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Alfven Waves and Spatio-Temporal Structuring in the Auroral Ionosphere
KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.ORCID-id: 0000-0003-2422-5426
2002 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Stockholm: KTH , 2002. , s. x, 41
Nyckelord [en]
dispersive alfrén waves, auroral particle acceleration, ionospheric alfvén resonator, auroral particle acceleration, small scale auroral structure
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
URN: urn:nbn:se:kth:diva-3364OAI: oai:DiVA.org:kth-3364DiVA, id: diva2:9156
Disputation
2002-06-07, 00:00
Anmärkning
QC 20100618Tillgänglig från: 2002-06-05 Skapad: 2002-06-05 Senast uppdaterad: 2010-06-18Bibliografiskt granskad
Delarbeten
1. Quasiperiodic oscillations observed at the edge of an auroral arc by Auroral Turbulence 2
Öppna denna publikation i ny flik eller fönster >>Quasiperiodic oscillations observed at the edge of an auroral arc by Auroral Turbulence 2
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1999 (Engelska)Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 26, nr 22, s. 3365-3368Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The Auroral Turbulence II (AT2) sounding rocket carried three payloads into the auroral ionosphere where they crossed several are structures. At the border of an auroral are a quasiperiodic structure was observed by the magnetic and electric field instruments as well as by the particle detectors. The variations were temporal oscillations, but existed only in a narrow (approximate to 7 km) region transverse to the are, with a correlation length along the are of at least several km. The relation between the electric and magnetic field amplitude indicates the Alfvenic nature of the variations. Field aligned electron precipitation is correlated to the field variations. The narrow band nature of the oscillations and frequency around 0.6 Hz is consistent with waves confined in the ionospheric Alfven resonator.

Nyckelord
Alfven Waves, Sounding Rocket, Boundary, Cavity, Model
Nationell ämneskategori
Geofysik
Identifikatorer
urn:nbn:se:kth:diva-13427 (URN)10.1029/1999GL003588 (DOI)000083677500009 ()
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
2. Multiple-point electron measurements in a nightside auroral arc: Auroral Turbulence II particle observations
Öppna denna publikation i ny flik eller fönster >>Multiple-point electron measurements in a nightside auroral arc: Auroral Turbulence II particle observations
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1999 (Engelska)Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 26, nr 22, s. 3361-3364Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We report here three-point measurements of bursty, velocity-dispersed, field-aligned electron precipitation at the poleward edge of a northward-moving, post-breakup, nightside auroral arc. The three-point measurement allows detection of the proper motion of the inverted-V arc, which is shown to be 550 m/sec northward. The velocity dispersion patterns are fitted to find the source altitude of the precipitation bursts as a function of distance from the poleward edge of the are. These source points are interpreted to trace out the low-altitude boundary of the inverted-V potential drop, which is seen to rise both in time, and in the northward direction. The precipitation bursts under the inverted-V are seen to have an are-aligned velocity which varies with time, and which is consistent with the measured E x B local drift speed.

Nyckelord
2407 Ionosphere: Auroral ionosphere, 2455 Ionosphere: Particle precipitation, 2494 Ionosphere: Instruments and techniques, 7807 Space Plasma Physics: Charged particle motion and acceleration
Nationell ämneskategori
Geofysik
Identifikatorer
urn:nbn:se:kth:diva-13435 (URN)10.1029/1999GL900599 (DOI)000083677500008 ()
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
3. Observation of low frequency electromagnetic activity at 1000 km altitude
Öppna denna publikation i ny flik eller fönster >>Observation of low frequency electromagnetic activity at 1000 km altitude
2001 (Engelska)Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 19, nr 6, s. 643-648Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present a statistical study of low frequency fluctuations of electric and magnetic fields, commonly interpreted as Alfvenic activity. The data base consists of six months of electric and magnetic field measurements by the Astrid-2 microsatellite. The occurrence of the events is studied with respect to the location and general activity. Large regions of broadband Alfvenic activity are persistently observed in the cusp/cleft and, during the periods of high geomagnetic activity, also in the pre-midnight sector of the auroral oval.

Nyckelord
ionosphere, auroral ionosphere, space plasma physics, waves and instabilities, magnetospheric physics, magnetosphere-ionosphere interactions, ALFVEN WAVES, AURORAL ARC
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:kth:diva-13438 (URN)10.5194/angeo-19-643-2001 (DOI)000169921400007 ()
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
4. Electron signatures and Alfven waves
Öppna denna publikation i ny flik eller fönster >>Electron signatures and Alfven waves
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2002 (Engelska)Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, nr A9Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

[1] We identify two distinct electron populations associated with Alfven waves in the Freja data set using the high time resolution state of the art electron detector. One of the populations, detected together with an Alfven wave, is field-aligned and can be seen as trapped within the wave. The other electron population is detected before the wave and consists of electrons which have left the wave at a point with a velocity higher than the local Alfven speed. In the paper, the electrons leaving wave are modeled for different density profiles and are compared with the observed data. Depending on the density profile, the model can produce the same energy-time and pitch angle-time dispersion that is observed in the Freja data. The conclusion of the paper is that the Alfven wave can explain the observed particle signatures. It is shown that the Alfven wave acceleration can create electron signatures similar to inverted-V structures. The density distribution along a flux tube has an important role in the type of particle signatures that can be detected at low altitudes.

Nyckelord
Alfven wave, electron acceleration, FREJA SATELLITE-OBSERVATIONS, PLASMA-WAVES, AURORAL ARC, ACCELERATION, PRECIPITATION, MAGNETOSPHERE, IONOSPHERE, ENERGIZATION, DISPERSION, EMISSION
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:kth:diva-13440 (URN)10.1029/2001JA900096 (DOI)000180343700020 ()
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
5. Field aligned current structures and associated pulsations during substorm recovery
Öppna denna publikation i ny flik eller fönster >>Field aligned current structures and associated pulsations during substorm recovery
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2002 (Engelska)Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202Artikel i tidskrift (Refereegranskat) Submitted
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:kth:diva-13445 (URN)
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
6. Numerical simulation of feedback instability in the ionospheric alfvén resonator
Öppna denna publikation i ny flik eller fönster >>Numerical simulation of feedback instability in the ionospheric alfvén resonator
2002 (Engelska)Rapport (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2002
Serie
Trita-ALP, ISSN 1103-6613 ; 2002:05
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:kth:diva-13448 (URN)
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2010-06-18Bibliografiskt granskad
7. Ionospheric reflection of small scale alfven waves: collisional effects
Öppna denna publikation i ny flik eller fönster >>Ionospheric reflection of small scale alfven waves: collisional effects
2002 (Engelska)Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007Artikel i tidskrift (Övrigt vetenskapligt) Submitted
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:kth:diva-13449 (URN)
Anmärkning
QC 20100618Tillgänglig från: 2010-06-18 Skapad: 2010-06-18 Senast uppdaterad: 2017-12-12Bibliografiskt granskad

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