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 Sciences2- Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University

3- Charles University in Prague, Czech Republic

Meeting on Solar Wind Turbulence, Kennebunkport, June 4-7, 2013

Contact person: Maria Riazantseva orearm@gmail.comGeorgy Zastenker gzastenk@iki.rssi.ru

BMSW instrument

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 (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.

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)

principle of measurementsby BMSW instrument

CollectorC2, C4 – grounding grid; C3 – deceleration grid; C1 – suppressor grid

Typical energetic spectrum distribution

Curr

ent o

n co

llect

or

Voltage on control gridVp

Tp

The comparison of SPECTR-R (BMSW) measurements of plasma parameters with WIND (SWE) data (14/08/2012)

An example of power spectrum of ion flux fluctuations on 20 min interval

break frequency Fcrit=1.3 Hz

An example of power spectrum of stream direction fluctuations on the same 20 min interval

break frequency Fcrit=0.53 Hz

Turbulent properties of the fluctuations of solar wind plasma flux on ion-kinetic scale

The frequency spectra of solar wind ion flux variations are clearly separated on two branches with significantly different spectral indexes

The histogram of the break frequencies and spectral indexes for spectra of fluctuations of the

ion flux value and it’s direction.

Fcrit_Flux=(1.40±0.63) HzFcrit_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)

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

Power spectrum of electron density fluctuations obtained using measurements

of ARTEMIS (Chen et.al,2012 )

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 magnetic field fluctuations in accordance with Cluster measurements

(Alexandrova et. al.,2009)

Intermittency for small scale ion flux variations

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.

intermittency

(а)

(b)

intermittency

Noise

influence

Noise

influence

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.