Ionospheric electron content at temperate latitudes during the declining phase of the sunspot cycle

Yeh, K. C.; Flaherty, B. J.

doi:10.1029/jz071i019p04557

Cited by 35 publications

(7 citation statements)

References 18 publications

(13 reference statements)

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“…In Table 1 we also list several bulk statistics such as Kp index, 10.7 cm flux (F10.7) 3 , and mean TEC at the MRO 4 . The solar flux at 10.7 cm is an often used index of solar activity and is known to correlate with the emission of the UV photons responsible for generating the free electrons that impact ionospheric radio propagation (Yeh & Flaherty 1966;Titheridge 1973;da Rosa et al 1973) with values ranging between 50 and 300 SFU (1 SFU=10 −22 W m −2 ). The Kp index (Bartels et al 1939), quantifies the severity of geomagnetic activity and combines many local measurements of the maximal horizontal displacement of the Earth's magnetic field.…”

Section: Ionospheric Contaminationmentioning

confidence: 99%

First limits on the 21 cm power spectrum during the Epoch of X-ray heating

Ewall‐Wice

Dillon

Hewitt

et al. 2016

Mon. Not. R. Astron. Soc.

103

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We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). Three hours of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1-3 hours of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 10 4 mK on comoving scales k 0.5 hMpc −1 . This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 z 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.

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Section: Ionospheric Contaminationmentioning

confidence: 99%

First limits on the 21 cm power spectrum during the Epoch of X-ray heating

Ewall‐Wice

Dillon

Hewitt

et al. 2016

Mon. Not. R. Astron. Soc.

103

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“…The solar activity dependence of ionospheric F2 parameters has been studied for a long period. The critical frequency of the F2 layer (foF2) or peak density (N m F2) [23,[35][36][37][38][39][40][41][42][43][44], peak height (h m F2) [6,23,40], TEC [29][30][31][45][46][47][48][49][50][51], plasma temperature and scale height [40,51], and thermosphere winds [52][53][54][55], temperature and neutral compositions [55][56][57] have been recently invest-igated. These studies mainly discussed the complicated trends and sensitivity of the solar activity dependency of the ionosphere, the detailed features and physical processes, and how to represent those characteristics effectively in applications.…”

Section: Features Around the F2 Peakmentioning

confidence: 99%

Solar activity effects of the ionosphere: A brief review

et al. 2011

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Solar radiation, which varies over multiple temporal scales, modulates remarkably the evolution of the ionosphere. The solar activity dependence of the ionosphere is a key and fundamental issue in ionospheric physics, providing information essential to understanding the variations in the ionosphere and its processes. Selected recent studies on solar activity effects of the ionosphere are briefly reviewed in this report. This report focuses on (1) observations of solar irradiance at X-ray and extreme ultraviolet wavelengths and the outstanding problems of solar proxies, in the view of ionospheric studies, (2) new findings and improved representations of the features of the solar activity dependence of ionospheric key parameters and the corresponding physical processes, (3) possible phenomena in the ionosphere under extremely high and low solar activity conditions that are unique, as indicated by historical solar datasets and the deep solar minimum of solar cycle 23/24, and (4) statistical studies and model simulations of the ionosphere response to solar flares. The above-mentioned studies provide new clues for comprehensively explaining basic processes in the ionosphere and improving the prediction capability of ionospheric models and related applications.

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“…Slab-thickness has been used by a number of workers as an index of temperature (Bhonsle et al, 1965;Hibberd and Ross, 1966). Yeh and Flaherty (1966) have derived an empirical relation between the electron to ion temperature ratio (T e /T i ) and slabthickness for a hybrid model with Chapman type on bottom side and diffusion type transport on topside. The slabthickness depends on the scale height of the ionizable constituents and the scale height of loss processes, both of which are dependent on neutral temperature and hence can be indicated by the slab-thickness (Mahajan et al, 1968;Titheridge, 1973;Pande et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Study of TEC, slab-thickness and neutral temperature of the thermosphere in the Indian low latitude sector

et al. 2011

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Abstract. The ionospheric equivalent slab-thickness is an important parameter which measures the skewness of the electron density profile of the ionosphere. In this paper, the diurnal, seasonal, day-to-day and latitudinal variations of ionospheric parameters namely total electron content (TEC), the peak ionization density of F-layer (NmF2), equivalent slab-thickness (τ ) and neutral temperature (T n ) are presented. The simultaneous data of GPS-TEC and NmF2 from Trivandrum (8.47 • N, 76.91 • E), Waltair (17.7 • N, 83.3 • E) and Delhi (28.58 • N, 77.21 • E) are used to compute the slabthickness (τ = TEC/NmF2) of the low sunspot period, [2004][2005]. The day-time TEC values at Waltair are found to be greater than those at Trivandrum, while at Delhi the day-time TEC values are much lower compared to those at Trivandrum and Waltair. The trends of variation in the monthly mean diurnal variation of TEC and NmF2 are similar at Delhi, while they are different at Trivandrum and Waltair during the daytime. The slab-thickness (τ ) has shown a pre-sunrise peak around 05:00 LT at all the three stations, except during the summer months over Delhi. A consistent secondary peak in slab-thickness around noon hours has also been observed at Trivandrum and Waltair. During equinox and winter months a large night-time enhancement in the slab-thickness (comparable to the early morning peak in slab-thickness) is observed at Delhi. The latitudinal variation of slab-thickness has shown a decrease from the equatorial station, Trivandrum to the low-mid latitude station, Delhi. The neutral temperatures (T n ) computed from the slab-thickness (τ ) has shown a sharp increase around 05:00 LT over Trivandrum and Waltair. Whereas at Delhi, a double peaking around 05:00 and 23:00 LT is observed during winter and equinoctial months. The neutral temperatures computed are compare well with those of the MSIS-90 model derived temperatures.

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Ionospheric electron content at temperate latitudes during the declining phase of the sunspot cycle

Cited by 35 publications

References 18 publications

First limits on the 21 cm power spectrum during the Epoch of X-ray heating

First limits on the 21 cm power spectrum during the Epoch of X-ray heating

Solar activity effects of the ionosphere: A brief review

Study of TEC, slab-thickness and neutral temperature of the thermosphere in the Indian low latitude sector

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