Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

Comparison of statistical downscaling methods with respect to extreme events over Europe: Validation results from the perfect predictor experiment of the COST Action VALUE

Abstract: Special Issue: VALUE: Validating and Integrating Downscaling Methods for Climate Change Research.

Continuous spectrum for a class of nonhomogeneous differential operators

Abstract: We study the boundary value problem $$-{\rm div}((| abla u|^{p_1(x)-2}+| abla u|^{p_2(x)-2}) abla u)=\lambda|u|^{q(x)-2}u$$ in Ω, u = 0 on ∂Ω, where Ω is a bounded domain in $$\mathbb{R}^N$$ with smooth boundary, λ is a positive real number, and the continuous functions p 1, p 2, and q satisfy 1 < p 2(x) < q(x) < p 1(x) < N and $$\max_{y\in\overline\Omega}q(y) < \frac{N p_2(x)}{N-p_2(x)}$$ for any $$x\in\overline\Omega$$ . The main result of this paper establishes the existence of two positive constants λ0 and λ1 with λ0 ≤ λ1 such that any $$\lambda\in[\lambda_1,\infty)$$ is an eigenvalue, while any $$\lambda\in(0,\lambda_0)$$ is not an eigenvalue of the above problem.

Solar Sources of Interplanetary Coronal Mass Ejections During the Solar Cycle 23/24 Minimum

Abstract: We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun–Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120∘. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were “stealth” CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤ 20∘) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME.