Access of energetic particles to Titan's exobase: A study of Cassini's T9 flyby
File(s)Regoli et al 2016.pdf (4.12 MB)
Published version
Author(s)
Type
Journal Article
Abstract
We study how the local electromagnetic disturbances introduced by Titan affect the ionization rates of the atmosphere. For this, we model the precipitation of energetic particles, specifically hydrogen and oxygen ions with energies between 1 keV and 1 MeV, into Titan׳s exobase for the specific magnetospheric configuration of the T9 flyby. For the study, a particle tracing software package is used which consists of an integration of the single particle Lorentz force equation using a 4th order Runge–Kutta numerical method. For the electromagnetic disturbances, the output of the A.I.K.E.F. hybrid code (kinetic ions, fluid electrons) is used, allowing the possibility of analyzing the disturbances and asymmetries in the access of energetic particles originated by their large gyroradii. By combining these methods, 2D maps showing the access of each set of particles were produced. We show that the access of different particles is largely dominated by their gyroradii, with the complexity of the maps increasing with decreasing gyroradius, due to the larger effect that local disturbances introduced by the presence of the moon have in the trajectory of the particles with lower energies. We also show that for particles with gyroradii much larger than the moon׳s radius, simpler descriptions of the electromagnetic environment can reproduce similar results to those obtained when using the full hybrid simulation description, with simple north–south fields being sufficient to reproduce the hybrid code results for O+ ions with energies larger than 10 keV but not enough to reproduce those for H+ ions at any of the energies covered in the present study. Finally, by combining the maps created with upstream plasma flow measurements by the MIMI/CHEMS instrument, we are able to estimate normalized fluxes arriving at different selected positions of the moon׳s exobase. We then use these fluxes to calculate energy deposition and non-dissociative N2 ionization rates for precipitating O+ and H+ ions and find differences in the ion production rates of up to almost 80% at the selected positions. All these results combined show that the electromagnetic field disturbances present in the vicinity of Titan significantly affect the contribution of energetic ions to local ionization profiles.
Date Issued
2015-12-03
Online Publication Date
2015-12-03
2017-02-06T09:53:00Z
Date Acceptance
2015-11-22
ISSN
1873-5088
Publisher
Elsevier
Start Page
40
End Page
53
Journal / Book Title
Planetary and Space Science
Volume
130
Copyright Statement
© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Source Database
web-of-science
Sponsor
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
The Royal Society
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000383302800006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
ST/K001051/1
ST/M003094/1
RP140004
ST/N000692/1
ST/N002776/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Titan
Exobase
Tracing software
Precipitation
Hybrid code
Energy deposition
MASS-SPECTROMETER
UPPER-ATMOSPHERE
IONOSPHERE
MAGNETOSPHERE
SIMULATION
ENCOUNTER
0201 Astronomical And Space Sciences
Publication Status
Published