by the authors.

Jebai, Al Kassem; Martin, Philippe; Rouchon, Pierre

2012-01-01

213

Fine-scale characteristics of interplanetary sector boundaries  

Microsoft Academic Search

This investigation has studied the structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions during the time interval from December 1974 to April 1975. A sector transition region is the region of variable magnetic field magnitude and direction observed in or near the ecliptic plane between magnetic sectors in the interplanetary magnetic field (IMF). Such

K. W. Behannon; F. M. Neubauer; H. Barnstorf

1981-01-01

214

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

215

Survey of interplanetary shock characteristics  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

216

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

217

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

NASA Astrophysics Data System (ADS)

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

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

1985-05-01

218

Erratum to "Solar Sources and Geospace Consequences of Interplanetary Magnetic Clouds Observed During Solar Cycle 23-Paper 1" [J. Atmos. Sol.-Terr. Phys. 70(2-4) (2008) 245-253  

NASA Technical Reports Server (NTRS)

One of the figures (Fig. 4) in "Solar sources and geospace consequences of interplanetary magnetic Clouds observed during solar cycle 23 -- Paper 1" by Gopalswamy et al. (2008, JASTP, Vol. 70, Issues 2-4, February 2008, pp. 245-253) is incorrect because of a software error in t he routine that was used to make the plot. The source positions of various magnetic cloud (MC) types are therefore not plotted correctly.

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

2009-01-01

219

Interplanetary Disturbances Affecting Space Weather  

NASA Astrophysics Data System (ADS)

The Sun somehow accelerates the solar wind, an incessant stream of plasma originating in coronal holes and some, as yet unidentified, regions. Occasionally, coronal, and possibly sub-photospheric structures, conspire to energize a spectacular eruption from the Sun which we call a coronal mass ejection (CME). These can leave the Sun at very high speeds and travel through the interplanetary medium, resulting in a large-scale disturbance of the ambient background plasma. These interplanetary CMEs (ICMEs) can drive shocks which in turn accelerate particles, but also have a distinct intrinsic magnetic structure which is capable of disturbing the Earth's magnetic field and causing significant geomagnetic effects. They also affect other planets, so they can and do contribute to space weather throughout the heliosphere. This paper presents a historical review of early space weather studies, a modern-day example, and discusses space weather throughout the heliosphere.

Wimmer-Schweingruber, Robert F.

2014-01-01

220

The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.

Fedder, J. A.; Lyon, J. G.

1995-01-01

221

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

222

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

NASA Astrophysics Data System (ADS)

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

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

223

INTERPLANETARY ASPECTS OF CMES David F. Webb  

E-print Network

and magnetic elds into the heliosphere causing major geomagnetic storms and interplanetary shocks, a key source of solar ener- getic particles. Much of the plasma observed in a CME is entrained on expanding magnetic eld coronagraphs have provided the most recent white lightobservations ofCMEs, with coverage now throughthe rst

Webb, David F.

224

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

225

Velocity measurement of the interplanetary hydrogen  

NASA Astrophysics Data System (ADS)

We are proposing to use HST/STIS over a single orbit to make Lyman-alpha observations of the interplanetary hydrogen during the March-April period of this year {2012}. This special request is driven by a recent reanalysis of HST data {Vincent et al. 2011, published after the last call for proposals}.The heliospheric interface results from the interaction of the solar wind and the interstellar medium {ISM}. Within the heliosphere, the interplanetary hydrogen {IPH} flows at an average speed of about 23 km/sec, carrying the signature of the ISM and the heliospheric interface. The IPH has been observed for decades through the backscattering of solar Lyman-alpha photons and solar cycle 23 provided the first partial temporal map of the IPH velocity. It is now well established that the IPH velocity depends on solar activity. Moreover some analyses suggested that it may be also affected by the obliquity of the interstellar magnetic field, yielding a change of 1-2 km/sec.However a combination of the uncertainty of some measurements {e.g. GHRS} and the clustering of others near points on the cycle make it difficult to identify an unambiguous trend. Only one limited set is able to show a cycle dependence, but these represent an annual average and do not match the existing models. The best approach to address these issues is a new set of yearly spectroscopic measurements for at least a half solar cycle. Since we are currently just leaving a solar maximum, it is essential to start immediately in order to have an adequate baseline for temporal measurements.

Vincent, Frederic

2011-10-01

226

Implementing the Interplanetary Internet  

E-print Network

Implementing the Interplanetary Internet differing approaches Lloyd Wood Surrey Space Centre guest lecture Tuesday 17 February 2009. #12;22Interplanetary Internet ­ Lloyd Wood How did it all begin?How did Internet ­ Lloyd Wood VintVintVintVint sets up an Internet Society SIGsets up an Internet Society SIGsets

Wood, Lloyd

227

Power Spectrum Anisotropy for Interplanetary Fluctuations Inside 1 AU  

Microsoft Academic Search

The mean interplanetary magnetic field (IMF) is thought to provide a direction that breaks the isotropic symmetry of turbulence by providing a preferred direction. With this hypothesis several hybrid model for interplanetary turbulence have been proposed where field-aligned wave vectors are coupled to perpendicular wave vectors and the resultant system evolves as a coupled two-component turbulent geometry. However, asymmetry can

J. A. Tessein; C. W. Smith; W. H. Matthaeus; M. A. Forman; J. Borovsky

2008-01-01

228

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

229

The 3-dimensional radio mapping experiment /SBH/ on ISEE-C. [interplanetary magnetic field structure for solar wind flow studies using type 3 bursts  

NASA Technical Reports Server (NTRS)

The SBH experiment on ISEE-C will provide maps of the large scale structure of the interplanetary magnetic field from ten solar radii altitude to the earth orbit, in and out of the ecliptic. The SBH instrument will track type III solar radio bursts at 24 frequencies in the range 30 kHz-2 MHz thus providing the positions of 24 points along the line of force which guides the electrons producing the radio radiation. The antennas are two dipoles: one (90 m long) in the spin plane, the other (15 m long) along the spin axis. The receiver was designed for high sensitivity (0.3 microV in 3 kHz BW), high intermodulation rejection (80 dB/1 microV input for order 2 products), large dynamic range (70 dB), high selectivity (-30-dB response 6.5 kHz away from the center frequency of 10.7 MHz for the 3 kHz BW channels), and high reliability (expected orbital life: 3 years).

Knoll, R.; Epstein, G.; Hoang, S.; Huntzinger, G.; Steinberg, J. L.; Fainberg, J.; Grena, F.; Stone, R. G.; Mosier, S. R.

1978-01-01

230

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

231

Influence of interplanetary solar wind sector polarity on the ionosphere  

NASA Astrophysics Data System (ADS)

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

liu, jing

2014-05-01

232

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

233

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 ?eld ?uctuations 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

234

Wave properties near the subsolar magnetopause - Pc 3-4 energy coupling for northward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

Strong slow mode waves in the Pc 3-4 frequency range are found in the magnetosheath close to the magnetopause. We have studied these waves at one of the ISEE subsolar magnetopause crossings using the magnetic field, electric field, and plasma measurements. We use the pressure balance at the magnetopause to calibrate the Fast Plasma Experiment data versus the magnetometer data. When we perform such a calibration and renormalization, we find that the slow mode structures are not in pressure balance and small scale fluctuations in the total pressure still remain in the Pc 3-4 range. Energy in the total pressure fluctuations can be transmitted through the magnetopause by boundary motions. The Poynting flux calculated from the electric and magnetic field measurements suggests that a net Poynting flux is transmitted into the magnetopause. The two independent measurements show a similar energy transmission coefficient. The transmitted energy flux is about 18 percent of the magnetic energy flux of the waves in the magnetosheath. Part of this transmitted energy is lost in the sheath transition layer before it enters the closed field line region. The waves reaching the boundary layer decay rapidly. Little wave power is transmitted into the magnetosphere.

Song, P.; Russell, C. T.; Strangeway, R. J.; Wygant, J. R.; Cattell, C. A.; Fitzenreiter, R. J.; Anderson, R. R.

1993-01-01

235

An MHD simulation of the effects of the interplanetary magnetic field By component on the interaction of the solar wind with the earth's magnetosphere during southward interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

The interaction between the solar wind and the earth's magnetosphere has been studied by using a time-dependent three-dimensional MHD model in which the IMF pointed in several directions between dawnward and southward. When the IMF is dawnward, the dayside cusp and the tail lobes shift toward the morningside in the northern magnetosphere. The plasma sheet rotates toward the north on the dawnside of the tail and toward the south on the duskside. For an increasing southward IMF component, the plasma sheet becomes thinner and subsequently wavy because of patchy or localized tail reconnection. At the same time, the tail field-aligned currents have a filamentary layered structure. When projected onto the northern polar cap, the filamentary field-aligned currents are located in the same area as the region 1 currents, with a pattern similar to that associated with auroral surges. Magnetic reconnection also occurs on the dayside magnetopause for southward IMF.

Ogino, T.; Walker, R. J.; Ashour-Abdalla, M.; Dawson, J. M.

1986-01-01

236

Challenges in Interplanetary MANETs  

Microsoft Academic Search

Very soon, the need for networks that span inter-planetary distances, or Inter-Planetary Area Networks (IPANs), may be reality. These networks pose unique challenges on end-to-end communications with QoS, reliable information exchange under frequent topology changes, and rapid service provisioning. Mobile Ad hoc NETworks (MANETs) are very useful in such situations and are currently being researched for their autonomous characteristics and

Chien-Chung Shen; Sundaram Rajagopalan

2002-01-01

237

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

238

The solar and interplanetary causes of the recent minimum in geomagnetic activity (MGA23): a combination of midlatitude small coronal holes, low IMF BZ variances, low solar wind speeds and low solar magnetic fields  

NASA Astrophysics Data System (ADS)

Minima in geomagnetic activity (MGA) at Earth at the ends of SC23 and SC22 have been identified. The two MGAs (called MGA23 and MGA22, respectively) were present in 2009 and 1997, delayed from the sunspot number minima in 2008 and 1996 by ~1/2-1 years. Part of the solar and interplanetary causes of the MGAs were exceptionally low solar (and thus low interplanetary) magnetic fields. Another important factor in MGA23 was the disappearance of equatorial and low latitude coronal holes and the appearance of midlatitude coronal holes. The location of the holes relative to the ecliptic plane led to low solar wind speeds and low IMF (Bz) variances (?Bz2) and normalized variances (?Bz2/B02) at Earth, with concomitant reduced solar wind-magnetospheric energy coupling. One result was the lowest ap indices in the history of ap recording. The results presented here are used to comment on the possible solar and interplanetary causes of the low geomagnetic activity that occurred during the Maunder Minimum.

Tsurutani, B. T.; Echer, E.; Gonzalez, W. D.

2011-05-01

239

Study of Travelling Interplanetary Phenomena Report  

NASA Astrophysics Data System (ADS)

Scientific progress on the topic of energy, mass, and momentum transport from the Sun into the heliosphere is contingent upon interdisciplinary and international cooperative efforts on the part of many workers. Summarized here is a report of some highlights of research carried out during the SMY/SMA by the STIP (Study of Travelling Interplanetary Phenomena) Project that included solar and interplanetary scientists around the world. These highlights are concerned with coronal mass ejections from solar flares or erupting prominences (sometimes together); their large-scale consequences in interplanetary space (such as shocks and magnetic 'bubbles'); and energetic particles and their relationship to these large-scale structures. It is concluded that future progress is contingent upon similar international programs assisted by real-time (or near-real-time) warnings of solar activity by cooperating agencies along the lines experienced during the SMY/SMA.

Dryer, Murray

1987-09-01

240

A COMPARISON BETWEEN APRIL 1999 AND FEBRUARY 2000 SOLAR-TERRESTRIAL CONNECTION EVENTS: INTERPLANETARY ASPECTS  

E-print Network

in the complex ejecta event (3 hours) than for the magnetic cloud (5 hours) the complex ejecta storm was more fields than in magnetic clouds in order to cause intense storms, because the injection rate is higher (in: INTERPLANETARY ASPECTS Interplanetary parameters ­ Magnetic Cloud April 1999 E. Echer, M. Virgínia Alves, W. D

241

Super dual auroral radar network radar imaging of dayside high-latitude convection under northward interplanetary magnetic field: Toward resolving the distorted two-cell versus multicell controversy  

NASA Astrophysics Data System (ADS)

Data from the Kapuskasing and Saskatoon radars of the evolving Super Dual Auroral Radar Network (SuperDARN) HF radar network have been analyzed to study the two-dimensional structure and dynamics of dayside high-latitude ionospheric convection under northward interplanetary magnetic field (IMF) conditions. A period extending from 1600 to 2030 UT (~0900-1330 MLT) on January 10, 1994, was examined. During this interval, magnetic field data were available from the IMP 8 satellite and indicated moderately stable northward IMF conditions. For the first few hours of observation the By component of the IMF was positive, reasonably steady, and approximately twice the magnitude of Bz. During this interval, the high-latitude convection images obtained with the SuperDARN radars were very similar to the distorted two-cell convection maps for positive By as presented by Heppner and Maynard (1987). At ~1840 UT, a decrease in By in association with an increase in Bz, led to an extended period with By~Bz. During this second interval the convection patterns were highly variable and even chaotic. Finally, a sharp decrease in the By component at 1914 UT, probably in association with a rotational discontinuity in the solar wind, led to an extended period with By<

Greenwald, R. A.; Bristow, W. A.; Sofko, G. J.; Senior, C.; Cerisier, J.-C.; Szabo, A.

1995-10-01

242

Effect of size and shape dispersion on the averaged magnetic response of ensembles of semiconductor quantum rings  

NASA Astrophysics Data System (ADS)

In this paper a theoretical study was made of the conditional averages of the magnetization and magnetic susceptibility of dispersive ensembles of nano-objects with a very complex geometry—self-assembled wobbled semiconductor quantum rings. Using the multivariate statistics approach and previously proposed mapping method the impact of the dispersion of the ring geometry parameters on the static magnetic response of the ensembles has been investigated near the first Aharonov-Bohm oscillation. The description is suited to clarify the important question of which geometrical parameters’ dispersions are crucial for the formation and properties of the magnetic response of ensembles. We theoretically show that for the dispersive ensembles of InGaAs/GaAs capped wobbled quantum rings the actual value and temperature dependence of the differential magnetic susceptibility can be optimized by an appropriate control of the conditional parameters of the ensembles. The ring rim radius variations play a crucial role in this dependence. We have managed to simulate in detail the temperature behavior of the meaningful averages of the magnetization and positive peak of the differential magnetic susceptibility for ensembles of the rings known from the experiment. The simulated temperature dependence, position, and magnitude of the positive peak in the differential magnetic susceptibility are in a good agreement with the experimental observations.

Thu, L. M.; Chiu, W. T.; Voskoboynikov, O.

2012-05-01

243

Long-duration penetration of the interplanetary electric field to the low-latitude ionosphere during the main phase of magnetic storms  

Microsoft Academic Search

It is well known that the interplanetary electric field can penetrate to the low-latitude ionosphere. It is generally believed that the penetration of electric fields can last only for ?30 min because of the shielding effect in the ring current. In this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in

Chao-Song Huang; John C. Foster; Michael C. Kelley

2005-01-01

244

Interplanetary magnetic field structure and solar wind parameters as inferred from solar magnetic field observations and by using a numerical 2-D MHD model  

Microsoft Academic Search

An attempt is made to infer parameters of the solar corona and the solar wind by means of a numerical, self-consistent MHD simulation. Boundary conditions for the magnetic field are given from the observations of the large-scale magnetic field at the Sun. A two-region, planar (the ecliptic plane is assumed) model for the solar wind flow is considered. Region I

A. V. Usmanov

1993-01-01

245

Interplanetary Field Enhancements: Further evidence of an interaction between the solar wind and interplanetary dust  

Microsoft Academic Search

Interplanetary field enhancements (IFEs) are highly unusual, sharply-peaked increases in the magnitude of the heliospheric magnetic field. They have been found in the solar wind over a wide range of heliocentric distances. Spatial clustering of IFEs detected near Venus led to a link being found between some IFEs and dust particles co-orbiting with asteroid 2201 Oljato. This link suggested that

G. H. Jones; E. J. Smith; A. Balogh

2003-01-01

246

In-situ Measurements of Interplanetary and Interstellar Dust  

NASA Astrophysics Data System (ADS)

Dust is finely dispersed solid material in interplanetary space. It derives from a number of sources: larger meteoroids, comets, asteroids, the planets, and satellites, and there is interstellar dust sweeping through the solar system. These dust particles range in size from assemblages of a few molecules to tenth millimetre-sized grains. Dust particles absorb and scatter solar radiation and emit thermal radiation giving rise to Zodiacal light at visible and thermal emission at infrared wavelengths. Astronomical observations of both emissions provide information on the average properties of very large number of particles and their spatial distribution. Information on the physical and chemical properties and the orbital motion is obtained by direct methods. Direct methods include: (1) collection of dust particles (Fig. 1) on collectors on spacecraft returned to Earth and on airplanes in the stratosphere, (2) investigations of dust impacts craters on lunar samples and manmade impact plates returned from space, and (3) insitu measurements of individual particles by instruments on board satellites and space probes. Dust particles collected in the upper atmosphere provide the morphology and chemical and mineralogical composition of extraterrestrial particles of 5 to 50 microns in diameter but no information on the source of these particles is obtained. The NASA Stardust mission was the first space mission that returned dust from a comet. The study of impact craters on man-made and lunar surface samples exposed to space is used to characterize the flux of interplanetary micrometeoroids and their size distribution. Microcraters have been found ranging from 0.02 ?m to millimetres in diameter. In-situ detectors on board of satellites and spaceprobes for the measurement of interplanetary dust have been used in the ecliptic plane from inside Mercury's orbit to the Kuiper belt and in space above and below the solar poles. Penetration detectors have a detection threshold of ?10-13 g (approx. 1 ?m radius). The most sensitive and versatile dust detectors are impact ionization detectors. They provide not only the mass and velocity of the impacting particle but also their chemical composition and electrical charge. Two types of dust particles were found to dominate the dust flux in interplanetary space. Interplanetary micrometeoroids covering a wide mass range from 10-16 to 10-6 g are mostly recorded at ecliptic latitudes below = 30º. Interstellar grains with masses between 10-14 and 10-12 g have been positively identified from 0.3 AU near the ecliptic plane and at high ecliptic latitudes (Fig. 2). Interstellar grains move on hyperbolic trajectories through the planetary system and constitute the dominant dust flux in the outer solar system and at high ecliptic latitudes. The interstellar dust stream is strongly filtered by solar radiation pressure and modulated by the solar wind magnetic field. Interstellar particles with optical properties of astronomical silicates or organic refractory materials are consistent with the observed radiation pressure effects. References [1] Jessberger, E. K. et al. (2001) In: Interplanetary Dust (eds. S.F. Dermott, H. Fechtig, E. Grün, and B.A.S. Gustafson): 253-294, Springer, Heidelberg [1] Grün et al. (2001) In: Interplanetary Dust (eds. S.F. Dermott, H. Fechtig, E. Grün, and B.A.S. Gustafson): 295-346, Springer, Heidelberg

Grün, E.

2008-09-01

247

Effects of Interplanetary Transport on Derived Energetic Particle Source Strengths  

NASA Astrophysics Data System (ADS)

We study the transport of solar energetic particles (SEPs) in the inner heliosphere in order to relate observations made by an observer at 1 AU to the total energy content of particles at the source, assumed to be near the Sun. We use a numerical simulation that integrates the trajectories of a large number of individual particles moving in the interplanetary magnetic field. We model pitch-angle scattering and adiabatic cooling of energetic ions with energies from 50 keV/nucleon to 100 MeV/nucleon. Among other things, we determine the number of times that particles of a given energy cross 1 AU and the average energy loss that they suffer due to adiabatic deceleration in the solar wind. We use a number of different forms of the interplanetary spatial diffusion coefficient, a wide range of scattering mean-free paths, and consider a number of different ion species in order to generate a wide range of simulation results that can be applied to individual SEP events. Our results are used to estimate the total energy needed to accelerate particles for an event on 20 February 2002 based on observations made at 1 AU. We find that estimates of the source energy based on SEP measurements at 1 AU are relatively insensitive to mean free path and scattering scheme.

Chollet, E. E.; Giacalone, J.; Mewaldt, R. A.

2009-12-01

248

Effects of interplanetary transport on derived energetic particle source strengths  

NASA Astrophysics Data System (ADS)

We study the transport of solar energetic particles (SEPs) in the inner heliosphere in order to relate observations made by an observer at 1 AU to the number and total energy content of accelerated particles at the source, assumed to be near the Sun. We use a numerical simulation that integrates the trajectories of a large number of individual particles moving in the interplanetary magnetic field. We model pitch angle scattering and adiabatic cooling of energetic ions with energies from 50 keV nucleon-1 to 100 MeV nucleon-1. Among other things, we determine the number of times that particles of a given energy cross 1 AU and the average energy loss that they suffer because of adiabatic deceleration in the solar wind. We use a number of different forms of the interplanetary spatial diffusion coefficient and a wide range of scattering mean-free paths and consider a number of different ion species in order to generate a wide range of simulation results that can be applied to individual SEP events. We apply our simulation results to observations made at 1 AU of the 20 February 2002 solar energetic particle event, finding the original energy content of several species. We find that estimates of the source energy based on SEP measurements at 1 AU are relatively insensitive to the mean-free path and scattering scheme if adiabatic cooling and multiple crossings are taken into account.

Chollet, E. E.; Giacalone, J.; Mewaldt, R. A.

2010-06-01

249

Viscosity and inertia in cosmic-ray transport - Effects of an average magnetic field  

NASA Technical Reports Server (NTRS)

A generalized transport equation is introduced which describes the transport and propagation of cosmic rays in a magnetized, collisionless medium. The equation is valid if the cosmic-ray distribution function is nearly isotropic in momentum, if the ratio of fluid speed to fluid-flow particle speed is small, and if the ratio of collision time to time for change in the macroscopic flow is small. Five independent cosmic-ray viscosity coefficients are found, and the ralationship of this viscosity to particle orbits in a magnetic field is presented.

Williams, L. L.; Jokipii, J. R.

1991-01-01

250

The interplanetary mass ejections behaviour in the heliosphere  

E-print Network

We present here an overview of an important solar phenomenon with major implication for space weather and planetary life. The coronal mass ejections (CMEs) come from the Sun and expand in the heliosphere, becoming interplanetary coronal mass ejections (ICMEs). They represent huge clouds of plasma and magnetic fields that travel with velocities reaching even 2000 km/s and perturbing the planetary and interplanetary field. The magnetic clouds (MC) are a special class of ICMEs. We summarize some aspects as the ICMEs identification, propagation and track back to the Sun, where the solar source could be found. We notice here few known catalogs of the ICMEs and magnetic clouds.

Dumitrache, Cristiana

2014-01-01

251

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

252

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

253

Cosmic ray scintillations. II - General theory of interplanetary scintillations  

NASA Technical Reports Server (NTRS)

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

Owens, A. J.

1974-01-01

254

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

255

A correlative study of SSC's, interplanetary shocks, and solar activity  

NASA Technical Reports Server (NTRS)

A total of 93 SSC's were examined during the four year period from 1968 to 1971 at and near the peak of the solar activity cycle. Of the 93 SSC's 81 could be associated with solar activity, such as solar flares and radio bursts of Type II and Type IV. The mean propagation speeds of these flare-associated events ranged from 400 to 1000 km/sec with an average speed of 600-700 km/sec. Disturbances associated with 48 of the SSC's have been studied in detail using the corresponding interplanetary (IP) magnetic field, and plasma data when they were available. It was found that 41 of the 48 disturbances corresponded to IP shock waves, and the remaining seven events were tangential discontinuities. Thirty percent of the IP shocks had thick structure (i.e. the magnetic field jump across the shock occurred over a distance much greater than 50 proton Larmor radii). Also given is a statistical study of the gross geometry of a typical or average shock surface based on multiple spacecraft sightings and their relative orientation with respect to the solar flare. It is suggested that a typical shock front propagating out from the sun at l AU has a radius of curvature on the order of l AU. Also given are some general properties of oblique IP flare-shocks.

Chao, J. K.; Lepping, R. P.

1973-01-01

256

Dust in Interplanetary Space and in the Local Galactic Environment  

NASA Astrophysics Data System (ADS)

The solar system is a natural laboratory, accessible by a variety of methods, for studying the astrophysics of dust. Astronomical measurements mostly at visible and infrared wavelengths, yield the large-scale distribution of dust and its average composition. Examining natural surfaces deployed to the space environment, and assessing those surfaces' micro-crater distributions, reveals the size distribution of dust. Meteor observations and their corresponding measurements provide orbital information of dust grains and their genetic interrelation to the larger bodies in our solar system: comets and asteroids. From analyses of meteorites and interplanetary dust particles collected in the stratosphere, we have a comprehensive understanding of the isotopic, elemental, and mineralogical composition of this primordial material. Finally, in situ dust analysis via dust detectors located in interplanetary space, the most versatile method, have been providing data to determine the dust particles' mass, speed, trajectory, and chemical composition. An assortment of dust exhibiting a variety of dynamical processes has been identified in interplanetary space. In Jupiter's proximity, intense streams have been observed of nanometer-sized ash particles, which are emitted from the volcanoes of Jupiter's moon Io. These particles are accelerated by the powerful Jovian magnetic field to speeds of several 100 km/s, and are propelled further into interplanetary and interstellar space by the solar wind magnetic field. In interplanetary space, concentrations of collisional debris in the asteroid belt have been identified by infrared observations. The Poynting-Robertson effect drags these particles in towards the Earth and the Sun, where they sublimate. If the giant planets did not block their inward drift, a similar fate is expected for the dust assortment that is generated by collisions in the Kuiper belt. Another dust population is the mostly sub-micron-sized dust from comets, released while the comets traverse the inner parts of our solar system. These comet particles are shed from the comet's coma and consequently, quickly driven out of the solar system by radiation pressure forces. Larger particles form trails along the orbit of the parent comet, which result in a meteor storm as the Earth crosses the trail. Furthermore, the dust of comet trails can disperse via planetary perturbations into the background zodiacal cloud. Last, but not least, an important dust population identified by in situ dust instruments is the micron-sized interstellar grains flowing through the planetary system with the interstellar gas flow being part of the local interstellar cloud. This cloud is at the edge of the local bubble of hot tenuous gas which was excavated by supernova explosions in the near-by Scorpius-Centaurus and Orion Associations. These dust populations are the target of future dust observatory missions in space. Such a dust observatory satellite carries a dust telescope, which is a combination of a dust trajectory sensor together with an analyzer for the particles' chemical composition. With accurate dust trajectory measurements, we can identify its place of origin: for example, comets, asteroids, or interstellar space. From the particles' bulk properties and their chemical composition, we can infer properties of the environments out of which the particles were formed, and in which they were subsequently altered.

Grün, E.; Dikarev, V.; Frisch, P. C.; Graps, A.; Kempf, S.; Krüger, H.; Landgraf, M.; Moragas-Klostermeyer, G.; Srama, R.

2004-05-01

257

KINETIC PROPERTIES OF INTERPLANETARY MATTER  

Microsoft Academic Search

Estimates of the kinetic and transport properties of the interplanetary ; medium are reviewed. It is pointed out that the effective mean free paths of ; interplanetary ions and electrons are effectively small compared to the scale of ; the system, either because of Coulomb collisions or dynamical instability of the ; gas. Numerical expressions are given for the mean

E Parker

1962-01-01

258

An interplanetary scintillation activity index  

Microsoft Academic Search

Using interplanetary scintillation (IPS) data obtained from the Cambridge 81.5 MHz array, an activity index is developed in which it is possible to identify (1) discrete structures, most likely relating to transient density enhancements, and (2) periodic activity, relating to corotating interplanetary structure. Significant, yet weak correlations are found between the index and geomagnetic activity. Results suggest that the pursuit

R. A. Harrison; M. A. Hapgood; V. Moore; E. A. Lucek

1992-01-01

259

Radio tracking of solar energetic particles through interplanetary space.  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

260

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

261

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

262

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

263

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

264

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

NASA Technical Reports Server (NTRS)

Plasma fluid parameters calculated from solar wind and magnetic field data to determine the characteristic properties of driver gas following a select subset of interplanetary shocks were studied. 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. While helium enhancements were present downstream of the shock in all 9 of these events, only about half of them contained simultaneous changes in the two quantities. 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, by a small decrease in the variance of the bulk velocity, and by an increase in the ratio of parallel to perpendicular temperature. The cold driver gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

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

1983-01-01

265

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

NASA Technical Reports Server (NTRS)

Plasma fluid parameters calculated from solar wind and magnetic field data obtained on ISEE 3 were studied. The characteristic properties of driver gas following interplanetary shocks was determined. Of 54 shocks observed from August 1978 to February 1980, nine 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 nine 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 bidirectional flow of suprathermal solar wind electrons at higher energies.

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

1982-01-01

266

Solar and interplanetary precursors of geomagnetic storms in solar cycle 23  

NASA Astrophysics Data System (ADS)

Estimating the magnetic storm effectiveness of solar and associated interplanetary phenomena is of practical importance for space weather modelling and prediction. This article presents results of a qualitative and quantitative analysis of the probable causes of geomagnetic storms during the 11-year period of solar cycle 23: 1996-2006. Potential solar causes of 229 magnetic storms (Dst ? -50 nT) were investigated with a particular focus on halo coronal mass ejections (CMEs). A 5-day time window prior to the storm onset was considered to track backward the Sun's eruptions of halo CMEs using the SOHO/LASCO CMEs catalogue list. Solar and interplanetary (IP) properties associated with halo CMEs were investigated and correlated to the resulting geomagnetic storms (GMS). In addition, a comparative analysis between full and partial halo CME-driven storms is established. The results obtained show that about 83% of intense storms (Dst ? -100 nT) were associated with halo CMEs. For moderate storms (-100 nT < Dst ? -50 nT), only 54% had halo CME background, while the remaining 46% were assumed to be associated with corotating interaction regions (CIRs) or undetected frontside CMEs. It was observed in this study that intense storms were mostly associated with full halo CMEs, while partial halo CMEs were generally followed by moderate storms. This analysis indicates that up to 86% of intense storms were associated with interplanetary coronal mass ejections (ICMEs) at 1 AU, as compared to moderate storms with only 44% of ICME association. Many other quantitative results are presented in this paper, providing an estimate of solar and IP precursor properties of GMS within an average 11-year solar activity cycle. The results of this study constitute a key step towards improving space weather modelling and prediction.

Uwamahoro, J.; McKinnell, L.-A.

2013-02-01

267

A shock surface geometry - The February 15-16, 1967, event. [solar flare associated interplanetary shock  

NASA Technical Reports Server (NTRS)

An estimated shape is presented for the surface of the flare-associated interplanetary shock of February 15-16, 1967, as seen in the ecliptic-plane cross section. The estimate is based on observations by Explorer 33 and Pioneers 6 and 7. The estimated shock normal at the Explorer 33 position is obtained by a least-squares shock parameter-fitting procedure for that satellite's data; the shock normal at the Pioneer 7 position is found by using the magnetic coplanarity theorem and magnetic-field data. The average shock speed from the sun to each spacecraft is determined along with the local speed at Explorer 33 and the relations between these speeds and the position of the initiating solar flare. The Explorer 33 shock normal is found to be severely inclined and not typical of interplanetary shocks. It is shown that the curvature of the shock surface in the ecliptic plane near the earth-Pioneer 7 region is consistent with a radius of not more than 0.4 AU.

Lepping, R. P.; Chao, J. K.

1976-01-01

268

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

269

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. 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.

Wilson, L. B., III

2012-01-01

270

Transport in the interplanetary medium of coronal mass ejections  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are large scale structures of plasma and magnetic field expelled from the Sun to the interplanetary medium and generally observed in white light coronagraphs. During their travel, in the interplanetary medium these structures named interplanetary coronal mass ejections (ICMEs), suffer acceleration or deceleration due to the interaction with the ambient solar wind. This process can be understood as a transference of momentum between the interplanetary CME (ICME) and the solar wind. This process seems to be fundamentally different for `slow' and `fast' ICMEs (compared with the ambient solar wind velocity). In this work, we approach the problem from the fluid dynamics point of view and consider the ICMEs - solar wind system as two interacting fluids under the action of viscous forces. We note that this interaction is a special case of interaction between low density plasmas. Using these viscous forces in the Newtons Second Law, we obtained an analytical solution for the ICME velocity as a function of time. By comparing our analytic results with empirical models found in recent literature, we suggested values for the viscosity and drag parameters in this system. In this first approximation we have neglected the magnetic field.

Borgazzi, A.; Lara, A.; Romero-Salazar, L.; Ventura, A.

2008-07-01

271

Evolution and interaction of large interplanetary streams  

NASA Technical Reports Server (NTRS)

A computer simulation for the evolution and interaction of large interplanetary streams based on multi-spacecraft observations and an unsteady, one-dimensional MHD model is presented. Two events, each observed by two or more spacecraft separated by a distance of the order of 10 AU, were studied. The first simulation is based on the plasma and magnetic field observations made by two radially-aligned spacecraft. The second simulation is based on an event observed first by Helios-1 in May 1980 near 0.6 AU and later by Voyager-1 in June 1980 at 8.1 AU. These examples show that the dynamical evolution of large-scale solar wind structures is dominated by the shock process, including the formation, collision, and merging of shocks. The interaction of shocks with stream structures also causes a drastic decrease in the amplitude of the solar wind speed variation with increasing heliocentric distance, and as a result of interactions there is a large variation of shock-strengths and shock-speeds. The simulation results shed light on the interpretation for the interaction and evolution of large interplanetary streams. Observations were made along a few limited trajectories, but simulation results can supplement these by providing the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. The use of a quantitative nonlinear simulation model including shock merging process is crucial in the interpretation of data obtained in the outer heliosphere.

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

1985-01-01

272

InterplanetarySupply Chain Management &  

E-print Network

to system development. A simple example of this is standard and metric tools. In most cases, where Learned in NASA Space Flight Interplanetary Supply Chain Management & Logistics Architectures William A. In the consideration of these objectives, a need for a study on NASA Lessons Learned was recognized. The study

de Weck, Olivier L.

273

Sources of interplanetary dust: Asteroids  

Microsoft Academic Search

The asteroid belt is examined as a potential source of interplanetary dust. Using results from the Pioneer-10 experiments the relative contribution of asteroidal and cometary particles to the Zodiacal cloud is estimated using methods developed in earlier studies of meteoroidal collisions (collisional model). It is found that the contribution of asteroidal particles to dust in the asteroidal belt is small

J. S. Dohnanyi

274

3-D MHD Model of the Solar Wind-Interplanetary Space Combining System 1:Variation of Solar Wind Speed Associated with the Photospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

Existing global models of the solar-wind/IMF expanding to the Earth's orbit are basically grounded in the idea of "source surface." It is widely accepted that the sector structure and the solar wind speed are primarily controlled by the magnetic field at the source surface and the so-called "expansion factor." On the other hand, 3-D MHD model is still off from practical use because both of scientific and technical problems. One of the former problems is the reproduction of supersonic solar-wind. From the viewpoint of the physics of the solar wind, coronal heating and outward acceleration mechanisms are invoked to explain the supersonic evolution of the solar wind. Since the mechanism responsible for the heating/acceleration is still one of the primary subjects of the physics of the solar wind, many MHD models have taken into account their effects by incorporating additional source terms corresponding to promising candidates such as thermal conductions, radiation losses and wave pressures. However there are few MHD models considering the effect of the expansion factor, which determines the solar-wind speed in the series of source surface models. In this study we newly incorporate the flux tube expansion rate into the MHD equation system including heat source function in the energy equation. Appling the unstructured grid system, we achieved the dense grid spacing at the inner boundary, which enable us to adopt realistic solar magnetic fields, and a size of simulation space of 1AU. Photospheric magnetic field data is used as the inner boundary condition.The simulation results are summarized as: (1) The variation of solar wind speed is well controlled by the structure of magnetic fields at and little above the solar surface and (2) Far above the solar surface, the interface between high and low speed flows evolves to a structure suggestive of CIRs. Comparing the data from simulation with the actual solar wind data obtained by spacecrafts, we will discuss the future improvement of our model. Non-stationary phenomena such as CMEs are still beyond of this study. Acknowledgement: Wilcox Solar Observatory data used in this study was obtained via the web site http://quake.stanford.edu/~wso courtesy of J.T. Hoeksema.

Nakamizo, A.; Tanaka, T.

2006-12-01

275

Ionospheric Response to the Changes in the Interplanetary Magnetic Field (IMF) Bz Under Strong Positive IMF By Conditions, as Seen using SuperDARN and PolarDARN Radars.  

NASA Astrophysics Data System (ADS)

The interplanetary magnetic field (IMF) is known to have a profound influence on the ionospheric convection pattern at high latitudes. Thus, when the IMF has a dominant southward (Bz) component, the convection over the central polar cap is anti-sunward and closes through the dawn and dusk sectors to produce a familiar 2-cell convection pattern. For strong northward IMF conditions, the pattern is thought to break into four cells, with sunward convection taking place over the noon sector of the polar cap. For strong IMF By conditions the standard 2-cell convection pattern is believed to become asymmetric and/or to rotate from its basic alignment with the noon-to- midnight meridian to a more dusk-to-dawn or dawn-to-dusk alignment. With the help of the new PolarDARN radar in combination with other SuperDARN radar data, we have been able to observe changes occurring deep into the polar cap during a period of strong sustained positive IMF By, when the Bz component was always less than 20% of the By component in magnitude. The basic shape of the convection pattern was highly reminiscent of the Heppner-Maynard `BC' convection pattern predicted for strong positive By conditions ( Heppner and Maynard, JGR, 92, 4467, 1987). We note that we observed very clear changes in the convection pattern as Bz changed signs, with a distinct sub-cell on the evening side being present while the IMF Bz component was greater than zero. The sub-cell completely vanished when the Bz component changed sign. These variations were unexpected in view of the relatively small IMF Bz magnitudes involved. Interestingly enough, this feature would have been missed, had the PolarDARN radar data not been added to the data obtained with the rest of the SuperDARN radars. We will discuss the implications of our findings for our understanding of ionospheric/magnetospheric convection in response to solar wind inputs.

Choudhary, R.; St.-Maurice, J.; Sofko, G. J.

2007-12-01

276

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

277

Fluctuations of cosmic rays and IMF in the vicinity of interplanetary shocks  

Microsoft Academic Search

Fluctuations of cosmic rays and interplanetary magnetic field upstream of interplanetary shocks are studied using data of ground-based polar neutron monitors as well as measurements of energetic particles and solar wind plasma parameters aboard the ACE spacecraft. It is shown that coherent cosmic ray fluctuations in the energy range from 10keV to 1GeV are often observed at the Earth’s orbit

A. V. Grigoryev; S. A. Starodubtsev; V. G. Grigoryev; I. G. Usoskin; K. Mursula

2008-01-01

278

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

279

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

280

Magnetospheric substorms are strongly modulated by interplanetary high-speed streams  

NASA Astrophysics Data System (ADS)

The occurrence of substorms was examined over a complete 11-year solar cycle, identifying over 5000 substorms. It was found that high-speed streams strongly modulate the substorm occurrence rate, peak amplitude and ionospheric dissipation in the form of Joule heating and auroral electron precipitation. Substorms occurring during the years of frequent interplanetary high-speed streams (1994 and 2003) are 32% more intense, on average, and transfer twice as much magnetic energy to the auroral ionosphere as the substorms occurring during the years of few or no high-speed streams (1993, 1995-2002). To characterize and to predict the substorm activity we form a new measure, the substorm activity parameter Rsu, which we expect to become a powerful tool in analyzing the near-Earth space climate.

Tanskanen, E. I.; Slavin, J. A.; Tanskanen, A. J.; Viljanen, A.; Pulkkinen, T. I.; Koskinen, H. E. J.; Pulkkinen, A.; Eastwood, J.

2005-08-01

281

Alfven waves in spiral interplanetary field  

NASA Technical Reports Server (NTRS)

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

Whang, Y. C.

1973-01-01

282

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

283

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

284

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

285

Long-living structures in the interplanetary medium according to observations of Jovian electrons  

NASA Astrophysics Data System (ADS)

Quasi-stationary structures appearing in the interplanetary medium near 1 AU are studied, which represent magnetic traps for energetic electrons emitted from the magnetosphere of Jupiter. When such a trap passes by Earth, enhanced electron fluxes are observed. The flux peaks are not high; they are only visible clearly at low background, i.e. low solar activity. We compare electron flux observations during subsequent solar activity minima. A particularly long series was observed during the last minimum in 2007-2009 with an average period of about 26 days, instead of 27.3 days expected - the synodic period of the Earth. During other solar activity minima the period also differs from it by 1-2 days suggesting the existence of a complicated structure consisting of magnetic traps which allows Jovian electrons to arrive at Earth irrespective of the relative position of Jupiter and Earth. The size of traps, their longitudinal extension and the lifetime of electrons is investigated together with the magnetic field and its variability. The variation of the periodicity of Jovian electron fluxes due to co-rotation with the Sun is connected to the variability of the magnetic structure of the traps in the course of one solar rotation (? 25 days). In numerical simulations assuming perfect co-rotation and Jupiter as a moving source in the co-rotating frame a combined effect of the CIR and magnetic connection is obtained and fitted to the observations.

Kecskemety, Karoly; Logachev, Yurii; Daibog, Elena; Kota, Jozsef

286

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

287

Wide longitudinal distribution of interplanetary electrons following the 7 February 2010 solar event: Observations and transport modeling  

NASA Astrophysics Data System (ADS)

We analyze 65-105 keV electrons in the 7 February 2010 solar electron event observed simultaneously by STEREO-A, STEREO-B, and ACE. A method to reconstruct the full-electron pitch angle distributions from the four Solar Electron and Proton Telescope sensors on STEREO-A/B and the Solar Electron and Proton Telescope instrument on ACE in the energy range of approximately 60-300 keV for periods of incomplete angular coverage is presented. A transport modeling based on numerical solutions of a three-dimensional particle propagation model which includes pitch angle scattering and focused transport is applied to the intensity and anisotropy profiles measured on all three spacecraft. Based on an analysis of intensity gradients observed between the three spacecraft, we find that the lateral transport of the electrons occurs partially close to the Sun, due to effects of nonradial divergence of magnetic field lines or particle diffusion, and partially in the interplanetary medium. For the mean free paths characterizing the electron diffusion parallel and perpendicular to the interplanetary magnetic field, we derive values of ??˜ 0.1 AU and ??˜ 0.01 AU. In comparison with results from other particle events which we had previously analyzed in a similar manner we discuss whether the diffusion mean free paths parallel and perpendicular to the average magnetic field might be related with each other, and whether the particle transport perpendicular to the average magnetic field is more likely due to particles following meandering magnetic field lines, or due to particles being scattered off individual field lines.

Dröge, W.; Kartavykh, Y. Y.; Dresing, N.; Heber, B.; Klassen, A.

2014-08-01

288

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

289

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

290

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.

291

Venus Express observations of the induced magnetosphere at dayside during the passage of an interplanetary coronal mass ejection  

Microsoft Academic Search

Although there is no intrinsic magnetic field at Venus, the convected interplanetary magnetic field piles up to form a magnetic barrier in the dayside inner magnetosheath. In analogy to the Earth's magnetosphere, the magnetic barrier acts as an induced magnetosphere on the dayside and hence as the obstacle to the solar wind. It consists of regions near the planet and

Tielong Zhang

2008-01-01

292

On the solar origin of interplanetary disturbances observed in the vicinity of the Earth  

NASA Astrophysics Data System (ADS)

The solar origin of 40 interplanetary disturbances observed in the vicinity of the Earth between January 1997 and June 1998 is investigated in this paper. Analysis starts with the establishment of a list of Interplanetary Mass Ejections or ICMEs (magnetic clouds, flux ropes and ejecta) and of Interplanetary Shocks measured at WIND for the period for which we had previously investigated the coupling of the interplanetary medium with the terrestrial ionospheric response. A search for associated coronal mass ejections (CMEs) observed by LASCO/SOHO is then performed, starting from an estimation of the transit time of the inter-planetary perturbation from the Sun to the Earth, assumed to be achieved at a constant speed (i.e. the speed measured at 1 AU). EIT/SOHO and Nançay Radioheliograph (NRH) observations are also used as proxies in this identification for the cases when LASCO observations do not allow one to firmly establish the association. The last part of the analysis concerns the identification of the solar source of the CMEs, performed using a large set of solar observations from X-ray to radio wavelengths. In the present study, this association is based on a careful examination of many data sets (EIT, NRH and H images and not on the use of catalogs and of Solar Geophysical Data reports). An association between inter-planetary disturbances and LASCO/CMEs or proxies on the disk is found for 36 interplanetary events. For 32 events, the solar source of activity can also be identified. A large proportion of cases is found to be associated with a flare signature in an active region, not excluding of course the involvement of a filament. Conclusions are finally drawn on the propagation of the disturbances in the interplanetary medium, the preferential association of disturbances detected close to the Earth’s orbit with halos or wide CMEs and the location on the solar disk of solar sources of the interplanetary disturbances during that period.

Vilmer, N.; Pick, M.; Schwenn, R.; Ballatore, P.; Villain, J. P.

2003-04-01

293

Quaternion Averaging  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

294

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

295

ULF waves and energetic electrons resulting from intense interplanetary shocks  

NASA Astrophysics Data System (ADS)

We present results of modelling the energetic electron response to an intense interplanetary shock on November 7, 2004, when the interplanetary magnetic field was northward. The shock was accompanied by large amplitude monochromatic ULF waves in the inner magnetosphere, and energetic electrons that may have resulted from drift-bounce resonance interaction with the waves. A plethora of spacecraft observed the shock passage in the solar wind, outer and inner magnetosphere. We briefly review the spacecraft observations, and present global simulations of the shock interaction with the magnetosphere using the LFM model. Using the global E and B obtained from the LFM model, we input time series to a test-particle model that advances phase space density in response to ULF waves, and attempt to explain the elevation of the MeV electron flux that accompanies the shock.

Rankin, R.; Degeling, A. W.; Elkington, S. R.

2012-12-01

296

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

297

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

298

Magnetic clouds, helicity conservation, and intrinsic scale flux ropes  

NASA Technical Reports Server (NTRS)

An intrinsic-scale flux-rope model for interplanetary magnetic clouds, incorporating conservation of magnetic helicity, flux and mass is found to adequately explain clouds' average thermodynamic and magnetic properties. In spite their continuous expansion as they balloon into interplanetary space, magnetic clouds maintain high temperatures. This is shown to be due to magnetic energy dissipation. The temperature of an expanding cloud is shown to pass through a maximum above its starting temperature if the initial plasma beta in the cloud is less than 2/3. Excess magnetic pressure inside the cloud is not an important driver of the expansion as it is almost balanced by the tension in the helical field lines. It is conservation of magnetic helicity and flux that requires that clouds expand radially as they move away from the Sun. Comparison with published data shows good agreement between measured cloud properties and theory. Parameters determined from theoretical fits to the data, when extended back to the Sun, are consistent with the origin of interplanetary magnetic clouds in solar filament eruptions. A possible extension of the heating mechanism discussed here to heating of the solar corona is discussed.

Kumar, A.; Rust, D. M.

1995-01-01

299

Particle Acceleration at Interplanetary Discontinuities  

NASA Astrophysics Data System (ADS)

Interplanetary discontinuities, long-duration Alfvenic fluctuations and transient structures such as shocks, stream interfaces (SIs), and coronal mass ejections (CME's) are considered to be prime candidates for accelerating particles in space and are therefore also responsible for producing the suprathermal particle population. The spectral slope of the phase space density of of the suprathermal particle population has been reported to cluster around v-5 but may vary significantly over longer time periods [1]. It is unclear, however, how such as slope is generated and how these interplanetary structures contribute. In a statistical study for the years 2007-2009 we investigate shocks, SIs (alone or combined) as well as CME's with respect to ion acceleration efficiency and the formation of suprathermal tails in the particle distribution. This depends on solar wind plasma conditions (for example, the presence of Alfvenic fluctuations) and on the acceleration process, the shock geometry, and on the intensity of the source population. Pickup helium (He+) is an excellent tracer for interplanetary discontinuities. It is abundant at these plasma discontinuities because it is preferentially accelerated compared to solar wind ions (including He+2). This study shows that all of these discontinuities produce a suprathermal population with varying number density and spectral slope. Depending on the discontinuity/structure type, the solar wind plasma conditions, the data accumulation time, and the location within the discontinuity, the slopes of the suprathermal tails are shown to vary between v-3 and v-7. This large range is most likely due to the fact that the plasma at these discontinuities has not yet reached stationary state conditions. This conjecture can be confirmed by measurements and simulated particle distributions. [1] Gloeckler et al., : AIP Conf. Proc. 1436, 136 (2012); doi: 10.1063/1.4723601

Kucharek, Harald; Farrugia, Charles; Popecki, Mark; Klecker, Berndt; Simunac, Kristin; Galvin, Antoinette

2014-05-01

300

Interplanetary Space Weather and Its Planetary Connection  

Microsoft Academic Search

Interplanetary travel is not just a science fiction scenario anymore, but a goal as realistic as when our ancestors started to cross the oceans. With curiosity driving humans to visit other planets in our solar system, the understanding of interplanetary space weather is a vital subject today, particularly because the physical conditions faced during a space vehicle's transit to its

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

2008-01-01

301

Dynamic Model Development for Interplanetary Navigation  

Microsoft Academic Search

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,

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

2005-01-01

302

A quasi-linear kinetic equation for cosmic rays in the interplanetary medium  

NASA Technical Reports Server (NTRS)

A kinetic equation for interplanetary cosmic rays is set up with the aid of weak-plasma-turbulence theory for an idealized radially symmetric model of the interplanetary magnetic field. As a starting point, this treatment invokes the Vlasov equation instead of the traditional Fokker-Planck equation. Quasi-linear theory is applied to obtain a momentum diffusion equation for the heliocentric frame of reference which describes the interaction of cosmic rays with convecting magnetic irregularities in the solar-wind plasma. Under restricted conditions, the well-known equation of solar modulation can be obtained from this kinetic equation.

Luhmann, J. G.

1976-01-01

303

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

304

Average configuration of the distant (less than 220-earth-radii) magnetotail - Initial ISEE-3 magnetic field results  

NASA Technical Reports Server (NTRS)

Magnetic field measurements from the first two passes of the ISEE-3 GEOTAIL Mission have been used to study the structure of the trans-lunar tail. Good agreement was found between the ISEE-3 magnetopause crossings and the Explorer 33, 35 model of Howe and Binsack (1972). Neutral sheet location was well ordered by the hinged current sheet models based upon near earth measurements. Between X = -20 and -120 earth radii the radius of the tail increases by about 30 percent while the lobe field strength decreases by approximately 60 percent. Beyond X = -100 to -1200 earth radii the tail diameter and lobe field magnitude become nearly constant at terminal values of approximately 60 earth radii and 9 nT, respectively. The distance at which the tail was observed to cease flaring, 100-120 earth radii, is in close agreement with the predictions of the analytic tail model of Coroniti and Kennel (1972). Overall, the findings of this study suggest that the magnetotail retains much of its near earth structure out to X = -220 earth radii.

Slavin, J. A.; Tsurutani, B. T.; Smith, E. J.; Jones, D. E.; Sibeck, D. G.

1983-01-01

305

The interaction of a magnetic cloud with the Earth - Ionospheric convection in the Northern and Southern Hemispheres for a wide range of quasi-steady interplanetary magnetic field conditions  

NASA Technical Reports Server (NTRS)

Observations are presented of the ionospheric convection in cross sections of the polar cap and auroral zone as part of the study of the interaction of the Earth's magnetosphere with the magnetic cloud of January 13-15, 1988. For strongly northward IMF, the convection in the Southern Hemisphere is characterized by a two-cell convection pattern comfined to high latitudes with sunward flow over the pole. The strength of the flows is comparable to that later seen under southward IMF. Superimposed on this convection pattern there are clear dawn-dusk asymmetries associated with a one-cell convection component whose sense depends on the polarity of the magnetic cloud's large east-west magnetic field component. When the cloud's magnetic field turns southward, the convection is characterized by a two-cell pattern extending to lower latitude with antisunward flow over the pole. There is no evident interhemispheric difference in the structure and strength of the convection. Superimposed dawn-dusk asymmetries in the flow patterns are observed which are only in part attributable to the east-west component of the magnetic field.

Freeman, M. P.; Farrugia, C. J.; Burlaga, L. F.; Hairston, M. R.; Greenspan, M. E.; Ruohoniemi, J. M.; Lepping, R. P.

1993-01-01

306

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

307

Analysis of double-step response to an interplanetary shock in the dayside magnetosphere  

NASA Astrophysics Data System (ADS)

We present an analysis of double-step magnetic field enhancement caused by interplanetary (IP) shock impacts on the Earth's magnetosphere. The structures were observed by the GOES-8, 10, 11, and 12 spacecraft in the dayside geostationary orbit, particularly during northward interplanetary magnetic field (IMF) conditions. The double-step structures, similar to what is observed in the ground horizontal magnetic field (H) component at low and mid latitudes, were observed preferentially on the dayside. Structures observed around 12-15 magnetic local time (MLT) displayed the steepest initial enhancement step, followed by a magnetic field strength decrease before the second enhancement step. At other dayside MLTs of the geostationary orbit, the initial response was smoother, and no decrease was observed before the second step. We suggest that this MLT asymmetry in the decrease of the total magnetic field is caused by the pushing of the plasmaspheric ions over the geostationary orbit due to the magnetospheric compression.

Andréeová, K.; Juusola, L.; Kilpua, E. K. J.; Koskinen, H. E. J.

2014-10-01

308

Coordinated THEMIS spacecraft and all-sky imager observations of interplanetary shock effects on plasma sheet flow bursts, poleward boundary intensifications, and streamers  

NASA Astrophysics Data System (ADS)

order to characterize plasma sheet and nightside auroral disturbances in response to interplanetary shocks, we have examined three interplanetary shock events that occurred when multiple Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft were located in the plasma sheet near midnight while ground-based aurora data were available near the spacecraft footprints. Large-scale responses we found are that the magnetotail magnetic pressure started to increase within ~2 min of the SYM-H jump, and the diffuse aurora near the auroral equatorward boundary intensified over a wide magnetic local time range, due to the shock compressional effect, on average 3 min after the shock arrival. In addition, we also identified plasma sheet and auroral disturbances that are more transient and localized. Earthward or equatorward flow bursts are observed in the near-Earth plasma sheet on average 5 min after the SYM-H increase. We find that these fast flows, originating downtail of the near-Earth spacecraft, form a localized channel, since only some of the spacecraft detected the flow bursts. Poleward boundary intensifications (PBIs) and subsequent north-south directed auroral streamers are then formed, while no substorm activity was detected. Those auroral forms are also localized in space near midnight and around the footprint of the spacecraft. These results indicate that the fast flows are azimuthally localized channels and are the magnetotail counterpart of the PBIs and streamers and that such localized disturbances are triggered by the interplanetary shocks in addition to the large-scale compression of the magnetosphere.

Yue, Chao; Nishimura, Yukitoshi; Lyons, Larry R.; Angelopoulos, Vassilis; Donovan, Eric F.; Shi, Quanqi; Yao, Zhonghua; Bonnell, John W.

2013-06-01

309

Magnetic Storms  

NASA Technical Reports Server (NTRS)

This talk provides a brief summary of the first conference devoted entirely to magnetic storms. Topics cover the relevant phenomena at the Sun/corona, propogation of these structures through interplanetary space, the response of the magnetosphere to interaction with these interplanetary structures, the formation of the storm time ring current (in particular the oxygen content of the ring-current), and storm ionospheric effects and ground based effects.

Tsurutani, B. T.; Gonzalez, W. D.; Kamide, Y.

1996-01-01

310

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

311

Volatiles in interplanetary dust particles  

NASA Technical Reports Server (NTRS)

Interplanetary dust particles (IDP's) collected by specially equipped aircraft flying in the stratosphere have generated a lot of interest during the last decade. These particles, consisting of primitive materials originating in small solar system bodies such as comets and asteroids, are complex heterogeneous species with a variety of components. In order to understand the past histories of IDP's, it is particularly important to know the nature of the volatiles present. Volatiles released from a number of IDP's have been studied; however, a large number of particles must be studied in order to establish trends, to classify types of IDP's, and to have comparison data for determining the origins of IDP's. This study involves the analysis of six IDP's using laser microprobe mass spectrometry.

Bustin, Roberta

1991-01-01

312

Infrared emission from interplanetary dust  

NASA Astrophysics Data System (ADS)

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.

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

1989-02-01

313

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

314

Post-shock spikes: A new feature of proton and alpha enhancements associated with an interplanetary shock wave  

NASA Technical Reports Server (NTRS)

Abrupt and prolonged enhancements in the intensities of 100 to approximately 2000 keV nucleon protons and alpha particles observed in interplanetary space are interpreted as particle populations confined between an interplanetary shock front and a magnetic field discontinuity. Prominent intensity spikes observed only below approximately 400 keV per charge for both protons and alpha particles several hours behind the shock front suggest that some fraction of the confined particles is accelerated by an energy per charge dependent process.

Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.; Hovestadt, D.

1974-01-01

315

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

316

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

317

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

318

Comparison of Interplanetary Disturbances at the NEAR Spacecraft with Coronal Mass Ejections at the Sun  

NASA Astrophysics Data System (ADS)

We examined interplanetary (IP) magnetic field disturbances recorded by the Near Earth Asteroid Rendezvous-Shoemaker spacecraft (NEAR) when it was above either the east or west solar limb as seen from Earth; we then identified the associated coronal mass ejections (CMEs) detected above the limbs by the SOHO LASCO coronagraph. We found 10 cases in which a nonrecurring IP disturbance could be associated with a CME. Eight of the disturbances included a magnetic flux rope signature. Flux rope chirality and axis orientation were determined for each one and compared with chirality and axis orientation at the Sun, as inferred from flux rope signatures-filaments and sigmoids-that could be associated with the CMEs. In most cases, the chirality and orientation inferred from these preeruption flux rope signatures agreed well with the flux rope signatures at NEAR. These results suggest, in agreement with Plunkett and coworkers, that the flux ropes existed prior to eruption and that the flux ropes on the Sun become flux ropes in IP space. Comparisons of the CME speeds to the time-of-flight average speeds showed that flux ropes are less accelerated or decelerated by the solar wind than are the CME leading edges. These results imply that the faint features or loops that make up the CME leading edges are probably distinct from the flux ropes.

Rust, D. M.; Anderson, B. J.; Andrews, M. D.; Acuña, M. H.; Russell, C. T.; Schuck, P. W.; Mulligan, T.

2005-03-01

319

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

320

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

321

Analysis of human brain exposure to low-frequency magnetic fields: a numerical assessment of spatially averaged electric fields and exposure limits.  

PubMed

Compliance with the established exposure limits for the electric field (E-field) induced in the human brain due to low-frequency magnetic field (B-field) induction is demonstrated by numerical dosimetry. The objective of this study is to investigate the dependency of dosimetric compliance assessments on the applied methodology and segmentations. The dependency of the discretization uncertainty (i.e., staircasing and field singularity) on the spatially averaged peak E-field values is first determined using canonical and anatomical models. Because spatial averaging with a grid size of 0.5?mm or smaller sufficiently reduces the impact of artifacts regardless of tissue size, it is a superior approach to other proposed methods such as the 99th percentile or smearing of conductivity contrast. Through a canonical model, it is demonstrated that under the same uniform B-field exposure condition, the peak spatially averaged E-fields in a heterogeneous model can be significantly underestimated by a homogeneous model. The frequency scaling technique is found to introduce substantial error if the relative change in tissue conductivity is significant in the investigated frequency range. Lastly, the peak induced E-fields in the brain tissues of five high-resolution anatomically realistic models exposed to a uniform B-field at ICNIRP and IEEE reference levels in the frequency range of 10?Hz to 100?kHz show that the reference levels are not always compliant with the basic restrictions. Based on the results of this study, a revision is recommended for the guidelines/standards to achieve technically sound exposure limits that can be applied without ambiguity. PMID:23404214

Chen, Xi-Lin; Benkler, Stefan; Chavannes, Nicholas; De Santis, Valerio; Bakker, Jurriaan; van Rhoon, Gerard; Mosig, Juan; Kuster, Niels

2013-07-01

322

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

323

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

324

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

325

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

326

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

327

Magnetic cloud induced magnetic storms: a lack of classical substorm expansion phases  

NASA Technical Reports Server (NTRS)

The purpose of this paper will be to examine a specific but important subset of magnetic storms, those that are caused by large southward, smoothly rotating magnetic fields: interplanetary magnetic clouds.

Tsurutani, B. T.; Zhou, X. Y.; Gonzalez, W. D.

2001-01-01

328

International Launch Vehicle Selection for Interplanetary Travel  

NASA Technical Reports Server (NTRS)

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

Ferrone, Kristine; Nguyen, Lori T.

2010-01-01

329

Quiet time particle acceleration in interplanetary space  

E-print Network

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

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

2004-12-09

330

Solar, Heliospheric, and Interplanetary Environment  

NSF Publications Database

... proposals to investigate the connections between eruptive events and magnetic phenomena on the Sun ... will be evaluated by considering the relation of the proposed activity to science community goals ...

331

Investigations of cosmic ray anisotropies and their relationship to concurrent magnetic field data  

NASA Technical Reports Server (NTRS)

Investigations of cosmic ray anisotropies and their relationship to concurrent magnetic field data are reported. These investigations range in scope from the examination of data very late in the decay phase of a solar particle event where long term (approximately 6 hour) averages are used and definite interplanetary effects sought after to an examination of the change in low energy particle anisotropy as the satellite approaches the bow shock and the magnetopause.

Allum, F. R.

1974-01-01

332

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

333

The cause of high-intensity long-duration continuous AE activity (HILDCAAS) - Interplanetary Alfven wave trains  

NASA Technical Reports Server (NTRS)

It is shown that high intensity (AE of greater than 1,000 nT), long duration (T of greater than 2d) continuous auroral activity events are caused by outward (from the sun) propagating interplanetary Alfven wave trains. The Alfven waves are often (but not always) detected several days after major interplanetary events, such as shocks and solar wind density enhancements. Presumably, magnetic reconnection between the southward components of the Alfven wave magnetic fields and magnetospheric fields is the mechanism for transfer of solar wind energy to the magnetosphere.

Tsurutani, Bruce T.; Gonzalez, Walter D.

1987-01-01

334

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

335

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

336

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

337

Apollo and the Space Race! Interplanetary Travel!  

E-print Network

Seminar 6! Apollo and the Space Race! Interplanetary Travel! FRS 104, Princeton University! Robert" !! Arms race" !! Treaties" !! Prestige and perceptions" !! Eisenhower, 1958" !! Outer space only Rendezvous, NASA monograph" #12;Trouble in the Spacecraft: Ejection Capsule" A Space Strategy for the United

Stengel, Robert F.

338

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

339

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

340

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

341

INTERPLANETARY TYPE III RADIOBURSTS AND RELATIVISTIC ELECTRONS  

E-print Network

INTERPLANETARY TYPE III RADIOBURSTS AND RELATIVISTIC ELECTRONS S. HUCKE*, M.-B. KALLENRODE, and with the fluxes of ~ 0.5 MeV electrons measured by HELIOS. For 51 flare-associated kilometric type III bursts (FAIII bursts) with 1og(TA)> 10 we find: (1) 25 bursts (49%) are accompanied by a relativistic electron

Steinhoff, Heinz-Jürgen

342

Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data  

Microsoft Academic Search

Hourly averaged interplanetary magnetic field (IMF) and plasma data from the Advanced Composition Explorer (ACE) and Wind spacecraft, generated from 1 to 4 min resolution data time-shifted to Earth have been analyzed for systematic and random differences. ACE moments-based proton densities are larger than Wind\\/Solar Wind Experiment (SWE) fits-based densities by up to 18%, depending on solar wind speed. ACE

J. H. King; N. E. Papitashvili

2005-01-01

343

Upstream electron oscillations and ion overshoot at an interplanetary shock wave  

NASA Technical Reports Server (NTRS)

During the passage of a large interplanetary shock on Oct. 13, 1981, the ISEE-1 and -2 spacecraft were in the solar wind outside of the upstream region of the bow shock. The high time resolution data of the University of California particle instruments allow pinpointing the expected electron spike as occurring just before the magnetic ramp. In addition, two features that occur at this shock have not been observed before: electron oscillations associated with low frequency waves upstream of the shock and sharp 'overshoot' (about 1 sec) in the ion fluxes that occur right after the magnetic ramp. This interplanetary shock exhibits many of the same characteristics that are observed at the earth's bow shock.

Potter, D. W.; Parks, G. K.

1983-01-01

344

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

345

Cosmic ray scintillations. III - The low-frequency limit and observations of interplanetary scintillations  

NASA Technical Reports Server (NTRS)

Statistically significant broad-band fluctuations, or 'scintillations', in the high-energy (about 1 GeV) cosmic ray intensity observed by neutron monitors are interpreted. The scintillations are caused by fluctuations in the interplanetary magnetic field. The theory of the scintillations is presented for the low-frequency limit, below .0001 Hz, including the effects of the earth's rotation on the fluxes observed by the neutron monitors. The observations and the theory are in good agreement. The shapes and amplitudes of the observed spectra and, in particular, a broad enhancement in the power spectrum of the Deep River neutron monitor flux near 1 cpd are related to the interplanetary magnetic field power spectrum and the cosmic ray anisotropy.

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

1974-01-01

346

Quasi-linear theory and transport theory. [particle acceleration in interplanetary medium  

NASA Technical Reports Server (NTRS)

The theory of energetic particle scattering by magnetostatic fluctuations is reviewed in so far as it fails to produce the rigidity-independent mean-free-paths observed. Basic aspects of interplanetary magnetic field fluctuations are reviewed with emphasis placed on the existence of dissipation range spectra at high wavenumbers. These spectra are then incorporated into existing theories for resonant magnetostatic scattering and are shown to yield infinite mean-free-paths. Nonresonant scattering in the form of magnetic mirroring is examined and offered as a partial solution to the magnetostatic problem. In the process, mean-free-paths are obtained in good agreement with observations in the interplanetary medium at 1 AU and upstream of planetary bow shocks.

Smith, Charles W.

1992-01-01

347

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

348

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

349

Comparison of Yohkoh x-ray coronal events with Ulysses interplanetary events  

NASA Technical Reports Server (NTRS)

The Yohkoh soft X-ray telescope (SXT) has observed several largescale eruptive events per year for the first three years of observations (Aug. 1991 - Nov. 1994) Such events are most prominent at high latitudes, but resemble long-duration flare events seen in active regions. Some of the high-latitude events have now been identified in the Ulysses/SWICS data base during the Ulysses south polar passage. There are puzzling examples of solar events with no interplanetary counterparts. A comparison of coronal and interplanetary events can lead to better models for mapping interplanetary disturbances back to their source location, especially by combining Yohkoh morphology with three-dimensional representations of the coronal magnetic field. In this paper we describe the parameters of the hot plasma seen by SXT. There is clear evidence for non radial motion in specific events. We present comparisons between the ionization temperature of the interplanetary plasma with that observed at the Sun in cases where this is possible.

Lemen, J. R.; Acton, L. W.; Alexander, D.; Galvin, A. B.; Harvey, K. L.; Hoecksema, J. T.; Zhao, X.; Hudson, H.

1995-01-01

350

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

351

Multiple spacecraft observations of interplanetary shocks: four spacecraft determination of shock normals  

Microsoft Academic Search

ISEE 1,2,3 IMP8, and Prognoz 7 observations of interplanetary shocks in 1978 and 1979 provide five instances where a single shock is observed by four spacecraft. These observations are used to determine best-fit normals for these five shocks. In addition to providing well-documented shocks for furture techniques. When the angle between upstream and downstream magnetic field is greater than 20,

C.T. Russell; M. M. Mellott; E. J. Smith; J. H. King

1983-01-01

352

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

353

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

354

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

355

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

356

Interplanetary Proton Cumulated Fluence Model Update  

NASA Astrophysics Data System (ADS)

Solar particle events constitute an important concern for space missions They may lead to effects seen in microelectronics or damage to solar cells and constitute a potential hazard for manned missions In order to estimate the risk related to mission integrated fluence a number of models have been developed which apply statistical analysis based on the collection of solar proton data from a variety of sources during the last few solar cycles Recent results have demonstrated the influence of assumptions and data caveats on these analyses This paper extends work done by Rosenqvist et al 2005 and Feynman et al 1990 1993 2002 to describe an updated engineering model for the proton interplanetary fluence with energies 1 4 30 and 60 MeV This model is derived from a public list of solar proton fluences based on inter-calibrated data from a number of sources covering almost 3 solar cycles References J Feynman T P Armstrong L Dao-Gibner and S Silverman A New Interplanetary Proton Fluence Model J Spacecraft and Rockets 27 403 1990 J Feynman G Spitale J Wang and S Gabriel Interplanetary proton fluence model JPL 1991 J Geophys Res 98 13281-13294 1993 J Feynman A Ruznaikin and V Berdichevsky The JPL proton fluence model an update J Atmos Solar-Terr Phys 64 1679-1686 2002 Rosenqvist L A Hilgers H Evans E Daly M Hapgood R Stamper and R Zwickl S Bourdarie and D Bosher A toolkit for updating interplanetary proton cumulated fluence models J Spacecraft and Rockets Vol 42

Glover, A.; Hilgers, A.; Rosenqvist, L.; Evans, H.

357

Dusty Plasma Effects in the Interplanetary Medium?  

NASA Astrophysics Data System (ADS)

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

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

358

Interplanetary energetic particle observations of the March 1989 events  

NASA Technical Reports Server (NTRS)

The IMP-8 spacecraft placed in an elongated orbit of approximately R(sub E) x R(sub E) orbit around the Earth was the only monitor of the energetic particle environment of the near interplanetary space during the period of the solar particle events associated with the Active Region 5395 in March 1989. Measurements of energetic ion and electron intensities were obtained in a series of channels within the energy range: 0.3 to 440 MeV for photons, 0.6 to 52 MeV/nuc for alpha particles, 0.7 to 3.3 MeV/nuc for nuclei with Z greater than or equal to 3, 3 to 9 MeV/nuc with Z greater than or equal to 20, and 0.2 to 2.5 MeV for electrons. The responses of selected energy channels during the period 5 to 23 March 1989 are displayed. It is clearly noted that the most prominent energetic ion intensity enhancements in that time interval were associated with the interplanetary shock wave of March 13 (07:42 UT) as well as that of March 8 (17:56 UT), which have distinct particle acceleration signatures. These shock waves play a major role in determining the near Earth energetic ion intensities during the above period by accelerating and modulating the ambient solar energetic particle population, which was already present in high intensities in the interplanetary medium due to the superposition of a series of solar flare particle events originating in AR 5395. The differential ion intensities at the lowest energy channel of the CPME experiment, which were associated with the March 13 shock wave, reached the highest level in the life of the IMP-8 spacecraft at this energy. At high energies, the shock associated intensity peak was smaller by less than a factor of 3 than the maxima of solar flare particle intensities from some other major flares, in particular from those with sites well connected to the Earth's magnetic flux tubes.

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

1989-01-01

359

CAWSES November 7-8, 2004, Superstorm: Complex Solar and Interplanetary Features in the Post-Solar Maximum Phase  

NASA Technical Reports Server (NTRS)

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 approx.4 nT to 44 nT. However, the fields after the shocks were northward, and magnetic storms did not result. The three ram pressure increases were associated with major sudden impulses (SI + s) at Earth. A magnetic cloud followed the third forward shock and the southward Bz associated with the latter was responsible for the superstorm. Two reverse waves were detected, one at the edge and one near the center of the magnetic cloud (MC). It is suspected that these 'waves' were once reverse shocks which were becoming evanescent when they propagated into the low plasma beta MC. The second reverse wave caused a decrease in the southward component of the IMF and initiated the storm recovery phase. It is determined that flares located at large longitudinal distances from the subsolar point were the most likely causes of the first two shocks without associated magnetic clouds. It is thus unlikely that the shocks were 'blast waves' or that magnetic reconnection eroded away the two associated MCs. This interplanetary/solar event is an example of the extremely complex magnetic storms which can occur in the post-solar maximum phase.

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

2008-01-01

360

Cancer Screening with Digital Mammography for Women at Average Risk for Breast Cancer, Magnetic Resonance Imaging (MRI) for Women at High Risk  

PubMed Central

Executive Summary Objective The purpose of this review is to determine the effectiveness of 2 separate modalities, digital mammography (DM) and magnetic resonance imaging (MRI), relative to film mammography (FM), in the screening of women asymptomatic for breast cancer. A third analysis assesses the effectiveness and safety of the combination of MRI plus mammography (MRI plus FM) in screening of women at high risk. An economic analysis was also conducted. Research Questions How does the sensitivity and specificity of DM compare to FM? How does the sensitivity and specificity of MRI compare to FM? How do the recall rates compare among these screening modalities, and what effect might this have on radiation exposure? What are the risks associated with radiation exposure? How does the sensitivity and specificity of the combination of MRI plus FM compare to either MRI or FM alone? What are the economic considerations? Clinical Need The effectiveness of FM with respect to breast cancer mortality in the screening of asymptomatic average- risk women over the age of 50 has been established. However, based on a Medical Advisory Secretariat review completed in March 2006, screening is not recommended for women between the ages of 40 and 49 years. Guidelines published by the Canadian Task Force on Preventive Care recommend mammography screening every 1 to 2 years for women aged 50 years and over, hence, the inclusion of such women in organized breast cancer screening programs. In addition to the uncertainty of the effectiveness of mammography screening from the age of 40 years, there is concern over the risks associated with mammographic screening for the 10 years between the ages of 40 and 49 years. The lack of effectiveness of mammography screening starting at the age of 40 years (with respect to breast cancer mortality) is based on the assumption that the ability to detect cancer decreases with increased breast tissue density. As breast density is highest in the premenopausal years (approximately 23% of postmenopausal and 53% of premenopausal women having at least 50% of the breast occupied by high density), mammography screening is not promoted in Canada nor in many other countries for women under the age of 50 at average risk for breast cancer. It is important to note, however, that screening of premenopausal women (i.e., younger than 50 years of age) at high risk for breast cancer by virtue of a family history of cancer or a known genetic predisposition (e.g., having tested positive for the breast cancer genes BRCA1 and/or BRCA2) is appropriate. Thus, this review will assess the effectiveness of breast cancer screening with modalities other than film mammography, specifically DM and MRI, for both pre/perimenopausal and postmenopausal age groups. International estimates of the epidemiology of breast cancer show that the incidence of breast cancer is increasing for all ages combined whereas mortality is decreasing, though at a slower rate. The observed decreases in mortality rates may be attributable to screening, in addition to advances in breast cancer therapy over time. Decreases in mortality attributable to screening may be a result of the earlier detection and treatment of invasive cancers, in addition to the increased detection of ductal carcinoma in situ (DCIS), of which certain subpathologies are less lethal. Evidence from the Surveillance, Epidemiology and End Results (better known as SEER) cancer registry in the United States, indicates that the age-adjusted incidence of DCIS has increased almost 10-fold over a 20 year period, from 2.7 to 25 per 100,000. There is a 4-fold lower incidence of breast cancer in the 40 to 49 year age group than in the 50 to 69 year age group (approximately 140 per 100,000 versus 500 per 100,000 women, respectively). The sensitivity of FM is also lower among younger women (approximately 75%) than for women aged over 50 years (approximately 85%). Specificity is approximately 80% for younger women versus 90% for women over 50 years. The increased density of breast tissue in younger women is l

2010-01-01

361

Prompt penetration electric fields (PPEFs) and their ionospheric effects during the great magnetic storm of 30–31 October 2003  

Microsoft Academic Search

We explore the ionospheric effects of prompt penetration electric fields (PPEFs) for a variety of interplanetary magnetic field directions. We use the great magnetic storm of 30–31 October as an example of PPEF effects. For intense southward interplanetary magnetic fields (IMFs), inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm. Concurrent

B. T. Tsurutani; O. P. Verkhoglyadova; A. J. Mannucci; A. Saito; T. Araki; K. Yumoto; T. Tsuda; M. A. Abdu; J. H. A. Sobral; W. D. Gonzalez; H. McCreadie; G. S. Lakhina; V. M. Vasyli?nas

2008-01-01

362

A power spectral analysis of turbulence associated with interplanetary shock waves  

NASA Astrophysics Data System (ADS)

We calculate the power spectra densities of magnetic field fluctuations associated with interplanetary shock waves at 1AU, utilizing in-situ magnetic field measurements from spacecraft ACE and Wind. We derive related quantities both upstream and downstream of a shock as a function of time/distance away from the shock passage. We present results for a few events that exhibit clear upstream enhanced wave activity. We show that mostly they are of Alfvénic nature and confined within certain distance upstream. We also present a preliminary analysis of turbulence-particle interaction based on spectral analysis results. Implications of such analysis to turbulence transport models are also discussed.

Hu, Qiang; Zank, Gary P.; Li, Gang; Ao, Xianzhi

2013-06-01

363

Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook Spacecraft Anomalies: An Update  

E-print Network

Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook / 29 Spacecraft Anomalies: An Update #12;Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook Overview 1 Interplanetary Spaceflight Swing-by Deep Space Network

Aste, Andreas

364

Galactic cosmic ray modulation and interplanetary medium perturbations due to a long-living active region during October 1989  

NASA Technical Reports Server (NTRS)

During October 1989, three very energetic flares were ejected by the same active region at longitudes 9 deg E, 32 deg W, and 57 deg W, respectively. The shape of the galactic cosmic ray variations suggests the presence of large magnetic cloud structures (Nagashima et al., 1990) following the shock-associated perturbations. In spite of long data gaps the interplanetary observations at Interplanetary Monitoring Platform (IMP) 8 (near the Earth) and International Cometary Explorer (ICE)(approximately 1 AU, approximately 65 deg W) confirm this possibility for the event related to the 9 deg E flare; the principal axes analysis shows that the interplanetary magnetic field variations at both spacecraft locations are mainly confined on a meridian plane. This result suggests that the western longitudinal extension of this cloud is indeed very large (greater than or equal to 5 deg). The nonnegligible depression in the cosmic ray intensity observed inside the possible cloud related to the 57 deg W flare indicates that also the eastern extension could be very wide. The analysis of neutron monitor data shows clearly the cosmic ray trapping effect of magnetic clouds; this mechanism seems to be responsible for the enhanced diurnal effect often observed during the recovery phase of Forbush decreases. We give an interpretation for the anisotropic cosmic ray peak occurring in the third event, and, related to that, we suggest that the Forbush decrease modulated region at the Earth's orbit could be somewhat wider than the magnetic cloud, as already anticipated by Nagashima et al. (1990). By this analysis, based mainly on cosmic ray data, we show that it is possible to do reasonable inferences on the large-scale structure of flare-related interplanetary perturbations when interplanetary medium data are not completely present.

Bavassano, B.; Iucci, N.; Lepping, R. P.; Signorini, C.; Smith, E. J.; Villoresi, G.

1994-01-01

365

Direct observations of higher frequency density fluctuations in the interplanetary plasma  

NASA Technical Reports Server (NTRS)

Direct observations from the plasma spectrometers on Pioneer 6 at 1 AU in December, 1965, have been used to obtain the power associated with fluctuations in the number density of solar-wind protons in the frequency range from .001 to .01 Hz. A power-law spectrum is obtained in this frequency range. The extension of the power-law density spectrum based on direct observations to these higher frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations and with the dominance of large-scale turbulence in the solar wind. This result is also consistent with direct observations of the solar-wind proton speed and the interplanetary magnetic field.

Intriligator, D. S.

1975-01-01

366

Forecast of the arrival of interplanetary shocks by measuring cosmic ray fluctuations in the interplanetary  

E-print Network

interplanetary shocks, for which a large flux of low-energy particles (10 keV - 10 MeV) of solar It is statistically shown that Space Weather events, caused by bursts of solar activity, may affect the frequency cosmic ray fluctuations and solar wind parameters measured onboard the ACE spacecraft. The method

Usoskin, Ilya G.

367

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

368

Problems of Interplanetary and Interstellar Trade  

NASA Astrophysics Data System (ADS)

If and when interplanetary and interstellar trade develops, it will be novel in two respects. First, the distances and time spans involved will reduce all or nearly all trade to the exchange of intangible goods. That threatens the possibility of conducting business in a genuinely common currency and of enforcing debt agreements, especially those involving sovereign debt. Second, interstellar trade suggests trade between humans and aliens. Cultural distance is a probable obstacle to initiating and sustaining such trade. Such exchange also threatens the release of new and potentially toxic memes.

Hickman, John

2008-01-01

369

Case Studies of Interplanetary Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

We contrast the solar wind characteristics and origins for typical and extreme ICME cases using STEREO data. This past solar minimum was characterized by weak transients. In contrast the rise of the cycle included extremely fast interplanetary coronal mass ejections, with one such ICME observed in situ by STEREO A exceeding 1500 km/s at 1 AU. We will compare specific cases of slow and fast ICME solar wind observed in situ by STEREO to general solar wind ion parameters, particularly for proton, helium and iron ions.

Galvin, Antoinette B.; Simunac, Kristin; Farrugia, Charles

2014-06-01

370

Simulation of solar flare particle interaction with interplanetary shock waves  

Microsoft Academic Search

In order to study the propagation of solar cosmic rays in interplanetary space a computer program has been developed using a Monte-Carlo technique, which traces the histories of particles released impulsively at the Sun. The particle propagation model considers the adiabatic deceleration during the convective and diffusive transport of the particles, and the model of the interplanetary medium incorporates a

M. Scholer; G. Morfill

1975-01-01

371

Constraints on the average magnetic field strength of relic radio sources 0917+75 and 1401-33 from XMM-Newton observations  

E-print Network

We observed two relic radio sources, 0917+75 and 1401-33, with the XMM-Newton X-ray observatory. We did not detect any X-ray emission, thermal or non-thermal, in excess of the local background level from either target. This imposes new upper limits on the X-ray flux due to inverse Compton scattering of photons from the cosmic microwave background by relativistic electrons in the relic sources, and new lower limits on the magnetic field strength from the relative strength of the radio and X-ray emission. The combination of radio and X-ray observations provides a measure of the magnetic field independent of equipartition or minimum energy assumptions. Due to increasing sensitivity of radio observations, the known population of cluster relics has been growing; however, studies of non-thermal X-ray emission from relics remain scarce. Our study adds to the small sample of relics studied in X-rays. In both relics, our field strength lower limits are slightly larger than estimates of the equipartition magnetic field.

C. M. Hubert Chen; D. E. Harris; Fiona A. Harrison; Peter H. Mao

2008-01-01

372

Cosmic ray decreases caused by interplanetary shocks observed by the Brazilian Southern Space Observatory's Multidirectional Muon Detector  

NASA Astrophysics Data System (ADS)

The space between the planets in the Solar System is continuously permeated by the supermagnetosonic expansion of the solar atmosphere - the solar wind. This is a magnetized plasma that carries outward the sun’s magnetic field. Furthermore, the Sun’s sporadically emits huge coronal mass ejections (CMEs) that disturb the solar wind. When the interplanetary remnants of these CMEs are faster than the local plasma magnetosonic wave speed, shock waves are driven. These shock waves are observed as abrupt variations in solar wind plasma and magnetic field parameters. As one consequence, when these shock waves pass by Earth, cosmic ray decreases are observed by ground based cosmic ray detectors. It is the aim of this work to study interplanetary shock waves effects on cosmic rays measured at ground level. Interplanetary shocks are identified and their parameters determined using the plasma and magnetic field instruments of the Advanced Composition Explorer (ACE). Cosmic rays decreases are studied using the Multidirectional Muon Detector (MMD), in operation at the Southern Space Observatory - SSO/CRS/INPE-MCTI, in São Martinho da Serra, RS, Southern Brazil. The period of analysis is from January 2006 to July 2011. In this study it is calculated the shock strength, the magnetic field and plasma density compression ratio across the shocks. Besides, the cosmic ray decrease due to the shocks is determined. Further, the amplitude of cosmic ray decreases is correlated to the shock strength. The results are compared with previous published works.

Deggeroni, Vinicíus; Echer, Ezequiel; Schuch, Nelson Jorge; Dal Lago, Alisson; Da Silva, Marlos; Bremm, Tiago

373

Coherent radar estimates of average high-latitude ionospheric Joule heating  

SciTech Connect

The Scandinavian Twin Auroral Radar Experiment (STARE) and Sweden and Britain Radar Experiment (SABRE) bistatic coherent radar systems have been employed to estimate the spatial and temporal variation of the ionospheric Joule heating in the combined geographic latitude range 63.8 deg - 72.6 deg (corrected geomagnetic latitude 61.5 deg - 69.3 deg) over Scandinavia. The 173 days of good observations with all four radars have been analyzed during the period 1982 to 1986 to estimate the average ionospheric electric field versus time and latitude. The AE dependent empirical model of ionospheric Pedersen conductivity of Spiro et al. (1982) has been used to calculate the Joule heating. The latitudinal and diurnal variation of Joule heating as well as the estimated mean hemispherical heating of 1.7 x 10(exp 11) W are in good agreement with earlier results. Average Joule heating was found to vary linearly with the AE, AU, and AL indices and as a second-order power law with Kp. The average Joule heating was also examined as a function of the direction and magnitude of the interplanetary magnetic field. It has been shown for the first time that the ionospheric electric field magnitude as well as the Joule heating increase with increasingly negative (southward) Bz.

Kosch, M.J.; Nielsen, E. [Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany)

1995-07-01

374

The CME-ICME Connection and Interplanetary Structure During Solar Minimum  

NASA Astrophysics Data System (ADS)

When an interplanetary transient (ICME) exhibits a large angle and smooth rotation in the IMF vector, it is classified as a magnetic cloud (MC) and commonly interpreted as the signature of a magnetic flux rope. On the average bout a third of ICME ejecta are MCs, although the fraction seems to be larger during the quiet phase of the solar cycle. Non-flux rope ICMEs are likely (1) distorted during the transit through heliosphere, (2) observed at an unfavorable crossing angle if the ICME structure has spatial variation, (3) or are simply have a more complex internal structure. Five Magnetic Clouds (MC) have been found from a total of nine ICMEs observed during 2007 January 01 to 2008 August 31, when the separation of STEREO A (STA) and B (STB) spacecraft varied between 0.05 to 70.35 degrees heliolongitude. We investigate the four best MCs using observations from three spacecraft (STA, STB and ACE). The first MC seems to have been detected by all three spacecraft (STA and STB 40.4 degrees apart), while the latter three were detected by only one of the STEREO spacecraft and sometimes by ACE. From the inferred flux rope orientation at each crossing and the spatial variation of the ICME properties, we interpret how each MC flux rope was situated relative to the spacecraft, and its connection to the Sun from corresponding coronal and heliospheric modeling results. Each of the MCs can be associated at low confidence (in contrary to expectations for solar minimum time) with a CME observed by coronagraphs on board STEREO and/or SOHO. All potential parent CMEs were very slow in the 200 km/s range (plane-of-sky), but the speeds of the MCs were between ~390 and ~480 km/s, indicating acceleration in the heliosphere. Solar disk activities are minor around the four CMEs, with no GOES x-ray flares, and two possibly associated filament eruptions. Some CME structures appear to form in the coronagraph field of view rather than rising from below. Several low/mid- latitude coronal holes and a highly warped coronal streamer arcade and source surface neutral line dominate the coronal structure during the period of the study. Previous studies have shown that the MC fluxrope orientation may be aligned with the large-scale coronal streamer arcades. Estimated MC orientations are discussed and compared with events during the previous solar minimum, which exhibited a more dipolar coronal structure. This work was supported, in part, by NASA NNG06GE51G, NNX08AJ04G, and NAS5-03131.

Li, Y.; Lynch, B. J.; Luhmann, J. G.; Kilpua, E.; Toy, V.; Vourlidas, A.; Russell, C. T.; Galvin, A. B.

2008-12-01

375

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

376

Comment on 'Observations of reconnection of interplanetary and lobe magnetic field lines at the high-latitude magnetopause' by J.T. Gosling, M.F. Thomsen, S.J. Bame, R.C. Elphic, and C.T. Russell  

NASA Technical Reports Server (NTRS)

Comment is presented on the results of measurements, reported by Gosling et al. (1991), that were made on ISEE in the vicinity of the high-latitude dusk magnetopause near the terminator plane, at a time when the local magnetosheath and tail lobe magnetic fields were nearly oppositely directed. The character of the observed plasma flowing both tailward and sunward within the high-latitude magnetopause current layer presented real evidence for the local reconnection process. Gosling et al. argued that this process may be a manifestation of different global magnetospheric topology structures. In the comment, a global magnetospheric convection pattern is constructed for the northward IMF and for the case of a large azimuthal component of the IMF with small Bz, irrespective of its sign. The suggested scheme provides a simple explanation for the observed sunward convection in the polar caps both for the northward and for strong By with small Bz. According to the present model, for the magnetosheath field at 2300 UT on June 11, 1978, the reconnection between the open field lines appears at the northern neutral point.

Belen'kaia, Elena

1993-01-01

377

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

NASA Technical Reports Server (NTRS)

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

1984-01-01

378

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

379

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

380

On the complex state of the interplanetary medium of 28-29 July 1977  

NASA Technical Reports Server (NTRS)

Observations of plasma and magnetic field variations in the near-Earth solar wind are discussed. Both a corotating stream and a driven shock are present. The driver gas seems to be enveloped in the rising speed phase of this stream; this appearance is attributed to a convoluted surface separating the two plasma domains. The magnetic field in the post shock flow (0030-1230 UT of July 29) has a large and geoeffective southward component at times; the energy coupling coefficient reaches approximately 5.4 x 10 to the 19th power ergs/s. In the driver gas (1230 UT of July 29 to 0110 of July 30) the magnetic field is dominantly northward. The density and dynamic pressure decrease by almost two orders of magnitude (100 to 2 cm/3) from just behind the interplanetary shock to approximately 3 hours into the driver gas flow. The dominant magnetic field variation in the driver gas is modeled by a cloud-like structure. Significant plasma parameter variations within the driver gas are attributed to structure in the parent solar mass ejection event and to interplanetary kinematics.

King, J. H.; Lepping, R. P.; Sullivan, J. D.

1981-01-01

381

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

SciTech Connect

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 >approx.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. The example of bi-directional streaming clearly cannot be explained by field line connection to either the earth's bow shock or the outward propagating interplanetary shock which passed ISEE 3 approx.16 hours earlier. The event is best explained if the local interplanetary field was a part of either 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.

1981-02-01

382

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

383

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

384

PARTICLE ENERGY SPECTRA AT TRAVELING INTERPLANETARY SHOCK WAVES  

SciTech Connect

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

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

2012-09-20

385

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

386

The accretion of interplanetary dust by Ap and Am stars  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

387

MIDACO software performance on interplanetary trajectory benchmarks  

NASA Astrophysics Data System (ADS)

A numerical study of the MIDACO optimization software on the well known GTOP benchmark set, published by the European Space Agency (ESA), is presented. The GTOP database provides trajectory models of real-world interplanetary space missions such as Cassini, Messenger or Rosetta. The trajectory models are formulated as constrained nonlinear optimization problems and are known to be difficult to solve. Here a comprehensive and rigorous numerical analysis of the MIDACO out-of-the-box performance on the GTOP benchmark set is presented and discussed. In the past, the putative best known solutions of these benchmarks often required several months and even years to be found. In this contribution it will be shown, that MIDACO is able to solve five out of seven of these benchmarks to their best known solution within minutes to hours.

Schlueter, Martin

2014-08-01

388

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

389

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

390

IRAS observations of the interplanetary dust emission  

NASA Astrophysics Data System (ADS)

The Infrared Astronomical Satellite (IRAS) has completed a sensitive, highly redundant survey of the full sky in four broad photometric bands at 12, 25, 60, and 100 micrometers wavelength. The survey measured interplanetary dust emission over elongation angles ranging from 60 to 120 degrees. Bright emission from the main cloud is consistent with optically thin blackbody emission. The grains are evidently quite black, with an "apparent albedo" of about 0.07. The data show clear evidence for deviation of the dust symmetry surface from the ecliptic plane. Surprising bands of emission were discovered near the ecliptic plane and about ten degrees on either side of it. The heliocentric distance of this material, suggested to be asteroidal in origin, is inferred to be about 2.5 AU from both color temperature and parallax measurements.

Hauser, M. G.; Gautier, T. N.; Good, J.; Low, F. J.

391

Infrared Spectroscopy of Anhydrous Interplanetary Dust Particles  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

392

Mars Odyssey Joins The Third Interplanetary Network  

E-print Network

The Mars Odyssey spacecraft carries two experiments which are capable of detecting cosmic gamma-ray bursts and soft gamma repeaters. Since April 2001 they have detected over 275 bursts and, in conjunction with the other spacecraft of the interplanetary network, localized many of them rapidly and precisely enough to allow sensitive multi-wavelength counterpart searches. We present the Mars Odyssey mission and describe the burst capabilities of the two experiments in detail. We explain how the spacecraft timing and ephemeris have been verified in-flight using bursts from objects whose precise positions are known by other means. Finally, we show several examples of localizations and discuss future plans for the Odyssey mission and the network as a whole.

K. Hurley; I. Mitrofanov; A. Kozyrev; M. Litvak; A. Sanin; V. Grinkov; S. Charyshnikov; W. Boynton; C. Fellows; K. Harshman; D. Hamara; C. Shinohara; R. Starr; T. Cline

2005-08-17

393

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

394

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

395

On modeling flux rope-type small interplanetary transients by non-force free methods  

NASA Astrophysics Data System (ADS)

Small interplanetary transients can have the geometry of magnetic flux ropes. We show examples of these taken from STEREO and WIND observations. We then model these examples using techniques which do not assume a force-free state. We do this because past work (Wenyuan et al., 2014) has shown statistically over large samples that the plasma beta (proton plus electron) can be of order unity. We use two methods, one analytical and one based on Grad-Shafranov reconstruction. We then discuss the results obtained from this least-squares fitting approach in the context of a comparison with what one would obtain from a linear force-free algorithm (Lundquist solution).

Yu, Wenyuan; Luhmann, Janet G.; Farrugia, Charles; Moestl, Christian; Leitner, Martin; Galvin, Antoinette; Sonnerup, Bengt; Lugaz, Noé

396

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

NASA Astrophysics Data System (ADS)

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

Troshichev, Oleg; Smirnov, Michael

397

Variation of Solar, Interplanetary and Geomagnetic Parameters during Solar Cycles 21-24  

NASA Astrophysics Data System (ADS)

The length of solar cycle 23 has been prolonged up to about 13 years. Many studies have speculated that the solar cycle 23/24 minimum will indicate the onset of a grand minimum of solar activity, such as the Maunder Minimum. We check the trends of solar (sunspot number, solar magnetic fields, total solar irradiance, solar radio flux, and frequency of solar X-ray flare), interplanetary (interplanetary magnetic field, solar wind and galactic cosmic ray intensity), and geomagnetic (Ap index) parameters (SIG parameters) during solar cycles 21-24. Most SIG parameters during the period of the solar cycle 23/24 minimum have remarkably low values. Since the 1970s, the space environment has been monitored by ground observatories and satellites. Such prevalently low values of SIG parameters have never been seen. We suggest that these unprecedented conditions of SIG parameters originate from the weakened solar magnetic fields. Meanwhile, the deep 23/24 solar cycle minimum might be the portent of a grand minimum in which the global mean temperature of the lower atmosphere is as low as in the period of Dalton or Maunder minimum.

Oh, Suyeon; Kim, Bogyeong

2013-06-01

398

Numerical simulations of solar disturbances and their interplanetary consequences  

NASA Technical Reports Server (NTRS)

Time-dependent MHD numerical simulations are used to study responses of the solar atmosphere and interplanetary medium to simulated solar disturbances. A number of 2D and 3D examples of coronal mass ejection (CME) simulations and some current controversies concerning the basic processes of CME initiation are discussed. Footpoint shearing motion is tested to determine whether it can provide a reasonable mechanism for CME development from arch filament configurations. Possible interplanetary consequences to CME-like disturbances are demonstrated by using 3D simulations to determine the dynamic response of the solar wind to a plasmoid injection from an eruptive filament or prominence. The possibility that a plasmoid may be generated in the interplanetary medium by a solar-generated shock that propagates through a heliospheric current sheet is discussed. Application of the 3D model for the interpretation of interplanetary scintillation observations is addressed.

Dryer, M.; Wu, S. T.; Detman, T. R.

1990-01-01

399

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

400

Designing An Interplanetary Autonomous Spacecraft Navigation System Using Visible Planets.  

E-print Network

??A perfect duality exists between the problem of space-based orbit determination from line-of-sight measurements and the problem of designing an interplanetary autonomous navigation system. Mathematically,… (more)

Karimi, Reza

2012-01-01

401

Hybrid methods for interplanetary low-thrust trajectory optimization  

E-print Network

Hybrid methods for interplanetary low-thrust trajectory optimization are proposed. These methods are combinations of selected, existing methods for trajectory optimization. The focus of this thesis is to obtain solutions to a class of trajectories...

Aroonwilairut, Krisada

2012-06-07

402

Zodiacal light as an indicator of interplanetary dust  

NASA Technical Reports Server (NTRS)

The most striking feature of the night sky in the tropics is the zodiacal light, which appears as a cone in the west after sunset and in the east before sunrise. It is caused by sunlight scattered or absorbed by particles in the interplanetary medium. The zodiacal light is the only source of information about the integrated properties of the whole ensemble of interplanetary dust. The brightness and polarization in different directions and at different colors can provide information on the optical properties and spatial distribution of the scattering particles. The zodiacal light arises from two independent physical processes related to the scattering of solar continuum radiation by interplanetary dust and to thermal emission which arises from solar radiation that is absorbed by interplanetary dust and reemitted mainly at infrared wavelengths. Attention is given to observational parameters of zodiacal light, the methods of observation, errors and absolute calibration, and the observed characteristics of zodiacal light.

Weinberg, J. L.; Sparrow, J. G.

1978-01-01

403

A time-averaged cosmic ray propagation theory  

NASA Technical Reports Server (NTRS)

An argument is presented, which casts doubt on our ability to choose an appropriate magnetic field ensemble for computing the average behavior of cosmic ray particles. An alternate procedure, using time-averages rather than ensemble-averages, is presented.

Klimas, A. J.; Sandri, G.

1975-01-01

404

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

405

The quiet solar wind. [proton and magnetic properties  

NASA Technical Reports Server (NTRS)

Data from nine spacecraft are combined to study the properties of solar wind protons and the interplanetary magnetic field under unusual conditions that proton speed, density, and temperature variations are small over periods comparable to the solar wind expansion time. From the 14 quiet intervals studied it is determined that (1) the square root of T versus velocity relation is less steep than was calculated from long-term-averaged or 3-hour quiet data; (2) the density varies approximately as the inverse square of the velocity; however, the data scatter is large, and an alternative interpretation is that mass flux is constant for velocities over about 400 km/s, in agreement with earlier studies; (3) the magnitude of the interplanetary magnetic field is independent of solar wind speed and density; and (4) the average field direction varies with the solar wind speed as predicted by Parker's spiral model. The intercalibration of solar wind measurements by different spacecraft is discussed in an appendix.

Neugebauer, M.

1976-01-01

406

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

407

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

408

Mars interplanetary trajectory design via Lagrangian points  

NASA Astrophysics Data System (ADS)

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

Eapen, Roshan Thomas; Sharma, Ram Krishan

2014-09-01

409

Mars Science Laboratory Interplanetary Navigation Analysis  

NASA Technical Reports Server (NTRS)

The Mars Science Laboratory (MSL) is a NASA rover mission that will be launched in late 2011 and will land on Mars in August of 2012. This paper describes the analyses performed to validate the navigation system for launch, interplanetary cruise, and approach. MSL will use guidance during its descent into Mars in order to minimize landing dispersions, and therefore will be able to use smaller landing zones that are closer to terrain of high scientific interest. This will require a more accurate delivery of the spacecraft to the atmospheric entry interface, and a late update of the state of the spacecraft at entry. During cruise and approach the spacecraft may perform up to six trajectory correction maneuvers (TCMs), to target to the desired landing site with the required flight path angle at entry. Approach orbit determination covariance analyses have been performed to evaluate the accuracy that can be achieved in delivering the spacecraft to the entry interface point, and to determine how accurately the state of the spacecraft can be predicted to initialize the guidance algorithm. In addition, a sensitivity analysis has been performed to evaluate which factors most contribute to the improvement or degradation of the navigation performance, for both entry flight path angle delivery and entry state knowledge.

Martin-Mur, Tomas J.; Kruizinga, Gerard L.; Wong, Mau C.

2011-01-01

410

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

411

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

412

Prediction of DC magnetic fields for magnetic cleanliness on spacecraft  

Microsoft Academic Search

Magnetometry is among the most used techniques in space exploration, e.g. to study complex plasma interactions between the solar wind and the Earth's magnetosphere, to map the planetary or interplanetary magnetic fields, or to retrieve information about the structural composition of planets. The success of each mission relies on the attainment of an adequate level of magnetic cleanliness at the

Axel Junge; Filippo Marliani

2011-01-01

413

Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms  

NASA Technical Reports Server (NTRS)

We have examined the ISEE 3 distant tail data during three intense magnetic storms and have identified the tail response to high-speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms.

Ho, C. M.; Tsurutani, B. T.

1997-01-01

414

(abstract) The Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms  

NASA Technical Reports Server (NTRS)

We have examined the ISEE-3 distant tail data during three intense magnetic storms and have identified the tail response to high speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms.

Ho, C. M.; Tsurutani, B. T.

1996-01-01

415

Great magnetic storms  

NASA Technical Reports Server (NTRS)

The five largest magnetic storms that occurred between 1971 to 1986 are studied to determine their solar and interplanetary causes. All of the events are found to be associated with high speed solar wind streams led by collisionless shocks. The high speed streams are clearly related to identifiable solar flares. It is found that: (1) it is the extreme values of the southward interplanetary magnetic fields rather than solar wind speeds that are the primary causes of great magnetic storms, (2) shocked and draped sheath fields preceding the driver gas (magnetic cloud) are at least as effective in causing the onset of great magnetic storms (3 of 5 events) as the strong fields within the driver gas itself, and (3) precursor southward fields ahead of the high speed streams allow the shock compression mechanism (item 2) to be particularly geoeffective.

Tsurutani, Bruce T.; Lee, Yen T.; Gonzalez, Walter D.; Tang, Frances

1992-01-01

416

Great magnetic storms  

SciTech Connect

The five largest magnetic storms that occurred between 1971 and 1986 are studied to determine their solar and interplanetary causes. All of the events are found to be associated with high speed solar wind streams led by collisionless shocks. The high speed streams are clearly related to identifiable solar flares. It is found that (1) it is the extreme values of the southward interplanetary magnetic fields rather than solar wind speeds that are the primary causes of great magnetic storms, (2) shocked and draped sheath fields preceding the driver gas (magnetic cloud) are at least as effective in causing the onset of great magnetic storms (3 of 5 events ) as the strong fields within the driver gas itself, and (3) precursor southward fields ahead of the high speed streams allow the shock compression mechanism (item 2) to be particularly geoeffective.

Tsurutani, B.T.; Yen Te Lee; Tang, F. (California Inst. of Tech., Pasadena, CA (United States)); Gonzalez, W.D.

1992-01-03

417

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

418

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

419

Great magnetic storms  

Microsoft Academic Search

The five largest magnetic storms that occurred between 1971 and 1986 are studied to determine their solar and interplanetary causes. All of the events are found to be associated with high speed solar wind streams led by collisionless shocks. The high speed streams are clearly related to identifiable solar flares. It is found that (1) it is the extreme values

Bruce T. Tsurutani; Yen Te Lee; Frances Tang; W. D. Gonzalez

1992-01-01

420

Interplanetary gas. XXVIII - A study of the three-dimensional properties of interplanetary sector boundaries using disconnection events in cometary plasma tails  

NASA Technical Reports Server (NTRS)

Studies of the solar wind on the basis of cometary plasma tail observations are considered. Niedner and Brandt (1978, 1979) have concluded that the plasma tail frequently disconnects from the cometary head, and that these disconnection events (DEs) are produced by magnetic reconnection at sector boundary passages. They proposed that the disconnections are a natural combination of Alfven's model and the solar-wind sector structure first discovered by Wilcox and Ness (1965). The DEs can be utilized as probes of interplanetary sector structure. Correlations between DEs and sector boundaries obs