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Webber W.R.,New Mexico State University | Intriligator D.S.,Carmel Research Center | Decker R.B.,Johns Hopkins University
AIP Conference Proceedings

Motivated by the recent observation that two separate periods of enhanced intensities of solar wind ions at ∼2 times the normal solar wind energy were observed at times of the shock arrival and at the magnetic field maximum at Voyager 2 at 73 AU, arising from the 2003 Halloween event at the Earth, we have re-examined the higher energy proton data from 0.06 to 20 MeV from the LECP and CRS instruments on V2 for this event. We find that there are two separate regions of particle acceleration in this outward propagating merged interaction region. The one near the shock has a much harder proton spectrum extending up to ∼20 MeV, but with a relative paucity of particles below ∼1.0 MeV. The other, near the time of maximum magnetic field fluctuations, is dominated by protons at energies ∼1 MeV or less with a sharp cutoff above 2 MeV. The two regions are separated spatially and the half width of the respective radial intensity distributions at each energy can be used to estimate a local diffusion coefficient. The composite spectrum from these two regions is a power law with a spectral index ∼-1.4 below 1 MeV steepening to-3.2 above ∼2 MeV. This observation has important implications astrophysically, beyond what is seen locally, because most astrophysical observations of accelerated spectra cannot resolve the two components and therefore miss the clues that help identify the particle acceleration mechanisms. © 2012 American Institute of Physics. Source

Webber W.R.,New Mexico State University | Intriligator D.S.,Carmel Research Center
Journal of Geophysical Research: Space Physics

We have extended our earlier calculations of the distance to the heliospheric termination shock (HTS), which covered the period from the launch of V1 and V2 in 1977 to 2005, to the period from 2006 to 2011. During this latter period, the solar wind speed, ram pressure, and magnetic field decreased to the lowest levels in recent history, related to the sunspot minimum in 2008-2009. The HTS distance has decreased correspondingly so that V1, which was crossed by the HTS at 94 AU in late 2004, would now, in early 2011, be expected to reach the HTS at a distance of ∼80 AU, when the HTS distance would be expected to be at its minimum. Similarly, V2, which was crossed by the HTS at 84 AU in mid-2007, would, in early 2011, reach the HTS at a distance of only 74 AU. These distances, in early 2011, are ∼15% less than those at which V1 and V2 initially reached the HTS. The distance to the heliopause (HP) is more uncertain, but recent calculations place its equilibrium distance at between 1.4 and 1.6 times the HTS distance. Allowing for an additional 1 year for the HP to reach its equilibrium minimum distance relative to the HTS would mean that, assuming this distance remains a constant fraction larger than the HTS distance, the HP distance would be at its minimum distance of (1.4-1.6) × 80 AU = 112-128 AU at V1 in early 2012. At this time, V1 will be in the direction of a distance of ∼120 AU so that there is a possibility that V1 could cross the HP and enter interstellar space at the time 2012.0 ± 1 year. If the crossing does not happen during this time period, then it is unlikely that V1 will reach this defining boundary before about 2016 because of the expected outward motion of the HTS and the HP toward their more normal distances of 85-96 and ∼120-140 AU, coincident with the maximum of the new sunspot cycle. Copyright 2011 by the American Geophysical Union. Source

Kartalev M.,Bulgarian Academy of Science | Keremidarska V.,Bulgarian Academy of Science | Keremidarska V.,Microsoft | Dryer M.,National Oceanic and Atmospheric Administration | Dryer M.,Carmel Research Center
Earth, Moon and Planets

Earlier developed single fluid gas-dynamic model of solar wind–comet ionosphere interaction is applied to reveal some specifics in the morphology of the shocked “contaminated” solar wind region (cometosheath). The model is based on the Euler equations with added mass-loading, mass-loss and frictional force terms. Numerous reactions are taken into account in these terms including photoionization, charge transfer, dissociative recombination and ion-neutral frictional force. The electromagnetic terms are omitted, thus reducing the MHD single-fluid system of equations to gas-dynamic one. The used shock-fitting numerical scheme allows the separation of distinct areas formed by the considered interaction and exploration of their properties in detail. Attention is focused on the region between the shock wave and the contact surface as well as on the positions of these boundaries. Accurate examination of the distribution of density, temperature and velocity reveals spatial variations that resemble the variations registered by a number of spacecraft in the vicinity of comets. No specific comparisons with data are made at this stage. Two very first events of the Rosetta spacecraft’s crossing of the magnetic cavity boundary around Comet 67P/Churyumov–Gerasimenko are discussed using a “faux-transient” application of our steady-state model. © 2016 Springer Science+Business Media Dordrecht Source

Two of the most recent outer heliospheric kHz emissions detected by the University of Iowa plasma wave detector on Voyager 1 started at about 2004.64 and 2006.39, respectively. Large interplanetary shocks reached V1 and V2, which are near the heliospheric termination shock, at almost the same time that the two kHz radio emissions turned-on. So, in fact, the arrivals of these large shocks near the heliospheric termination shock were coincident with the onset of these kHz emissions. These two large shocks were unusual in that they were the two strongest shocks in solar cycle 23 seen in the outer heliosphere at V2. They had developed maximum dynamic pressures ∼4-6 times the average solar wind dynamic pressure for periods >26 days by the time they reached V2. © 2010 American Institute of Physics. Source

Intriligator D.S.,Carmel Research Center | Detman T.,Carmel Research Center | Intriligator J.,Carmel Research Center | Intriligator J.,Bangor University | And 8 more authors.
AIP Conference Proceedings

We have analyzed space weather throughout the heliosphere using the three-dimensional (3D) timedependent magnetohydrodynamic (MHD) Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI) [1] out to Voyager 2 (V2) and beyond by comparing the HHMS-PI model results with the available spacecraft data. We also have analyzed space weather throughout the heliosphere through in-depth analyses of the available simultaneous data from a number of instruments on spacecraft at various locations. In this paper we focus on our HHMS-PI modeling (starting at the Sun) of the Halloween 2003 solar events by comparing the model results with spacecraft data at ACE and Ulysses. For the Halloween 2003 solar events we also summarize our inter-comparisons of the in-situ V2 data from many of the V2 instruments. These analyses of the comparisons ("benchmarking") of HHMS-PI simulations and the various spacecraft data and of our in-depth analyses of the V2 particle and field data indicate that particle acceleration and other important physical processes are associated with the heliospheric propagation of these large solar cycle 23 space weather events. We conclude that space weather, originating at the Sun, can have important affects throughout the heliosphere to distances as great as 73 AU and beyond. © 2012 American Institute of Physics. Source

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