Bibliography

The Role of High Energy Photoelectrons on the Dissociation of Molecular Nitrogen in Earth's Ionosphere

Soft x-ray radiation from the sun is responsible for the production of high energy photoelectrons in the D and E regions of the ionosphere, where they deposit most of their ionization

Samaddar, Srimoyee; Venkataramani, Karthik; Yonker, Justin; Bailey, Scott; , others;

Published by: arXiv preprint arXiv:2209.11185      Published on:

YEAR: 2022     DOI: 10.48550/arXiv.2209.11185

Sounding Rocket Observation of Nitric Oxide in the Polar Night

An altitude profile of Nitric Oxide (NO) in the 80–110 km altitude range was measured in the polar night from a sounding rocket on 27 January 2020. The observations were made using the technique of stellar occultation with a UV spectrograph observing the γ (1,0) band of NO near 215 nm. The tangent point for the altitude profile was at 74° latitude, a location that had been in darkness for 80 days. The retrieved slant column density profile is interpreted using an assumed four-parameter analytic profile shape. Retrievals of the fitting parameters yield a profile with a peak NO concentration of 2.2 ± 0.7 × 108 cm−3 at 93.5 ± 4.1 km. The observations were made during a time of minimum solar and geomagnetic activity. The NO maximum retrieved from the rocket profile is significantly larger in abundance and lower in altitude than other observations on the same day at nearby latitudes just outside the polar night. These rocket-borne results are consistent with NO that is created over the course over the polar winter and is confined to high latitudes in the polar night by the mesospheric polar vortex. During the course of that confinement the abundance increases due to the lack of photodissociation, allowing the NO to descend. We show that the observed descent can be explained by eddy diffusion-driven transport, though vertical advection cannot be ruled out.

Bailey, Scott; McClintock, William; Carstens, Justin; Thurairajah, Brentha; Das, Saswati; Randall, Cora; Harvey, Lynn; Siskind, David; Stevens, Michael; Venkataramani, Karthik;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2022     DOI: 10.1029/2021JA030257

Lower thermosphere; mesosphere; nitric oxide; polar night; sounding rocket; stellar occultation

The Role of Solar Soft X-rays Irradiance in Thermospheric Structure

We use a new Atmospheric Chemistry and Energetics one-dimensional (ACE1D) thermospheric model to show that the energies deposited by the solar soft x-rays in the lower

Samaddar, Srimoyee; Venkataramani, Karthik; Bailey, Scott; , others;

Published by: arXiv preprint arXiv:2209.10543      Published on:

YEAR: 2022     DOI: 10.48550/arXiv.2209.10543

A Model of the Globally-averaged Thermospheric Energy Balance

Similar to the MSIS data, we bin the GUVI temperatures by latitude It should be noted that GUVI observations at high values of While the GUVI observations cannot be compared directly

Venkataramani, Karthik; Bailey, Scott; Samaddar, Srimoyee; Yonker, Justin;

Published by: arXiv preprint arXiv:2211.05301      Published on:

YEAR: 2022     DOI: 10.48550/arXiv.2211.05301

Climatological study of the ion temperature in the ionosphere as recorded by Millstone Hill incoherent scatter radar and comparison with the IRI model

Ion temperature data recorded by Millstone Hill incoherent scatter radar (42.61° N, 288.51° E) over four full solar cycles (from 1970 to 2018) are analyzed to depict its climatological behavior in the range of altitudes between 100 and 550 km. The ion temperature dependencies on altitude, local time, month of the year, and solar activity level are studied through a climatological analysis based on binning and boxplot representation of statistical values. Binned observations of ion temperature are compared with International Reference Ionosphere (IRI) modeled values (IRI-2016 version). This comparison reveals several shortcomings in the IRI modeling of the ion temperature at ionosphere altitudes, in particular for the altitudinal, diurnal, seasonal, and solar activity description. The main finding of this study is that the overall IRI overestimation of the ion temperature can be probably ascribed to the long-term ionosphere cooling. Moreover, the study suggests that the IRI ion temperature model needs to implement the seasonal and solar activity dependence, and introduce a more refined diurnal description to allow multiple diurnal maxima seen in observations. The IRI ion temperature anchor point at 430 km is investigated in more detail to show how also a better description of the altitude dependence is desirable for modeling purposes. Some hints and clues are finally given to improve the IRI ion temperature model.

Pignalberi, Alessio; Aksonova, Kateryna; Zhang, Shun-Rong; Truhlik, Vladimir; Gurram, Padma; Pavlou, Charalambos;

Published by: Advances in Space Research      Published on: sep

YEAR: 2021     DOI: 10.1016/j.asr.2020.10.025

Climatological analysis; International Reference Ionosphere model; ion temperature; Millstone Hill incoherent scatter radar

Comparison of the Thermospheric Nitric Oxide Emission Observations and the GITM Simulations: Sensitivity to Solar and Geomagnetic Activities

An accurate estimate of the energy budget (heating and cooling) of the ionosphere and thermosphere, especially during space weather events, has been a challenge. The abundance of Nitric Oxide (NO), a minor species in the thermosphere, is an important component of energy balance here because its production comes from energy sources able to break the strong bond of molecular nitrogen, and infrared emissions from NO play an important role in thermospheric cooling. Recent studies have significantly improved our understanding of NO chemistry and its relationship to energy deposition in the thermospheric photochemical reactions. In this study, the chemical scheme in the Global Ionosphere Thermosphere Model (GITM) is updated to better predict the lower thermospheric NO responses to solar and geomagnetic activity. We investigate the sensitivity of the 5.3-micron NO emission to F10.7 and Ap indices by comparing the global integrated emission from GITM with an empirical proxy derived from the Sounding of the Atmosphere using Broadband Emission Radiometry measurements. GITM\textquoterights total emission agrees well within 20\% of the empirical values. The updated chemistry scheme significantly elevates the level of integrated emission compared to the previous scheme. The inclusion of N2(A)-related production of NO contributes an additional 5-25\% to the emission. Localized enhancement of ~70\% in column density and a factor of three in column emission are simulated at a moderate geomagnetic level.

Lin, Cissi; Deng, Yue; Venkataramani, Karthik; Yonker, Justin; Bailey, Scott;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2018

YEAR: 2018     DOI: 10.1029/2018JA025310

Comparison of the Thermospheric Nitric Oxide Emission Observations and the Global Ionosphere-Thermosphere Model (GITM) Simulations: Sensitivity to Solar and Geomagnetic Activities

The magnitude of enhancement observed in column density agrees well with the cases observed by TIMED/GUVI −8 W/m3) agree well with TIMED/SABER and GUVI measurements.

Lin, Cissi; Deng, Yue; Venkataramani, Karthik; Yonker, Justin; Bailey, Scott;

Published by: arXiv preprint arXiv:1807.01380      Published on:

YEAR: 2018     DOI: https://doi.org/10.48550/arXiv.1807.01380

Parameterization of Nitric Oxide Emissions in the Thermosphere

Lin, CYT; Deng, Yue; Venkataramani, Karthik; Yonker, Justin; Bailey, Scott;

Published by:       Published on:

YEAR: 2016     DOI:

Electron precipitation models in global magnetosphere simulations

General methods for improving the specification of electron precipitation in global simulations are described and implemented in the Lyon-Fedder-Mobarry (LFM) global simulation model, and the quality of its predictions for precipitation is assessed. LFM\textquoterights existing diffuse and monoenergetic electron precipitation models are improved, and new models are developed for lower energy, broadband, and direct-entry cusp precipitation. The LFM simulation results for combined diffuse plus monoenergetic electron precipitation exhibit a quadratic increase in the hemispheric precipitation power as the intensity of solar wind driving increases, in contrast with the prediction from the OVATION Prime (OP) 2010 empirical precipitation model which increases linearly with driving intensity. Broadband precipitation power increases approximately linearly with driving intensity in both models. Comparisons of LFM and OP predictions with estimates of precipitating power derived from inversions of Polar satellite UVI images during a double substorm event (28\textendash29 March 1998) show that the LFM peak precipitating power is \>4\texttimes larger when using the improved precipitation model and most closely tracks the larger of three different inversion estimates. The OP prediction most closely tracks the double peaks in the intermediate inversion estimate, but it overestimates the precipitating power between the two substorms by a factor \>2 relative to all other estimates. LFMs polar pattern of precipitating energy flux tracks that of OP for broadband precipitation exhibits good correlation with duskside region 1 currents for monoenergetic energy flux that OP misses and fails to produce sufficient diffuse precipitation power in the prenoon quadrant that is present in OP. The prenoon deficiency is most likely due to the absence of drift kinetic physics in the LFM simulation.

Zhang, B.; Lotko, W.; Brambles, O.; Wiltberger, M.; Lyon, J.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2015

YEAR: 2015     DOI: 10.1002/2014JA020615

electron precipitation; global magnetosphere simulation; magnetosphere-ionosphere coupling

Impacts of atmospheric ultrafast Kelvin waves on radio scintillations in the equatorial ionosphere

We present a statistical analysis of the amplitudes of GPS scintillations (S4 index) observed throughout 2008\textendash2010 using the satellite radio occultation measurements of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). Here, for the first time, periodic variability in the occurrence of S4 is investigated using these data. Significant variations of S4 with periods of 2.5\textendash4 days (quasi-3 days) are identified from the observations during postsunset hours (1900\textendash2400 local time) between 15\textdegreeS\textendash 15\textdegreeN magnetic latitude during this 3 year interval. Coherence analyses of these variations with the geomagnetic Ap index, solar EUV irradiance, and atmospheric wind measurements from an equatorial mesosphere meteor radar at Thumba, India ( 8.5\textdegreeN, 77\textdegreeE) are performed, providing a measure of the relationship between variations in the scintillations and potential drivers. The quasi-3 day variations in S4 are found to covary with the variations of the three drivers examined. In particular, the S4 signatures are found to be coherent with the atmospheric ultrafast Kelvin (UFK) planetary waves characterized by the zonal wind measurements of the radar. This study shows that these UFK waves are as important as the solar and geomagnetic drivers in forcing the day-to-day variations of the occurrence of equatorial spread F.

Liu, Guiping; Immel, Thomas; England, Scott; Frey, Harald; Mende, Stephen; Kumar, Karanam; Ramkumar, Geetha;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2013

YEAR: 2013     DOI: 10.1002/jgra.50139

day-to-day variability; Equatorial ionosphere; scintillation; Ultra Fast Kelvin planetary wave

Ionospheric and thermospheric storms at equatorial latitudes observed by CHAMP, ROCSAT, and DMSP

Balan, N.; Liu, J; Otsuka, Y.; Ram, Tulasi; ühr, H.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2012

YEAR: 2012     DOI: 10.1029/2011JA016903

Effects observed in the equatorial and low latitude ionospheric F-region in the Brazilian sector during low solar activity geomagnetic storms and comparison with the COSMIC measurements

The main objective of the present investigation has been to compare the ionospheric parameters (NmF2 and hmF2) observed by two ground-based ionospheric sounders (one at PALMAS- located near the magnetic equator and the other at Sao Jose dos Campos-located in the low-latitude region) in the Brazilian sector with that by the satellite FORMOSAT-3/COSMIC radio occultation (RO) measurements during two geomagnetic storms which occurred in December 2006 and July 2009. It should be pointed out that in spite of increasing the latitude (to 10\textdegree) and longitude (to 20\textdegree) around the stations; we had very few common observations. It has been observed that both the peak electron density (NmF2) and peak height (hmF2) observed by two different techniques (space-borne COSMIC and ground-based ionosondes) during both the geomagnetic storm events compares fairly well (with high correlation coefficients) at the two stations in the Brazilian sector. It should be pointed out that due to equatorial spread F (ESF) in the first storm (December 2006) and no-reflections from the ionosphere during nighttime in the second storm (July 2009), we had virtually daytime data from the two ionosondes.

Sahai, Y.; de Jesus, R.; Fagundes, P.R.; Selhorst, C.L.; de Abreu, A.J.; Ram, Tulasi; Aragon-Angel, A.; Pillat, V.G.; Abalde, J.R.; Lima, W.L.C.; Bittencourt, J.A.;

Published by: Advances in Space Research      Published on: 11/2012

YEAR: 2012     DOI: 10.1016/j.asr.2012.07.006

COSMIC satellite; F-region; geomagnetic storm; Ionosphere; Low solar activity

Dayside ionospheric response to recurrent geomagnetic activity during the extreme solar minimum of 2008

Ram, Tulasi; Lei, J.; Su, S.-Y.; Liu, C.; Lin, C.; Chen, W.;

Published by: Geophysical Research Letters      Published on: Jan-01-2010

YEAR: 2010     DOI: 10.1029/2009GL041038

FORMOSAT-3/COSMIC observations of seasonal and longitudinal variations of equatorial ionization anomaly and its interhemispheric asymmetry during the solar minimum period

Ram, Tulasi; Su, S-Y; Liu, CH;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2009     DOI:

Correlative study of plasma bubbles, evening equatorial ionization anomaly, and equatorial prereversal E$\times$ B drifts at solar maximum

Previous ground observations have revealed a correlation that exists between equatorial plasma bubbles, evening equatorial ionization anomaly (EIA), and prereversal E × B drift velocity using latitudinal arrays of ionospheric sounders, such as in the Indian and American regions. Besides the ground measurements, the space-based observations also provide a convenient way to study the global-scale variations.

Li, Guozhu; Ning, Baiqi; Liu, Libo; Zhao, Biqiang; Yue, Xinan; Su, S-Y; Venkatraman, Sarita;

Published by: Radio Science      Published on:

YEAR: 2008     DOI: 10.1029/2007RS003760

Measurements of X-ray emission from rocket-triggered lightning

, Dwyer; Rassoul, HK; Al-Dayeh, M; Caraway, L; Wright, B; Chrest, A; Uman, MA; Rakov, VA; Rambo, KJ; Jordan, DM; , others;

Published by: Geophysical Research Letters      Published on:

YEAR: 2004     DOI: