174 research outputs found
Generalizations of the St\"ormer Problem for Dust Grain Orbits
We consider the generalized St\"ormer Problem that includes the
electromagnetic and gravitational forces on a charged dust grain near a planet.
For dust grains a typical charge to mass ratio is such that neither force can
be neglected. Including the gravitational force gives rise to stable circular
orbits that encircle that plane entirely above/below the equatorial plane. The
effects of the different forces are discussed in detail. A modified 3rd
Kepler's law is found and analyzed for dust grains.Comment: 21 pages LaTeX, 12 figure
Modeling of dust halo formation following comet outbursts: Preliminary results
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94600/1/grl3123.pd
Modeling solar wind massâloading in the vicinity of the Sun using 3âD MHD simulations
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106053/1/jgra50759.pd
Lunar surface: Dust dynamics and regolith mechanics
The lunar surface is characterized by a collisionally evolved regolith resulting from meteoroid bombardment. This lunar soil consists of highly angular particles in a broad, approximately power law size distribution, with impact-generated glasses. The regolith becomes densified and difficult to excavate when subjected to lunar quakes or, eventually, manned and unmanned activity on the surface. Solar radiation and the solar wind produce a plasma sheath near the lunar surface. Lunar grains acquire charge in this environment and can exhibit unusual behavior, including levitation and transport across the surface because of electric fields in the plasma sheath. The fine component of the lunar regolith contributes to the operational and health hazards posed to planned lunar expeditions. In this paper we discuss the mechanical response of the regolith to anticipated exploration activities and review the plasma environment near the lunar surface and the observations, models, and dynamics of charged lunar dust
2012), Characteristics of a plasma sheath in a magnetic dipole field: Implications to the solar wind interaction with the lunar magnetic anomalies
[1] The solar wind interaction with the lunar surface, especially in regions of crustal magnetic anomalies, remains of great interest for in situ plasma measurements. Small-scale laboratory experiments cannot reproduce the conditions near the lunar surface, but provide a unique opportunity to identify and examine several of the physical processes. We study plasma interaction with a magnetic dipole field at an insulating surface in order to understand the effect of crustal magnetic anomalies on the solar wind-lunar surface interaction. In our experiments, electrons are magnetized with gyroradii r smaller than distances from the surface d (r < d) but ions remain unmagnetized with r > d. The measured potential distribution shows a non-monotonic sheath above the surface and variations on the surface along the axis of the dipole field. The surface near the center of the dipole is charged more positively by ions as the electrons are magnetically shielded away. A potential minimum is found in the shielding region between the surface and the bulk plasma due to collisional and magnetic mirror trapping effects. Potential variations on the surface are the result of the inhomogeneity of the dipolar field, showing an enhancement of the electric field at the cusps. Enhanced electric fields in the regions of magnetic anomalies on the lunar surface may enhance the transport of small-sized charged dust particles, possibly explaining the formation of the lunar swirls. Citation: Wang, X., M. HorĂĄnyi, and S. Robertson (2012), Characteristics of a plasma sheath in a magnetic dipole field: Implications to the solar wind interaction with the lunar magnetic anomalies
Galileo dust data from the jovian system: 2000 to 2003
The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003.
The Galileo dust detector monitored the jovian dust environment between about 2
and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo
dust instrument for the period January 2000 to September 2003. We report on the
data of 5389 particles measured between 2000 and the end of the mission in
2003. The majority of the 21250 particles for which the full set of measured
impact parameters (impact time, impact direction, charge rise times, charge
amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in
radius), most of them originating from Jupiter's innermost Galilean moon Io.
Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact
rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280
R_J from Jupiter. This peak in dust emission appears to coincide with strong
changes in the release of neutral gas from the Io torus. Strong variability in
the Io dust flux was measured on timescales of days to weeks, indicating large
variations in the dust release from Io or the Io torus or both on such short
timescales. Galileo has detected a large number of bigger micron-sized
particles mostly in the region between the Galilean moons. A surprisingly large
number of such bigger grains was measured in March 2003 within a 4-day interval
when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J
jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003
provided the first actual comparison of in-situ dust data from a planetary ring
with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space
Scienc
Probing IMF using nanodust measurements from inside Saturn's magnetosphere
We present a new concept of monitoring the interplanetary magnetic field (IMF) by using in situ measurements of nanodust stream particles in Saturn's magnetosphere. We show that the nanodust detection pattern obtained inside the magnetosphere resembles those observed in interplanetary space and is associated with the solar wind compression regions. Our dust dynamics model reproduces the observed nanodust dynamical properties as well as the detection pattern, suggesting that the ejected stream particles can reenter Saturn's magnetosphere at certain occasions due to the dynamical influence from the timeâvarying IMF. This method provides information on the IMF direction and a rough estimation on the solar wind compression arrival time at Saturn. Such information can be useful for studies related to the solar windâmagnetosphere interactions, especially when the solar wind parameters are not directly available. Key Points A new method to probe IMF with nanodust measurements inside the magnetosphere Under changing IMF, ejected nanoparticles can reâenter Saturnâs magnetosphere IMF direction and solar wind compression arrival time can be derivedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99078/1/grl50604.pd
Mass loading of the solar wind by a sungrazing comet
Collisionless mass loading was suggested by Biermann et al. (1967) for describing interactions between the solar wind and cometary atmospheres. Recent observations have led to an increased interest in coronal mass loading due to sungrazing comets and collisional debris of sunward migrating interplanetary dust particles. In a previous paper, we presented a 3âD MHD model of the solar corona based on the BlockâAdaptiveâTreeâSolarwindâRoeâUpwindâScheme code which includes the interaction of dust with the solar wind. We have shown the impact on the solar wind from abrupt mass loading in the coronal region. We apply the model to a sungrazing cometary source, using ejected dust dynamics to generate tailâshaped massâloading regions. Results help predict the effects on the solar wind acceleration and composition due to sungrazing comets, such as Comet C/2011 W3 (Lovejoy). We show how these effects may be detected by the upcoming Solar Probe Plus Mission. Key Points Application of mass loading in the SWMF SC component for sungrazing comets Extension to a tail source model for mass loading due to a sungrazing comet Prediction of massâloaded solar wind parameters along a space probe pathPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108676/1/grl51967.pd
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