VEGA: En route to Venus and comet Halley

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95520/1/eost5312.pd

Charge exchange avalanche at the cometopause

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95404/1/grl3768.pd

Particle acceleration at comets

This paper compares calculated and measured energy spectra of implanted H+ and O+ ions on the assumption that the pick‐up geometry is quasi‐parallel and about 1% of the waves generated by the cometary pickup process propagates backward (towards the comet). The model provides a good description of the implanted O+ and H+ energy distribution near the pickup energies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87298/2/267_1.pd

An analytic solution to the steady‐state double adiabatic equations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94665/1/grl5619.pd

Dusty cometary atmospheres

This paper summarizes our present understanding of the physical processes controlling the dust and gas production of cometary nuclei and the evolution of the dusty gas flow in the inner coma. Special emphasis is being made to compile a self-consistent set of governing equations describing the accelerating dusty gas flow in a cometary atmosphere.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26895/1/0000461.pd

A Titov-D\'emoulin Type Eruptive Event Generator for β>0\beta>0 Plasmas

We provide exact analytical solutions for the magnetic field produced by prescribed current distributions located inside a toroidal filament of finite thickness. The solutions are expressed in terms of toroidal functions which are modifications of the Legendre functions. In application to the MHD equilibrium of a twisted toroidal current loop in the solar corona, the Grad-Shafranov equation is decomposed into an analytic solution describing an equilibrium configuration against the pinch-effect from its own current and an approximate solution for an external strapping field to balance the hoop force. Our solutions can be employed in numerical simulations of coronal mass ejections. When superimposed on the background solar coronal magnetic field, the excess magnetic energy of the twisted current loop configuration can be made unstable by applying flux cancellation to reduce the strapping field. Such loss of stability accompanied by the formation of an expanding flux rope is typical for the Titov & D\'emoulin (1999) eruptive event generator. The main new features of the proposed model are: (i) The filament is filled with finite $\beta$ plasma with finite mass and energy, (ii) The model describes an equilibrium solution that will spontaneously erupt due to magnetic reconnection of the strapping magnetic field arcade, and (iii) There are analytic expressions connecting the model parameters to the asymptotic velocity and total mass of the resulting CME, providing a way to connect the simulated CME properties to multipoint coronograph observations.Comment: 20 pages, 7 figure

Driving Saturn's magnetospheric periodicities from the upper atmosphere/ionosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95345/1/jgra21800.pd

Eruptive Event Generator Based on the Gibson-Low Magnetic Configuration

Coronal Mass Ejections (CMEs), a kind of energetic solar eruptions, are an integral subject of space weather research. Numerical magnetohydrodynamic (MHD) modeling, which requires powerful computational resources, is one of the primary means of studying the phenomenon. With increasing accessibility of such resources, grows the demand for user-friendly tools that would facilitate the process of simulating CMEs for scientific and operational purposes. The Eruptive Event Generator based on Gibson-Low flux rope (EEGGL), a new publicly available computational model presented in this paper, is an effort to meet this demand. EEGGL allows one to compute the parameters of a model flux rope driving a CME via an intuitive graphical user interface (GUI). We provide a brief overview of the physical principles behind EEGGL and its functionality. Ways towards future improvements of the tool are outlined

A time-dependent dusty gas dynamic model of axisymmetric cometary jets

The first results of a new time-dependent, axisymmetric dusty gas dynamical model of inner cometary atmospheres are presented. The model solves the coupled, time-dependent continuity, momentum, and energy equations for a gas--dust mixture between the nucleus surface and 100 km using a 40 x 40 axisymmetric grid structure. The time-dependent multidimensional partial differential equation system was solved with a new numerical technique employing a second-order accurate Godunov-type scheme with dimensional splitting. It is found that narrow axisymmetric jets generate a subsolar dust spike and a jet cone, where a significant amount of the jet ejecta is accumulated. This subsolar dust spike has not been predicted on earlier calculations. The opening angle of the jet cone depends on the jet strength and it also varies during the time-dependent phase of the jet. For weak jets the steady-state half-opening angle is about 50[deg]. In the case of the strong jets the jet cone extends to the nightside in good agreement with the Giotto imaging results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28694/1/0000514.pd