Qiang Hu
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Qiang Hu has a total of 7 co-authors. Here are the top co-authors by number of shared publications:
B. Dasgupta
Institute of Geophysics and Planetary Physics University of California 92521 Riverside CA
2 shared publicationsBrahmananda Dasgupta
University of California
2 shared publicationsCharles W. Smith
Institute of Earth, Oceans and Space University of New Hampshire Durham New Hampshire USA
2 shared publicationsNorman F. Ness
Bartol Research Institute University of Delaware Newark Delaware USA
2 shared publicationsRuth M. Skoug
Los Alamos National Laboratory Los Alamos New Mexico USA
2 shared publicationsD. P. Choudhary
Department of Physics and Astronomy California State University 91330 Northridge CA
1 shared publication
Latest Publications
- 1 December 2007
- Published by Springer Nature in Solar Physics
- Vol. 247 (1) , 87-101
An Improved Approach to Non-Force-Free Coronal Magnetic Field Extrapolation
- 1 December 2007
- Published by Springer Nature in Solar Physics
- Vol. 247 (1) , 87-101
An Improved Approach to Non-Force-Free Coronal Magnetic Field Extrapolation
- Open Access
A Practical Approach to Coronal Magnetic Field Extrapolation Based on the Principle of Minimum Dissipation Rate
We present a newly developed approach to solar coronal magnetic field extrapolation from vector magnetograms, based on the Principle of Minimum Dissipation Rate (MDR). The MDR system was derived from a variational problem that is more suitable for an open and externally driven system, like the solar corona. The resulting magnetic field equation is more general than force-free. Its solution can be expressed as the superposition of two linear (constant-$\alpha$) force-free fields (LFFFs) with distinct $\alpha$ parameters, and one potential field. Thus the original extrapolation problem is decomposed into three LFFF extrapolations, utilizing boundary data. The full MDR-based approach requires two layers of vector magnetograph measurements on solar surface, while a slightly modified practical approach only requires one. We test both approaches against 3D MHD simulation data in a finite volume. Both yield quantitatively good results. The errors in the magnetic energy estimate are within a few percents. In particular, the main features of relatively strong perpendicular current density structures, representative of the non-force freeness of the solution, are well recovered.Open AccessA Practical Approach to Coronal Magnetic Field Extrapolation Based on the Principle of Minimum Dissipation Rate
We present a newly developed approach to solar coronal magnetic field extrapolation from vector magnetograms, based on the Principle of Minimum Dissipation Rate (MDR). The MDR system was derived from a variational problem that is more suitable for an open and externally driven system, like the solar corona. The resulting magnetic field equation is more general than force-free. Its solution can be expressed as the superposition of two linear (constant-$\alpha$) force-free fields (LFFFs) with distinct $\alpha$ parameters, and one potential field. Thus the original extrapolation problem is decomposed into three LFFF extrapolations, utilizing boundary data. The full MDR-based approach requires two layers of vector magnetograph measurements on solar surface, while a slightly modified practical approach only requires one. We test both approaches against 3D MHD simulation data in a finite volume. Both yield quantitatively good results. The errors in the magnetic energy estimate are within a few percents. In particular, the main features of relatively strong perpendicular current density structures, representative of the non-force freeness of the solution, are well recovered. - 5 August 2006
- Published by American Geophysical Union (AGU) in Geophysical Research Letters
- Vol. 33 (15)
A new approach to modeling non‐force free coronal magnetic field
We propose a new approach to deriving the local three‐dimensional (3D) non‐force free coronal magnetic field structure from photospheric vector magnetograph measurements. Based on the Principle of Minimum Dissipation Rate, a general non‐force free magnetic field can be expressed as the superposition of two linear (constant‐α) force free field. The parameter, α, for each of the two linear force free field, can be determined by optimizing the requirement that the recovered transverse magnetic field components as the superposition of the corresponding components of the two linear force free field agree with the observed ones at the photospheric level. A preliminary test case study of an analytic non‐force free field model is presented to illustrate the method. We discuss the difficulties associated with the linear force free field extrapolation and the feasibility of our method.
- 5 August 2006
- Published by American Geophysical Union (AGU) in Geophysical Research Letters
- Vol. 33 (15)
A new approach to modeling non‐force free coronal magnetic field
We propose a new approach to deriving the local three‐dimensional (3D) non‐force free coronal magnetic field structure from photospheric vector magnetograph measurements. Based on the Principle of Minimum Dissipation Rate, a general non‐force free magnetic field can be expressed as the superposition of two linear (constant‐α) force free field. The parameter, α, for each of the two linear force free field, can be determined by optimizing the requirement that the recovered transverse magnetic field components as the superposition of the corresponding components of the two linear force free field agree with the observed ones at the photospheric level. A preliminary test case study of an analytic non‐force free field model is presented to illustrate the method. We discuss the difficulties associated with the linear force free field extrapolation and the feasibility of our method.
- 25 August 2005
- Published by American Geophysical Union (AGU) in Journal of Geophysical Research
- Vol. 110 (A9)
On the magnetic topology of October/November 2003 events
We examine the topology of several magnetic ejecta events during October–November 2003. The Grad‐Shafranov reconstruction results from ACE magnetic and plasma data show magnetic flux rope configurations. Some are large scale, with sizes of tenths of an AU, typical of magnetic clouds. Some are of sizes hundredths of an AU. Their characteristic parameters are reported. Magnetic field data from Wind spacecraft are utilized to compare the prediction from numerical modeling with the actual measurement. Poor to good agreement is achieved. The deviations are discussed, particularly in the context of extremely high‐speed solar wind flows.
- 25 August 2005
- Published by American Geophysical Union (AGU) in Journal of Geophysical Research
- Vol. 110 (A9)
On the magnetic topology of October/November 2003 events
We examine the topology of several magnetic ejecta events during October–November 2003. The Grad‐Shafranov reconstruction results from ACE magnetic and plasma data show magnetic flux rope configurations. Some are large scale, with sizes of tenths of an AU, typical of magnetic clouds. Some are of sizes hundredths of an AU. Their characteristic parameters are reported. Magnetic field data from Wind spacecraft are utilized to compare the prediction from numerical modeling with the actual measurement. Poor to good agreement is achieved. The deviations are discussed, particularly in the context of extremely high‐speed solar wind flows.
- 28 June 2005
- Published by American Geophysical Union (AGU) in Geophysical Research Letters
- Vol. 32 (12)
Calculation of magnetic helicity of cylindrical flux rope
We examine a method of calculating the magnetic helicity of cylindrical magnetic flux rope of arbitrary cross section from in‐situ spacecraft data. First we examine the gauge invariance of the definition of relative helicity by Finn and Antonsen (1985). Two approaches based on Grad‐Shafranov equation are then described. A case study is presented to illustrate the method. The results show significant discrepancies from an earlier study utilizing axially symmetric models. We briefly discuss the potential applications for Sun‐Earth connection.
- 28 June 2005
- Published by American Geophysical Union (AGU) in Geophysical Research Letters
- Vol. 32 (12)
Calculation of magnetic helicity of cylindrical flux rope
We examine a method of calculating the magnetic helicity of cylindrical magnetic flux rope of arbitrary cross section from in‐situ spacecraft data. First we examine the gauge invariance of the definition of relative helicity by Finn and Antonsen (1985). Two approaches based on Grad‐Shafranov equation are then described. A case study is presented to illustrate the method. The results show significant discrepancies from an earlier study utilizing axially symmetric models. We briefly discuss the potential applications for Sun‐Earth connection.
- 3 March 2004
- Published by American Geophysical Union (AGU) in Journal of Geophysical Research
- Vol. 109 (A3)
Multiple flux rope magnetic ejecta in the solar wind
Four magnetic flux rope events observed by Advanced Composition Explorer (ACE) in the solar wind at 1 AU are examined by the Grad‐Shafranov reconstruction technique. Their 2D cross sections obtained from magnetic field and plasma measurements show configurations of multiple, nonsymmetric, cylindrical flux ropes embedded within their boundaries. Each boundary is defined in consistency with two‐dimensional magnetohydrostatic theory. Among the four events, three have double flux rope configurations, and the fourth is a triplet. Parameters characterizing the events are derived. The orientation of cylindrical axis is obtained, and associated uncertainty is estimated. All events have unidirectional axial magnetic field and axial currents. The total axial magnetic flux is of the order ∼1012 Wb, and the total axial current is of the order ∼108 A. Each flux rope in the doubled flux rope pair and the triplet has the same chirality as its partner(s). Magnetic X points are formed between adjacent flux ropes on the plane perpendicular to the cylindrical axis. One event with abrupt change in magnetic field direction and another related to energetic particles are discussed.
- 3 March 2004
- Published by American Geophysical Union (AGU) in Journal of Geophysical Research
- Vol. 109 (A3)
Multiple flux rope magnetic ejecta in the solar wind
Four magnetic flux rope events observed by Advanced Composition Explorer (ACE) in the solar wind at 1 AU are examined by the Grad‐Shafranov reconstruction technique. Their 2D cross sections obtained from magnetic field and plasma measurements show configurations of multiple, nonsymmetric, cylindrical flux ropes embedded within their boundaries. Each boundary is defined in consistency with two‐dimensional magnetohydrostatic theory. Among the four events, three have double flux rope configurations, and the fourth is a triplet. Parameters characterizing the events are derived. The orientation of cylindrical axis is obtained, and associated uncertainty is estimated. All events have unidirectional axial magnetic field and axial currents. The total axial magnetic flux is of the order ∼1012 Wb, and the total axial current is of the order ∼108 A. Each flux rope in the doubled flux rope pair and the triplet has the same chirality as its partner(s). Magnetic X points are formed between adjacent flux ropes on the plane perpendicular to the cylindrical axis. One event with abrupt change in magnetic field direction and another related to energetic particles are discussed.