The Physics of the Heliopause
ISSI International Team

Abstract

This proposal is for an ISSI team to study the physics of the heliopause in the context of the Voyager observations, with the goal of maximizing the science return from the mission. The team consists of the Principal Investigators or their representatives from each of the functioning instruments on Voyager and a broad selection of theorists/modelers. The two Voyager spacecraft are exploring a totally uncharted region of space and will make the first crossings of the heliopause and enter interstellar space. This proposed team is timely because of the likelihood that the Voyagers will soon see (or may already be) seeing phenomena associated with the heliopause.

Full text of the proposal document (PDF).

Team members

John Richardson	MIT	Voyager Plasma instrument
Vlad Izmodenov	Moscow State University	Theory and modeling, IBEX
Rob Decker	Johns Hopkins University	Voyager Low Energy Charged Particle instrument
Vladimir Florinski	University of Alabama, Huntsville	Theory and modeling
Hans Fahr	University of Bonn	Theory and modeling, IBEX
Roma Ratkiewicz	Polish Academy of Sciences	Theory and modeling
Randy Jokipii	University of Arizona	Theory and modeling, organizer
Merav Opher	Boston University	Theory and modeling
Ed Stone	CalTech	Voyager Cosmic Ray Subsystem, organizer
Tom Krimigis	Johns Hopkins University	Voyager Low Energy Charged Particle instrument
Jim Drake*	University of Maryland	Theory and modeling

* participated remotely

Project schedule

Meeting 1 agenda

Tuesday, April 17, beginning at 9:00 AM

Wednesday, April 18, beginning at 9:00 AM

Thursday and Friday, April 19-20: further discussion

Meeting 2 agenda

TBA

Publications

TBA

Topics to be addressed

• Heliopause kHz radio source from electrostatic waves

  • Cutoff constrains number density of electrons

• Is there a heliopause transition layer/region? How thick? Structure? Where?

  • Run simulations

  • Effects of neutrals, magnetic fields, modeling

  • Magnetopause analogs

  • Plasma depletion – reconnection?, physical cause

• Simulate flow patterns and compare with observations

  • Can one model reproduce both V1 and V2 observations of flows, and magnetic fields? Time dependence?

  • Also V2 densities and thermal proton temperature

• Prediction of 3-D structure and when V1/V2 are expected to cross heliopause. What will be seen?

• Constraints on parameters and boundary conditions for model simulations (interstellar neutrals, latitudinal solar wind, etc)

  • Compare the different implementations of the heliospheric simulations for the same parameters

• Long-term solar-cycle temporal variations of termination shock location at V1 and V2 now

• Origin of the V1 plasma stagnation region

  • Models

• Turbulence and large-scale instabilities at the heliopause

• Propagation of disturbances into the heliosheath

  • Statistical description of disturbances

• Galactic cosmic ray effects and gradients in the interstellar medium

  • Boundary conditions at the heliopause

  • Modulation outside the heliopause

  • Outer heliosheath fluctuations expected – can they significantly change the transport of cosmic rays?

  • Effects of the flow of ISM around the heliosphere on the GCR and ACR transport coefficients

• Termination Shock Particle and Anomalous Cosmic Ray boundary condition at the heliopause – free escape? Anisotropies? Observable intensities?

  • Decreases in intensity as the Voyagers move outward

  • Compare with field direction and optimal regions for reconnect at the heliopause

  • Effects of cross-field diffusion/transport

  • Spectral evolution in the heliosheath

• Magnetic field plasma, energetic particles in interstellar medium just outside of heliopause (magnitude, direction)

• Energetic neutral atoms

  • ENAs from the heliotail direction?

  • Ribbon/belt connection

  • Connection between ENA and Voyager observations

  • Implications of Voyager observations for ENA

  • Comparison of ENA observations with the heliospheric simulations

• Magnetic reconnection in the heliosheath/heliopause

  • Current-sheet thickness upstream and downstream of the termination shock?

  • Proton boundary layers, correlations with different instruments (esp. V2)

  • Direct observational tests of reconnection – e.g., V2 plasma turbulence

  • Observed magnetic field on V2 beyond 2009.5

  • Compare/contrast the two extreme model types now being considered

• Particle transport and accceleration by magnetic reconnection

  • Acceleration of anomalous cosmic rays – energy issue

  • Predicted large anisotropies from anomalous cosmic-ray acceleration

  • Energetic-particle transport in reconnected bubbles

• Inner-heliosheath magnetic field intensity related to flow speed