Change search
ReferencesLink to record
Permanent link

Direct link
Europa's far ultraviolet oxygen aurora from a comprehensive set of HST observations
KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Southwest Research Institute, United States.ORCID iD: 0000-0003-0554-4691
Show others and affiliations
2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 3, 2143-2170 p.Article in journal (Refereed) PublishedText
Abstract [en]

We analyze a large set of far ultraviolet oxygen aurora images of Europa's atmosphere taken by Hubble's Space Telescope Imaging Spectrograph (HST/STIS) in 1999 and on 19 occasions between 2012 and 2015. We find that both brightness and aurora morphology undergo systematic variations correlated to the periodically changing plasma environment. The time variable morphology seems to be strongly affected by Europa's interaction with the magnetospheric plasma. The brightest emissions are often found in the polar region where the ambient Jovian magnetic field line is normal to Europa's disk. Near the equator, where bright spots are found at Io, Europa's aurora is faint suggesting a general difference in how the plasma interaction shapes the aurora at Io and Europa. The dusk side is consistently brighter than the dawnside with only few exceptions, which cannot be readily explained by obvious plasma physical or known atmospheric effects. Brightness ratios of the near-surface OI] 1356 Å to OI 1304 Å emissions between 1.5 and 2.8 with a mean ratio of 2.0 are measured, confirming that Europa's bound atmosphere is dominated by O2. The 1356/1304 ratio decreases with increasing altitude in agreement with a more extended atomic O corona, but O2 prevails at least up to altitudes of ∼900 km. Differing 1356/1304 line ratios on the plasma upstream and downstream hemispheres are explained by a differing O mixing ratio in the near-surface O2 atmosphere of ∼5% (upstream) and ≲1% (downstream), respectively. During several eclipse observations, the aurora does not reveal any signs of systematic changes compared to the sunlit images suggesting no or only weak influence of sunlight on the aurora and an optically thin atmosphere.

Place, publisher, year, edition, pages
Blackwell Publishing, 2016. Vol. 121, no 3, 2143-2170 p.
Keyword [en]
aurora, Europa, HST
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-187287DOI: 10.1002/2015JA022073ISI: 000374730900022ScopusID: 2-s2.0-84961279412OAI: oai:DiVA.org:kth-187287DiVA: diva2:929529
Note

QC 20160519

Available from: 2016-05-19 Created: 2016-05-19 Last updated: 2016-06-08Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Roth, LorenzIvchenko, Nickolay
By organisation
Space and Plasma Physics
In the same journal
Journal of Geophysical Research - Space Physics
Fusion, Plasma and Space Physics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 6 hits
ReferencesLink to record
Permanent link

Direct link