STUDY OF EXTREME-ULTRAVIOLET EMISSION AND PROPERTIES OF A CORONAL STREAMER FROMPROBA2/SWAP,HINODE/EIS AND MAUNA LOA Mk4 OBSERVATIONS

Abstract

Wide-field extreme-ultraviolet (EUV) telescopes imaging in spectral bands sensitive to 1 MK plasma on the Sun often observe extended, ray-like coronal structures stretching radially from active regions to distances of 1.5-2 R , which represent the EUV counterparts of white-light streamers. To explain this phenomenon, we investigated the properties of a streamer observed on 2010 October 20 and 21, by the PROBA2/SWAP EUV telescope together with the Hinode/EIS (HOP 165) and the Mauna Loa Mk4 white-light coronagraph. In the SWAP 174 Å band comprising the Fe ix-Fe xi lines, the streamer was detected to a distance of 2 R . We assume that the EUV emission is dominated by collisional excitation and resonant scattering of monochromatic radiation coming from the underlying corona. Below 1.2 R , the plasma density and temperature were derived from the Hinode/EIS data by a line-ratio method. Plasma conditions in the streamer and in the background corona above 1.2 R from the disk center were determined by forward-modeling the emission that best fit the observational data in both EUV and white light. It was found that the plasma in the streamer above 1.2 R is nearly isothermal, with a temperature of T = 1.43 ± 0.08 MK. The hydrostatic scale-height temperature determined from the evaluated density distribution was significantly higher (1.72 ± 0.08 MK), which suggests the existence of outward plasma flow along the streamer. We conclude that, inside the streamer, collisional excitation provided more than 90% of the observed EUV emission, whereas, in the background corona, the contribution of resonance scattering became comparable with that of collisions at R 2 R .

Comparison of Magnetohydrodynamics Simulation And Observasional Result to Solar Coronal Helmet Streamer

“…1) [2]. The lower parts (arcade base) are about the scale of active regions or even larger as observed in the green line emitted by FeXIV (λ = 5303A) [3].…”

“…The coronal plasma density distribution is not isotropic as a result of the penetration by the helmet streamer magnetic structure [1,3,4]. Figure 1 is making image of the process white light data with several helmet streamers structure (A and B) [2,3].…”

“…Figure 1 is making image of the process white light data with several helmet streamers structure (A and B) [2,3].…”

“…Study of the helmet streamers formation in the solar corona is very important to have some plausible physical condition prior a launch of energetic solar CMEs since the CMEs mostly emerge from the helmet streamers [3,5]. The idea of research is magnetic fields can induce currents in a moving conductive fluid, which create forces on the fluid.…”

“…The idea of research is magnetic fields can induce currents in a moving conductive fluid, which create forces on the fluid. The set of equations which describe this condition are combination of the NavierStokes equations of fluid dynamics and Maxwell's equations of electromagnetism [3,6,7]. Magnetohydrodynamics equation was used in reference to the transfer of momentum from the Sun to the planets, but it's eventually expanded upon to include the current field.…”