English
norskBlar i forfatter "Lorentzen, Dag Arne"
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Electron Density Depletion Region Observed in the Polar Cap Ionosphere
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-16)This paper presents and discusses electron density depletion regions observed with the incoherent scatter EISCAT Svalbard Radar (ESR) located at 75.43°N geomagnetic latitude. The data include several decades of measurements, which make them suitable for studying statistical features and characteristics of the ionospheric parameters. Here we focus on the electron density depletions and their dependence ... -
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 ... -
Observations of sunlit N2+ aurora at high altitudes during the RENU2 flight
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-24)We present measurements of sunlit aurora during the launch of the Rocket Experiment for Neutral Upwelling 2 (RENU2) on the 13 December 2015, 07:34 UTC. The in situ auroral conditions coincide with those of sunlit aurora and were characterised by the 391.4 and 427.8 nm N<sub>2</sub> <sup>+</sup> emissions. A correlation between several auroral wavelengths, as measured by a meridian-scanning ... -
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) ... -
Particle precipitations during NEIAL events : simultaneous ground based observations at Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007)In this paper we present Naturally Enhanced Ion Acoustic Lines (NEIALs) observed with the EISCAT Svalbard Radar (ESR). For the first time, long sequences of NEIALs are recorded, with more than 50 events within an hour, ranging from 6.4 to 140 s in duration. The events took place from ~08:45 to 10:00 UT, 22 January 2004. We combine ESR data with observations of optical aurora by a meridian scanning ... -
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. ... -
Severe and localized GNSS scintillation at the poleward edge of the nightside auroral oval during intense substorm aurora
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-01)In this paper we study how GPS, GLONASS, and Galileo navigation signals are compromised by strong irregularities causing severe phase scintillation (σϕ>1) in the nightside high-latitude ionosphere during a substorm on 3 November 2013. Substorm onset and a later intensification coincided with polar cap patches entering the auroral oval to become auroral blobs. Using Global Navigation Satellite Systems ... -
SIOS’s Earth Observation (EO), Remote Sensing (RS), and operational activities in response to COVID-19
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-15)Svalbard Integrated Arctic Earth Observing System (SIOS) is an international partnership of research institutions studying the environment and climate in and around Svalbard. SIOS is developing an efficient observing system, where researchers share technology, experience, and data, work together to close knowledge gaps, and decrease the environmental footprint of science. SIOS maintains and facilitates ... -
Space and atmospheric physics on Svalbard: a case for continued incoherent scatter radar measurements under the cusp and in the polar cap boundary region
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-04)Incoherent scatter radars (ISRs) represent the only instrument (both ground and space based) capable of making high temporal and spatial resolution measurements of multiple atmospheric parameters—such as densities, temperatures, particle velocities, mass flux—over an altitude range covering the entire mesosphere/lower thermosphere/ionosphere (MLTI) system on a quasi-continuous basis. The EISCAT ...
