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Non-linear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The force-free assumption is a valid approximation at coronal heights, but for the…

Coronal holes are the coolest and darkest regions of the solar atmosphere, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the…

Solar and Stellar Astrophysics · Physics 2011-09-21 D. Banerjee , G. R. Gupta , L. Teriaca

Here we report on the unique observation of flaring coronal loops at the solar limb using high resolution imaging spectropolarimetry from the Swedish 1-meter Solar Telescope. The vantage position, orientation and nature of the chromospheric…

The extended minimum of Solar Cycle 23, the extremely quiet solar-wind conditions prevailing, and the mini-maximum of Solar Cycle 24 drew global attention and many authors have since attempted to predict the amplitude of the upcoming Solar…

Solar and Stellar Astrophysics · Physics 2020-12-07 K. Sasikumar Raja , P. Janardhan , Susanta Kumar Bisoi , Madhusudan Ingale , Prasad Subramanian , K. Fujiki , Milan Maksimovic

Aims. We aim to characterise the magnetism of a large fraction of the north polar region close to a maximum of activity, when the polar regions are reversing their dominant polarity. Methods. We make use of full spectropolarimetric data…

Solar and Stellar Astrophysics · Physics 2020-04-08 A. Pastor Yabar , M. J. Martínez González , M. Collados

The magnetic field shapes the structure of the solar corona but we still know little about the interrelationships between the coronal magnetic field configurations and the resulting quasi-stationary structures observed in coronagraphic…

We present a novel experiment with the capacity to independently measure both the electron density and the magnetic field of the solar corona. We achieve this through measurement of the excess Faraday rotation due to propagation of the…

Astrophysics · Physics 2009-11-13 S. M. Ord , S. Johnston , J. Sarkissian

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which…

We report results of an in-depth numerical investigation of three-dimensional projection effects which could influence the observed loop-like structures in an optically thin solar corona. Several archetypal emitting geometries are tested,…

Solar and Stellar Astrophysics · Physics 2023-11-13 Vadim M. Uritsky , James A. Klimchuk

The coronal magnetic field above a particular photospheric region will vanish at a certain number of points, called null points. These points can be found directly in a potential field extrapolation or their density can be estimated from…

Astrophysics · Physics 2009-11-13 D. W. Longcope , C. E. Parnell

High-speed solar wind streams emanating from coronal holes are frequently impinging on the Earth's magnetosphere causing recurrent, medium-level geomagnetic storm activity. Modeling high-speed solar wind streams is thus an essential element…

Coronal holes are recognized as the primary sources of heliospheric open magnetic flux (OMF). However, a noticeable gap exists between in-situ measured OMF and that derived from remote sensing observations of the Sun. In this study, we…

It has long been known that the high-speed stream (HSS) peak velocity at Earth directly depends on the area of the coronal hole (CH) on the Sun. Different degrees of association between the two parameters have been shown by many authors. In…

In this review, I focus on the structure and evolution of the coronal magnetic fields modelled from observations. The development of instruments measuring the photospheric and chromospheric magnetic fields with a high spatial and time…

Solar and Stellar Astrophysics · Physics 2011-01-18 Stephane Regnier

Understanding the magnetic fields of the Sun is essential for unraveling the underlying mechanisms driving solar activity. Integrating topological data analysis techniques into these investigations can provide valuable insights into the…

Solar and Stellar Astrophysics · Physics 2024-01-31 Pablo Santamarina Guerrero , Yukio Katsukawa , Shin Toriumi , David Orozco Suárez

We analyse observations of a saddle-like structure in the corona above the western limb of the Sun on 2017 July 18. The structure was clearly outlined by coronal loops with typical coronal temperature no more than 1 MK. The dynamics of…

Solar and Stellar Astrophysics · Physics 2018-07-04 Boris Filippov

Solar image analysis relies on the detection of coronal holes for predicting disruptions to earth's magnetic field. The coronal holes act as sources of solar wind that can reach the earth. Thus, coronal holes are used in physical models for…

Solar and Stellar Astrophysics · Physics 2022-07-21 Venkatesh Jatla

Seven different models are applied to the same problem of simulating the Sun's coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated…

The solar minima between solar cycles 22-23, 23-24 and 24-25 are the best observed minima on record. In situ solar wind and interplanetary magnetic field measurements by the WIND and ACE spacecraft at L1 with one-hour cadence are explored…

Solar and Stellar Astrophysics · Physics 2024-04-18 P. J. Steyn , D. Johnson , G. J. J. Botha , S. Régnier

The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random…

Solar and Stellar Astrophysics · Physics 2016-01-22 R. B. Dahlburg , G. Einaudi , B. D. Taylor , I. Ugarte-Urra , H. P. Warren , A. F. Rappazzo , M. Velli