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Max Planck Institute fur Sonnensystemforschung, Lindau
Njemačka
Astrophysikalisches Institute, Postdam
Njemačka
K.U. Leuven-Centrum voor Plasma-Astrofysica, Leuven
Belgija
NASA Marshall Space Flight Center, Huntsville, USA
Sjedinjene američke države
Harvard-Smithsonian Center for Astrophysics, Cambridge
Sjedinjene američke države
Short description of project
Current Sheets (CSs) are a basic prerequisite for magnetic reconnection. The goal of the proposed research is to define CS properties in the solar athmosphere and their signatures in the interplanetary medium, and to understand their role in the developments of solar eruptive events. The project was inspired by recently acquired ground and space based observations that reveal CSs signatures at the time of flare/CMEs (Coronal Mass Ejections), in the chromosphere, in the corona and in the interplanetary medium. At the same time, theoretical studies predict the formation of CSs in different models/configurations, but theories and observational results have not yet developed an interaction efficient enough to allow us to construct an unified scenario. This proposal aims at maximizing the synergy between observers/data analysts and theoreticians, so as to enable a significant advance in our understanding of CS behaviour and properties. A further motivation for studying CSs is related to the expected electric fields in CSs that may well be the source of solar energetic particle (SEP) events that create a serious hazard for human being and their machines. Hence, the refinement of CS models has a pragmatic benefit in helping forecast the production of energetic particles, an issue of growing importance for our present society.
Short description of the task performed by Croatian partner
Observational approach: SOHO experiments and results have advanced the work, still far from being completed, on the remote identification and characterization of CSs, but the in situ analysis
of the residue of the reconnection process that created the CS has not yet been satisfactorily developed. However, neither remote, nor in situ analyses can give unique answers unless they
are merged and considered as part of the same phenomenon. Since this issue is central to our
proposal, in situ measurements will be joined with remote observations to convey information on
the still-to-be-defined in situ signatures of CSs, on the configuration of the region where CMEs
originate, and on the mechanism that generates CMEs. The breakout model predicts reconnection to occur above the flux-rope and, at later times, also below it, while, e.g., the catastrophe model predicts a long CS to extend from the flux rope towards the underlying growing arcade of loops: identification of hot CS plasma ahead of the flux rope in in situ data directly links to a CME model. Analysis of composition, ionization state, and energetic particle signatures in the context of the local magnetic field will be used to define the plasma - magnetic field context and to learn whether this is consistent with model predictions and properties of the ejecta inferred from remote observations. This will be
done for specific well-observed events and in a statistical analysis of groups of events. Remotely
acquired data sources will mainly be SOHO, the MLSO (Mauna Loa Solar Observatory) MK4
coronagraph, TRACE (Transition Region and Coronal Explorer), RHESSI (Reuven Ramaty High
Energy Solar Spectroscopic Imager), SMEI (Solar Mass Ejection Imager) and various groundbased
magnetographs and radio dynamic spectra and Nancay radioheliograph observations.
Modeling approach: there is specific synergy between the observational approach and models of CMEs. In particular, the so-called a posteriori approach aims to reproduce the characteristics of CMEs at the Sun, starting with their in situ properties. Simulations of the CSs themselves will be used to understand the observed heating and particle acceleration. Models of CME origins, as mentioned above, will be compared with the in situ and remote measurements to test consistency and learn how to use the in situ data to better identify various parts of the ejecta. Also, MHD and kinetic CS simulations will be developed as an independent complementary issue.
Ovo web sjedište koristi tehnologiju "kolačića" (eng. cookie) da bi se korisnicima prikazao dinamičan i personaliziran sadržaj, te su oni nužni za ispravan rad. Ako nastavite pregledavati ove stranice, kolačići će biti korišteni u suradnji s vašim preglednikom Weba.
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