Abstract
Abstract. We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001) survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992). The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV), we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence the location and behaviour of the plasma populations in the magnetosphere. Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; magnetospheric configuration and dynamic)
Highlights
In order to understand how mass and energy flow into and around the magnetosphere, we must be able to relate plasma populations observed at different locations
The plasma component remaining on these field lines until they are closed by magnetic reconnection in the tail is trapped within the magnetosphere and subsequently accelerated earthward
The data set used in this study is from the Magnetospheric Ion Composition Sensor (MICS) of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE)
Summary
In order to understand how mass and energy flow into and around the magnetosphere, we must be able to relate plasma populations observed at different locations. In the energy range from 1.8 to 21.4 keV an enhancement was observed along the dawn flank between ≈68◦ and 75◦, giving rise to a dawn-dusk asymmetry This asymmetry was shown not to be caused by direct entry of particles into the magnetosphere (i.e. neither the Svalgaard-Mansurov effect nor a dawn-dusk asymmetry in Fermi acceleration at a quasiparallel bow shock), but by ions drifting earthward from the tail, as was demonstrated by sorting the data by energy and the sense of the interplanetary magnetic field Z−component (IMF BZ). Using a formulation introduced by Whipple (1978), they showed that, in general, the occurrence distributions of ions and electrons were globally consistent with the conventional drift paradigm; validating the simple corotation and convection electric fields used in their analysis They were able to describe the average particle transport over a wide range of geomagnetic activity levels.
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.
