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On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode  

John Mariska   Submitted: 2012-11-20 09:27

Since its launch on 22 September 2006, the EUV Imaging Spectrometer onboard the Hinode satellite has exhibited a gradual decay in sensitivity. Using spectroheliograms taken in the Fe VIII 185.21 Angstrom and Si VII 275.35 Angstrom emission lines in quiet regions near Sun center we characterize that decay. For the period from December 2006 to March 2012, the decline in the sensitivity can be characterized as an exponential decay with an average time constant of 7358 ? 1030 days (20.2 ? 2.8 years). Emission lines formed at temperatures >106.1 K in the quiet-Sun data exhibit solar-cycle effects.

Authors: J. T. Mariska
Projects: Hinode/EIS

Publication Status: Solar Physics, in press
Last Modified: 2012-11-20 20:24
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Doppler Shift, Intensity, and Density Oscillations Observed with the EUV Imaging Spectrometer on Hinode  

John Mariska   Submitted: 2010-03-02 08:15

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 2 km s-1 in emission lines ranging from Fe XI 188.23 Angstroms, which is formed at log T = 6.07 to Fe XV 284.16 Angstroms, which is formed at log T = 6.32. Typical periods are near 10 minutes. 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.

Authors: Mariska, John T. and Muglach, K.
Projects: Hinode/EIS

Publication Status: ApJ (in press)
Last Modified: 2010-03-02 09:25
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John Mariska   Submitted: 2008-06-03 04:55

Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory and with the Bragg Crystal Spectrometer on Yohkoh. This Letter reports the detection of low-amplitude damped oscillations in coronal emission lines formed at much lower temperatures observed with the EUV Imaging Spectrometer on the Hinode satellite. The oscillations have an amplitude of about 2 km s-1, and a period of around 35 min. The decay times show some evidence for a temperature dependence with the lowest temperature of formation emission line (Fe XII 195.12 Angstroms) exhibiting a decay time of about 43 min, while the highest temperature of formation emission line (Fe XV 284.16 Angstroms) shows no evidence for decay over more than two periods of the oscillation. The data appear to be consistent with slow magnetoacoustic standing waves, but may be inconsistent with conductive damping.

Authors: Mariska, J.T., Warren, H.P., Williams, D.R., Watanabe, T.
Projects: Hinode/EIS

Publication Status: ApJ Letters in press
Last Modified: 2008-09-23 21:01
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Subject will be restored when possible  

John Mariska   Submitted: 2007-09-28 06:58

The EUV Imaging Spectrometer (EIS) on the Hinode satellite is capable of measuring emission line center positions for Gaussian line profiles to a fraction of a spectral pixel, resulting in relative solar Doppler-shift measurements with an accuracy of a less than a km s-1 for strong lines. We show an example of the application of that capability to an active region sit-and-stare observation in which the EIS slit is placed at one location on the Sun and many exposures are taken while the spacecraft tracking keeps the same solar location within the slit. For the active region examined (NOAA 10930), we find that significant intensity and Doppler-shift fluctuations as a function of time are present at a number of locations. These fluctuations appear to be similar to those observed in high-temperature emission lines with other space-borne spectroscopic instruments. With its increased sensitivity over earlier spectrometers and its ability to image many emission lines simultaneously, EIS should provide significant new constraints on Doppler-shift oscillations in the corona.

Authors: John T. Mariska, Harry P. Warren, Ignacio Ugarte-Urra, David H. Brooks, David R. Williams, and Hirohisa Hara
Projects: Hinode

Publication Status: PASJ special Hionde issue in press
Last Modified: 2007-09-29 21:41
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Characteristics of Solar Flare Doppler Shift Oscillations Observed with the Bragg Crystal Spectrometer on Yohkoh  

John Mariska   Submitted: 2005-11-03 07:01

This paper reports the results of a survey of Doppler shift oscillations measured during solar flares in emission lines of S XV and Ca XIX with the Bragg Crystal Spectrometer (BCS) on Yohkoh. Data from 20 flares that show oscillatory behavior in the measured Doppler shifts have been fitted to determine the properties of the oscillations. Results from both BCS channels show average oscillation periods of 5.5 ± 2.7 minutes, decay times of 5.0 ± 2.5 minutes, amplitudes of 17.1 ± 17.0 km/ s, and inferred displacements of 1070 ± 1710 km, where the listed errors are the standard deviations of the sample means. For some of the flares, intensity fluctuations are also observed. These lag the Doppler shift oscillations by 1/4 period, strongly suggesting that the oscillations are standing slow mode waves. The relationship between the oscillation period and the decay time is consistent with conductive damping of the oscillations.

Authors: Mariska, J. T.
Projects: Yohkoh-BCS

Publication Status: ApJ in press
Last Modified: 2005-11-03 07:01
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Observations of Solar Flare Doppler Shift Oscillations with the Bragg Crystal Spectrometer on Yohkoh  

John Mariska   Submitted: 2005-01-07 05:50

Oscillations in solar coronal loops appear to be a common phenomenon. Transverse and longitudinal oscillations have been observed with both the Transition Region and Coronal Explorer and Extreme Ultraviolet Imaging Telescope imaging experiments. Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation Spectrometer. These observations provide valuable diagnostic information on coronal conditions and may help refine our understanding of coronal heating mechanisms. I have initiated a study of the time dependence of Doppler shifts measured during flares with the Bragg Crystal Spectrometer (BCS) on Yohkoh. This Letter reports the detection of oscillatory behavior in Doppler shifts measured as a function of time in the emission lines of S XV and Ca XIX. For some flares, both lines exhibit damped Doppler shift oscillations with amplitudes of a few km s-1 and periods and decay times of a few minutes. The observations appear to be consistent with transverse oscillations. Because the BCS observed continuously for almost an entire solar cycle, it provides numerous flare data sets, which should permit an excellent characterization of the average properties of the oscillations.

Authors: Mariska, J. T.
Projects: Yohkoh-BCS

Publication Status: ApJ Letters in press
Last Modified: 2005-01-07 05:50
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Abstracts by Author
On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode
Doppler Shift, Intensity, and Density Oscillations Observed with the EUV Imaging Spectrometer on Hinode
Subject will be restored when possible
Subject will be restored when possible
Characteristics of Solar Flare Doppler Shift Oscillations Observed with the Bragg Crystal Spectrometer on Yohkoh
Observations of Solar Flare Doppler Shift Oscillations with the Bragg Crystal Spectrometer on Yohkoh

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