Geocoronal hydrogen studies using Fabry–Perot interferometers, part 1: Instrumentation, observations, and analysis

Mierkiewicz, E. J.; Roesler, F. L.; Nossal, S. M.; Reynolds, R. J.

doi:10.1016/j.jastp.2005.08.024

Cited by 32 publications

(99 citation statements)

References 61 publications

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“…The Arequipa nightglow images are analyzed using the method of annular summing spectroscopy described by Coakley et al (1996), Mierkiewicz et al (2006), andNossal et al (2006). By imaging the FPI circular interference pattern onto the face of the thermo-electrically cooled bare CCD chip (high quantum efficiency) and then integrating the nightglow images around the center of this pattern to convert the image into a spectrum, the ratio of signal to noise is much improved.…”

Section: Data Analysis: Determination Of the Spectrummentioning

confidence: 99%

New results on equatorial thermospheric winds and the midnight temperature maximum

et al. 2008

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Abstract. Optical observations of thermospheric winds and temperatures determined with high resolution measurements of Doppler shifts and Doppler widths of the OI 630-nm equatorial nightglow emission have been made with improved accuracy at Arequipa, Peru (16.4 • S, 71.4 • W) with an imaging Fabry-Perot interferometer. An observing procedure previously used at Arecibo Observatory was applied to achieve increased spatial and temporal sampling of the thermospheric wind and temperature with the selection of eight azimuthal directions, equally spaced from 0 to 360 • , at a zenith angle of 60 • . By assuming the equivalence of longitude and local time, the data obtained using this technique is analyzed to determine the mean neutral wind speeds and mean horizontal gradients of the wind field in the zonal and meridional directions. The new temperature measurements obtained with the improved instrumental accuracy clearly show the midnight temperature maximum (MTM) peak with amplitudes of 25 to 200 K in all directions observed for most nights. The horizontal wind field maps calculated from the mean winds and gradients show the MTM peak is always preceded by an equatorward wind surge lasting 1-2 h. The results also show for winter events a meridional wind abatement seen after the MTM peak. On one occasion, near the September equinox, a reversal was observed during the poleward transit of the MTM over Arequipa. Analysis inferring vertical winds from the observed convergence yielded inconsistent results, calling into question the validity of this calculation for the MTM structure at equatorial latitudes during solar minimum. Comparison of the observations with the predictions of the NCAR general circulation model indicates that the model fails to reproduce the observed amplitude by a factor of 5 or more. This is attributed in part to the lack of adequate spatial resolution in the model as the MTM phenomenon takes place within a scale of 300-500 km and ∼45 min in local time.Correspondence to: J. Meriwether (john.meriwether@ces.clemson.edu)The model shortcoming is also attributed in part to the need for the model to include a hydrodynamical mechanism to describe the merging of the zonal wind with the meridional tidal winds that converge onto the geographical equator. Finally, a conclusion of this work is that the MTM compressional heating takes place along the perimeter of the pressure bulge rather than within the bulge, an issue previously not appreciated.

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Section: Data Analysis: Determination Of the Spectrummentioning

confidence: 99%

New results on equatorial thermospheric winds and the midnight temperature maximum

et al. 2008

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“…Since Fabry-Pérot spectrometers offer the advantage of simultaneously achieving high throughput and high spectral resolution, they are used to obtain high-resolution spectra of very faint, extended diffuse emission line objects of the ISM such as H II regions and PNe (Roesler 1974;Tufte 1997;Mierkiewicz et al 2006 spectral resolution (Sahan et al 2005(Sahan et al , 2007. After completing test observations in the zenith direction, the spectrometer was supported by TUBITAK (The Scientific and Technical Research Council of Turkey) with grant number 104T252 to explore ionized gas in ISM with a spatial resolution of 4 .…”

Section: Defpos Spectrometermentioning

confidence: 99%

“…1999; Mierkiewicz et al 2006). The post-étalon (or the exit) optics including a combination of two lenses with an effective focal length of ≈17 cm, were used to image the Fabry-Pérot s annular interference pattern onto 1.0 cm 2 region the CCD, which can record many spectral elements simultaneously.…”

Section: Defpos Spectrometermentioning

confidence: 99%

“…Light is collected simultaneously in all spectral elements. Annular summing spectroscopy makes use of the property of the FabryPerot interference pattern that equal area annuli correspond to equal spectral intervals (Reynolds et al 1990;Coakley et al 1996;Nossal et al 1998;Mierkiewicz et al 2006). Using this technique whereby the pixel intensities are integrated within concentric equal area annuli, the reduced CCD image of the Fabry-Pérot interference pattern is converted to a spectral profile.…”

Section: Defpos Spectrometermentioning

confidence: 99%

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Hα observations with DEFPOS

Şahan

2011

Astron Nachr

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A 7.5 cm, dual étalon Fabry‐Pérot spectrometer called DEFPOS has been set up at Coudé focus of 150 cm RTT150 telescope at TUBITAK National Observatory (TUG, Antalya, Turkey) to investigate the physical properties of Diffuse Ionized Gas (DIG) in our Galaxy. The spectrometer, having a 4 arcmin circular field of view over a 200 km s–1 (4.4 Å) spectral window near Hα, has been used to observe H II regions and Planetary Nebulae (PNe) since May 2007 (Sahan et al. 2009). Early observations have been analyzed and physical and kinematic properties such as the intensity, the line width, and the LSR velocity are presented here. These values are compared with earlier results from different studies. In this study, I discuss some results obtained by DEFPOS, including two H II regions (Sh2‐156, Sh2‐157), and two PNe (NGC 1360, and NGC 6826). The Intensities, the radial velocities and the line widths of the Hα emission line vary from 101.4R to 149.97R (1 Rayleigh =106/4π photons cm–2 sr–1 s–1 = 2.41 × 10–7 erg cm–2 s–1 sr–1 at Hα), –41.19 km s–1 to +8.34 km s–1, and 39.55 km s–1 to 58.23 km s–1, respectively (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…The Balmer α line of hydrogen differs in wavelength from the Balmer α line of deuterium by 82 km s −1 (1.78 Å) [10,11,24]. The purpose of this method is to be able to determine the wavelength interval that corresponds to an annular area on the chip.…”

Section: Intensity Calibrationmentioning

confidence: 99%

Intensity calibration of DEFPOS data

2009

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In this study, details of the intensity calibration of Dual Etalon Fabry-Perot Optical Spectrometer (DEFPOS) were described. At TUBITAK National Observatory (TUG), The DEFPOS was redesigned so as to observe galactic Hα emission line from the diffuse ionized gas with 4 field of view (FOV) and then was located at the coudé exit of the 150 cm RTT150 telescope (Şahan et al., Research in Astronomy and Astrophysics (RAA) 9(2), 2009). The Absolute intensity calibration of the spectrometer was made by utilizing the data obtained from nine selected regions of NGC 7000 nebula. These regions were selected within 49 FOV whose intensity calibration was determined to be 850 ± 50 R by Scherb (Astrophys J 243:644-650, 1981). One of these regions was specially selected because of its intensity for the 4 FOV was estimated as 900 R by Morgenthaler et al. (Astrophys J 563(1):451-461, 2001). For calibration of the DEFPOS data, the intensity values from Ishida and Kawajiri (PASJ 20:95-121, 1968) and the VTSS Hα maps were used and it was found that 1 ADU km s −1 equals 2337.4 R for a 1200 s exposure time. The radial velocities and the line widths from these regions were also determineḋ I. Yeǧingil is on leave of absence from Cukurova University.N. and compared with the previous results. These calibrations have been in close agreement.

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Geocoronal hydrogen studies using Fabry–Perot interferometers, part 1: Instrumentation, observations, and analysis

Cited by 32 publications

References 61 publications

New results on equatorial thermospheric winds and the midnight temperature maximum

New results on equatorial thermospheric winds and the midnight temperature maximum

Hα observations with DEFPOS

Intensity calibration of DEFPOS data

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