نتایج جستجو برای: sun corona

تعداد نتایج: 47564  

2008
V. Delouille P. Chainais J. - F. Hochedez

Future missions such as Solar Orbiter (SO), InterHelioprobe, or Solar Probe aim at approaching the Sun closer than ever before, with on board some high resolution imagers (HRI) having a subsecond cadence and a pixel area of about (80km) 2 at the Sun during perihelion. In order to guarantee their scientific success, it is necessary to evaluate if the photon counts available at these resolution a...

2017
Takashi SAKURAI

The solar corona is a tenuous outer atmosphere of the Sun. Its million-degree temperature was discovered spectroscopically in the 1940s, but its origin has been debated since then without complete convergence. Currently there are two classes of models; the wave theory and the microflare/nanoflare theory. Both models have merits and disadvantages, but the essential issues are nearly pinned down....

2009
A. R. Yeates D. H. Mackay

Loss of equilibrium of magnetic flux ropes is a leading candidate for the origin of solar coronal mass ejections (CMEs). The aim of this paper is to explore to what extent this mechanism can account for the initiation of CMEs in the global context. A simplified MHD model for the global coronal magnetic field evolution in response to flux emergence and shearing by large-scale surface motions is ...

2007
S. Krucker A.O.. Benz

We present sensitive coronal line (Fe IX and Fe XII) observations by the Extreme ultraviolet Imaging Telescope (EIT) onboard the SOHO satellite. The thermal emission of the quiet corona is detected to uctuate in time and space, presumably the result of localized heat inputs. Signiicant uctuations are found in 85% of all pixels. The more prominent enhancements are identiied with previously repor...

2008
I. G. Hannah

We present the first results using the Reuven Ramaty High-Energy Solar Spectroscopic Imager, RHESSI, to observe solar X-ray emission not associated with active regions, sunspots or flares (the quiet Sun). Using a newly developed chopping technique (fan-beam modulation) during seven periods of offpointing between June 2005 to October 2006, we obtained upper limits over 3-200 keV for the quietest...

Journal: :Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 2012
Vasilis Archontis

We present a review of the process of magnetic flux emergence in the Sun. We focus on observations and numerical experiments that explore the dynamical rise of magnetic fields from the solar interior to the corona. We describe the response of the highly stratified solar atmosphere on flux emergence and, consequently, we present a comprehensive picture of the coupling between solar dynamic event...

1997
Daniel Wang

I characterize the global distribution of the 3/4 keV band background with a simple model of the hot Galactic corona, plus an isotropic extragalactic background. The corona is assumed to be approximately polytropic (index = 5/3) and hydrostatic in the gravitational potential of the Galaxy. The model accounts for X-ray absorption, and is constrained iteratively with the ROSAT all-sky X-ray surve...

2002
Takeru Ken Suzuki

We investigate possibilities of solar coronal heating by acoustic waves generated not at the photosphere but in the corona, aiming at heating in the midto low-latitude corona where the low-speed wind is expected to come from. Acoustic waves of period τ ∼ 100s are triggered by chromospheric reconnection, one model of small scale magnetic reconnection events recently proposed by Sturrock. These w...

2007
STEVEN R. CRANMER

In this paper the dissipation of ion cyclotron resonant waves in the extended solar corona is Alfve n examined in detail. For the Ðrst time, the wave damping arising from more than 2000 low-abundance ion species is taken into account. Useful approximations for the computation of coronal ionization equilibria for elements heavier than nickel are presented. Also, the Sobolev approximation from t...

2007
Andrea Verdini

We solve the problem of propagation and dissipation of Alfvénic turbulence in a model solar atmosphere consisting of a static photosphere and chromosphere, transition region, and open corona and solar wind, using a phenomenological model for the turbulent dissipation based on wave reflection. We show that most of the dissipation for a given wave-frequency spectrum occurs in the lower corona, an...

نمودار تعداد نتایج جستجو در هر سال

با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید