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Full-Text Articles in Physical Sciences and Mathematics
Effects Of Coronal Magnetic Field Structures On The Transport Of Solar Energetic Particles, Lulu Zhao, Ming Zhang
Effects Of Coronal Magnetic Field Structures On The Transport Of Solar Energetic Particles, Lulu Zhao, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
This Letter presents a model calculation of solar energetic particle (SEP) transport to test the sensitivity of the distribution of escaped SEPs in interplanetary space and dependence upon the details of the magnetic field structure in the corona. It is applied to a circumsolar event on 2011 November 3, in which SEPs are observed promptly after the solar event eruption by three spacecraft (the twin Solar TErrestrial RElations Observatories (STEREO-A and STEREO-B) and ACE) separated by more than 100° in longitude from each other. The corona magnetic field reconstructed from photosphseric field measurements using the PFSS method changes substantially before …
Double Power Laws In The Event-Integrated Solar Energetic Particle Spectrum, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
Double Power Laws In The Event-Integrated Solar Energetic Particle Spectrum, Lulu Zhao, Ming Zhang, Hamid K. Rassoul
Aerospace, Physics, and Space Science Faculty Publications
A double power law or a power law with exponential rollover at a few to tens of MeV nucleon−1 of the eventintegrated differential spectra has been reported in many solar energetic particle (SEP) events. The rollover energies per nucleon of different elements correlate with a particleʼs charge-to-mass ratio (Q/A). The probable causes are suggested as residing in shock finite lifetimes, shock finite sizes, shock geometry, and an adiabatic cooling effect. In this work, we conduct a numerical simulation to investigate a particleʼs transport process in the inner heliosphere. We solve the focused transport equation using a time-backward Markov stochastic approach. …
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 …
Propagation Of Solar Energetic Particles In Three-Dimensional Interplanetary Magnetic Fields: In View Of Characteristics Of Sources, H. Q. He, Gang Qin, Ming Zhang
Propagation Of Solar Energetic Particles In Three-Dimensional Interplanetary Magnetic Fields: In View Of Characteristics Of Sources, H. Q. He, Gang Qin, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
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 …
Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur
Composition And Spectral Properties Of The 1 Au Quiet-Time Superthermal Ion Population During Solar Cycle 23, M. A. Dayeh, M. I. Desai, Joseph R. Dwyer, Hamid K. Rassoul, G. M. Mason, J. E. Mazur
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed the spectral and compositional properties of suprathermal heavy ions during quiet times from 1995 January 1 to 2007 December 31 using Wind/Energetic Particles: Anisotropy, Composition, and Transport/SupraThermal-through-Energetic Particle Telescope and Advanced Composition Explorer/Ultra-low Energy Isotope Spectrometer at energies between 0.04 and 2.56 MeV nucleon−1. We find the following. (1) Quiet-time Fe/O and C/O abundances are correlated with solar cycle activity, reflecting corresponding values measured in solar energetic particle and interplanetary (IP) shock events during solar maximum, and those measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions. (2) The 3He/4He ratio lies …
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 …
Study Of The Solar Anisotropy Of Cosmic Ray Primaries Of About 200 Gev Energy With The L3+C Muon Detector, G Baksay, L Baksay, K Dehmelt, M Hohlmann, Z Szillasi, I Vodopianov, The L3 Collaboration
Study Of The Solar Anisotropy Of Cosmic Ray Primaries Of About 200 Gev Energy With The L3+C Muon Detector, G Baksay, L Baksay, K Dehmelt, M Hohlmann, Z Szillasi, I Vodopianov, The L3 Collaboration
Aerospace, Physics, and Space Science Faculty Publications
Context. Primary cosmic rays experience multiple deflections in the non-uniform galactic and heliospheric magnetic fields which may generate anisotropies. Aims. A study of anisotropies in the energy range between 100 and 500 GeV is performed. This energy range is not yet well explored. Methods. The L3 detector at the CERN electron-positron collider, LEP, is used for a study of the angular distribution of atmospheric muons with energies above 20 GeV. This distribution is used to investigate the isotropy of the time-dependent intensity of the primary cosmic-ray flux with a Fourier analysis. Results. A small deviation from isotropy at energies around …
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 …
The Role Of Interplanetary Scattering In Western Hemisphere Large Solar Energetic Particle Events, Glenn M. Mason, Mihir I. Desai, Christina M.S. Cohen, Richard A. Mewaldt, Edward C. Stone, Joseph R. Dwyer
The Role Of Interplanetary Scattering In Western Hemisphere Large Solar Energetic Particle Events, Glenn M. Mason, Mihir I. Desai, Christina M.S. Cohen, Richard A. Mewaldt, Edward C. Stone, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
Using high-sensitivity instruments on the ACE spacecraft, we have examined the intensities of O and Fe in 14 large solar energetic particleevents whose parent activity was in the solar western hemisphere. Sampling the intensities at low (∼273 keV nucleonˉ¹) and high (∼12 MeV nucleonˉ¹) energies, we find that at the same kinetic energy per nucleon, the Fe/O ratio decreases with time, as has been reported previously. This behavior is seen in more than 70% of the cases during the rise to maximum intensity and continues in most cases into the decay phase. We find that for most events if we …
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 …
Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer
Spectral Properties Of Heavy Ions Associated With The Passage Of Interplanetary Shocks At 1 Au, Mihir I. Desai, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
We have surveyed the energy spectra of ∼0.1-100 MeV nucleonˉ¹ C, O, and Fe nuclei associated with the passage of 72 interplanetary (IP) shocks observed on board the ACE spacecraft during the period 1997 October-2002 October. Our main results are as follows: (1) The spectral fit parameters are independent of the local shock properties. (2) About 7% of the events exhibit increasing Fe/O ratios with energy; the remaining events have Fe/O ratios that either remain constant or decrease with energy. (3) The Fe/O ratio in the shock-associated particles is typically ∼30% lower than in the ambient population. (4) The fractionation …
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 …
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 …
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 …