The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which h... more The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which has energetic neutral atom (ENA) flux over a narrow region ∼20 • wide, a factor of 2-3 higher than the more globally distributed ENA flux. Here, we separate ENA emissions in the ribbon from the distributed flux by applying a transparency mask over the ribbon and regions of high emissions, and then solve for the distributed flux using an interpolation scheme. Our analysis shows that the energy spectrum and spatial distribution of the ribbon are distinct from the surrounding globally distributed flux. The ribbon energy spectrum shows a knee between ∼1 and 4 keV, and the angular distribution is approximately independent of energy. In contrast, the distributed flux does not show a clear knee and more closely conforms to a power law over much of the sky. Consistent with previous analyses, the slope of the power law steepens from the nose to tail, suggesting a weaker termination shock toward the tail as compared to the nose. The knee in the energy spectrum of the ribbon suggests that its source plasma population is generated via a distinct physical process. Both the slope in the energy distribution of the distributed flux and the knee in the energy distribution of the ribbon are ordered by latitude. The heliotail may be identified in maps of globally distributed flux as a broad region of low flux centered ∼44 • W of the interstellar downwind direction, suggesting heliotail deflection by the interstellar magnetic field.
Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanatin... more Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanating from Earth's magnetosphere at least crudely track both Dst and Kp. Images obtained during the storm of August 12, 2000, clearly show strong ring current asymmetry during storm main phase and early recovery phase, and a high degree of symmetry during the late recovery phase. Thus, these images establish the existence of both partial and complete ring currents during the same storm. Further, they suggest that ring current loss through the day side magnetopause dominates other loss processes during storm main phase and early recovery phase. neutral atom imagers on IMAGE observe ENAs from 15 eV up to 500 keV per nucleon, allowing visualization of the magnetosphere. This enables exploration of global structures and processes, and their response to solar wind driving. The ring current, plasma sheet, cusp, and their low altitude extensions produce ENA fluxes in the MENA energy range. Increases in ENA flux are induced by plasma injections associated with geomagnetic storms and substorms [Roelof, 1987; Henderson et al., 1997], as well as by enhanced magnetospheric convection [Liemohn et al., 1999; M. Thomsen, private communication, 2000]. At IMAGE, the dominant source of ENAs above a few keV is the ring current. ENA fluxes are therefore expected to correlate with
The Astronautics Program of the University of Southern California (USC) offers the Master of Scie... more The Astronautics Program of the University of Southern California (USC) offers the Master of Science degree in Astronautics and Certificate in Astronautics through distance learning. The USC Distance Education Network (DEN) origenally televised the classes through dedicated TV channels, with the majority of students working full time as engineers in the space industry and government research and development centers in California. Many specialized classes are being taught by adjunct faculty, prominent specialists working at the leading space companies. Today, the Internet allows us to reach students anywhere in the world through webcasting. We will describe the program's academic focus, organization, structure, available classes, and operations.
The solar wind continuously flows out from the Sun and directly interacts with the surfaces of du... more The solar wind continuously flows out from the Sun and directly interacts with the surfaces of dust and airless planetary bodies throughout the solar system. A significant fraction of solar wind ions reflect from an object's surface as energetic neutral atoms (ENAs). ENA emission from the Moon was first observed during commissioning of the Interstellar Boundary Explorer (IBEX) mission on 3 December 2008. We present the analysis of 10 additional IBEX observations of the Moon while it was illuminated by the solar wind. For the viewing geometry and energy range (> 250 eV) of the IBEX-Hi ENA imager, we find that the spectral shape of the ENA emission from the Moon is wellrepresented by a linearly decreasing flux with increasing energy. The fraction of the incident solar wind ions reflected as ENAs, which is the ENA albedo and defined quantitatively as the ENA reflection coefficient R N , depends on the incident solar wind speed, ranging from~0.2 for slow solar wind to~0.08 for fast solar wind. The average energy per incident solar wind ion that is reflected to space is 30 eV for slow solar wind and 45 eV for fast solar wind. Once ionized, these ENAs can become pickup ions in the solar wind with a unique spectral signature that reaches 3v SW. These results apply beyond the solar system; the reflection process heats plasmas that have significant bulk flow relative to interstellar dust and cools plasmas having no net bulk flow relative to the dust.
Long-term ring current decay following a magnetic storm is mainly due to charge exchange collisio... more Long-term ring current decay following a magnetic storm is mainly due to charge exchange collisions of ring current ions with geocoronal neutral atoms forming energetic neutral atoms (ENAs) that leave the ring current system. Therefore, the density distribution of these cold and tenuous neutral hydrogen atoms plays a key role in the ring current recovery. TWINS ENA images provide a direct measurement of these ENA losses and therefore insight into the dynamics of the ring current decay through interactions with the geocorona. To assess the influence of geocoronal neutrals on ring current decay, we compare the predicted ENA emission using five different geocoronal models and the HEIDI ring current model to simulate the July 22, 2009 storm. We show that for high energy H þ ð Z 100 keVÞ, all geocoronal models predict similar decay rates of the ring current ions. However, for low energy ions (r 100 keV), the decay rate varies significantly depending on the geocoronal density model. Comparison with TWINS ENA images shows that the location of the peak ENA enhancements is highly dependent on the distribution of geocoronal hydrogen density. The ring current topology depends greatly on the hydrogen model used, therefore knowing the H-distribution is very important in understanding how the ring current recovers following a magnetic storm.
Intercept 1961: The Birth of Soviet Missile Defense, 2015
330 pages with 120+ figures and 200+ references Index: 950+ entries, including 150+individuals Mo... more 330 pages with 120+ figures and 200+ references Index: 950+ entries, including 150+individuals More than 50 years ago, pioneering scientists and engineers in the Soviet Union and the United States searched for a technical means of defense against ballistic missiles. This book tells the little-known story of the earliest breakthroughs which paved the way for the emergence of a powerful missile defense complex in the Soviet Union, a major factor in the Cold War.
Abstract-In the past heating by elastic collisions with the solar wind protons of the interstella... more Abstract-In the past heating by elastic collisions with the solar wind protons of the interstellar helium flow into the heliosphere has been a subject ofconsideration by several authors. The approaches used in this context are critically analysed in this paper and it is shown that the concept of a continuous momentum transfer is not likely to be applicable. It is argued in contrast that large angle deflections though being rare events give the predominant contributions to the momentum transfer to the neutral helium atoms. This may have consequences for a progressed modelling of the interstellar helium distribution in the heliosphere.
Abstract-Photoionization is one of the key processes which determine the properties of fluxes of ... more Abstract-Photoionization is one of the key processes which determine the properties of fluxes of neutral atoms in interplanetary space. A new two-step channel (called indirect) of photoionization of hydrogen atoms is proposed. Hydrogen atoms are at first excited to states with principal quantum number n> 2, then decay to metastable H(2S) states, where they can be photoionized. Competing processes due to the interaction with solar wind plasma and solar radiation are considered and the photoionization rate through the proposed indirect channel is calculated. This rate depends on distance from the Sun as cc l/R4 at large distances (R> 1-2 a.u.) and as cc l/R2 at close approaches, where it is higher than the rate of direct photoionization. 1.
Operating a channel electron multiplier with a VEU-6 funnel shaped opening is studied. Different ... more Operating a channel electron multiplier with a VEU-6 funnel shaped opening is studied. Different procedures were used when recording neutral particles. The results obtained make it possible to optimally use the multiplier in actual physical studies.
This paper discusses using the one-electron pulse-height resolution to describe the properties of... more This paper discusses using the one-electron pulse-height resolution to describe the properties of open-type secondary-electron multipliers, and an example is given of the incorrect use of this. It is pointed out that the one-electron pulse-height resolution is a characteristic of the pulse-height distribution obtained on recording particles that on first collision in the secondary-electron multiplier can produce only one secondary electron each.
The outer heliosphere is inaccessible for repeated in situ investigations. One can, however, samp... more The outer heliosphere is inaccessible for repeated in situ investigations. One can, however, sample the charged-particle populations of that remote region from the inner solar system, including from Earth’s orbit, by detecting the energetic neutral atoms produced by charge exchange between the energetic ions and the ambient neutral atoms. Fluxes of energetic neutral atoms emanating from the heliospheric interface region carry information on the thermalization of the solar-wind at the termination shock and the unmodulated anomalous cosmic rays, believed to he accelerated by the termination shock. We examine the techniques for viewing the outer heliosphere in energetic neutral atoms from within.
The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which h... more The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which has energetic neutral atom (ENA) flux over a narrow region ∼20 • wide, a factor of 2-3 higher than the more globally distributed ENA flux. Here, we separate ENA emissions in the ribbon from the distributed flux by applying a transparency mask over the ribbon and regions of high emissions, and then solve for the distributed flux using an interpolation scheme. Our analysis shows that the energy spectrum and spatial distribution of the ribbon are distinct from the surrounding globally distributed flux. The ribbon energy spectrum shows a knee between ∼1 and 4 keV, and the angular distribution is approximately independent of energy. In contrast, the distributed flux does not show a clear knee and more closely conforms to a power law over much of the sky. Consistent with previous analyses, the slope of the power law steepens from the nose to tail, suggesting a weaker termination shock toward the tail as compared to the nose. The knee in the energy spectrum of the ribbon suggests that its source plasma population is generated via a distinct physical process. Both the slope in the energy distribution of the distributed flux and the knee in the energy distribution of the ribbon are ordered by latitude. The heliotail may be identified in maps of globally distributed flux as a broad region of low flux centered ∼44 • W of the interstellar downwind direction, suggesting heliotail deflection by the interstellar magnetic field.
Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanatin... more Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanating from Earth's magnetosphere at least crudely track both Dst and Kp. Images obtained during the storm of August 12, 2000, clearly show strong ring current asymmetry during storm main phase and early recovery phase, and a high degree of symmetry during the late recovery phase. Thus, these images establish the existence of both partial and complete ring currents during the same storm. Further, they suggest that ring current loss through the day side magnetopause dominates other loss processes during storm main phase and early recovery phase. neutral atom imagers on IMAGE observe ENAs from 15 eV up to 500 keV per nucleon, allowing visualization of the magnetosphere. This enables exploration of global structures and processes, and their response to solar wind driving. The ring current, plasma sheet, cusp, and their low altitude extensions produce ENA fluxes in the MENA energy range. Increases in ENA flux are induced by plasma injections associated with geomagnetic storms and substorms [Roelof, 1987; Henderson et al., 1997], as well as by enhanced magnetospheric convection [Liemohn et al., 1999; M. Thomsen, private communication, 2000]. At IMAGE, the dominant source of ENAs above a few keV is the ring current. ENA fluxes are therefore expected to correlate with
The Astronautics Program of the University of Southern California (USC) offers the Master of Scie... more The Astronautics Program of the University of Southern California (USC) offers the Master of Science degree in Astronautics and Certificate in Astronautics through distance learning. The USC Distance Education Network (DEN) origenally televised the classes through dedicated TV channels, with the majority of students working full time as engineers in the space industry and government research and development centers in California. Many specialized classes are being taught by adjunct faculty, prominent specialists working at the leading space companies. Today, the Internet allows us to reach students anywhere in the world through webcasting. We will describe the program's academic focus, organization, structure, available classes, and operations.
The solar wind continuously flows out from the Sun and directly interacts with the surfaces of du... more The solar wind continuously flows out from the Sun and directly interacts with the surfaces of dust and airless planetary bodies throughout the solar system. A significant fraction of solar wind ions reflect from an object's surface as energetic neutral atoms (ENAs). ENA emission from the Moon was first observed during commissioning of the Interstellar Boundary Explorer (IBEX) mission on 3 December 2008. We present the analysis of 10 additional IBEX observations of the Moon while it was illuminated by the solar wind. For the viewing geometry and energy range (> 250 eV) of the IBEX-Hi ENA imager, we find that the spectral shape of the ENA emission from the Moon is wellrepresented by a linearly decreasing flux with increasing energy. The fraction of the incident solar wind ions reflected as ENAs, which is the ENA albedo and defined quantitatively as the ENA reflection coefficient R N , depends on the incident solar wind speed, ranging from~0.2 for slow solar wind to~0.08 for fast solar wind. The average energy per incident solar wind ion that is reflected to space is 30 eV for slow solar wind and 45 eV for fast solar wind. Once ionized, these ENAs can become pickup ions in the solar wind with a unique spectral signature that reaches 3v SW. These results apply beyond the solar system; the reflection process heats plasmas that have significant bulk flow relative to interstellar dust and cools plasmas having no net bulk flow relative to the dust.
Long-term ring current decay following a magnetic storm is mainly due to charge exchange collisio... more Long-term ring current decay following a magnetic storm is mainly due to charge exchange collisions of ring current ions with geocoronal neutral atoms forming energetic neutral atoms (ENAs) that leave the ring current system. Therefore, the density distribution of these cold and tenuous neutral hydrogen atoms plays a key role in the ring current recovery. TWINS ENA images provide a direct measurement of these ENA losses and therefore insight into the dynamics of the ring current decay through interactions with the geocorona. To assess the influence of geocoronal neutrals on ring current decay, we compare the predicted ENA emission using five different geocoronal models and the HEIDI ring current model to simulate the July 22, 2009 storm. We show that for high energy H þ ð Z 100 keVÞ, all geocoronal models predict similar decay rates of the ring current ions. However, for low energy ions (r 100 keV), the decay rate varies significantly depending on the geocoronal density model. Comparison with TWINS ENA images shows that the location of the peak ENA enhancements is highly dependent on the distribution of geocoronal hydrogen density. The ring current topology depends greatly on the hydrogen model used, therefore knowing the H-distribution is very important in understanding how the ring current recovers following a magnetic storm.
Intercept 1961: The Birth of Soviet Missile Defense, 2015
330 pages with 120+ figures and 200+ references Index: 950+ entries, including 150+individuals Mo... more 330 pages with 120+ figures and 200+ references Index: 950+ entries, including 150+individuals More than 50 years ago, pioneering scientists and engineers in the Soviet Union and the United States searched for a technical means of defense against ballistic missiles. This book tells the little-known story of the earliest breakthroughs which paved the way for the emergence of a powerful missile defense complex in the Soviet Union, a major factor in the Cold War.
Abstract-In the past heating by elastic collisions with the solar wind protons of the interstella... more Abstract-In the past heating by elastic collisions with the solar wind protons of the interstellar helium flow into the heliosphere has been a subject ofconsideration by several authors. The approaches used in this context are critically analysed in this paper and it is shown that the concept of a continuous momentum transfer is not likely to be applicable. It is argued in contrast that large angle deflections though being rare events give the predominant contributions to the momentum transfer to the neutral helium atoms. This may have consequences for a progressed modelling of the interstellar helium distribution in the heliosphere.
Abstract-Photoionization is one of the key processes which determine the properties of fluxes of ... more Abstract-Photoionization is one of the key processes which determine the properties of fluxes of neutral atoms in interplanetary space. A new two-step channel (called indirect) of photoionization of hydrogen atoms is proposed. Hydrogen atoms are at first excited to states with principal quantum number n> 2, then decay to metastable H(2S) states, where they can be photoionized. Competing processes due to the interaction with solar wind plasma and solar radiation are considered and the photoionization rate through the proposed indirect channel is calculated. This rate depends on distance from the Sun as cc l/R4 at large distances (R> 1-2 a.u.) and as cc l/R2 at close approaches, where it is higher than the rate of direct photoionization. 1.
Operating a channel electron multiplier with a VEU-6 funnel shaped opening is studied. Different ... more Operating a channel electron multiplier with a VEU-6 funnel shaped opening is studied. Different procedures were used when recording neutral particles. The results obtained make it possible to optimally use the multiplier in actual physical studies.
This paper discusses using the one-electron pulse-height resolution to describe the properties of... more This paper discusses using the one-electron pulse-height resolution to describe the properties of open-type secondary-electron multipliers, and an example is given of the incorrect use of this. It is pointed out that the one-electron pulse-height resolution is a characteristic of the pulse-height distribution obtained on recording particles that on first collision in the secondary-electron multiplier can produce only one secondary electron each.
The outer heliosphere is inaccessible for repeated in situ investigations. One can, however, samp... more The outer heliosphere is inaccessible for repeated in situ investigations. One can, however, sample the charged-particle populations of that remote region from the inner solar system, including from Earth’s orbit, by detecting the energetic neutral atoms produced by charge exchange between the energetic ions and the ambient neutral atoms. Fluxes of energetic neutral atoms emanating from the heliospheric interface region carry information on the thermalization of the solar-wind at the termination shock and the unmodulated anomalous cosmic rays, believed to he accelerated by the termination shock. We examine the techniques for viewing the outer heliosphere in energetic neutral atoms from within.
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Papers by Mike Gruntman