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Sodankylä, Finland

Kozlovsky A.,Sodankyla Geophysical Observatory | Lukianova R.,Arctic and Antarctic Research Institute | Shalimov S.,RAS Research Center Kurchatov Institute | Lester M.,University of Leicester
Journal of Geophysical Research A: Space Physics | Year: 2016

Meteor radar observations at the Sodankylä Geophysical Observatory (67° 22′N, 26° 38′E, Finland) indicate that the mesospheric temperature derived from meteor decay times is systematically underestimated by 20-50 K during the Geminids meteor shower which has peak on 13 December. A very good coincidence of the minimum of routinely calculated temperature and maximum of meteor flux (the number of meteors detected per day) was observed regularly on that day in December 2008-2014. These observations are for a specific height-lifetime distribution of the Geminids meteor trails and indicate a larger percentage of overdense trails compared to that for sporadic meteors. A consequence of this is that the routine estimates of mesospheric temperature during the Geminids are in fact underestimates. The observations do, however, indicate unusual properties (e.g., mass, speed, or chemical composition) of the Geminids meteoroids. Similar properties were found also for Quadrantids in January 2009-2015, which like the Geminids has as a parent body an asteroid, but not for other meteor showers. ©2016. American Geophysical Union. All Rights Reserved. Source

Lukianova R.Y.,Arctic and Antarctic Research Institute | Kozlovskii A.,Sodankyla Geophysical Observatory | Christiansen F.,Technical University of Denmark
Geomagnetism and Aeronomy | Year: 2012

Structures controlled by the IMF By sign and season of the year have been detected based on the decomposition of field-aligned current maps constructed using magnetic field measurements on polar low-orbiting satellites. It has been indicated that field-aligned currents have identical structures, composed of the main polar circular current and the return current at the polar cap dayside boundary, at any By sign in the summer hemisphere. Two different types of structures are implemented under winter conditions depending on the By sign. For the northern winter, it is the polar circular current and the return current at the polar cap nightside boundary at By <0; current sheets are strongly stretched along latitudes below 80° MLat, and only small part of the current is in the noon sector of the polar cap. For the summer winter, the corresponding structures are implemented at opposite By signs. The intensities of the field-aligned currents, originating as a result of the interhemispheric asymmetry and flowing along closed geomagnetic field lines near the polar cap boundary, have been estimated. The maximum of the interhemispheric current density is 0.25 μA m -2 in the summer and 0.1 μA m -2 in the winter; the total current is 5 × 10 5 and 5 × 10 4 A, respectively. © 2012 Pleiades Publishing, Ltd. Source

Manninen J.,Sodankyla Geophysical Observatory | Kleimenova N.G.,Russian Academy of Sciences | Kozyreva O.V.,Russian Academy of Sciences
Geomagnetism and Aeronomy | Year: 2013

We discuss the results of an analysis of digital high-sensitivity ground-based observations of very low frequency (VLF) emissions, carried out in Northern Finland (L = 5.3) in May-June 2012. During this period of time, we found that three high-speed solar wind streams approached the Earth's magnetosphere and at the front of these fluxes long-lasting intense daytime bursts of VLF emissions were generated in two frequency bands: above and below ∼2.5 kHz. At frequencies above ∼2.5-3.0 kHz, there were VLF hiss waves, the temporal structure of which consisted of a quasi-periodic sequence of separate stronger spots of noise signals. The low-frequency band was represented by chorus waves, superimposed on intense hiss emissions at frequencies below ∼1.5 kHz. The high-frequency (f > 2.5 kHz) waves were elliptic and, predominately, left-hand polarized and the low-frequency waves were right-hand polarized. It was supposed that high-frequency VLF hiss waves were generated at L < 5 and VLF chorus waves were generated at L > 5. We discuss a possible scenario of the generation and propagation of the VLF emissions observed. © 2013 Pleiades Publishing, Ltd. Source

Kozlovsky A.,Sodankyla Geophysical Observatory | Shalimov S.,Institute of Physics of the Earth | Lukianova R.,Space Research Institute | Lester M.,University of Leicester
Journal of Geophysical Research: Space Physics | Year: 2014

We report on ionosonde and meteor radar observations made in Sodankylä Geophysical Observatory (SGO, 67°22 N, 26°38 E, Finland) on 9 December 2009, during a test launch of the Russian solid propellant military missile. Due to a technical problem, the missile was self-destroyed around 07 UT at an ionospheric height (near 200 km altitude) over the Kola Peninsula (Russia), at a distance about 500 km to east from the observatory. Products of the explosion were spread into a large area and reached the region of SGO meteor radar observations in about 2 h (around 09 UT). After about 3 h (around 10 UT), a sporadic E layer presumably composed of the remains including long-lived metallic (aluminum and its oxides) ions, was observed near the zenith of the SGO ionosonde. We discuss possible mechanisms accounting for transport of the remains. (1) Since the event occurred during a long-lasting period of extremely low solar and magnetic activity, the ionospheric electric field was unlikely to play a substantial role in the transport of the remains and sporadic E layer formation. (2) The horizontal transport of the remains cannot be explained by the neutral winds based on empirical models. (3) Theoretical estimations suggest that the observed transport could be due to thermospheric turbulence. Key Points Solid propellant rocket destruction in the ionosphere on 9 December 2009 Ionospheric effects observed by ionosonde and meteor radar Transport of rocket remains (metallic ions) in the high-latitude ionosphere ©2014. American Geophysical Union. All Rights Reserved. Source

Kavanagh A.J.,Lancaster University | Kavanagh A.J.,British Antarctic Survey | Honary F.,Lancaster University | Donovan E.F.,University of Calgary | And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2012

We present an epoch analysis of energetic (>30keV) electron precipitation during 173 high speed solar wind streams (HSS) using riometer observations of cosmic noise absorption (CNA) as a proxy for the precipitation. The arrival of the co-rotating interaction region (CIR) prior to stream onset, elevates the precipitation which then peaks some 12h after stream arrival. Precipitation continues for several days following the HSS arrival. The MLT distribution of CNA is generally consistent with the statistical pattern explained via the substorm process, though the statistical deep minimum of CNA/precipitation does change during the HSS suggesting increased precipitation in the 15-20 MLT sector. The level of precipitation is strongly controlled by the average state of the IMF BZ component on the day prior to the arrival of the stream interface. An average negative IMF BZ will produce higher CNA across all L-shells and MLT, up to 100% higher than an average positive IMF BZ. © 2012 American Geophysical Union. All Rights Reserved. Source

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