Bibliography

A method to derive global O/N2 ratios from SSUSI/DMSP based on Re-AURIC algorithm

Global thermospheric O/N₂ column density ratios are obtained using the SSUSI/DMSP far-ultraviolet (FUV) dayglow data and the Re-AURIC simulation results. The Re-AURIC is derived from the AURIC algorithm after some old modules are updated. The calculation processes of O/N₂ ratio are then established using the simulations of Re-AURIC to calibrate the ratios of the OI 135.6\ nm emission and N₂ LBHS emission from SSUSI observations. The standard deviation (1σ) and correlation coefficient are 0.045 and 0.769 compared with the O/N₂ ratios provided by the SSUSI EDR data. The statistical errors between the calculated ratios and the EDR references are generally less than 0.2 with 96.40\% at 2σ (95.44\%) and less than 0.1 with 60.51\% at about 1σ (68.26\%). Two global O/N₂ ratio maps are obtained using this method to study its variations when the magnetic storm occurs. The significant O/N₂ depletion can be seen in one O/N₂ ratio map whose Kp index is 6. Also, the depletion is not uniform at different longitudes and the scales extend from high latitude to low latitude during magnetic storm. This proposed method provides us with a simple and useful tool to obtain the global O/N₂ distribution and even the future modeling from the observations on satellites.

Ding, GuangXing; Chen, Bo; Zhang, Xiaoxin; He, Fei;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 03/2020

YEAR: 2020     DOI: 10.1016/j.jastp.2020.105196

FUV dayglow; Magnetic storm; O/N2 ratio; Re-AURIC

Comparison of Reference Heights of O/N ₂ and ∑O/N ₂ Based on GUVI Dayside Limb Measurement

We define a new thermospheric concept, the reference heights of O/N₂, referring to a series of thermospheric heights corresponding to the fixed ratios of O to N₂ number density. Here, based on Global Ultraviolet Imager (GUVI) limb measurement, we compare O/N₂ column density ratio (∑O/N₂) and the reference heights of O/N₂. We choose the transition height of O and N₂ (transition height hereafter), a special reference height at which O number density is equal to N₂ number density, to verify the connection with ∑O/N₂ during geomagnetically quiet periods. It is found that transition height and ∑O/N₂ have noticeable negative correlation with correlation coefficient of -0.887. An empirical model of transition height (O/N₂ model hereafter) is established based on nonlinear least-squares-fitting method. The considerable correlation (greater than 0.96), insignificant errors (less than 4\%) and the great influencing weight of ∑O/N₂ to reference heights indicate the validity of O/N₂ model and the existence of quantitative relation between ∑O/N₂ and transition height. Besides, it is verified that the similar quantitative relation also exists between ∑O/N₂ and reference heights of other O/N₂ values. Namely, using the O/N₂ model coefficients, we can roughly get the whole altitude profiles of O/N₂ within 6\% precision for any given ∑O/N₂.

Yu, Tingting; Ren, Zhipeng; Yu, You; Yue, Xinan; Zhou, Xu; Wan, Weixing;

Published by: Space Weather      Published on: 01/2020

YEAR: 2020     DOI: 10.1029/2019SW002391

O/N2 ratio

Ionospheric response to a geomagnetic storm during November 8--10, 2004

This paper investigates the response of the equatorial, and near equatorial, ionosphere to geomagnetic disturbances during the period November 8-10, 2004. Ionosonde data from Trivandrum (8.5\textdegreeN 77\textdegreeE and dip 0.5\textdegreeN) and SHAR (13.5\textdegreeN, 80.2\textdegreeE, dip \~5.5\textdegreeN), magnetic field data from Tirunelveli (8.7\textdegreeN, 76.9\textdegreeE, dip latitude 0.5\textdegreeS) and Alibag (18.64\textdegreeN, 72.87\textdegreeE), and GUVI O/N₂ data in the Indian longitude sector, are used for the study. The behavior of interplanetary parameters is also examined in conjunction with the ionospheric data. On 8 November, the EIA around noontime is not fully inhibited even though the electrojet strength an indicates inhibition of EIA due to a disturbance dynamo electric field effect. It is the enhanced O/N₂ over TRV and SHAR, with a larger increase over SHAR, which results in a larger (than expected) value of the EIA proxy parameter. On 9 November, the comparable values of f_oF₂ at TRV and SHAR around noon time is due to the combined effect of a weakened anomaly in the presence disturbance dynamo electric field effects leading to the EIA crest being near SHAR, and increased O/N₂ values at TRV and SHAR with a larger increase at TRV. On 10 November, the very strong values of the EIA proxy-SHAR parameter is attributed to the combined effects of prompt penetration electric field related modulations of EIA, and significant O/N₂ changes at the equatorial, and near equatorial, latitude. Thus, the study reveals the important role of storm-induced O/N₂ changes, along with prompt penetration electric fields and disturbance dynamo electric fields in modulating the ionization distribution in the equatorial ionization anomaly (EIA) region during this period.

Simi, K.; Manju, G.; Haridas, M.; Nayar, S.; Pant, Tarun; Alex, S.;

Published by: Earth, Planets and Space      Published on: 05/2013

YEAR: 2013     DOI: 10.5047/eps.2012.09.005

Equatorial Electrojet; Equatorial ionization anomaly; geomagnetic storm; O/N2 ratio