Year-end Sale % OFF 
Abstract
Abstract. A large set of interplanetary shock waves observed using the Ulysses spacecraft is analysed in order to determine their local parameters. For the first time a detailed analysis is extended to the thermodynamic properties of a large number of events. The intention is to relate the shock parameters to the requirements set by MHD shock theory. A uniform approach is adopted in the selection of up and downstream regions for this analysis and applied to all the shock waves. Initially, the general case of a 3 component adiabatic plasma is considered. However, the calculation of magnetosonic and Alfvénic Mach numbers and the ratio of downstream to upstream entropy produce some unexpected results. In some cases there is no clear increase in entropy across the shock and also the magnetosonic Mach number can be less than 1. It is found that a more discerning use of data along with an empirical value for the polytropic index can raise the distribution of downstream to upstream entropy ratios to a more acceptable level. However, it is also realised that many of these shocks are at the very weakest end of the spectrum and associated phenomena may also contribute to the explanation of these results.
Highlights
Around the time of the first identification of a collisionless shock wave in the heliosphere by Sonett et al (1964) the actual existence of shock waves supporting dissipation with no collisions was in question
Gloag for a particular event seen in spacecraft data to be described as a shock wave. This theoretical shock structure consists of an increase in magnetic field magnitude and deflection of the magnetic field away from the shock normal, in the forward direction, for the much more commonly observed fast mode shock
In the case of slow mode shocks, passing from upstream to downstream, the magnetic field magnitude decreases and the field bends towards the shock normal direction
Summary
Around the time of the first identification of a collisionless shock wave in the heliosphere by Sonett et al (1964) the actual existence of shock waves supporting dissipation with no collisions was in question. These conditions can be expressed in terms of shock parameters which require the use of both magnetic and plasma data measured in situ by spacecraft experiments. The size of the up and downstream regions to be used in the calculation of the shock parameters for this study is influenced to some extent by the resolution of the plasma data.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
