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Full-Text Articles in Physical Sciences and Mathematics
A Test Of The Interstellar Boundary Explorer Ribbon Formation In The Outer Heliosheath, Konstantin V. Gamayunov, Jacob Heerikhuisen, Hamid K. Rassoul
A Test Of The Interstellar Boundary Explorer Ribbon Formation In The Outer Heliosheath, Konstantin V. Gamayunov, Jacob Heerikhuisen, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
NASA's Interstellar Boundary EXplorer (IBEX) mission is imaging energetic neutral atoms (ENAs) propagating to Earth from the outer heliosphere and local interstellar medium (LISM). A dominant feature in all ENA maps is a ribbon of enhanced fluxes that was not predicted before IBEX. While more than a dozen models of the ribbon formation have been proposed, consensus has gathered around the so-called secondary ENA model. Two classes of secondary ENA models have been proposed; the first class assumes weak scattering of the energetic pickup protons in the LISM, and the second class assumes strong but spatially localized scattering. Here we …
Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Galactic Cosmic-Ray Modulation In A Realistic Global Magnetohydrodynamic Heliosphere, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Aerospace, Physics, and Space Science Faculty Publications
To understand the behavior of cosmic-ray modulation seen by the two Voyager spacecraft in the region near the termination shock (TS) and in the heliosheath at a distance of >100 AU, a realistic magnetohydrodynamic global heliosphere model is incorporated into our cosmic-ray transport code, so that the detailed effects of the heliospheric boundaries and their plasma/magnetic geometry can be revealed. A number of simulations of cosmic-ray modulation performed with this code result in the following conclusions. (1) Diffusive shock acceleration by the TS can significantly affect the level of cosmic-ray flux and, in particular, its radial gradient profile in the …
Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang
Stochastic Acceleration Of Suprathermal Particles Under Pressure Balance Conditions, Thorsten Antecki, Reinhard Schlickeiser, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f ∝ p −5,which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V0 and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the …
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Nikolai V. Pogorelov, Jacob Heerikhuisen, Hamid K. Rassoul
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Nikolai V. Pogorelov, Jacob Heerikhuisen, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
A self-consistent model of the interstellar pickup protons, the slab component of the Alfvenic turbulence, and core solar wind (SW) protons is presented for r {>=} 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvenic power spectral density, and a third equation governs SW temperature including source due to the Alfven wave energy dissipation. A fraction of the pickup proton free energy, f{sub D} , which is actually released in the waveform during isotropization, is taken from the quasi-linear consideration without …
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Self-Consistent Model Of The Interstellar Pickup Protons, Alfvenic Turbulence, And Core Solar Wind In The Outer Heliosphere, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov, Jacob Heerikhuisen
Aerospace, Physics, and Space Science Faculty Publications
A self-consistent model of the interstellar pickup protons, the slab component of the Alfvenic turbulence, and core solar wind (SW) protons is presented for r {>=} 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvenic power spectral density, and a third equation governs SW temperature including source due to the Alfven wave energy dissipation. A fraction of the pickup proton free energy, f{sub D} , which is actually released in the waveform during isotropization, is taken from the quasi-linear consideration without …
A Theory Of Bimodal Acceleration Of Pickup Ions By Compressive Solar Wind Turbulence Under Pressure Balance, Ming Zhang, Reinhard Schlickeiser
A Theory Of Bimodal Acceleration Of Pickup Ions By Compressive Solar Wind Turbulence Under Pressure Balance, Ming Zhang, Reinhard Schlickeiser
Aerospace, Physics, and Space Science Faculty Publications
Recently, it was demonstrated that stochastic acceleration of particles going through a series of compressive plasma waves can be efficient and fast. It could be too fast so that the pressure built up by the accelerated particles may in turn modify the amplitude of waves to prevent the particles from having an exploding pressure. We call this condition pressure balance. In this paper, we take into account the fact that active acceleration of particles only occupies a limited volume of space due to a possible intermittent nature of plasma waves or turbulence. We develop a bimodal acceleration theory that treats …
Cosmic-Ray Modulation By The Global Merged Interaction Region In The Heliosheath, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov
Cosmic-Ray Modulation By The Global Merged Interaction Region In The Heliosheath, Xi Luo, Ming Zhang, Hamid K. Rassoul, Nikolai V. Pogorelov
Aerospace, Physics, and Space Science Faculty Publications
It was found by Voyager 1 and Voyager 2 that the Global Merged Interaction Region (GMIR) still has effects on cosmic-ray transport in the heliosheath. The GMIR produced by the intense solar activities of 2005 September propagated into the heliosheath in 2006, causing several decreases in the cosmic-ray flux at Voyager 1. Motivated by these observations, we investigate cosmic-ray modulation by the GMIR in the heliosheath using a three-dimensional Galactic cosmic-ray modulation code that includes the drift effect, termination shock, and a propagating GMIR. The simulation reproduces all major modulation features found by previous cosmic-ray observations in the supersonic solar …
Pitch Angle Scattering In The Outer Heliosheath And Formation Of The Interstellar Boundary Explorer Ribbon, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul
Pitch Angle Scattering In The Outer Heliosheath And Formation Of The Interstellar Boundary Explorer Ribbon, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
The dominant and unexpected feature in the first Interstellar Boundary EXplorer (IBEX) maps is a ribbon of the enhanced energetic neutral atom (ENA) emissions. Presenting the first results from IBEX,McComas et al. identified six possible mechanisms of ribbon formation. One of the mechanisms, the so-called secondary ENA mechanism, was already quantitatively elaborated by Heerikhuisen et al., and they successfully reproduced the main features of the ribbon. We further study the "secondary ENA" mechanism by quantifying a previously omitted stage of the proton evolution between two consecutive acts of the charge-exchange in the outer heliosheath (OHS). The main findings can be …
Pitch Aangle Scattering In The Outer Heliosheath And Formation Of The Interstellar Boundary Explorer Ribbon, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul
Pitch Aangle Scattering In The Outer Heliosheath And Formation Of The Interstellar Boundary Explorer Ribbon, Konstantin V. Gamayunov, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
The dominant and unexpected feature in the first Interstellar Boundary EXplorer (IBEX) maps is a ribbon of the enhanced energetic neutral atom (ENA) emissions. Presenting the first results from IBEX,McComas et al. identified six possible mechanisms of ribbon formation. One of the mechanisms, the so-called secondary ENA mechanism, was already quantitatively elaborated by Heerikhuisen et al., and they successfully reproduced the main features of the ribbon. We further study the "secondary ENA" mechanism by quantifying a previously omitted stage of the proton evolution between two consecutive acts of the charge-exchange in the outer heliosheath (OHS). The main findings can be …
Abundances And Energy Spectra Of Corotating Interaction Region Heavy Ions Observed During Solar Cycle 23, Glenn M. Mason, Richard A. Leske, Mihir I. Desai, Christina M.S. Cohen, Joseph R. Dwyer, Joseph E. Mazur, Richard A. Mewaldt, Robert E. Gold, Stamatios M. Krimigis
Abundances And Energy Spectra Of Corotating Interaction Region Heavy Ions Observed During Solar Cycle 23, Glenn M. Mason, Richard A. Leske, Mihir I. Desai, Christina M.S. Cohen, Joseph R. Dwyer, Joseph E. Mazur, Richard A. Mewaldt, Robert E. Gold, Stamatios M. Krimigis
Aerospace, Physics, and Space Science Faculty Publications
Using instruments on the ACE spacecraft, we surveyed the heavy-ion spectra and composition over the range He– Fe for 41 corotating interaction regions (CIRs) during 1998–2007. Below~ 1 MeV nucleon^-1 the spectra are power laws in kinetic energy nucleon^-1 with an average spectral index of 2:51 ± 0:10, rolling over above ~ 1 MeV nucleon^-1 to power-law spectra with an average index of 4:47 ± 0:17. The spectral shapes for different species are similar, leading to relative abundances that are constant over our energy range, even though the intensities cover up to 8 orders of magnitude. Relative to oxygen, the …
A New Phenomenon In Impulsive-Flare-Associated Energetic Particles, Eileen E. Chollet, Joe Giacalone, Joseph E. Mazur, M Al Dayeh
A New Phenomenon In Impulsive-Flare-Associated Energetic Particles, Eileen E. Chollet, Joe Giacalone, Joseph E. Mazur, M Al Dayeh
Aerospace, Physics, and Space Science Faculty Publications
We present ACE/ULEIS and Wind/STEP observations of a new and unusual feature of energetic ions between 0.02 and 3 MeV nucleon ˉ¹ associated with impulsive solar flares. In addition to the usual velocity dispersion associated with the transit in the heliospheric magnetic field of energetic particles from a small localized source on the Sun, these events also show intermittent behavior that may be related to the magnetic flux tube structure of the solar wind. These are anomalous bursts of low-energy particles, which we call "tassels." Tassels are enhancements of ions extending to much lower energies than those associated with the …
Solar Cycle Variations In The Composition Of The Suprathermal Heavy-Ion Population Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
Solar Cycle Variations In The Composition Of The Suprathermal Heavy-Ion Population Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
We have measured the annual variation in the quiet-time composition of interplanetary suprathermal ions between 0.04 and 1 MeV nucleon-1 from 1994 November 20 through 2006 January 1. Our results show the following: (1) The C/O and Fe/O ratios are similar to the corresponding values measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions of 1994-1997 and 2005. (2) During periods of increased solar activity between 1998 and 2002, the C/O ratio is similar to that measured in solar energetic particle (SEP) events, while the Fe/O ratio lies between the values measured in coronal mass …
The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason
The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason
Aerospace, Physics, and Space Science Faculty Publications
The mean free path is widely used to measure the level of solar energetic particles' diffusive transport. We model a solar energetic particle event observed by Wind STEP at 0.31-0.62 MeV nucleonˉ¹, by solving the focused transport equation using the Markov stochastic process theory. With different functions of the pitch angle diffusion coefficient D μμ, we obtain different parallel mean free paths for the same event. We show that the different values of the mean free path are due to the high anisotropy of the solar energetic particles. This makes it problematic to use just the mean free path to …
The Ccompton-Getting Effect Of Energetic Particles With An Anisotropic Pitch-Angle Distribution: An Application To Voyager 1 Results At ∼85 Au, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
This paper provides a theoretical simulation of anisotropy measurements by the Low-Energy Charged Particle (LECP) experiment on Voyager. The model starts with an anisotropic pitch-angle distribution function in the solar wind plasma reference frame. It includes the effects of both Compton-Getting anisotropy and a perpendicular diffusion anisotropy that possibly exists in the upstream region of the termination shock. The calculation is directly applied to the measurements during the late 2002 particle event seen by Voyager 1. It is shown that the data cannot rule out either the model with zero solar wind speed or the one with a finite speed …
Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul
Interplanetary Transport Mechanisms Of Solar Energetic Particles, Gang Qin, Ming Zhang, Joseph R. Dwyer, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
Numerical simulations of charged particle trajectories in a Parker field with model turbulence are used to study the transport mechanisms of solar energetic particles (SEPs): magnetic focusing, pitch-angle diffusive transport due to magnetic fluctuations, and adiabatic cooling. The results of the simulations are compared with analytical formulae for the transport effects. We find that adiabatic cooling is significant for SEPs traveling from the Sun to 1 AU. The simulation results agree much better with the anisotropic adiabatic cooling effect theory than with the isotropic one. Also, we show that the simulation results agree well with the theory of magnetic focusing …
Abundances Of Heavy And Ultraheavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer, Jack Randy Jokipii, Robert E. Gold, Stamatios M. Krimigis
Abundances Of Heavy And Ultraheavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer, Jack Randy Jokipii, Robert E. Gold, Stamatios M. Krimigis
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed ³He-rich solar energetic particle (SEP) events over the period 1997 September-2003 April in order to characterize abundances of heavy ions near 400 keV nucleonˉ¹. The first part of the study focuses on 20 distinct SEP events that show the previously observed pattern in which, relative to O, heavy ions through Fe are enriched, with the enrichment increasing with mass. We find that these enrichments are well correlated such that ³He-rich SEP events with high Fe/C also show larger enrichments in other heavy ions. Ultraheavy (UH; taken as 78-220 amu) ions are routinely seen in these events with …
Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug
Evidence For A Suprathermal Seed Population Of Heavy Ions Accelerated By Interplanetary Shocks Near 1 Au, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Charles W. Smith, Ruth M. Skoug
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed the 0.1-10 MeV nucleonˉ¹ elemental abundances at 72 interplanetary (IP) shocks observed by the Ultra-Low-Energy Isotope Spectrometer on board the Advanced Composition Explorer from 1997 October through 2002 September. We find the following: (1) The C/O ratios in IP shocks were substantially depleted (by more than ∼40%) relative to solar wind values. (2) The IP shock abundances were poorly correlated with those measured in the slow and fast solar wind. (3) Energetic ions above ∼0.1 MeV nucleonˉ¹ from impulsive and gradual solar energetic particle events (SEPs) were present upstream of all the IP shocks in our survey. …
Spectral Properties Of He And Heavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph R. Dwyer
Spectral Properties Of He And Heavy Ions In ³He-Rich Solar Flares, Glenn M. Mason, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
Using advanced instrumentation on the ACE spacecraft, we have conducted a survey of solar energetic particle spectra in ³He-rich events over a broad energy range ∼80 keV nucleon-1 to 15 MeV nucleonˉ¹ during the period 1997 September-2001 March. The spectra of ⁴He and heavy ions (C, N, O, Ne, Mg, Si, S, Ca, Fe) were generally similar over this range but often hardened below ∼1 MeV nucleonˉ¹. In most of the events there was even stronger hardening of the ³He spectrum below ∼1 MeV nucleonˉ¹, leading to an energy-dependent ³He: ⁴He ratio. These observations point to unique and distinct properties …
A New Heavy Ion Abundance Enrichment Pattern In ³He-Rich Solar Particle Events, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
A New Heavy Ion Abundance Enrichment Pattern In ³He-Rich Solar Particle Events, Glenn M. Mason, Joseph E. Mazur, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
We report the first examples of ³He-rich solar energetic particle (SEP) events with heavy ion enrichments that are not ordered generally by mass. A second new feature is the large enrichment of ¹⁴N, the first time large enrichments have been seen for heavy ions lighter than O or Ne. These SEP events were too small and at too low an energy (<500 keV nucleon-1) to have been observed previously. The best observed event, 2001 July 16, had abundance ratios C : N : O : Ne : Mg : Si : S : Ca : Fe of ∼0.8 : 1.0 : ≡ 1 : 0.5 : 0.5 : 2.0 : 2.4 : 0.2 : 0.9, corresponding, respectively, to enhancements over the slow solar wind of ∼1.2 :15 : ≡ 1 : 5. : 3.4 : 12 :49 : 19 : 7. This pattern is incompatible with a gravitational settling enrichment mechanism. The simultaneous large enhancements of ¹⁴N and ²⁸Si, which have identical charge-to-mass ratios for certain ionization states, suggest that selective plasma wave heating plays a key role, as has long been suspected. Enhancement of ¹⁴N implies relatively low temperatures (<1.5 × 10 6 K) since fully stripped ¹⁴N cannot be preferentially heated. Also, the presence of enhanced species such as ¹⁴N and ²⁸Si, along with others with small or no enhancements ( 16)O, ²⁰Ne), may indicate that the plasma waves must operate over a relatively narrow range of frequencies and that the material must be heated while the waves are present.
Isotopic Composition Of Solar Energetic Particle Events Measured By Advanced Composition Explorer/Uleis, Joseph R. Dwyer, Glenn M. Mason, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Eberhard S. Möbius, Mark A. Popecki
Isotopic Composition Of Solar Energetic Particle Events Measured By Advanced Composition Explorer/Uleis, Joseph R. Dwyer, Glenn M. Mason, Joseph E. Mazur, Robert E. Gold, Stamatios M. Krimigis, Eberhard S. Möbius, Mark A. Popecki
Aerospace, Physics, and Space Science Faculty Publications
Since its 1997 August launch, the Ultra Low Energy Isotope Spectrometer (ULEIS) on board the Advanced Composition Explorer (ACE) has observed a large number of solar energetic particle (SEP) events in the 0.4-3 MeV nucleonˉ¹ range. These events show remarkable variability of both the elemental and isotopic compositions, with ²²Ne/²⁰Ne varying, from event to event, by up to a factor of 10, Fe/O by up to a factor of 100, and ³He/⁴He by up to a factor of 104. In this paper we present new measurements of the ²²Ne/²⁰Ne, ²⁶Mg/²⁴Mg, and ³He/⁴He ratios at ∼ 1 MeV nucleonˉ¹ and compare …
Acceleration Of ³He Nuclei At Interplanetary Shocks, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Charles W. Smith, Ruth M. Skoug
Acceleration Of ³He Nuclei At Interplanetary Shocks, Mihir I. Desai, Glenn M. Mason, Joseph R. Dwyer, Joseph E. Mazur, Charles W. Smith, Ruth M. Skoug
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed the 0.5-2.0 MeV nucleonˉ¹ ion composition of 56 interplanetary (IP) shocks observed with the Ultra - Low-Energy Isotope Spectrometer on board the Advanced Composition Explorer from 1997 October 1 through 2000 November 30. Our results show the first ever measurement (25 cases) of ³He ions being accelerated at IP shocks. The ³He/⁴He ratio at the 25 shocks exhibited a wide range of values between 0.0014 and 0.24; the ratios were enhanced between factors of ∼3 and 600 over the solar wind value. During the survey period, the occurrence probability of ³He-rich shocks increased with rising solar activity …