<p>Meteoroids entering the Earth&#3... more <p>Meteoroids entering the Earth's atmosphere are associated with a number of phenomena including ablation, ambipolar diffusion, plasma transport, chemical reactions, shock waves, and plasma turbulence. A bright daylight fireball observed on 2020-12-04 13:30 UTC with two meteor cameras located in Skibotn and Sørreisa allowed the precise entry trajectory of the fireball to be determined. The path of the entering object is approximately between Angeli Finland and Pajala Sweden. Based on the brightness and entry trajectory, it is possible to estimate the approximate mass of the object, and associate it with a meteor shower (Northern Taurids). The effects of the fireball on the atmosphere were detected with a number of radar and radio instruments within the region, including ionosondes, meteor radars, an all-sky VHF imaging system, and an infrasound sensor. These observations allow a detailed study of the atmospheric interaction of a large meteoric body with the Earth's atmosphere to be made. In this talk, we will describe the observations of this fireball and discuss preliminary findings.</p>
We have conducted a campaign observation of auroras at Gillam (56.4N, 265.4E) and Fort Smith (60.... more We have conducted a campaign observation of auroras at Gillam (56.4N, 265.4E) and Fort Smith (60.0N, 248.1E), Canada, for January 2-15, 2008, during the tail-aligned phase of the THEMIS satellites. The observation was carried out using two all-sky cameras (180 degree field of view (FOV)) with a sampling rate of 30 Hz and two narrow FOV cameras ( 50 degree
The self-consistent determination of emergent flux and electron distribution in synchrotron self-... more The self-consistent determination of emergent flux and electron distribution in synchrotron self-Compton (SSC) models is considered in the limit when Compton cooling dominates synchrotron cooling and the Thomson optical depth is small. An approximate analytic description is found that agrees well with numerical solutions. The results are used to evaluate the importance of Compton cooling during the initial/high frequency phase of radio outbursts in flat spectrum compact radio sources. It is concluded that the main observational features are not likely due to a Compton phase in an adiabatically expanding source. It is shown explicitly why this conclusion differs from that of earlier calculations. An alternative model is considered, in which the injected electron distribution is anisotropic. The subsequent pitch angle scattering phase is identified with the high frequency radio outburst. The salient features expected from such a model agree qualitatively with those observed. The observed burst of 3C 345 is discussed in some detail; in particular, the importance of the different time evolutions between 1990 and 1994 of the burst in the initial and late phases is stressed. It is emphasized that in order to constrain models for the outbursts of compact radio sources, detailed observations of the initial phase are essential.
We have discussed in more detail the possibilities of extracting information on the dusty plasma ... more We have discussed in more detail the possibilities of extracting information on the dusty plasma conditions in planetary rings and in laboratories by observing the V-shaped Mach cone pattern around a charged body moving through or close to a layer of dusty plasma. ...
We have computed the dispersion relation for low-frequency dust-acoustic waves including dust cha... more We have computed the dispersion relation for low-frequency dust-acoustic waves including dust charge variation. A phase difference between the dust charge variation and the wave can lead to a strong damping of the wave. We present analytical expressions for the wave ...
We discuss to what extent small scale density inhomogeneities in the dust distribution may influe... more We discuss to what extent small scale density inhomogeneities in the dust distribution may influence radar backscatter in the summer mesopause. We show for a reasonable range of parameters that falling dust interacting with a neutral gas vortex cannot penetrate to the centre of the vortex. The size of the hole in the dust space density distribution around the vortex
We show that a dust test particle moving in a periodic orbit in electrostatic fields, as those du... more We show that a dust test particle moving in a periodic orbit in electrostatic fields, as those due to planetary rings, will experience a net deceleration also in the absence of any dust-dust collisions. The varying charge on the moving dust, as it moves in and out of regions of ...
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1996
... 9 by inserting the appropriate qd ad(min)U in Eq. 6, with U taken from Fig. 1 and the plasma ... more ... 9 by inserting the appropriate qd ad(min)U in Eq. 6, with U taken from Fig. 1 and the plasma densities to be used in the Debye wavelength k ( i,e) given by the Boltzmann distribution n n 0 exp Z eV kT . 16 ... Res. 98, 13315 1993. 6M. Rosenberg, Planet. Space Sci. 41, 229 1993. ...
Dust particles, assumed to be of one size and to exhibit a discrete distribution of electric char... more Dust particles, assumed to be of one size and to exhibit a discrete distribution of electric charges, are treated as heavy ions with a large number of ionization levels. The average of the discrete particle effects on the kinetic equations is approximated by the Lénard–Balescu collision term and by detailed counting to describe transport in velocity space and transitions between the differentionization levels respectively. We estimate analytically and numerically the relaxation times for the dust particles both towards a Maxwellian velocity distribution and towards an equilibrium distribution for the ionization levels. We sum over the ionization levels to obtain a hierarchy of ‘charge-moment’ equations for the single dust density function, and estimate the importance of terms originating from the ionization distribution. Similar terms are also present in the hydrodynamic equations for a dust plasma, and we briefly discuss these.
We investigate the charge-dispersive effects on a sheath of monosized dust particles in equilibri... more We investigate the charge-dispersive effects on a sheath of monosized dust particles in equilibrium. This is done through describing the dust particles by using equations in (x, v) space (kinetic space) that include terms originating from the charge distribution of the dust particles. The charge-dispersive terms are assumed to be completely determined by the local charging processes. We find that the effects due to these terms are opposed by the ordinary gradient terms in the current equation in kinetic space, and they are therefore smaller than first expected. We also identify kinetic effects that are not included in the usual expression for the dust charge in hydrodynamic space.
<p>Meteoroids entering the Earth&#3... more <p>Meteoroids entering the Earth's atmosphere are associated with a number of phenomena including ablation, ambipolar diffusion, plasma transport, chemical reactions, shock waves, and plasma turbulence. A bright daylight fireball observed on 2020-12-04 13:30 UTC with two meteor cameras located in Skibotn and Sørreisa allowed the precise entry trajectory of the fireball to be determined. The path of the entering object is approximately between Angeli Finland and Pajala Sweden. Based on the brightness and entry trajectory, it is possible to estimate the approximate mass of the object, and associate it with a meteor shower (Northern Taurids). The effects of the fireball on the atmosphere were detected with a number of radar and radio instruments within the region, including ionosondes, meteor radars, an all-sky VHF imaging system, and an infrasound sensor. These observations allow a detailed study of the atmospheric interaction of a large meteoric body with the Earth's atmosphere to be made. In this talk, we will describe the observations of this fireball and discuss preliminary findings.</p>
We have conducted a campaign observation of auroras at Gillam (56.4N, 265.4E) and Fort Smith (60.... more We have conducted a campaign observation of auroras at Gillam (56.4N, 265.4E) and Fort Smith (60.0N, 248.1E), Canada, for January 2-15, 2008, during the tail-aligned phase of the THEMIS satellites. The observation was carried out using two all-sky cameras (180 degree field of view (FOV)) with a sampling rate of 30 Hz and two narrow FOV cameras ( 50 degree
The self-consistent determination of emergent flux and electron distribution in synchrotron self-... more The self-consistent determination of emergent flux and electron distribution in synchrotron self-Compton (SSC) models is considered in the limit when Compton cooling dominates synchrotron cooling and the Thomson optical depth is small. An approximate analytic description is found that agrees well with numerical solutions. The results are used to evaluate the importance of Compton cooling during the initial/high frequency phase of radio outbursts in flat spectrum compact radio sources. It is concluded that the main observational features are not likely due to a Compton phase in an adiabatically expanding source. It is shown explicitly why this conclusion differs from that of earlier calculations. An alternative model is considered, in which the injected electron distribution is anisotropic. The subsequent pitch angle scattering phase is identified with the high frequency radio outburst. The salient features expected from such a model agree qualitatively with those observed. The observed burst of 3C 345 is discussed in some detail; in particular, the importance of the different time evolutions between 1990 and 1994 of the burst in the initial and late phases is stressed. It is emphasized that in order to constrain models for the outbursts of compact radio sources, detailed observations of the initial phase are essential.
We have discussed in more detail the possibilities of extracting information on the dusty plasma ... more We have discussed in more detail the possibilities of extracting information on the dusty plasma conditions in planetary rings and in laboratories by observing the V-shaped Mach cone pattern around a charged body moving through or close to a layer of dusty plasma. ...
We have computed the dispersion relation for low-frequency dust-acoustic waves including dust cha... more We have computed the dispersion relation for low-frequency dust-acoustic waves including dust charge variation. A phase difference between the dust charge variation and the wave can lead to a strong damping of the wave. We present analytical expressions for the wave ...
We discuss to what extent small scale density inhomogeneities in the dust distribution may influe... more We discuss to what extent small scale density inhomogeneities in the dust distribution may influence radar backscatter in the summer mesopause. We show for a reasonable range of parameters that falling dust interacting with a neutral gas vortex cannot penetrate to the centre of the vortex. The size of the hole in the dust space density distribution around the vortex
We show that a dust test particle moving in a periodic orbit in electrostatic fields, as those du... more We show that a dust test particle moving in a periodic orbit in electrostatic fields, as those due to planetary rings, will experience a net deceleration also in the absence of any dust-dust collisions. The varying charge on the moving dust, as it moves in and out of regions of ...
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1996
... 9 by inserting the appropriate qd ad(min)U in Eq. 6, with U taken from Fig. 1 and the plasma ... more ... 9 by inserting the appropriate qd ad(min)U in Eq. 6, with U taken from Fig. 1 and the plasma densities to be used in the Debye wavelength k ( i,e) given by the Boltzmann distribution n n 0 exp Z eV kT . 16 ... Res. 98, 13315 1993. 6M. Rosenberg, Planet. Space Sci. 41, 229 1993. ...
Dust particles, assumed to be of one size and to exhibit a discrete distribution of electric char... more Dust particles, assumed to be of one size and to exhibit a discrete distribution of electric charges, are treated as heavy ions with a large number of ionization levels. The average of the discrete particle effects on the kinetic equations is approximated by the Lénard–Balescu collision term and by detailed counting to describe transport in velocity space and transitions between the differentionization levels respectively. We estimate analytically and numerically the relaxation times for the dust particles both towards a Maxwellian velocity distribution and towards an equilibrium distribution for the ionization levels. We sum over the ionization levels to obtain a hierarchy of ‘charge-moment’ equations for the single dust density function, and estimate the importance of terms originating from the ionization distribution. Similar terms are also present in the hydrodynamic equations for a dust plasma, and we briefly discuss these.
We investigate the charge-dispersive effects on a sheath of monosized dust particles in equilibri... more We investigate the charge-dispersive effects on a sheath of monosized dust particles in equilibrium. This is done through describing the dust particles by using equations in (x, v) space (kinetic space) that include terms originating from the charge distribution of the dust particles. The charge-dispersive terms are assumed to be completely determined by the local charging processes. We find that the effects due to these terms are opposed by the ordinary gradient terms in the current equation in kinetic space, and they are therefore smaller than first expected. We also identify kinetic effects that are not included in the usual expression for the dust charge in hydrodynamic space.
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