Relationships between a potential field-source surface model of the coronal magnetic field and properties of the solar wind at 1 AU

1984 ◽  
Vol 89 (A6) ◽  
pp. 3957 ◽  
Author(s):  
S. T. Suess ◽  
J. M. Wilcox ◽  
J. T. Hoeksema ◽  
H. Henning ◽  
M. Dryer
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Potential Field ◽  
Coronal Magnetic Field ◽  
Surface Model ◽  
Source Surface ◽  
Field Source

scholarly journals An elliptic expansion of the potential field source surface model

2020 ◽  
Vol 638 ◽  
pp. A109
Author(s):  
M. Kruse ◽  
V. Heidrich-Meisner ◽  
R. F. Wimmer-Schweingruber ◽  
M. Hauptmann
Keyword(s):  
Magnetic Field ◽  
Potential Field ◽  
Three Dimensional ◽  
Coronal Magnetic Field ◽  
Magnetic Configuration ◽  
Surface Model ◽  
Source Surface ◽  
Field Source ◽  
Numerical Solver ◽  
Elliptical Models

Context. The potential field source surface model is frequently used as a basis for further scientific investigations where a comprehensive coronal magnetic field is of importance. Its parameters, especially the position and shape of the source surface, are crucial for the interpretation of the state of the interplanetary medium. Improvements have been suggested that introduce one or more additional free parameters to the model, for example, the current sheet source surface model. Aims. Relaxing the spherical constraint of the source surface and allowing it to be elliptical gives modelers the option of deforming it to more accurately match the physical environment of the specific period or location to be analyzed. Methods. A numerical solver is presented that solves Laplace’s equation on a three-dimensional grid using finite differences. The solver is capable of working on structured spherical grids that can be deformed to create elliptical source surfaces. Results. The configurations of the coronal magnetic field are presented using this new solver. Three-dimensional renderings are complemented by Carrington-like synoptic maps of the magnetic configuration at different heights in the solar corona. Differences in the magnetic configuration computed by the spherical and elliptical models are illustrated.

scholarly journals An integrated data-driven solar wind - CME numerical framework for space weather forecasting

2020 ◽  
Author(s):  
Nishant M. Narechania ◽  
Ljubomir Nikolic ◽  
Lucie Freret ◽  
Hans De Sterck ◽  
Clinton P. T. Groth
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Space Weather ◽  
Weather Forecasting ◽  
Coronal Magnetic Field ◽  
Data Driven ◽  
Source Surface ◽  
Field Source ◽  
Space Weather Forecasting ◽  
Semi Empirical

The development of numerical models and tools which have operational space weather potential is an increasingly important area of research. This study presents recent Canadian efforts toward the development of a numerical framework for Sun-to-Earth simulations of solar wind disturbances. This modular three-dimensional (3D) simulation framework is based on a semi-empirical data-driven approach to describe the solar corona and an MHD-based description of the heliosphere. In the present configuration, the semi-empirical component uses the Potential Field Source Surface (PFSS) and Schatten Current Sheet (SCS) models to derive the coronal magnetic field based on observed magnetogram data. Using empirical relations, solar wind properties are associated with this coronal magnetic field. Together with a Coronal Mass Ejection (CME) model, this provides inner boundary conditions for a global MHD model which is used to describe interplanetary propagation of the solar wind and CMEs. The proposed MHD numerical approach makes use of advanced numerical techniques. The 3D MHD code employs a finite-volume discretization procedure with limited piecewise linear reconstruction to solve the governing partial-differential equations. The equations are solved on a body-fitted hexahedral multi-block cubed-sphere mesh and an efficient iterative Newton method is used for time-invariant simulations and an explicit time-marching scheme is applied for unsteady cases. Additionally, an efficient anisotropic block-based refinement technique provides significant reductions in the size of the computational mesh by locally refining the grid in selected directions as dictated by the flow physics. The capabilities of the framework for accurately capturing solar wind structures and forecasting solar wind properties at Earth are demonstrated. Furthermore, a comparison with previously reported results and future space weather forecasting challenges are discussed.

scholarly journals Global Coronal Equilibria with Solar Wind Outflow

2021 ◽  
Vol 923 (1) ◽  
pp. 57
Author(s):  
Oliver E. K. Rice ◽  
Anthony R. Yeates
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Potential Field ◽  
Field Model ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Radial Magnetic Field ◽  
Similar Time ◽  
Magnetic Field Model ◽  
Magnetohydrodynamic Simulations

Abstract Given a known radial magnetic field distribution on the Sun’s photospheric surface, there exist well-established methods for computing a potential magnetic field in the corona above. Such potential fields are routinely used as input to solar wind models, and to initialize magneto-frictional or full magnetohydrodynamic simulations of the coronal and heliospheric magnetic fields. We describe an improved magnetic field model that calculates a magneto-frictional equilibrium with an imposed solar wind profile (which can be Parker’s solar wind solution, or any reasonable equivalent). These “outflow fields” appear to approximate the real coronal magnetic field more closely than a potential field, take a similar time to compute, and avoid the need to impose an artificial source surface. Thus they provide a practical alternative to the potential field model for initializing time-evolving simulations or modeling the heliospheric magnetic field. We give an open-source Python implementation in spherical coordinates and apply the model to data from solar cycle 24. The outflow tends to increase the open magnetic flux compared to the potential field model, reducing the well-known discrepancy with in situ observations.

PFSS-Based Solar Wind Forecast and the Radius of the Source-Surface

2017 ◽  
Vol 13 (S335) ◽  
pp. 307-309
Author(s):  
Ljubomir Nikolić
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Spherical Surface ◽  
Solar Wind Speed ◽  
Coronal Holes ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Field Source ◽  
Forecast Models ◽  
Field Lines

AbstractThe potential-field source-surface (PFSS) model of the solar corona is a widely used tool in the space weather research and operations. In particular, the PFSS model is used in solar wind forecast models which empirically associate solar wind properties with the numerically derived coronal magnetic field. In the PFSS model, the spherical surface where magnetic field lines are forced to open is typically placed at 2.5 solar radii. However, the results presented here suggest that setting this surface (the source-surface) to lower heights can provide a better agreement between observed and modelled coronal holes during the current solar cycle. Furthermore, the lower heights of the source-surface provide a better match between observed and forecasted solar wind speed.

scholarly journals Interplanetary conditions: lessons from this minimum

2011 ◽  
Vol 7 (S286) ◽  
pp. 168-178 ◽  
Author(s):  
J. Luhmann ◽  
C. O. Lee ◽  
P. Riley ◽  
L. K. Jian ◽  
C. T. Russell ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Minimum ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Field Source ◽  
Mass Fluxes ◽  
Solar Wind Structure ◽  
Cycle 24

AbstractInterplanetary conditions during the Cycle 23-24 minimum have attracted attention because they are noticeably different than those during other minima of the space age, exhibiting more solar wind stream interaction structures in addition to reduced mass fluxes and low magnetic field strengths. In this study we consider the differences in the solar wind source regions by applying Potential Field Source Surface models of the coronal magnetic field. In particular, we consider the large scale coronal field geometry that organizes the open field region locations and sizes, and the appearance of the helmet streamer structure that is another determiner of solar wind properties. The recent cycle minimum had an extraordinarily long entry phase (the decline of Cycle 23) that made it difficult to identify when the actual miminum arrived. In particular, the late 23rd cycle was characterized by diminishing photospheric fields and complex coronal structures that took several extra years to simplify to its traditional dipolar solar minimum state. The nearly dipolar phase, when it arrived, had a duration somewhat shorter than those of the previous cycles. The fact that the corona maintained an appearance more like a solar maximum corona through most of the quiet transitional phase between Cycles 23 and 24 gave the impression of a much more complicated solar minimum solar wind structure in spite of the weaknesses of the mass flux and interplanetary field. The extent to which the Cycle 23-24 transition will affect Cycle 24, and/or represents what happens during weak cycles in general, remains to be seen.

scholarly journals Coronal magnetic fields from the inversion of linear polarization measurements

2009 ◽  
Vol 5 (S264) ◽  
pp. 96-98
Author(s):  
Yu Liu ◽  
Haosheng Lin ◽  
Jeff Kuhn
Keyword(s):  
Linear Polarization ◽  
Spatial Relation ◽  
Coronal Magnetic Field ◽  
Surface Model ◽  
Source Surface ◽  
Coronal Emission ◽  
Field Source ◽  
Close Relationship ◽  
The Difference ◽  
Ir Emission

AbstractReal 3-D coronal magnetic field reconstruction is expected to be made based on the technologies of IR spectrometry and tomography, in which the data from other wavelengths can be used as critical reference. Our recent studies focused on this issue are briefly reviewed in this paper. Liu & Lin (2008) first evaluated the validity of potential field source surface model applied to one of five limb regions in the corona by comparing the theoretical polarization maps with SOLARC observations in the IR Fe XIII 10747 Å forbidden coronal emission line (CEL). The five limb coronal regions were then studied together in order to study the spatial relation between the bright EUV features on the solar disk and the inferred IR emission sources, which were obtained from the inversion of the SOLARC linear polarization (LP) measurements (Liu 2009). The inversion for each fiber data in the field of view was made by finding the best location where the difference between the synthesized and the observed polarizations reaches the minimum in the integration path along the line of sight. We found a close relationship between the inferred IR emission source locations and the EUV strong emission positions.

Three-dimensional reconstruction of an expanding shock associated with a Solar particle event

2021 ◽  
Author(s):  
Federica Frassati ◽  
Monica Laurenza ◽  
Alessandro Bemporad ◽  
Matthew J. West ◽  
Salvatore Mancuso ◽  
...  
Keyword(s):  
Magnetic Field ◽  
3D Reconstruction ◽  
Ultra Violet ◽  
Coronal Magnetic Field ◽  
Release Time ◽  
Shock Acceleration ◽  
Source Surface ◽  
Type Ii ◽  
Field Source ◽  
The Magnetic Field

<p><span>On 2013 June 21st an eruption occurred in the active region NOAA 1177 (14S73E), </span><span>giving rise to</span> <span>a M2.9 class flare starting at 02:30 UT, a fast partial halo coronal mass ejection (CME), and a type II radio burst. The concomitant emission of solar energetic particles (SEPs) produced a significant increase in the proton fluxes measured by LET and HET aboard STEREO-B. By using stereoscopic observations in extreme ultra violet (EUV) and white light (WL) spectral intervals, we performed a 3D reconstruction of the expanding front by processing SDO/AIA, STEREO/EUVI, COR1 and COR2, and SOHO/LASCO data assuming a spheroidal model. By using the 3D reconstruction, we estimated the temporal evolution of θ</span><span><sub>Bn,</sub></span><span> </span><span>i.e.,</span> <span>the angle between the normal to the expanding front and the coronal magnetic field computed by the Potential-Field Source-Surface (PFSS) approximation, within 2.5 R</span><span><sub>ʘ</sub></span><span>. The front </span><span>of the CME</span><span>was found to be quasi-parallel to the magnetic field almost everywhere</span><span><sub>.</sub></span><span> Above 2.5 R</span><span><sub>ʘ</sub></span><span>, where the front was identified as a shock, we projected the 3D expanding surface </span><span>reconstructed for </span><span>different times on the ecliptic plane and</span><span> </span><span>we calculated the θ</span><span><sub>Bn </sub></span><span>between the normal to the front and Parker spiral arms. In this case the shock was almost perpendicular to the magnetic field (quasi-parallel shock). During the expansion the region located between the nose and the eastern flank of the shock was magnetically connected with ST-B in agreement with the significant SEP flux measured on-board this spacecraft.</span> <span>W</span><span>hile</span> <span>the shock was only marginally connected with ST-A and GOES-15. </span><span>T</span><span>he SEP release time was estimated to be 10 minutes after the Type II onset, when the shock front was already above 2.5 R</span><span><sub>ʘ</sub></span><span> with a quasi-parallel configuration. Our results are discussed in the framework of the shock acceleration scenario, even if quasi-parallel shocks are expected to have a reduced acceleration efficiency.</span></p>

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