Zobrazeno 1 - 10
of 498
pro vyhledávání: '"I. I. Virtanen"'
Publikováno v:
Annales Geophysicae, Vol 42, Pp 355-369 (2024)
Auroral electron precipitation during a substorm exhibits complex spatiotemporal variations which are still not fully understood, especially during the very dynamic phase immediately following the onset. Since during disturbed times, the auroral oval
Externí odkaz:
https://doaj.org/article/09c5b577794b4beeac580f55d8028823
Autor:
S. Oyama, K. Hosokawa, H. Vanhamäki, A. Aikio, T. Sakanoi, L. Cai, I. I. Virtanen, K. Shiokawa, N. Nishitani, A. Shinbori, Y. Ogawa
Publikováno v:
Geophysical Research Letters, Vol 50, Iss 14, Pp n/a-n/a (2023)
Abstract A thermospheric wind data set from a Fabry‐Perot interferometer (630 nm) and the ion velocity from a Dynasonde in Tromsø, Norway, was analyzed for nine winter seasons to study the dynamics of the thermosphere and F‐region ionosphere at
Externí odkaz:
https://doaj.org/article/46480dca218345279f66037e96bcbfeb
Publikováno v:
Atmospheric Measurement Techniques, Vol 15, Pp 3843-3857 (2022)
We propose a novel method for deconvolving incoherent scatter radar data to recover accurate reconstructions of backscattered powers. The problem is modelled as a hierarchical noise-perturbed deconvolution problem, where the lower hierarchy consists
Externí odkaz:
https://doaj.org/article/8de78de6abe149a2854dd2284cca8f69
Autor:
J. Norberg, I. I. Virtanen, L. Roininen, J. Vierinen, M. Orispää, K. Kauristie, M. S. Lehtinen
Publikováno v:
Atmospheric Measurement Techniques, Vol 9, Iss 4, Pp 1859-1869 (2016)
We validate two-dimensional ionospheric tomography reconstructions against EISCAT incoherent scatter radar measurements. Our tomography method is based on Bayesian statistical inversion with prior distribution given by its mean and covariance. We emp
Externí odkaz:
https://doaj.org/article/e97e1094c99e4da4bed572f37d928b33
Publikováno v:
Annales Geophysicae, Vol 27, Pp 2799-2811 (2009)
Both ionospheric and weather radar communities have already adopted the method of transmitting radar pulses in an aperiodic manner when measuring moderately overspread targets. Among the users of the ionospheric radars, this method is called Aperi
Externí odkaz:
https://doaj.org/article/82eb02e2ddf9413193e137fb3364a90f
Publikováno v:
Annales Geophysicae, Vol 26, Pp 2923-2927 (2008)
When statistical inversion of a lag profile is used to determine an incoherent scatter target, the posterior variance of the estimated target can be used to determine how well a set of transmission codes perform. In this work we present an incoher
Externí odkaz:
https://doaj.org/article/b1ce8b4127bc4dc7a9efb92d9f127c44
Publikováno v:
Annales Geophysicae, Vol 26, Pp 2291-2301 (2008)
A fast method for theoretically comparing the posteriori variances produced by different phase code sequences in incoherent scatter radar (ISR) experiments is introduced. Alternating codes of types 1 and 2 are known to be optimal for selected rang
Externí odkaz:
https://doaj.org/article/927099b51eae4ce7aad352a42401be57
Publikováno v:
Annales Geophysicae, Vol 26, Pp 2281-2289 (2008)
The EISCAT incoherent scatter radars routinely perform simultaneous measurements of E- and F-regions of the ionosphere. In addition several experiments exist for measuring pulse-to-pulse correlations from the D-region. However, the D-region experi
Externí odkaz:
https://doaj.org/article/5bbd1acc0f814b86a3cf168c7935518f
Publikováno v:
Annales Geophysicae, Vol 26, Pp 2419-2426 (2008)
We present a novel method for analyzing range and Doppler spread targets in the amplitude domain using linear statistical inversion. The result of the analysis is an estimate of the range dependent amplitude behaviour of the target backscatter dur
Externí odkaz:
https://doaj.org/article/27129e16f0b648378c4a3230725a80d3
Publikováno v:
Annales Geophysicae, Vol 26, Pp 571-581 (2008)
The present standard EISCAT incoherent scatter experiments are based on alternating codes that are decoded in power domain by simple summation and subtraction operations. The signal is first digitised and then different lagged products are calcula
Externí odkaz:
https://doaj.org/article/714d4ca754d2433d81b560312e44e0c6