J. D. Richardson

Massachusetts Institute of Technology, Cambridge, Massachusetts, United States

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Publications (197)494.09 Total impact

  • L. F. Burlaga · N. F. Ness · J. D. Richardson
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    ABSTRACT: We discuss magnetic field and plasma observations from Voyager 2 (V2) during 2011, when V2 was beginning to see the effects of increasing solar activity following the solar minimum in 2009. The magnetic field strength (B) profile showed large amplitude fluctuations that can be resolved into a linear increase of B with time and a sinusoidal variation of the period of 86.2 ± 0.8 days. Voyager 2 was in a unipolar region in which the magnetic polarity was directed away from the sun along the Parker spiral 96% of the time, indicating that V2 was poleward of the heliospheric current sheet (HCS) throughout most of 2011. The distribution of B was lognormal, but a Gaussian distribution was observed when the linear variation of B was subtracted from the data. The distribution of daily increments of B was a q-Gaussian distribution with q = 1.1 ± 0.1, which is less intermittent than normally observed in the heliosheath. However, the distribution of hourly increments of B was a q-Gaussian distribution with q = 1.5 ± 0.03. The density, temperature and velocity increased linearly from the beginning of 2011 to approximately day 254. The magnetic and thermal pressure tended to increase throughout the year, but the magnetic pressure dominated most of the time. The counting rate of >70 MeV/n particles increased rapidly during the first 250 days, but it leveled out during the rest of the year when B was stronger. The empirical CR-B relationship describes this behavior.
    Journal of Geophysical Research: Space Physics 08/2014; 119(8). DOI:10.1002/2014JA020297 · 3.44 Impact Factor
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    ABSTRACT: Jupiter magnetospheric interactions and surface composition, both important to subsurface ocean detection for the Galilean icy moons Europa, Ganymede, and Callisto, can be measured using plasma ion mass spectrometry on either an orbiting spacecraft or one designed for multiple flybys of these moons. Detection of emergent oceanic materials at the Europa surface is more likely than at Ganymede and Callisto. A key challenge is to resolve potential intrinsic Europan materials from the space weathering patina of iogenic species implanted onto the sensible surface by magnetospheric interactions. Species-resolved measurements of pickup ion currents are also critical to extraction of oceanic induced magnetic fields from magnetospheric interaction background dominated by these currents. In general the chemical astrobiological potential of Europa should be determined through the combination of surface, ionospheric, and pickup ion composition measurements. The requisite Ion Mass Spectrometer (IMS) for these measurements would need to work in the high radiation environment of Jupiter's magnetosphere between the orbits of Europa and Ganymede, and beyond. A 3D hybrid model of the moon-magnetosphere interaction is also needed to construct a global model of the electric and magnetic fields, and the plasma environment, around Europa. Europa's ionosphere is probably usually dominated by hot pickup ions with 100–1000 eV temperatures, excursions to a “classical” cold ionosphere likely being infrequent. A field aligned ionospheric wind driven by the electron polarization electric field should arise and be measurable.
    Planetary and Space Science 11/2013; 88:26–41. DOI:10.1016/j.pss.2013.01.013 · 1.63 Impact Factor
  • F. Bagenal · R. J. Wilson · J. D. Richardson · W. R. Paterson
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    ABSTRACT: We have collated and, in some cases, re-analyzed the plasma data obtained by the Voyager 1 & 2 and Galileo spacecraft in the magnetosphere of Jupiter. We present the derived spatial and temporal variations in plasma density, temperature and velocity throughout the plasmasheet. We also use a simple model for density distribution with latitude to produce 3-D maps of plasmasheet properties and derive the flow of mass and energy in the magnetosphere.
  • A. Lynnyk · J. Safránková · Z. Nemecek · J. D. Richardson
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    ABSTRACT: Interplanetary coronal mass ejections (ICMEs) and their subset, magnetic clouds (MCs), are important manifestations of solar activity which have substantial impact on the geomagnetic field. We re-analyze events already identified in Wind and Voyager 2 data and estimate changes of their geometry along the path from the Sun. The analysis is based on the thickness of the sheath between a shock and a particular ICME or MC which is proportional to the apparent curvature radius of ICMEs/MCs. We have found that this apparent radius of curvature increases with the Mach number and this effect is attributed to the larger deformation of the fast ICME/MC. Further, the relative sheath thickness that is proportional to the flux rope oblateness decreases with the magnetic field intensity inside the ICME/MC and increases with the heliospheric distance.
    Planetary and Space Science 07/2011; 59:840-847. DOI:10.1016/j.pss.2011.03.016 · 1.63 Impact Factor
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    ABSTRACT: All the current global models of the heliosphere are based on the assumption that the magnetic field in the heliosheath, in the region close to the heliopause is laminar. We argue that in that region the heliospheric magnetic field is not laminar but instead consists of magnetic bubbles. Recently, we proposed that the annihilation of the "sectored" magnetic field within the heliosheath as it is compressed on its approach to the heliopause produces the anomalous cosmic rays and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densely-packed magnetic islands/bubbles are produced. These magnetic islands/bubbles will be convected with the ambient flows as the sector region is carried to higher latitudes filling the heliosheath. We further argue that the magnetic islands/bubbles will develop upstream within the heliosheath. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the heliopause. We present a 3D MHD simulation with very high numerical resolution that captures the north-south boundaries of the sector region. We show that due to the high pressure of the interstellar magnetic field a north-south asymmetry develops such that the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We suggest that this scenario is supported by the following changes that occur around 2008 and from 2009.16 onward: a) the sudden decrease in the intensity of low energy electrons detected by Voyager 2; b) a sharp reduction in the intensity of fluctuations of the radial flow; and c) the dramatic differences in intensity trends between GCRs at V1 and 2. We argue that these observations are a consequence of V2 leaving the sector region of disordered field during these periods and crossing into a region of unipolar laminar field.
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    ABSTRACT: The combination of the Interstellar Boundary Explorer (IBEX) all‐sky maps of the energetic neutral atom fluxes with the Voyager in situ measurements gives us a unique opportunity to learn more about the physics governing the solar wind (SW) interaction with the local interstellar medium (LISM). Moreover, since the position of the ribbon of an enhanced ENA flux in the sky strongly depends on the LISM properties, we are able to constrain those by comparing numerical simulations with the IBEX observations. In this paper, we discuss the current status of the Huntsville model of the SW‐LISM interaction, compare numerical results with the IBEX and Voyager observations, and discuss the importance of taking into account time‐dependent phenomena, particularly the solar cycle effects.
    12/2010; 1302(1):3-12. DOI:10.1063/1.3529988
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    ABSTRACT: The Rankine‐Hugoniot (R‐H) jump conditions at the heliospheric termination shock provide a means of knitting together the in situ measurements from Voyager 2 (VGR2) with the remote sensing of the heliosheath plasma via energetic neutral atom (ENA) imaging by IBEX and Cassini∕INCA. The VGR2 instrument suite has a gap (∼1–30 keV) in the ion measurements. While the ENA images (0.2–6 keV and 5–55 keV) fill the VGR2 gap in the pixel containing the VGR2 spacecraft, they do so only in the sense that they provide the ion intensity integrated along the radial line of sight throughout the entire heliosheath. The synthesis we attempt is further complicated by the observational results from all three spacecraft that the non‐thermal component of the ion pressure dominates that of the thermal component. We therefore have developed (and applied) a generalized formulation of the R‐H conditions that does not invoke an equation of state, but rather can directly ingest the instrumentally‐measured non‐thermal spectrum. The result is an estimate that the ratio (upstream∕downstream) of the non‐thermal pressure is ∼43%, confirming anew that the termination shock (at least at VGR2) is strongly mediated by non‐thermal ions.
    12/2010; 1302(1):133-141. DOI:10.1063/1.3529960
  • J. Safrankova · O. Gutynska · Z. Nemecek · A. Lynnyk · J. D. Richardson
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    ABSTRACT: We analyzed high-resolution observations of the magnetic field strength measured by Voyager 1 and Voyager 2 on their path through the Jupiter' magnetosheath and Voyager 2 in the heliosheath prior to and after the crossing of the termination shock and compared them with those fluctuations measured by Cluster and THEMIS in the different places of the Earth's magnetosheath and with magnetic field variations in the sheaths of ICMEs and CMEs registered by Wind as well as Voyager 1 and 2 on their path. To characterize the type of fluctuations, we investigate their spectral slopes and correlation properties, mainly the correlations between the magnetic field and ion density. Finally, we discuss similarities and differences of the fluctuations in different regions on various time scales (from several hours to tens of days).
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    C. Wang · T. R. Sun · X. C. Guo · J. D. Richardson
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    ABSTRACT: Observations show that the geosynchronous magnetic field in midnight sector sometimes decreases when an interplanetary (IP) fast forward shock (FFS) passes Earth, even though the magnetosphere is always compressed. We perform case studies of the response observed by the GOES spacecraft at geosynchronous orbit near midnight to two IP shocks passing Earth. One shock produces a decrease in BZ (a negative response) and the other an increase in BZ (a positive response). A global 3D MHD code is run to reproduce the responses at geosynchronous orbit, and to further provide information on the initiation and development of BZ variations in the entire magnetosphere. The model reveals that when a FFS sweeps over the magnetosphere, there exist mainly two regions, a positive response region caused by the compressive effect of the shock and a negative response region which is probably associated with the temporary enhancement of earthward convection in the nightside magnetosphere. The spacecraft may observe an increase or decrease of the magnetic field depending on which region it is in. The numerical results reproduce the main characters of the geosynchronous magnetic field response to IP shocks for these two typical cases.
    Journal of Geophysical Research Atmospheres 10/2010; 115(A10). DOI:10.1029/2010JA015451 · 3.44 Impact Factor
  • John F. Cooper · M. E. Hill · J. D. Richardson · S. J. Sturner
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    ABSTRACT: The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism (Cooper et al., Plan. Sp. Sci., 2009) and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.
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    C. Wang · H. Li · J. D. Richardson · J. R. Kan
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    ABSTRACT: Interplanetary (IP) shocks disturb the magnetosphere-ionosphere system resulting in geosynchronous magnetic field changes and sudden impulses observed by ground-based magnetometers. We extend the implications of a previous statistical study and show that sudden impulses (SIs) can be used to estimate some parameters at the L1 point and geosynchronous orbit, including the change of the square root of solar wind dynamic pressure across the shock and the associated geosynchronous magnetic field changes near the subsolar region. It should be pointed out that the relationship between magnetospheric field change and SIs amplitude and the solar wind dynamic pressure is not a single valued one, but a statistical relationship is useful in cases when interplanetary data are not available. Empirical formulae deduced from observations can be used to estimate certain IP shock characteristics and geosynchronous magnetic field changes from sudden impulse data observed on the ground, with the prediction efficiency as high as 90% and 86%, respectively. These estimates are useful for studying historic, pre-space era data or if the L1 and geosynchronous data are not available at some future time.
    Journal of Geophysical Research Atmospheres 01/2010; 115. DOI:10.1029/2009JA014833 · 3.44 Impact Factor
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    L. F. Burlaga · N. F. Ness · Y.-M. Wang · N. R. Sheeley · J. D. Richardson
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    ABSTRACT: 1] The density and temperature profiles of the plasma measured by Voyager 2 (V2) behind the termination shock changed abruptly near 2008.6 from relatively large average values and large fluctuations during 2007.7 to 2008.6 (interval A) to relatively low average values and very small‐amplitude fluctuations during 2008.6 to 2009.4 (interval B). This paper shows that the change in the magnetic field strength B(t) was less abrupt than the plasma changes, and the fluctuations of the magnetic field strength in interval B were of moderate amplitude, with indications of a quasiperiodic structure in part of the interval. The magnetic field was directed away from the sun (positive polarity) ∼ 78% ± 5% of the time in both interval A and interval B, changing in an irregular way from positive to negative polarities throughout the interval. The polarity distribution indicates that the minimum latitudinal extent of the heliospheric current sheet (HCS) was near V2 throughout the interval, consistent with the extrapolated minimum latitudes of the HCS computed from solar magnetic field observations. Thus, V2 was observing magnetic fields from the southern polar coronal hole most of the time. The distribution of B was lognormal in interval A and Gaussian interval B.
    Journal of Geophysical Research Atmospheres 01/2010; 74(115). DOI:10.1029/2009JA015239 · 3.44 Impact Factor
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    M Opher · F Alouani Bibi · G Toth · J D Richardson · V V Izmodenov · T I Gombosi
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    ABSTRACT: Magnetic fields play an important (sometimes dominant) role in the evolution of gas clouds in the Galaxy, but the strength and orientation of the field in the interstellar medium near the heliosphere has been poorly constrained. Previous estimates of the field strength range from 1.8-2.5 microG and the field was thought to be parallel to the Galactic plane or inclined by 38-60 degrees (ref. 2) or 60-90 degrees (ref. 3) to this plane. These estimates relied either on indirect observational inferences or modelling in which the interstellar neutral hydrogen was not taken into account. Here we report measurements of the deflection of the solar wind plasma flows in the heliosheath to determine the magnetic field strength and orientation in the interstellar medium. We find that the field strength in the local interstellar medium is 3.7-5.5 microG. The field is tilted approximately 20-30 degrees from the interstellar medium flow direction (resulting from the peculiar motion of the Sun in the Galaxy) and is at an angle of about 30 degrees from the Galactic plane. We conclude that the interstellar medium field is turbulent or has a distortion in the solar vicinity.
    Nature 12/2009; 462(7276):1036-8. DOI:10.1038/nature08567 · 42.35 Impact Factor
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    C. Wang · H. Li · J. D. Richardson · J. R. Kan
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    ABSTRACT: Interplanetary (IP) shocks disturb the magnetosphere-ionosphere system resulting in geosynchronous magnetic field changes and sudden impulses observed by ground-based magnetometers. We extend the implications of a previous statistical study and show that sudden impulses (SIs) can be used to estimate key parameters at L1 point and geosynchronous orbit, including the arrival time of an IP shock at L1 point, the change of the solar wind dynamic pressure across the shock, and the associated geosynchronous magnetic field changes near the subsolar region. Empirical formulae deduced from observations can be used to estimate certain IP shock characteristics and geosynchronous magnetic field changes from observed sudden impulse data observed on the ground with prediction efficiency as high as 89%. These estimates are useful for studying historic, pre-space era data, or if L1 and geosynchronous data are not available at some future time.
  • M. Opher · F. Alouani Bibi · G. Toth · J. D. Richardson · V. Izmodenov · T. I. Gombosi
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    ABSTRACT: We show that the heliosheath flows can be used as a new and highly important data set to determine the interstellar magnetic field orientation and magnitude. We use a new three-dimensional model that includes both the plasma and the neutral H atoms as well as the interplanetary and interstellar magnetic fields. The field orientation and magnitude that we derive differ substantially from the those previously reported (Opher et al. 2006, 2007). We comment on the consequences of this result on the heliospheric global asymmetries (such as the field-aligned streaming of low energy particles, the distance of the termination shock, and the shape of the heliopause). We comments as well on the inference on the conditions on the local interstellar medium. We study the effect of numerical resolution and non-stationary on the model shock and find them to be negligible. We also comment on the possible effects of the tilt of current sheet, not included currently in the model (which at the time of the termination shock crossings of Voyager 1 and 2 was about 30 degrees). We present a simulation with a scaled down heliosphere which includes a dynamic time dependent current sheet.
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    ABSTRACT: Properties of the heliospheric interface, a complex product of an interaction between charged and neutral particles and magnetic fields in the heliosphere and surrounding Circumheliospheric Medium, are far from being fully understood. Recent Voyager spacecraft encounters with the termination shock and their observations in the heliosheath revealed multiple energetic particle populations and noticeable spatial asymmetries not accounted for by the classic theories. Some of the challenges still facing space physicists include the origin of anomalous cosmic rays, particle acceleration downstream of the termination shock, the role of interstellar magnetic fields in producing the global asymmetry of the interface, the influence of charge exchange and interstellar neutral atoms on heliospheric plasma flows, and the signatures of solar magnetic cycle in the heliosheath. These and other outstanding issues are reviewed in this joint report of working groups 4 and 6.
    Space Science Reviews 03/2009; 143(1-4):57-83. DOI:10.1007/s11214-009-9488-7 · 5.87 Impact Factor
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    M. Opher · J. D. Richardson · G. Toth · T. I. Gombosi
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    ABSTRACT: Magnetic effects are ubiquitous and known to be crucial in space physics and astrophysical media. We have now the opportunity to probe these effects in the outer heliosphere with the two spacecraft Voyager1 and2. Voyager1 crossed, in December 2004, the termination shock and is now in the heliosheath. On August30, 2007 Voyager2 crossed the termination shock, providing us for the first time in-situ measurements of the subsonic solar wind in the heliosheath. With the recent in-situ data from Voyager1 and 2 the numerical models are forced to confront their models with observational data. Our recent results indicate that magnetic effects, in particular the interstellar magnetic field, are very important in the interaction between the solar system and the interstellar medium. We summarize here our recent work that shows that the interstellar magnetic field affects the symmetry of the heliosphere that can be detected by different measurements. We combined radio emission and energetic particle streaming measurements from Voyager1 and 2 with extensive state-of-the art 3D MHD modeling, to constrain the direction of the local interstellar magnetic field. The orientation derived is a plane ∼60°–90° from the galactic plane. This indicates that the field orientation differs from that of a larger scale interstellar magnetic field, thought to parallel the galactic plane. Although it may take 7–12 years for Voyager2 to leave the heliosheath and enter the pristine interstellar medium, the subsonic flows are immediately sensitive to the shape of the heliopause. The flows measured by Voyager2 in the heliosheath indicate that the heliopause is being distorted by local interstellar magnetic field with the same orientation as derived previously. As a result of the interstellar magnetic field the solar system is asymmetric being pushed in the southern direction. The presence of hydrogen atoms tend to symmetrize the solutions. We show that with a strong interstellar magnetic field with our most current model that includes hydrogen atoms, the asymmetries are recovered. It remains a challenge for future works with a more complete model, to explain all the observed asymmetries by V1 andV2. We comment on these results and implications of other factors not included in our present model.
    Space Science Reviews 02/2009; 143(1):43-55. DOI:10.1007/s11214-008-9453-x · 5.87 Impact Factor
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    C. Wang · J. B. Liu · H. Li · Z. H. Huang · J. D. Richardson · J. R. Kan
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    ABSTRACT: We perform a statistical survey of geospace magnetic field responses, including the geosynchronous magnetic field and the sudden impulses on the ground, to interplanetary shocks (IP shocks) between 1998 and 2005. The magnitude of the geosynchronous magnetic field (dB z ) responses to IP shocks depends strongly on local time, which peaks near the noon meridian; however, the relative magnitude of the responses depends only weakly on local time. These results are similar to those obtained from the statical study of the responses to solar wind dynamic pressure pulses. However, negative responses (where dB z is negative) were sometimes observed in the nightside of the magnetosphere even though the IP shocks always caused increases in the solar wind dynamic pressure, a new phenomenon not widely reported in the literature. Our analysis shows that ˜75% of negative responses in the midnight sector are associated with southward interplanetary magnetic field. For a moderately compressed magnetosphere, the amplitude of the geosynchronous response dB z could be determined by the average value of the background local magnetic field. As the magnitude of the upstream solar wind dynamic pressure increases, the rate of response increases correspondingly. The dB z at the geosynchronous orbit near local noon and the amplitude of sudden impulses (dSYM-H) on the ground are highly correlated.
    Journal of Geophysical Research Atmospheres 01/2009; 114. DOI:10.1029/2008JA013794 · 3.44 Impact Factor
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    ABSTRACT: A shocklike transition at 2003.37 from quasi-periodic flows to increasingly fast flows was observed by Voyager 2 (V2) near 70 AU. The transition was related to the appearance of coronal holes near the solar equatorial plane on Carrington rotation (CR) ≈1994. Several important features (two cycles of quasi-periodic variations in V and B, a shock, a merged interaction region (MIR) with strong magnetic fields in a region with increasing speed, and a second shock that was related to the 2003 October 29-30 events at 1 AU) were observed by V2 from 2002.8 to 2004.4. A one-dimensional multifluid MHD model shows that these features at V2 evolved from the flows observed by ACE at 1 AU. The model also shows that the features propagated through the heliosphere out to 95 AU. The changes in the magnetic field associated with the features at V2 caused changes in the cosmic-ray intensity (CRI) of particles more energetic than 70 MeV nucleon-1. The quasi-periodic variations were related to variations in CRI, but they produced no appreciable net decrease in the CRI. Both the first shock and the MIR produced a steplike decrease in the CRI at V2.
    The Astrophysical Journal 12/2008; 618(2):1074. DOI:10.1086/426105 · 6.28 Impact Factor
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    J. D. Richardson · Y Liu · C Wang · D. J. Mccomas
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    ABSTRACT: Context. The ionized solar wind interacts directly with the interstellar neutrals which flow into the heliosphere. These neutrals are ionized, mainly by charge exchange, then accelerated to the solar wind speed with the momentum and energy removed from the bulk flow of the solar wind. Thus, by measuring the solar wind slowdown, one can estimate the interstellar neutral density.Aims. In July 2005, Ulysses at 5 AU and Voyager 2 near 80 AU were at the same heliolatitude. We use this alignment to determine the solar wind speed decrease between these two spacecraft.Methods. Ulysses data are used as input to a 1-D MHD model which includes the effects of pickup ions. We removed a section of data contaminated by an ICME directed toward Voyager 2.Results. Comparison of the Voyager 2 speeds with the model results shows that the solar wind speed decreased by 67 km s$^{-1}$ between Ulysses and Voyager 2, consistent with an interstellar neutral density at the termination shock of 0.09 cm$^{-3}$.
    Astronomy and Astrophysics 11/2008; 491. DOI:10.1051/0004-6361:20078565 · 4.48 Impact Factor

Publication Stats

3k Citations
494.09 Total Impact Points

Institutions

  • 1205–2014
    • Massachusetts Institute of Technology
      • • Kavli Institute for Astrophysics and Space Research
      • • Department of Physics
      Cambridge, Massachusetts, United States
  • 2009
    • George Mason University
      Fairfax, Virginia, United States
  • 2004–2007
    • Chinese Academy of Sciences
      • Center for Space Science and Applied Research
      Peping, Beijing, China
  • 2003
    • Charles University in Prague
      • Faculty of Mathematics and Physics
      Praha, Praha, Czech Republic
  • 1999
    • Tel Aviv University
      Tell Afif, Tel Aviv, Israel