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1. Modeling the effectiveness of shielding in the earth-moon-mars radiation environment using PREDICCS: five solar events in 2012

Author

Quinn Philip R., Schwadron Nathan A., Townsend Larry W., Wimmer-Schweingruber Robert F., Case Anthony W., Spence Harlan E., Wilson Jody K., and Joyce Colin J.

Subjects
Mars, Moon, Radiation environment, Human exploration, Exposure, Meteorology. Climatology, QC851-999
Abstract

Radiation in the form of solar energetic particles (SEPs) presents a severe risk to the short-term health of astronauts and the success of human exploration missions beyond Earth’s protective shielding. Modeling how shielding mitigates the dose accumulated by astronauts is an essential step toward reducing these risks. PREDICCS (Predictions of radiation from REleASE, EMMREM, and Data Incorporating the CRaTER, COSTEP, and other SEP measurements) is an online tool for the near real-time prediction of radiation exposure at Earth, the Moon, and Mars behind various levels of shielding. We compare shielded dose rates from PREDICCS with dose rates from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard the Lunar Reconnaissance Orbiter (LRO) at the Moon and from the Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) during its cruise phase to Mars for five solar events in 2012 when Earth, MSL, and Mars were magnetically well connected. Calculations of the accumulated dose demonstrate a reasonable agreement between PREDICCS and RAD ranging from as little as 2% difference to 54%. We determine mathematical relationships between shielding levels and accumulated dose. Lastly, the gradient of accumulated dose between Earth and Mars shows that for the largest of the five solar events, lunar missions require aluminum shielding between 1.0 g cm−2 and 5.0 g cm−2 to prevent radiation exposure from exceeding the 30-day limits for lens and skin. The limits were not exceeded near Mars.

Published
2017
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2. Anomalous Cosmic Ray Oxygen Observations in to 0.1 au

Author

Rankin, Jamie S., McComas, David J., Leske, Richard A., Christian, Eric R., Cohen, Christina M. S., Cummings, Alan C., Joyce, Colin J., Labrador, Allan W., Mewaldt, Richard A., Schwadron, Nathan A., Stone, Edward C., Strauss, R. Du Toit, and Wiedenbeck, Mark E.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Space Physics
Abstract

The Integrated Science Investigation of the Sun instrument suite onboard NASA's Parker Solar Probe mission continues to measure solar energetic particles and cosmic rays closer to the Sun than ever before. Here, we present the first observations of cosmic rays into 0.1 au (21.5 solar radii), focusing specifically on oxygen from ~2018.7 to ~2021.2. Our energy spectra reveal an anomalous cosmic ray-dominated profile that is comparable to that at 1 au, across multiple solar cycle minima. The galactic cosmic ray-dominated component is similar to that of the previous solar minimum (Solar Cycle 24/25 compared to 23/24) but elevated compared to the past (Solar Cycle 20/21). The findings are generally consistent with the current trend of unusually weak solar modulation that originated during the previous solar minimum and continues today. We also find a strong radial intensity gradient: 49.4 +/- 8.0 %/au from 0.1 to 0.94 au, for energies of 6.9 to 27 MeV/nuc. This value agrees with that measured by Helios nearly 45 years ago from 0.3 to 1.0 au (48 +/- 12 %/au; 9 to 29 MeV/nuc) and is larger than predicted by models. The large ACR gradients observed close to the Sun by the Parker Solar Probe Integrated Science Investigation of the Sun instrument suite found here suggest that intermediate-scale variations in the magnetic field's structure strongly influences cosmic ray drifts, well inside 1 au.

Published
2021
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5. Particle Radiation Sources, Propagation and Interactions in Deep Space, at Earth, the Moon, Mars, and Beyond: Examples of Radiation Interactions and Effects

Author

Schwadron, Nathan A., primary, Cooper, John F., additional, Desai, Mihir, additional, Downs, Cooper, additional, Gorby, Matt, additional, Jordan, Andrew P., additional, Joyce, Colin J., additional, Kozarev, Kamen, additional, Linker, Jon A., additional, Mikíc, Zoran, additional, Riley, Pete, additional, Spence, Harlan E., additional, Török, Tibor, additional, Townsend, Lawrence W., additional, Wilson, Jody K., additional, and Zeitlin, Cary, additional

Published
2017
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6. Magnetic Waves Excited by Newborn Pickup H + Near Jupiter: Neutral Hydrogen Loss by the Planetary System

Author

Hollick, Sophia J., primary, Smith, Charles W., additional, Pine, Zackary B., additional, Argall, Matthew R., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, Kubiak, Marzena A., additional, Bagenal, F., additional, and Richardson, John D., additional

Published
2022
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7. High-latitude Observations of Inertial-range Turbulence by the Ulysses Spacecraft During the Solar Minimum of 1993–96

Author

Watson, Abigale S., primary, Smith, Charles W., additional, Marchuk, Anastasia V., additional, Argall, Matthew R., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Bzowski, Maciej, additional, Kubiak, Marzena A., additional, and Murphy, Neil, additional

Published
2022
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9. New Data from the ISʘIS instrument Suite on Parker Solar Probe

Author

Christian, Eric, primary, Cohen, Christina, additional, Cummings, Alan C., additional, Davis, Andrew, additional, Desai, Mihir, additional, De Nolfo, Georgia A., additional, Giacalone, Joseph, additional, Hill, Matt E., additional, Joyce, Colin J., additional, Labrador, Allan, additional, Leske, Rick A., additional, Matthaeus, William, additional, McComas, David, additional, McNutt Jr., Ralph L., additional, Mewaldt, Richard Alvin, additional, Mitchell, Donald G., additional, Mitchell, J. W., additional, Rankin, Jamie, additional, Roelof, Edmond C., additional, Schwadron, Nathan, additional, Stone, Edward C., additional, Szalay, Jamey, additional, and Wiedenbeck, Mark, additional

Published
2021
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11. Magnetic Waves Excited by Newborn Pickup H+ Near Jupiter: Neutral Hydrogen Loss by the Planetary System.

Author

Hollick, Sophia J., Smith, Charles W., Pine, Zackary B., Argall, Matthew R., Joyce, Colin J., Isenberg, Philip A., Vasquez, Bernard J., Schwadron, Nathan A., Sokół, Justyna M., Bzowski, Maciej, Kubiak, Marzena A., Bagenal, F., and Richardson, John D.

Subjects
PLANETARY systems, SOLAR wind, FLUXGATE magnetometers, JUPITER (Planet), CHARGE exchange, WIND waves
Abstract

We report here observations of magnetic waves recorded by the Voyager spacecraft in the solar wind near Jupiter that are possibly the result of excitation by newborn pickup H+. Consideration of growth rates due to the known interstellar ion sources strongly disfavor an interstellar source. To determine the likely source of the waves, we compute the minimum ion production rate by equating wave growth to turbulent cascade rates and derive a lower limit for the production of H+ at the times of observations. The only available source of neutral H at these times and at the levels required is the Jovian system, most notably charge exchange between energetic protons and the neutral clouds around Io and Europa's orbits. Further refinement of the source identity is not possible at this time. We provide an estimate for the neutral H source subject to assumptions of the latitudinal extent of the population which is not constrained by observation. Plain Language Summary: The Voyager spacecraft instruments include a fluxgate magnetometer called MAG that measures the changing ambient magnetic field. We report observations by MAG of low‐frequency waves in the solar wind outside the Jovian magnetosphere that are seen at frequencies and with characteristics that suggest the waves are excited by protons that originate as neutral hydrogen. Collision with solar wind protons ionize the neutral hydrogen to produce an energetic ion population called pickup ions. We use known characteristics of wave excitation by pickup ions to estimate the rate of pickup ion production. The only source that is strong enough to produce the pickup ions with the number density required is the Jovian system. Key Points: Magnetic waves were measured by Voyagers 1 and 2 in the solar wind near the magnetosphere of JupiterThese waves have signatures of excitation by local pickup H+ ionsA neutral H loss rate of ∼5 × 1028 s−1 from the Jovian system is estimated [ABSTRACT FROM AUTHOR]

Published
2022
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12. Solar Wind Turbulence from 1 to 45 au. III. Anisotropy of Magnetic Fluctuations in the Inertial Range Using Voyager and ACE Observations

Author

Pine, Zackary B., primary, Smith, Charles W., additional, Hollick, Sophia J., additional, Argall, Matthew R., additional, Vasquez, Bernard J., additional, Isenberg, Philip A., additional, Schwadron, Nathan A., additional, Joyce, Colin J., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, Kubiak, Marzena A., additional, Hamilton, Kathleen E., additional, McLaurin, Megan L., additional, and Leamon, Robert J., additional

Published
2020
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13. Solar Wind Turbulence from 1 to 45 au. I. Evidence for Dissipation of Magnetic Fluctuations Using Voyager and ACE Observations

Author

Pine, Zackary B., primary, Smith, Charles W., additional, Hollick, Sophia J., additional, Argall, Matthew R., additional, Vasquez, Bernard J., additional, Isenberg, Philip A., additional, Schwadron, Nathan A., additional, Joyce, Colin J., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, Kubiak, Marzena A., additional, Hamilton, Kathleen E., additional, McLaurin, Megan L., additional, and Leamon, Robert J., additional

Published
2020
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14. Solar Wind Turbulence from 1 to 45 au. IV. Turbulent Transport and Heating of the Solar Wind Using Voyager Observations

Author

Pine, Zackary B., primary, Smith, Charles W., additional, Hollick, Sophia J., additional, Argall, Matthew R., additional, Vasquez, Bernard J., additional, Isenberg, Philip A., additional, Schwadron, Nathan A., additional, Joyce, Colin J., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, Kubiak, Marzena A., additional, and McLaurin, Megan L., additional

Published
2020
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15. Observation of Bernstein Waves Excited by Newborn Interstellar Pickup Ions in the Solar Wind

Author

Joyce, Colin J, Smith, Charles W, Isenberg, Philip A, Gary, S. Peter, Murphy, Neil, Gray, Perry C, and Burlaga, Leonard F

Subjects
Solar Physics
Abstract

A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.

Published
2012
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16. Solar Wind Turbulence from 1 to 45 au. II. Analysis of Inertial-range Fluctuations Using Voyager and ACE Observations.

Author

Pine, Zackary B., Smith, Charles W., Hollick, Sophia J., Argall, Matthew R., Vasquez, Bernard J., Isenberg, Philip A., Schwadron, Nathan A., Joyce, Colin J., Sokół, Justyna M., Bzowski, Maciej, Kubiak, Marzena A., Hamilton, Kathleen E., McLaurin, Megan L., and Leamon, Robert J.

Subjects
MAGNETIC field measurements, PLASMA waves, SOLAR wind, TURBULENCE, EXPLORERS, POWER spectra
Abstract

We examine both Voyager and Advanced Composition Explorer magnetic field measurements at frequencies that characterize the inertial range using traditional polarization techniques that are designed to characterize plasma waves. Although we find good agreement with both the anticipated spectral index of the power spectrum and the scaling of magnetic power with heliocentric distance, we do not find that the polarization analyses yield results that can be readily described by plasma wave theory. The fluctuations are not circularly polarized and there is a markedly reduced coherence between the components of the fluctuation. The degree of polarization is also generally low, although not as low as the coherence, and the minimum variance direction is essentially random. We conclude that traditional plasma wave theory may not offer a good description for inertial-range fluctuations. [ABSTRACT FROM AUTHOR]

Published
2020
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18. Magnetic Waves Excited by Newborn Interstellar Pickup Ions Measured by the Voyager Spacecraft from 1 to 45 au. III. Observation Times

Author

Hollick, Sophia J., primary, Smith, Charles W., additional, Pine, Zackary B., additional, Argall, Matthew R., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, and Kubiak, Marzena A., additional

Published
2018
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19. Magnetic Waves Excited by Newborn Interstellar Pickup Ions Measured by the Voyager Spacecraft from 1 to 45 au. II. Instability and Turbulence Analyses

Author

Hollick, Sophia J., primary, Smith, Charles W., additional, Pine, Zackary B., additional, Argall, Matthew R., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, and Kubiak, Marzena A., additional

Published
2018
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20. Magnetic Waves Excited by Newborn Interstellar Pickup Ions Measured by the Voyager Spacecraft from 1 to 45 au. I. Wave Properties

Author

Hollick, Sophia J., primary, Smith, Charles W., additional, Pine, Zackary B., additional, Argall, Matthew R., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, and Kubiak, Marzena A., additional

Published
2018
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21. Opening a Window on ICME-driven GCR Modulation in the Inner Solar System

Author

Winslow, Reka M., primary, Schwadron, Nathan A., additional, Lugaz, Noé, additional, Guo, Jingnan, additional, Joyce, Colin J., additional, Jordan, Andrew P., additional, Wilson, Jody K., additional, Spence, Harlan E., additional, Lawrence, David J., additional, Wimmer-Schweingruber, Robert F., additional, and Mays, M. Leila, additional

Published
2018
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22. Erratum: “Observation of Magnetic Waves Excited by Newborn Interstellar Pickup He+ Observed by the Voyager 2 Spacecraft at 30 au” (2017, ApJ, 849, 61)

Author

Argall, Matthew R., primary, Hollick, Sophia J., additional, Pine, Zackary B., additional, Smith, Charles W., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, and Burlaga, Leonard F., additional

Published
2018
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23. Observation of Magnetic Waves Excited by Newborn Interstellar Pickup He+ Observed by theVoyager 2Spacecraft at 30 au

Author

Argall, Matthew R., primary, Hollick, Sophia J., additional, Pine, Zackary B., additional, Smith, Charles W., additional, Joyce, Colin J., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, and Burlaga, Leonard F., additional

Published
2017
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24. Observations of Low-Frequency Magnetic Waves due to Newborn Interstellar Pickup Ions Using ACE, Ulysses, and Voyager Data

Author

Smith, Charles W., primary, Aggarwal, Poornima, additional, Argall, Matthew R., additional, Burlaga, Leonard F., additional, Bzowski, Maciej, additional, Cannon, Bradford E., additional, Peter Gary, S., additional, Fisher, Meghan K., additional, Gilbert, Jason A., additional, Hollick, Sophia J., additional, Isenberg, Philip A., additional, Joyce, Colin J., additional, Murphy, Neil, additional, Nuno, Raquel G., additional, Pine, Zackary B., additional, Richardson, John D., additional, Schwadron, Nathan A., additional, Skoug, Ruth M., additional, Sokół, Justyna M., additional, Taylor, David K., additional, and Vasquez, Bernard J., additional

Published
2017
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26. VOYAGER OBSERVATIONS OF MAGNETIC WAVES DUE TO NEWBORN INTERSTELLAR PICKUP IONS: 2–6 au

Author

MIT Kavli Institute for Astrophysics and Space Research, Richardson, John D, Aggarwal, Poornima, Taylor, David K., Smith, Charles W., Joyce, Colin J., Fisher, Meghan K., Isenberg, Philip A., Vasquez, Bernard J., Schwadron, Nathan A., Cannon, Bradford E., Richardson, John D., MIT Kavli Institute for Astrophysics and Space Research, Richardson, John D, Aggarwal, Poornima, Taylor, David K., Smith, Charles W., Joyce, Colin J., Fisher, Meghan K., Isenberg, Philip A., Vasquez, Bernard J., Schwadron, Nathan A., Cannon, Bradford E., and Richardson, John D.

Abstract

We report observations by the Voyager 1 and 2 spacecraft of low-frequency magnetic waves excited by newborn interstellar pickup ions H⁺ and He⁺ during 1978–1979 when the spacecraft were in the range from 2 to 6.3 au. The waves have the expected association with the cyclotron frequency of the source ions, are left-hand polarized in the spacecraft frame, and have minimum variance directions that are quasi-parallel to the local mean magnetic field. There is one exception to this in that one wave event that is excited by pickup H+ is right-hand polarized in the spacecraft frame, but similar exceptions have been reported by Cannon et al. and remain unexplained. We apply the theory of Lee & Ip that predicts the energy spectrum of the waves and then compare growth rates with turbulent cascade rates under the assumption that turbulence acts to destroy the enhanced wave activity and transport the associated energy to smaller scales where dissipation heats the background plasma. As with Cannon et al., we find that the ability to observe the waves depends on the ambient turbulence being weak when compared with growth rates, thereby allowing sustained wave growth. This analysis implies that the coupled processes of pitch-angle scattering and wave generation are continuously associated with newly ionized pickup ions, despite the fact that the waves themselves may not be directly observable. When waves are not observed, but wave excitation can be argued to be present, the wave energy is simply absorbed by the turbulence at a rate that prevents significant accumulation. In this way, the kinetic process of wave excitation by scattering of newborn ions continues to heat the plasma without producing observable wave energy. These findings support theoretical models that invoke efficient scattering of new pickup ions, leading to turbulent driving in the outer solar wind and in the IBEX ribbon beyond the heliopause., University of New Hampshire (Caltech subcontract 44A1085631), United States. National Aeronautics and Space Administration (grant NNX13AF97G), United States. National Aeronautics and Space Administration (grant NNX11AJ37G), National Science Foundation (U.S.) (grant AGS0962506), National Science Foundation (U.S.) (grant AGS1357893)

Published
2016

27. A SURVEY OF MAGNETIC WAVES EXCITED BY NEWBORN INTERSTELLAR He+OBSERVED BY THEACESPACECRAFT AT 1 au

Author

Fisher, Meghan K., primary, Argall, Matthew R., additional, Joyce, Colin J., additional, Smith, Charles W., additional, Isenberg, Philip A., additional, Vasquez, Bernard J., additional, Schwadron, Nathan A., additional, Skoug, Ruth M., additional, Sokół, Justyna M., additional, Bzowski, Maciej, additional, Zurbuchen, Thomas H., additional, and Gilbert, Jason A., additional

Published
2016
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36. Ulysses and Voyager Observations of Waves Due to Interstellar Pickup H+ and He+.

Author

Smith, Charles W., Isenberg, Philip A., Joyce, Colin J., Cannon, Bradford E., Murphy, Neil, Nuno, Raquel G., and Schwadron, Nathan A.

Subjects
ASTRONOMICAL observations, WAVES (Physics), INTERSTELLAR hydrogen, HELIUM, OPTICAL polarization, SCATTERING (Physics), ASTROPHYSICS
Abstract

Interstellar pickup ions, in scattering to isotropy, should generate waves in particular frequency ranges, but observations of such waves are very rare. To date, only proton-generated waves at Ulysses have been reported, and only sporadically during times of quasi-radial field. Here, we present two sets of wave observations. The first set are waves due to pickup H+ seen by the Ulysses spacecraft as part of a new study to gather and build a data base of observations that can better be questioned regarding the fundamental physics of wave generation by interstellar pickup ions. There we demonstrate that the waves may have small signatures in the power spectrum while showing strong evidence of wave-particle dynamics in the polarization spectra. The second set is a spectral enhancement measured at the Voyager 2 spacecraft during 4.5 hours on DOY 7, 1979 at a heliocentric radial position of 4.5 AU. The large-scale IMF was nearly radial, and the frequency range and polarization of the enhanced fluctuations are consistent with pickup ion-generated waves from inflowing interstellar H and He. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves on any spacecraft, and prompts further searches for such waves in data sets closer to the Sun. [ABSTRACT FROM AUTHOR]

Published
2010
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37. Magnetic Waves Excited by Newborn Pickup H+Near Jupiter: Neutral Hydrogen Loss by the Planetary System

Author

Hollick, Sophia J., Smith, Charles W., Pine, Zackary B., Argall, Matthew R., Joyce, Colin J., Isenberg, Philip A., Vasquez, Bernard J., Schwadron, Nathan A., Sokół, Justyna M., Bzowski, Maciej, Kubiak, Marzena A., Bagenal, F., and Richardson, John D.

Abstract

We report here observations of magnetic waves recorded by the Voyager spacecraft in the solar wind near Jupiter that are possibly the result of excitation by newborn pickup H+. Consideration of growth rates due to the known interstellar ion sources strongly disfavor an interstellar source. To determine the likely source of the waves, we compute the minimum ion production rate by equating wave growth to turbulent cascade rates and derive a lower limit for the production of H+at the times of observations. The only available source of neutral H at these times and at the levels required is the Jovian system, most notably charge exchange between energetic protons and the neutral clouds around Io and Europa's orbits. Further refinement of the source identity is not possible at this time. We provide an estimate for the neutral H source subject to assumptions of the latitudinal extent of the population which is not constrained by observation. The Voyager spacecraft instruments include a fluxgate magnetometer called MAG that measures the changing ambient magnetic field. We report observations by MAG of low‐frequency waves in the solar wind outside the Jovian magnetosphere that are seen at frequencies and with characteristics that suggest the waves are excited by protons that originate as neutral hydrogen. Collision with solar wind protons ionize the neutral hydrogen to produce an energetic ion population called pickup ions. We use known characteristics of wave excitation by pickup ions to estimate the rate of pickup ion production. The only source that is strong enough to produce the pickup ions with the number density required is the Jovian system. Magnetic waves were measured by Voyagers 1 and 2 in the solar wind near the magnetosphere of JupiterThese waves have signatures of excitation by local pickup H+ionsA neutral H loss rate of ∼5 × 1028s−1from the Jovian system is estimated Magnetic waves were measured by Voyagers 1 and 2 in the solar wind near the magnetosphere of Jupiter These waves have signatures of excitation by local pickup H+ions A neutral H loss rate of ∼5 × 1028s−1from the Jovian system is estimated

Published
2022
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40. EXCITATION OF LOW-FREQUENCY WAVES IN THE SOLAR WIND BY NEWBORN INTERSTELLAR PICKUP IONS H+ AND He+ AS SEEN BY VOYAGER AT 4.5 AU

Author

Joyce, Colin J., Smith, Charles W., Isenberg, Philip A., Murphy, Neil, and Schwadron, Nathan A.

Abstract

We report the observation of a spectral enhancement in the magnetic field fluctuations measured by the MAG instrument on the Voyager 2 spacecraft during 4.5 hr on DOY 7, 1979 at a heliocentric radial position of 4.5 AU. This time period is contained within a solar wind rarefaction when the large-scale interplanetary magnetic field was nearly radial. The frequency range and polarization of the enhanced fluctuations are consistent with waves generated by newly ionized interstellar H+ and He+. We show sunward propagation of the waves via a cross-helicity analysis. We compare the observation with a theoretical model and find reasonable agreement given the model assumptions. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves by any spacecraft.

Published
2010

42. ULYSSES OBSERVATIONS OF MAGNETIC WAVES DUE TO NEWBORN INTERSTELLAR PICKUP IONS. II. APPLICATION OF TURBULENCE CONCEPTS TO LIMITING WAVE ENERGY AND OBSERVABILITY.

Author

Cannon, Bradford E., Smith, Charles W., Isenberg, Philip A., Vasquez, Bernard J., Joyce, Colin J., Murphy, Neil, and Nuno, Raquel G.

Subjects
INTERSTELLAR magnetic fields, INTERSTELLAR medium, QUASILINEARIZATION, HELIOSPHERE, WAVE energy
Abstract

The low-frequency magnetic waves that arise from the isotropization of newborn interstellar pickup ions (PUIs) are reasonably well described by linear and quasi-linear kinetic theory in so far as those theories predict the wave frequency and polarization in the spacecraft frame. Those theories fail to describe the scarce observability of the waves. Quasilinear theory predicts that the wave power should accumulate over long periods of time as the relatively weak kinetic instability slowly adds power to the observed spectrum. At the same time it has been argued that the same wave energy must serve as a secondary source of thermal ion heating in the outer heliosphere once the initial turbulence is depleted. To the extent that turbulent transport of the wave energy acts against the spectrally confined accumulation of wave energy, turbulence should be a limiting factor in observability. We argue that turbulence does limit the observability of the waves and we use turbulence theory to predict the observed wave energy. We compare this prediction against a database of 502 wave observations attributed to newborn interstellar PUIs observed by the Ulysses spacecraft. [ABSTRACT FROM AUTHOR]

Published
2014
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43. Ulysses and Voyager Observations of Waves Due to Interstellar Pickup H+ and He+.

Author

Smith, Charles W., Isenberg, Philip A., Joyce, Colin J., Cannon, Bradford E., Murphy, Neil, Nuno, Raquel G., and Schwadron, Nathan A.

Subjects
*ASTRONOMICAL observations, *WAVES (Physics), *INTERSTELLAR hydrogen, *HELIUM, *OPTICAL polarization, *SCATTERING (Physics), *ASTROPHYSICS
Abstract

Interstellar pickup ions, in scattering to isotropy, should generate waves in particular frequency ranges, but observations of such waves are very rare. To date, only proton-generated waves at Ulysses have been reported, and only sporadically during times of quasi-radial field. Here, we present two sets of wave observations. The first set are waves due to pickup H+ seen by the Ulysses spacecraft as part of a new study to gather and build a data base of observations that can better be questioned regarding the fundamental physics of wave generation by interstellar pickup ions. There we demonstrate that the waves may have small signatures in the power spectrum while showing strong evidence of wave-particle dynamics in the polarization spectra. The second set is a spectral enhancement measured at the Voyager 2 spacecraft during 4.5 hours on DOY 7, 1979 at a heliocentric radial position of 4.5 AU. The large-scale IMF was nearly radial, and the frequency range and polarization of the enhanced fluctuations are consistent with pickup ion-generated waves from inflowing interstellar H and He. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves on any spacecraft, and prompts further searches for such waves in data sets closer to the Sun. [ABSTRACT FROM AUTHOR]

Published
2010
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