Periodic variations of geocoronal Balmer‐alpha brightness due to solar‐driven exospheric abundance variations

Kerr, Robert B.; García, R.; He, X.; Noto, J.; Lancaster, Redgie S.; Tepley, C. A.; González, S. A.; Friedman, J. S.; Doe, R. A.; Lappen, M.; McCormack, B. M.

doi:10.1029/1999ja900186

Cited by 23 publications

(24 citation statements)

References 37 publications

(42 reference statements)

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“…The intensity observed in Wisconsin was about 50% higher at solar maximum than at solar minimum for a shadow altitude of 3000 km during solar cycles 22 and 23. However, opposite results were found for an observation at Arecibo, Puerto Rico, in 1983; the Balmer-a intensity was about 50% higher during the solar minimum than during the solar maximum for a shadow altitude less than ∼2000 km [Kerr et al, 2001].…”

Section: Geocoronamentioning

confidence: 58%

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

2011

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[1] We investigated, for the first time, long-term variations in reflection heights of tweek atmospherics based on very low frequency (VLF) observations at Kagoshima, Japan. The results revealed the effects of the solar cycle on the nighttime lower ionosphere at low to middle latitudes. The tweek reflection heights on geomagnetically quiet days were analyzed every month over three solar cycles by using an automated spectral fitting procedure to estimate the cutoff frequency. The average and standard deviation of the reflection height were 95.9 km and ±3.1 km, respectively. Typical periods of time variation for the reflection height were 13.3, 3.2, 1.3, 1.0, 0.6, and 0.5 years. The variations in tweek reflection heights did not show simple anticorrelation with solar activity. The correlation coefficient between tweek reflection height and sunspot number was 0.03 throughout the three solar cycles. Hilbert-Huang transform analysis successfully indicated the presence of 0.5-1.5 year and ∼10 year variations as intrinsic mode functions (IMF). The decomposed IMF with the ∼10 year variation had a positive correlation with sunspot numbers and a negative correlation with galactic cosmic rays (GCRs). We hypothesize that these variations in tweek reflection heights could be caused by coupling of several ionization effects at the D and lower E regions, effects such as geocorona, GCRs, particle precipitation, and variations in neutral density in the lower thermosphere. Among these processes, the geocorona and particle precipitation could show negative correlation, while the GCRs and neutral density could show positive correlation with solar activities.Citation: Ohya, H., K. Shiokawa, and Y. Miyoshi (2011), Long-term variations in tweek reflection height in the D and lower E regions of the ionosphere,

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Section: Geocoronamentioning

confidence: 58%

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

2011

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“…If confined to a single element detector, such as a photomultiplier tube (PMT), the interferometer must be scanned through the desired spectral interval, sequentially sampling one spectral resolution element dl at a time. Although there are a number of ways to accomplish this (e.g., mechanical, tilt, or pressure scanning) the method most commonly used in geocoronal Balmer a studies involves pressure scanning (see e.g., Atreya et al, 1975;Meriwether et al, 1980;Shih et al, 1985;Yelle and Roesler, 1985;Harlander and Roesler, 1989;Kerr et al, 1986;Kerr et al, 2001a, b;Nossal et al, 1993).…”

Section: Pressure Scanning and Pressure Tuningmentioning

confidence: 99%

“…Although ground-based Fabry-Perot observations of geocoronal hydrogen have been made over the last several decades with increasing instrumental capabilities (Reynolds et al, 1973;Atreya et al, 1975;Meriwether et al, 1980;Yelle and Roesler, 1985;Shih et al, 1985, Kerr et al, 1986, 2001aKerr and Tepley, 1988;He et al, 1993; , 1997Bishop et al, 2001Bishop et al, , 2004Mierkiewicz, 2002; and references therein), recent advances in detector technology, such as the charged-coupled-device (CCD), and its application to Fabry-Perot spectroscopy (e.g., CCD annular summing spectroscopy), have greatly improved the quality and quantity of geocoronal Balmer a emissions data. Scientific areas of focus include:…”

Section: Introductionmentioning

confidence: 99%

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

Mierkiewicz

Roesler

Nossal

et al. 2006

Journal of Atmospheric and Solar-Terrestrial Physics

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“…Somewhat weaker is the emission between 4652Å and 4650Å, corresponding to the blended The second panel shows the spectral interval 4843Å to 4876Å covering the H β line at 4861Å. There is weak emission at the unshifted line throughout the interval, most probably coming from the scattering in the geocorona or from a galactic source (see the discussion of H α emission by Kerr et al, 2001). Doppler shifted and broadened hydrogen emission is seen between 15:30 UT and 17:00 UT, intensifying at 16:30 UT, and later on as weaker and more time varying emissions between 17:15 UT and 18:00 UT.…”

Section: Data and Analysismentioning

confidence: 99%

Observation of O+ (4P-4D0) lines in electron aurora over Svalbard

et al. 2004

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Abstract. This work reports on observations of O + lines in aurora over Svalbard, Norway. The Spectrographic Imaging Facility measures auroral spectra in three wavelength intervals (H β , N (1,3) band. It is found that in electron aurora, the brightness of this multiplet, is on average, about 0.1 of the N + 2 1N(0,2) total brightness. A joint optical and incoherent scatter radar study of an electron aurora event shows that the ratio is enhanced when the ionisation in the upper E-layer (140-190 km) is significant with respect to the E-layer peak below 130 km. Rayed arcs were observed on one such occasion, whereas on other occasions the auroral intensity was below the threshold of the imager. A one-dimensional electron transport model is used to estimate the cross section for production of the multiplet in electron collisions, yielding 0.18×10 −18 cm 2 .

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Periodic variations of geocoronal Balmer‐alpha brightness due to solar‐driven exospheric abundance variations

Cited by 23 publications

References 37 publications

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

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

Observation of O<sup>+</sup> (<sup>4</sup>P-<sup>4</sup>D<sup>0</sup>) lines in electron aurora over Svalbard

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Periodic variations of geocoronal Balmer‐alpha brightness due to solar‐driven exospheric abundance variations

Cited by 23 publications

References 37 publications

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

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

Observation of O&lt;sup&gt;+&lt;/sup&gt; (&lt;sup&gt;4&lt;/sup&gt;P-&lt;sup&gt;4&lt;/sup&gt;D&lt;sup&gt;0&lt;/sup&gt;) lines in electron aurora over Svalbard

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Observation of O<sup>+</sup> (<sup>4</sup>P-<sup>4</sup>D<sup>0</sup>) lines in electron aurora over Svalbard