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Solar wind turbulence is anisotropic with respect to the mean magnetic field. Anisotropy leads to ambiguity when interpreting in-situ turbulence observations in the solar wind because an apparent change in the measurements could be due…

Solar and Stellar Astrophysics · Physics 2022-01-12 L. -L. Zhao , G. P. Zank , L. Adhikari , M. Nakanotani

Using magnetographic data provided by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we analyzed the structure of magnetic fields and vertical electric currents in six active regions (ARs) with different level…

Solar and Stellar Astrophysics · Physics 2020-02-19 Yuriy A. Fursyak , Alexander S. Kutsenko , Valentina I. Abramenko

We construct a magnetic helicity conserving dynamo theory which incorporates a calculated magnetic helicity current. In this model the fluid helicity plays a small role in large scale magnetic field generation. Instead, the dynamo process…

Astrophysics · Physics 2009-10-31 Ethan T. Vishniac , Jungyeon Cho

To investigate the power and spectral index anisotropy in the inertial range of solar wind turbulence, we use 70 intervals of electric field data accumulated by Cluster spacecraft in the free solar wind. We compute the electric field…

Space Physics · Physics 2020-09-24 Deepali , Supratik Banerjee

We investigate the anisotropy of Alfv\'enic turbulence in the inertial range of slow solar wind and in both driven and decaying reduced magnetohydrodynamic simulations. A direct comparison is made by measuring the anisotropic second-order…

Space Physics · Physics 2012-08-20 C. H. K. Chen , A. Mallet , T. A. Yousef , A. A. Schekochihin , T. S. Horbury

In the past few years suggestions have emerged that the solar magnetic field might have a bi-helical component with oppositely polarized magnetic fields at large and small scales, and that the shedding of such fields may be crucial for the…

Astrophysics · Physics 2009-11-07 T. A. Yousef , A. Brandenburg

We use magnetic helicity to characterise solar wind fluctuations at proton-kinetic scales from Wind observations. For the first time, we separate the contributions to helicity from fluctuations propagating at angles quasi-parallel and…

In a previous paper, we found that proton temperatures are clearly associated with the proton-scale turbulence in the solar wind, and magnetic helicity signature appears to be an important indicator in the association. Based on 15 years of…

Space Physics · Physics 2021-01-27 G. Q. Zhao , Y. Lin , X. Y. Wang , H. Q. Feng , D. J. Wu , H. B. Li , A. Zhao , Q. Liu

CrI$_{3}$ is considered to be a promising candidate for spintronic devices and data storage. We derived the Heisenberg Hamiltonian for CrI$_{3}$ from density functional calculations using the Liechtenstein formula. Moreover, the…

Materials Science · Physics 2023-04-24 Hung Ba Tran , Hiroyoshi Momida , Yu-ichiro Matsushita , Koun Shirai , Tamio Oguchi

We analyze the evolution of the interplanetary magnetic field spatial structure by examining the inner heliospheric autocorrelation function, using Helios 1 and Helios 2 "in situ" observations. We focus on the evolution of the integral…

Solar and Stellar Astrophysics · Physics 2011-10-19 M. E. Ruiz , S. Dasso , W. H. Matthaeus , E. Marsch , J. M. Weygand

The velocity field in the lower solar atmosphere undergoes strong interactions with magnetic fields. Many authors have pointed out that power is reduced by a factor between two and three within magnetic regions, depending on frequency,…

Solar and Stellar Astrophysics · Physics 2015-06-12 F. Giannattasio , M. Stangalini , D. Del Moro , F. Berrilli

Identifying solar active regions (ARs), which consist of one or more pairs of magnetic patches with opposite polarities, is essential due to their significant role in dynamic solar atmospheric phenomena. In this study, we analyze ARs during…

Solar and Stellar Astrophysics · Physics 2025-09-16 Zahra Tajik , Hasan Rezaei , Mehdi Simiari , Hossien Safari

The anisotropy of solar wind turbulence is a critical issue in understanding the physics of energy transfer between scales and energy conversion between fields and particles in the heliosphere. Using the measurement of \emph{Parker Solar…

Cosmological magnetic fields induce temperature and polarization fluctuations in the cosmic microwave background (CMB) radiation. A cosmological magnetic field with current amplitude of order $10^{-9}$ G is detectable via observations of…

Astrophysics · Physics 2009-11-10 Tina Kahniashvili , Bharat Ratra , ;

It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of SDO, earlier studies have mostly used MDI/SOHO line of sight magnetograms and assumed that magnetic fields…

Solar and Stellar Astrophysics · Physics 2015-05-20 Yongliang Song , Mei Zhang

Solar activity can be witnessed in the form of sunspots and active regions, where the magnetic field is enhanced by up to a factor 1000 as compared to that of the quiet Sun. In addition, solar activity manifests itself in terms of flares,…

Solar and Stellar Astrophysics · Physics 2025-07-25 Gottfried Mann , Frédéric Schuller

Expanding on an earlier work that relied on linear force-free magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free…

Solar and Stellar Astrophysics · Physics 2015-06-11 M. K. Georgoulis , K. Tziotziou , N. -E. Raouafi

Dynamos in the Sun and other bodies tend to produce magnetic fields that possess magnetic helicity of opposite sign at large and small scales, respectively. The build-up of magnetic helicity at small scales provides an important saturation…

Solar and Stellar Astrophysics · Physics 2010-11-30 Piyali Chatterjee , Gustavo Guerrero , Axel Brandenburg

Magnetic helicity is a fundamental constraint in both ideal and resistive magnetohydrodynamics. Measurements of magnetic helicity density on the Sun and other stars are used to interpret the internal behaviour of the dynamo generating the…

Solar and Stellar Astrophysics · Physics 2022-11-03 Parag Gupta , Radostin D. Simitev , David MacTaggart

Measuring the magnetic helicity distribution in the solar corona can help in understanding the trigger of solar eruptive events because magnetic helicity is believed to play a key role in solar activity due to its conservation property. A…

Solar and Stellar Astrophysics · Physics 2013-07-11 K. Dalmasse , E. Pariat , G. Valori , P. Démoulin , L. M. Green