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norskArtikler, rapporter og annet (TGO)
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A new five-wavelength photometer operated in Tromsø (69.6°N, 19.2°E)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-11)A new fve-wavelength photometer was developed and installed at the EISCAT Tromsø site (69.6°N, 19.2°E) in January 2017. The photometer consists of two units: an optical unit and a control unit together with a PC. The photometer is capable of simultaneously observing auroral emissions with fve wavelengths. A uniqueness of the present system is its capability of precise pointing, which enables ... -
Seasonal and solar cycle variations of thermally excited 630.0 nm emissions in the polar ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018)Solar cycle and seasonal variations have been found in the occurrence of strong thermally excited 630.0 nm emissions in the polar ionosphere. Measurements from the European Incoherent Scatter Svalbard Radar have been used to derive the thermal emission intensity. Thermally excited emissions have been found to maximize at solar maximum with peak occurrence rate of ∼40% compared to ∼2% at solar minimum. ... -
How Often Do Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-17)This paper studies thermally excited emissions in the polar ionosphere derived from European Incoherent Scatter Svalbard radar measurements from the years 2000–2015. The peak occurrence is found around magnetic noon, where the radar observations show cusp-like characteristics. The ionospheric, interplanetary magnetic field and solar wind conditions favor dayside magnetic reconnection as the dominant ... -
The red-sky enigma over Svalbard in December 2002
(Journal article; Tidsskriftartikkel; Peer reviewed, 2005-07-27)On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral ... -
On the contribution of thermal excitation to the total 630.0 nm emissions in the northern cusp ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-25)Direct impact excitation by precipitating electrons is believed to be the main source of 630.0 nm emissions in the cusp ionosphere. However, this paper investigates a different source, 630.0 emissions caused by thermally excited atomic oxygen O(1D) when high electron temperature prevail in the cusp. On 22 January 2012 and 14 January 2013, the European Incoherent Scatter Scientific Association (EISCAT) ... -
Neutral atmosphere temperature trends and variability at 90 km, 70°N, 19°E, 2003-2014
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-27)Neutral temperatures at 90 km height above Tromsø, Norway, have been determined using ambipolar diffusion coefficients calculated from meteor echo fading times using the Nippon/Norway Tromsø Meteor Radar (NTMR). Daily temperature averages have been calculated from November 2003 to October 2014 and calibrated against temperature measurements from the Microwave Limb Sounder (MLS) on board Aura. ... -
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-02)Cosmic noise at 40 MHz is measured at Ny-Ålesund (79° N, 12° E) using a relative ionospheric opacity meter ("riometer"). A riometer is normally used to determine the degree to which cosmic noise is absorbed by the intervening ionosphere, giving an indication of ionisation of the atmosphere at altitudes lower than generally monitored by other instruments. The usual course is to determine a "quiet-day" ... -
The auroral red line polarisation: modelling and measurements
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-12)In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is provided as input. An electron transport code is used to infer the stationary electron flux at each ... -
A case study on generation mechanisms of a sporadic sodium layer above Tromsø (69.6° N) during a night of high auroral activity
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-05)We have quantitatively evaluated generation mechanisms of a sporadic sodium layer (SSL) based on observational data obtained by multiple instruments at a high-latitude station: Ramfjordmoen, Tromsø, Norway (69.6° N, 19.2° E). The sodium lidar observed an SSL at 21:18 UT on 22 January 2012. The SSL was observed for 18 min, with a maximum sodium density of about 1.9 × 1010 m−3 at 93 km with a 1.1 km ... -
Change in turbopause altitude at 52 and 70° N
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-26)The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general ... -
Spectral characteristics of high latitude raw 40MHz cosmic noise signals
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-07)Cosmic noise at 40 MHz is measured at Ny-Ålesund (79◦ N, 12◦ E) using a relative ionospheric opacity meter (“riometer”). A riometer is normally used to determine the degree to which cosmic noise is absorbed by the intervening ionosphere, giving an indication of ionization of the atmosphere at altitudes lower than generally monitored by other instruments. The usual course is to determine a ... -
Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures - Part 1
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014) -
A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014) -
Complexity signatures in the geomagnetic H-component recorded by the Tromsø magnetometer (70°N, 19°E) over the last quarter of a century
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014) -
Complexity signatures for short timescales in the atmosphere above Adventdalen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-30) -
Real-time determination and monitoring of the auroral electrojet boundaries
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)A method for nowcasting of the auroral electrojet location from real-time geomagnetic data in the European sector is presented. Along the auroral ovals strong electrojet currents are flowing. The variation in the geomagnetic field caused by these auroral electrojets is observed on a routine basis at high latitudes using ground-based magnetometers. From latitude profiles of the vertical component of ... -
Internasjonale forpliktelser
(Journal article; Tidsskriftartikkel, 1980)I forbindelse med at Nordlysobservatoriet har eksistert i 50 år kan det være på sin plass å spørre om det fortsatt er behov for virksomheten. Svaret er at observatoriet fyller en viktig oppgave i internasjonal forskning. -
Nordlysobservatoriet gjennom 50 år
(Journal article; Tidsskriftartikkel, 1980)De mange forsøk på å beskrive og forklare nordlyset som en finner i eldre litteratur vitner om lange tradisjoner for denne forskningen i vårt land. Norge ble av mange oppfattet som "Nordlysets Fædreneland" som biskop Spidberg fra Kristiansand uttrykte det allere i 1750. -
Radiobølgeforplantning i ionosfæren
(Journal article; Tidsskriftartikkel, 1980)Atmosfæren er bygd opp av nitrogen og oksygen. Opp til 60-70 km er atmosfæren stort sett nøytral, alle atomer har like mye positiv som negativ ladning. Høyere oppe vil røntgenstråling og energirike partikler forårsake ionisering, dvs. en del atomer blir spaltet i positive ion og frie elektroner. Det er dette høydeområdet fra ca. 60-1000 km, med relativt stor tetthet av drie ladede partikler, som nå ... -
Nordlys i atmosfæren
(Journal article; Tidsskriftartikkel, 1980)Nordlyset er lys i atmosfæren som skyldes nedbør av energirike partikler - særlig elektroner, og de former og bevegelser vi ser i nordlyset skyldes variasjoner i denne atmosfæren. Når energirike elektroner nærmer seg jorden ovenfra, trenger de gjennom atmosfæren som stadig øker i tetthet. i 150-100 km's høyde blir atmosfærens tetthet så stor at elektronene begynner å kollidere med atmosfærenes atomer ...
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