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1

THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

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

V. A. BAILEY

1963-01-01

2

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

3

Interplanetary magnetic-sector structure, 1926 - 1971  

Microsoft Academic Search

Geomagnetic effects related to the interplanetary magnetic field. A relation between the polarity of the interplanetary magnetic field and the type of diurnal variation of the geomagnetic field inside the polar cap has been discovered independently by Svalgaard [1968], Mansurov [1969], and Mansurov and Mansurova [1970] and noted by Iwasaki [1971]. The relationship has been confirmed by FriisChristensen et al.

L. Svalgaard

1972-01-01

4

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

5

Intermittent character of interplanetary magnetic field fluctuations  

SciTech Connect

Interplanetary magnetic field magnitude fluctuations are notoriously more intermittent than velocity fluctuations in both fast and slow wind. This behavior has been interpreted in terms of the anomalous scaling observed in passive scalars in fully developed hydrodynamic turbulence. In this paper, the strong intermittent nature of the interplanetary magnetic field is briefly discussed comparing results performed during different phases of the solar cycle. The scaling properties of the interplanetary magnetic field magnitude show solar cycle variation that can be distinguished in the scaling exponents revealed by structure functions. The scaling exponents observed around the solar maximum coincide, within the errors, to those measured for passive scalars in hydrodynamic turbulence. However, it is also found that the values are not universal in the sense that the solar cycle variation may be reflected in dependence on the structure of the velocity field.

Bruno, Roberto; Carbone, Vincenzo; Chapman, Sandra; Hnat, Bogdan; Noullez, Alain; Sorriso-Valvo, Luca [IFSI/INAF, via Fosso del Cavaliere, I-00133 Rome (Italy); Dipartimento di Fisica, Universita della Calabria, and CNISM, Unita di Cosenza, Arcavacata di Rende I-87036 (Italy); Centre for Fusion, Space and Astrophysics, University of Warwick, Warwick CV4 7AL (United Kingdom); Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F-06304 Nice (France); LICRYL, INFM/CNR, I-87036 Arcavacata di Rende (Italy)

2007-03-15

6

Periodicities in the Interplanetary Magnetic Field Polarity.  

National Technical Information Service (NTIS)

The daily data of the polarity of the interplanetary magnetic field for the years 1926 to 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 recurrence in those str...

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

1985-01-01

7

Periodicities in the Interplanetary Magnetic Field Polarity.  

National Technical Information Service (NTIS)

A spectrum analysis for daily values of the interplanetary magnetic field observed and inferred from 1947 to 1976 shows a dominant peak with a period of about that of the solar rotation indicating that sector patterns live long enough for this modulation ...

W. D. Gonzalez-Alarcon A. L. C. Gonzalez

1979-01-01

8

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

9

Magnetic shielding for interplanetary spacecraft  

SciTech Connect

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

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

1991-12-01

10

Magnetic shielding for interplanetary spacecraft  

SciTech Connect

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

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

1991-01-01

11

Dynamics of Magnetic Clouds in Interplanetary Space (abstract only).  

National Technical Information Service (NTIS)

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 field...

T. Yeh

1987-01-01

12

Fractal structure of the interplanetary magnetic field  

SciTech Connect

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.

1985-05-01

13

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations were observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions. Magnetic field variations near the

K. W. Behannon

1977-01-01

14

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided and are continuing to provide extensive observations of the variations of the interplanetary magnetic field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations are observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions.

Kenneth W. Behannon

1978-01-01

15

Heliocentric Distance Dependence of the Interplanetary Magnetic Field.  

National Technical Information Service (NTIS)

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations we...

K. W. Behannon

1977-01-01

16

Effects of interplanetary magnetic field z component and the solar wind dynamic pressure on the geosynchronous magnetic field  

Microsoft Academic Search

A study of the correlation of the geosynchronous magnetic field with interplanetary magnetic field (IMF) Bz and the solar wind dynamic pressure (Pd) is presented. Hourly averages of 5 years of GOES 6 and 6 years of GOES 7 observations are correlated with IMF Bz and Pd. As previously reported, increases in Pd enhance geosynchronous Bz on the dayside, most

Simon Wing; David G. Sibeck

1997-01-01

17

Periodicities in the interplanetary magnetic field polarity  

SciTech Connect

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 was observed, with amplitudes decreasing in that same order. However, for shorter intervals of time (of the order of 1 year) the resulting spectral distribution does not necessarily present the same characteristics, particularly concerning the relative power of the peaks at about 27.5 and 13.5 days. These results are interpreted, through a simulation with rectangular waves, as cases that correspond either to a to-sector or to a four-sector structure, when the dominant peak is that of about 27.5 or 13.5 days, respectively. Thus, by performing an annual survey of the data, it as found that there is a continuous change in the type of dominant structure, with intervals having a well-defined two-sector structure alternating with those having either a less defined structure or a well-defined four-sector structure. A further application of the power spectrum technique to this type of alternating variability in the dominant structures led to the conclusion that significant periodicities of about 3.7 and 1.5 years seem to exist in such a variability. These periodicities become important when compared to similar ones reported in studies of solar and geomagnetic activity.

Gonzalez, A.L.C.; Gonzalez, W.D. (Inst. de Pesquisas Espaciais, Sao Jose dos Campos, Sao Paulo (Brazil))

1987-05-01

18

Solar Cosmic Rays in a Regular InterPLANETARY Magnetic Field.  

National Technical Information Service (NTIS)

The theory of high-energy protons in a regular interplanetary magnetic field is extended to admit the strong heliocentric dependence of the interplanetary magnetic field strength, resulting in an event decay phase whose character is somewhat steeper than ...

S. M. Bennett

1965-01-01

19

PERTURBATIONS OF THE INTERPLANETARY MAGNETIC FIELD BY THE LUNAR WAKE  

Microsoft Academic Search

through the leeward riow, an. alternating pattern of magnitude increases and decreases is observed in the penumbra, while generally only an increase is observed in the umbra. Using a theoretical model of plasma flow due to Whang, a first-order solution of the perturbed interplanetary magnetic field is compared with observations. It is concluded that the perturbations can be partially explained

N. F. Ness; K. W. Behannon; H. E. Taylor; Y. C. Whang

1968-01-01

20

The spiral structure of the interplanetary magnetic field  

Microsoft Academic Search

We examine the Pioneer 10 data concerning the heliocentric radial variation of the interplanetary magnetic field. Incorporating the systematic increase in solar wind velocity observed during the mission leads to much improved agreement between the usual Parker Archimedean spiral and the data. The effects of correlations between short-period fluctuations of speed and azimuthal field are discussed and it is concluded

G. D. Parker; J. R. Jokipii

1976-01-01

21

The spiral structure of the interplanetary magnetic field  

Microsoft Academic Search

The Pioneer 10 data concerning the heliocentric radial variation of the interplanetary magnetic field are examined. Incorporating the systematic increase in solar wind velocity observed during the mission leads to much improved agreement between the usual Parker Archimedean spiral and the data. The effects of correlations between short-period fluctuations of speed and azimuthal field are discussed. It is concluded that

G. D. Parker; J. R. Jokipii

1976-01-01

22

INTERPLANETARY MAGNETIC FLUX DEPLETION DURING PROTRACTED SOLAR MINIMA  

SciTech Connect

We examine near-Earth solar wind observations as assembled within the Omni data set over the past 15 years that constitute the latest solar cycle. We show that the interplanetary magnetic field continues to be depleted at low latitudes throughout the protracted solar minimum reaching levels below previously predicted minima. We obtain a rate of flux removal resulting in magnetic field reduction by 0.5 nT yr{sup -1} at 1 AU when averaged over the years 2005-2009 that reduces to 0.3 nT yr{sup -1} for 2007-2009. We show that the flux removal operates on field lines that follow the nominal Parker spiral orientation predicted for open field lines and are largely unassociated with recent ejecta. We argue that the field line reduction can only be accomplished by ongoing reconnection of nominally open field lines or very old closed field lines and we contend that these two interpretations are observationally equivalent and indistinguishable.

Connick, David E.; Smith, Charles W.; Schwadron, Nathan A., E-mail: davideconnick@gmail.com, E-mail: Charles.Smith@unh.edu, E-mail: N.Schwadron@unh.edu [Physics Department, Space Science Center, University of New Hampshire, Durham, NH (United States)

2011-01-20

23

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

24

Evolution of magnetic flux ropes associated with flux transfer events and interplanetary magnetic clouds  

Microsoft Academic Search

Spacecraft observations suggest that flux transfer events and interplanetary magnetic clouds may be associated with magnetic flux ropes which are magnetic flux tubes containing helical magnetic field lines. In the magnetic flux ropes, the azimuthal magnetic field is superposed on the axial field. The time evolution of a localized magnetic flux rope is studied. A two-dimensional compressible MHD simulation code

C. Q. Wei; L. C. Lee; S. Wang; S.-I. Akasofu

1991-01-01

25

Evolution of magnetic flux ropes associated with flux transfer events and interplanetary magnetic clouds  

Microsoft Academic Search

Spacecraft observations suggest that flux transfer events and interplanetary magnetic clouds may be associated with magnetic flux ropes which are magnetic flux tubes containing helical magnetic field lines. In the magnetic flux ropes, the azimuthal magnetic field (B{sub θ}) is superposed on the axial field (B{sub z}). In this paper the time evolution of a localized magnetic flux rope is

C. Q. Wei; L. C. Lee; S. Wang; S.-I. Akasofu

1991-01-01

26

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

27

Interplanetary shocks generated by expanding magnetic loops  

Microsoft Academic Search

We present a self-consistent numerical model of shock wave formation in the heliosphere by an expanding magnetic loop. In the model a coronal mass ejection is initiated by a loss of magnetohydrostatic equilibrium of the loop as a result of an increase of underlying magnetic field strength. The expanding magnetic loops produce propagating shock waves. The plasma motions are described

T. V. Stepanova; A. G. Kosovichev

1993-01-01

28

Recovery phase of magnetic storms induced by different interplanetary drivers  

NASA Astrophysics Data System (ADS)

Statistical analysis of Dstbehavior 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 (Dstmin ? -100 nT) magnetic storms are well approximated by hyperbolic functions Dst(t) = a/(1 + t/?h) with constant ?h times for each types of drivers while for moderate (-100 < Dstmin ? -50 nT) storms Dst profile can not be approximated by hyperbolic function with constant ?h times because hyperbolic ?h times increase with increasing time of recovery phase. Dependence of ?h times on types of interplanetary drivers is the same as indicated above. Relation between duration and value Dstmin for storms induced by MC and Sheath has 2 parts: module of Dstmin and duration correlate at small durations while they anticorrelate at large durations. Obtained results show that recovery phase Dst variations depend on type of interplanetary drivers inducing magnetic storms.

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

2012-08-01

29

Equatorial storm sudden commencements and interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Interplanetary (IP) shock signatures from interplanetary magnetic field (IMF) data gathered by the Explorer 33, 34 and 35 satellites were compared with H magnetograms associated with major sudden shock commencements (SC) from ground observatories within the equatorial electrojet belt (Huancayo, Addis Ababa and Trivandrum) during 1967-70. It is suggested that the SC in H at low latitudes are composed of two effects: one due to hydromagnetic pressure on the magnetosphere caused by the solar plasma, and the other due to the induced electric field associated with the solar wind velocity. The effect of the magnetospheric electric field is faster than the effect due to the compression of the magnetosphere by the impinging solar plasma.

Rastogi, R. G.

1980-10-01

30

Reconstruction of Open Solar Magnetic Flux and Interplanetary Magnetic Field in the 20Th Century  

Microsoft Academic Search

We reconstruct mean magnitudes of the open solar magnetic field since 1915 using ? magnetic synoptic charts of the Sun. The\\u000a obtained series allows estimation of the interplanetary magnetic field. They also confirm the known conclusion about the secular\\u000a increase of the solar open magnetic flux in the first half of the 20th century.

V. G. Ivanov; E. V. Miletsky

2004-01-01

31

CME and Reconnection Contributions to the Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

Examination of L1 magnetic field data from the recent solar minimum reveals evidence for ongoing magnetic reconnection below the Alfven critical point and throughout the recent protracted solar minimum. This ongoing reconnection permits both the ejection of open field lines from the heliosphere and the creation of new magnetic loops that are capable of subduction below the photosphere. At the same time, a theory can be developed based on related published ideas wherein CMEs contribute magnetic field to interplanetary space that, in time, become part of the observed open field line population. What seems most interesting is that (1) throughout the recent protracted solar minimum the IMF flux drops steadily and the apparent reconnection continues at a very steady rate, and (2) the field model can account for this observation by using reasonable parameters for ICME flux content and reconnection rates. We will also show our efforts to account for the interplanetary magnetic field during the rising phase of the solar cycle as CME flux injection is balanced against reduction by field line reconnection.

Connick, D.; Schwadron, N. A.; Smith, C. W.

2011-12-01

32

Substorms under northward interplanetary magnetic field: Statistical study  

NASA Astrophysics Data System (ADS)

It was recently noted that substorms can occur even under prolonged northward interplanetary magnetic field (IMF) conditions. Based on the substorm list obtained from the 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, are found within 30 min preceding 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. F.; Li, H.; Hu, Y. Q.; Du, J.

2013-01-01

33

Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9. 5 AU  

SciTech Connect

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

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

1984-04-01

34

Observations of a Small Interplanetary Magnetic Flux Rope Associated with a Magnetic Reconnection Exhaust  

Microsoft Academic Search

A small interplanetary magnetic flux rope prior to an X-line magnetic reconnection exhaust was observed on 1998 March 25 at 1 AU. The X-line magnetic reconnection exhaust has been identified and reported by Gosling et al. The duration of this small magnetic flux rope is about 2 hr. We fitted the constant alpha force-free model to the observed magnetic fields.

H. Q. Feng; D. J. Wu

2009-01-01

35

OBSERVATIONS OF A SMALL INTERPLANETARY MAGNETIC FLUX ROPE ASSOCIATED WITH A MAGNETIC RECONNECTION EXHAUST  

Microsoft Academic Search

A small interplanetary magnetic flux rope prior to an X-line magnetic reconnection exhaust was observed on 1998 March 25 at 1 AU. The X-line magnetic reconnection exhaust has been identified and reported by Gosling et al. The duration of this small magnetic flux rope is about 2 hr. We fitted the constant alpha force-free model to the observed magnetic fields.

H. Q. Feng; D. J. Wu

2009-01-01

36

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

37

Interplanetary Magnetic Sector Polarity Inferred from Polar Geomagnetic Field Observations.  

National Technical Information Service (NTIS)

In order to infer the interplanetary sector polarity from observations at Thule and Godhavn abs In order to infer the interplanetary sector polarity from polar geomagnetic field diurnal variations, measurements were carried out at Godhavn and Thule (Denma...

E. Friis-christensen K. Lassen J. M. Wilcox W. Gonzalez D. S. Colburn

1971-01-01

38

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

39

Interplanetary coronal mass ejection and ambient interplanetary magnetic field correlations during the Sun-Earth connection events of October–November 2003  

Microsoft Academic Search

Magnetic field observations made during 28 October to 1 November 2003, which included two fast interplanetary coronal mass ejections (ICMEs), allow a study of correlation lengths of magnetic field parameters for two types of interplanetary (IP) structures: ICMEs and ambient solar wind. Further, they permit the extension of such investigations to the magnetosheath and to a distance along the Sun-Earth

C. J. Farrugia; H. Matsui; H. Kucharek; R. B. Torbert; C. W. Smith; V. K. Jordanova; K. W. Ogilvie; R. P. Lepping; D. B. Berdichevsky; T. Terasawa; J. Kasper; T. Mukai; Y. Saito; R. Skoug

2005-01-01

40

Cusp latitude magnetic impulse events. 2. Interplanetary magnetic field and solar wind conditions  

SciTech Connect

The interplanetary magnetic field (IMF) conditions and solar wind plasma parameters prevailing during the magnetic impulse events identified by Lanzerotti et al. at the near cusp latitude stations Iqaluit, Canada, and South Pole Station, Antarctica, are examined. The impulse events are found to occur during periods of high IMF variability. The prevailing IMF orientation, averaged over 11-min periods during the events, shows no distinct anisotropies. However, by examining the IMF orientation when the IMF variability is small a south-east anisotropy is found. Examining the IMF orientation on timescales of less than 1 min reveals that the impulse events are characterized by a more southward oriented IMF than is to be expected statistically. The IMF B{sub y} control of the duration of nonconjugate events is in accordance with the effect expected from the presence of magnetic tension in a reconnection setting. The amplitude of the events is found to be strongly related to solar wind speed. It is concluded that a change in the solar wind dynamic pressure, while not among the primary mechanisms generating the magnetic impulse events, may account for between 15% and 30% of them. On the other hand, reconnection processes are able to produce impulse events of the required magnitude. It is argued then that magnetic reconnection is likely responsible for generating a minimum of 50%-70% to a maximum of 90% of the events. However, this conclusion leaves parts of the picture unclear. Lanzerotti et al. found that magnetic impulse events with a unipolar deflection in the vertical component of the magnetic field possessed a local time dependence; positive deflections occurred in local morning, while negative deflections occurred in local afternoon. This dependence can be explained by postulating that the magnetic impulse events are associated with vortices generated by the Kelvin-Helmholtz instability in the low-latitude boundary layer. 68 refs., 14 figs., 7 tabs.

Konik, R.M. [AT& T Bell Labs., Murray Hill, NJ (United States)]|[Cornell Univ., Ithaca, NY (United States); Lanzerotti, L.J. [AT& T Bell Labs., Murray Hill, NJ (United States); Wolfe, A. [AT& T Bell Labs., Murray Hill, NJ (United States)]|[City Univ. of New York, Brooklyn, NY (United States)] [and others

1994-08-01

41

Effects of the interplanetary conditions on the magnetic activity observed in the southern auroral zone  

NASA Astrophysics Data System (ADS)

The relationship between the interplanetary conditions and the magnetic activity recorded at Belgrano is examined. H-component magnetograms, rheometer records and the concurrent interplanetary data are used. It is found that the geomagnetic activity is generated by the combined effect of a variety of interplanetary conditions. The data distinctly show that each physical entity of the interplanetary medium has a specific and precise role in the development of active periods. The reversal of the IMF polarity appears to be the critical step in the generation of geomagnetic activity.

Cazeneuve, H. A.; Tabocchini, H.

1981-08-01

42

Inferring interplanetary magnetic field polarities from geomagnetic variations  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

43

Evidence linking coronal mass ejections with interplanetary magnetic clouds  

SciTech Connect

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.

1983-12-01

44

NOZOMI observation of transient, non-spiral magnetic field in interplanetary space associated with limb CMEs  

NASA Astrophysics Data System (ADS)

The magnetic fields of interplanetary objects that were ejected as coronal mass ejections (CMEs) from the limb of the Sun were observed by the NOZOMI spacecraft at 1.38 AU above the east limb of the Sun. The solar wind magnetic field whose launch time coincided with ejection of the limb CME was different from that estimated from ACE observations near the Earth, suggesting that NOZOMI encountered transient magnetic structures, or that the heliospheric magnetic field re-structured after ejection of the CMEs. The corresponding interplanetary magnetic field showed non-spiral magnetic field, enhancements of magnetic field, or magnetic discontinuities, but no common structure was yet found.

Nakagawa, T.; Matsuoka, A.

2003-09-01

45

Attitude stabilization of averaging magnetic torque  

Microsoft Academic Search

The stability problems of two magnetic control systems are discussed. One uses a three-axis magnetic actuator only; the other includes an additional momentum-biased wheel. The so-called orbit-averaged magnetic controllers, derived from the orbit-averaged magnetic field, show an ability to ensure the global attitude stabilization. This is supported theoretically by the averaging method and Lyapunov theories, and also illustrated by the

Lin Huang; Wuxing Jing

2006-01-01

46

Annual and Solar-Magnetic-Cycle Variations in the Interplanetary Magnetic Field, 1926-1971.  

National Technical Information Service (NTIS)

The polarity of the interplanetary magnetic field has been inferred by Svalgaard from observations of the polar geomagnetic field during the interval 1926-1971. On the basis of a few years of spacecraft observations Rosenberg and Coleman have suggested th...

J. M. Wilcox P. H. Scherrer

1972-01-01

47

Calculation of the interplanetary magnetic field based on its value in the solar photosphere  

Microsoft Academic Search

The difficulties associated with calculating the parameters of the interplanetary magnetic field (IMF) from solar magnetic\\u000a data have been considered. All conventional calculation patterns and available input databases have been analyzed from a unified\\u000a standpoint. It has been shown that these assumptions and limitations cannot affect the general structure and dependence on\\u000a cycle of solar and interplanetary data. At the

V. N. Obridko; B. D. Shelting; A. F. Kharshiladze

2006-01-01

48

Interplanetary small- and intermediate-sized magnetic flux ropes during 1995–2005  

Microsoft Academic Search

We present a comprehensive survey of 125 small- and intermediate-sized interplanetary magnetic flux ropes during solar cycle 23 (1995–2005) using Wind in situ observations near 1 AU. As a result, we found the following: (1) The annual number of small- and intermediate-sized interplanetary magnetic flux ropes is not very sensitive to the solar cycle, but its trend is very similar

H. Q. Feng; D. J. Wu; C. C. Lin; J. K. Chao; L. C. Lee; L. H. Lyu

2008-01-01

49

Why does the subsolar magnetopause move sunward for radial interplanetary magnetic field?  

NASA Astrophysics Data System (ADS)

This paper analyzes the distribution of different pressure components (dynamic, thermal, magnetic) in the magnetosheath along the Sun-Earth line for northward and radial interplanetary magnetic field (IMF) orientations with motivation to explain an unusual location and shape of the magnetopause often observed during the intervals of the radial IMF. The analysis employs isotropic and anisotropic MHD models, and their results are compared with the statistical processing of THEMIS observations. We have found that (1) the temperature anisotropy in the magnetosheath controls the pressure distribution near the magnetopause, and (2) the total pressure exerted on the subsolar magnetopause depends on the IMF orientation being significantly lower than the solar wind dynamic pressure for the radial IMF. The results of both MHD simulations and statistical investigations are quantitatively consistent with already published observations of the average magnetopause location as a function of the IMF orientation.

Samsonov, A. A.; N?me?ek, Z.; Šafránková, J.; Jelínek, K.

2012-05-01

50

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

51

PUZZLES OF THE INTERPLANETARY MAGNETIC FIELD IN THE INNER HELIOSPHERE  

SciTech Connect

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

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

2012-12-20

52

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

53

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

54

Equatorial electric fields during magnetically disturned conditions 1. The effect of the interplanetary magnetic field  

Microsoft Academic Search

Radar measurements of E and F region drift velocities have been used to look for correlations between changes in equatorial electric fields and the interplanetary magnetic field (IMF). The east-west component of the IMF appears to be unimportant, but the north-south component has some effect; rapid reversals from south to north are sometimes correlated with reversals of the equatorial east-west

B.G. Fejer; C.A. Gonzales; D.T. Farley; M.C. Kelley; R.F. Woodman

1979-01-01

55

Predicting Propagation Timing Delays in the Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

Experimental observations of solar wind-magnetosphere coupling processes and terrestrial "space weather" predictions rely heavily on measurements of the Interplanetary Magnetic Field (IMF) at the L1 orbit. Our previous investigation with simultaneous measurements of the IMF with four spacecraft at various locations (ACE, Wind, IMP-8, and Geotail) has found that the "phase front" of the fluctuations in IMF often is tilted at an angle. The tilt angle varies on a scale of minutes to tens of minutes. It had been shown that this tilting causes significant errors in the calculation of the propagation delay times from ACE to other locations, if they are determined only by the separation distance and solar wind velocity in the GSE X direction. Accurate timings depend on a knowledge of the orientation or tilt angle of the phase front plane, and this angle can vary significantly in a few hours or minutes. This orientation can be determined from simultaneous IMF measurements by three or more spacecraft, but this is not a practical method for routine operations when data from only one spacecraft at L1 are available, particularly in real time. This dilemma has led to the question of whether or not the phase plane orientation can be determined from a single satellite measurement alone. Recently it has been found that the "minimum variance" technique can be used to address this problem. Through the use of multiple-satellite measurements, the tilt angle and time delays that are determined by the minimum variance with just one satellite can be tested against the actual delays. It has been found that the success of this method is highly dependent on both the number of IMF measurements used for each calculation and on the rejection criteria for indeterminate results. Experimental tests of the optimal parameters for the minimum variance analysis and the quality of the plane determination will be presented.

Weimer, D. R.; Ober, D.; Maynard, N. C.; Burke, W. J.; Collier, M. R.; McComas, D. J.; Smith, C. W.

2001-12-01

56

A classification of dayside auroral forms and activities as a function of interplanetary magnetic field orientation  

Microsoft Academic Search

We present a classification of auroral forms in the dayside high-latitude ionosphere, based on ground observations from Svalbard. Having sorted the different auroral forms by magnetic local time (MLT) and morphological and optical spectral characteristics, we then study them as a function of the orientation of the interplanetary magnetic field (IMF). We find that the IMF clock angle theta is

Per Even Sandholt; Charles J. Farrugia; Jøran Moen; Øystein Noraberg; Bjørn Lybekk; Torleif Sten; Truls Hansen

1998-01-01

57

Interplanetary Magnetic Field Connection to the L1 Lagrangian Orbit During Upstream Energetic Ion Events  

Microsoft Academic Search

Energetic ions moving upstream from the Earth's bow shock frequently appear at the sunward Lagrangian (L1) point. The most common orientation of the interplanetary magnetic field (IMF) during these upstream events is near-radial from the sun (the nominal direction for connection to the magnetosphere). However, strong unidirectional beams of ions streaming away from Earth, consistent with good magnetic connection to

E. C. Roelof; C. W. Smith; N. F. Ness; R. M. Skoug; R. L. Tokar

2002-01-01

58

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

59

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

Microsoft Academic Search

We have reconstructed the interplanetary magnetic field (IMF), its radial component, and the open solar magnetic flux using the solar modulation potential derived from cosmogenic 10Be radionuclide data for a period covering the past 9300 years. Reconstructions using the assumption of both constant and variable solar wind speeds yielded closely similar results. During the Maunder Minimum, the strength of the

F. Steinhilber; J. A. Abreu; J. Beer; K. G. McCracken

2010-01-01

60

NOZOMI observation of transient, non-spiral magnetic field in interplanetary space associated with limb CMEs  

Microsoft Academic Search

The magnetic fields of interplanetary objects that were ejected as coronal mass ejections (CMEs) from the limb of the Sun were observed by the NOZOMI spacecraft at 1.38 AU above the east limb of the Sun. The solar wind magnetic field whose launch time coincided with ejection of the limb CME was different from that estimated from ACE observations near

T. Nakagawa; A. Matsuoka

2003-01-01

61

Modeling the magnetosphere for northward interplanetary magnetic field: Effects of electrical resistivity  

Microsoft Academic Search

We develop a simple analytic model and use global simulations of Earth's magnetosphere to investigate the effects of electrical resistivity on the topology of the magnetosphere for northward interplanetary magnetic field (IMF). We find that for low resistivity values (<~104Omegam) the magnetosphere remains open after 6 hours of northward IMF. For larger values (>~2×105Omegam) the magnetic flux of the tail

Joachim Raeder

1999-01-01

62

OBSERVATIONS OF A SMALL INTERPLANETARY MAGNETIC FLUX ROPE ASSOCIATED WITH A MAGNETIC RECONNECTION EXHAUST  

SciTech Connect

A small interplanetary magnetic flux rope prior to an X-line magnetic reconnection exhaust was observed on 1998 March 25 at 1 AU. The X-line magnetic reconnection exhaust has been identified and reported by Gosling et al. The duration of this small magnetic flux rope is about 2 hr. We fitted the constant alpha force-free model to the observed magnetic fields. The model fitting results show that the spacecraft crosses the magnetic flux rope well away from the axis, with d {sub 0}/R {sub 0} being 0.76. The fitting results also show that its magnetic configuration is a right-handed helical flux rope, that the estimated field intensity at the axis is 16.3 nT, and that its diameter is 0.0190 AU. In addition, the axial direction of this rope is (theta = 6 deg., phi = 214 deg.), namely, this magnetic flux rope is lying nearly in the ecliptic plane. According to the geometric relation of the small flux rope and the reconnection exhaust, it is very possible that the small magnetic flux rope has a larger scale initially and comes from the corona; its magnetic fields are peeled off when moving from the Sun to the Earth and at last it reaches a small scale. Though magnetic reconnection can produce a flux-rope topology, in this case the X-line magnetic reconnection is destroying rather than generating the small magnetic flux rope.

Feng, H. Q. [College of Physics and Electronics Science, Luoyang Normal University, Luoyang (China); Wu, D. J., E-mail: hengqiangfeng@gmail.co [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2009-11-10

63

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

SciTech Connect

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

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

1991-07-01

64

Reconstruction of the sector structure of the interplanetary magnetic field by geomagnetic station data  

NASA Astrophysics Data System (ADS)

This paper describes a new method for reconstructing the polarity of the interplanetary magnetic field. The technique is based on the Svalgaard-Mansurov effect. We ause geomagnetic data of high-latitude stations with a long observation period, including the presatellite era. This method is designed to improve the quality and accuracy of reconstructed polarity, complementing the results of previous methods of Svalgaard (1975) and Vennerström et al. (2001). For the large presatellite period from 1926, the accuracy of the method is estimated to be around 89% of overlaps with the interplanetary magnetic field polarity determined from satellite data.

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

2012-11-01

65

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

PubMed

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

Mazur; Mason; Dwyer; Giacalone; Jokipii; Stone

2000-03-20

66

A preliminary analysis of dynamic and realistic heliosphere using interplanetary scintillation and photospheric magnetic data  

NASA Astrophysics Data System (ADS)

A new MHD simulation method for reproducing a realistic and time-varying global heliospheric modelling is developed using solar-wind speed data from interplanetary sintillation (IPS) and photospheric magnetic data from optical observations. The IPS together with the magnetic data provide us inner boundary conditions which include both co-rotating solar-wind speed distribution and magnetic field distributions using a tilted current sheet model. Hence it enables us to reproduce dynamical co-rotating wind-wind interaction and also magnetic field structures such as an oscillating equatorial magnetic neutral sheet in a three-dimensional heliosphere. In our preliminary results of this method, a realistic and oscillating equatorial neutral sheet and wind-wind interactions are shown both in the interplanetary space and the heliosheath.

Washimi, Haruichi; Hayashi, Keiji; Tokumaru, Munetoshi; Zank, Gary P.; Hu, Qiang; Tanaka, Takashi; Florinski, Vladimir; Adams, James; Kubo, Yuki

2012-05-01

67

Long Time Behaviour of the Interplanetary Magnetic Field-Sectorial Structure.  

National Technical Information Service (NTIS)

The behavior of the interplanetary magnetic field (IMF) polarity was analyzed from data covering the years 1926 to 1982. The data refer to daily values of the IMF polarity, which is defined as being away or toward, according to the predominat direction of...

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

1984-01-01

68

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

69

Polar cap electric field saturation during interplanetary magnetic field Bz north and south conditions  

Microsoft Academic Search

We report the results of an investigation of the saturation of the polar cap electric field during periods of large northward and southward interplanetary magnetic field (IMF). While it has been demonstrated that saturation can occur for both northward and southward IMF, a direct comparison between the two regimes during saturated driving has not been performed. We use solar wind

F. D. Wilder; C. R. Clauer; J. B. H. Baker

2010-01-01

70

Interplanetary magnetic field–geomagnetic field coupling and vertical variance index  

Microsoft Academic Search

The solar wind impacting at the geomagnetopause contains transient variations in the embedded interplanetary magnetic field (IMF). These disturbances are mirrored in the horizontal geomagnetic field measured at the Huancayo and Ascension Island stations. This investigation attempts to relate the microtemporal fluctuations in the IMF with the horizontal component of the geomagnetic field by means of a newly developed daily

A. Abraham; G. Renuka; L. Cherian

2010-01-01

71

Reconstruction of Interplanetary Magnetic Field and Solar Wind Speed for the Last 135 Years Revisited  

Microsoft Academic Search

We reconstruct the magnitude of the interplanetary magnetic field B and solar wind speed v at 1 AU using 1) yearly values of sunspot numbers and geomagnetic index aa; 2) available spacecraft measurements of v and B since 1964. We compare our results with the reconstruction done by Stamper et al. (1999) and also with the reconstruction by Svalgaard et

V. A. Osherovich; J. Fainberg

2007-01-01

72

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

73

Evidence for the tongue of ionization under northward interplanetary magnetic field conditions  

Microsoft Academic Search

The activities of the International Ionospheric Tomography Community open up new possibilities of simultaneously imaging the large-scale spatial structure of the ionosphere in different longitude sectors. In the study, tomography receiver chains in Scandinavia and Greenland were used to provide a wide view of the plasma density structure in the winter, magnetic postnoon sector under conditions of stable, positive interplanetary

H. R. Middleton; S. E. Pryse; L. Kersley; G. S. Bust; E. J. Fremouw; J. A. Secan; W. F. Denig

2005-01-01

74

Predicting interplanetary magnetic field (IMF) propagation delay times using the minimum variance technique  

Microsoft Academic Search

It has been known that the fluctuations in the interplanetary magnetic field (IMF) may be oriented in approximately planar structures that are tilted with respect to the solar wind propagation direction along the Sun-Earth line. This tilting causes the IMF propagating from a point of measurement to arrive at other locations with a timing that may be significantly different from

D. R. Weimer; D. M. Ober; N. C. Maynard; M. R. Collier; D. J. McComas; N. F. Ness; C. W. Smith; J. Watermann

2003-01-01

75

Variable time delays in the propagation of the interplanetary magnetic field  

Microsoft Academic Search

(1) Simultaneous measurements of the interplanetary magnetic field (IMF) are obtained at various locations with four spacecraft, ACE, Wind, IMP-8, and Geotail. We have devised a technique whereby the exact propagation delay time between ACE, at the L1 orbit, and each of the other three spacecraft can be derived from these measurements. This propagation delay is determined as a continuously

D. R. Weimer; D. M. Ober; N. C. Maynard; W. J. Burke; M. R. Collier; D. J. McComas; N. F. Ness; C. W. Smith

2002-01-01

76

Variable time delays in the propagation of the interplanetary magnetic field  

Microsoft Academic Search

Simultaneous measurements of the interplanetary magnetic field (IMF) are obtained at various locations with four spacecraft, ACE, Wind, IMP-8, and Geotail. We have devised a technique whereby the exact propagation delay time between ACE, at the L1 orbit, and each of the other three spacecraft can be derived from these measurements. This propagation delay is determined as a continuously varying

D. R. Weimer; D. M. Ober; N. C. Maynard; W. J. Burke; M. R. Collier; D. J. McComas; N. F. Ness; C. W. Smith

2002-01-01

77

Low-latitude geomagnetic response to the interplanetary conditions during very intense magnetic storms  

NASA Astrophysics Data System (ADS)

The variations in the horizontal and declination components of the geomagnetic field in response to the interplanetary shocks driven by fast halo coronal mass ejections, fast solar wind streams from the coronal hole regions and the dynamic pressure pulses associated with these events are studied. Close association between the field-aligned current density ( j?) and the fluctuations in the declination component (? DABG) at Alibag is found for intense storm conditions. Increase in the dawn-dusk interplanetary electric field ( Ey) and ? DABG are generally in phase. However, when the magnetospheric electric field is directed from dusk to dawn direction, a prominent scatter occurs between the two. It is suggested that low-latitude ground magnetic data may serve as a proxy for the interplanetary conditions in the solar wind.

Rawat, R.; Alex, S.; Lakhina, G. S.

2009-05-01

78

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

79

Magnetic Flux Circulation During Dawn-Dusk Oriented Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

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. H.; Deng, Y.; Wiltberger, M. J.; Lyon, J.

2010-12-01

80

Latitudinal Dependence of Cosmic Rays Modulation at 1 AU and Interplanetary Magnetic Field Polar Correction  

NASA Astrophysics Data System (ADS)

The cosmic rays differential intensity inside the heliosphere, for energy below 30 GeV/nuc, depends on solar activity and interplanetary magnetic field polarity. This variation, termed solar modulation, is described using a 2-D (radius and colatitude) Monte Carlo approach for solving the Parker transport equation that includes diffusion, convection, magnetic drift and adiabatic energy loss. Since the whole transport is strongly related to the interplanetary magnetic field (IMF) structure, a better understanding of his description is needed in order to reproduce the cosmic rays intensity at the Earth, as well as outside the ecliptic plane. In this work an interplanetary magnetic field model including the standard description on ecliptic region and a polar correction is presented. This treatment of the IMF, implemented in the HelMod Monte Carlo code (version 2.0), was used to determine the effects on the differential intensity of Proton at 1\\,AU and allowed one to investigate how latitudinal gradients of proton intensities, observed in the inner heliosphere with the Ulysses spacecraft during 1995, can be affected by the modification of the IMF in the polar regions.

Bobik, P.; Boella, G.; Boschini, M. J.; Consolandi, C.; Della Torre, S.; Gervasi, M.; Grandi, D.; Kudela, K.; Pensotti, S.; Rancoita, P. G.; Rozza, D.; Tacconi, M.

81

Influence of solar magnetic fields on the escape of accelerated particles into interplanetary space  

SciTech Connect

The fact that large particle fluxes are observed in only 40% of the cases even from powerful chromospheric flares (importance > or =2B) attracts attention. A statistical relation is found between the sign of the longitudinal component of the photospheric field and the size of the flux of energetic particles in the interplanetary medium. If an H..cap alpha.. flare was observed in a region of a positive sign of the magnetic field, then large particle fluxes (a rise of 10--1000 times) will be recorded in the interplanetary medium with a probability of approx.80%. But if an H..cap alpha.. flare was observed in a region of a negative magnetic field, then there will be almost no particles (a rise of no more than two times) with a probability of 86%.

Kuzhevskii, B.M.; Petrova, I.V.

1978-09-01

82

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

83

Interplanetary magnetic field connection to the L1 Lagrangian orbit during upstream energetic ion events  

Microsoft Academic Search

Energetic ions (>15 keV) moving upstream from the Earth's bow shock frequently appear at the sunward Lagrangian point (L1) ~1.5×106km upstream from Earth. The most common orientation of the interplanetary magnetic field (IMF) at L1 during these upstream events is near-radial from the Sun (the nominal direction for connection to the magnetosphere). However, strong unidirectional beams of ions streaming away

D. K. Haggerty; E. C. Roelof; C. W. Smith; N. F. Ness; R. L. Tokar; R. M. Skoug

2000-01-01

84

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

Microsoft Academic Search

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

Thomas H. Zurbuchen; Ian G. Richardson

2006-01-01

85

Interplanetary magnetic field control and magnetic conjugacy of auroral E region backscatter  

NASA Astrophysics Data System (ADS)

The interplanetary magnetic field (IMF) control and magnetic conjugacy of the auroral E region backscatter are assessed using observations by the nominally conjugate Super Dual Auroral Radar Network (SuperDARN) Syowa East and Pykkvibaer HF radars at ˜69° magnetic latitude and the ACE satellite measurements in the solar wind. A common-mode radar data set comprising 118 days in January-December 2000 is considered, and the E region echo occurrence rates are calculated for each 10 min interval. The occurrence variations are adjusted for the magnetic local time and seasonal dependencies by subtracting the reference daily trends for low IMF magnitudes. The Bz effects dominate at Bz < 0, while By effects become noticeable at Bz > 0. The occurrence strongly increases as Bz becomes more negative and minimizes at small negative By and positive Bz values. The Bz effects are stronger by a factor of ˜2 than those of By. The extent of magnetic conjugacy is considerable, with an overall correlation between conjugate occurrences of 0.7. The backscatter is most conjugate at large negative Bz and generally at large IMF values. The correlations are higher on the dayside and during the equinoxes, indicating a preference for both conjugate locations to be sunlit. Finally, correlations of occurrences with solar wind coupling functions are higher on the dayside, with some evidence of the response time increasing away from magnetic noon, implying more direct IMF control near noon. The overall predictability of the E region backscatter occurrence from the solar wind inputs is considerable, with correlations being higher than those reported previously for the F region backscatter.

Makarevich, Roman A.; Koustov, A. V.; Carter, B. A.

2012-01-01

86

Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions  

NASA Astrophysics Data System (ADS)

Historic geomagnetic activity observations have been used to reveal centennial variations in the open solar flux and the near-Earth heliospheric conditions (the interplanetary magnetic field and the solar wind speed). The various methods are in very good agreement for the past 135 years when there were sufficient reliable magnetic observatories in operation to eliminate problems due to site-specific errors and calibration drifts. This review underlines the physical principles that allow these reconstructions to be made, as well as the details of the various algorithms employed and the results obtained. Discussion is included of: the importance of the averaging timescale; the key differences between ``range'' and ``interdiurnal variability'' geomagnetic data; the need to distinguish source field sector structure from heliospherically-imposed field structure; the importance of ensuring that regressions used are statistically robust; and uncertainty analysis. The reconstru! ctions are exceedingly useful as they provide calibration between the in-situ spacecraft measurements from the past five decades and the millennial records of heliospheric behaviour deduced from measured abundances of cosmogenic radionuclides found in terrestrial reservoirs. Continuity of open solar flux, using sunspot number to quantify the emergence rate, is the basis of a number of models that have been very successful in reproducing the variation derived from geomagnetic activity. These models allow us to extend the reconstructions back to before the development of the magnetometer and to cover the Maunder minimum. Allied to the radionuclide data, the models are revealing much about how the Sun and heliosphere behaved outside of grand solar maxima and are providing a means of predicting how solar activity is likely to evolve now that the recent grand maximum (that had prevailed throughout the space age) has come to an end.

Lockwood, Mike

2013-09-01

87

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

88

Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness: 2. Oblique collision  

Microsoft Academic Search

The numerical studies of the interplanetary coupling between multiple magnetic clouds (MCs) are continued by a 2.5-dimensional ideal magnetohydrodynamic (MHD) model in the heliospheric meridional plane. The interplanetary direct collision (DC)\\/oblique collision (OC) between both MCs results from their same\\/different initial propagation orientations. Here the OC is explored in contrast to the results of the DC. Both the slow MC1

Ming Xiong; Huinan Zheng; Shui Wang

2009-01-01

89

Interplanetary medium A dusty plasma  

NASA Astrophysics Data System (ADS)

The average mass of dust per volume in space equals that of the solar wind so that the interplanetary medium should provide an obvious region to study dust plasma interactions. While dust collective behavior is typically not observed in the interplanetary medium, the dust component rather consists of isolated grains screened by and interacting with the plasma. Space measurements have revealed several phenomena possibly resulting from dust plasma interactions, but most of the dust plasma interactions are at present not quantified. Examples are the production of neutrals and pick-up ions from the dust, dust impact generated field variations at spacecraft and magnetic field variations possibly caused by solar wind interacting with dust trails. Since dust particles carry a surface charge, they are exposed to the Lorentz force in the interplanetary magnetic field and for grains of sub-micrometer sizes acceleration can be substantial.

Mann, Ingrid

90

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

91

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

92

DRIFT ORBITS OF ENERGETIC PARTICLES IN AN INTERPLANETARY MAGNETIC FLUX ROPE  

SciTech Connect

Interplanetary magnetic flux ropes have significant effects on the distribution of energetic particles in space. Flux ropes can confine solar energetic particles (SEPs) for hours, and have relatively low densities of Galactic cosmic rays (GCRs), as seen during second-stage Forbush decreases. As particle diffusion is apparently inhibited across the flux rope boundary, we suggest that guiding center drifts could play a significant role in particle motion into and out of the flux ropes. We develop an analytic model of the magnetic field in an interplanetary magnetic flux rope attached to the Sun at both ends, in quasi-toroidal coordinates, with the realistic features of a flux rope cross section that is small near the Sun, expanding with distance from the Sun, and field lines that are wound less tightly close to the Sun due to stretching by the solar wind. We calculate the particle drift velocity field due to the magnetic field curvature and gradient as a function of position and pitch-angle cosine, and trace particle guiding center orbits numerically, assuming conservation of the first adiabatic invariant. We find that SEPs in the interior of a flux rope can have drift orbits that are trapped for long times, as in a tokamak configuration, with resonant escape features as a function of the winding number. For Forbush decreases of GCRs, the drifts should contribute to a unidirectional anisotropy and net flow from one leg of the loop to the other, in a direction determined by the poloidal field direction.

Krittinatham, W.; Ruffolo, D., E-mail: watcharawuth.krittinatham@gmail.co, E-mail: scdjr@mahidol.ac.t [Department of Physics, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400 (Thailand)

2009-10-10

93

New Insights into The Structure of the Turbulent Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

We present new insights into the structure of the turbulent interplanetary magnetic field. Various authors [1,2] have studied field line random walk associated with interplanetary fields consisting of smooth mean fields and fluctuations. One possible way to generate fluctuations [3,4] is at a source surface near the solar surface, by random transverse plasma motions (such as supergranulation at the solar photosphere or perhaps reconnection), together with a uniform radial outflow at a specified solar wind speed. In this approach, the structure of the magnetic field fluctuations is controlled by the temporal and spatial dependence of the footpoint velocity field. These combine to regulate the spatial structure observed in the interplanetary field. Further dynamical processing is ignored in this view, which is therefore most appropriate for large scale fluctuations. Comparison of this picture with observations from the magnetometer on the Ulysses spacecraft has shown good agreement. A quite different approach to modeling the spatial structure of interplanetary fluctuations is embodied in the so-called two component model, This was introduced [5,6,7] as a useful simplified parameterization of interplanetary fluctuations, and, since it is associated with no specific generation mechanism, this approach is consistent with either solar-surface or in situ generation of turbulence. This also shows good agreement with observations. Here, we show that these two apparently different ways of modeling turbulent fields can be closely related. In particular, we show that by properly choosing the temporal and spatial dependence of the transverse velocity field at the solar source surface, we can generate the two component model (as well as many other possible models). The consequences of this insight for our understanding of turbulence and energetic-particle transport are discussed. [1] Jokipii and Parker, Phys. Rev. Lett, 21, 44, 1968 [2] Matthaeus et al, Phys. Rev Lett. 75, 2136, 1995 [3] Jokipii and Kota Geophys. Res. Lett., 16, 1, 1989 [4] Giacalone and Jokipii, Astrophys. J. 616, 573, 2004 [5] Matthaeus, Goldstein and Roberts, JGR, 95, 20673, 1990 [6] Tu and Marsch, 98, 1257, 1993 [7] Bieber etal, Atrophys. J., 420, 294, 1994

Matthaeus, W. H.; Giacalone, J.; Jokipii, J. R.

2005-12-01

94

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

95

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

96

An Analysis of Magnetohydrodynamic Invariants of Magnetic Fluctuations within Interplanetary Flux Ropes  

NASA Astrophysics Data System (ADS)

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 (|? m | in [0.6: 1]), but extremely variable cross-helicity states (|? 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 \\sqrt{\\sigma _{m}^{2}+\\sigma _{c}^{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.; Perri, S.; Bruno, R.; Carbone, V.; Amicis, R. D.

2013-10-01

97

Anomalous magnetosheath properties during Earth passage of an interplanetary magnetic cloud  

SciTech Connect

In this work the authors present a model for the behavior of the magnetosheath during the passage of the earth thru an interplanetary magnetic cloud. They study the variation of plasma flow and field values as a result of this encounter. The unique feature of such encounters is that they present substantial changes in the solar wind conditions along the bow shock and magnetopause for periods of 1 to 2 days. The mach number upstream of the bow shock can be as low as 3, compared to normal value of 8 to 10. The mach number and magnetic shear across the magnetopause have a major impact on the magnetosheath properties. The authors use the encounter of January 14-15, 1988, as a basis for their model, and apply ideal MHD equations, by means of a boundary layer technique, to study changes in field and plasma flow patterns.

Farrugia, C.J. [Univ. of Malta, Msida (Malta); Erkaev, N.V. [Russian Academy of Sciences, Krasnoyarsk (Russian Federation); Burlaga, L.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)] [and others

1995-10-01

98

Quantitative Imaging of the Solar Wind: CME Mass Evolution and the Interplanetary Magnetic Flux Balance  

NASA Astrophysics Data System (ADS)

We recently developed post-processing techniques for heliospheric images from the STEREO spacecraft; the new data sets enable, for the first time, quantitative photometric studies of evolving wind features at distances up to 1 A.U. from the Sun. We have used the new data to trace several CMEs and magnetic disconnection events to their origins in the solar corona, and to infer the force balance and entrained magnetic flux in those features. We present recent results showing the relationship between ICME and CME anatomy, in particular the origin of an observed interplanetary flux rope and the relationship between original launched solar material and piled-up sheath material and flux in the storm at 1. A.U. We discuss implications for understanding space weather physics and predicting individual events, and point out the importance of future imaging technologies such as polarized heliospheric imaging.

DeForest, Craig

2012-05-01

99

Explanation for anomalous equatorial ionospheric electric fields associated with a northward turning of the interplanetary magnetic field  

Microsoft Academic Search

Anomalous reversals of the zonal equatorial electric field component have sometimes been observed when the interplanetary magnetic field turns northward from a steady southerly direction. We suggest that this reversal is associated with a sudden change in the convection electric field in the magnetosphere and present measurements to support this explanation. Although slower variations in the convection field are shielded

M. C. Kelley; B.G. Fejer; C.A. Gonzales

1979-01-01

100

A Comprehensive Study of Relationship Between Subsolar Standoff Distance of the Magnetopause and Cone Angle of Interplanetary Magnetic Field  

Microsoft Academic Search

The subsolar standoff distance of the Earth's magnetopause is an important parameter in studying interactions between the solar wind and the magnetosphere. Its value is mainly controlled by the north-south component (Bz) of the interplanetary magnetic field (IMF) and solar wind dynamic pressure (Dp). Recent studies have found that the subsolar standoff distance is large for small cone angle of

C. Huang; J. Shue; W. Hsieh; B. Lee

2010-01-01

101

On the Role of Fluctuations in the Interplanetary Magnetic Field of Heat Conduction in the Solar Wind.  

National Technical Information Service (NTIS)

In the study of the role of fluctuations in the interplanetary magnetic field on heat conduction in the solar wind, the authors find that the main reduction of the thermal conductivity should occur at low heliocentric distances. The main reason is that th...

S. Cuperman N. Metzler

1973-01-01

102

Sector structure of the interplanetary magnetic field in the nineteenth century  

NASA Astrophysics Data System (ADS)

The interplanetary magnetic field (IMF) is the magnetic field of the Sun stretched out by the solar wind. The polarity of the IMF is either positive or negative according to the polarity of the original solar magnetic field. The equivalent ionospheric Disturbance Polar current powered by the azimuthal Y component current system is located at polar latitudes and provides specific geomagnetic variations. It is known that the configuration of this system depends on the polarity of the IMF. Thus, in the absence of direct data in the presatellite era, the IMF sector structure could only be inferred from ground-based geomagnetic observations (Svalgaard,1968; Mansurov,1969). In this paper the IMF polarities have been reconstructed for the nineteenth century for the first time. It is possible due to the advent of the digitized geomagnetic records in the Helsinki and St. Petersburg observatories. These data have been available since 1844 and 1878, respectively. We assume that the reconstructions are reliable enough to study the solar magnetic field of the past. The polarities inferred for the nineteenth and twentieth centuries display similar sector structures. Seasonal variations of the ratio of positive and negative sectors give clear evidence of solar magnetic field reversals starting from the second half of the nineteenth century.

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

2013-07-01

103

Variations of the atmospheric electric field in the near-pole region related to the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Variations in the atmospheric, near-surface vertical electric field component Ez measured at the Russian Antarctic station Vostok in 1998 are analyzed in conjunction with changes of the interplanetary magnetic field (IMF). A total of 134 days were selected which satisfied the ``fair weather'' conditions, that is, days with absence of high winds, falling or drifting snow, clouds, and electric field ``pollution'' from the station's power plant. It is shown that the average diurnal variation of Ez for these days follows the global geoelectric field ``fair-weather'' diurnal variation: the ``Carnegie'' curve, which describes the global electric circuit formed by the thunderstorm activity occurring mostly over equatorial regions. The Ez diurnal variation shows strong seasonal dependence: it is maximal (~40% of the average daily magnitude) in summer but gradually reduces through the equinoctial months and is almost negligible during the austral winter. Ez at Vostok is strongly affected by variations in both the IMF By and Bz components. The influence of By is dominant during geomagnetic daytime hours (1100-1400 UT at Vostok): Ez increases with By in the range from -10 to +10 nT. The IMF Bz effect is mainly seen at dawn (Ez decreases with Bz) and dusk (Ez increases with Bz).

Frank-Kamenetsky, A. V.; Troshichev, O. A.; Burns, G. B.; Papitashvili, V. O.

2001-01-01

104

Relations between the interplanetary magnetic field Bz, AE index, and cusp latitude  

NASA Astrophysics Data System (ADS)

The connection between the interplanetary magnetic field (IMF) Bz, AE index, and magnetospheric cusp location is examined qualitatively. Seven months during 1979-1980 were searched for periods of low auroral activity and/or periods when the IMF Bz component and the AE index varied inconsistently (i.e., southward Bz and quiescent AE). During quiet auroral conditions, the IMF Bz, AE index, and equatorward cusp boundary generally tend to act coherently, although during very quiet times the cusp may exhibit considerable variability that is apparently unassociated with either Bz or AE. The effects of Bz and AE variations on the cusp are quite complicated and the observations simply do not indicate clear cusp response to one or the other. The largest equatorward cusp motions seem to occur as a result of prolonged southward Bz lasting 3 hours or more, and cusp latitude appears to depend strongly on time-accumulated Bz.

Carbary, J. F.; Meng, C.-I.

1986-02-01

105

Auroral electrodynamics at the cusp/cleft poleward boundary during northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Combined ground- and satellite-based information on the electrodynamics of the cusp/cleft ionosphere is used for a case characterized by northward interplanetary magnetic field (IMF). Focus is placed on the auroral dynamics/morphology within the zone of strong azimuthal convection at the cusp poleward boundary. Attention is given to a generator mechanism poleward of the cusp/cleft, giving rise to strong momentum transfer and discrete electron precipitation within a 200-km-wide latitudinal zone at the cusp/cleft poleward boundary. The characteristics of the cusp/cleft ionosphere combined with similar studies of negative IMF B(z) cases indicate that a qualitatively similar mode of solar wind-magnetosphere interaction occurs for both northward and southward IMF.

Sandholt, Per E.

1991-05-01

106

High-latitude ionospheric convection pattern during steady northward interplanetary magnetic field  

SciTech Connect

The DMSP F8 satellite`s coverage of Earth`s polar regions provides horizontal ion drift velocities along the dawn-dusk meridian at approximately 835 km altitude in each hemisphere during the 100 min orbital period. The authors examine the ionospheric convection signatures observed by this spacecraft in the summer and winter hemispheres during periods when the interplanetary magnetic field (IMF) is directed northward for at least 45 min prior to the satellite entering the polar region and remains northward throughout the polar pass. These convection signatures can be readily categorized by the number of sunward and antisunward flow regions and by their potential distributions. Here the authors describe the most frequently identifiable and reproducible features of the convection pattern that exist during steady northward IMF conditions. In addition to IMF Bz, the influences on the convection pattern of the IMF Bz.

Cumnock, J.A.; Heelis, R.A.; Hairston, M.R.; Newell, P.T.

1995-08-01

107

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

108

Short-duration convection bays and localized interplanetary magnetic field structures on November 28, 1995  

NASA Astrophysics Data System (ADS)

We present ground-based, plasma sheet, and magnetosheath observations of two subsequent short-duration (10-20 min) increases of the postmidnight westward electrojet on November 28, 1995. Appearing as though small (150-200 nT) substorms, they were not accompanied by any substorm expansion onset signatures. Auroral breakup, worldwide Pi2 pulsations, and the corresponding plasma sheet activity, such as fast flows, current disruption, and plasmoid generation, were all observed only at the recovery of the second electrojet increase. These convection bays were associated with the equatorward expansion of the auroras and simultaneous magnetic variations in the polar cap and middle latitudes. Growth phase signatures of the lobe field increase and tailward stretching of magnetic field were also observed in the plasma sheet. Bursty bulk flows in the plasma sheet seem to be quenched at the onset of first convection bay and did not resume until the auroral breakup which concluded the second convection bay. A point of interest of this event was the ``incomplete'' convection/current system with a well-developed dawn vortex in the absence of well-defined dusk vortex; instead, a complicated transient activity dominated over the afternoon-dusk local time sector. We interpret this asymmetry either in terms of the magnetopause encounter with the edge of the solar wind driver, i.e., strong southward IMF, which hits only the dawn part of the magnetosphere, or with an extremely slant interplanetary discontinuity. This unique configuration was inferred from observations of uncorrelated strong southward Bz events by the Wind and IMP 8 spacecraft in the dusk and dawn magnetosheath, respectively, as well as from the directional analysis of the interplanetary discontinuities which form the edges of these structures. We suggest that interaction of the magnetosphere with very slant solar wind discontinuities may bring various specific features to magnetospheric and ionospheric dynamics that have not been reported.

Sergeev, V. A.; Kamide, Y.; Kokubun, S.; Nakamura, R.; Deehr, C. S.; Hughes, T. J.; Lepping, R. P.; Mukai, T.; Petrukovich, A. A.; Shue, J.-H.; Shiokawa, K.; Troshichev, O. A.; Yumoto, K.

1998-10-01

109

Investigating Magnetic Field Line Lengths in Interplanetary Coronal Mass Ejections Using Energetic Electron Events  

NASA Astrophysics Data System (ADS)

About one quarter of the observed interplanetary coronal mass ejections (ICMEs) are characterized by enhanced magnetic fields that smoothly rotate in direction over time scales of about 10 to 50 hours. These ICMEs have the appearance of magnetic flux ropes and are known as “magnetic clouds” (MCs). In a flux rope, the twist of the magnetic field increases with distance from the flux-rope axis. The total lengths of the twisted field lines can be determined using solar energetic particles of known speeds when the solar release time and the 1 AU onset times of the particles are known. A recent examination of about 30 electron events in and near eight ICMEs showed no obvious indication that the field line lengths were longest near the MC boundaries and shortest at the MC axis or outside the MC, contrary to the expectations for a flux-rope. In this study, we use the impulsive beamed electron events observed with the EPAM instrument on the ACE spacecraft to determine the field line lengths inside a sample of ICMEs included in the catalog of Richardson and Cane (2010). In particular, we apply this technique for the first time to ICMEs that are not MCs and compare the field line lengths inside MCs and non-MC ICMEs and in the ambient solar wind outside the ICMEs.

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

2010-12-01

110

O+ outflow channels around Venus controlled by directions of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Using the plasma and the magnetic field data measured by the ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and the magnetometer (MAG) onboard Venus Express between June 2006 and December 2008, positions of high energy O+ fluxes (>100 eV) around Venus are examined for two different interplanetary magnetic field (IMF) configurations: IMF nearly perpendicular to the Venus-Sun line (perpendicular IMF case) and IMF nearly parallel to it (parallel IMF case). In most of the perpendicular IMF case, the high energy O+ fluxes are observed only near the magnetic poles. In contrast, they are observed regardless of a convection electric field around the terminator in most of the parallel IMF case. Energy of the flux depends on the convection electric field direction in the former case. In contrast, it has no dependence on the field direction in the latter case. We attribute these results to more complicated draping pattern of IMF around the ionosphere in the parallel IMF case than for that of the perpendicular IMF case. In the perpendicular IMF case, the IMF drapes around the ionosphere, forming a single plasma sheet. In contrast, in the parallel IMF case, the IMF drapes complicatedly, creating many antiparallel configuration of local magnetic field. Such multiple antiparallel configuration results in a local acceleration of O+ and more outflow channels. Thus, the ion acceleration region and its mechanism can be essentially different between the perpendicular IMF case and the parallel IMF case.

Masunaga, K.; Futaana, Y.; Yamauchi, M.; Barabash, S.; Zhang, T.; Fedorov, A.; Terada, N.; Okano, S.

2011-12-01

111

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

NASA Astrophysics Data System (ADS)

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 ˜ 80% of cases, the GCR intensity decreased during the passage of these structures, i.e., a "Forbush decrease" occurred, while in ˜ 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 ˜ 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. J. 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.

2011-06-01

112

ON THE INTERNAL STRUCTURE OF THE MAGNETIC FIELD IN MAGNETIC CLOUDS AND INTERPLANETARY CORONAL MASS EJECTIONS: WRITHE VERSUS TWIST  

SciTech Connect

In this study, we test the flux rope paradigm by performing a 'blind' reconstruction of the magnetic field structure of a simulated interplanetary coronal mass ejection (ICME). The ICME is the result of a magnetohydrodynamic numerical simulation and does not exhibit much magnetic twist, but appears to have some characteristics of a magnetic cloud, due to a writhe in the magnetic field lines. We use the Grad-Shafranov technique with simulated spacecraft measurements at two different distances and compare the reconstructed magnetic field with that of the ICME in the simulation. While the reconstructed magnetic field is similar to the simulated one as seen in two dimensions, it yields a helically twisted magnetic field in three dimensions. To further verify the results, we perform the reconstruction at three different position angles at every distance point, and all results are found to be in agreement. This work demonstrates that the current paradigm of associating magnetic clouds with flux ropes may have to be revised.

Al-Haddad, N.; Roussev, I. I.; Lugaz, N. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Moestl, C. [Space Research Institute, Austrian Academy of Sciences, Graz 8042 (Austria); Jacobs, C.; Poedts, S. [Centrum voor Plasma-Astrofysica, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Farrugia, C. J., E-mail: iroussev@ifa.hawaii.edu, E-mail: nlugaz@ifa.hawaii.edu, E-mail: christian.moestl@oeaw.ac.at [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)

2011-09-10

113

Substorm-like magnetospheric response to a discontinuity in the Bx component of interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We examined the magnetospheric magnetic field and plasma responses to an encounter of a discontinuity in the Bx component of interplanetary magnetic field (IMF). The striking variations of simultaneous solar wind dynamic pressure and IMF-Bz were not observed. Furthermore, we found that this IMF-Bx discontinuity was a heliospheric current sheet, separating two high-speed solar wind streams with different velocity and magnetic polarity. In this study, the magnetic field and plasma data were obtained from Time History of Events and Macroscale Interactions during Substorms (THEMIS), Cluster, and GOES to investigate the magnetospheric responses, and those were taken from ACE and Geotail to monitor the solar wind conditions. Simultaneous geomagnetic field variations from the ground observatories and aurora activity from Polar were also examined. When the discontinuity encountered the magnetosphere, THEMIS-D, -E, and THEMIS-A observed abrupt and transient magnetic field and plasma variations in the dawnside near-Earth magnetotail and tail-flank magnetopause. Significant magnetic field perturbations were not observed by Cluster as located in the duskside magnetotail at this time interval. Although simultaneous dipolarization and negative bay variations with Pi2 waves were observed by GOES and the ground observatories, global auroral activities were not found. Around the dawnside tail-flank magnetopause, THEMIS-C and -A experienced the magnetopause crossings due to the magnetopause surface waves induced by Kelvin-Helmholtz instability. These results suggest that the magnetic field and plasma variations in the near-Earth magnetotail and tail-flank magnetopause were caused by moderate substorm-like phenomena and magnetopause surface waves. They also indicate that clear magnetospheric disturbances can be brought even without significant variations in the solar wind.

Nowada, M.; Lin, C.-H.; Pu, Z.-Y.; Fu, S.-Y.; Angelopoulos, V.; Carlson, C. W.; Auster, H.-U.

2012-04-01

114

Auroral electrodynamics at the cusp/cleft poleward boundary during northward interplanetary magnetic field  

SciTech Connect

Combined latitude profiles of optical aurora, magnetic disturbances, particle precipitation and field-aligned currents are used to investigate the electrodynamics of the cusp/cleft ionosphere during northward interplanetary magnetic field. An active zone of strong azimuthal plasma convection, manifested by the Svalgaard-Mansurov effect in ground magnetic deflections and auroral structure at the poleward boundary of the cusp/cleft is observed within {approximately}1,030-1,230 MLT. Contrary to the typical cusp/cleft auroral activity during negative IMF B{sub z} the discrete auroral forms in the present case move into the cusp/cleft arc, from the poleward edge. Both the optical observations and the inferred field-aligned current/plasma flow pattern indicate a generator mechanism poleward of the cusp/cleft, giving rise to strong momentum transfer and discrete electron precipitation within a {approximately}200 km wide latitudinal zone at the cusp/cleft poleward boundary, at the time of a poleward moving cusp/cleft arc. From this and other similar studies of the cusp/cleft ionosphere, the author concludes that a qualitatively similar mode of solar wind-magnetosphere interaction is operating both during northward and southward IMF.

Sandholt, P.E. (Univ. of Oslo (Norway))

1991-05-01

115

Observations of an interplanetary switch-on shock driven by a magnetic cloud  

NASA Astrophysics Data System (ADS)

A possible interplanetary switch-on shock event prior to a trailing magnetic cloud was observed on August 1, 2002 at 1 AU. We fit the data with the Rankine-Hugoniot (R-H) relations based on both oblique and switch-on shock models. It is found that both models are consistent with the observed data, and the best fit solutions of the two models are close to one another. For the oblique shock model, the best fit upstream shock normal angle, $\\theta$ BN1 (= cos-1(Bt1/B1)), is as small as 5.55°. The shock has the following characteristics: (1) plasma density, plasma temperature, and the magnetic field strength all increase across the shock, (2) protons are thermalized very efficiently across the shock, but it is not the case for electrons, (3) the fast-mode Mach number is greater than unity in the preshock region and less than unity in the postshock region, and (4) from the oblique shock model we find that the normal Alfvén Mach number is very close to unity in the postshock region, while from the switch-on shock model we obtain a solution of unity normal Alfvén Mach number. Our results clearly demonstrate the MHD character of a fast shock propagating along the ambient magnetic field.

Feng, H. Q.; Lin, C. C.; Chao, J. K.; Wu, D. J.; Lyu, L. H.; Lee, L. C.

2009-04-01

116

CORONAL JETS, MAGNETIC TOPOLOGIES, AND THE PRODUCTION OF INTERPLANETARY ELECTRON STREAMS  

SciTech Connect

We investigate the acceleration source of the impulsive solar energetic particle (SEP) events on 2007 January 24. Combining the in situ electron measurements and remote-sensing solar observations, as well as the calculated magnetic fields obtained from a potential-field source-surface model, we demonstrate that the jets associated with the hard X-ray flares and type-III radio bursts, rather than the slow and partial coronal mass ejections, are closely related to the production of interplanetary electron streams. The jets, originated from the well-connected active region (AR 10939) whose magnetic polarity structure favors the eruption, are observed to be forming in a coronal site, extending to a few solar radii, and having a good temporal correlation with the electron solar release. The open-field lines near the jet site are rooted in a negative polarity, along which energetic particles escape from the flaring AR to the near-Earth space, consistent with the in situ electron pitch angle distribution. The analysis enables us to propose a coronal magnetic topology relating the impulsive SEP events to their solar source.

Li, C.; Matthews, S. A.; Van Driel-Gesztelyi, L.; Sun, J.; Owen, C. J., E-mail: cl2@mssl.ucl.ac.uk [Mullard Space Science Laboratory, University College London, Dorking, Surrey RH5 6NT (United Kingdom)

2011-07-01

117

Topological structure of the magnetotail as a function of interplanetary magnetic field direction  

SciTech Connect

Magnetic reconnection between the interplanetary magnetic field (IMF) and the geomagnetic field is thought to play a major role in the transfer of solar wind momentum and energy to the magnetosphere. As the angle between the IMF and the geomagnetic field is changed at the bow of the magnetosphere, the topological record of the location of the reconnection region should be recorded in the magnetosheath and on the magnetopause along the flanks of the tail, because the super fast flow freezes strong magnetic gradients formed in the bow reconnection regions into the plasma downstream. In this report, the authors present results from a three-dimensional, magnetohydrodynamic (MHD), global numerical simulation code for the location of the separatrix between unconnected IMF magnetosheath field lines and reconnected field lines which penetrate the magnetopause and connect to the polar ionosphere. The angle between the IMF direction and the line where the separatrix crosses the magnetopause is shown to be a sensitive function of the IMF clock angle. The authors also explain how this behavior can be used to derive an approximate relation for the dependence of the cross-polar voltage on the IMF clock angle. They conclude with a note of caution concerning the importance of physical boundary conditions in magnetoplasma simulations. 31 refs., 5 figs.

Fedder, J.A. [Naval Research Lab., Washington, DC (United States)]|[SFA, Incorporated, Landover, MD (United States); Lyon, J.G. [Dartmouth College, Hanover, NH (United States); Slinker, S.P. [Naval Research Lab., Washington, DC (United States)] [and others

1995-03-01

118

Structure of the magnetopause for low Mach number and strongly northward interplanetary magnetic field  

SciTech Connect

The authors use ISEE magnetic field and plasma data to examine dayside magnetopause crossings under conditions of low Mach number and strongly northward interplanetary magnetic field (IMF). When the solar wind Mach number is low, the IMF strength and magnetosheath field strength are large, and they expect the effects of magnetic reconnection to be the strongest. When the IMF is strongly northward, they find that the location of the magnetopause boundary layer is very stationary in the space, and they observe many features that are common for both typical and low Mach numbers. However, under low Mach number conditions, the authors have observed some features that would be expected for cusp reconnection. The boundary layer near the subsolar region contains heated magnetosheath plasma with little hot magnetospheric component that has clearly entered the magnetosphere elsewhere. At least some of the structures present in the boundary layer are impulsive. Inside the boundary layer there is also clear evidence of accelerated flow from the cusp region for strongly northward IMF at low Mach number. Therefore at low Mach number, reconnection is important in the formation of the boundary layer for northward IMF.

Le, G.; Russell, C.T. [Univ. of California, Los Angeles, CA (United States); Gosling, J.T. [Los Alamos National Lab., NM (United States)

1994-12-01

119

Search for Persistent Quasi-Periodicities in the Solar and Interplanetary Magnetic Fields  

NASA Astrophysics Data System (ADS)

Previous analysis of the radial component of the interplanetary magnetic field from 1962 - 1998 has revealed a dominant frequency of 27.03 days to 0.02 day accuracy (Neugebauer, et al., 2000). We have repeated and extended this analysis with OMNI data from 1963 - 2007 obtained from the Coordinated Heliospheric Observations (COHO) database. Over this longer data string we find that the 27.03 day Lomb-Scargle periodogram peak is reduced while two side peaks near 26.8 days and 27.6 days become almost as strong. In the interval 1999-2007 there are two dominant periods near 26.5 days and 27.2 days. As a solar counterpart to the above analysis we have searched for persistent rotation periods near 27 days of global patterns of photospheric magnetic fields derived from Wilcox Solar Observatory synoptic Carrington rotation maps. Techniques applied include, principal components analysis, independent component analysis, singular spectrum analysis, wavelet spectral analysis, and complex demodulation. We find a variety of quasi- periodicities between 26 and 29 days that remain coherent for 1 - 2 years. In the southern solar hemisphere the strongest periodicity is at 28.2 days, while in the northern hemisphere it is around 26.5 days. Neugebauer, M., Smith, Smith, E.J., Ruzmaikin, A., Feynman, J., Vaughan, A.H. 2000, J. Geophys. Res., 106, A5, 8363.

Lawrence, J. K.; Cadavid, A. C.; Ruzmaikin, A.

2007-12-01

120

Reduction of viscous potential for northward interplanetary magnetic field as seen in the LFM simulation  

NASA Astrophysics Data System (ADS)

The two primary methods responsible for solar wind magnetosphere coupling are magnetic reconnection and the viscous interaction. The viscous interaction is generated due to the antisunward dragging of plasma inside the magnetopause by the plasma flowing in the magnetosheath, creating a return flow deeper inside the magnetosphere and producing a circulation pattern. This viscous circulation pattern is mapped into the ionosphere via magnetic field lines, which results in ionospheric electric field in the nonrotating Earth's frame. We measure this interaction in terms of an electric potential, the viscous potential. In this paper, we use the results obtained from the Lyon-Fedder-Mobarry (LFM) simulation model during periods of purely northward interplanetary magnetic field (IMF) for different solar wind velocity and ionospheric conductivity, showing a reduction of the viscous potential with increasing magnitude of northward IMF. The viscous potential is found to settle around 5-10 kV for large +Bz values. The decrease in viscous potential was found to be associated with a weak or nonexistent sunward plasma flow in the nightside plasmasheet. Instead, the return flow to the dayside occurs at high latitudes and is associated with the reconnection topology and dynamics that occur during northward IMF periods. We also show that the magnetosphere remains closed during purely northward IMF, except for two small regions—one on each hemisphere, where the magnetic reconnection occur. We argue that the reduction of the viscous potential is due to a reduction of the velocity shear across the magnetopause and the lack of sunward convection in the equatorial tail.

Bhattarai, S. K.; Lopez, R. E.

2013-06-01

121

Superconducting magnets and mission strategies for protection from ionizing radiation in interplanetary manned missions and interplanetary habitats  

Microsoft Academic Search

First order evaluations for active shielding based on superconducting magnetic lenses were made in the past in ESA supported studies. The present increasing interest of permanent space complexes, to be considered in the far future as ‘bases’ rather than ‘stations’, located in ‘deep’ space (as it has been proposed for the L1 libration’s point between Earth and Moon, or for

Piero Spillantini

2011-01-01

122

Distortion of the interplanetary magnetic field by three-dimensional propagation of coronal mass ejections in a structured solar wind  

Microsoft Academic Search

A three-dimensional (3-D) numerical magnetohydrodynamic model is used to investigate the temporal and spatial evolution of large-scale solar wind (SW) disturbances. A tilted dipole outflow configuration is specified at the inner boundary near the Sun, and a structured, corotating SW flow with a monopolar interplanetary magnetic field (IMF) is established by dynamic relaxation between 0.14 and 1.04 AU. Time-dependent variation

D. Odstrcil; V. J. Pizzo

1999-01-01

123

The interplanetary magnetic field influences mid-latitude surface atmospheric pressure  

NASA Astrophysics Data System (ADS)

The existence of a meteorological response in the polar regions to fluctuations in the interplanetary magnetic field (IMF) component By is well established. More controversially, there is evidence to suggest that this Sun-weather coupling occurs via the global atmospheric electric circuit. Consequently, it has been assumed that the effect is maximized at high latitudes and is negligible at low and mid-latitudes, because the perturbation by the IMF is concentrated in the polar regions. We demonstrate a previously unrecognized influence of the IMF By on mid-latitude surface pressure. The difference between the mean surface pressures during times of high positive and high negative IMF By possesses a statistically significant mid-latitude wave structure similar to atmospheric Rossby waves. Our results show 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. We suggest the mechanism for this from conventional meteorology. The amplitude of the effect is comparable to typical initial analysis uncertainties in ensemble numerical weather prediction. Thus, a relatively localized small-amplitude solar influence on the upper atmosphere could have an important effect, via the nonlinear evolution of atmospheric dynamics, on critical atmospheric processes.

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

2013-12-01

124

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

125

Formation of the theta aurora by a transient convection during northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Formation of the theta aurora, which appears under the conditions of northward interplanetary magnetic field (IMF) and greater IMF magnitude, is investigated from the analysis of solutions obtained from a magnetohydrodynamic (MHD) simulation. The theta aurora formation is caused by a transient convection after a sign change of IMF By. This transient convection must include a replacement of lobe field lines from old IMF originating fields to new IMF originating fields, a rotation of plasma sheet to opposite inclination, and a reformation of ionospheric convection cells. In the midst of these reconfigurations, old and new convection systems must coexist in the magnetosphere-ionosphere system. In this stage the polar cap and tail lobes are continuously encroached by the new open field lines connected to the new IMF. Whereas magnetic field lines accumulated in new lobes tend to rotate the outer plasma sheet in the opposite direction, the old merging-cell convection still continues to generate closed field lines that must return to dayside against the new lobe formation. As time goes on, the growth of new lobes results in the blocking of the return path toward the dayside of closed field lines generated in the old merging cell to form the kink structure in the plasma sheet. Losing their return path, these closed field lines generated from old lobes accumulate on the nightside. The transpolar arc (TPA) appears at the footpoints of these accumulated closed field lines. In the tail plasma sheet the cross-tail Z configuration and kink structures are generated because the plasma sheet near the magnetopause is rotated to the opposite direction while the core part is retaining old rotation.

Tanaka, T.; Obara, T.; Kunitake, M.

2004-09-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

127

MAGNETIC FIELD-LINE LENGTHS IN INTERPLANETARY CORONAL MASS EJECTIONS INFERRED FROM ENERGETIC ELECTRON EVENTS  

SciTech Connect

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

Kahler, S. W. [Air Force Research Laboratory, RVBXS, 29 Randolph Rd, Hanscom AFB, MA 01731 (United States); Haggerty, D. K. [Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Richardson, I. G., E-mail: AFRL.RVB.PA@hanscom.af.mil [Code 661, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2011-08-01

128

Global hybrid simulations: Foreshock waves and cavitons under radial interplanetary magnetic field geometry  

NASA Astrophysics Data System (ADS)

We use global hybrid (kinetic ions and fluid electrons) simulations to study the solar wind interaction with the magnetosphere for a radial ($\\theta$ vB = 0) interplanetary magnetic field (IMF) geometry. Global hybrid simulations provide a collective picture of processes taking place in the foreshock, bow shock, and magnetosheath. Because ions are treated as particles, these codes also give information on ion-scale microphysics. Under radial IMF geometry, the foreshock forms in front of the dayside magnetosphere, and the plasma convecting downstream is very perturbed. The foreshock is permeated by weakly compressive ultralow frequency (ULF) waves that propagate at angles up to 30° to the ambient field. These weakly compressive waves are generated by field-aligned ions. Wave-Particle interaction results in ion scattering, while wave amplitude grows and fluctuations become compressive as they approach the shock. While weakly compressive waves are dominant far from the shock, a second population of ULF fluctuations arises close to it. These fast magnetosonic waves propagate at large angles to the magnetic field and are linearly polarized. We find that, in addition to the ULF waves, large depressions in density and magnetic field magnitude form near the shock. These density cavitons or depressions are bounded by enhanced magnetic fields, and inside them, hot diffuse ions are present. Foreshock density cavitons in our simulations are embedded in regions with ULF activity, which is in contrast to the isolated character of ``foreshock cavities'' reported previously. We show that density cavitons form due to the nonlinear interaction of the two types of waves present in the foreshock. Wave interaction also modifies the characteristics of weakly compressive waves. A comparison of our results with Cluster observations reveals that the characteristics of weakly compressive waves in our simulation resemble the properties of right-handed 30-s waves found in the terrestrial foreshock. Likewise, we show the existence of density cavitons, or depressions, in regions of Earth's foreshock permeated by ULF waves. The properties of these observed Cluster cavitons are similar to the ones we find in the simulations.

Blanco-Cano, X.; Omidi, N.; Russell, C. T.

2009-01-01

129

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

NASA Astrophysics Data System (ADS)

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

Slavin, James

130

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

131

Solar Source of the Interplanetary Sector Structure.  

National Technical Information Service (NTIS)

The interplanetary sector structure observed by the IMP-1 satellite during three solar rotations in 1963-64 is compared with the photospheric magnetic field structure observed with the solar magnetograph at Mt. Wilson Observatory. The interplanetary secto...

J. M. Wilcox N. F. Ness

1967-01-01

132

Effect of Interplanetary Magnetic Field on the Equatorial Ionosphere Dynamics in March 1998  

NASA Astrophysics Data System (ADS)

Variations of the equatorial ionosphere height and critical frequency foF2 for Cebu Island (124 deg. E, 10.3 deg N; 2.4 in diplatitude) and Manila (121 deg. E, 14.6 deg. N, 7.3 deg. N in diplatitude) are compared with interplanetary magnetic field data. The ground-based measurements of the critical frequency foF2 Jicamarca are used for study of longitudinal variations during of 10 March 1998 magnetic storm. The subsequently main phase decrease of Dst to - 107 nT was generated by the 3 hour's negative IMF Bz=-18nT. Situation in the polar cusp was determined by 6 hour's negative IMF By = - 20 nT. The critical frequency foF2 decrease in the same way at Cebu Island and Jicamarca from 15.45 UT up to 19 UT but the values of decreases are significantly different at two stations. At Cebu Island (the night sector) the foF2 drops from 8 MHz to 2 MHz. In the day sector at Jicamarca the critical frequency drops from 11.5 MHZ to 9 MHz. These changes were accompanied by a rise of heights of the F-region. It is shown that changes in the ionospheric height at two stations (Cebu and Manila) depend from direction of the Bz IMF. The heights at two stations vary almost identical during northward IMF Bz (quiet period on March 7, 1998) and vary a fairly different way during reorientations of the IMF (disturbance periods on 9 and 12 March 1998). The distinctions between quiet and disturbance periods in heights can reach up to 50-100 km. It can be shown that this effect is the result of direct penetration of electric field from the field-aligned currents (FAC), which connected with DP systems, to equatorial ionosphere. This additional electric field of the FAC carries ions away from the equatorial F2 layer and consequently we observe maximum F2 layer at great heights. Differences between behaviour of heights at the two stations during southward IMF Bz are attributable to location of the electrojet that can be formed by the FAC electric field.

Sizova, L.; Maruyama, T.; Nozaki, K.

133

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); Clauer, C.R. [Univ. of Michigan, Ann Arbor, MI (United States)

1995-05-01

134

The Jovian magnetospheric magnetic and electric fields: Effects of the interplanetary magnetic field  

Microsoft Academic Search

The purpose of this paper is to study using a constructed magnetospheric magnetic field model the electric fields and plasma motions caused by Jupiter's rotation and the solar wind MHD generator. Analysis of observations shows that a complicated differential rotation system is operating in the jovian magnetosphere. Observational data also reveal the presence of solar wind plasma in the jovian

E. S. Belenkaya

2004-01-01

135

Difference Between Magnetic Clouds and Non-cloud Ejecta in the Interplanetary Medium  

Microsoft Academic Search

Solar cycle 23 has witnessed the accumulation of data on an unprecedented number of coronal mass ejections (CMEs) at the Sun and in the interplanetary (IP) medium, thanks to the large array of spaceborne observatories such as SOHO, Wind, and ACE. These observations have helped us make significant progress on the structure and evolution of CMEs in the inner heliosphere.

N. Gopalswamy

2008-01-01

136

A study of the expansion and distortion of the cross section of magnetic clouds in the interplanetary medium  

NASA Astrophysics Data System (ADS)

Herein an approach is presented to determine the expansion and distortion of the cross section of magnetic clouds (MCs) in their evolution in the interplanetary medium. This approach, based on the improvement of our previous elliptical cross-section model for the magnetic topology of MCs, gives analytical expressions for ? and ? which incorporate the expansion of the cross section of clouds. Our starting point is the assumption of a spatially uniform j?, the normal component of the plasma current density to the cross section of the cloud. As it is described in the text, this expansion provides a time dependency of the three components of the plasma current density. The main physical consequences of this behavior are discussed. Fittings to eight selected MCs of years 2000 and 2001 with different magnetic field profiles are presented.

Hidalgo, M. A.

2003-08-01

137

Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007), but here during northward Interplanetary Magnetic Field (IMF). The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression) in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP) expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 ?t, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc.) for which predictions are proposed to test furthermore our simulation technique.

Baraka, S.; Ben-Jaffel, L.

2011-01-01

138

The Jovian magnetospheric magnetic and electric fields: Effects of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to study using a constructed magnetospheric magnetic field model the electric fields and plasma motions caused by Jupiter's rotation and the solar wind MHD generator. Analysis of observations shows that a complicated differential rotation system is operating in the jovian magnetosphere. Observational data also reveal the presence of solar wind plasma in the jovian magnetosphere. However, the processes by which it crosses the magnetopause are left unexplained. Here we present an approach to the fundamental problem of the nature of the global plasma convection and corotation in the jovian magnetosphere. The constructed model allows us to map the various parts of the magnetosphere into the ionosphere and vice versa in order to correlate them with the different regions and processes.

Belenkaya, E. S.

2004-04-01

139

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

140

A Simulation Study of the Response of the Jovian Magnetosphere to Changes in the Solar Wind Dynamic Pressure and Interplanetary Magnetic Field  

Microsoft Academic Search

A rapidly rotating equatorial current sheet and plasma sheet dominates the Jovian magnetosphere. We have used a global magnetohydrodynamic (MHD) simulation to investigate the effects of changes in the solar wind dynamic pressure and interplanetary magnetic field (IMF) on the Jovian magnetospheric configuration with emphasis on changes in the equatorial plasma sheet. We have carried out three numerical experiments: 1.

R. J. Walker; T. Ogino; K. Fukazawa

2003-01-01

141

Observations of the response time of high-latitude ionospheric convection to variations in the interplanetary magnetic field using EISCAT and IMP8 data  

Microsoft Academic Search

We have combined 300 h of tristatic mea- surements of the field-perpendicular F region iono- spheric flow measured overhead at Tromsø by the EISCAT UHF radar, with simultaneous IMP-8 mea- surements of the solar wind and interplanetary magnetic field (IMF) upstream of the Earth's magnetosphere, in order to examine the response time of the ionospheric flow to changes in the

H. Khan; S. W. H. Cowley

1999-01-01

142

A statistical study of the ionospheric convection response to changing interplanetary magnetic field conditions using the assimilative mapping of ionospheric electrodynamics technique  

Microsoft Academic Search

We examine 65 ionospheric convection changes associated with changes in the Y and Z components of the interplanetary magnetic field (IMF). We measure the IMF reorientations (for all but six of the events) at the Wind satellite. For 22 of the events the IMF reorientation is clearly observed by both Wind and IMP 8. Various methods are used to estimate

A. J. Ridley; Gang Lu; C. R. Clauer; V. O. Papitashvili

1998-01-01

143

The effects of the solar magnetic polarity and the solar wind velocity on Bz-component of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

We have studied the effect of both solar magnetic polarity and the solar wind velocity on the Bz-component of the interplanetary magnetic field, IMFBz, for the minimum activity of the solar cycles 21, 22, 23 and 24. We made a statistical study of IMFBz in the first section which is considered as an extension of Lyatsky et al. (2003). They made a statistical study of IMFBz for two periods of minimum solar activity 22 and 23 related to 1985-1987 and 1995-1997 when the solar magnetic field had opposite polarity. Our results seem to be consistent with the results obtained by Lyatsky et al. (2003). We found that there is a dependence of IMFBz on the IMFBx and the solar magnetic polarity for the minimum periods of the selected four solar cycles. In addition, we found that there is a dependence of IMFBz on the solar wind velocity.

Youssef, M.; Mahrous, A.; Mawad, R.; Ghamry, E.; Shaltout, M.; El-Nawawy, M.; Fahim, A.

2012-04-01

144

Model of the high-latitude ionospheric convection pattern during southward interplanetary magnetic field using DE 2 data  

SciTech Connect

Data from the polar-orbiting satellite DE 2 are used to calculate one-dimensional electrostatic potential distributions across the polar cap region. Using passes that lie within {plus minus} 3 hours MLT of the dawn-dusk line, various parameters of the polar potential distribution (location and magnitude of the maxima and minima, location of the zero potential point, etc.) are analyzed in relation to each other and to the interplanetary magnetic field (IMF). The resulting dependences are used to derive a two-dimensional model of the distribution of the electrostatic potential in the high-latitude ionosphere during times of southward IMF. This model can be generated using as inputs either the ionospheric potential parameters or, based on the relationships analyzed here, the IMF conditions. The capabilities of the resulting mathematical model are illustrated, and the importance of retaining a flexibility in the model to accommodate individual observations is emphasized.

Hairston, M.R.; Heelis, R.A. (Univ. of Texas, Richardson (United States))

1990-03-01

145

Characteristics of polar-cap precipitation and their dependence on the interplanetary magnetic field and the solar wind  

SciTech Connect

Work completed on the nature of the precipitation occuring in the polar cap and its relationship to the state of the solar wind and the interplanetary magnetic field is reviewed. This work has shown that there are two states of polar-cap precipitation; an active state occurring when the IMF B/sub z/ component is positive in which polar showers or polar squalls occur over much of the cap and a quiet state occurring when the IMF B/sub z/ is negative in which only the unperturbed polar rain is observed. The two states occur with approximately equal frequency. The characteristics of both the precipitating electrons and ions for the two states and the variation in these characteristics with the orientation of the IMF and the state of the solar-wind plasma are discussed along with the implications of these observations as to the mechanisms leading to these two states.

Hardy, D.A.; Gussenhoven, M.S.; Riehl, K.; Burkhardt, R.; Heinemann, N.

1986-01-01

146

Cluster observations of the local energy transfer at the dayside magnetopause under steady interplanetary magnetic field conditions  

NASA Astrophysics Data System (ADS)

We use the multi-spacecraft mission Cluster to make observational estimates of the local energy transfer across the dayside high-latitude magnetopause during an interval of continuous reconnection. The instantaneous power input is estimated from jxB observations from the FGM instrument and CIS magnetosheath velocity observations and is compared to E·j measurements with the electric field deduced from the EFW instrument. The good agreement between these two independent measurements validates the quality of the technique. The energy flux is estimated during ten complete magnetopause crossings under steady southward and dawnward interplanetary magnetic field conditions (IMF). In most cases we find that there is no or little flow of energy across the magnetopause boundary as expected on the dayside magnetopause where the magnetic tension is mainly perpendicular to the solar wind flow. However, at some crossings when Cluster observes high-speed plasma jets energy it is found to be transferred from the magnetic field to the particles as a result of the magnetic reconnection process. Furthermore, it is possible to make estimations of the inflow reconnection velocity from the magnitude of the local energy estimate. This was found to be in reasonable agreement with the results from standard techniques. However, the inflow velocity as well as the energy transfer rate varies considerably during the course of the ten crossings. This may support the previous theory that the reconnection rate is continuously active but its rate is modulated.

Rosenqvist, L.; Vaivads, A.; Retino, A.; Stenberg, G.

2006-12-01

147

Revised Landau damping rates of magnetohydrodynamic waves in hot magnetized equilibrium plasmas and its consequences for cosmic ray transport in the interplanetary medium  

NASA Astrophysics Data System (ADS)

A relativistic theory of transverse oscillations in hot, magnetized, isotropic equilibrium plasmas is presented. The special theory of relativity enters the description with the requirement that the particle masses depend on the particle velocities which themselves are limited by the speed of light. Using the relativistic Maxwell-Boltzmann-Jüttner (MBJ) distribution correctly describing the equilibrium state of a plasma, we formulate the dispersion relations for subluminal as well as superluminal waves, using the Trubnikov representation. For Landau damping of transverse wave modes, the so-called cyclotron damping, an analytical expression generalizing earlier results to a relativistically correct form is derived. The theory is applied to an electron-proton plasma, the main constituents of the interplanetary medium. Special consideration is given to the regime of weak damping of low- and high-frequency waves in the interplanetary plasma. The resulting dispersion relations and damping rates are used to determine cosmic ray transport parameters in the interplanetary medium, in particular the mean free path of solar energetic particles and the related modulation parameter of galactic cosmic rays in a simple diffusion-convection modulation model. It is shown that at particle rigidities below about 109V/c the mean free path and the modulation parameter are significantly different for cosmic ray protons, negatrons, and positrons because of the different handedness of the particles in the ordered interplanetary magnetic field and the different Landau damping rates of right-handed and left-handed circularly polarized plasma waves.

Schlickeiser, R.; Fichtner, H.; Kneller, M.

1997-03-01

148

Investigation of the interhemispheric asymmetry in reverse convection near solstice during northward interplanetary magnetic field conditions using MHD simulations  

NASA Astrophysics Data System (ADS)

reverse convection potential under northward interplanetary magnetic field (IMF) is significantly larger in the summer ionosphere than in the winter. In this study, we use the Coupled Magnetosphere-Ionosphere-Thermosphere model to simulate a Northern Hemisphere winter event where observations have shown asymmetry in both the reverse convection strength between hemispheres and the magnetic field topology associated with the ionospheric reverse convection cells. We show that a topological asymmetry, in which reconnection between the geomagnetic field and the IMF occurs in the summer hemisphere, first drives the interhemispheric asymmetry in reverse convection strength rather than an interhemispheric asymmetry in ionospheric conductivity. We find a large amount of overdraped open magnetic flux connected to the summer hemisphere that results from this reconnection bypasses the winter hemisphere x line and reconnects with the IMF again in the summer hemisphere lobe. This leads to a large amount of circulating lobe flux in the summer hemisphere and stagnant lobe flux in the winter hemisphere, while maintaining a divergence-free field, as well as the weaker reverse convection potential in the winter hemisphere ionosphere.

Wilder, F. D.; Eriksson, S.; Wiltberger, M.

2013-07-01

149

High-latitude ionospheric convection models derived from Defense Meteorological Satellite Program ion drift observations and parameterized by the interplanetary magnetic field strength and direction  

NASA Astrophysics Data System (ADS)

A series of new high-latitude ionospheric convection models have been constructed using Defense Meteorological Satellite Program (DMSP) thermal ion drift measurements. The models are obtained by sorting cross polar cap electrostatic potentials into magnetic latitude/magnetic local time bins. A regression analysis of the potentials in each bin is then implemented for establishing the relationships to the interplanetary magnetic field (IMF) for three seasons: summer, winter, and equinox. A linear modeling formula for the ionospheric electrodynamics (LIMIE) yields a convection response to the average solar wind (i.e., the ``quasi-viscous'' interaction) and to changes in the IMF By, Bz <= 0, and Bz > 0 components. The modeled convection is a superposition of the first two parameters with either the IMF Bz <= 0 or the Bz > 0 component. A global model is created by fitting the regression analysis results to a spherical harmonic function. The resulting DMSP-based ionospheric convection model (DICM) is fully parameterized by the IMF strength and direction. With this model, ionospheric convection patterns can be generated for any IMF configuration during quiet to moderate geomagnetic conditions. We compare the DICM model with other available high-latitude convection patterns organized by the IMF. The new elements in DICM are its quasi-viscous and separate IMF-dependent terms for both the northern and southern polar regions, which are not explicitly found in other ionospheric convection studies. The DICM's seasonal dependence and interhemispheric symmetry/asymmetry features show that the summer cross-polar potentials are 10-15% smaller than the winter potentials. The latter is in agreement with the seasonal dependence of field-aligned currents and with the voltage-current relationship required for the proper magnetosphere-ionosphere coupling.

Papitashvili, Vladimir O.; Rich, Frederick J.

2002-08-01

150

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

PubMed

The radiation absorbed by astronauts during interplanetary flights is mainly due to cosmic rays of solar origin (SCR). In the most powerful solar flares the dose absorbed in few hours can exceed that cumulated in one year of exposition to the galactic component of cosmic rays (GCR). At energies above the minimum one needed to cross the walls of the spaceship there are extrapolations and guesses, but no data, on the angular distribution of SCR's, an information that is necessary for establishing whatever defence strategy. It was therefore proposed of sending to Mars a measurement device, that should continuously collect data during the travel, and possibly also in the orbit around Mars and on the Mars surface. The device should identify the particle and privilege the completeness in the measurement of its parameters. In fact the high energy electrons travel at speed of the light and could be used in the and future dangerous proton component. Also the much less abundant but individually more dangerous ions should be identified. The device should indeed include a magnetic spectrometer and a high granularity range telescope, and a good time of flight measurement. ASI is supporting an assessment study of a possible mission of such a device on board of the 2005 probe to Mars. A parallel technical study is also in progress to define the workable techniques and the possible configurations of a system of magnetic lenses for protecting the crew of a spaceship. PMID:11776989

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

2001-01-01

151

Strategies to Forecasting Space Weather Events from Uncovering and Predicting Patterns of the Interplanetary Magnetic Field Inside Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

The interplanetary magnetic field (IMF) inside coronal mass ejections (CME) is a major factor in controlling terrestrial space weather events. Our ability to model, and thus predict, CME propagation is constantly improving. However, our ability to predict the detailed and relevant magnetic structure inside CMEs is not necessarily following behind at the same rate. Nev-ertheless, it is highly desirable to predict the IMF structure at the L1 point on intermediate timescales up to half a day ahead of time. In this presentation, we discuss how pattern recog-nition of at solar wind IMF data at the L1 point could be part of a forecast system for the IMF and terrestrial space weather events on these intermediate time scales. Our approach is to clas-sify the temporal patterns of the IMF inside CMEs at relevant time scales by classifying solar wind time series segments of various lengths using Kohonen Self-Organizing Maps. We present how these networks view the time history of CMEs passing over the L1 point. We discuss how this classification of temporal patterns can be used in predicting the future temporal develop-ment of the solar wind IMF in CMEs. Ultimately, our approach is geared towards enabling the development of a probability-driven space weather forecasting approach that combines at a minimum L1 in situ and solar remote observations, but is also open to (and very likely will require) model-based techniques.

Jahn, Jorg-Micha; Elliott, H. A.

152

Jovian electron jets in interplanetary space  

NASA Astrophysics Data System (ADS)

The COSPIN/KET experiment onboard Ulysses has been monitoring the flux of ˜ 3-20 MeV electrons in interplanetary space since the launch of Ulysses in October 1990. The origin of these electrons has been known for a long time to be the Jovian magnetosphere. Propagation models assuming interplanetary diffusion of these electrons in the ideal Parker magnetic field were successfully developed in the past. The average electron flux measured by our experiment agrees with these models for most of the times before and after the Jovian flyby of February 1992, i.e. in and out of the ecliptic down to 28° S of heliographic latitude for the last data presented here (end of March 1993). However, in addition to this average flux level well accounted for by diffusion in an ideal Parker field, we have found very short duration electron events which we call "jets", characterized by: (i) a sharp increase and decrease of flux; (ii) a spectrum identical to the electron spectrum in the Jovian magnetosphere; and (iii) a strong first-order anisotropy. These jets only occur when the magnetic field at Ulysses lies close to the direction of Jupiter, and most of the time (86% of the events) points outwards from Jupiter, i.e. has the same polarity after the flyby as the Jovian dipole (North to South). These events are interpreted as crossings by Ulysses of magnetic flux tubes or sheets directly connected to the location of the Jovian magnetosphere from which electrons escape into interplanetary space. The average thickness of these sheets is ˜ 10 11cm or ˜ 14 Jovian radii. These jets are clearly identified up to 0.4 a.u. before the Jupiter flyby in the ecliptic plane, and up to 0.9 a.u. out of the ecliptic. Moreover, the characteristic rocking of the electron spectrum in the Jovian magnetosphere with a 10 h periodicity is found to be present during the jets, and predominantly during them. In the past, this modulation has been reported to be present in interplanetary space as far as 1 a.u. upwind of Jupiter, a fact which cannot be accounted for by diffusion in the average Parker magnetic field. Our finding gives a simple explanation to this phenomenon, the 10 h modulation being carried by the "jet" electrons which travel with no appreciable diffusion along magnetic field lines with a direction far from the ideal Parker spiral.

Ferrando, P.; Ducros, R.; Rastoin, C.; Raviart, A.

1993-11-01

153

Space environment of Mercury at the time of the first MESSENGER flyby: Solar wind and interplanetary magnetic field modeling of upstream conditions  

Microsoft Academic Search

The first flyby of Mercury by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft occurred on 14 January 2008. In order to provide contextual information about the solar wind (SW) properties and the interplanetary magnetic field near the planet, we have used an empirical modeling technique combined with a numerical physics-based SW model. The Wang-Sheeley-Arge (WSA) method uses

Daniel N. Baker; Dusan Odstrcil; Brian J. Anderson; C. Nick Arge; Mehdi Benna; George Gloeckler; Jim M. Raines; David Schriver; James A. Slavin; Sean C. Solomon; Rosemary M. Killen; Thomas H. Zurbuchen

2009-01-01

154

Interplanetary magnetic field at ?9 AU during the declining phase of the solar cycle and its implications for Saturn's magnetospheric dynamics  

Microsoft Academic Search

We study the interplanetary magnetic field (IMF) data obtained by the Cassini spacecraft during a ?6.5-month interval when the spacecraft was approaching Saturn at heliocentric distances between ?8.5 and ?8.9 AU. It is shown that the structure of the IMF is consistent with that expected to be formed by corotating interaction regions (CIRs) during the declining phase of the solar

C. M. Jackman; N. Achilleos; E. J. Bunce; S. W. H. Cowley; M. K. Dougherty; G. H. Jones; S. E. Milan; E. J. Smith

2004-01-01

155

Interplanetary magnetic field at ~9 AU during the declining phase of the solar cycle and its implications for Saturn's magnetospheric dynamics  

Microsoft Academic Search

We study the interplanetary magnetic field (IMF) data obtained by the Cassini spacecraft during a ~6.5-month interval when the spacecraft was approaching Saturn at heliocentric distances between ~8.5 and ~8.9 AU. It is shown that the structure of the IMF is consistent with that expected to be formed by corotating interaction regions (CIRs) during the declining phase of the solar

C. M. Jackman; N. Achilleos; E. J. Bunce; S. W. H. Cowley; M. K. Dougherty; G. H. Jones; S. E. Milan; E. J. Smith

2004-01-01

156

Intense interplanetary magnetic fields observed by geocentric spacecraft during 1963--1975  

Microsoft Academic Search

Ninety-two percent of the intense magnetic fields (>13 ..gamma..) observed at 1 AU During solar cycle 20 (1963--1975) were associated with shocks, stream interfaces, or cold magnetic enhancements (CMF's). Most (52%) of the magnetic field intensity enhancements occurred at stream interfaces; 27% occurred behind shocks without interfaces; and 11% occurred in CME's. The most intense fields (25--37 ..gamma..) followed shocks.

L. F. Burlaga; J. H. King

1979-01-01

157

Interplanetary magnetic field at ˜9 AU during the declining phase of the solar cycle and its implications for Saturn's magnetospheric dynamics  

NASA Astrophysics Data System (ADS)

We study the interplanetary magnetic field (IMF) data obtained by the Cassini spacecraft during a ˜6.5-month interval when the spacecraft was approaching Saturn at heliocentric distances between ˜8.5 and ˜8.9 AU. It is shown that the structure of the IMF is consistent with that expected to be formed by corotating interaction regions (CIRs) during the declining phase of the solar cycle, with two sectors during each solar rotation, and crossings of the heliospheric current sheet generally embedded within few-day higher-field compression regions, separated by several-day lower-field rarefaction regions. This pattern was disrupted in November 2003, however, by an interval of high activity on the Sun. These data have then been employed to estimate the voltage associated with open flux production at Saturn's magnetopause using an empirical formula adapted from Earth. The results show that the CIR-related structuring of the IMF leads to corresponding structuring of the interplanetary interaction with Saturn's magnetosphere and hence also to intervals of very different dynamical behavior. During few-day compression regions where the IMF strength is ˜0.5-2 nT, the average Dungey cycle voltage is estimated to be ˜100 kV, such that the open flux produced over such intervals is ˜30-40 GWb, similar to the typical total amount present in Saturn's magnetosphere. The magnetosphere is thus significantly driven by the solar wind interaction during such intervals. During some rarefaction intervals, on the other hand, the field strength remains ˜0.1 nT or less over several days, implying reconnection voltages of ˜10 kV or less, with negligible production of open flux. The magnetosphere is then expected to enter a quiescent state, dominated by internal processes. Overall, ˜100 GWb of open flux is estimated to be produced during each ˜25-day solar rotation, about 3 times the typical flux contained in the tail, and sufficient to drive three to five substorms. We point out, however, that CIR-related variations in solar wind dynamic pressure will also occur in synchronism with the field variations, which may also play a role in modulating the open flux in the system, thus reinforcing the synchronization of the pattern of growth and decay of open flux to the CIR pattern. Estimates of open flux production associated with the period of strong solar activity indicate that major magnetospheric dynamics were excited by reconnection-mediated solar wind interaction during this interval.

Jackman, C. M.; Achilleos, N.; Bunce, E. J.; Cowley, S. W. H.; Dougherty, M. K.; Jones, G. H.; Milan, S. E.; Smith, E. J.

2004-11-01

158

Energy filter effect for solar wind particle entry to the plasma sheet via flank regions during southward interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

Several mechanisms have been used to explain solar wind plasma entry into the plasma sheet in the magnetotail. In this paper, we focus on the gradient drift entry (GDE) process in the equatorial flanks of the magnetosphere, based on the magnetopause picture of a tangential discontinuity with a small tangential electric field as was suggested by Alfvén (1968). We discuss the GDE efficiency in different conditions using the adiabatic theory. It can be clearly shown that the GDE efficiency is much lower during southward interplanetary magnetic field (IMF), with a strong energy filter effect for incoming solar wind particles. Given a typical condition, a critical energy for particle entry is calculated to be several kiloelectron volts. Only those particles with higher energy can penetrate the magnetopause, a condition which can be also proved by test particle simulations. The lower efficiency than that during northward IMF during periods of southward IMF is in agreement with the different properties of the plasma sheet observed, i.e., hot and tenuous when the IMF is southward, cold and dense for northward IMF.

Zhou, X.-Z.; Pu, Z. Y.; Zong, Q.-G.; Xie, L.

2007-06-01

159

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

NASA Astrophysics Data System (ADS)

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

Luo, H.; Chen, G. X.

2012-04-01

160

Polar cusp and vicinity under strongly northward interplanetary magnetic field on April 11, 1997: Observations and MHD simulations  

NASA Astrophysics Data System (ADS)

We present a correlative case study of the solar wind interaction with the magnetosphere using in situ observations of the polar cusp and surrounding regions, ground-based and low-altitude spacecraft polar cap observations, and global MHD simulations during an extended period of strongly northward interplanetary magnetic field (IMF) on April 11, 1997. Within this extended period of strongly northward IMF, the Polar spacecraft entered a region with magnetosheath-like plasma and field lines above the polar cusp. Data from multiple instruments on Polar showed that the observed signatures can be interpreted as Polar entering the reconnection layer and crossing the current layer associated with it. The magnetosheath-like field lines encountered by Polar have just reconnected poleward of the polar cusp in the north. The reversed ionospheric convection patterns derived from the assimilative mapping of ionospheric electrodynamics (AMIE) technique show the reversed convection over the polar cap due to high-latitude reconnection throughout the whole interval. MHD simulations were performed using solar wind parameters observed by Wind, supporting the cusp reconnection interpretation.

Le, G.; Raeder, J.; Russell, C. T.; Lu, G.; Petrinec, S. M.; Mozer, F. S.

2001-10-01

161

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

NASA Astrophysics Data System (ADS)

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 entire polar cap, the region of open field lines are in darkness. For many years optical observation had been conducted in the Antarctica, mostly at South Pole station, with focus on studying dayside auroral phenomena that may be associated with the reconnection process between the interplanetary and the Earth's field. Although a great deal has been learned from such ground based observations, satellite based global views especially those from the IMAGE satellite proton imager, that is quite blind to dayside solar produced luminosities, contributed significantly to our understanding of the global scale morphology of the high latitude regions. Ground based optical observatory arrays are still very useful for providing the small to medium scale view of the various phenomena and the development of such array of observatories in Antarctica are still being actively pursued. Although it is not its primary purpose, the ground based THEMIS array will also be on line in the near future and it will make observations of the nightside polar cap region. In the near future there will be several arrays in operation to study the region of field lines that map from the ground into the interplanetary medium.

Mende, S. B.

2005-12-01

162

Dynamical evolution of interplanetary magnetic fields and flows between 0. 3 AU and 8. 5 AU: entrainment  

SciTech Connect

The radial evolution of interplanetary flows and associated magnetic fields between 0.3 AU and 8.5 AU was analyzed using data from Helios 1 and Voyager 1, respectively. During a 70-day interval in 1980 Voyager 1 observed two streams which appeared to be recurrent and which had little fine structure. The corresponding flows observed by Helios 1 were much more complex, showing numerous small streams, transient flows and shocks as well as a few large corotating streams. It is suggested that in moving to 8 AU the largest corotating streams swept up the slower flows (transient and/or corotating streams) and shocks into a relatively thin region in which they coalesced to form a single large-amplitude compression wave. We refer to this combined process of sweeping and coalescence as ''entrainment''. The resulting large-amplitude compression wave is different from that formed by the steepening of a corotating stream from a coronal hole, because different flows from distinct sources, with possibly different composition and magnetic polarity, are brought together to form a single new structure. As a result of entrainment, memory of the sources and flow configurations near the sun is lost. Small-scale features are erased as the flows move outward and energy is transferred from small scales to large scales by entrainment. Thus in the outer solar system the structure of the solar wind may be dominated by large scale pressure waves (compressions followed by rarefractions) separated by several AU. Beyond several AU most of the compression waves are no longer driven by streams, and the compression waves expand freely. At large distances (> or approx. = 25 AU) they will have interacted extensively with one another producing yet another state of the solar wind, with fewer large-scale non-uniformities and more small-scale non-uniformities.

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

1983-05-01

163

The day time electric field disturbances at equator and associated changes in interplanetary electric field and the ionospheric plasma density during intense magnetic storm periods  

NASA Astrophysics Data System (ADS)

During periods of enhanced geomagnetic activity, the low latitude ionospheric plasma densities, electric fields and currents undergo strong perturbations. The direct penetration of the high latitude electric field to lower latitudes, and the disturbance dynamo, both play a significant role in restructuring the storm time equatorial ionosphere and thermosphere. Variations of the H component of the geomagnetic field at equator and at low latitude stations are investigated to show the counter electrojet (CEJ) events are associated with electric fields from Field aligned currents (FAC). It is well known that FAC are controlled by the interplanetary magnetic fields (IMF) and electric fields from the FAC can direct penetrate to equatorial ionosphere. Thus, the penetrated electric field plays a crucial part in the development of geomagnetic disturbances and ionospheric plasma motion in the low latitude and in the inner magnetosphere. The effect of space weather related perturbations in electric fields and currents in the equatorial and low latitude magnetic field associated with the changes in magnetospheric convection can be investigated using simultaneous observations from ground geomagnetic data and ionospheric data and satellite data during the intense magnetic storm periods. Equatorial magnetic field variations and counter electrojet events will be examined for magnetically disturbed periods in association with changes in interplanetary magnetic field and auroral electric fields.

Bhaskara, Veenadhari; Alex, S.; Singh, R.

164

Energetic charged particles as probes of the geometry and topology of the interplanetary magnetic field: The detection of coronal mass ejections  

SciTech Connect

The large-scale structure of the interplanetary magnetic field has been inferred almost exclusively from single point measurements obtained by spacecraft. It has recently been appreciated that energetic charged particles can yield new information about the interplanetary fields since they originate at the sun and are constrained to follow the field lines out to the points of observation. The author reviews the results of particle probes, particularly bidirectional flows (BDFs), to detect coronal mass ejections (CMEs). While a good association, possibly one-to-one, has been assumed between BDFs and CMEs, there is now evidence to suggest that some CMEs do not produce BDFs and that many BDFs are not due to CMEs.

Kahler, S.W.

1994-09-01

165

EVOLUTION OF A CORONAL MASS EJECTION AND ITS MAGNETIC FIELD IN INTERPLANETARY SPACE  

SciTech Connect

This Letter presents the first theoretical study of the dynamics of a coronal mass ejection (CME) observed by STEREO-A/B. The CME was continuously tracked by SECCHI-A, providing position-time data from eruption to 1 AU. The ejecta was intersected by STEREO-B at 1 AU, where the magnetic field and plasma parameters were measured. The observed CME trajectory and the evolution of the CME magnetic field are modeled using the semianalytic erupting flux-rope model. It is shown that the best-fit theoretical solution is in good agreement-within 1% of the measured CME trajectory in the 1 AU field of view-and is consistent with the in situ magnetic field and plasma data at 1 AU.

Kunkel, V. [George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Chen, J. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2010-06-01

166

Electric potential patterns in the northern and southern polar regions parameterized by the interplanetary magnetic field  

Microsoft Academic Search

Electric potential patterns have been obtained from the IZMIRAN electrodynamic model (IZMEM) for the northern and southern polar regions during summer, winter, and equinox. The model is derived from a large quantity of high-latitude ground-based geomagnetic data (above {+-} 57° corrected geomagnetic latitude) at all magnetic local time hours. A linear regression analysis technique has been used to obtain the

V. O. Papitashvili; B. A. Belov; D. S. Faermark; Ya. I. Feldstein; S. A. Golyshev; L. I. Gromova; A. E. Levitin

1994-01-01

167

Electric potential patterns in the northern and southern polar regions parameterized by the interplanetary magnetic field  

Microsoft Academic Search

Electric potential patterns have been obtained from the IZMIRAN electrodynamic model (IZMEM) for the northern and southern polar regions during summer, winter, and equinox. The model is derived from a large quantity of high-latitude ground-based geomagnetic data (above +\\/- 57 deg corrected geomagnetic latitude) at all magnetic local time hours. A linear regression analysis technique has been used to obtain

V. O. Papitashvili; B. A. Belov; D. S. Faermark; Ya. I. Feldstein; S. A. Golyshev; L. I. Gromova; A. E. Levitin

1994-01-01

168

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

Microsoft Academic Search

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

D. A. Roberts

1990-01-01

169

Mean Interplanetary Magnetic Field Measurement Using the ARGO-YBJ Experiment  

Microsoft Academic Search

The Sun blocks cosmic-ray particles from outside the solar system, forming a detectable shadow in the sky map of cosmic rays detected by the ARGO-YBJ experiment in Tibet. Because the cosmic-ray particles are positively charged, the magnetic field between the Sun and the Earth deflects them from straight trajectories and results in a shift of the shadow from the true

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

2011-01-01

170

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

171

Distribution of convection potential around the polar cap boundary as a function of the interplanetary magnetic field  

SciTech Connect

Plasma flow data from the AE-C, AE-D and DE 2 satellites have been used to systematically study the distribution of the convection potential around the polar cap boundary under a variety of different interplanetary magnetic field (IMF) conditions. For either a garden hose (B{sub x}B{sub y}<0) or ortho-garden hose (B{sub x}B{sub y}>0) orientation of the IMF, the potential distribution is mainly affected by the sign of B{sub y}. In the northern hemisphere, the zero potential line (which separates the dusk convection cell from the dawn cell) on the dayside shifts duskward as B{sub y} changes from positive to negative. But in the southern hemisphere, a dawnward shift has been found, although the uncertainties are large. The typical range of displacement is about {plus minus}1.5 hours MLT. Note that this shift is in the opposite direction from most simple schematic models of ionospheric flow; this reflects the fact that the polar cap boundary is typically more poleward than the flow reversal associated with the region 1 current system, which shifts in the opposite direction. Thus the enhanced flow region typically crosses noon. In most cases a sine wave is an adequate representation of the distribution of potential around the boundary. However, in a few cases the data favors (at the 80% confidence level) a steeper gradient near noon, more indicative of a throat. The potential drop at the duskside boundary is almost greater than at the dawnside boundary. A slight duskward shift of the patterns observed as the IMF changes from garden hose to ortho-garden hose conditions. Analytic equipotential contours, given the potential function as a boundary condition, are constructed for several IMF conditions.

Lu, G.; Reiff, P.H.; Karty, J.L. (Rice Univ., Houston, TX (USA)); Hairston, M.R.; Heelis, R.A. (Univ. of Texas, Richardson (USA))

1989-10-01

172

Effect of the interplanetary magnetic field on the distribution of electric fields in the polar ionosphere  

NASA Astrophysics Data System (ADS)

Heppner (1972), in an analysis of satellite data, observed 12 types of electric-field distributions in the polar ionosphere along the morning-evening meridian. In the present paper it is shown that these distribution types can be described by the analytical model of Uvarov and Barashkov (1984). In this model the excitation of the electric fields is investigated by solving the set of continuity equations for current in three regions (the north and south polar caps and a region outside the caps) with allowance for the magnetic conjugacy of the ionosphere in the two hemispheres.

Uvarov, V. M.; Barashkov, P. D.

1985-08-01

173

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

NASA Astrophysics Data System (ADS)

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. 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-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; Tylka, Allan J.; Ng, Chee K.; Wang, Yi-Ming; Dietrich, William F.

2013-10-01

174

Cosmic Ray Intensity Variation during the Passage of Interplanetary Disturbances  

NASA Astrophysics Data System (ADS)

An investigation has been made so as to study the cosmic-ray decreases occurring during 2006 with respect to the arrival times of interplanetary shocks and magnetic clouds. We have identified three interplanetary magnetic cloud events during 5, February 2006, 13 April 2006 and 14 April 2006. The interplanetary magnetic field (B), north south component of interplanetary magnetic field (Bz), solar wind velocity, sunspot number (R) and disturbance storm time index (Dst) associated with these events has been studied in the present work. The data (neutron monitor count rate) from Newark Neutron Monitor 9NM64 has been used. The north south component of IMF (Bz) produce large geomagnetic disturbance on the onset of interplanetary magnetic clouds. The deviations in the interplanetary and solar wind plasma parameters are significantly correlated to the magnetic cloud events. The increase in Dst index, sunspot number (R) and Bz after the magnetic cloud event produces increase in cosmic ray intensity.

Agarwal Mishra, Rekha; Agarwal Mishra, Rekha; Mishra, Rajesh Kumar

175

Topology and convection of a northward interplanetary magnetic field reconnection event  

NASA Astrophysics Data System (ADS)

>From observations and global MHD simulations, we deduce the local and global magnetic topology and current structure of a northward IMF reconnection event in the dayside magnetopause. The ESA four-satellite Cluster suite crossed the magnetopause at a location mapping along field lines to an ionospheric H-alpha emission observed by the IMAGE spacecraft. Therefore, we seek reconnection signatures in the Cluster data. From the four-point Cluster observations, we develop a superposed epoch method to find the instantaneous x-line, its associated current sheet, and the nature of the reconnecting particle flows. This method is unique in that it removes the motion of the hyperbolic structure and the magnetopause relative to the spacecraft. We detect singular field line reconnection--planar hyperbolic reconnecting fields superposed on an out-of- plane field. We also detect the non-ideal electric field that is required to certify reconnection at locations where the magnetic field does not vanish, and estimate a reconnection electric field of - 4 mV/m. The current sheet appears bifurcated, embedding a 30 km current sheet of opposite polarity within a broader current sheet about 130 km thick. Using a resistive MHD simulation and ionospheric satellite data, we examine the same event at global length scales. This gives a 3D picture of where reconnection occurs on the magnetopause for northward IMF with B x and B y components and a tilted dipole field. It also demonstrates that northward IMF 3D reconnection couples the reconnection electric field and field-aligned currents to the ionosphere, driving sunward convection in a manner that agrees with satellite measurements of sunward flows. We find singular field line reconnection of the IMF with both open and closed field lines near nulls in both hemispheres. The reconnection in turn produces both open and closed field lines. We discuss for the first time how line-tying in the ionosphere and draping of open and IMF field lines produce a torsion of the reconnecting singular magnetic field lines within the magnetopause. The simulation and data show that magnetopause reconnection topology is three-dimensional in a way that challenges accepted models of neutral lines and x-lines with guide fields.

Wendel, Deirdre E.

176

Modeling the Evolution of Plasma Phase Space Density During a Period of Northward Interplanetary Magnetic Field  

NASA Astrophysics Data System (ADS)

The goal of this investigation is to understand the formation of the plasma sheet, and why the observational data shows differences in the plasma energy distribution between the dawn and dusk flank. Understanding the formation of the plasma sheet is important because the plasma sheet is the main source of particles to the ring current and the radiation belts. These populations become enhanced during intervals of northward IMF. To carry out this study, we model a plasma sheet refilling after a northward turning of the IMF. The goal is to compute the phase space density of simulated particles by mapping forwards in time the phase space densities of plasma sheet ions obtained from the Geotail spacecraft. We have used northward IMF upstream solar wind conditions, corresponding with the upstream parameters used to bin the Geotail dataset, to drive the electric and magnetic field models in our Lorentz force particle tracer, which are used to trace ion trajectories. Our particle tracer uses a Tsyganenko magnetic field model and a Weimer electric potential model, and it assumes that there are no particle losses, so that according to Liouville’s Theorem the phase space density is constant along the generated particle trajectories. The initial and boundary conditions for the phase space mapping are based on Geotail data. We compare our simulated phase space densities with the corresponding Geotail data and discuss the differences between the simulations and the observations. Our results demonstrate one of the sources of the observed dawn-dusk asymmetry during times of northward IMF, which is asymmetric plasma transport in the magnetosphere.

Mata, W. J.; Lemon, C.; Lyons, L. R.; Wang, C.

2009-12-01

177

Solar wind energy input during prolonged, intense northward interplanetary magnetic fields: A new coupling function  

NASA Astrophysics Data System (ADS)

Sudden energy release (ER) events in the midnight sector auroral zone during intense (B > 10 nT), long-duration (T > 3 h), northward (N = Bz > 0 nT) IMF magnetic clouds (MCs) during solar cycle 23 (SC23) have been examined in detail. The MCs with northward-then-southward (NS) IMFs were analyzed separately from MCs with southward-then-northward (SN) configurations. It is found that there is a lack of ER/substorms during the N field intervals of NS clouds. In sharp contrast, ER events do occur during the N field portions of SN MCs. From the above two results it is reasonable to conclude that the latter ER events represent residual energy remaining from the preceding S portions of the SN MCs. We derive a new solar wind-magnetosphere coupling function during northward IMFs: ENIMF = ? N-1/12 V7/3 B1/2 + ? V |Dstmin|. The first term on the right-hand side of the equation represents the energy input via “viscous interaction,” and the second term indicates the residual energy stored in the magnetotail. It is empirically found that the magnetotail/magnetosphere/ionosphere can store energy for a maximum of ˜4 h before it has dissipated away. This concept is defining one for ER/substorm energy storage. Our scenario indicates that the rate of solar wind energy injection into the magnetotail/magnetosphere/ionosphere for storage determines the potential form of energy release into the magnetosphere/ionosphere. This may be more important to understand solar wind-magnetosphere coupling than the dissipation mechanism itself (in understanding the form of the release). The concept of short-term energy storage is also applied for the solar case. It is argued that it may be necessary to identify the rate of energy input into solar magnetic loop systems to be able to predict the occurrence of solar flares.

Du, A. M.; Tsurutani, B. T.; Sun, W.

2011-12-01

178

Average dimension and magnetic structure of the distant Venus magnetotail  

NASA Astrophysics Data System (ADS)

The authors report the first major statistical investigation of the far wake of an unmagnetized object embedded in the solar wind. The investigation is based on Pioneer Venus Orbiter magnetometer data from 70 crossings of the Venus wake at altitudes between 5 and 11 Venus radii during reasonably steady IMF conditions. The authors find that Venus has a well-developed tail, flaring with altitude and possibly broader in the direction parallel to the IMF cross-flow component. Tail lobe field polarities and the direction of the cross-tail field are consistent with tail accretion from the solar wind. Average values for the cross-tail field (2 nT) and the distant tail flux (3 MWb) indicate that most distant tail field lines close across the center of the tail and are not rooted in the Venus ionosphere. The authors illustrate their findings in a three-dimensional schematic.

Saunders, M. A.; Russell, C. T.

1986-05-01

179

Interplanetary magnetic field By and auroral conductance effects on high-latitude ionospheric convection patterns  

NASA Astrophysics Data System (ADS)

The dependence of the ionospheric electric potential (convection) on the interplanetary magnetic field (IMF) and the ionospheric conductivity is investigated to understand the generation of convection patterns in the framework of the solar wind-magnetosphere-ionosphere (S-M-I) coupling scheme and the merging concept. A numerical magnetohydrodynamic (MHD) simulation is adopted for the study of the present problem. To achieve a high resolution in the ionosphere, the MHD calculation employs the finite volume (FV) total-variation diminishing (TVD) scheme with an unstructured grid system. The two-cell convection patterns reproduced from simulation are shown for several cases under the southward IMF condition during the growth-phase interval. In the investigation of these results, special attention is paid to the analysis of mirror symmetry in the convection patterns with respect to the IMF By. On the dayside in the Northern Hemisphere, IMF By- (By+) generates flow deflection on newly opened field lines toward the dusk (dawn) without a severe violation of the mirror symmetry. While the mirror symmetry of the convection pattern is maintained even on the nightside when the ionospheric conductivity is uniform, it is not maintained on the nightside when the ionospheric conductivity is nonuniform. A realistic ionospheric conductivity modifies the convection pattern in the Northern (Southern) Hemisphere so as to emphasize distinctive features seen for IMF By+ (By-) under a uniform conductivity, and the reproduced convection patterns coincide with the observation quite well including fine signatures on the nightside, both for IMF By- and By+. Because of the nonuniform conductivity, cell centers of convection are shifted to the earlier magnetic local times, and the antisunward flow in the northern polar cap is nearly aligned with noon-midnight meridian for IMF By-, while the flow in the northern polar cap has a significant inclination from prenoon to premidnight for IMF By+. These convection patterns can be understood by considering the effect due to the Hall current closure of the region-1 field-aligned current. The analysis for the dependence of nightside convection on IMF By and ionospheric conductivity shows that the Harang discontinuity is attributed partially to the structure of magnetospheric driver but mainly to the effect of nonuniform auroral conductivity. As a consequence, it is more adequate to say that convection patterns are more or less caused by the synthesized effect of more than one process rather than a single elementary process. Reproduced convection patterns in this paper show a particular coincidence with satellite observations summarized by adopting the pattern-recognition-based approach.

Tanaka, T.

2001-11-01

180

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

NASA Astrophysics Data System (ADS)

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 1 AU: 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, ? 0.6. The SEP events within ICMEs show stronger correlation between the peak proton intensity and the soft X-ray flux of the associated solar flare, with correlation coefficient r=0.67±0.13, compared to the SEP events propagating in the standard solar wind, r=0.36±0.13. The difference is more pronounced for near-relativistic electrons. The main reason for the different correlation behavior seems to be the larger spread of the flare longitude in the SEP sample detected in the solar wind as compared to SEP events within ICMEs. We discuss to what extent observational bias, different physical processes (particle injection, transport, etc.), and the IMF configuration can influence the relationship between SEPs and coronal activity.

Miteva, R.; Klein, K.-L.; Malandraki, O.; Dorrian, G.

2013-02-01

181

Storm sudden commencements at Indian stations and associated changes in interplanetary magnetic field orientation  

NASA Astrophysics Data System (ADS)

Storm sudden commencement (SSC) or sudden impulse (SI) is one of the important aspects of solar terrestrial relationships involving solar wind, IMF, magnetosphere, ionosphere and EEJ. The SSCs observed globally everywhere at ground, the amplitude of each SSC and waveform will different and depends on the latitude and also the local time. The understanding of the SCs in general involves the complex current systems that develop in the magnetosphereionosphere domain as a result of sudden magnetospheric compression. In recent years, the statistical studies showed the local time (LT) pattern of occurrence of preliminary impulse at middle and low latitudes and associated mechanisms of field aligned currents and ionospheric currents. The objective of this work focuses is on the SSCs chacteristics of severe magnetic storms which occurred during solar cycle 23 and associated IMF parameters and solar wind dynamic pressure will be investigated using digital geomagnetic data from Indian sector and also satellite data. This study will also aim to understand the aspects of preliminary impulse and main impulse characteristics at low latitudes from Indian sector and the associated ionospheric current systems which will be the tool to investigate the coupling between magnetosphere and Ionosphere.

Bhaskara, Veenadhari; Alex, S.; Singh, R.

182

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

SciTech Connect

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

Roberts, D.A. (NASA Goddard Space Flight Center, Greenbelt, MD (United States))

1990-02-01

183

Variations in the Spectral Slopes of Interplanetary Data  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

184

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

Microsoft Academic Search

Six-month and yearly averages of solar wind speed from 1962 to 1975 are shown to be highly correlated with geomagnetic activity as measured by averages of the AP index. On the same time scale the correlation between the southward component of the interplanetary magnetic field and geomagnetic activity is poor. Previous studies with hourly averages give opposite results. The better

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

1977-01-01

185

Comparison of magnetic field observations of an average magnetic cloud with a simple force free model: the importance of field compression and expansion  

NASA Astrophysics Data System (ADS)

We investigate the ability of the cylindrically symmetric force-free magnetic cloud (MC) fitting model of Lepping et al. (1990) to faithfully reproduce actual magnetic field observations by examining two quantities: (1) a difference angle, called ?, i.e., the angle between the direction of the observed magnetic field (Bobs) and the derived force free model field (Bmod) and (2) the difference in magnitudes between the observed and modeled fields, i.e., ?B(=|Bobs|-|Bmod|), and a normalized ?B (i.e., ?B/) is also examined, all for a judiciously chosen set of 50 WIND interplanetary MCs, based on quality considerations. These three quantities are developed as a percent of MC duration and averaged over this set of MCs to obtain average profiles. It is found that, although and its normalize version are significantly enhanced (from a broad central average value) early in an average MC (and to a lesser extent also late in the MC), the angle is small (less than 8°) and approximately constant all throughout the MC. The field intensity enhancements are due mainly to interaction of the MC with the surrounding solar wind plasma causing field compression at front and rear. For example, for a typical MC, ?B/ is: 0.21±0.27 very early in the MC, -0.11±0.10 at the center (and -0.085±0.12 averaged over the full "central region," i.e., for 30% to 80% of duration), and 0.05±0.29 very late in the MC, showing a double sign change as we travel from front to center to back, in the MC. When individual MCs are examined we find that over 80% of them possess field enhancements within several to many hours of the front boundary, but only about 30% show such enhancements at their rear portions. The enhancement of the MC's front field is also due to MC expansion, but this is usually a lesser effect compared to compression. It is expected that this compression is manifested as significant distortion to the MC's cross-section from the ideal circle, first suggested by Crooker et al. (1990), into a more elliptical/oval shape, as some global MC studies seem to confirm (e.g., Riley and Crooker, 2004) and apparently also as confirmed for local studies of MCs (e.g., Hidalgo et al., 2002; Nieves-Chinchilla et al., 2005).

Lepping, R. P.; Narock, T. W.; Chen, H.

2007-12-01

186

Magnetic island formation between large-scale flow vortices at an undulating postnoon magnetopause for northward interplanetary magnetic field  

Microsoft Academic Search

Time History of Events and Macroscale Interactions during Substorms multispacecraft observations are presented for a ?2-h-long postnoon magnetopause event on 8 June 2007 that for the first time indicate that the trailing (sunward) edges of Kelvin-Helmholtz (KH) waves are commonly related to small-scale <0.56 RE magnetic islands or flux transfer events (FTE) during the growth phase of these surface waves.

S. Eriksson; H. Hasegawa; W.-L. Teh; B. U. Ö. Sonnerup; J. P. McFadden; K.-H. Glassmeier; O. Le Contel; V. Angelopoulos; C. M. Cully; D. E. Larson; R. E. Ergun; A. Roux; C. W. Carlson

2009-01-01

187

Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars  

Microsoft Academic Search

This paper presents the catalogue and the method of determination of averaged quadratic effective magnetic fields for 596 main sequence and giant stars. The catalogue is based on measurements of the stellar effective (or mean longitudinal) magnetic field strengths B_e, which were compiled from the existing literature. We analysed the properties of 352 chemically peculiar A and B stars in

V. D. Bychkov; L. V. Bychkova; J. Madej

2003-01-01

188

Local and nonlocal geometry of interplanetary coronal mass ejections: Galactic cosmic ray (GCR) short-period variations and magnetic field modeling  

NASA Astrophysics Data System (ADS)

Energetic galactic cosmic ray (GCR) particles, arriving within the solar system, are modulated by the overall interplanetary field carried in the solar wind. Localized disturbances related to solar activity cause further reduction in intensity, the largest being Forbush decreases in which fluxes can fall ˜20% over a few days. Understanding Forbush decreases leads to a better understanding of the magnetic field structure related to shock waves and fast streams originating at the Sun since the propagation characteristics of the GCR probe much larger regions of space than do individual spacecraft instruments. We examined the temporal history of the integral GCR fluence (?100 MeV) measured by the high-sensitivity telescope (HIST) aboard the Polar spacecraft, along with the solar wind magnetic field and plasma data from the ACE spacecraft during a 40-day period encompassing the 25 September 1998 Forbush decrease. We also examined the Forbush and (energetic storm particles) ESP event on 28 October 2003. It is the use of HIST in a high-counting-rate integral mode that allows previously poorly seen, short-scale depressions in the GCR fluxes to be observed, adding crucial information on the origin of GCR modulation. Variability on time scales within the frequency range 0.001-1.0 mHz is detected. This paper concentrates on investigating four simple models for explaining short-term reductions in the GCR intensity of both small and large amplitude. Specifically, these models are a local increase in magnetic scattering power, the passage of a shock discontinuity, and the passage of a tangential discontinuity or magnetic rope in the solar wind plasma. Analysis of the short-scale GCR depressions during a test period in September through October 1998 shows that they are not correlated with changes in magnetic scattering power or fluctuations in solar wind speed or plasma density. However, magnetic field and plasma data during the test period of Forbush decrease strongly suggest the presence of an interplanetary coronal mass ejection (ICME). Use of a non-force-free magnetic rope model in conjunction with the energetic particle data allows modeling of the geometry of the ICME in terms of a magnetic cloud topology. It is only this cloud configuration that allows a satisfactory explanation of the magnitude of the Forbush event of 25 September 1998. Calculations made during the test period point to short-scale GCR depressions being caused by either small-scale magnetic flux rope structures or possibly tangential discontinuities in the solar wind.

Quenby, J. J.; Mulligan, T.; Blake, J. B.; Mazur, J. E.; Shaul, D.

2008-10-01

189

Intense geomagnetic storm signatures at low-latitudes in response to varying solar wind-interplanetary magnetic field conditions and associated energetics  

NASA Astrophysics Data System (ADS)

Geomagnetic storms are large scale manifestations of the various complex physical processes occurring in the Earth's magnetosphere which are instigated by highly changing solar wind and interplanetary magnetic field (IMF) conditions. Primary trigger for geomagnetic field distur-bances characterizing the magnetic storms is the transfer of tremendous energy and momentum carried by the solar wind into the Earth's magnetosphere. The southward directed meridional component (Bz) of IMF assists in efficient transport of energy through the magnetic reconnec-tion process. The total energy loaded in the magnetosphere is redistributed in different regions therein. During several phases of geomagnetic storm, the storage, consumption and dissipation of energy contained in the magnetospheric regions influence the major magnetospheric cur-rent systems substantially. In this paper, we investigate the contributions of different currents towards storm development and intensification in response to energy budget. Intense geomag-netic storm signatures at low-latitudes in Indian subcontinent are discussed emphasizing on the energetics. High resolution digital magnetic data from low-latitude station is utilized in conjunction with satellite data to delineate the characteristics of diverse storm patterns.

Rawat, Rashmi; Alex, Sobhana; Lakhina, Gurbax S.

190

A Quasi-Linear Kinetic Equation for Cosmic Rays in the Interplanetary Medium.  

National Technical Information Service (NTIS)

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 inste...

J. G. Luhmann

1976-01-01

191

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

NASA Astrophysics Data System (ADS)

Here we present a method to forecast the arrival of an interplanetary shock to the Earth's orbit in advance of up to one day, using cosmic ray fluctuations and solar wind parameters measured onboard the ACE spacecraft. The method is based on our previous results [1]. By means of continuous monitoring of the interplanetary space state since April 2010, we conclude that not all shocks can be reliably forecasted by the method. Only those interplanetary shocks, for which a large flux of low-energy particles (10 keV - 10 MeV) of solar or interplanetary origin exists in the upstream region, can be forecasted. This is typically related to quasi-parallel shocks. In the absence of such particles, a forecast cannot be made. This is a typical situation for quasi-perpendicular shocks. Our analysis shows that, on average, an interplanetary shock can be forecasted for several hours up to one day, with the probability about 70%.

Starodubtsev, S. A.; Grigoryev, V. G.; Usoskin, I. G.

2013-02-01

192

The role of the Y-component of the interplanetary magnetic field in transpolar saturation and ring current response as found in data and simulation  

NASA Astrophysics Data System (ADS)

Energy is transferred into the magnetosphere of Earth through merging of magnetic fields (Dungey cycle and lobe cell convection) and through momentum transfer across the magnetopause (viscous interactions). These processes cause enhanced plasma convection in the inner magnetosphere and ionosphere, which in turn form the ring current and the transpolar potential, respectively. These processes have been studied extensively with regard to the role of the north-south component of the interplanetary magnetic field (IMF). The role of the dawn-dusk IMF is less well known. We use the LFM global MHD simulation, the CRCM, and data to quantify the transpolar potential and ring current responses to the dawn-dusk IMF (B y). As with the north-south IMF (Bz), we find the transpolar potential saturates for large values of B y. Furthermore, the transpolar potential saturates at approximately the same magnitude of the magnetic field, but with a much smaller transpolar potential value. This suggests the saturation of the transpolar potential depends on the balance of the forces in the magnetosheath rather than the region 1 current. Unlike with Bz, we find the ring current does not respond to changes in By. This indicates a decoupling of the plasma convection in the ionosphere from convection in the inner magnetosphere. We discuss the implications of these results for space physics.

Mitchell, Elizabeth Joy

193

Interplanetary Disturbances and Space Weather  

NASA Astrophysics Data System (ADS)

Interplanetary disturbances associated with solar flares, coronal mass ejections (CMEs), and solar wind streams (co-rotating interaction regions, CIRs) are responsible for a significant fraction of the space weather effects occurring in the near-Earth environment. This talk reviews the radial evolution of the solar wind transients in the inner heliosphere, based on interplanetary scintillation (IPS) images obtained from the Ooty Radio Telescope, combined with a wealth of data acquired from space missions, such as SDO, SOHO and STEREO. Results show that the interaction between the interplanetary disturbance (CME or CIR) and the background solar wind determines the radial evolution of its speed and size. Further, the magnetic energy associated with the propagating transient (the magnetic cloud in the case of a CME and the high-speed stream for a CIR) is likely to play a crucial role in determining the effectiveness of the compression and propagation characteristics of the disturbance. These results are useful to quantify the drag force imposed on a disturbance by the interaction with the ambient solar wind and it is essential in modeling the propagation of a disturbance. This study also has a great importance in understanding the prediction of CME/CIR-associated space weather at the near-Earth environment.

Manoharan, P. K.

2012-07-01

194

Solar wind plasma profiles during interplanetary field enhancements (IFEs): Consistent with charged-dust pickup  

NASA Astrophysics Data System (ADS)

The solar wind contains many magnetic structures, and most of them have identifiable correlated changes in the flowing plasma. However, the very characteristic rise and fall of the magnetic field in an interplanetary field enhancement has no clear solar wind counterpart. It appears to be a pure magnetic ``barrier'' that transfers solar wind momentum to charged dust produced in collisions of interplanetary bodies in the size range of tens to hundreds of meters. This transfer lifts the fine scale dust out of the Sun's gravitational well. We demonstrate the lack of field-plasma correlation with several examples from spacecraft records as well as show an ensemble average velocity profile during IFEs which is consistent with our IFE formation hypothesis.

Lai, H. R.; Wei, H. Y.; Russell, C. T.

2013-06-01

195

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

SciTech Connect

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

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

1984-08-20

196

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

Microsoft Academic Search

It is well known that intense southward magnetic field and convection electric field (V × B) in the interplanetary medium are key parameters that control the magnitude of geomagnetic storms. By investigating the interplanetary conditions of 82 intense geomagnetic storms from 1998 to 2006, we have compared many different criteria of interplanetary conditions for the occurrence of the intense geomagnetic

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

2010-01-01

197

A numerical simulation of charged particle interactions with interplanetary shock waves  

Microsoft Academic Search

A computer model, developed to numerically simulate the combined effects of a charged particle's energization at an interplanetary shock and propagation to a satellite-borne particle detector at the obsevation point, is described and the trajectory results examined. A charged particle's adiabatic motion is assumed to be scatter-free along the laminar spiral interplanetary magnetic field (IMF). The interplanetary shock wave is

R. B. Decker

1979-01-01

198

An improved method of inferring interplanetary sector structure, 1905-present  

Microsoft Academic Search

A new method of estimating interplanetary sector polarity from geomagnetic activity is presented. The method is based on a linear multiregression between the By component of the interplanetary magnetic field and hourly values of the magnetic perturbation (DeltaX,DeltaY,DeltaZ) at selected magnetic observatories. By simultaneous use of all three components, and by using all hours of local time, the method yields

S. Vennerstroem; B. Zieger; E. Friis-Christensen

2001-01-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

200

Statistical averaging of marine magnetic anomalies and the aging of oceanic crust.  

USGS Publications Warehouse

Visual comparison of Mesozoic and Cenozoic magnetic anomalies in the North Pacific suggests that older anomalies contain less short-wavelength information than younger anomalies in this area. To test this observation, magnetic profiles from the North Pacific are examined from crust of three ages: 0-2.1, 29.3-33.1, and 64.9-70.3Ma. For each time period, at least nine profiles were analyzed by 1) calculating the power density spectrum of each profile, 2) averaging the spectra together, and 3) computing a 'recording filter' for each time period by assuming a hypothetical seafloor model. The model assumes that the top of the source is acoustic basement, the source thickness is 0.5km, and the time scale of geomagnetic reversals is according to Ness et al. (1980). The calculated power density spectra of the three recording filters are complex in shape but show an increase of attenuation of short-wavelength information as the crust ages. These results are interpreted using a multilayer model for marine magnetic anomalies in which the upper layer, corresponding to pillow basalt of seismic layer 2A, acts as a source of noise to the magnetic anomalies. As the ocean crust ages, this noisy contribution by the pillow basalts becomes less significant to the anomalies. Consequently, magnetic sources below layer 2A must be faithful recorders of geomagnetic reversals.-AuthorPacific power density spectrum

Blakely, R. J.

1983-01-01

201

High-speed solar wind with southward interplanetary magnetic field causes relativistic electron flux enhancement of the outer radiation belt via enhanced condition of whistler waves  

NASA Astrophysics Data System (ADS)

Relativistic electron flux in the outer radiation belt tends to increase during the high-speed solar wind stream (HSS) events. However, HSS events do not always cause large flux enhancement. To determine the HSS events that cause such enhancement and the mechanisms that are responsible for accelerating the electrons, we analyzed long-term plasma data sets, for periods longer than one solar cycle. We demonstrate that during HSS events with the southward interplanetary magnetic field (IMF)-dominant HSS (SBz-HSS), relativistic electrons are accelerated by whistler mode waves; however, during HSS events with the northward IMF-dominant HSS, this acceleration mechanism is not effective. The differences in the responses of the outer radiation belt flux variations are caused by the differences in the whistler mode wave-electron interactions associated with a series of substorms. During SBz-HSS events, hot electron injections occur and the thermal plasma density decreases due to the shrinkage of the plasmapause, causing large flux enhancement of relativistic electrons through whistler mode wave excitation. These results explain why large flux enhancement of relativistic electrons tends to occur during SBz-HSS events.

Miyoshi, Y.; Kataoka, R.; Kasahara, Y.; Kumamoto, A.; Nagai, T.; Thomsen, M. F.

2013-09-01

202

Statistical study of interplanetary condition effect on geomagnetic storms  

NASA Astrophysics Data System (ADS)

Based on the archive OMNI data for the period 1976-2000 an analysis has been made of 798 geomagnetic storms with D st < -50 nT and their interplanetary sources-large-scale types of the solar wind: CIR (145 magnetic storms), Sheath (96), magnetic clouds MC (62), and Ejecta (161). The remaining 334 magnetic storms have no well-defined sources. For the analysis, we applied the double method of superposed epoch analysis in which the instants of the magnetic storm beginning and minimum of D st index are taken as reference times. The well-known fact that, independent of the interplanetary source type, the magnetic storm begins in 1-2 h after a southward turn of the IMF ( B z < 0) and both the end of the main phase of a storm and the beginning of its recovery phase are observed in 1-2 h after disappearance of the southward component of the IMF is confirmed. Also confirmed is the result obtained previously that the most efficient generation of magnetic storms is observed for Sheath before MC. On the average parameters B z and E y slightly vary between the beginning and end of the main phase of storms (minimum of D st and D {/st *} indices), while D st and D {/st *} indices decrease monotonically proportionally to integral of B z and E y over time. Such a behavior of the indices indicates that the used double method of superposed epoch analysis can be successfully applied in order to study dynamics of the parameters on the main phase of magnetic storms having different duration.

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

2010-12-01

203

The response of the magnetic field in the geosynchronous orbit to the interplanetary solar wind dynamic pressure pulses  

Microsoft Academic Search

Solar wind dynamic pressure DP is one of the main factors which affect magnetosphere There are three categories of the DP changes increases decreases pulses increases and then decreases and here we investgate the response of geosynchronous magnetic field to DP pulses since their figures can be clearly and evidently identified Among the more than 600 dynamic pressure pulses observed

J. B. Liu; C. Wang; Z. H. Huang

2006-01-01

204

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

SciTech Connect

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

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

1992-12-01

205

Intense geomagnetic storms and causative interplanetary conditions  

NASA Astrophysics Data System (ADS)

Active sun is characterized by large and powerful emissions triggered by the twisting and shearing of solar magnetic field lines Orientation of the coronal ejecta and the structure and direction of interplanetary parameters play a dominant role in the formulation and development of intense geomagnetic storms Digital magnetic observations at low latitude locations are worth considering for understanding and interpreting the varied dynamics of intense geomagnetic storms Variations in the Horizontal and Declination components of geomagnetic field that are attributed to the varying interplanetary conditions are discussed for a set of intense storm events occurred in the current solar cycle Differing response of geomagnetic field to the interplanetary shocks driven by fast halo coronal mass ejections fast solar wind streams from the coronal hole regions and the dynamic pressure pulses associated with these mechanisms will be projected Contribution from the solar wind plasma and interplanetary magnetic field for these events are discussed in relation to the quantum of energy transfer from the solar wind into the earth s magnetosphere

Rawat, R.; Alex, S.; Lakhina, G. S.

206

Enhanced high-altitude polar cap plasma and magnetic field values in response to the interplanetary magnetic cloud that caused the great storm of 31 March 2001: A case study for a new magnetospheric index  

NASA Astrophysics Data System (ADS)

The magnetospheric electron number density and the magnetic field strength near 8 RE over the polar cap increased dramatically after the arrival of an interplanetary magnetic cloud on 31 March 2001. These parameters were determined with high accuracy from the plasma resonances stimulated by the Radio Plasma Imager (RPI) on Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) near apogee during both quiet (30 March 2001) and disturbed (31 March 2001) days. The quiet day and disturbed day values were each compared with magnetospheric magnetic field and electron density models; good agreement was found with the former but not the latter. The magnetospheric response was also expressed in terms of the ratio of the electron plasma frequency fpe to the electron cyclotron frequency fce, which is proportional to the ratio of the electron gyroradius to the Debye radius. Simultaneous Wind measurements of the solar wind magnetic field strength, speed, and plasma density were used to calculate the solar wind quasi-invariant QI. This index is equivalent to the ratio of the solar wind magnetic pressure to the solar wind ram pressure or to the inverse of the magnetic Mach number squared. These nondimensional quantities, QI and fpe/fce, have fundamental meanings in the solar wind MHD regime and in the relation between electric and magnetic forces on electrons in the magnetosphere, respectively. During the large 31 March 2001 storm, IMAGE was at the right place at the right time so as to enable comparisons between RPI fpe/fce and Wind QI determinations. Both QI and fpe/fce formed maxima during 6-hour observing intervals during this storm that were found to be highly correlated (87%) with a magnetospheric time lag of about 3 hours for fpe/fce. These results, based on a detailed case study of this important event, suggest that the plasma parameter fpe/fce may serve as a useful magnetospheric index.

Osherovich, Vladimir A.; Benson, Robert F.; Fainberg, Joseph; Green, James L.; Garcia, Leonard; Boardsen, Scott; Tsyganenko, Nikolai; Reinisch, Bodo W.

2007-06-01

207

High Amplitude Events in relation to Interplanetary disturbances  

NASA Astrophysics Data System (ADS)

The Sun emits the variable solar wind which interacts with the very local interstellar medium to form the heliosphere. Hence variations in solar activity strongly influence interplanetary space, from the Sun's surface out to the edge of the heliosphere. Superimposed on the solar wind are mass ejections from the Sun and/or its corona which, disturb the interplanetary medium - hence the name "interplanetary disturbances". Interplanetary disturbances are the sources of large-scale particle acceleration, of disturbances in the Earth's magnetosphere, of modulations of galactic cosmic rays in short, they are the prime focus for space weather studies. The investigation deals with the study of cosmic ray intensity, solar wind plasma and interplanetary magnetic field parameters variation due to interplanetary disturbances (magnetic clouds) during an unusual class of days i.e. high amplitude anisotropic wave train events. The high amplitude anisotropic wave train events in cosmic ray intensity has been identified using the data of ground based Goose Bay neutron monitor and studied during the period 1981-94. Even though, the occurrence of high amplitude anisotropic wave trains does not depend on the onset of interplanetary magnetic clouds. But the possibility of occurrence of these events cannot be overlooked during the periods of interplanetary magnetic cloud events. It is observed that solar wind velocity remains higher (> 300) than normal and interplanetary magnetic field B remains lower than normal on the onset of interplanetary magnetic cloud during the passage of these events. It is also noted from the superposed epoch analysis of cosmic ray intensity and geomagnetic activity for high amplitude anisotropic wave train events during the onset of interplanetary magnetic clouds that the increase in cosmic ray intensity and decrease in geomagnetic activity start not at the onset of magnetic clouds but after few days. The north south component of IMF (Bz), IMF (B), proton density (N), proton temperature (T) and latitude angle reaches to their maximum, whereas solar wind velocity (V) and longitude angle reaches to their minimum on the day of magnetic cloud event during the passage of high amplitude anisotropic wave trains. The cosmic ray intensity and Dst index both are found to decrease with the increase of solar wind velocity and reaches to their minimum on the days of high-speed solar wind streams during HAEs.

Mishra, Rajesh Kumar; Agarwal Mishra, Rekha

2012-07-01

208

Influence of interplanetary solar wind sector polarity on the ionosphere  

NASA Astrophysics Data System (ADS)

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

Liu, Jing; Liu, Libo; Zhao, Biqiang; Wan, Weixing

2012-08-01

209

Pitch angle distributions of solar energetic particles and the local scattering properties of the interplanetary magnetic field  

NASA Astrophysics Data System (ADS)

An approximate solution of the Fokker-Planck equation containing pitch angle scattering and adiabatic focusing is discussed. For modest focusing effects the omnidirectional density obeys an ordinary diffusion equation with a modified diffusion coefficient. The anisotropic part of the distribution function is properly normalized and split into an even and an odd part. The even part is determined by the ratio between the scattering mean free path and the focusing length and by the degree of polarization of the magnetic field fluctuations. The odd part is determined by the deviation of the pitch angle scattering from isotropic scattering. The method supplies a powerful tool to obtain the local characteristics of pitch angle scattering. It is insensitive to long lasting solar injections and to moderate radial variations of the mean free path. The method is applied to solar particle events observed on Helio-1 and -2.

Beeck, J.; Wibberenz, G.

1985-08-01

210

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

211

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  

SciTech Connect

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 ({approximately}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 B{sub y} component of the IMF was positive, reasonably steady, and approximately twice the magnitude of B{sub z}. 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 B{sub y} as presented by Heppner and Maynard. At {approx} 1840 UT, a decrease in B{sub y} in association with an increase in B{sub z}, led to an extended period with B{sub y}{approx}B{sub z}. During this second interval the convection patterns were highly variable and even chaotic. Finally, a sharp decrease in the B{sub y} component at 1914 UT, probably in association with a rotational discontinuity in the solar wind, led to an extended period with B{sub y}<

Greenwald, R.A.; Bristow, W.A. [Johns Hopkins Univ., Laurel, MD (United States); Szabo, A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)] [and others

1995-10-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

213

Geomagnetic effects of high-density plasma with southward magnetic field in the interplanetary coronal mass ejection observed on May 2-3, 1998  

Microsoft Academic Search

This paper aims to clarify the effect of high-density plasma in interplanetary coronal mass ejection (ICME) observed during the May 2-3, 1998 geomagnetic storm. The examination is performed based on the estimation of Dst index, which is calculated with the observed solar wind parameters of the ICME. The estimated Dst index variation is compared with Dst index variation provided by

Haruka Adachi; Tohru Sakurai; Katsuhide Marubashi

2006-01-01

214

The Relation of Variations in Total Magnetic Field at High Latitude with the Parameters of the Interplanetary Magnetic Field and with DP2 Fluctuations.  

National Technical Information Service (NTIS)

The maximum disturbances from the positive and negative regions of delta B (Bp and Bn, respectively) are investigated with respect to their correlation with (1) the average N-S component, Bz, (2) the average angle with respect to the solar magnetospheric ...

R. A. Langel

1974-01-01

215

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

216

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

217

Ion dynamics in the near-Earth magnetotail: Magnetic turbulence versus normal component of the average magnetic field  

Microsoft Academic Search

The influence on ion motion of magnetic turbulence observed in the near-Earth magnetotail is investigated by numerical simulation. The magnetotail current sheet is modeled as a magnetic field reversal with a normal magnetic field component Bn, plus a three-dimensional spectrum of magnetic fluctuations ?B, which represents the observed magnetic turbulence. A cross tail electric field Ey is included. A test

A. Greco; A. L. Taktakishvili; G. Zimbardo; P. Veltri; L. M. Zelenyi

2002-01-01

218

Cosmic ray modulation by interplanetary disturbances  

NASA Astrophysics Data System (ADS)

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

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

219

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

220

Ion dynamics in the near-Earth magnetotail: Magnetic turbulence versus normal component of the average magnetic field  

Microsoft Academic Search

The influence on ion motion of magnetic turbulence observed in the near-Earth magnetotail is investigated by numerical simulation. The magnetotail current sheet is modeled as a magnetic field reversal with a normal magnetic field component Bn, plus a three-dimensional spectrum of magnetic fluctuations deltaB, which represents the observed magnetic turbulence. A cross tail electric field Ey is included. A test

A. Greco; A. L. Taktakishvili; G. Zimbardo; P. Veltri; L. M. Zelenyi

2002-01-01

221

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

PubMed

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

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

2003-04-01

222

Geomagnetic storm characteristics under varied interplanetary conditions  

NASA Astrophysics Data System (ADS)

Solar cycle-23 witnessed many successive intense X-ray solar flares and coronal mass ejections (CME) during the peak activity period, as well as in the descending phase of the cycle. Some of these emissions had large solar energetic particle events associated with them. When such solar ejecta impact the Earth's magnetosphere, they cause large scale disturbances in the geomagnetic field known as geomagnetic storms. Large variability in the occurrence characteristics of geomagnetic storms is controlled ultimately by the solar activity. Thus the changes in the interplanetary conditions are distinctly seen in the low latitude geomagnetic records as each storm event differs from the other. Several intense storm events of solar cycle-23 are analyzed for assessing the role of interplanetary magnetic field components B_{y} (east-west) and B_{z} (north-south) in controlling the generation and development of various types of storms.

Rawat, R.; Alex, S.; Lakhina, G. S.

2007-12-01

223

Interplanetary Meteoroids Near Earh and Moon  

NASA Astrophysics Data System (ADS)

Several models for the sporadicmeteoroid background have been developed over the last two decades. These include, among others, the Divine, the Staubach and the Dikarev model. They cover mass ranges from 10-18 g to 1 g typically and are applicable for model-specific heliocentric distance ranges between 0.1 and 20 AU. At 1 AU from the Sun in the ecliptic plane, averaged fluxes (over directions and velocities) are tuned to the well established interplanetary model by Grün et al. (1985). However, in many respects thesemodels differ considerably, and our comparison of flux predictions near Earth from existing models shows a clear need for additional measurements and simulations in order to derive a reliable model for the population of interplanetary and interstellar meteoroids.

Dikarev, V.; Drolshagen, G.; Landgraf, M.; Krag, H.; Kuiper, W.; Grün, E.

2008-09-01

224

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

225

Neutral hydrogen in interplanetary space  

Microsoft Academic Search

The theory and observations relevant to the problem of neutral hydrogen in interplanetary space are reviewed. Emphasis is placed on those theoretical problems whose treatment in the existing literature is not entirely satisfactory, but discussion of all significant observational and theoretical aspects of the interplanetary H problem is provided. Attention is also given to other neutral constituents (particularly He) that

Thomas E. Holzer

1977-01-01

226

Liquid chromatography/proton nuclear magnetic resonance spectrometry average composition analysis of fuels  

SciTech Connect

The use of a NMR spectrometer as a continuous flow liquid chromatographic detector (LC//sup 1/H NMR) generates a proton spectrum of each hydrocarbon class present in the sample. A detailed set of equations is presented which permits LC//sup 1/H NMR integration data from petroleum fuels to be interpreted as an average composition for each chromatographic fraction. Quantities calculated for each aromatic fraction include: the number average molecular weight, average degree of substitution on aromatic rings, the absolute number of moles of each structural type of carbon, an average structure (devoid of stereoisomer information), the total number of moles of carbon in each chromatographic fraction, and numerous other properties of interest in fuel characterization. The method is demonstrated for artifical fuels of known composition, for two experimental aviation fuels, and for a fuel blending stock sample which had been fully characterized at an independent laboratory by gas chromatography and GC/MS. The LC//sup 1/H NMR average composition method is shown to be very accurate for the monocyclic aromatic (substituted benzenes and tetralins) and dicyclic aromatic (substituted naphthalenes and acenaphthenes) fractions of petroleum fuels. Average molecular weights for these fractions can be routinely determined at an accuracy of +/-4 daltons. The other quantities are also determined at a high degree of accuracy. The applicability of the LC//sup 1/H NMR method to the aliphatic fraction of fuel samples is restricted by difficulties in accounting for quaternary carbons and cycloalkanes.

Haw, J.F.; Glass, T.E.; Dorn, H.C.

1983-01-01

227

Non-Abelian magnetic monopole dominance for SU(3) Wilson loop average  

SciTech Connect

We show that the non-Abelian magnetic monopole defined in a gauge-invariant way in SU(3) Yang-Mills theory gives a dominant contribution to confinement of the fundamental quark, in sharp contrast to the SU(2) case.

Kondo, Kei-Ichi; Shinohara, Toru [Department of Physics, Graduate School of Science, Chiba University, Chiba 263-8522 (Japan); Shibata, Akihiro [Computing Research Center, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan); Kato, Seikou [Fukui National College of Technology, Sabae 916-8507 (Japan)

2011-05-23

228

Solar cycle effects in near-Earth interplanetary parameters and geomagnetic activity  

NASA Astrophysics Data System (ADS)

Solar cycle effects are investigated in planetary geomagnetic activity from 27-day averages of several near-Earth OMNI parameters compared with equivalent Kp and Dst index averages for almost four decades (1964-2001). Some established trends in these parameters over solar cycles are confirmed; for example, it is concluded that changes in the magnitude (rather than in direction) constitute the primary solar cycle variation in the IMF. The solar cycle effects are also thoroughly studied from the northern polar cap magnetic activity index PCN (1975-2001), which is considered as an ``ionospheric gauge'' of the ``merging'' interplanetary electric field constantly applied to the geomagnetosphere; these results are compared with available studies of solar cycle effects in the auroral magnetic activity indices AL and AU. It is concluded that the 11-year solar activity cycle is clearly seen in all above-mentioned parameters and indices; however, the available time series are not long enough to confirm firmly the existing hypothesis of the increasing geomagnetic activity during last century. Our study also reveals that long-term changes in planetary geomagnetic activity are driven more actively by solar wind-magnetosphere coupling of an electrodynamic nature rather than by plasma transport into the magnetosphere. This suggests that ambient interplanetary ``electric'' environment (in which the Earth's magnetosphere is immersed over the solar cycles) may play a more significant role in causing changes in the frequency of geomagnetic storms and substorms than previously realized.

Papitashvili, V. O.; Papitashvili, N. E.; King, J. H.; Rasmussen, O.; Gromova, L. I.

2001-05-01

229

Solar Wind, Interplanetary Magnetic Field, and Geodipole Tilt Control of Central Plasma Sheet Parameters and Magnetotail Geometry as Derived From Geotail's LEP and MGF Data.  

NASA Astrophysics Data System (ADS)

Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and IMF parameters, in the range of distances between 10 and 50 RE. Another result of this effort is a new quantitative model, representing as a~function of the dipole tilt angle the shape of the cross-tail current sheet and its response to varying solar wind and IMF conditions. The models are based on a~large set of data of the Low-Energy Particle (LEP) and Magnetic Field (MGF) instruments, taken by Geotail spacecraft in 1994-1998 and used in the form of 1-min average values of the CPS parameters and magnetic field components. The concurrent solar wind and IMF data were provided by Wind and IMP~8 spacecraft. The overall quality of the modeling was characterized by the correlation coefficient (c.c.) R between the observed and predicted values of a parameter. The CPS ion density N, controlled mostly by the solar wind proton density and by the northward IMF component, is the most unstable characteristic of the CPS, yielding the lowest c.c., RN=0.57. The CPS temperature T, controlled mainly by the solar wind speed V and the IMF Bz, yielded a higher c.c., RT=0.71. The CPS ion pressure P was found to be most effectively controlled by the solar wind ram pressure Psw and by an IMF-related parameter composed of the perpendicular IMF component Bperpendicular to and the sine of half clock angle ? /2. In a striking contrast with N and T, the model pressure P revealed a~very high c.c. with the data, RP=0.95, manifesting approximate force balance in the CPS due to its confinement by the external tail lobe magnetic field. The modeling revealed very little dawn-dusk asymmetry of the CPS beyond 10 RE, consistent with the observed symmetry of the tail lobe magnetic field. The plasma ion density N is the lowest at midnight and grows towards the tail's flanks. Larger/smaller solar wind ion densities and northward/southward IMF Bz result in larger/smaller N in the CPS. In contrast to the density N, the temperature T peaks at the midnight meridian and falls off towards the CPS flanks (so that the dawn-dusk variation of their product, the CPS pressure, is much smaller). Faster/slower solar wind and southward/northward IMF Bz result in a~hotter/cooler CPS. The CPS ion pressure P is nearly constant across the midtail (20-50RE); at closer distances the isobars gradually bend and approximately follow the contours of constant geomagnetic field in the equatorial plane. For northward IMF conditions combined with a~slow solar wind, this transition occurs at much larger distances, reflecting a weaker tail current and hence more dipole-like magnetic field. Geodipole tilt and solar wind effects on the shape of the cross-tail current sheet have been modeled in the range of distances 10-50 RE, using the magnetic field data from the entire near-tail phase of the Geotail operation.

Tsyganenko, N. A.

2002-12-01

230

Control of interplanetary solar wind sector polarity on changes in the ionosphere  

NASA Astrophysics Data System (ADS)

Solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability. In this study, a solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances and ionospheric perturbations has been demonstrated. Superposed epoch analysis confirms that the increases in interplanetary solar wind speed within three days after SB crossings and the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings. 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. For the same solar sector polarity there are opposite IMF Bz components between March and September equinox, and between June and December solstice. The F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998-2011 are utilized to extract how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings. foF2 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. In September equinox, relative variations of foF2 at noon are depressed at high latitudes and enhanced in low-equatorial latitudes during IMF away sectors. This research was supported by Chinese Academy of Sciences (KZZD-EW-01-3), National Key Basic Research Program of China (2012CB825604) and National Natural Science Foundation of China (41231065).

Liu, Libo; Liu, Jing; Zhao, Biqiang; Wan, Weixing

2013-04-01

231

Volatiles in Interplanetary Dust Particles.  

National Technical Information Service (NTIS)

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 ...

R. Bustin

1991-01-01

232

Average relaxation time of internal spectrum for carbosilane dendrimers: Nuclear magnetic resonance studies  

NASA Astrophysics Data System (ADS)

A new theoretical description of the interior mobility of carbosilane dendrimers has been tested. Experiments were conducted using measurements of the 1H NMR spin-lattice relaxation time, T1H, of two-, three- and four-generation carbosilane dendrimers with three different types of terminal groups in dilute chloroform solutions. Temperature dependences of the NMR relaxation rate, 1/T1H, were obtained for the internal CH2 - groups of the dendrimers in the range of 1/T1H maximum, allowing us to directly evaluate the average time of the internal spectrum for each dendrimer. It was found that the temperature of 1/T1H maximum is practically independent of the number of generations, G; therefore, the theoretical prediction was confirmed experimentally. In addition, the average time of the internal spectrum of carbosilane dendrimers was found to be near 0.2 ns at room temperature, and this value correlates well with the values previously obtained for other dendrimer structures using other experimental techniques.

Markelov, Denis A.; Matveev, Vladimir V.; Ingman, Petri; Lähderanta, Erkki; Boiko, Natalia I.

2011-09-01

233

Average relaxation time of internal spectrum for carbosilane dendrimers: nuclear magnetic resonance studies.  

PubMed

A new theoretical description of the interior mobility of carbosilane dendrimers has been tested. Experiments were conducted using measurements of the (1)H NMR spin-lattice relaxation time, T(1H), of two-, three- and four-generation carbosilane dendrimers with three different types of terminal groups in dilute chloroform solutions. Temperature dependences of the NMR relaxation rate, 1/T(1H), were obtained for the internal CH(2)-groups of the dendrimers in the range of 1/T(1H) maximum, allowing us to directly evaluate the average time of the internal spectrum for each dendrimer. It was found that the temperature of 1/T(1H) maximum is practically independent of the number of generations, G; therefore, the theoretical prediction was confirmed experimentally. In addition, the average time of the internal spectrum of carbosilane dendrimers was found to be near 0.2 ns at room temperature, and this value correlates well with the values previously obtained for other dendrimer structures using other experimental techniques. PMID:21974558

Markelov, Denis A; Matveev, Vladimir V; Ingman, Petri; Lähderanta, Erkki; Boiko, Natalia I

2011-09-28

234

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

235

Autonomous interplanetary constellation design  

NASA Astrophysics Data System (ADS)

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

Chow, Cornelius Channing, II

236

Interplanetary origins of moderate (-100 nT < Dst ? -50 nT) geomagnetic storms during solar cycle 23 (1996-2008)  

NASA Astrophysics Data System (ADS)

The interplanetary causes of 213 moderate-intensity (-100 nT < peak Dst ? -50 nT) geomagnetic storms that occurred in solar cycle 23 (1996-2008) are identified. Interplanetary drivers such as corotating interaction regions (CIRs), pure high-speed streams (HSSs), interplanetary coronal mass ejections (ICMEs) of two types [those with magnetic clouds (MCs) and those without (nonmagnetic cloud or ICME_nc)], sheaths (compressed and/or draped sheath fields), as well as their combined occurrence were identified as causes of the storms. The annual rate of occurrence of moderate storms had two peaks, one near solar maximum and the other in the descending phase, around 3 years later. The highest rate of moderate storm occurrence was found in the declining phase (25 storms year-1). The lowest occurrence rate was 5.7 storms year-1 and occurred at solar minimum. All moderate-intensity storms were associated with southward interplanetary magnetic fields, indicating that magnetic reconnection was the main mechanism for solar wind energy transfer to the magnetosphere. Most of these storms were associated with CIRs and pure HSSs (47.9%), followed by MCs and noncloud ICMEs (20.6%), pure sheath fields (10.8%), and sheath and ICME combined occurrence (9.9%). In terms of solar cycle dependence, CIRs and HSSs are the dominant drivers in the declining phase and at solar minimum. CIRs and HSSs combined have about the same level of importance as ICMEs plus their sheaths in the rising and maximum solar cycle phases. Thus, CIRs and HSSs are the main driver of moderate storms throughout a solar cycle but with variable contributions from ICMEs, their shocks (sheaths), and combined occurrence within the solar cycle. This result is significantly different than that for intense (Dst ? -100 nT) and superintense (Dst ? -250 nT) magnetic storms shown in previous studies. For superintense geomagnetic storms, 100% of the events were due to ICME events, while for intense storms, ICMEs, sheaths, and their combination caused almost 80% of the storms. CIRs caused only 13% of the intense storms. The typical interplanetary electric field (Ey) criteria for moderate magnetic storms were identified. It was found that ~80.1% of the storms follow the criterion of Ey ? 2 mV m-1 for intervals longer than 2 h. It is concluded that southward directed interplanetary magnetic fields within CIRs/HSSs may be the main energy source for long-term averaged geomagnetic activity on Earth.

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

2013-01-01

237

IPS Observations of Short-Time Scale Interplanetary Activity  

NASA Astrophysics Data System (ADS)

We have carried out a program of continuous Interplanetary Scintillation (IPS) monitoring of the interplanetary activity using Ooty Radio Telescope (ORT). From May 1990 to March 1991, during the 22nd, solar maximum, a few radio sources were monitored to provide long stretches of IPS data with a high-time resolution of few minutes. These observations covered 0.3 to 0.8 AU region (12° to 70° elongations) around the sun at several heliographic latitudes. During the observation, we detected 33 short-time scale IPS events which had significant variation in the scintillation index and solar wind velocity. These were considered to be due to travelling interplanetary disturbances. A multi-component model of plasma density enhancement was developed to estimate the geometry and physical properties of these IPS events. Detailed analysis of 20 of these events suggests, 1. fast IPS events were interplanetary signatures of Coronal Mass Ejections (CMEs), 2. the average mass and energy of these events was ˜ 1016 gm and 1033 erg respectively,3. 80% of IPS events were associated with X-ray flares on the sun and 50% were associated with geomagnetic activity at earth. Detailed study of the multicomponent model suggests IPS observations at smaller elongations (hence at higher radio frequencies) are more suited to detect fast-moving interplanetary disturbances such as produced by CMEs.

Gothoskar, Pradeep; Pramesh Rao, A.

1996-03-01

238

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

239

A pure permanent magnet-two plane focusing-tapered wiggler for a high average power FEL  

SciTech Connect

A high-average power FEL is under construction at Los Alamos. The FEL will have aspects of both an oscillator and a SASE (self-amplified spontaneous emission) device. That is, a high-gain and high- extraction efficiency wiggler will be used with a very low-Q optical resonator. FEL simulations reveal that a tapered wiggler with two- plane focusing is required to obtain desired performance. The wiggler is comprised of a I meter long untapered section followed by a 1 meter tapered section. The taper is achieved with the magnetic gap and not the wiggler period which is constant at 2 cm. The gap is tapered from 5.9 mm to 8.8 mm. The, gap, rather than the period, is tapered to avoid vignetting of the 16 {mu}m optical beam. Two-plane focusing is necessary to maintain high current density and thus high gain through out the 2 meter long wiggler. Several magnetic designs have been considered for the wiggler. The leading candidate approach is a pure permanent wiggler with pole faces that are cut to roughly approximate the classical parabolic pole face design. Focusing is provided by the sextupole component of the wiggler magnetic field and is often called ``natural`` or ``betatron`` focusing. Details of the design will be presented.

Fortgang, C.M.

1996-11-01

240

Pollution potentials in interplanetary space  

NASA Astrophysics Data System (ADS)

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

Keay, C. S. L.

241

What is the fate of interplanetary dust  

Microsoft Academic Search

The following general picture of the interplanetary dust is presented: (1) size distribution; (2) spatial distribution; (3) composition; (4) dynamics; and (5) origin. The solar probe mission provides a unique opportunity to study the evolution of the interplanetary dust and its eventual destruction near the sun. Two destructive processes (fragmentation and vaporization) of interplanetary dust are discussed.

M. S. Hanner

1978-01-01

242

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

Microsoft Academic Search

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

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

2008-01-01

243

Evolution and interaction of large interplanetary streams  

SciTech Connect

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.

1985-02-01

244

Magnetic Field Measurements by Pioneer 8. Part 2: Hourly Averages of the Field Elements from 8 Dec. 1968 - 20 Dec. 1969 (Bartels' Solar Rotation 1852 to 1865).  

National Technical Information Service (NTIS)

The magnetic field data in the solar ecliptic reference system are presented in graphical form. Hourly averages of field intensities, latitude and longitude of the field vector, and variances are shown for Bartel's solar rotation from 1852 to 1865.

F. Mariani N. F. Ness C. Irace

1975-01-01

245

Solar-diurnal variations of Cosmic rays (CR), connected with the passage of the Earth through the Neutral Layer of the Interplanetary Magnetic Fields (IMF) and the earthquake problem  

NASA Astrophysics Data System (ADS)

Key explanation on effect of Fundamental Law of Momentum Conservation is given on the basis of Cosmo-Physical processes, which can be connected with all kinds of recently known geo-effective phenomena. Many works have been devoted to searches of extraterrestrial sources of generation of earthquake initiation preconditions. There is a direct indication on the fact in these works that all kinds of geo-active fluxes of plasma, which goes ahead of strong geomagnetic storms, concomitant to the earthquakes, may be served as favourable conditions for earthquake appearance. If in one group of works, the increase of seismic activity during geo-active solar flare is reported, then in the other group of works, there is the direct indication on the fact, that it is necessary to study the mechanism of generation of electro-magnetic emanation in the seismically active regions of Earth. Certain strong destructive earthquakes are putting in touch by some authors with the outburst of cosmic rays in distant regions of Universe during stellar explosion of supernovae. It's impossible to avoid our attention from announcement of 100% increase of hard component of cosmic radiation above Yerevan 30 minutes ahead of 1988 Spitak Earthquake. And finally, the data on article, in which is shown that about 75% of earthquakes with magnitude M>=6 takes place during traverse of neutral layer of Interplanetary Magnetic Field by the Earth, in the presence of good correlation with 11-years cycle of Solar Activity. Above mentioned geo-effective phenomena, with an increasable amount, can be reviewed in frame of the Law of Momentum Conservation, if we take into account the peculiarities of its development for a given specific cases.

Khazaradze, N.; Vanishvili, G.; Bakradze, T.; Kordzadze, L.; Bazerashvili, E.; Elizbarashvili, M.

2013-02-01

246

The evolution of interplanetary shocks  

Microsoft Academic Search

Unambiguous identification of the solar events associated with 48 interplanetary (IP) shocks has been facilitated by the observation of radio emission generated by the shocks. This identification makes possible an investigation of the way in which these shocks evolve and of the relationship between solar event 'strength' and shock velocity. All but two of the 48 solar events associated with

H. V. Cane

1985-01-01

247

Interplanetary round trip mission design  

Microsoft Academic Search

This paper defines the basic constraints for interplanetary round trip travel or, equivalently, for round trip travel from and to a natural or artificial satellite, such as round trips from the International Space Station to another satellite and back. While the constraints are straightforward, they do not seem to have been discussed previously in the literature, perhaps because round trip

James R. Wertz

2004-01-01

248

Revised Landau damping rates of magnetohydrodynamic waves in hot magnetized equilibrium plasmas and its consequences for cosmic ray transport in the interplanetary medium  

Microsoft Academic Search

A relativistic theory of transverse oscillations in hot, magnetized, isotropic equilibrium plasmas is presented. The special theory of relativity enters the description with the requirement that the particle masses depend on the particle velocities which themselves are limited by the speed of light. Using the relativistic Maxwell-Boltzmann-Jüttner (MBJ) distribution correctly describing the equilibrium state of a plasma, we formulate the

R. Schlickeiser; H. Fichtner; M. Kneller

1997-01-01

249

Use of single-component wind speed in Rankine-Hugoniot analysis of interplanetary shocks  

Microsoft Academic Search

We have extended and deployed a routine designed to run independently on the Web providing real-time analysis of interplanetary shock observations from L1. The program accesses real-time magnetic field, solar wind speed, and proton density data from the Advanced Composition Explorer (ACE) spacecraft, searches for interplanetary shocks, analyzes shocks according to the Rankine-Hugoniot (R-H) jump conditions, and provides shock solutions

Vasiliy S. Vorotnikov; Charles W. Smith; Charles J. Farrugia; Calum J. Meredith; Qiang Hu; Adam Szabo; Ruth M. Skoug; Christina M. S. Cohen; Andrew J. Davis; Kiyohumi Yumoto

2011-01-01

250

Plasma and energetic particle structure upstream of a quasi-parallel interplanetary shock  

Microsoft Academic Search

This paper assembles ISEE 1, 2, and 3 observations of the interplanetary magnetic and electric fields, plasma, magnetohydrodynamic waves, electromagnetic and electrostatic plasma waves, 1- to 6-keV protons and electrons, and >30-keV\\/Q ions for the interplanetary shock of November 12, 1978. The shock was high speed (640 km s⁻¹), supercritical, quasi-parallel, and an efficient accelerator of energetic protons. The flux

C. F. Kennel; F.L. Scarf; F. V. Coroniti; C.T. Russell; K.-P. Wenzel; T. R. Sanderson; P. Van Nes; W. C. Feldman; G. K. Parks; E. J. Smith; B. T. Tsurutani; F. S. Mozer; M. Temerin; R. R. Anderson; J. D. Scudder; M. Scholer

1984-01-01

251

Interplanetary sector boundaries 1971-1973  

NASA Astrophysics Data System (ADS)

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.

1980-05-01

252

Magnetohydrodynamic Simulations of Interplanetary Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

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

2013-11-01

253

The June 1st 2008 CME in the Interplanetary Medium  

NASA Astrophysics Data System (ADS)

In this work we present a combined study/analysis of the counterpart of the CME of June 1st of 2008 in the interplanetary medium. This event has been largely studied because of its peculiar initiation and its possible forecasting consequences for space weather. We show an in situ analysis of the CME in the interplanetary medium in order to shed some light on the propagation and evolution mechanisms of the ICME. The energetic particles play an important role in order to understand the overall event, the source on the Sun and the effect over the Earth. The typical shock associated characteristics with the counterpart of the CMEs in the interplanetary medium has been determined, in order to understand the propagation properties. The magnetic cloud has been studied and analyzed using non force-free models as start point to incorporate expansion. To accomplish this analysis the IMPACT/STEREO B in-situ measurement have been considered in order to characterize the Interplanetary CME.

Nieves-Chinchilla, T.; F.-Vinas, A.; Gomez-Herrero, R.; Malandraki, O. E.; Dresing, N.; Hidalgo, M. A.; Davila, J.

2010-05-01

254

SPATIAL OFFSETS OF INTERPLANETARY ION AND ELECTRON SOURCE REGIONS  

SciTech Connect

Observations of impulsive solar energetic particles provide unique insight into the process of particle acceleration in the solar atmosphere. X-ray and gamma-ray observations of precipitating particles from solar flares have shown offsets between the ion and the electron emission. We present Advanced Composition Explorer (ACE) observations of interplanetary energetic ion and suprathermal electron events with intensity variations related to connection or lack thereof to the particle source. These results indicate an offset between the acceleration regions of ions and electrons of the same order of magnitude as that observed in the gamma-ray events. However, if the particle event originates at the magnetic footpoints of an interplanetary coronal mass ejection, the ACE observations do not exhibit this offset, suggesting that different magnetic geometry or acceleration processes may be present in those regions.

Chollet, E. E. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Giacalone, J. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Skoug, R. M.; Steinberg, J. T. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States)

2009-11-10

255

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

256

Solar Cycle Variations in Relations between Solar, Interplanetary and  

Microsoft Academic Search

We continue our investigation (see for instance, Yermolaev Yu.I., Yermolaev M.Yu. Statistical relationships between solar, interplanetary, and geomagnetic disturbances 1976-2000, Cosmic Research, v.40, N 1, p.1-14, 2002) where we study 25-year sets of solar X-ray observations, measurements of plasma and magnetic field parameters in the solar wind and Dst index variations with the purpose of revealing the factors rendering the

Yu. I. Yermolaev; M. Yu. Yermolaev; A. A. Petrukovich

2003-01-01

257

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

258

Coronal and interplanetary propagation, interplanetary acceleration, cosmic-ray observations by deep space network and anomalous component  

NASA Astrophysics Data System (ADS)

The purpose is to provide an overview of the contributions presented in sessions SH3, SH1.5, SH4.6 and SH4.7 of the 19th International Cosmic Ray Conference. These contributed papers indicate that steady progress continues to be made in both the observational and the theoretical aspects of the transport and acceleration of energetic charged particles in the heliosphere. Studies of solar and interplanetary particles have placed emphasis on particle directional distributions in relation to pitch-angle scattering and magnetic focusing, on the rigidity and spatial dependence of the mean free path, and on new propagation regimes in the inner and outer heliosphere. Coronal propagation appears in need of correlative multi-spacecraft studies in association with detailed observation of the flare process and coronal magnetic structures. Interplanetary acceleration has now gone into a consolidation phase, with theories being worked out in detail and checked against observation.

Ng, C. K.

1985-08-01

259

Helicity transport from solar convection zone to interplanetary space  

NASA Astrophysics Data System (ADS)

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

Zhang, Mei

2013-07-01

260

Observations of the interplanetary plasma  

Microsoft Academic Search

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

W. I. Axford

1968-01-01

261

The effect of inhomogeneity of toroidal magnetic field on the solutions of bounce-averaged Fokker-Planck equation on Tore Supra  

NASA Astrophysics Data System (ADS)

In order to access more consistently RF current drive problems on Tore Supra, 2D relativistic Fokker-Planck equation for the electron distribution function is bounce-averaged by introducing the inhomogeneity of magnetic field along a toroidal direction. Assuming a large aspect ratio tokamak with circular magnetic surfaces, we obtained the approximate formulas for the bounce-averaged coefficients involved in the calculation of electron fluxes driven by the electric field and collisions in the bounce-averaged Fokker-Planck equation in the toroidal magnetic field geometry created by N discrete magnetic coils, represented by B?(r,Vthgr)=B(r,Vthgr=0)(1+?)/1+Vegr cos(Vthgr)[1-?(r,Vthgr)cos(N Jgr)], where Vegr=r/R0(<<1), R0 and r are the major and minor radii of the torus, ? is the magnetic ripple depth, Vthgr and Jgr are the poloidal and toroidal angles, respectively. These approximate formulas were in very good agreements with the exact numerical solutions. Applying these formulas for relevant Tore Supra parameters, it is found out that the effects of inhomogeneity of totoidal magnetic field on the solutions of bounce-averaged Fokker-Planck equation are very negligible even in the highest ripple regions on Tore Supra. .

Ju, Myunghee; Peysson, Yves; Basiuk, Vincent

2001-10-01

262

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

SciTech Connect

The authors present a study of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. The results constrain theories of the acceleration of the solar wind and of the evolution of fluctuation amplitudes. They show that the magnetic fluctuation amplitude normalized by the strength of the magnetic field is largely independent of stream structure at the scales studied. Using this fact, they find that the WKB prediction generally provides a good approximation to the magnetic amplitude evolution for all but the smallest scales in the inner heliosphere, which show a dissipation with respect to the WKB prediction, and the largest scales in the outer heliosphere, which decrease more slowly than the simple theory predicts. Velocity fluctuations are shown to generally follow the level of the magnetic fluctuations at the higher frequencies of this study, although it is the energy densities of the velocity and magnetic fluctuations that correlate well rather than the velocity and magnetic fluctuations themselves. Near 0.3 AU the energy in the largest scale velocity fluctuations is, on average, a few times larger than that in the magnetic fluctuations, but with increasing heliocentric distance the magnetic fluctuations become slightly dominant on all scales. The dominance of the kinetic energy in the inner heliosphere is limited to the radial component of the velocity while the transverse components exhibit a more wave-like near equipartition between kinetic and magnetic energy.

Roberts, D.A.; Goldstein, M.L. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Klein, L.W. (Applied Research Corp., Landover, MD (United States))

1990-04-01

263

Cusp/cleft auroral forms and activities in relation to ionospheric convection: Responses to specific changes in solar wind and interplanetary magnetic field conditions  

SciTech Connect

The authors describe in detail a four hour period on Dec 17, 1992, of cusp/cleft region observations, made in conjunction with the occurance of a transient auroral event. There was an IMF directional discontinuity where the fields changed from positive IMF B{sub y} (B{sub z}{much_lt}0) to large negative B{sub y} (B{sub z}>0) in conjunction with a change in convection direction in the cusp region. They present data from satellite observations, in addition to ground based data collected over an array of stations in Greenland and Svalbard. They view this as a first step toward an effort to correlate responses in the ionosphere to different solar wind and interplantetary magnetic field conditions. They analyze this data in terms of the array of different conditions which was exhibited in the ionosphere over this four hour period.

Sandholt, P.E. [Univ., of Oslo, Oslo (Norway); Farrugia, C.J. [Univ. of Malta, Msida (Malta); Stauning, P. [Danish Meteorological Institute, Copenhagen (Denmark); Crowley, S.W.H. [Imperial College, London (United Kingdom)

1996-03-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

265

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.

266

Observations of interplanetary scintillation in China  

NASA Astrophysics Data System (ADS)

The Sun affects the Earth in multiple ways. In particular, the material in interplanetary space comes from coronal expansion in the form of solar wind, which is the primary source of the interplanetary medium. Ground-based Interplanetary Scintillation (IPS) observations are an important and effective method for measuring solar wind speed and the structures of small diameter radio sources. In this paper we will discuss the IPS observations in China.

Liu, Li-Jia; Peng, Bo

2013-07-01

267

THE SOLAR ORIGIN OF SMALL INTERPLANETARY TRANSIENTS  

SciTech Connect

In this paper, we present evidence for magnetic transients with small radial extents ranging from 0.025 to 0.118 AU measured in situ by the Solar-Terrestrial Relations Observatory (STEREO) and the near-Earth Advanced Composition Explorer (ACE) and Wind spacecraft. The transients considered in this study are much smaller (<0.12 AU) than the typical sizes of magnetic clouds measured near 1 AU ({approx}0.23 AU). They are marked by low plasma beta values, generally lower magnetic field variance, short timescale magnetic field rotations, and are all entrained by high-speed streams by the time they reach 1 AU. We use this entrainment to trace the origin of these small interplanetary transients in coronagraph images. We demonstrate that these magnetic field structures originate as either small or large mass ejecta. The small mass ejecta often appear from the tip of helmet streamers as arch-like structures and other poorly defined white-light features (the so-called blobs). However, we have found a case of a small magnetic transient tracing back to a small and narrow mass ejection erupting from below helmet streamers. Surprisingly, one of the small magnetic structures traces back to a large mass ejection; in this case, we show that the central axis of the coronal mass ejection is along a different latitude and longitude to that of the in situ spacecraft. The small size of the transient is related to the in situ measurements being taken on the edges or periphery of a larger magnetic structure. In the last part of the paper, an ejection with an arch-like aspect is tracked continuously to 1 AU in the STEREO images. The associated in situ signature is not that of a magnetic field rotation but rather of a temporary reversal of the magnetic field direction. Due to its 'open-field topology', we speculate that this structure is partly formed near helmet streamers due to reconnection between closed and open magnetic field lines. The implications of these observations for our understanding of the variability of the slow solar wind are discussed.

Rouillard, A. P. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Sheeley, N. R. Jr; Cooper, T. J. [Naval Research Laboratory, Washington, DC 29375-5352 (United States); Davies, J. A. [RAL Space, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Lavraud, B.; Opitz, A.; Sauvaud, J.-A. [Centre d'Etude Spatiale des Rayonnements, Universite de Toulouse, 21028, Toulouse (France); Kilpua, E. K. J. [Department of Physical Sciences, Theoretical Physics Division, University of Helsinki (Finland); Skoug, R. M.; Steinberg, J. T. [Space Science and Applications, Los Alamos National Laboratory, MS-D466, Los Alamos, NM 87545 (United States); Szabo, A. [NASA Goddard Space Flight Center, Greenbelt, Maryland, MD 20771 (United States)

2011-06-10

268

The effect of adiabatic energy loss during interplanetary propagation of solar energetic particles  

Microsoft Academic Search

Because of the divergence of the solar wind flows, energetic particles should experience adiabatic energy loss almost everywhere in the interplanetary space. The energy loss of particles gyrating in magnetic fields is a pitch-angle dependent process and it is present with or without particle scattering by magnetic turbulences. The energy loss is much faster close to sun than at large

G. Qin; M. Zhang

2004-01-01

269

Nozomi observation of interplanetary transients ejected as limb coronal mass ejections  

Microsoft Academic Search

The magnetic fields of interplanetary objects that were ejected as coronal mass ejections (CMEs) from the limb of the Sun were observed by the NOZOMI spacecraft at 1.38 AU above the east limb of the Sun. The solar wind magnetic field whose launch time coincided with ejection of the limb CME was different from that estimated from ACE observations near

T. Nakagawa; A. Matsuoka

2002-01-01

270

The local characteristic function of interplanetary particle propagation  

NASA Astrophysics Data System (ADS)

An easily measurable intensity function which characterizes the interplanetary propagation of charged solar flare particles is presented. This function is nearly time invariant during a solar event despite the large variations of intensity and anisotropy, but varies from event to event. It characterizes the systematic and stochastic forces of the interplanetary magnetic field which focus and scatter the particles in pitch angle. The model of focused transport shows that this function is essentially determined by the local shape and amplitude of the pitch angle diffusion coefficient kappa (mu) and by the local value of the focusing length. The time profile of the solar particle injection is typically of negligible influence. The local characteristic function may be used as a powerful new tool for a systematic analysis of flare particle angular distributions, Examples are given.

Green, G.; Schlueter, W.

1985-08-01

271

Interplanetary scattering mean free path: Collisionless wave-damping effects  

SciTech Connect

Waves with small wavelengths are responsible for the scattering of particles with small values of ..mu.. (where ..mu.. is the cosine of the particle pitch angle). However, these waves are strongly damped in a thermal plasma by the process of collisionless cyclotron damping. This damping severely reduces theamplitude of the waves at small wavelengths and, in turn, results in a severely reduced scattering rate near ..mu.. = 0. This effect allows the mean free path for some particles to be much longer than the value estimated from standard quasi-linear theory. To demonstrate this point, a specific model for the observed interplanetary magnetic turbulence spectrum is chosen which is consistent with current observational constraints and also reflects the effects of collisionless wave damping. The consequences of these assumptions for the calculation of the interplanetary mean free path are explored. Specific predictions of the theory regarding the propagation of protons are best described by considering three separate kinetic energy regimes.

Davila, J.M.; Scott, J.S.

1984-10-01

272

Active shielding for long duration interplanetary manned missions  

NASA Astrophysics Data System (ADS)

For long duration interplanetary manned missions the protection of astronauts from cosmic radiation is an unavoidable problem that has been considered by many space agencies. In Europe, during 2002-2004, the European Space Agency supported two research programs on this thematic: one was the constitution of a dedicated study group (on the thematic 'Shielding from cosmic radiation for interplanetary missions: active and passive methods') in the framework of the 'life and physical sciences' report, and the other an industrial study concerning the 'radiation exposure and mission strategies for interplanetary manned missions to Moon and Mars'. Both programs concluded that, outside the protection of the magnetosphere and in the presence of the most intense and energetic solar events, the protection cannot rely solely on the mechanical structures of the spacecraft, but a temporary shelter must be provided. Because of the limited mass budget, the shelter should be based on the use of superconducting magnetic systems. For long duration missions the astronauts must be protected from the much more energetic galactic cosmic rays during the whole mission period. This requires the protection of a large habitat where they could live and work, and not the temporary protection of a small volume shelter. With passive absorbers unable to play any significant role, the use of active shielding is mandatory. The possibilities offered by superconducting magnets are discussed, and recommendations are made about the needed R&D. The technical developments that have occurred in the meanwhile and the evolving panorama of possible near future interplanetary missions, require revising the pioneering studies of the last decades and the adoption of a strategy that considers long lasting human permanence in 'deep' space, moreover not only for a relatively small number of dedicated astronauts but also for citizens conducting there 'normal' activities.

Spillantini, Piero

2010-04-01

273

Solar and interplanetary origins of the November 2004 superstorms  

NASA Astrophysics Data System (ADS)

During the first half of November 2004, many solar flares and coronal mass ejections (CMEs) were associated with solar active region (AR) 10696. This paper attempts to identify the solar and interplanetary origins of two superstorms which occurred on 8 and 10 November with peak intensities of Dst = -373 nT and -289 nT, respectively. Southward interplanetary magnetic fields within a magnetic cloud (MC), and a sheath + MC were the causes of these two superstorms, respectively. Two different CME propagation models [Gopalswamy, N., Yashiro, S., Kaiser, M.L. et al. Predicting the 1-AU arrival times of coronal mass ejections. J. Geophys. Res. 106, 29207-29219, 2001; Gopalswamy, N.S., Lara, A., Manoharan, P.K. et al. An empirical model to predict the 1-AU arrival of interplanetary shocks. Adv. Space Res. 36, 2289-2294, 2005] were employed to attempt to identify the solar sources. It is found that the models identify several potential CMEs as possible sources for each of the superstorms. The two Gopalswamy et al. models give the possible sources for the first superstorm as CMEs on 2330 UT 4 November 2004 or on 1454 UT 5 November 2004. For the second superstorm, the possible solar source was a CME that on 0754 UT 5 November 2004 or one that occurred on 1206 UT 5 November 2004. We note that other propagation models sometimes agree and other times disagree with the above results. It is concluded that during high solar/interplanetary activity intervals such as this one, the exact solar source is difficult to identify. More refined propagation models are needed.

Echer, Ezequiel; Tsurutani, Bruce T.; Guarnieri, Fernando L.

2009-09-01

274

Iron charge distribution as an identifier of interplanetary coronal mass ejections  

Microsoft Academic Search

We present solar wind Fe charge state data measured on the Advanced Composition Explorer (ACE) from early 1998 to the middle of 2000. Average Fe charge states in the solar wind are typically around 9 to 11. However, deviations from these average charge states occur, including intervals with a large fraction of Fe16 which are consistently associated with interplanetary coronal

S. T. Lepri; T. H. Zurbuchen; L. A. Fisk; I. G. Richardson; H. V. Cane; G. Gloeckler

2001-01-01

275

Magnetic Tape Containing Average Elevations of Topography in California and Adjacent Regions for Areas of 1x1 Minutes in Size.  

National Technical Information Service (NTIS)

Average elevations of about 199,000 1x1 and 51,000 3x3 minute 'compartments' in California and vicinity are recored on a magnetic tape. The 1x1 minute coverage extends about 15 miles and the 3x3 minute about 100 miles in all directions beyond the Californ...

S. L. Robbins H. W. Oliver D. Plouff

1973-01-01

276

Multisatellite Observations of Interplanetary Field Enhancements  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) are magnetic structures in the solar wind that have a cusp-shaped maximum in the field strength with a strong current sheet often near the central peak. These structures generally last an hour or more. They have a tendency to be seen more often at specific ecliptic longitudes, have been identified on occasion with particular small solar system bodies (asteroid 2201 Oljato and comet 122P/ De Vico) and attributed to the interaction of the solar wind with charged dust. On occasion they are detected nearly simultaneously by several spacecraft. Multispacecraft detection have been made with PVO, Venera-13 and Venera-14; with ISEE 1 and ISEE 3 and more recently with STEREO A and B, ACE and Wind. In this paper we use a delay matching algorithm developed by D. Weimer on the IFE of December 24, 2006 detected by 4 spacecraft. While the IFE is crossing the four spacecraft separated in Y by 90 Re and in X by 160 Re the measured delay was close to the calculated advection time. Along the apparent center line of the event the delay was close to 4 minutes. This event together with previous events are consistent with IFEs being magnetic structures that are convecting outward from the Sun with nearly, but slightly slower than, the solar wind velocity. We need to understand the occurrence rate of such structures and their physical cause because if this hypothesis is true, they may be responsible for accelerating dust out of the inner solar system.

Russell, C. T.; Weimer, D. R.; Jian, L. K.; Lai, H. R.; Luhmann, J. G.

2008-12-01

277

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

278

Coronal transients and their interplanetary effects  

Microsoft Academic Search

Contents: 1. Introduction. 2. Background material: Ancient history - solar flares and geomagnetic storms. Modern history - interplanetary shock waves. Coronal transients or mass ejections. 3. The present: Theoretical models. New observations of coronal mass ejections. 4. The future: Solar origins. Interplanetary effects.

A. J. Hundhausen; L. F. Burlaga; W. C. Feldman; J. T. Gosling; E. Hildner; L. L. House; R. A. Howard; A. S. Krieger; M. R. Kundu; B. C. Low; N. R. Sheeley Jr.; R. S. Steinolfson; R. T. Stewart; R. G. Stone; S. T. Wu

1984-01-01

279

Solar cycle study of interplanetary Lyman-alpha variations - Pioneer Venus Orbiter sky background results  

SciTech Connect

PVO observations of the interplanetary Ly-alpha (IPL) background, obtained over an entire solar cycle (SC) from 1979 to 1985, are compiled and analyzed statistically, along with data from other instruments and earlier solar cycles. The results are presented in extensive tables and graphs and characterized in detail. Findings reported include SC variation of 1.8 for the longitudinally averaged IPL intensity (in agreement with the variation of the 27-d disk-averaged integrated solar Ly-alpha flux), yearly averaged ecliptic H-atom lifetime at 1 AU equal to 1.0 Ms at solar minimum and 1.5 Ms at solar maximum, interplanetary H density equal to 0.07 + or - 0.01/cu cm, and interplanetary H/He within the heliopause but far from the sun of 7 + or - 3. 74 references.

Ajello, J.M.; Stewart, A.I.; Thomas, G.E.; Graps, A.

1987-06-01

280

Disconnection of coronal field lines due to the emergence of new photospheric flux as the cause of CMEs and interplanetary shocks  

Microsoft Academic Search

A scenario is presented whereby CMEs and interplanetary shocks are consequences of a large scale rearrangement of the coronal magnetic field induced by the disconnection of field lines from the solar surface due to the emergence of flux with opposite polarity. In this scenario the CME is the mass released from the previously closed structure and the interplanetary shock is

S. Bravo

1996-01-01

281

Propagation of normal and faster CMEs in the interplanetary medium  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

282

Steady State Chaotic Magnetic Fields and Particle Dynamics Cross-field Transport of Particles in Chaotic Magnetic Fields  

Microsoft Academic Search

The observed propagation of cosmic rays in the interplanetary space cannot be explained unless there is diffusion of the energetic particles across the interplanetary magnetic field. The cross-field diffusion of cosmic rays is assumed to be due to the chaotic nature of the interplanetary\\/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and

B. Dasgupta; A. Ram

2009-01-01

283

Infrared emission from interplanetary dust  

SciTech Connect

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

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

1989-02-01

284

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

285

Research on prediction techniques for the time dependence of solar particle events and geomagnetic activity from results of synoptic analysis of solar and interplanetary particle, plasma and field observations. Final report 1 Jul 75-30 Sep 79  

Microsoft Academic Search

A total of eight scientific techniques have been investigated as an aid for prediction of solar energetic particle events and geomagnetic storms; (1) Synoptic analysis of interplanetary data; (2) H sub ALPHA synoptic charts of low coronal magnetic structure; (3) Solar wind mapping of high coronal emission longitude of solar wind plasma and large-scale interplanetary magnetic field lines; (4) Analysis

E. C. Roelof; R. E. Gold

1980-01-01

286

Shielding Structures for Interplanetary Human Mission  

NASA Astrophysics Data System (ADS)

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

Tracino, Emanuele; Lobascio, Cesare

2012-07-01

287

Relationship between interplanetary quantities and Birkeland current densities  

SciTech Connect

We have examined the relationship between hourly values of solar wind density, speed and the interplanetary magnetic field and the densities of Region 1 Birklend current densities. Data acquired from 51 passes in the morning sector (0800 to 1300 MLT) during IMF b/sub y/>0 and 74 passes in the afternoon sector (1100 to 1600 MLT) during IMF b/sub y/<0 were used in this study. This separation of data by polarity of IMF b/sub y/ was done to avoid the compligated bipagb IP091482 MG100482.

Iijima, T.; Potemra, T.A.

1982-04-01

288

Average Speed  

NSDL National Science Digital Library

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

Horton, Michael

2009-05-30

289

On the role of interplanetary sources in the evolution of low-frequency Alfvenic turbulence in the solar wind  

SciTech Connect

The role of local interplanetary sources in the evolution of low-frequency Alfvenic turbulence in solar wind was investigated by studying a solar wind region with high differential kinetic energy at different heliocentric distances inside 1 AU, with focus placed on large-scale fluctuations. Results of a detailed analysis, based on hourly averages of plasma and magnetic field data of Helios 2, indicated that, at least for the inner heliosphere, an established view that local sources of waves play a relevant role in driving the Alfvenic turbulence evolution is not realistic. It is proposed that such evolution, especially at large scales, is governed by interactions of the outward waves of solar origin with the wind structure. 27 refs.

Bavassano, B.; Bruno, R. (CNR, Ist. di Fisica dello Spazio Interplanetario, Frascati (Italy))

1992-12-01

290

Interplanetary Sample Canister for Mars Sample Return  

NASA Astrophysics Data System (ADS)

We propose the development of an Interplanetary Sample Canister (ISC) for the Mars Sample Return (MSR) mission using CubeSat and Microfabricated Electrospray Propulsion (MEP) technology to enable a lower cost MSR mission.

Strange, N. J.; Klesh, A. T.; Marrese-Reading, C. M.; Oh, D. Y.; Ziemer, J. K.; McElrath, T. P.; Landau, D. F.; Grebow, D. J.

2012-06-01

291

Interplanetary space transport using inertial fusion propulsion.  

National Technical Information Service (NTIS)

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 missio...

C. D. Orth

1998-01-01

292

Suprathermal ions upstream from interplanetary shocks  

Microsoft Academic Search

Suprathermal ions with energies between solar wind thermal energies and approx.29 keV are occasionally observed ahead of outward propagating interplanetary shocks with the Los Alamos\\/Garching fast plasma experiment on ISEE 1 and 2. Compared with suprathermal ion velocity distributions observed upstream from the earth's bow shock, the upstream interplanetary shock ion velocity distributions are relatively structureless, and the particle fluxes

J. T. Gosling; S. J. Bame; W. C. Feldman; G. Paschmann; N. Sckopke; C.T. Russell

1984-01-01

293

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

Microsoft Academic Search

The Venus bow shock location has been measured at nearly 2000 shock crossings, and its dependence on solar EUV, solar wind conditions, and the interplanetary magnetic field determined. The shock position at the terminator varies from about 2.14 Venus radii at solar minimum to 2.40 Venus radii at solar maximum. The location of the shock varies little with solar wind

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

1988-01-01

294

Study of interplanetary structure plasma parameters and ground cosmic ray modulation  

NASA Astrophysics Data System (ADS)

Interplanetary coronal mass ejections (ICMEs) are gigantic clouds of ionized gas launched from the Sun. These structures populate the interplanetary medium, frequently hit the planets. Depending on their characteristic and orientation, they may transfer their energy which is necessary to cause the geomagnetic storms, to the Earth's magnetosphere. ICMEs can be studied according to the variability of interplanetary magnetic field (IMF) and plasma parameters, such as, field intensity, direction, proton density (Np ), proton speed (VP ), radial component of proton temperature (Tp ), and plasma beta (?) which is defined as the ratio between thermal pressure and magnetic pressure. By using the minimum variance analysis (MVA) method, it is possible to identify the plane of maximum variance of the magnetic field data sets, and the eigenvector normal corresponding to the axis of the magnetic clouds. This allows to obtain the azimuthal (?k ) and inclination (?k ) axis orientation in relation to the ecliptic plane. The objective of this work is to study these ICME characteristics and their relation with modulation of ground level cosmic rays. To do this, IMF and plasma data from the Advanced Composition Explorer (ACE) spacecraft, and >50 GeV cosmic ray data from the multidirectional muon telescope installed in the Southern Space Observatory (OES/CRS/CIE/INPE - MCT) in São a Martinho da Serra, Brazil, will be used. Geomagnetic response to the interplanetary structures will be studied using the Dst index.

Kemmerich, Níkolas; Deives Kummer, Fabricio; Vinicius Dias Silveira, Marcos; Schuch, Nelson Jorge; Dal Lago, Alisson; Munakata, Kazuoki; Kuwabara, Takao; Echer, Ezequiel; Martins da Silva, Samuel; da Silva, Marlos; Braga, Carlos Roberto

295

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

Microsoft Academic Search

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

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

1990-01-01

296

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

297

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

Microsoft Academic Search

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

H. V. Cane; I. G. Richardson

2003-01-01

298

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

299

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

Microsoft Academic Search

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

G. E. Blanford; K. L. Thomas; D. S. McKay

1988-01-01

300

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

SciTech Connect

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

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

1982-01-01

301

In situ observations of coronal mass ejections in interplanetary space  

SciTech Connect

Coronal mass ejections, CMEs, in the solar wind at 1 AU generally have distinct plasma and field signatures by which they can be distinguished from the ordinary solar wind. These include one or more of the following: helium abundance enhancements, ion and electron temperature depressions, unusual ionization states, strong magnetic fields, low plasma beta, low magnetic field variance, coherent field rotations, counterstreaming (along the field) energetic protons, and counterstreaming suprathermal electrons. The most reliable of these appears to be counterstreaming electrons, which indicates that CMEs at 1 AU typically are closed field structures either rooted at both ends in the Sun or entirely disconnected from it as plasmoids. About 1/3 of all CMEs have sufficiently high speeds to produce transient interplanetary shock disturbances at 1 AU; the remainder simply ride along with the solar wind. The frequency of occurrence of CMEs in the ecliptic plane, as distinguished by the counterstreaming electron signature, varies roughly in phase and amplitude with the 11-yr solar activity cycle. Near solar maximum they account for {approximately} 15% of all solar wind measurements, while near solar minimum they account for less than 1% of all the measurements. All but one of the 37 largest geomagnetic storms near the last solar maximum were associated with Earth-passage of interplanetary disturbances driven by fast CMEs; that is, CMEs are the prime link between solar and geomagnetic activity. However, more than half of all earthward directed CMEs are relatively ineffective in a geomagnetic sense. 19 refs., 6 figs.

Gosling, J.T.

1991-01-01

302

Variations in the large-scale polar solar magnetic flux: The average annual series of the ? index in 1858-2006  

NASA Astrophysics Data System (ADS)

A long series of the known ? index of the solar corona structure has been proposed. It seems that this index, which characterizes the limb extension of polar coronal plume systems, is of importance because it is related to the large-scale polar solar magnetic flux. Solar corona photographs and drawings during total solar eclipses, collected for 13 solar activity cycles from different sources (78 eclipses), as well as H-alpha map data on the drift of the high-latitude belt of filaments before polarity reversal of the polar magnetic field have been used. Daily solar corona images, obtained on the SOHO spacecraft (using an EIT ultraviolet telescope), have been additionally used. The series of the average annual ? index values in 1858-2006 in the Northern and Southern solar hemi-spheres (including the values in the alternating variant, i.e., with regard to the magnetic field sign) have been created by synthesizing these data. The obtained series have been studied in the context of a comparison with other indices characterizing different components of the general solar magnetic field.

Guseva, S. A.; Nagovitsyn, Yu. A.

2012-07-01

303

Elliptical magnetic clouds and geomagnetic storms  

Microsoft Academic Search

Magnetic clouds are simple phenomena which modulate the interplanetary space and they are a subset of Interplanetary Coronal Mass Ejections. Due to the sustained orientation of their magnetic fields south- and northwards, they can influence the Earth's magnetosphere and may give rise to geomagnetic storms. Since such storms are dominant factors of space weather predictions, magnetic clouds are an important

I. Antoniadou; A. Geranios; M. Vandas; M. Panagopoulou; O. Zacharopoulou; O. Malandraki

2008-01-01

304

INTERPLANETARY SHOCKS LACKING TYPE II RADIO BURSTS  

SciTech Connect

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

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

2010-02-20

305

Interplanetary drivers of ionospheric prompt penetration electric fields  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

306

Helium at Interplanetary Discontinuities: ACE STEREO Observations and Simulations  

NASA Astrophysics Data System (ADS)

ACE/SEPICA observations showed that, on average, energetic He+ is after H+ and He2+ the third most abundant energetic particle species in the heliosphere. Depending on the type of the energetic population the He+/He2+ ratio can reach unusually high values in the energy range 250 - 800keV/n ratios up to unity. As a major source of energetic He+ interplanetary pickup ions have been identified that are preferentially accelerated at co-rotating interaction regions (CIRs), transient interaction regions (TIRs), and interplanetary traveling shocks. Most recent data from STEREO/PLASTIC in the energy range of 0.2-80keV/Q show clear evidence of abundant He+ at interplanetary discontinuities. Thus PLASTIC extends the energy range into injection region of the source. Furthermore, ACE/ULEIS and ACE/SEPICA measurements showed that very often 3He2+ and He+ are also accelerated simultaneously at CME-driven IP shocks. This is surprising because, these to species originate from different sources. However, this may indicate that the injection, or the acceleration efficiency of the accelerator for different source population may be similar. From observations, however, this cannot be differentiated easily. In numerical simulations this can be done because there is control over species and distribution functions. In a numerical study we applied test particle simulations and multi-dimensional hybrid simulations to address the contribution of source, injection and acceleration efficiency at shocks to the variability of the helium ratio. These, simulations with and without superimposed turbulence in the shock region will be compared with observations.

Moebius, E.; Kucharek, H.; Allegrini, F.; Desai, M.; Klecker, B.; Popecki, M.; Farrugia, C.; Galvin, A.; Bochsler, P.; Karrer, R.; Opitz, A.; Simunac, K.

2007-12-01

307

Multiple spacecraft observations of interplanetary shocks: ISEE 3-D plasma measurements  

SciTech Connect

ISEE 1 and ISEE 3 three-dimensional solar wind plasma measurements are used together with magnetic field measurements across five previously studied interplanetary shocks to test the accuracy of the mixed-mode shock-normal determination technique and to test whether the shock properties are best approximated with a ratio of specific heats of 5/3 or 2. In the shocks examined, the assumption that the velocity jump was along the normal provided an estimate of the shock normal within 15/sup 0/ of our best fit normal 50% of the time and within 50/sup 0/, 90% of the time. The mixed-mode normals lay within 12/sup 0/ of our best fit normal 50% of the time and within 36/sup 0/, 90% of the time. Part of this deviation may be due to differnces in the orientation of the local normal from that of the average normal. Finally, the jump in plasma and field across the shock is better predicted from the Rankine-Hugoniot equations using a ratio of specific heats (4) of 5/3 rather than 2.

Russell, C.T.; Gosling, J.T.; Zwickl, R.D.; Smith, E.J.

1983-12-01

308

Local and global scattering properties of the interplanetary medium obtained from Solar Energetic Particles (SEPs)  

NASA Astrophysics Data System (ADS)

Solar energetic particles can be used as probes for the turbulence level in the interplanetary medium. It is of general interest to compare the LOCAL scattering properties near an observer with GLOBAL properties which characterize the average scattering along the magnetic field. We discuss various methods by which the scattering conditions can be determined: (1) overall fits of observed particle intensities and anisotropies to a transport model; (2) evaluation of the steady-state pitch angle distribution; and (3) suitably normalized angular distributions during the intensity maximum of a particle event. Energetic particle data from HELIOS 1/2 are analyzed, and the mean free paths obtained with the different methods are compared with each other. As a result one can state: (1) for a number of solar particle events the radial mean free path is essentially constant between the Sun and Helios; and (2) large variations in the degree of scattering exist from one event to the other. These results indicate the existence of 'regimes' where the amount of particle scattering is relatively constant over extended regions in radius and azimuth, but with marked differences from one regime to the other.

Wibberenz, G.; Hatzky, R.; Bieber, J. W.

1995-06-01

309

Fast Numerical Integration of Interplanetary Orbits.  

National Technical Information Service (NTIS)

Mathematical considerations on the stability of the numerical integration of interplanetary orbits lead to a step-size control for the time that minimizes the computation time. The controls are derived from the eigenvalues of the Jacobian of the right-han...

F. Debatin A. Tilgner F. Hechler

1986-01-01

310

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

311

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

312

Interplanetary shocks preceded by solar filament eruptions  

SciTech Connect

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

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

1986-12-01

313

On interplanetary coronal mass ejection identification at 1 AU  

SciTech Connect

Coronal mass ejections are believed to be produced in the corona from closed magnetic regions not previously participating in the solar wind expansion. At 1 AU their interplanetary counterparts (ICMEs) generally have a number of distinct plasma and field signatures that distinguish them from the ambient solar wind. These include heat flux dropouts, bi-directional streaming, enhanced alpha particle events, times of depressed proton temperatures, intervals of distorted or enhanced magnetic field, and times of large magnetic field rotations characteristic of magnetic clouds. The first three of these signatures are phenomena that occur at some point within the ICME, but do not necessarily persist throughout the entire ICME. The large scale magnetic field rotations, distortions and enhancements, and the proton temperature depressions tend to mark more accurately the beginning and end of the ICME proper. We examine herein the reliability with which each of these markers identifies ICMEs utilizing ISEE-3 data from 1978{endash}1980. {copyright} {ital 1999 American Institute of Physics.}

Mulligan, T.; Russell, C.T. [Institute of Geophysics and Planetary Physics and the Department of Earth and Space Sciences University of California Los Angeles (United States); Gosling, J.T. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1999-06-01

314

The interplanetary origins and the main-phase development of moderate geomagnetic storms (1978 - 1979)  

NASA Astrophysics Data System (ADS)

Geomagnetic storms are related to the ring current, which is driven by energy injection primarily during energetic solar wind-magnetosphere coupling due to reconnection at the magnetopause. This work identified the interplanetary origins of moderate geomagnetic storms (-100 nT less than or equal to Dst(MIN) less than -50 nT) and analyzed the coupling processes during the storm main phase. For this purpose the interplanetary magnetic field, solar-wind temperature, density and velocity data, obtained by the ISEE-3 satellite, were used together with the equatorial-Dst and auroral-AE geomagnetic indices, provided by the World Data Center, for the interval August/1978 - December/1979. 78 moderate storms were identified, in which 40 storm events (Dst beginning at approximately 0 nT) were selected. Related to these well defined events the following interplanetary origins were found: coronal mass ejections phenomena - CME (40 percent related to interplanetary shocks; 22.5 percent to single streams; 17.5 percent to streams interactions; 10 percent to non-compressive density enhancement) and non-CME phenomena (7.5 percent related to Alfven-like waves and 2.5 percent to no-identified feature). 47 percent of CME-phenomena occurred near the heliospheric current sheet. Regarding the main-phase development all energy coupling functions showed a similar behavior, that is, the south component of the interplanetary magnetic field (in the magnetospheric coordinate frame) controls basically this coupling. The best linear fits were given by Ey electric field-like and epsilon electric power-like functions. However the complexities in these coupling relations point to other simultaneous energy transfer processes such as non-proportional transference, viscous transference, and 'unloading' process.

Mendes, Odim, Jr.

1992-08-01

315

Bounce-averaged diffusion coefficients due to resonant interaction of the outer radiation belt electrons with oblique chorus waves computed in a realistic magnetic field model  

NASA Astrophysics Data System (ADS)

We present the results of calculations of the bounce-averaged pitch angle, mixed, and momentum diffusion coefficients in a dipole and two realistic field models (the T01s model for quiet and storm conditions). We consider resonant interactions of the outer radiation belt electrons with oblique chorus waves. We demonstrate that on the dayside, the use of a realistic magnetic field versus a dipole field only makes a significant difference for small equatorial pitch angles at energies larger than E = 1 MeV. On the nightside, the differences between the scattering rates calculated in the Tsyganenko and dipole models can reach several orders of magnitude at various equatorial pitch angles for electrons with E ? 0.5 MeV. The most significant changes in the scattering rates computed in the realistic and dipole magnetic fields occur during the geomagnetically active conditions. On the nightside, for E ? 0.5 MeV, the diffusion coefficients calculated in the Tsyganenko field show significant scattering near the edge of the loss cone that can produce loss of electrons to the atmosphere, while in the dipole model there is no scattering at small equatorial pitch angles. Our computations in the realistic field show that resonant interactions between electrons with E ? 1 MeV and chorus waves can be an effective net loss mechanism on both the dayside and the nightside. To explain the differences in the scattering rates associated with a change in the magnetic field model, we present the contribution of various resonant harmonics to the diffusion and examine the changes in the resonance condition.

Orlova, Ksenia G.; Shprits, Yuri Y.; Ni, Binbin

2012-07-01

316

Second order average Hamiltonian theory of symmetry-based pulse schemes in the nuclear magnetic resonance of rotating solids: Application to triple-quantum dipolar recoupling  

NASA Astrophysics Data System (ADS)

The average Hamiltonian theory (AHT) of several classes of symmetry-based radio-frequency pulse sequences is developed to second order, allowing quantitative analyses of a wide range of recoupling and decoupling applications in magic-angle-spinning solid state nuclear magnetic resonance. General closed analytical expressions are presented for a cross term between any two interactions recoupled to second order AHT. We classify them into different categories and show that some properties of the recoupling pulse sequence may be predicted directly from this classification. These results are applied to examine a novel homonuclear recoupling strategy, effecting a second order average dipolar Hamiltonian comprising trilinear triple quantum (3Q) spin operators. We discuss general features and design principles of such 3Q recoupling sequences and demonstrate by numerical simulations and experiments that they provide more efficient excitation of 13C 3Q coherences compared to previous techniques. We passed up to 15% of the signal through a state of 3Q coherence in rotating powders of uniformly 13C-labeled alanine and tyrosine. Second order recoupling-based 13C homonuclear 3Q correlation spectroscopy is introduced and demonstrated on tyrosine.

Brinkmann, Andreas; Edén, Mattias

2004-06-01

317

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

2013-02-12

318

MHD simulation study of the interplanetary shocks under different conditions  

NASA Astrophysics Data System (ADS)

Simulation study of interplanetary shocks is important in order to describe dynamic process of their propagation and evolution during their passage through the Earth's magnetosphere as a whole in order to improve our observational knowledge of geospace. Our statistical analysis of a set of fast forward shocks shows that disturbance speed in the Earth's magnetosphere is higher than the original shock speed in the solar wind and differs according to the cone angle between the shock front normal in the solar wind and Sun-Earth line. Disturbance speed seems to be higher in all perpendicular cases than for oblique cases. For the purpose to describe this difference, GUMICS-4 global MHD simulation is used to calculate shock/disturbance propagation and evolution in different regions of the magnetosphere under different original conditions. Several methods are used to derive the propagation speeds and directions, such as Rankine-Hugoniot, velocity and magnetic coplanarity, and minimum variance analysis.

Andreeova, K.; Pulkkinen, T. I.; Juusola, L.; Palmroth, M. M.; Santolik, O.

2009-12-01

319

Comparison of YOHKOH x-ray coronal events with ULYSSES interplanetary events  

NASA Astrophysics Data System (ADS)

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.

1995-06-01

320

Heating of Plasmas in the Near-Earth Magnetotail by the Impact of an Interplanetary Shock  

NASA Astrophysics Data System (ADS)

It has been reported that radiation belt particles are rapidly energized by the impact of an interplanetary shock. In this study we report the observations by Cluster spacecraft that strong heating of plasmas occurs in the near-Earth magnetotail at ~-17 RE when an interplanetary shock impacts Earth's magnetosphere. On 24 August 2005 an interplanetary shock impacted Earth's magnetosphere and induced a storm sudden commencement (SSC) and magnetic storm. After the SSC both the density and temperature of plasmas in the near-Earth magnetotail significantly increased. The increases are more clearly seen in electrons than ions. Also, the particle fluxes of ions and electrons with E > ~30 keV increased more than an order of magnitude after the SSC. For ions significant flux enhancement was observed up to ~92.2 keV. On the other hand, for electrons the enhancement was observed up to ~127.5 keV. These results suggest that the heating is more efficient on electrons than ions. We will discuss about the physical mechanism responsible for the heating of plasmas in the magnetotail due to the impact of an interplanetary shock.

Lee, E.; Parks, G. K.; Wilber, M.; Lin, N.; Kim, K.; Lee, D.; SEON, J.; Jin, H.

2011-12-01

321

Solar and Interplanetary Causes of the Last Solar Cycle Deep Minimum in Geomagnetic Activity  

NASA Astrophysics Data System (ADS)

The recent solar cycle minimum (2008-2009) was extreme in several aspects, being the longest and deeper (low sunspot number) during the space era. Furthermore, the geomagnetic index ap showed its lowest value during the entire period of its record. The solar and interplanetary causes of this low geomagnetic activity were investigated. It was found that this period of minimum geomagnetic activity showed low values of interplanetary magnetic fields, solar wind speed, and the variance of the IMF Bz component. As a consequence, there was a minimum in energy transfer (epsilon parameter) from solar wind to the magnetosphere. The low IMF was caused by low solar magnetic fields, the low solar wind speed and low variances by the predominance of mid-latitude small coronal holes in this time of cycle, leading to solar wind streams from the edge of these holes to reach earth's orbit.

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

2011-12-01

322

Solar and interplanetary triggers of the largest Dst variations of the solar cycle 23  

NASA Astrophysics Data System (ADS)

We present the results of an investigation from the Sun to the Earth of the sequence of events that caused major Dst decreases (?Dst?-100 nT during 1 h) that occurred during 1996-2005. These events are expected to be better related to geomagnetic induced current (GIC) events than those events where any geomagnetic index is far from its quiet time value. At least one full halo CME with a speed on the plane of sky above 900 km/s participates in every studied event. The seven events were triggered by interplanetary signatures, which arise as a consequence of interaction among different solar ejections. The interaction arises at different stages from the solar surface, between segments of a filament, to the interplanetary medium, appearing as ejecta or multiple-magnetic clouds (MultiMCs). In other cases, shock waves overtake or compress previous ICMEs and at other times the interaction also appears between magnetic clouds (MCs) and streams.

Cerrato, Y.; Saiz, E.; Cid, C.; Gonzalez, W. D.; Palacios, J.

2012-05-01

323

Radio emission from the heliopause triggered by an interplanetary shock.  

PubMed

A strong heliospheric radio emission event has been detected by Voyagers 1 and 2 in the frequency range of 2 to 3 kilohertz. This event started in July 1992 and is believed to have been generated at or near the heliopause by an interplanetary shock that originated during a period of intense solar activity in late May and early June 1991. This shock produced large plasma disturbances and decreases in cosmic ray intensity at Earth, Pioneers 10 and 11, and Voyagers 1 and 2. The average propagation speed estimated from these effects is 600 to 800 kilometers per second. After correction for the expected decrease in the shock speed in the outer heliosphere, the distance to the heliopause is estimated to be between 116 and 177 astronomical units. PMID:17841865

Gurnett, D A; Kurth, W S; Allendorf, S C; Poynter, R L

1993-10-01

324

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

325

Interplanetary conditions leading to superintense geomagnetic storms (Dst ? ?250 nT) during solar cycle 23  

Microsoft Academic Search

The interplanetary causes of superintense geomagnetic storms (superstorms, Dst ? ?250 nT) that occurred during solar cycle 23 are studied. Eleven superstorms occurred during the cycle, five close to solar maximum (2000–2001) and six in the post-maximum\\/declining phase (2003–2004). About 1\\/3 of the superstorms were caused by magnetic clouds (MCs), 1\\/3 by a combination of sheath and MC fields, and

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

2008-01-01

326

Coronal transients and their interplanetary effects  

SciTech Connect

The role of coronal mass ejections in the context of solar-terrestrial physics is examined. Some of the necessary background material on flares and geomagnetic storms, on interplanetary shock waves, and on coronal mass ejections is described. One of the modern tools available for approaching these questions - theoretical models for the initiation and propagation of transient phenomenon in the solar corona is described. All of this material was extensively reviewed in the recent literature, and the coverage of it is both selective and somewhat abbreviated. The second of the tools - a new generation of coronagraph observation of mass ejections and complementary set of solar and interplanetary observations suitable for correlative studies, is described. Important problems to be solved in answering these questions and some suggested strategies for approaching these problems will be discussed.

Not Available

1984-06-01

327

Adiabatic Deceleration of Solar Energetic Particles as Deduced from Monte Carlo Simulations of Interplanetary Transport  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations of interplanetary transport are employed to study adiabatic energy losses of solar protons during propagation in the interplanetary medium. We consider four models. The first model is based on the diffusion-convection equation. Three other models employ the focused transport approach. In the focused transport models, we simulate elastic scattering in the local solar wind frame and magnetic focusing. We adopt three methods to treat scattering. In two models, we simulate a pitch-angle diffusion as successive isotropic or anisotropic small-angle scatterings. The third model treats large-angle scatterings as numerous small-chance isotropizations. The deduced intensity time profiles are compared with each other, with Monte Carlo solutions to the diffusion-convection equation, and with results of the finite-difference scheme by Ruffolo (1995). A numerical agreement of our Monte Carlo simulations with results of the finite-difference scheme is good. For the period shortly after the maximum intensity time, including deceleration can increase the decay rate of the near-Earth intensity essentially more than would be expected based on advection from higher momenta. We, however, find that the excess in the exponential-decay rate is time dependent. Being averaged over a reasonably long period, the decay rate of the near-Earth intensity turns out to be close to that expected based on diffusion, convection, and advection from higher momenta. We highlight a variance of the near-Earth energy which is not small in comparison with the energy lost. It leads to blurring of any fine details in the accelerated particle spectra. We study the impact of realistic spatial dependencies of the mean free path on adiabatic deceleration and on the near-Earth intensity magnitude. We find that this impact is essential whenever adiabatic deceleration itself is important. It is also found that the initial angular distribution of particles near the Sun can markedly affect MeV-proton energy losses and intensities observed at 1 AU. Computations invoked during the study are described in detail.

Kocharov, L.; Vainio, R.; Kovaltsov, G. A.; Torsti, J.

1998-09-01

328

Resonance glow of the neutral interplanetary gas  

NASA Astrophysics Data System (ADS)

The neutral hydrogen, embedded in the partially ionized local interstellar medium, can enter deeply into the heliosphere with the interstellar wind flow. While entering into the heliosphere it suffers from intense charge-exchange interactions with the solar wind protons. This charge-exchange leads to a fractional depletion of the interstellar hydrogen atoms inside the heliosphere and modulates their velocity and temperature distribution. The resulting thermodynamical conditions of the interstellar hydrogen inside the heliosphere are described by two kinetic density models. The first model by Wu & Judge specially takes into account the influence on hydrogen due to solar photo ionization and solar gravitation and leads to appropriate results in the solar vicinity. The second model by Osterbart & Fahr takes into account the plasma interaction effects near the solar wind shock region and near the heliopause. Hence, this model gives more realistic results for the hydrogen properties far away from the Sun. Besides these theoretical modelings of the interplanetary hydrogen, measurements of the interplanetary hydrogen HI-Lyman-Alpha resonance glow were performed and attempts have been made to deduce the relevant thermodynamical parameter of the neutral interstellar hydrogen by analyzing these glow data. Two radiation transport models will be discussed which are used to analyze the interplanetary hydrogen HI-Lyman-Alpha resonance glow data. First, the "optically thin" approximation which is used very often in the literature because of its simple numerical handling. Unfortunately, this model has a very limited region of validity. The second radiation transport model by Scherer & Fahr introduces the exact redistribution function which takes into account the local thermodynamical conditions of the scattering agent, like density, bulk velocity and temperature of the neutral interplanetary hydrogen. Also it takes into account the actually observed solar HI-Lyman-Alpha emission profile. Therefore it is a significant improvement with respect to the "optically thin" approximation but causes much more numerical efforts.

Scherer, Horst

2000-05-01

329

Interplanetary Scintillation Pushchino Survey II (Kopylov+, 2004)  

Microsoft Academic Search

We present the results of optical identification of 248 interplanetary scintillating (IPS) radio sources from the Pushchino Survey (PS) in the area of 0.11sr with the center at RA=10h28m, DE=+41{deg}. All 260 counterparts of IPS radio sources from the 7C and FIRST catalogues, which had been found in Paper I (Cat. ), were considered. We used USNO-B1.0 catalogue (limiting magnitude

A. I. Kopylov; V. S. Artyukh; F. G. Kopylova

2005-01-01

330

Interplanetary Shocks Lacking Type II Radio Bursts  

Microsoft Academic Search

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (~34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated

N. Gopalswamy; H. Xie; P. Mäkelä; S. Akiyama; S. Yashiro; M. L. Kaiser; J.-L. Bougeret

2010-01-01

331

Coronal mass ejections and interplanetary shocks  

Microsoft Academic Search

A comparison between Solwind observations of coronal mass ejections (CME's) and Helios 1 observations of interplanetary shocks during 1979-1982 indicates that 72 percent of the shocks were associated with large, low-latitude mass ejections on the nearby limb. Most of the associated CME's had speeds in excess of 500 km\\/s, but some of them had speeds in the range 200-400 km\\/s.

N. R. Sheeley Jr.; R. A. Howard; D. J. Michels; M. J. Koomen; R. Schwenn; K. H. Muehlhaeuser; H. Rosenbauer

1985-01-01

332

Interplanetary shock-induced current sheet disturbances leading to auroral activations: THEMIS observations  

NASA Astrophysics Data System (ADS)

We present a unique case of shock-generated tail current sheet (CS) disturbances measured by five THEMIS spacecraft in a tail-aligned configuration from -11 to -17 Re on 3 March 2009 when an interplanetary shock passed by the Earth. The spacecraft were ideally near the tail CS center. The IMF Bz was weakly southward with a 2 h average of -0.4 nT in the shock upstream. At 0602 UT when the shock impinged at the subsolar magnetopause, compressional waves were launched and propagated at a speed of ~2900 km s-1 into the tail. Their arrival presented a discontinuity in the magnetic field and plasma density around a THEMIS outer probe. Then, the CS thickness started decreasing and the tail reconnection rate started increasing. About 3-4 min later when the shock in the solar wind compressed the tail magnetopause at the down-tail location of the THEMIS spacecraft, the CS thinning became more significant and abrupt. Consequently, the CS thickness reduced by ~80% from ~16 × 103 to ~3 × 103 km in ~7 min X = -11 Re. At the same time, earthward fast flows and multiple dipolarization fronts were detected in the tail CS and auroral activity similar to a small substorm on the ground. We found that the tail CS and plasma sheet experienced a two-step evolution, which is attributed to the much faster propagation of compressional waves inside the magnetosphere than the shock in the solar wind. During the first step, the local magnetic field and plasma varied with low fluctuations. In the second step, the CS and plasma sheet became very disturbed with fast flows and significant waves presented. Observations also indicated that the magnetotail is not in pressure equilibrium during the shock compression.

Zhou, Xiaoyan; Zhou, Xu-Zhi; Angelopoulos, Vassilis; Shi, Quanqi; Wang, Chih-Ping; Frey, Harald

2013-06-01

333

Integrated shielding systems for manned interplanetary spaceflight  

NASA Astrophysics Data System (ADS)

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

George, Jeffrey A.

1992-01-01

334

GEOTAIL Observation of Interplanetary Shocks During the Solar Storm Season in October-November 2003  

NASA Astrophysics Data System (ADS)

Using GEOTAIL data, we study interplanetary shock (IPS) events and related phenomena in the solar storm season in 28 October - 6 November 2003. Four IPSs detected by GEOTAIL are, (1) ~02 UT on 28 October, (2) ~06 UT on 29 October, (3) ~06 UT on 4 November, and (4) ~20 UT on 6 November. (Another strong IPS detected by ACE at ~16 UT on 30 October came was not seen by GEOTAIL since GEOTAIL was in the magnetosphere.) While IPS-1 and IPS-4 were relatively weak shock, IPS-2 was the fastest shock (average speed of ~2200 km/s) ever detected by GEOTAIL. IPS03 was a moderately strong IPS with average speed of ~1100 km/s. From the viewpoint of nonthermal particle acceleration, we are most interested in IPS-2 and related phenomena. Unfortunately, since the background of SEPs (solar energetic particles) above 10 MeV during the IPS-2 event was fourth-strongest in the satellite record, the low energy ion detector LEP/EAi was masked for the most of the event. However, from other instruments including the low energy electron detector LEP/EAe, the solar wind ion detector LEP/SWi, energetic particle and ion composition EPIC, the magnetic field detector MGF, the plasma wave instrument PWI, the electric field instrument EFD we could obtain valuable data for this interesting IPS event. We will discuss (1) local shock properties (such as the shock angle, propagation speed, and compression ratio), (2) activity of waves resonating with energetic protons as well as energetic electrons, and (3) particle acceleration and possible `cosmic-ray-mediated' feature, namely preacceleration of the solar wind in the foreshock region ahead of the IPS.

Terasawa, T.; Oka, M.; Nakata, K.; Saito, Y.; Mukai, T.; Hayakawa, H.; Matsuoka, A.; Tsuruda, K.; Ishisaka, K.; Kasaba, Y.; Kojima, H.; Matsumoto, H.; Keika, K.; Nose, M.; McEntire, R. W.

2004-05-01

335

Sun-Earth Magnetic connection probed with radio bursts and magnetic field extrapolation  

Microsoft Academic Search

Energetic particles accelerated in the solar corona can be detected by spacecraft in interplanetary space provided there is either (i) a direct magnetic connection between the spacecraft and the acceleration region, or (ii) transport of particles across magnetic field lines in the corona or interplanetary space. We use type III radio bursts associated with locally produced Langmuir waves observed by

G. Lointier; K.-L. Klein; S. Hoang

2004-01-01

336

Interplanetary fast shocks and associated drivers observed through the 23rd solar minimum by Wind over its first 2.5 years  

NASA Astrophysics Data System (ADS)

A list of the interplanetary shocks observed by Wind from its launch (in Nov 1994) to May 1997 is presented. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using two techniques. These are: 1) a combination of the ``preaveraged'' magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, and 2) the Viñas and Scudder [1986] technique for solving the nonlinear least squares Rankine-Hugoniot equations. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. The mean strength and rate of occurrence of the shocks appear to correlate with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and the beginning of solar cycle 23. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The shock normal distribution showed a mean direction peaking in the ecliptic plane and with a longitude of ~200° (GSE coordinates). Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientations far off the ecliptic plane. No shock propagated with longitude ?n>=220+/-10°, i.e. against the average Parker spiral direction. Examination of the obliquity angle ?Bn (i.e., between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% were quasi-perpendicular, and about 32% of the shocks oblique, and the rest quasi-parallel. Small uncertainty in the estimated angle ?Bn was obtained for about 10 shocks with magnetosonic Mach numbers between 1 and 2.

Berdichevsky, Daniel B.; Szabo, Adam; Lepping, Ronald P.; Viñas, Adolfo F.; Mariani, Franco

2000-12-01

337

Interplanetary and geomagnetic consequences of 5 January 2005 CMEs associated with eruptive filaments  

NASA Astrophysics Data System (ADS)

On 5 January 2005, SoHO/LASCO observed the launch of two successive coronal mass ejections (CMEs) associated with the filament (active region and quiescent) structures. The eruptions resulted in two distinct magnetic clouds whose embedded flux-rope topology is modeled by the Grad-Shafranov (G-S) reconstruction technique. Filament plasma remnants in these magnetic clouds were identified using a combination of in situ plasma, magnetic, and composition signatures. In situ spacecraft (ACE and Wind) measurements suggest interaction between two magnetic clouds with complex magnetic structures at interface region separated by magnetic holes. These features impacted the Earth's terrestrial magnetosphere-ionosphere system and resulted in a moderate geomagnetic storm (peak Dst ?-96 nT). During the main phase of this storm on 7 January 2005, polarity reversals in the Y component (dawn to dusk) of interplanetary electric field triggered two major auroral substorms with concomitant changes in the polar ionospheric electric field. However, similar polarity reversal on 8 January 2005 during the recovery phase of the storm did not trigger any auroral substorm activity. The results provide clues for the interplanetary interaction of the two CMEs and its possible role in the development of the geomagnetic storm and substorms.

Sharma, Rahul; Srivastava, Nandita; Chakrabarty, D.; Möstl, Christian; Hu, Qiang

2013-07-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

339

Mineralogy of chondritic interplanetary dust particles  

NASA Astrophysics Data System (ADS)

This paper presents a synopsis of current investigations on the mineralogy of chondritic micrometeorites obtained from the lower stratosphere using flat-plate collection surfaces attached to high-flying aircraft. A compilation of detailed mineralogical analyses for 30 documented chondritic interplanetary dust particles indicates a wide variety of minerals present in assemblages which, as yet, are poorly defined. Two possible assemblages are: (1) carbonaceous phases and layer silicates and (2) carbonaceous and chain silicates or nesosilicates. Particles with both types of silicate assemblages are also observed.

MacKinnon, I. D. R.; Rietmeijer, F. J. M.

1987-08-01

340

Observations of magnetic helicity  

Microsoft Academic Search

The first observational signature of magnetic helicity in the solar atmosphere (sunspot whirls) was discovered 77 years ago. Since then, the existence of a cycle-invariant hemispheric helicity pattern has been firmly established through current helicity and morphological studies. During the last years, attempts were made to estimate\\/ measure magnetic helicity from solar and interplanetary observations. Magnetic helicity (unlike current helicity)

L. van Driel-Gesztelyi; P. Démoulin; C. H. Mandrini

2003-01-01

341

Solar Magnetic Field  

NASA Astrophysics Data System (ADS)

Electrical currents flowing in the solar plasma generate a magnetic field, which is detected in the SOLAR ATMOSPHERE by spectroscopic and polarization measurements (SOLAR MAGNETIC FIELD: INFERENCE BY POLARIMETRY). The SOLAR WIND carries the magnetic field into interplanetary space where it can be measured directly by instruments on space probes....

Schüssler, M.; Murdin, P.

2000-11-01

342

Simultaneous relativistic-electron and auroral-particle access to the polar caps during interplanetary magnetic field Bz northward: A scenario for an open-field line source of auroral particles  

Microsoft Academic Search

The large magnetic storm of February 1986 provides a unique opportunity to assess whether existing open-closed theories of the magnetosphere can consistently account for precipitating particle signatures measured at 840 km under a wide variety of solar wind and solar particle conditions. The simultaneous observation are prepared for relativistic electrons associated with a solar proton event and of auroral ions

M. S. Gussenhoven; E. G. Mullen

1989-01-01

343

Multi-Spacecraft Observations of Interplanetary Shock Parameters  

NASA Astrophysics Data System (ADS)

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

Koval, A.; Szabo, A.

2009-12-01

344

Multi-spacecraft observations of interplanetary shock parameters  

NASA Astrophysics Data System (ADS)

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

Koval, Andriy; Szabo, Adam

2010-05-01

345

Observations of electromagnetic whistler precursors at supercritical interplanetary shocks  

NASA Astrophysics Data System (ADS)

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 fci < f ? fce and wave numbers 0.02 ? k?ce ? 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. Although the precursors can have ?B/Bo 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, A.; Breneman, A.; Cattell, C. A.; Goetz, K.; Kellogg, P. J.; Kersten, K.; Kasper, J. C.; Maruca, B. A.; Pulupa, M.

2012-04-01

346

Detection of interplanetary activity using artificial neural networks  

NASA Astrophysics Data System (ADS)

Early detection of interplanetary activity is important when attempting to associate, with better accuracy, interplanetary phenomena with solar activity and geomagnetic disturbances. However, for a large number of interplanetary observations to be done every day, extensive data analysis is required, leading to a delay in the detection of transient interplanetary activity. In particular, the interplanetary scintillation (IPS) observations done with Ooty Radio Telescope (ORT) need extensive human effort to reduce the data and to model, often subjectively, the scintillation power spectra. We have implemented an artificial neural network (ANN) to detect interplanetary activity using the power spectrum scintillation. The ANN was trained to detect the disturbed power spectra, used as an indicator of the interplanetary activity, and to recognize normal and strong scattering spectra from a large data base of IPS spectra. The coincidence efficiency of classification by the network compared with the experts' judgement to detect the normal, disturbed and strong scattering spectra was found to be greater than 80 per cent. The neural network, when applied during the IPS mapping programme to provide early indication of interplanetary activity, would significantly help the ongoing efforts to predict geomagnetic disturbances.

Gothoskar, Pradeep; Khobragade, Shyam

1995-12-01

347

Delay-tolerant networking: an approach to interplanetary Internet  

Microsoft Academic Search

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

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

2003-01-01

348

A vacancy-disordered, oxygen-deficient perovskite with long-range magnetic ordering: local and average structures and magnetic properties of Sr2Fe1.5Cr0.5O5.  

PubMed

The local and average crystal structures and magnetic properties of the oxygen-deficient perovskite Sr(2)Fe(1.5)Cr(0.5)O(5+y) were studied using powder X-ray and neutron diffraction, neutron-pair distribution function analysis, and electron energy-loss spectroscopy. This material crystallizes in the cubic Pm3m space group, with a = 3.94491(14) Å. The oxygen vacancies are distributed randomly throughout the perovskite-type structure, and the average coordination number of the Fe(Cr) sites is 5. Refinement of the neutron diffraction data indicates y ? 0.05. This is in discordance with an earlier report on a material with the same nominal composition and cell constant. Electron energy-loss Cr L(2,3)-edge spectroscopy shows that Cr(3+) is present, which is also contrary to previous speculation. Neutron-pair distribution function studies show that a brownmillerite-like model involving ordered vacancies and alternating octahedral and tetrahedral coordination at the metal sites, gives a better description of the local structure out to ?5 Å. A remarkable phenomenon determined by neutron diffraction in Sr(2)Fe(1.5)Cr(0.5)O(5) is the occurrence of a long-range G-type antiferromagnetic ordering with T(c) ? 565 K because cubic oxygen-deficient perovskites with B-site disorder usually do not undergo transitions to magnetically ordered states. The observation of long-range antiferromagnetic order and the T(c) value are in accordance with previous Mössbauer spectroscopic studies. PMID:22288463

Ramezanipour, Farshid; Greedan, John E; Siewenie, Joan; Donaberger, Ronald L; Turner, Stuart; Botton, Gianluigi A

2012-01-30

349

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

350

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; W. D. Gonzalez; H. McCreadie; G. S. Lakhina; V. M. Vasyliunas

2008-01-01

351

Progress in the Study of Interplanetary Discontinuities  

SciTech Connect

This paper summarizes some of the recent rebirth of interest in interplanetary discontinuities. Vasquez et al. have developed a new method of searching for discontinuities that allows the study of structures with small angles of rotation. Those discontinuities are consistent with the in situ generation of discontinuities by Alfvenic turbulence. Borovsky has proposed that discontinuities with large rotation angles are the boundaries of flux tubes originating at the Sun. We conclude that both the Sun and turbulence are important sources of interplanetary discontinuities. We also argue that, at least in the slow solar wind, Tsurutani's in-situ generation by phase-steepened Alfven waves may be a manifestation of exhaust fan reconnection. We furthermore suggest that such reconnection may be responsible for the Walen ratio ([4pirho]{sup 1/2}|DELTAv|/|DELTAB|) across rotational discontinuities being less than the theoretically predicted value of unity. Whether or not the wind consists of discrete flux tubes rather than being simply discontinuous remains to be determined.

Neugebauer, Marcia; Giacalone, Joe [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

2010-03-25

352

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

SciTech Connect

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 ({Delta}{rho}V{sup 2}) may be associated with shocks, magnetic holes, or tangential discontinuities (TDs) in the interplanetary medium. The authors 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. Their theoretical analysis shows that the change in the plasma density across the interplanetary TD plays the most important role in the collision process. 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. The authors also simulate and discuss the interaction of a pair of tangential discontinuities, which may correspond to a magnetic hole, with the BS. 45 refs., 12 figs., 2 tabs.

Wu, B.H.; Mandt, M.E.; Lee, L.C. [and others

1993-12-01

353

Probable Cause of Interplanetary Field Enhancements: Destructive Collisions of Small Bodies  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) appear as smoothly varying cusp-shaped enhancements in the interplanetary magnetic field with a strong central current sheet. They last minutes to many hours. IFEs were attributed to dust released by asteroids and comets because of their appearance in association with conjunctions with asteroid 2201 Oljato. To maintain their magnetic field structure while at rest in the solar wind frame, IFEs must have significant mass because they do not have a flux rope geometry. We use the pressure gradient force to estimate the IFE mass using Helios (0.3-1.0AU) and ACE (1AU) data. We find the magnetic pressure difference falls as R-2 approximately from 0.3AU to 1AU, keeping the mass almost constant. At 1AU, the most frequent IFE mass is 10^8 kg and the rate decreases with both increasing and decreasing mass. We believe IFEs arise in interactions between solar wind and charged nanoscale dust particles produced in collisions of interplanetary objects. This hypothesis explains the large velocity achieved by IFEs, the macroscale magnetic field disturbances and the large mass contained in IFEs. In this paper we will use observed meteoroid population and collision models to calculate the inferred occurrence rate at 1AU and estimate the mass released by these collisions. By estimating the size of the disturbance produced by the collisions, we can relate the collision rate to the event rate detected by a spacecraft. The estimated meteoroid collision rate is found to be consistent with the IFE occurrence rate within the same mass range.

Lai, H.; Russell, C. T.; Delzanno, G. L.

2011-12-01

354

Interplanetary Propagation of Type-III Solar Radio Bursts Associated with Near-Relativistic Electron Events  

NASA Astrophysics Data System (ADS)

We have analyzed 125 interplanetary type III radio bursts detected between 25 KHz and 1 MHz by the WAVES/RAD1 experiment on Wind between 1997 and 2006. These events were selected for association with ACE/EPAM beam-like near-relativistic solar electron events. We have argued that these highly anisotropic near- relativistic electron events are well connected via the interplanetary magnetic field (IMF) to acceleration/release sites at the Sun. Consequently the associated type III events also should have good IMF connection to their release sites from the solar corona. We have made fits to the radius vs. time histories of the interplanetary type III bursts assuming that the solar wind electron density falls off inversely with radius squared. From linear fits to the leading edge of the high-resolution WAVES radio flux density, we found the apparent velocity (along an IMF spiral computed from the solar wind velocity at 1AU) of the leading edge of the type III bursts had a median value of 0.15c. We found that a significant fraction of the type III bursts were on field lines not passing directly through the Earth (confirmed by their emission frequencies remaining above the plasma frequency at Earth and the absence of associated <1keV low energy electrons). If we had assumed that the field lines containing the bursts had passed through the Earth, we would have deduced that the burst exciter was decelerating. However, once we allowed for that effect in our analysis, we found no evidence for interplanetary deceleration of the burst exciters. We then found that although ~75% of the bursts have an approximately constant speed, ~25% of the bursts were initially accelerating between the Sun and ~0.3 AU, consistent with a numerical simulation using statistical growth theory [Li et al, 2006].

Haggerty, D. K.; Roelof, E. C.

2008-05-01

355

Nearedge Absorption Spectroscopy of Interplanetary Dust Particles  

SciTech Connect

Interplanetary Dust Particles (IDPs) are derived from primitive Solar System bodies like asteroids and comets. Studies of IDPs provide a window onto the origins of the solar system and presolar interstellar environments. We are using Total Reflection X-ray Fluorescence (TXRF) techniques developed for the measurement of the cleanliness of silicon wafer surfaces to analyze these particles with high detection sensitivity. In addition to elemental analysis of the particles, we have collected X-ray Absorption Near-Edge spectra in a grazing incidence geometry at the Fe and Ni absorption edges for particles placed on a silicon wafer substrate. We find that the iron is dominated by Fe{sub 2}O{sub 3}.

Brennan, S.; Luening, K.; Pianetta, P.; Bradley, J.; Graham, G.; Westphal, A.; Snead, C.; Dominguez, G.; /SLAC, SSRL

2006-10-25

356

The Spanish Fireball Network: Popularizing Interplanetary Matter  

NASA Astrophysics Data System (ADS)

In order to increase in Spain the social interest in the study of interplanetary matter (asteroids, comets and meteoroids) we created the Spanish Photographic Meteor Network (SPMN) in 1997. This network has been dedicated to studying interplanetary matter with participation of researchers from three universities (Universitat Jaume I, Universitat de Barcelona and Universitat de València), the Institut d'Estudis Espacials de Catalunya (IEEC) and the Instituto de Astrofísica de Andalucía and it is also supported by the Atmospheric Sounding Station at El Arenosillo (INTA-CEDEA) and by the Experimental Station La Mayora (EELM-CSIC). In order to promote the participation of amateurs, our homepage (www.spmn.uji.es) presents public information about our research explains how amateur astronomers can participate in our network. In this paper we give some examples of the social role of a Fireball Network in order to give a coherent explanation to bright fireball events. Moreover, we also discuss the role of this kind of research project as a promoter of amateur participation and contribution to science. In fact, meteor astronomy can become an excellent area to form young researchers because systematic observation of meteors using photographic, video and CCD techniques has become one of the rare fields in astronomy in which amateurs can work together with professionals to make important contributions. We present here some results of the campaigns realized from the formation of the network. Finally, in a new step of development of our network, the all-sky CCD automatic cameras will be continuously detecting meteors and fireballs from four stations located in the Andalusia and Valencian communities by the end of 2005. Additionally, during important meteor showers we plan to develop fireball spectroscopy using medium field lenses.

Trigo-Rodríguez, J. M.; Castro-Tirado, A.; Llorca, J.; Fabregat, J.

357

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

358

Electromagnetic waves and electron anisotropies downstream of supercritical interplanetary shocks  

NASA Astrophysics Data System (ADS)

We present waveform observations of electromagnetic lower hybrid and whistler waves with fci ? f < fce downstream of four supercritical interplanetary shocks using the Wind search coil magnetometer. The whistler waves were observed to have a weak positive correlation between ?B and normalized heat flux magnitude and an inverse correlation with Teh/Tec. All were observed simultaneous with electron distributions satisfying the whistler heat flux instability threshold and most with T? h/T? h > 1.01. Thus, the whistler mode waves appear to be driven by a heat flux instability and cause perpendicular heating of the halo electrons. The lower hybrid waves show a much weaker correlation between ?B and normalized heat flux magnitude and are often observed near magnetic field gradients. A third type of event shows fluctuations consistent with a mixture of both lower hybrid and whistler mode waves. These results suggest that whistler waves may indeed be regulating the electron heat flux and the halo temperature anisotropy, which is important for theories and simulations of electron distribution evolution from the Sun to the Earth.

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

2013-01-01

359

Accretion of interplanetary dust by Ap and Am stars  

SciTech Connect

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. 35 references.

Kumar, C.K.; Davila, J.M.; Rajan, R.S. (Howard Univ., Washington, DC (USA); NASA, Goddard Space Flight Center, Greenbelt, MD (USA); California Institute of Technology, Pasadena (USA))

1989-02-01

360

Automated interplanetary shock detection and its application to Wind observations  

NASA Astrophysics Data System (ADS)

We present an automated two-step detection algorithm for identification of interplanetary (IP) shocks regardless their type in a real-time data stream. This algorithm is aimed for implementation on board the future Solar Orbiter mission for triggering the transmission of the high-resolution data to the Earth. The first step of the algorithm is based on a determination of a quality factor, Q indicating abrupt changes of plasma parameters (proton density and bulk velocity) and magnetic field strength. We test two sets of weighting coefficients for Q determination and propose the second step consisting of three additional constraints that increase the effectiveness of the algorithm. We checked the algorithm using Wind (at 1 AU) and Helios (at distances from 0.29 to 1 AU) data and compared obtained results with already existing lists of IP shocks. The efficiency of the presented algorithm for the Wind shock lists varies from 60% to 84% for two Q thresholds. The final shock candidate list provided by the presented algorithm contains the real IP shocks, as well as different discontinuities. The detection rate of the IP shocks equals to 64% and 29% for two Q thresholds. The algorithm detected all IP shocks associated with the solar wind transient structures triggering intense (Dst<-100 nT) geomagnetic storms.

Kruparova, O.; Maksimovic, M.; Å AfráNková, J.; N?Me?Ek, Z.; Santolik, O.; Krupar, V.

2013-08-01

361

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

362

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 Astrophysics Data System (ADS)

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

1993-04-01

363

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

NASA Astrophysics Data System (ADS)

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

Brändlein, Dirk; Lühr, Hermann; Ritter, Oliver

2012-11-01

364

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

365

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

SciTech Connect

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

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

1991-01-01

366

Effects of General Relativity on Interplanetary Time-Delay Measurements.  

National Technical Information Service (NTIS)

The predictions of general relativity regarding interplanetary time-delay measurements are explored in detail. We conclude that a fourth test of the theory is now feasible since the modifications of general relativity introduce on extra delay of about 200...

I. I. Shapiro

1964-01-01

367

Charging kinetics of dust in interplanetary space plasma  

NASA Astrophysics Data System (ADS)

A theoretical kinetic model for the physical understanding of the charging of dust particles in the interplanetary space plasma has been developed. In contrast to earlier studies, the present analysis incorporates (i) uniform potential theory for complex plasmas with size distribution of the dust particles, (ii) charge, number and energy balance of the constituents and (iii) appropriate expressions for photoelectric emission from a positively charged particle with inherent charge neutrality of the interplanetary space plasma. Further utilizing the population balance equation (given by Matsoukas and Russel) for the interplanetary dust particles, the fluctuations in steady-state charge (or electric potential) has also been investigated. For the illustration purpose, the computations have been performed for the interplanetary space plasma at 1 au from the sun; for this distance, reasonably good information on the gaseous and dust components are available. As an interesting feature, the theoretical predictions are in reasonably good agreement with observations and earlier estimates.

Misra, Shikha; Mishra, S. K.

2013-07-01

368

Interplanetary Sample Return Missions Using Radioisotope Electric Propulsion.  

National Technical Information Service (NTIS)

Solar electric propulsion (SEP) is being used for a variety of planetary missions sponsored by ESA, JAXA, and NASA and nuclear electric propulsion (NEP) is being considered for future, flagship-class interplanetary missions. Radioisotope electric propulsi...

R. Williams Y. Gao C. A. Kluever M. Cupples J. Belcher

2005-01-01

369

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

Microsoft Academic Search

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

R. P. Kane

2005-01-01

370

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

371

Inferring interplanetary flux rope orientation with the minimum residue method  

NASA Astrophysics Data System (ADS)

There are many 2-D models that can be used to describe the structure of the interplanetary flux rope (IFR), such as the force-free model, the nonforce-free model, and the inertial model. For each model, one or multiple field line invariants exist. In this study, we introduce a new definition of the quantity, residue, based on all field line invariants of a specified flux rope model to measure the deflection between the assumed axis and the true flux rope axis. Then, a new minimum residue (MR) method is proposed to infer the axial orientation of IFR with the observational data from a single spacecraft. For an arbitrarily assumed flux rope axis, the natural coordinate system can be constructed, then a magnetic flux function, A, and each invariant of the specified flux rope model can also be concurrently calculated under this coordinate system. The direction corresponding to the minimum residue is expected to be the real axial orientation. In previous study, the residue was first defined with A and a single invariant P t of a static equilibrium flux rope model. Here, the new MR method is tested with simulated magnetic cloud data sets constructed from the analytical model outputs of two different flux rope models with ``trend noise'' added. It shows that the new MR method is applicable in real case analysis and the inferring results are acceptable for cases with small closest approach distance and proper noise level. Compared with results from traditional methods, accuracy of the inferred axial orientation is improved by the new method. The new MR method is also applied to a typical in situ event observed by Wind spacecraft. The comparison of the inferring results from different models indicate that application of a more accurate flux rope model is useful for inferring techniques.

Li, H. J.; Feng, X. S.; Zuo, P. B.; Xie, Y. Q.

2009-03-01

372

A Test of Cosmic Ray Interplanetary Transport Theory  

Microsoft Academic Search

The daughter protons of the energetic neutrons (10-200MeV) produced in the June 3 1982 solar flare are noted as excellent particles for testing cosmic ray interplanetary transport theory. The long-standing discrepancy of about an order of magnitude between theory and observation concerning the cosmic ray transport mean free path in the interplanetary space is also reviewed to show the need

Liwei Dennis Zhang

1994-01-01

373

Energetic interplanetary shocks, radio emission, and coronal mass ejections  

Microsoft Academic Search

The interplanetary shocks which generate detectable low-frequency (<1 MHz) radio emission, represent as a group, the most energetic shocks produced by the sun. For all interplanetary (IP) shocks which generated so-called IP type II events, the authors find, when observations were available, that the associated solar events involved fast (> 500 km\\/s) coronal mass ejections (CMEs). In comparison with the

H. V. Cane; N. R. Jr. Sheeley; R. A. Howard

1987-01-01

374

Statistical Analysis of Energetic Electrons (3.4-16 MeV) at Geosynchronous Altitude and Their Relationship to Interplanetary Parameters.  

National Technical Information Service (NTIS)

This analysis attempted to examine the relationship between energetic electrons in the magnetosphere between the energy levels of 3.4-16 MeV, solar wind speed, and the Bz component of the Interplanetary Magnetic Field (IMF). The statistical analysis was a...

W. L. Smith

1983-01-01

375

Global Magnetospheric Response to an Interplanetary Shock: THEMIS Observations  

NASA Astrophysics Data System (ADS)

We investigate the global response of the geospace plasma environment to an interplanetary shock at ~0224 UT on May 28, 2008 from multiple THEMIS spacecraft observations in the magnetosheath (THEMIS B and C), the mid-afternoon (THEMIS A), and the dusk magnetosphere (THEMIS D and E). The interaction of the transmitted interplanetary shock with the magnetosphere has global effects. Consequently, it can affect geospace plasma significantly. After interacting with the bow shock, the interplanetary shock transmitted a fast shock and a discontinuity which propagated through the magnetosheath toward the Earth at speeds of 300 km/s and 137 km/s respectively. THEMIS A observations indicate that the interplanetary shock changed the properties of the plasmaspheric plume significantly. The plasmaspheric plume density increased rapidly from 10 to 100 cm-3 in 4 min and the ion distribution changed from an isotropic to a strongly anisotropic distribution. Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are most likely excited by the anisotropic ion distributions caused by the interplanetary shock impact. We show that the arrival of the interplanetary shock energize the plue population, resulting in strongly anisotropic particle distributions. THEMIS A, but not D or E, observed a plasmaspheric plume in the dayside magnetosphere. Multiple spacecraft observations indicate that the dawn-side edge of the plasmaspheric plume was located between THEMIS A and D (or E).

Zhang, H.; Sibeck, D. G.; Zong, Q.; McFadden, J. P.; Larson, D. E.; Glassmeier, K.; Angelopoulos, V.

2011-12-01

376

Specific interplanetary conditions for CIR-, Sheath-, and ICME-induced geomagnetic storms obtained by double superposed epoch analysis  

NASA Astrophysics Data System (ADS)

A comparison of specific interplanetary conditions for 798 magnetic storms with Dst <-50 nT during 1976-2000 was made on the basis of the OMNI archive data. We categorized various large-scale types of solar wind as interplanetary drivers of storms: corotating interaction region (CIR), Sheath, interplanetary CME (ICME) including both magnetic cloud (MC) and Ejecta, separately MC and Ejecta, and "Indeterminate" type. The data processing was carried out by the method of double superposed epoch analysis which uses two reference times (onset of storm and minimum of Dst index) and makes a re-scaling of the main phase of the storm in a such way that all storms have equal durations of the main phase in the new time reference frame. This method reproduced some well-known results and allowed us to obtain some new results. Specifically, obtained results demonstrate that (1) in accordance with "output/input" criteria the highest efficiency in generation of magnetic storms is observed for Sheath and the lowest one for MC, and (2) there are significant differences in the properties of MC and Ejecta and in their efficiencies.

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

2010-12-01

377

SIMONE: interplanetary microsatellites for NEO rendezvous missions  

NASA Astrophysics Data System (ADS)

The paper summarises a novel mission concept called SIMONE (Smallsat Intercept Missions to Objects Near Earth), whereby a fleet of microsatellites may be deployed to individually rendezvous with a number of Near Earth Objects (NEOs), at very low cost. The mission enables, for the first time, the diverse properties of a range of spectral and physical type NEOs to be determined. Such data are invaluable to the scientific study, impact damage prediction, and impact countermeasure planning of NEOs. The five identical 120kg spacecraft are designed for low-cost piggyback launch on Ariane-5 into GTO, from where each uses a gridded-ion engine to escape the Earth and ultimately to rendezvous with a different NEO target. The primary challenge with such a mission is the ability to accommodate the necessary electric propulsion, power, payload and other onboard systems within the constraints of a microsatellite. The paper describes the way in which the latest technological advancements have been selected and applied to the mission design. The SIMONE design is feasible and clearly demonstrates that the concept of an "interplanetary microsatellite" is now realisable.

Wells, Nigel; Walker, Roger; Green, Simon; Ball, Andrew

2003-11-01

378

SIMONE: Interplanetary microsatellites for NEO rendezvous missions  

NASA Astrophysics Data System (ADS)

The paper summarises a novel mission concept called SIMONE (smallsat intercept missions to objects near Earth), whereby a fleet of microsatellites may be deployed to individually rendezvous with a number of near Earth objects (NEOs), at very low cost. The mission enables, for the first time, the diverse properties of a range of spectral and physical type NEOs to be determined. Such data are invaluable to the scientific study, impact damage prediction, and impact countermeasure planning of NEOs. The five identical 120 kg spacecraft are designed for low-cost piggyback launch on Ariane-5 into GTO, from where each uses a gridded-ion engine to escape the Earth and ultimately to rendezvous with a different NEO target. The primary challenge with such a mission is the ability to accommodate the necessary electric propulsion, power, payload and other on-board systems within the constraints of a microsatellite. The paper describes the way in which the latest technological advancements have been selected and applied to the mission design. The SIMONE design is feasible and clearly demonstrates that the concept of an "interplanetary microsatellite" is now realisable.

Wells, Nigel; Walker, Roger; Green, Simon; Ball, Andrew

2006-10-01

379

On fragmentation of meteoroids in interplanetary space  

NASA Astrophysics Data System (ADS)

A possible fragmentation of meteoroids in interplanetary space inferred from grouping of particles in meteor streams is discussed. There is a conviction maintained by many observers that meteors within the streams are observed to be clustered in pairs or larger groups more frequently than one could expect from random distribution. The rate of dispersive effects indicates that the lifetime of any such a group of meteoroids is very limited. Therefore, if real, the pairs or groups must be due to recent fragmentation of larger meteoroids. Analyses based on visual observations of meteor streams lead to contradictory results. More conclusive are analyses based on radio measurements, which present a negative result concerning the permanent meteor showers with the stream structures at their middle and late evolutionary stages, and an indication of a positive result for younger dense stream structures of recent origin. Analysis of the 1969 Leonid display obtained by the Springhill high-power radar shows that about 10% of the population around the shower maximum is associated in close groups, within a distance up to of about 10 km and confined to an effective stream width comparable to the diameter of the Earth. The recent Leonid returns with the storm in 1999 provided a possibility to verify a non-random grouping of particles within this young filament of the stream. The analysis and results based on TV observations of the storm are presented and discussed.

Porub?an, V.; Tóth, J.; Yano, H.

2002-10-01

380

Radioisotopic heater units warm an interplanetary spacecraft  

SciTech Connect

The Cassini orbiter and Huygens probe, which were successfully launched on October 15, 1997, constitute NASA`s last grand-scale interplanetary mission of this century. The mission, which consists of a four-year, close-up study of Saturn and its moons, begins in July 2004 with Cassini`s 60 orbits of Saturn and about 33 fly-bys of the large moon Titan. The Huygens probe will descend and land on Titan. Investigations will include Saturn`s atmosphere, its rings and its magnetosphere. The atmosphere and surface of Titan and other icy moons also will be characterized. Because of the great distance of Saturn from the sun, some of the instruments and equipment on both the orbiter and the probe require external heaters to maintain their temperature within normal operating ranges. These requirements are met by Light Weight Radioisotope Heater Units (LWRHUs) designed, fabricated and safety tested at Los Alamos National Laboratory, New Mexico. An improved gas tungsten arc welding procedure lowered costs and decreased processing time for heat units for the Cassini spacecraft.

Franco-Ferreira, E.A. [Oak Ridge National Lab., TN (United States). Engineering Technology Div.; Rinehart, G.H. [Los Alamos National Lab., NM (United States)

1998-01-01

381

Magnetism on earth and in space  

NASA Astrophysics Data System (ADS)

The general characteristics of the phenomenon of magnetism are described. Attention is given to the magnetic properties of elementary particles, atoms, weak magnetic (diamagnetic and paramagnetic) and strong magnetic (magnetically ordered) substances. The question of magnetism in living organisms is considered, and examples of several recent industrial applications of magnetism and electromagnetism are presented. Information is presented on the magnetism of objects in space including the planets, the earth, the sun, stars, interplanetary and interstellar media and galaxies. Several illustrations are provided.

Belov, K. P.; Bochkarev, N. G.

382

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

383

STEREO observations of suprathermal electron distributions and the solar cycle variation of the interplanetary field  

NASA Astrophysics Data System (ADS)

STEREO SWEA provides the opportunity to observe solar wind halo electron heat fluxes and strahl over 4pi steradians at locations free of Earth bow shock contamination. After 4+ years of observations, and with the onset of solar cycle 24, we can begin to take a detailed look at the pitch angle distributions related to coronal transients impactng the interplanetary flux budget. Of primary interest are the conditions that lead to hour-scale, strong electron heat fluxes pointed back toward the Sun and counterstreaming or bi-directional electrons. Both of these phenomena have been associated with dynamical reconfigurations of the coronal fields, and in the case of counterstreaming, with the addition of magnetic flux to the heliosphere. We reconsider the different types of behavior known to be present in and around ICMEs from previous studies. Our analyses suggest how ICMEs enable the observed cycle variation in the interplanetary field strength. In particular, we show how counterstreaming can correspond to both the opening and closing of magnetic flux rooted at the Sun when other source(s) of suprathermals are considered.

Ellenburg, M. A.; Luhmann, J. G.; Schroeder, P. C.; Opitz, A.; Lavraud, B.; Sauvaud, J.; Jian, L.; Russell, C. T.; Simunac, K.; Galvin, A. B.

2011-12-01

384

Hybrid modelling the Pioneer Venus Orbiter magnetic field observations  

Microsoft Academic Search

This study presents comparisons between the Pioneer Venus Orbiter (PVO) magnetometer (OMAG) observations and the HYB-Venus hybrid simulation code. The comparisons are made near periapsides of four PVO orbits using the full resolution PVO\\/OMAG data. Also, the statistics of the solar wind and interplanetary magnetic field (IMF) conditions at Venus are studied using the PVO interplanetary dataset. The statistics include

R. Jarvinen; E. Kallio; I. Sillanpää; P. Janhunen

2008-01-01

385

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

386

A doubling of the Sun's coronal magnetic field during the past 100 years  

Microsoft Academic Search

The solar wind is an extended ionized gas of very high electrical conductivity, and therefore drags some magnetic flux out of the Sun to fill the heliosphere with a weak interplanetary magnetic field,. Magnetic reconnection-the merging of oppositely directed magnetic fields-between the interplanetary field and the Earth's magnetic field allows energy from the solar wind to enter the near-Earth environment.

M. Lockwood; R. Stamper; M. N. Wild

1999-01-01

387

Solar and Interplanetary Origins of Great Geomagnetic Storms in the Falling Phase of Current Solar Cycle 2  

NASA Astrophysics Data System (ADS)

The interplanetary causes of great magnetic storms peak Dst le -200 nT and intense magnetic storms -100 nT ge Dst ge -200 nT observed during the fall and maximum of solar cycle 23 2001-2004 have been studied by using the data from SPDF - OMNIWeb Public Data Service available at http omniweb gsfc nasa gov Seven great and twenty-four intense magnetic storms occurred during this period The four great magnetic storms that occurred on 31 March 01 Dst -387nT 11 April 01 Dst -271nT 20 November 03 Dst -472nT and 07 November 04 Dst -373nT and twenty three intense storms for which sufficient interplanetary data are available have been selected In general different sets of solar wind parameters such as solar wind velocity v p solar wind thermal speed V th solar wind ion density N ion dynamic pressure nPa solar wind electric field E y and interplanetary Magnetic Field IMF magnitude B and southward component B S of IMF are associated with the storms of these categories The great storm of 20 Nov 01 was associated with single magnetic cloud plasma beta approx 0 1 and other three with multi-clouds MCs The value of B S varied from -25nT to -55nT with the duration between 10-18 hrs The B s was the major part of B 70-100 during the main phase of great storms All fours storms evolved through single-step development in the ring current Out of 23 intense storms 16 storms were associated

Sushil, Kumar

388

Geomagnetic activity for northward interplanetary magnetic fields: Am index response  

SciTech Connect

The Am index is used to study the response of the magnetosphere to northward IMF. It is shown that most of the observed increase in activity can be explained by a correlation of the solar wind dynamic pressure with the IMF field strength such that the Am index varies only slightly with northward IMF strength when the solar wind dynamic pressure is held constant. There remains a smaller response of Am to solar wind velocity, which is usually attributed to a viscous interaction of the solar wind with the magnetosphere such as through the Kelvin-Helmholtz instability. The diurnal variation of Am during northward fields is also examined. A model invoking the Kelvin-Helmholtz instability on the flanks of the magnetopause have been used to predict the annual behavior of this diurnal variation. The predicted annual behavior is not found for northward IMF. The difference in diurnal variation from summer months to winter months, suggested to be caused solely by the Kelvin-Helmholtz instability, appears only for southward fields.

Scurry, L.; Russell, C.T. (Univ. of California, Los Angeles (USA))

1990-07-01

389

Very low strengths of interplanetary meteoroids and small asteroids  

NASA Astrophysics Data System (ADS)

We have assembled data on 13 cases of meteorite falls with accurate tracking data on atmospheric passage. In all cases, we estimate the bulk strength of the object corresponding to its earliest observed or inferred fragmentation in the high atmosphere, and can compare these values with measured strengths of meteorites in the taxonomic class for that fall. In all 13 cases, the strength corresponding to earliest observed or inferred fragmentation is much less than the compressive or tensile strength reported for that class of stony meteorites. Bulk strengths upon atmospheric entry of these bodies are shown to be very low, 0.1 to approximately 1 MPa on first breakup, and maximal strength on breakup as 1-10 MPa corresponding to weak and “crumbly” objects, whereas measured average tensile strength of the similar meteorite classes is about 30 MPa. We find a more random relation between bulk sample strength and sample mass than is suggested by a commonly used empirical power law. We estimate bulk strengths on entry being characteristically of the order of 10-1-10-2 times the tensile strengths of recovered samples. We conclude that pre-entry, meter-scale interplanetary meteoroids are typically highly fractured or in some cases rubbly in texture, presumably as a result of their parent bodies' collisional history, and can break up under stresses of a few megapascals. The weakness of some carbonaceous objects may result from very porous primordial accretional structures, more than fractures. These conclusions have implications for future asteroid missions, sample extraction, and asteroid hazard mitigation.

Popova, Olga; Borovi?ka, Ji?í; Hartmann, William K.; Spurný, Pavel; Gnos, Edwin; Nemtchinov, Ivan; Trigo-Rodríguez, Josep M.

2011-10-01

390

Towards a Solar Cycle Average Model for Heliospheric Irradiation of Small Icy Bodies in the Outer Solar System  

NASA Astrophysics Data System (ADS)

Abundant data are available from operational interplanetary spacecraft to construct model flux spectra and dosage profiles for irradiation of icy bodies including Centaurs, Kuiper Belt Objects, and Oort Cloud comets by ions at plasma to cosmic ray energies. Data sources include the Advanced Composition Explorer (ACE) and other spacecraft in interplanetary space near Earth, the Ulysses spacecraft in an eccentric six-year polar orbit around the Sun, and the two Voyager spacecraft now moving through the outer Solar System towards the boundaries of the heliosphere. For applications to irradiation of solar system objects there is a need to compile flux averages of past and future data extending over the 11-year solar activity cycle, and the 22-year solar magnetic cycle, as approximations to irradiation over much longer periods of time. Heliospheric plasma and cosmic ray transport models can be used to extrapolate from multiple spacecraft observation points to heliocentric orbits of specific bodies at given phases of these cycles. In this report we focus on interstellar pickup ions accelerated from initial plasma (eV - keV) energies up to 100 MeV/nucleon at the solar wind termination shock, thought to be located at 90 - 100 AU from the Sun, and propagated by diffusion and gradient-curvature drifts throughout the heliosphere. These ions show large changes in intensity and spatial gradients during both cycles, while being very important for surface irradiation of small bodies in the outer solar system. Overall positive radial gradients are predicted for ACR ion intensities averaged over 22 years at orbits of Centaurs and KBOs, possibly contributing to perihelion and eccentricity gradients in visible color of the Classical KBO population. Compression of heliospheric boundaries inward in response to increasing density of local interstellar gas could occasionally expose these objects to stronger radial gradients and higher irradiation dosages over billions of years.

Cooper, J. F.; Cummings, A. C.; Mewaldt, R. A.; Richardson, J. D.; Wang, C.; Johnson, R. E.

2003-05-01

391

An orbit averaged particle code  

Microsoft Academic Search

A new method for efficient computer simulation of long time-scale plasma physics phenomena is proposed which has proved successful in one- and two-dimensional magneto-inductive particle codes. The method relies on orbit-averaging charge and current densities in Maxwell's equations before solving for the self-consistent electric and magnetic fields in order to filter out unwanted high-frequency oscillations and reduce the number of

B. I. Cohen; T. A. Brengle; D. B. Conley; R. P. Freis

1980-01-01

392

Carbon Abundances, Major Element Chemistry, and Mineralogy of Hydrated Interplanetary Dust Particles.  

National Technical Information Service (NTIS)

Hydrated interplanetary dust particles (IDP's) comprise a major fraction of the interplanetary dust particles collected in the stratosphere. While much is known about the mineralogy and chemistry of hydrated IDP's, little is known about the C abundance in...

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

1993-01-01

393

Small comets - Implications for interplanetary Lyman-alpha  

NASA Astrophysics Data System (ADS)

It is noted that, due to the large amounts of hydrogen that would be generated in interplanetary space by the numerous small comets proposed by Frank et al. (1986), inhibition of water vapor by a factor of 3 x 10 to the -9th by very thick dust mantles would be necessary to prevent excitation of a detectable interplanetary Lyman-alpha glow. A forbiddingly large influx of dust would result from these cometesimals, with a carbon influx 350 times larger than the rate of burial of fresh carbon in sediments. Other optical problems associated with these cometesimals are considered.

Donahue, T. M.

1987-03-01

394

Reflectance spectroscopy of interplanetary dust particles  

NASA Astrophysics Data System (ADS)

Reflectance spectra were collected from chondritic interplanetary dust particles (IDPs), a polar micrometeorite, Allende (CV3) meteorite matrix, and mineral standards using a microscope spectrophotometer. Data were acquired over the 380-1100 nm wavelength range in darkfield mode using a halogen light source, particle aperturing diaphrams, and photomultiplier tube (PMT) detectors. Spectra collected from titanium oxide (Ti4O7), magnetite (Fe3O4), and Allende matrix establish that it is possible to measure indigenous reflectivities of micrometer-sized (>5 ?m in diameter) particles over the visible (VIS) wavelength range 450-800 nm. Below 450 nm, small particle effects cause a fall-off in signal into the ultraviolet (UV). Near-infrared (IR) spectra collected from olivine and pyroxene standards suggest that the ˜1 ?m absorption features of Fe-bearing silicates in IDPs can be detected using microscope spectrophotometry. Chondritic IDPs are dark objects (<15% reflectivity) over the VIS 450-800 nm range. Large (>1 ?m in diameter) embedded and adhering single mineral grains make IDPs significantly brighter, while surficial magnetite formed by frictional heating during atmospheric entry makes them darker. Most chondritic smooth (CS) IDPs, dominated by hydrated layer silicates, exhibit generally flat spectra with slight fall-off towards 800 nm, which is similar to type CI and CM meteorites and main-belt C-type asteroids. Most chondritic porous (CP) IDPs, dominated by anhydrous silicates (pyroxene and olivine), exhibit generally flat spectra with a slight rise towards 800 nm, which is similar to outer P and D asteroids. The most C-rich CP IDPs rise steeply towards 800 nm with a redness comparable to that of the outer asteroid object Pholus (Binzel, 1992). Chondritic porous IDPs are the first identified class of meteoritic materials exhibiting spectral reflectivities (between 450 and 800 nm) similar to those of P and D asteroids. Although large mineral grains, secondary magnetite, and small particle effects complicate interpretation of IDP reflectance spectra, microscope spectrophotometry appears to offer a rapid, nondestructive technique for probing the mineralogy of IDPs, comparing them with meteorites, investigating their parent body origins, and identifying IDPs that may have been strongly heated during atmospheric entry.

Bradley, J. P.; Keller, L. P.; Brownlee, D. E.; Thomas, K. L.

1996-05-01

395

The extreme magnetic storm of 1-2 September 1859  

Microsoft Academic Search

The 1-2 September 1859 magnetic storm was the most intense in recorded history on the basis of previously reported ground observations and on newly reduced ground-based magnetic field data. Using empirical results on the interplanetary magnetic field strengths of magnetic clouds versus velocities, we show that the 1 September 1859 Carrington solar flare most likely had an associated intense magnetic

B. T. Tsurutani; W. D. Gonzalez; G. S. Lakhina; S. Alex

2003-01-01

396

The extreme magnetic storm of 1–2 September 1859  

Microsoft Academic Search

The 1–2 September 1859 magnetic storm was the most intense in recorded history on the basis of previously reported ground observations and on newly reduced ground-based magnetic field data. Using empirical results on the interplanetary magnetic field strengths of magnetic clouds versus velocities, we show that the 1 September 1859 Carrington solar flare most likely had an associated intense magnetic

B. T. Tsurutani; W. D. Gonzalez; G. S. Lakhina; S. Alex

2003-01-01

397

COMPOSITION STRUCTURE OF INTERPLANETARY CORONAL MASS EJECTIONS FROM MULTISPACECRAFT OBSERVATIONS, MODELING, AND COMPARISON WITH NUMERICAL SIMULATIONS  

SciTech Connect

We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections (ICMEs) observed on 2007 May 21-23 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation coronal mass ejection (CME) initiation. We use these advances to interpret specific features of the ICME plasma composition resulting from the magnetic topology and evolution of the CME. We find that, in both the data and our MHD simulations, the flux ropes centers are relatively cool, while charge state enhancements surround and trail the flux ropes. The magnetic orientations of the ICMEs are suggestive of magnetic breakout-like reconnection during the eruption process, which could explain the spatial location of the observed iron enhancements just outside the traditional flux rope magnetic signatures and between the two ICMEs. Detailed comparisons between the simulations and data were more complicated, but a sharp increase in high iron charge states in the ACE and STEREO-A data during the second flux rope corresponds well to similar features in the flux cancellation results. We discuss the prospects of this integrated in situ data analysis and modeling approach to advancing our understanding of the unified CME-to-ICME evolution.

Reinard, Alysha A. [University of Colorado/Cooperative Institute for Research in Environmental Sciences and National Oceanic and Atmospheric Administration/Space Weather Prediction Center, Boulder, CO 80505 (United States); Lynch, Benjamin J. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Mulligan, Tamitha, E-mail: alysha.reinard@noaa.gov, E-mail: blynch@ssl.berkeley.edu, E-mail: tamitha.mulligan@aero.org [Space Sciences Department, Aerospace Corporation, Los Angeles, CA 90009 (United States)

2012-12-20

398

Composition Structure of Interplanetary Coronal Mass Ejections From Multispacecraft Observations, Modeling, and Comparison with Numerical Simulations  

NASA Astrophysics Data System (ADS)

We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections (ICMEs) observed on 2007 May 21-23 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation coronal mass ejection (CME) initiation. We use these advances to interpret specific features of the ICME plasma composition resulting from the magnetic topology and evolution of the CME. We find that, in both the data and our MHD simulations, the flux ropes centers are relatively cool, while charge state enhancements surround and trail the flux ropes. The magnetic orientations of the ICMEs are suggestive of magnetic breakout-like reconnection during the eruption process, which could explain the spatial location of the observed iron enhancements just outside the traditional flux rope magnetic signatures and between the two ICMEs. Detailed comparisons between the simulations and data were more complicated, but a sharp increase in high iron charge states in the ACE and STEREO-A data during the second flux rope corresponds well to similar features in the flux cancellation results. We discuss the prospects of this integrated in situ data analysis and modeling approach to advancing our understanding of the unified CME-to-ICME evolution.

Reinard, Alysha A.; Lynch, Benjamin J.; Mulligan, Tamitha

2012-12-01

399

Solar Wind Slowdown Due to Dust Pickup during Interplanetary Field Enhancements  

NASA Astrophysics Data System (ADS)

The interplanetary field enhancements (IFEs) are characterized by their cusp-shaped enhancement in the magnetic field magnitude. They are observed throughout the inner solar system from 0.72AU by Pioneer Venus Orbiter to 5AU by Ulysses. The annual IFE rate is ten at 0.72AU and around eight at 1AU, i.e., decreases as the heliocentric distance increases. Multiple-spacecraft observations show that IFEs are moving radially away from the Sun at nearly the ambient solar wind speed. During the IFE events, case studies show that while there are correlated diamagnetic compensations in pressure there are no significant correlated changes in the solar wind speed. An IFE formation mechanism that explains most of the IFE features is that IFEs result from interactions between solar wind and clouds of picked up nanoscale charged dust, which is released in interplanetary collisions between objects of 10 to 1000m in diameter. The enhanced magnetic field behaves as a magnetic barrier that can transfer momentum to the charged dust from the solar wind. Momentum lifts the dust outward in the solar gravitational well. A prediction of this hypothesis is that solar wind will be slowed down even when the IFEs have reached exactly the solar wind speed. To test this hypothesis, we perform a superposed analysis on the radial velocity of IFEs observed at 1AU. In contrast to the case studies, the statistical results have a significant change in speed. The velocity on the solar wind side of the IFEs is smaller than the ambient velocity. This slowdown increases for larger IFEs with larger estimated mass. In addition, the amount of momentum due to the solar wind slowdown is quantitatively consistent with the momentum expected to be needed to lift the dust out of the Sun's gravitational potential well, which is in strong support of our IFE formation mechanism.

Lai, Hairong; Russell, Christopher; Wei, Hanying

2013-04-01

400

The plasma-wave experiment on the VEGA interplanetary probes  

NASA Astrophysics Data System (ADS)

The paper describes the instruments and methods used in a study of plasma waves conducted aboard the Vega-1 and -2 interplanetary spacecraft, with special attention given to the characteristics of the two plasma wave analyzers (PWAs) used in the study: the PWA for low-frequency plasma waves and the PWA for high frequencies. Results are presented together with interpretation.

Klimov, S. I.; Korepanov, V. E.; Sopruniuk, P. M.; Savin, S. A.

401

Doppler Frequency in Interplanetary Radar and General Relativity.  

National Technical Information Service (NTIS)

The change of frequency of an interplanetary radar signal sent from the earth to another planet or to a space probe is worked out according to general relativity. The Schwarzschild spacetime is employed and its null geodesics control the motion of the sig...

G. C. Mcvittie

1972-01-01

402

An Interplanetary Rapid Transit System Between Earth and Mars  

Microsoft Academic Search

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

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

2003-01-01

403

Pioneer 10 studies of interplanetary shocks at large heliocentric distances  

Microsoft Academic Search

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

J. D. Mihalov; J. H. Wolfe

1979-01-01

404

The impact of ion propulsion on high energy interplanetary missions  

Microsoft Academic Search

Interplanetary science missions often require a significant on-board propulsive capability, which results in the need to carry large quantities of propellant. This reduces possible payload mass, or increases the overall size, mass and cost of the mission. Ion propulsion offers an attractive means of avoiding these large propellant masses associated with chemical propulsion systems. Indeed, if a spiral orbit-raising approach

David G Feam

1995-01-01

405

Interplanetary shocks preceded by solar-filament eruptions  

SciTech Connect

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

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

1986-12-01

406

Landau damping and steepening of interplanetary nonlinear hydromagnetic waves  

Microsoft Academic Search

According to collisionless shock theories, the thickness of a shock front should be of the order of the characteristic lengths of the plasmas (the Debye length, the proton and Larmor radii, etc.). Chao and Lepping (1974), found, however, that 30% of the observed interplanetary shocks at 1 AU have thicknesses much larger than these characteristic lengths. It is the objective

Aaron Barnes; J. K. Chao

1977-01-01

407

CME interactions with coronal holes and their interplanetary consequences  

Microsoft Academic Search

A significant number of interplanetary shocks (?17%) during cycle 23 were not followed by drivers. The number of such “driverless” shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the central meridian of

N. Gopalswamy; P. Mäkelä; H. Xie; S. Akiyama; S. Yashiro

2009-01-01

408

3-D model of ICME in the interplanetary medium  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

409

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

410

Modeling Magnetic Field Topology at Jupiter with the Khurana Magnetic Field Model  

NASA Astrophysics Data System (ADS)

To explore the degree of coupling between the interplanetary magnetic field (IMF) and Jupiter's magnetosphere, we traced magnetic field lines from the polar region of the planet using the Khurana [1997, 2005] magnetic field model. We used a parameterized definition of the Jovian magnetopause created by Joy et al. [2002] that varies with the value of the solar wind dynamic pressure. We searched for field lines that cross the magnetopause and that potentially connect to the interplanetary magnetic field. We further explored the variation on magnetic field structure with local time orientation of Jupiter's dipole (i.e. Central Meridian Longitude) as well as upstream solar wind and IMF conditions.

Cohen, I.; Bagenal, F.

2008-12-01

411

Solar Wind Quasi-invariant for Slow and Fast Magnetic Clouds  

NASA Astrophysics Data System (ADS)

The solar wind quasi-invariant (QI) has been defined by Osherovich, Fainberg, and Stone ( Geophys. Res. Lett. 26, 2597, 1999) as the ratio of magnetic energy density and the energy density of the solar wind flow. In the regular solar wind QI is a rather small number, since the energy of the flow is almost two orders of magnitude greater than the magnetic energy. However, in magnetic clouds, QI is the order of unity (less than 1) and thus magnetic clouds can be viewed as a great anomaly in comparison with its value in the background solar wind. We study the duration, extent, and amplitude of this anomaly for two groups of isolated magnetic clouds: slow clouds (360< v<450 km s-1) and fast clouds (450? v<720 km s-1). By applying the technique of superposition of epochs to 12 slow and 12 fast clouds from the catalog of Richardson and Cane ( Solar Phys. 264, 189, 2010), we create an average slow cloud and an average fast cloud observed at 1 AU. From our analysis of these average clouds, we obtain cloud boundaries in both time and space as well as differences in QI amplitude and other parameters characterizing the solar wind state. Interplanetary magnetic clouds are known to cause major magnetic storms at the Earth, especially those clouds which travel from the sun to the Earth at high speeds. Characterizing each magnetic cloud by its QI value and extent may help in understanding the role of those disturbances in producing geomagnetic activity.

Webb, Alla; Fainberg, Joseph; Osherovich, Vladimir

2012-04-01

412

Geoeffectiveness of the interplanetary manifestations of coronal mass ejections and solar-wind stream-stream interactions  

NASA Astrophysics Data System (ADS)

Coronal mass ejections and high-speed streams from the Sun, and related structures formed and evolved in interplanetary space, i.e. interplanetary manifestations of CMEs (ICMEs) and stream interaction regions (SIRs)/corotating interaction regions (CIRs), are mainly responsible for geomagnetic disturbances in the Earth's magnetic environment. However, the presence or absence of associated/finer structures of ICMEs (e.g., shock/sheath, magnetic cloud) and SIRs/CIRs (forward and reverse shocks, stream interface) might influence their geoeffectiveness as these features within large-scale structures of ICMEs and SIRs display different and varying plasma and field characteristics. In this work, we analyze the solar-wind plasma and field parameters (plasma velocity, density and pressure, magnetic field, its north-south component and electric field) together with geomagnetic activity parameters ( kp and Dst), applying the method of superposed epoch analysis. By systematically changing the time of passage of different features as epochs, e.g. discontinuities/shocks, CMEs/magnetic clouds in ICMEs and discontinuities/forward shocks in SIRs/CIRs, we study the relative geoeffectiveness of not only the large-scale structures (ICMEs/SIRs/CIRs), but of their finer features also. We critically analyze the differences in geoeffectiveness due to different structures and features, with distinct plasma/field characteristics, and we utilize these results to understand the mechanism during their interaction with geospace.

Mustajab, F.; Badruddin

2011-01-01

413

Magnetism.  

National Technical Information Service (NTIS)

This program describes magnets and magnetic materials by pointing out the characteristics of the magnetic field, the molecular arrangement of magnetized and unmagnetized metals, the laws of attraction and repulsion, and the factors that affect the amount ...

1972-01-01

414

Predicting the Global Average Temperature of the Thermosphere From an Empirical Model of the Polar Poynting Flux  

Microsoft Academic Search

The total Poynting flux flowing into both polar hemispheres as a function of time is compared with measurements of neutral densities in the thermosphere. An empirical model, based on satellite measurements, uses the solar wind and interplanetary magnetic field (IMF) to compute the total Poynting flux; this power flow is dissipated as heat in both polar ionospheres, which in turn

D. R. Weimer; E. K. Sutton; W. Tobiska

2010-01-01

415

A model of radiation conditions during spacecraft flights in the interplanetary space and in the Earth's magnetosphere.  

PubMed

Based on the available measurement data, simulations of radiation conditions during spacecraft flights in the interplanetary space and in the Earth's and Jupiter's radiation belts has been carried out. The > or = 10 MeV and > or = 30 MeV solar flare proton fluence forecast has been proposed for Cycle 22. Radiation conditions due to both magnetospheric electrons and protons and to solar flare protons, magnetic rigidity cutoff being taken into account, have been evaluated on spacecraft trajectories in the Earth's and Jupiter's magnetospheres. PMID:11537042

Getselev, I V; Ignatiev, P P; Kabashova, N A; Kontor, N N; Moszhukhina, A R; Timofeev, G A; Khotilovskaya, T G

1992-01-01

416

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

SciTech Connect

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

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