Young P.R.,George Mason University |
Muglach K.,NASA |
Muglach K.,ARTEP Inc
Solar Physics | Year: 2014
A blowout jet occurred within the south coronal hole on 9 February 2011 at 09:00 UT and was observed by the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory, and by the EUV Imaging Spectrometer (EIS) and X-Ray Telescope (XRT) onboard the Hinode spacecraft during coronal-hole monitoring performed as part of Hinode Operations Program No. 177. Images from AIA show expanding hot and cold loops from a small bright point with plasma ejected in a curtain up to 30 Mm wide. The initial intensity front of the jet had a projected velocity of 200 km s-1, and the line-of-sight (LOS) velocities measured by EIS are between 100 and 250 km s-1. The LOS velocities increased along the jet, implying that an acceleration mechanism operates within the body of the jet. The jet plasma had a density of 2.7×108 cm-3 and a temperature of 1.4 MK. During the event a number of bright kernels were seen at the base of the bright point. The kernels have sizes of ≈ 1000 km, are variable in brightness, and have lifetimes of 1 - 15 minutes. An XRT filter ratio yields temperatures of 1.5 - 3.0 MK for the kernels. The bright point existed for at least ten hours, but disappeared within two hours after the jet, which lasted for 30 minutes. HMI data reveal converging photospheric flows at the location of the bright point, and the mixed-polarity magnetic flux canceled over a period of four hours on either side of the jet. © 2014 Springer Science+Business Media Dordrecht.
Mariska J.T.,U.S. Navy |
Muglach K.,U.S. Navy |
Muglach K.,ARTEP Inc
Astrophysical Journal | Year: 2010
Low-amplitude Doppler-shift oscillations have been observed in coronal emission lines in a number of active regions with the EUV Imaging Spectrometer (EIS) on the Hinode satellite. Both standing and propagating waves have been detected and many periods have been observed, but a clear picture of all the wave modes that might be associated with active regions has not yet emerged. In this study, we examine additional observations obtained with EIS in plage near an active region on 2007 August 22-23. We find Doppler-shift oscillations with amplitudes between 1 and 2kms-1 in emission lines ranging from Fe XI 188.23 , Å which is formed at log T = 6.07, to Fe XV 284.16 , which is formed at log T = 6.32. Typical periods are near 10minutes. We also observe intensity and density oscillations for some of the detected Doppler-shift oscillations. In the better-observed cases, the oscillations are consistent with upwardly propagating slow magnetoacoustic waves. Simultaneous observations of the Ca II H line with the Hinode Solar Optical Telescope Broadband Filter Imager show some evidence for 10 minute oscillations as well. © 2010 The American Astronomical Society. All rights reserved.
Wang Y.-M.,U.S. Navy |
Muglach K.,NASA |
Muglach K.,ARTEP Inc
Astrophysical Journal | Year: 2013
Filament channels coincide with large-scale polarity inversion lines of the photospheric magnetic field, where flux cancellation continually takes place. High-cadence Solar Dynamics Observatory (SDO) images recorded in He ii 30.4 nm and Fe ix 17.1 nm during 2010 August 22 reveal numerous transient brightenings occurring along the edge of a filament channel within a decaying active region, where SDO line-of-sight magnetograms show strong opposite-polarity flux in close contact. The brightenings are elongated along the direction of the filament channel, with linear extents of several arcseconds, and typically last a few minutes; they sometimes have the form of multiple two-sided ejections with speeds on the order of 100 km s-1. Remarkably, some of the brightenings rapidly develop into larger scale events, forming sheetlike structures that are eventually torn apart by the diverging flows in the filament channel and ejected in opposite directions. We interpret the brightenings as resulting from reconnections among filament-channel field lines having one footpoint located in the region of canceling flux. In some cases, the flow patterns that develop in the channel may bring successive horizontal loops together and cause a cascade to larger scales. © 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
Busquet M.,ARTEP Inc
Optics Communications | Year: 2014
In this comment, we discuss the possibility of imaging the radiative precursor of a strong shock with a 21.2 nm soft x-ray laser probe and we analyze the data presented in C.Stehlé et al "New probing techniques of radiative shocks", (Optics Communications 285, 64, 2012) in order to derive some estimation of the achieved resolution. We show that the presented results are inconclusive for the existence of a radiative precursor. Furthermore, our best estimation of cold and warm Xenon VUV opacities tells that 21.2 nm backlighting would not be able to probe this radiative precursor. © 2012 Elsevier B.V.
Feldman U.,ARTEP Inc
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2016
CHIANTI is an atomic database with software for calculating emission properties. It is extensively used in deriving the atomic properties of spectra recorded from astrophysical and low density laboratory plasmas. In order to obtain an insight into the accuracy of the CHIANTI calculated level populations, a consistency check was conducted along the He i, Be i, B i, C i, N i, and O i isoelectronic sequences. In the evaluation process, levels of the ground configuration and the first and second excited configurations were considered. These are the levels responsible for most of the spectral lines used when deriving the plasma properties of astrophysical objects. As is documented below, the accuracy of the CHIANTI level population calculations depends on the particular ion, level and on the electron density. Under some conditions the calculations appear quite robust while in others they are not. © 2016 IOP Publishing Ltd.