Sökning: onr:"swepub:oai:DiVA.org:uu-172148" >
On the Formation an...
On the Formation and Structure of the Ionosphere of Titan
-
- Ågren, Karin, 1980- (författare)
- Uppsala universitet,Institutionen för fysik och astronomi
-
- Wahlund, Jan-Erik, Associate Professor (preses)
- Uppsala universitet,Teknisk-naturvetenskapliga fakulteten
-
- Nagy, Andrew, Professor Emeritus (opponent)
- University of Michigan
-
(creator_code:org_t)
- ISBN 9789155483449
- Uppsala : Acta Universitatis Upsaliensis, 2012
- Engelska 64 s.
-
Serie: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 926
- Relaterad länk:
-
https://uu.diva-port... (primary) (Raw object)
-
visa fler...
-
https://urn.kb.se/re...
-
visa färre...
Abstract
Ämnesord
Stäng
- We present results on the ionospheric structure around Titan observed during numerous deep (<1000 km) flybys by the Cassini spacecraft. Our results are based on measurements by the radio and plasma wave science instrument, in particular the Langmuir probe. In addition, data from the magnetometer and electron spectrometer have contributed.The ionosphere of Titan is created when the atmosphere of the moon becomes ionised. There are several mechanisms that contribute to this, the most important of which are considered to be photoionisation by EUV from the Sun with associated photoelectron ionisation, and particle impact ionisation by electrons and ions from Saturn’s corotating magnetosphere.We investigate the influence of the solar zenith angle on the electron number density at the ionospheric peak. The results show on average four times more plasma on the dayside compared to the nightside, with typical densities of 2500 – 3500 cm-3 and 400 – 1000 cm-3, respectively. In a complementary study, we make a case study of a nightside flyby and show that the altitude structure of the deep ionosphere is reproducible by a simple electron impact ionisation model. Taken together, this leads to the conclusion that solar photons are the main ionisation source of the dayside ionosphere. However, magnetospheric particle precipitation also contributes and can explain the electron densities seen on the nightside.As Titan does not exhibit any large intrinsic magnetic field, the fact that it is embedded in the magnetosphere of Saturn means that the Kronian field drapes around the moon and gives rise to an induced magnetosphere. We show that there are currents of the order of 10 – 100 nA m-2 flowing in the ionosphere of the moon. Associated with the currents are perpendicular electric fields ranging from 0.5 to 3 µV m-1.Finally, we investigate measurements obtained during T70, the deepest Titan flyby performed to date. We show that there is a substantial amount of negative ions present below an altitude of 900 km. This confirms previous result by the electron spectrometer, showing negative ions at higher altitudes in Titan’s ionosphere.
Ämnesord
- NATURVETENSKAP -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)
Nyckelord
- Titan
- Cassini
- space physics
- ionisation
- electron density
- ionosphere
- negative ions
- electric currents
- electric fields
- solar zenith angle
- Langmuir probe
- Space and Plasma Physics
- Rymd- och plasmafysik
Publikations- och innehållstyp
- vet (ämneskategori)
- dok (ämneskategori)
Hitta via bibliotek
Till lärosätets databas