M. Horanyi - Academia.edu (original) (raw)
Papers by M. Horanyi
Dust particles in interplanetary space can become charged through photoelectron emission by ultra... more Dust particles in interplanetary space can become charged through photoelectron emission by ultraviolet solar light. Additionally, dust particles can become charged through interaction with a UV-induced photoelectron sheath near the surface of larger space-borne objects. We have performed experiments to measure the photoelectric charging of single dust particles dropped through a beam of UV and dropped past a UV illuminated surface having a photoelectron sheath. The experiments are performed in vacuum, with illumination from a 1 kW Hg-Xe arc lamp having a minimum wavelength of ~ 200nm. The dust particles tested are 90-106 microns in diameter and are composed of zinc, copper, graphite, glass, SiC, JSC-1 (lunar regolith simulant) and JSC-Mars-1 (martian regolith simulant). The conducting materials charge in agreement with simple charging theory: positively when exposed to UV and negatively when interacting with the photoelectron sheath. Nonconducting materials exhibit a large amount of initial triboelectric charge. We will discuss the charges measured on each of these materials. ^* Work supported by NASA microgravity.
ABSTRACT Streams of tiny dust grains emerging from the volcanic plumes on Jupiter's moon ... more ABSTRACT Streams of tiny dust grains emerging from the volcanic plumes on Jupiter's moon Io are dispersed throughout Jupiter's magnetosphere with a fraction of them swiftly ejected even into interplanetary space. Up till now, speeds and sizes of these grains could be derived only indirectly from theoretical modelling. The fly-by of the Cassini spacecraft at Jupiter -- and the Galileo spacecraft orbiting the planet -- offered the unique opportunity to simultaneously observe the escaping streams of grains and to measure their speeds in a time-of-flight experiment between the two spacecraft. Our time-of-flight measurements result in a characteristic dust particle velocity on the order of 400 +/- 40 km s-1. This speed -- based on our computer simulations -- indicates a characteristic grain radius of approximately 8 +/- 2 nm. Our measurements imply a grain size distribution rising steeply towards smaller grains. The dust particle speeds are comparable with solar wind speeds and thus the Jovian dust stream particles are among the fastest objects in the solar system.
Planetary and Space Science
Cometary Plasma Processes, 2013
Cometary dust, by virtue of being immersed in a plasma and UV radiative environment are necessari... more Cometary dust, by virtue of being immersed in a plasma and UV radiative environment are necessarily electrically charged. This charging can lead to both physical and dynamical effects on the dust. On the other hand, the dust could have certain effects on the plasma as well as on the interplanetary magnetic field. These processes are discussed and the observations, both remote and in situ, which pertain to them are critically reviewed.
This data set contains Calibrated data taken by the New Horizons Student Dust Counter instrument ... more This data set contains Calibrated data taken by the New Horizons Student Dust Counter instrument during the post-launch checkout mission phase.
Journal of Geophysical Research: Atmospheres, 1998
We describe a new inversion algorithm for retrieving ozone densities and aerosol extinctions from... more We describe a new inversion algorithm for retrieving ozone densities and aerosol extinctions from Stratospheric Aerosol and Gas Experiment (SAGE) II measurements. The primary differences between the new algorithm and the current operational SAGE II inversion are the order of the species and altitude inversions, and the methods used to calculate aerosol extinction and remove saturated signals. Ozone densities retrieved at altitudes from 15 to 30 km using the new algorithm are compared to those from the operational SAGE II inversion, as well as to ozone densities from coincident balloon ozonesonde measurements at four different locations in the northern hemisphere between 1984 and 1991 for low to medium stratospheric aerosol loading conditions. The results of the comparison show that the ozone densities resulting from the operational and new algorithms agree to within 1% above 22 km. Below 22 km, the new results are lower than the operational results by up to 30%, depending on altitud...
The Jovian dust streams consist of 10 nanometer-sized dust particles which strongly couple to Jup... more The Jovian dust streams consist of 10 nanometer-sized dust particles which strongly couple to Jupiter's magnetosphere. After their discovery in interplanetary space with Ulysses in 1992, the streams have been monitored within the Jovian magnetosphere with Galileo since 1996 and have been observed with Cassini during its distant Jupiter flyby in 2000/2001. After release from their source - Io -
The break up of the comet Shoemaker-Levy 9 (SL9) in 1992 shortly before the fragment train specta... more The break up of the comet Shoemaker-Levy 9 (SL9) in 1992 shortly before the fragment train spectacularly crashed into Jupiter must have produced a copious amount of dust. It has been suggested (e.g., Horányi 1994, GRL 21, 1039--1042) that in about ten years following the SL9 disruption a fraction of material would settle in retrograde orbits well inside the jovian magnetosphere. In an attempt to find any evidence for the SL9 dust in the jovian system, we analyzed dust detector data of the Galileo spacecraft obtained from 1996 through 2001 between the orbits of the Galilean satellites. We have selected dust events probably caused by impacts of dust grains in retrograde orbits and derived yearly averages of the dust number density in that region. Our preliminary results seem to indicate a perceptible variation of the number density of the retrograde dust population with time, which might be attributed to the SL9 dust. Scarcity of the dataset prevents us from making firm conclusions, however. Furthermore, a direct comparison of the simulation results and the detector data is hampered by the fact that the theory and the measurements cover somewhat different time spans (2002 vs 1996--2001) and spatial regions (4--6 vs 6--30 jovian radii from the planet).
The New Horizons mission to Pluto and the Kuiper Belt is scheduled for launch in January 2006. As... more The New Horizons mission to Pluto and the Kuiper Belt is scheduled for launch in January 2006. As part of the Education and Public Outreach activity of the mission, undergraduate and graduate students at the Laboratory for Atmospheric and Space Physics, University of Colorado, are building a space experiment: the Student Dust Counter (SDC). This talk will summarize the technical
In a series of recent papers we predicted the existence of stable nonequatorial halo orbits of ch... more In a series of recent papers we predicted the existence of stable nonequatorial halo orbits of charged dust grains within the magnetosphere of Saturn. Now we consider how such orbits might be populated and their stability to time dependent charging as they visit different regions of the magnetosphere. In general we find that it is easier to generate prograde orbits than retrograde orbits. Results will be presented on lifetime limitations of various types of orbits due to time dependent charging. These model calculations will be extended to make predictions for the Cassini Cosmic Dust Analyzer measurements at Saturn.
A new instrument to analyze the chemical composition of dust particles in-situ in space has been ... more A new instrument to analyze the chemical composition of dust particles in-situ in space has been developed. The large target area (0.25 m2) makes this instrument well suited for detecting a statistically significant number of interstellar dust grains or other dust particles with a low flux. The device is a reflectron type time-of- flight mass spectrometer that measures the ions
... Sci. Conf., 26, 1577-1578. 7. Goertz, CK (1989), Dusty plasmas in the solar system, Rev. ... ... more ... Sci. Conf., 26, 1577-1578. 7. Goertz, CK (1989), Dusty plasmas in the solar system, Rev. ... Res., 103, 6605-6620. 9. Colwell, JE, AAS Gulbis, M. Horányi, S. Robertson (2005), Dust transport in photoelectron layers and the formation of dust ponds on Eros, Icarus, 175, 159-169. ...
The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact de... more The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact detector designed to map the interplanetary dust distribution along the trajectory of the New Horizons spacecraft as it traverses our solar system. VSDC is the first student built instrument on a deep space mission and is currently operated by a small group of undergraduate and graduate students at the Laboratory for Atmospheric and Space Physics (LASP), University of Colorado. VSDC is based on permanently polarized thin plastic film sensors that generate an electrical signal when an impacting dust particle penetrates them. The total surface area is about 0.1 square meters and the detection threshold is about 1 micron in radius. By the time of this meeting (7/2008), VSDC will have operated for about 500 days, covering an approximate distance of 1.2 to 10.5 AU. In this talk, we will briefly review the VSDC instrument, including the in-flight calibrations and tests. We will report on the measured spatial and size distribution of interplanetary dust particles before and after the New Horizons encounter with Jupiter. These data will also be compared to earlier measurements by Ulysses, Galileo and Cassini.
Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subs... more Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subsequent orbital dynamics of small grains can establish their size and spatial distributions, for example. Simultaneously, dust can alter the composition, density and temperature of the plasma surrounding it. The dynamics of charged dust particles can be surprisingly complex and fundamentally different from the well understood limits of gravitationally dominated motions of neutral particles or the adiabatic motion of electrons and ions in electromagnetic fields that dominate gravity. This talk will focus on recent Cassini observations at Saturn that are best explained by theories describing the effects of the magnetospheric fields and plasmas on the rings. As our best examples, we will discuss the physics describing the large-scale structure of the E-ring, and the formation of 'spokes' over the dense rings of Saturn.
Dust particles in interplanetary space can become charged through photoelectron emission by ultra... more Dust particles in interplanetary space can become charged through photoelectron emission by ultraviolet solar light. Additionally, dust particles can become charged through interaction with a UV-induced photoelectron sheath near the surface of larger space-borne objects. We have performed experiments to measure the photoelectric charging of single dust particles dropped through a beam of UV and dropped past a UV illuminated surface having a photoelectron sheath. The experiments are performed in vacuum, with illumination from a 1 kW Hg-Xe arc lamp having a minimum wavelength of ~ 200nm. The dust particles tested are 90-106 microns in diameter and are composed of zinc, copper, graphite, glass, SiC, JSC-1 (lunar regolith simulant) and JSC-Mars-1 (martian regolith simulant). The conducting materials charge in agreement with simple charging theory: positively when exposed to UV and negatively when interacting with the photoelectron sheath. Nonconducting materials exhibit a large amount of initial triboelectric charge. We will discuss the charges measured on each of these materials. ^* Work supported by NASA microgravity.
ABSTRACT Streams of tiny dust grains emerging from the volcanic plumes on Jupiter's moon ... more ABSTRACT Streams of tiny dust grains emerging from the volcanic plumes on Jupiter's moon Io are dispersed throughout Jupiter's magnetosphere with a fraction of them swiftly ejected even into interplanetary space. Up till now, speeds and sizes of these grains could be derived only indirectly from theoretical modelling. The fly-by of the Cassini spacecraft at Jupiter -- and the Galileo spacecraft orbiting the planet -- offered the unique opportunity to simultaneously observe the escaping streams of grains and to measure their speeds in a time-of-flight experiment between the two spacecraft. Our time-of-flight measurements result in a characteristic dust particle velocity on the order of 400 +/- 40 km s-1. This speed -- based on our computer simulations -- indicates a characteristic grain radius of approximately 8 +/- 2 nm. Our measurements imply a grain size distribution rising steeply towards smaller grains. The dust particle speeds are comparable with solar wind speeds and thus the Jovian dust stream particles are among the fastest objects in the solar system.
Planetary and Space Science
Cometary Plasma Processes, 2013
Cometary dust, by virtue of being immersed in a plasma and UV radiative environment are necessari... more Cometary dust, by virtue of being immersed in a plasma and UV radiative environment are necessarily electrically charged. This charging can lead to both physical and dynamical effects on the dust. On the other hand, the dust could have certain effects on the plasma as well as on the interplanetary magnetic field. These processes are discussed and the observations, both remote and in situ, which pertain to them are critically reviewed.
This data set contains Calibrated data taken by the New Horizons Student Dust Counter instrument ... more This data set contains Calibrated data taken by the New Horizons Student Dust Counter instrument during the post-launch checkout mission phase.
Journal of Geophysical Research: Atmospheres, 1998
We describe a new inversion algorithm for retrieving ozone densities and aerosol extinctions from... more We describe a new inversion algorithm for retrieving ozone densities and aerosol extinctions from Stratospheric Aerosol and Gas Experiment (SAGE) II measurements. The primary differences between the new algorithm and the current operational SAGE II inversion are the order of the species and altitude inversions, and the methods used to calculate aerosol extinction and remove saturated signals. Ozone densities retrieved at altitudes from 15 to 30 km using the new algorithm are compared to those from the operational SAGE II inversion, as well as to ozone densities from coincident balloon ozonesonde measurements at four different locations in the northern hemisphere between 1984 and 1991 for low to medium stratospheric aerosol loading conditions. The results of the comparison show that the ozone densities resulting from the operational and new algorithms agree to within 1% above 22 km. Below 22 km, the new results are lower than the operational results by up to 30%, depending on altitud...
The Jovian dust streams consist of 10 nanometer-sized dust particles which strongly couple to Jup... more The Jovian dust streams consist of 10 nanometer-sized dust particles which strongly couple to Jupiter's magnetosphere. After their discovery in interplanetary space with Ulysses in 1992, the streams have been monitored within the Jovian magnetosphere with Galileo since 1996 and have been observed with Cassini during its distant Jupiter flyby in 2000/2001. After release from their source - Io -
The break up of the comet Shoemaker-Levy 9 (SL9) in 1992 shortly before the fragment train specta... more The break up of the comet Shoemaker-Levy 9 (SL9) in 1992 shortly before the fragment train spectacularly crashed into Jupiter must have produced a copious amount of dust. It has been suggested (e.g., Horányi 1994, GRL 21, 1039--1042) that in about ten years following the SL9 disruption a fraction of material would settle in retrograde orbits well inside the jovian magnetosphere. In an attempt to find any evidence for the SL9 dust in the jovian system, we analyzed dust detector data of the Galileo spacecraft obtained from 1996 through 2001 between the orbits of the Galilean satellites. We have selected dust events probably caused by impacts of dust grains in retrograde orbits and derived yearly averages of the dust number density in that region. Our preliminary results seem to indicate a perceptible variation of the number density of the retrograde dust population with time, which might be attributed to the SL9 dust. Scarcity of the dataset prevents us from making firm conclusions, however. Furthermore, a direct comparison of the simulation results and the detector data is hampered by the fact that the theory and the measurements cover somewhat different time spans (2002 vs 1996--2001) and spatial regions (4--6 vs 6--30 jovian radii from the planet).
The New Horizons mission to Pluto and the Kuiper Belt is scheduled for launch in January 2006. As... more The New Horizons mission to Pluto and the Kuiper Belt is scheduled for launch in January 2006. As part of the Education and Public Outreach activity of the mission, undergraduate and graduate students at the Laboratory for Atmospheric and Space Physics, University of Colorado, are building a space experiment: the Student Dust Counter (SDC). This talk will summarize the technical
In a series of recent papers we predicted the existence of stable nonequatorial halo orbits of ch... more In a series of recent papers we predicted the existence of stable nonequatorial halo orbits of charged dust grains within the magnetosphere of Saturn. Now we consider how such orbits might be populated and their stability to time dependent charging as they visit different regions of the magnetosphere. In general we find that it is easier to generate prograde orbits than retrograde orbits. Results will be presented on lifetime limitations of various types of orbits due to time dependent charging. These model calculations will be extended to make predictions for the Cassini Cosmic Dust Analyzer measurements at Saturn.
A new instrument to analyze the chemical composition of dust particles in-situ in space has been ... more A new instrument to analyze the chemical composition of dust particles in-situ in space has been developed. The large target area (0.25 m2) makes this instrument well suited for detecting a statistically significant number of interstellar dust grains or other dust particles with a low flux. The device is a reflectron type time-of- flight mass spectrometer that measures the ions
... Sci. Conf., 26, 1577-1578. 7. Goertz, CK (1989), Dusty plasmas in the solar system, Rev. ... ... more ... Sci. Conf., 26, 1577-1578. 7. Goertz, CK (1989), Dusty plasmas in the solar system, Rev. ... Res., 103, 6605-6620. 9. Colwell, JE, AAS Gulbis, M. Horányi, S. Robertson (2005), Dust transport in photoelectron layers and the formation of dust ponds on Eros, Icarus, 175, 159-169. ...
The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact de... more The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact detector designed to map the interplanetary dust distribution along the trajectory of the New Horizons spacecraft as it traverses our solar system. VSDC is the first student built instrument on a deep space mission and is currently operated by a small group of undergraduate and graduate students at the Laboratory for Atmospheric and Space Physics (LASP), University of Colorado. VSDC is based on permanently polarized thin plastic film sensors that generate an electrical signal when an impacting dust particle penetrates them. The total surface area is about 0.1 square meters and the detection threshold is about 1 micron in radius. By the time of this meeting (7/2008), VSDC will have operated for about 500 days, covering an approximate distance of 1.2 to 10.5 AU. In this talk, we will briefly review the VSDC instrument, including the in-flight calibrations and tests. We will report on the measured spatial and size distribution of interplanetary dust particles before and after the New Horizons encounter with Jupiter. These data will also be compared to earlier measurements by Ulysses, Galileo and Cassini.
Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subs... more Saturn's rings show a variety of dusty plasma processes. The electrostatic charging and subsequent orbital dynamics of small grains can establish their size and spatial distributions, for example. Simultaneously, dust can alter the composition, density and temperature of the plasma surrounding it. The dynamics of charged dust particles can be surprisingly complex and fundamentally different from the well understood limits of gravitationally dominated motions of neutral particles or the adiabatic motion of electrons and ions in electromagnetic fields that dominate gravity. This talk will focus on recent Cassini observations at Saturn that are best explained by theories describing the effects of the magnetospheric fields and plasmas on the rings. As our best examples, we will discuss the physics describing the large-scale structure of the E-ring, and the formation of 'spokes' over the dense rings of Saturn.