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Spectral Properties of high frequency fluctuations of solar wind plasma

Meeting on Solar Wind Turbulence, Kennebunkport, June 4-7, 2013. Spectral Properties of high frequency fluctuations of solar wind plasma parameters: SPECTR-R data M. Riazantseva 1,2 , G. Zastenker 1 , J. Safrankova 4 , Z. Nemecek 4 , L. Prech 4

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Spectral Properties of high frequency fluctuations of solar wind plasma

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  1. Meeting on Solar Wind Turbulence, Kennebunkport, June 4-7, 2013 Spectral Properties of high frequency fluctuations of solar wind plasma parameters: SPECTR-R data M. Riazantseva1,2, G. Zastenker1, J. Safrankova4, Z. Nemecek4, L. Prech4 1- Space Research Institute, Russian Academy of Sciences 2- Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University 3- Charles University in Prague, Czech Republic Contact person: Maria Riazantsevaorearm@gmail.com GeorgyZastenkergzastenk@iki.rssi.ru

  2. BMSW instrument (experiment PLASMA-F) on board of spacecraft SPECTR-R • SPECTR-R: • Launched 18 July 2011 • highly elliptical orbit • period of revolution 8.3 days • Perigee 576 km;  • apogee 340000 km = 53 Re;  • inclination 51.3 deg. • Measurements of: • - Solar wind ion flux value and direction (time resolution 30 ms) • Solar wind plasma parameters in swepping mode (most of the time) : proton density , bulk speed, temperature, alfa particles/proton ratio • ( resolution 3 s) • Solar wind plasma parameters in adaptive mode (separate time intervals): proton density, bulk speed and temperature (resolution 30 ms) BMSW instrument • Tasks of the study: • -Turbulence in solar wind and magnetosheath on the scale of the ion dissipative range • Study of small scale discontinuities in the solar wind and magnetosheath • Study of fine structures of fronts of discontinuities (for example shocks)

  3. Typical energetic spectrum distribution principle of measurements by BMSW instrument Collector C2, C4 – grounding grid; C3 – deceleration grid; C1 – suppressor grid Current on collector Tp Vp Voltage on control grid The comparison of SPECTR-R (BMSW) measurements of plasma parameters with WIND (SWE) data (14/08/2012)

  4. Turbulent properties of the fluctuations of solar wind plasma flux on ion-kinetic scale An example of power spectrum of stream direction fluctuations on the same 20 min interval break frequency Fcrit=0.53 Hz An example of power spectrumof ion flux fluctuations on 20 min interval break frequency Fcrit=1.3 Hz The frequency spectra of solar wind ion flux variations are clearly separated on two branches with significantly different spectral indexes

  5. The histogram of the break frequencies and spectral indexesforspectra of fluctuations of the ion flux value and it’s direction. Fcrit_Flux=(1.40±0.63) Hz Fcrit_alfa=(0.48±0.16) Hz <Р1_Flux>= -1.52±(0.27) <P1_alfa>= -1.80±(0.46) <Р2_Flux>= -2.84 ± (0.27) <P2_alfa>= -2.43 ± (0.37)

  6. The comparison of spectra for ion density (a), bulk speed (b) and thermal speed (c) fluctuations by measurements of BMSW instrument in adaptive mode (time resolution 30 ms) Safrankova et. al., PRL, 2013

  7. The comparison of the spectra of fluctuations measured by SPECTR-R with published ones. Power spectrum of magnetic field fluctuations in accordance with HELIOS-2 and WIND measurements (Bruno et. al.,2004) Power spectrum of electron density fluctuationsobtained using measurements of ARTEMIS (Chen et.al,2012 ) Power spectrum of magnetic field fluctuations in accordance with Cluster measurements (Alexandrova et. al.,2009)

  8. Intermittency for small scale ion flux variations (а) intermittency Noise influence intermittency (b) Noise influence Probability distribution function (PDF) of ion flux variations on scale 30 ms (solid line) and corresponding Gaussian distribution (dashed line). Variations of the solar wind parameters are intermittent on the small scale up to scale where influence of the noise is significant. Behavior of flatness (4th order of moment) coefficient for ion flux fluctuations (a) and its direction (b) in the range 0.03-100 s.

  9. Conclusions: • BMSW instrument measurements can extend the frequency range of spectra of fluctuations of plasma parameters in the solar wind up to ~ 10 Hz; • The frequency spectra of solar wind ion flux variations are clearly separated on two branches and forms low and high frequency ranges. This break frequency is about 1.4 Hz on the average for variations of ion flux value and 0.5 Hz for variations of stream direction. • The spectral indices of variations of ion flux value (and polar angle) on the averages is about -1.5 (and -1.8) in the low frequency range and about -2.8 (and -2.4) in the high frequency range. • We did not find the clear dependence of values of spectral plasma parameters on the solar wind parameters, proton cyclotron frequency, inertial length etc. and this study needs to be continued using larger statistic. • The PDF show the high level of the intermittency for fluctuations on ~0.1-10 s scale.

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