Change search
ReferencesLink to record
Permanent link

Direct link
Cluster observations and theoretical explanations of broadband waves in the auroral region
Umeå University, Faculty of Science and Technology, Department of Physics.
Show others and affiliations
2005 (English)In: Annales Geophysicae, Vol. 23, 3739-3752 p.Article in journal (Refereed) Published
Abstract [en]

 Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves), while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV) plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.

Place, publisher, year, edition, pages
Copernicus Publications , 2005. Vol. 23, 3739-3752 p.
URN: urn:nbn:se:umu:diva-4595DOI: 10.5194/angeo-23-3739-2005OAI: diva2:143755
Available from: 2005-05-13 Created: 2005-05-13 Last updated: 2012-05-04Bibliographically approved
In thesis
1. The importance of waves in space plasmas: Examples from the auroral region and the magnetopause
Open this publication in new window or tab >>The importance of waves in space plasmas: Examples from the auroral region and the magnetopause
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis discusses the reasons for space exploration and space science. Space plasma physics is identified as an essential building block to understand the space environment and it is argued that observation and analysis of space plasma waves is an important approach.

Space plasma waves are the main actors in many important processes. So-called broadband waves are found responsible for much of the ion heating in the auroral region. We investigate the wave properties of broadband waves and show that they can be described as a mixture of electrostatic wave modes. In small regions void of cold electrons the broadband activity is found to be ion acoustic waves and these regions are also identified as acceleration regions. The identification of the wave modes includes reconstructions of the wave distribution function. The reconstruction technique allow us to determine the wave vector spectrum, which cannot be measured directly. The method is applied to other wave events and it is compared in some detail with a similar method.

Space plasma wave are also sensitive tools for investigations of both the fine-structure and the dynamics of space plasmas. Studies of whistler mode waves observed in the boundary layer on the magnetospheric side of the magnetopause reveal that the plasma is organized in tube-like structures moving with the plasma drift velocity. The perpendicular dimension of these tubes is of the order of the electron inertial length. We present evidence that each tube is linked to a reconnection site and argue that the high density of tube-like structures indicates patchy reconnection.

Place, publisher, year, edition, pages
Umeå: Fysik, 2005. 28 p.
Space and plasma physics, Plasma waves, magnetospheric physics, magnetopause, auroral region, wave distribution function, space exploration, reconnection, current tubes, Rymd- och plasmafysik
National Category
Fusion, Plasma and Space Physics
Research subject
Space Physics
urn:nbn:se:umu:diva-538 (URN)91-7305-872-6 (ISBN)
Public defence
Available from: 2005-05-13 Created: 2005-05-13Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text
By organisation
Department of 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: 25 hits
ReferencesLink to record
Permanent link

Direct link