Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

EIT waves and coronal magnetic field diagnosis

19.11.2009
Department of Astronomy, Nanjing University in Nanjing, China – Solar coronal seismology based on magnetic field-line stretching model of "EIT waves" is proposed, which is demonstrated to be potentially able to probe the mysterious magnetic field in the solar corona.

The study, which was led by Dr. Chen, is reported in Issue 52 of Science in China (G) because of its significant research value.

Many explosive phenomena on the Sun, such as solar flares, involve the energy conversion from the magnetic energy to thermal and kinetic energies in the corona, which is the outer atmosphere of the Sun. Therefore, the coronal magnetic field is extremely crucial in the understanding of these eruptive phenomena.

However, at present, only the magnetic field along the solar surface can be measured directly, whereas the magnetic field in the solar corona can hardly be measured. Despite some efforts of measuring through infrared spectral lines and of the inversion through radio emissions, the coronal magnetic field is generally approximated by extrapolating the magnetic field from the solar surface, which is however an ill-posed problem. Therefore, it would be great to have an alternative approach to diagnose the coronal magnetic field.

In 1997, the EUV Imaging Telescope (EIT in short) on board the European–US satellite, Solar and Heliospheric Observatory (SOHO), discovered an unexpected wavelike phenomenon propagating in the solar corona, which was later named "EIT waves" after the telescope. "EIT waves" were explained successfully to be apparently propagating density enhancements compressed by the successive stretching of magnetic field lines during coronal mass ejections (CMEs), the largest-scale eruptive phenomenon on the Sun.

According to this model, the "EIT waves" propagation velocity is intimately determined by the 3-dimensional distribution of the coronal magnetic field. Based on such an interesting property, Dr. Chen proposed recently that the profile of the "EIT wave" propagation velocity can be utilized to probe the coronal magnetic field.

Dr. Chen told the reporter: "You know, we can already diagnose the deep structure of the Earth by analyzing seismic waves. Similarly, we now can diagnose the magnetic field in the solar corona by analyzing EIT waves, which in some sense can be analogized as helioseismic waves." He commented that, in this sense, "EIT wave" observations open a new window for solar physicists to look into the mysterious magnetic field in the solar corona, and would help uncover the explosive nature of many explosive phenomena, including solar flares. As also commented by a reviewer, "This is an interesting paper describing the observations and modeling of EIT waves, and illustrating how they can be applied to probe the global magnetic field in the corona".

"EIT waves" were originally explained as the magnetoacoustic waves, i.e., sound waves coupled with the magnetic field. Such a model was also used to estimate the magnetic field in the low corona. However, the magnetoacoustic wave model cannot account for various characteristics of "EIT waves". To reconcile the discrepancies, Dr. Chen and his collaborators from China, USA, and Japan put forward the magnetic field-line stretching model since 2002, which has been widely recognized in the solar physics community. In this newly published paper, Dr. Chen demonstrated that it is feasible to diagnose the magnetic field in the solar corona using the observations of "EIT wave" velocity profiles.

With the application of the "EIT wave" diagnostics, the 3-dimensional distribution of the solar coronal magnetic field is expected to be revealed, which would finally help unveil the nature of solar flares and CMEs, the two major driving sources of hazardous space disturbances to human high-tech activities, including navigations, telecommunications, manned missions, etc.

Dr. P. F. Chen is working in Department of Astronomy, Nanjing University. The department is one of the lead groups of astronomy research in China. The research was sponsored by National Natural Science Foundation of China (Nos. 10403003 and 10673004) and the Key Project of Chinese National Programs for Fundamental Research and Development (2006CB806302).

References:

1. Chen P F. EIT waves and coronal magnetic field diagnosis. Sci China G-Phys Mech Astron, 2009, 52(11): 1785-1789

http://springer.r.delivery.net/r/r?2.1.Ee.2Tp.1hW1Qv.ByxLWW..H.Ixxu.3Geu.bW89MQ%5f%5fDUSeFVZ0

2. Chen P F, Wu S T, Shibata K and Fang C. Evidence of EIT and Moreton waves in numerical simulations. Astrophys J, 2002, 572: L99-L102

http://www.iop.org/EJ/abstract/1538-4357/572/1/L99/

3 Chen P F, Fang C and Shibata K. A full view of EIT waves. Astrophys J, 2005, 622: 1202-1210

http://www.iop.org/EJ/abstract/0004-637X/622/2/1202/

P. F. Chen | EurekAlert!
Further information:
http://www.nju.edu.cn

More articles from Physics and Astronomy:

nachricht Witnessing turbulent motion in the atmosphere of a distant star
23.08.2017 | Max-Planck-Institut für Radioastronomie

nachricht Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Optimizing therapy planning for cancers of the liver

24.08.2017 | Medical Engineering

Icebergs: Mathematical model calculates the collapse of shelf ice

24.08.2017 | Earth Sciences

Improved monitoring of coral reefs with the HyperDiver

24.08.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>