Complexity of Magnetic-field Turbulence at Reconnection Exhausts in the Solar Wind at 1 au

Magnetic reconnection is a complex mechanism that converts magnetic energy into particle kinetic energy and plasma thermal energy in space and astrophysical plasmas. In addition, magnetic reconnection and turbulence appear to be intimately related in plasmas. We analyze the magnetic-field turbulence at the exhaust of four reconnection events detected in the solar wind using the Jensen–Shannon complexity-entropy index. The interplanetary magnetic field is decomposed into the LMN coordinates using the hybrid minimum variance technique. The first event is characterized by an extended exhaust period that allows us to obtain the scaling exponents of higher-order structure functions of magnetic-field fluctuations. By computing the complexity-entropy index we demonstrate that a higher degree of intermittency is related to lower entropy and higher complexity in the inertial subrange. We also compute the complexity-entropy index of three other reconnection exhaust events. For all four events, the B L component of the magnetic field displays a lower degree of entropy and higher degree of complexity than the B M and B N components. Our results show that coherent structures can be responsible for decreasing entropy and increasing complexity within reconnection exhausts in magnetic-field turbulence.

Magnetic field turbulence studies aboard the China Seismo-Electromagnetic Satellite and related ground based phenomena

<p>With a new type of a scalar magnetometer, the Coupled Dark State Magnetometer (CDSM) aboard the China Seismo-Electromagnetic Satellite (CSES) mission, we observed magnetic field fluctuations in the period mid July 2018 until mid November 2018. <br>The measurement range of the CDSM is from 1000 nT up to 100000 nT and the accuracy 0.19 nT (1), the operational performance is discussed in (2). We are using 1 Hz data in the latitude range -65 degree to +65 degree, CSES has an altitude of approx. 507 km in Sun synchronous polar configuration with 97.4 degree inclination. <br>We analyzed the total magnetic field turbulence by converting the time series into thermodynamic parameters, e.g. entropy, finally these results have been compared with ground based seismic and volcanic events.</p><p>Ref:<br>(1) Pollinger, A., et al.: Coupled dark state magnetometer for the China Seismo-Electromagnetic Satellite, Measurement Science and Technology, 29, 9, 2018. https://doi.org/10.1088/1361-6501/aacde4<br>(2) Pollinger, A., et al.: In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite, Geosci. Instrum. Method. Data Syst., 9, 275–291, 2020. https://doi.org/10.5194/gi-9-275-2020</p>

Plasma and Magnetic Field Turbulence in the Earth’s Magnetosheath at Ion Scales

Crossing the Earth’s bow shock is known to crucially affect solar wind plasma including changes in turbulent cascade. The present review summarizes results of more than 15 years of experimental exploration into magnetosheath turbulence. Great contributions to understanding turbulence development inside the magnetosheath was made by means of recent multi-spacecraft missions. We introduce the main results provided by them together with first observations of the turbulent cascade based on direct plasma measurements by the Spektr-R spacecraft in the magnetosheath. Recent results on solar wind effects on turbulence in the magnetosheath are also discussed.

Interpretation of the power spectrum of the quiet Sun photospheric turbulence

ABSTRACT Observational power spectra of the photospheric magnetic field turbulence, of the quiet-sun, were presented in a recent paper by Abramenko & Yurchyshyn. Here, I focus on the power spectrum derived from the observations of the Near InfraRed Imaging Spectrapolarimeter operating at the Goode Solar Telescope. The latter exhibits a transition from a power law with index −1.2 to a steeper power law with index −2.2, for smaller spatial scales. This paper presents an interpretation of this change. Furthermore, this interpretation provides an estimate for the effective width of the turbulent layer probed by the observations. The latter turns out to be practically equal to the depth of the photosphere.

Estimating density and magnetic field turbulence in solar flares using radio zebra observations

Context. In solar flares the presence of magnetohydrodynamic turbulence is highly probable. However, information about this turbulence, especially the magnetic field turbulence, is still very limited. Aims. In this paper we present a new method for estimating levels of the density and magnetic field turbulence in time and space during solar flares at positions of radio zebra sources. Methods. First, considering the double-plasma resonance model of zebras, we describe a new method for determining the gyro-harmonic numbers of zebra stripes based on the assumption that the ratio R = Lb/Ln (Ln and Lb are the density and magnetic field scales) is constant in the whole zebra source. Results. Applying both the method proposed in this work and one from a previous paper for comparison, in the 14 February 1999 zebra event we determined the gyro-harmonic numbers of zebra stripes. Then, using the zebra-stripe frequencies with these gyro-harmonic numbers, we estimated the density and magnetic field in the zebra-stripe sources as n = (2.95−4.35) × 1010 cm−3 and B = 17.2−31.9 G, respectively. Subsequently, assuming that the time variation of the zebra-stripe frequencies is caused by the plasma turbulence, we determined the level of the time varying density and magnetic field turbulence in zebra-stripe sources as |Δn/n|t = 0.0112–0.0149 and |ΔB/B|t = 0.0056–0.0074, respectively. The new method also shows deviations in the observed zebra-stripe frequencies from those in the model. We interpret these deviations as being caused by the spatially varying turbulence among zebra-stripe sources; i.e., they depend on their gyro-harmonic numbers. Comparing the observed and model zebra-stripe frequencies at a given time, we estimated the level of this turbulence in the density and magnetic field as |Δn/n|s = 0.0047 and |ΔB/B|s = 0.0024. We found that the turbulence levels depending on time and space in the 14 February 1999 zebra event are different. This indicates some anisotropy of the turbulence, probably caused by the magnetic field structure in the zebra source.

Star formation efficiency of magnetized, turbulent and rotating molecular cloud

The formation of stars constitutes one of the basic problems in astrophysics. Understanding star formation efficiency of molecular clouds (MCs) of a galaxy is necessary for studying the galactic evolution. Present data and theoretical formulations show that the structure and dynamics of the interstellar medium (ISM) are extremely complex. Therefore, there is no simple model that can explain adequately the star formation efficiency of MCs because of its complex nature. The initial mass of the cloud needed for collapse varies based on the environment in which the cloud resides and the strength of its magnetic field, turbulence, as well as the speed of rotation. In this paper, we estimate the star formation efficiency by combining pre-determined models and the critical mass formulated by Kumssa & Tessema (2018).

Coherent structures and magnetic reconnection in photospheric and interplanetary magnetic field turbulence

In this paper it is shown that rope-rope magnetic reconnection in the solar wind can enhance multifractality in the inertial subrange and drive intermittent magnetic field turbulence. Additionally, it is shown that Lagrangian coherent structures can unveil the transport barriers of magnetic elements in the quiet Sun.