Blar i utgivelsesdato Artikler, rapporter og annet (TGO)
Viser treff 21-40 av 42
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Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009) -
Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009) -
Arctic tidal characteristics at Eureka (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006/07 : seasonal and longitudinal variations, migrating and non-migrating tides
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009) -
Characteristics of Arctic tides at CANDAC-PEARL (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006-2009 : radar observations and comparisons with the model CMAM-DAS
(Journal article; Tidsskriftartikkel; Peer reviewed, 2011)Operation of a Meteor Radar (MWR) at Eureka, Ellesmere Island (80° N, 86° W) began in February 2006: this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL), operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC). The first 36 months of tidal wind data (82–97 km) are here combined with contemporaneous tides from the Meteor Radar (MWR) ... -
Tropopause height at 78 degrees N 16 degrees E: average seasonal variation 2007-2010
(Journal article; Tidsskriftartikkel; Peer reviewed, 2011)We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by ... -
Tropopause height at 78°N 16°E: average seasonal variation 2007-2010
(Journal article; Tidsskriftartikkel; Peer reviewed, 2011)We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by ... -
Characteristics of Arctic winds at CANDAC-PEARL (80 degrees N, 86 degrees W) and Svalbard (78 degrees N, 16 degrees E) for 2006-2009: radar observations and comparisons with the model CMAM-DAS
(Journal article; Tidsskriftartikkel; Peer reviewed, 2011)Operation of a Meteor Wind Radar (MWR) at Eureka, Ellesmere Island (80° N, 86° W) began in February 2006; this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL), operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC). The first 36 months of wind data (82–97 km) are here combined with contemporaneous winds from the Meteor Wind Radar ... -
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 ... -
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) -
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 ... -
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 ... -
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 ... -
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 ... -
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" ... -
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) ... -
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 ...