Analysis and forecasting of Coronal mass ejection space Weather effects

Koronini izbačaji i Sunčevi bljeskovi su najsilovitiji eruptivni procesi na Suncu te se nerijetko smatraju glavnim pokretačima svemirskih vremenskih prilika. Praćenjem i predviđanjem svemirskih vremenskih prilika, odnosno stanja u međuplanetarnom prostoru, bliskoj okolici Zemlje te njenoj magnetosferi, ionosferi i termosferi bavi se svemirska prognostika (eng. "space weather"). Iako je to relativno novo područje istraživanja, usko vezano uz razvoj ljudske tehnologije (posebice svemirskih letjelica), može se tvrditi da je njen razvoj započeo davno prije "doba satelita" sa prvim opažanjima Sunčeve aktivnosti. Ljudska tehnologija napredovala je značajno u posljednjem stoljeću te je postala i osjetljivija na Sunčevu aktivnost. Živimo u doba satelita, aviona, elektroenergetskih sustava i svemirskih misija, koje izravno mogu biti pod (negativnim) utjecajem Sunčevih eruptivnih procesa. Stoga je shvaćanje i predviđanje takvih događaja te njihovih učinaka neophodno za moderno društvo.Coronal mass ejections (CMEs) are most powerful eruptions in the solar system. They are driven by the energy explosively released from the coronal magnetic field and are often associated with solar flares, representing a dissipative energy release that causes a wide range of electromagnetic emission at different wavelengths, from radio waves to gamma rays. CMEs have strong impact on space weather - they can cause severe problems in the modern human technology and represent a significant factor in human space-born missions planning. Therefore, they are an important element of space weather forecast, which is based on a numerous ground-based and space-born observations, as well as a variety of modeling and empirical forecast methods. Namely, CMEs drive the most intense geomagnetic storms and largest short-term depressions in galactic cosmic ray (GCR) flux, so called Forbush decreases. Both of these are direct consequences of the near-Earth interplanetary conditions due to CME passage over the Earth. Currently, probabilistic forecast methods turned out to be the most efficient procedure for predicting the geomagnetic storm strength and Forbush decrease magnitude based on the remote solar observations. The presented statistical analysis reveales that both geomagnetic storms and Forbush decreases are stronger for faster and wider CMEs, associated with stronger flares originating closer to the center of the solar disc, especially when they are involved in a CME-CME interaction. Statistical relationships are employed in empirical statistical modeling based on the geometric distribution, which can provide forecast of the CME related geo- and GCR-effectiveness (i.e. geomagnetic storm strength and Forbush decrease magnitude). The evaluation reveales that the forecast is less reliable if it is more specific, and gives a relatively good prediction whether or not strongest storms and significant Forbush decreases will occur. The main advantage is in the early warning, based on the input parameters that are not necessarily satellite-dependent. Based on the presented research, two online forecast tools have been developed, available at Hvar Observatory web page. In addition, geomagnetic forecast model has been implemented in the "COMESEP alert system", which is the first fully automatic system for detection of CMEs and solar flares, forecasting the CME arrival as well as their potentially hazardous impact

Primjena pristupa povijesnoga urbanog krajolika u izradi konzervatorskih podloga za kulturno-povijesne cjeline naselja

Kulturno-povijesne cjeline naselja izložene su gubitku svojih obilježja i vrijednosti zbog promjena koje izazivaju gospodarske okolnosti, klimatske promjene i katastrofe te sociološki i demografski trendovi, stoga zahtijevaju nove pristupe u planiranju. Iako se planiranje razvoja načelno poziva na očuvanje identitetskih obilježja, u praksi se ne osiguravaju učinkoviti alati za očuvanje naslijeđa i održivi razvoj. Važeća prostorno-planska dokumentacija po svojem sadržaju ne odgovara zahtjevima povijesnih cjelina jer postojeći način izrade urbanističkih planova nije prilagođen specifičnostima povijesnih područja. Također nedostaju konzervatorske podloge koje bi sustavno istražile i vrednovale urbana tkiva povijesnih naselja te na temelju vrednovanja svih sastavnica izradile strategije za očuvanje i održivi razvoj. U članku se na temelju pregleda teorijskog okvira te na primjeru Konzervatorske podloge kulturno-povijesne cjeline grada Malog Lošinja istražuje primjena metodologije izrade konzervatorskih podloga prema pristupu povijesnoga urbanog krajolika. Izrada konzervatorskih podloga prema metodologiji povijesnoga urbanog krajolika sagledavanjem svih njegovih sastavnica te objektiviziranjem vrednovanja omogućit će znanstvenu utemeljenost odluka o budućnosti naslijeđa unutar konzervatorske, urbanističke i arhitektonske struke

Heliospheric Evolution of Magnetic Clouds

Interplanetary evolution of eleven magnetic clouds (MCs) recorded by at least two radially aligned spacecraft is studied. The in situ magnetic field measurements are fitted to a cylindrically symmetric Gold-Hoyle force-free uniform-twist flux-rope configuration. The analysis reveals that in a statistical sense the expansion of studied MCs is compatible with self-similar behavior. However, individual events expose a large scatter of expansion rates, ranging from very weak to very strong expansion. Individually, only four events show an expansion rate compatible with the isotropic self-similar expansion. The results indicate that the expansion has to be much stronger when MCs are still close to the Sun than in the studied 0.47 - 4.8 AU distance range. The evolution of the magnetic field strength shows a large deviation from the behavior expected for the case of an isotropic self-similar expansion. In the statistical sense, as well as in most of the individual events, the inferred magnetic field decreases much slower than expected. Only three events show a behavior compatible with a self-similar expansion. There is also a discrepancy between the magnetic field decrease and the increase of the MC size, indicating that magnetic reconnection and geometrical deformations play a significant role in the MC evolution. About half of the events show a decay of the electric current as expected for the self-similar expansion. Statistically, the inferred axial magnetic flux is broadly consistent with it remaining constant. However, events characterized by large magnetic flux show a clear tendency of decreasing flux.Comment: 64 pages, 10 figure

A statistical study of long-term evolution of coronal hole properties as observed by SDO

The study of the evolution of coronal holes (CHs) is especially important in the context of high-speed solar wind streams (HSS) emanating from them. Stream interaction regions may deliver large amount of energy into the Earths system, cause geomagnetic storms, and shape interplanetary space. By statistically analysing 16 long-living CHs observed by the SDO, we focus on coronal, morphological and underlying photospheric magnetic field characteristics as well as investigate the evolution of the associated HSSs. We use CATCH to extract and analyse CHs using observations taken by AIA and HMI. We derive changes in the CH properties and correlate them to the CH evolution. Further we analyse the properties of the HSS signatures near 1au from OMNI data by manually extracting the peak bulk velocity of the solar wind plasma. We find that the area evolution of CHs mostly shows a rough trend of growing to a maximum followed by a decay. No correlation of the area evolution to the evolution of the signed magnetic flux and signed magnetic flux density enclosed in the projected CH area was found. From this we conclude that the magnetic flux within the extracted CH boundaries is not the main cause for its area evolution. We derive CH area change rates (growth and decay) of 14.2 +/- 15.0 * 10^8 km^2/day showing a reasonable anti-correlation (cc =-0.48) to the solar activity, approximated by the sunspot number. The change rates of the signed mean magnetic flux density (27.3 +/- 32.2 mG/day) and the signed magnetic flux (30.3 +/- 31.5 * 10^18 Mx/day) were also found to be dependent on solar activity (cc =0.50 and cc =0.69 respectively) rather than on the individual CH evolutions. Further we find that the CH area-to-HSS peak velocity relation is valid for each CH over its evolution but revealing significant variations in the slopes of the regression lines.Comment: Accepted at A&