STORM - Solar system plasma Turbulence:  Observations, inteRmittency and Multifractals

Solar system plasma Turbulence: Observations, inteRmittency and Multifractals

STORM started in January 2013 and ended in December 2015. The project is carried out by a Consortium of eight European institutes and universities led by the Belgian Institute for Space Aeronomy. STORM is devoted to a thorough analysis of solar system plasma turbulence from in-situ data gathered by spacecraft launched by the European Space Agency (ESA) and NASA. We investigated how the features of turbulence and intermittency vary with the solar activity and estimate the corresponding impact. We use electromagnetic field and plasma data provided by a core of three ESA spacecraft, Ulysses, Venus Express and the Cluster quartet, in coherence with data from other missions like ESA's Giotto and Rosetta, NASA's THEMIS, Cassini and Mars Global Surveyor. Complementary to the satellite databases we also studied the fluctuations of the geomagnetic field observed on ground. The analysis strategy adopted in STORM is built on the principle of increasing complexity, from lower order analyses (like, e.g., the Power Spectral Density - PSD) to higher order investigations (the Probability Distribution Functions – PDFs, Structure Functions - SFs, Fractals and Multifractals - MFs). The project made indeed a systematic survey, orbit by orbit, of data available from ESA data repositories and Principal Investigators. STORM produced catalogues of Power Spectral Density (PSD), Probability Distribution Functions (PDFs), partion functions and rank ordered multifractal spectra (MFs) at solar minimum (1997-1998, 2007-2008) and maximum (2000-2001) from data provided by Ulysses, Cluster, and Venus Express. Catalogues of the same type of analysis (PSD, PDFs, multifractal) were produced for magnetospheric data from Venus Express and Cluster, at solar minimum and maximum. Moreover the PSD, PDFs and multifractal analysis has been applied on geomagnetic data (nine global geomagnetic indices, AE, AL, AU, Dst, SYM-H, SYM-D, ASY-H, ASY-D, Dcm and data from individual Nordic observatories (Sodankylä, Nurmijärvi, and Belsk). Different types of turbulence models, like the p-model and the two-scale modified Cantor set models have been tested against solar wind and magnetospheric data.

The catalogues of analyzed data are organized like a functional database and structured according to the type of targeted system (solar wind/magnetosphere/geomagnetic indices), solar cycle phase (minimum versus maximum), type of analysis (PSD, PDFs, multifractal). The catalogues, available online from http://www.storm-fp7.eu, include 4094 PSD spectra, 9566 PDFs and 15633 multifractal (partition function based and Rank Ordered - ROMA) spectra. On the scientific side this huge collection of analyses provides new insight on turbulent processes in solar system plasmas. In a series of recent studies the members of STORM showed that : (1) a systematic survey of Ulysses data at solar minimum and maximum reveals that the magnetic intermittency exhibit a tendency to decrease with the heliocentric distance (Wawrzaszek et al., 2015); (2) statistically robust differences were found between the spectral properties of fast and slow wind magnetic turbulence at 0.72 astronomical units (in the vicinity of Venus) and at solar minimum (Teodorescu et al., 2015), (3) significant differences are found in the topology of the planetary magnetosheath turbulence between Venus and the Earth (Dwivedi et al., 2016, submitted); (4) the critical behavior of geomagnetic fluctuations suggest a dependence of the Dst index intermittency on the solar cycle phase but virtual independence of the fractal properties of AE on the solar cycle, pointing towards an intrinsic nonlinear behavior of the magnetosphere (Giannatasio et al., 2016, submitted). In addition to data analysis and scientific research STORM built an integrated library for non-linear analysis of time series that includes all the approaches adopted in STORM to investigate solar system plasma turbulence. This versatile analysis tool is prepared to offer the user a friendly environment tailored according to the STORM data analysis strategy, i.e. based on the principle of increasing complexity

Contact: marius.echim @ aeronomie.be

News

The International Workshop and School on "Solar system plasma turbulence, intermittency and multifractals (STORM 2015)” was organised in Mamaia, Romania, between September 6-13, 2015. The event focused on the quantitative experimental, theoretical and numerical investigation of turbulence, intermittency, fractal/multifractal features, waves and coherent structures interaction, criticality and non-linear cross-scale coupling.

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FP7 STORM & SHOCK Meeting in Brussels. A joint meeting of the two FP7 projects, STORM and SHOCK, took place in Brussels between March 24-25, 2015.

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STORM@AGU2014 Session on solar system plasma dynamical complexity and intermittency

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STORM@EGU2014: Session on solar system plasma turbulence.

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