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Found 107 entries in the Bibliography.

Showing entries from 51 through 100

2012

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

The global thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming event

This paper presents a study of thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming (SSW) event. This period was characterized by low solar and geomagnetic activity. The study was performed using the Global Self-consistent Model of Thermosphere, Ionosphere, and Protonosphere (GSM TIP). Model results were compared with ionosonde data from Irkutsk, Kaliningrad, Sao Jose dos Campos, and Jicamarca. The SSW event was modeled by specifying the temperature and density perturbations at the lower boundary of the GSM TIP (80 km altitude). GSM TIP simulation allowed the reproduction of the lower thermosphere temperature disturbances (the occurrence of the quasi-wave 1 structure at 80\textendash130 km altitude with a vertical scale of \~40 km), the negative response of F2 region electron density and the positive response of electron temperature at 300 km during the 2008 minor SSW event. The main formation mechanism of the global ionospheric response is due to the disturbances (decrease) in then(O)/n(N2) ratio. The change in zonal electric field is another important mechanism of the ionospheric response at low latitudes.

Korenkov, Y.; Klimenko, V.; Klimenko, M.; Bessarab, F.; Korenkova, N.; Ratovsky, K.; Chernigovskaya, M.; Shcherbakov, A.; Sahai, Y.; Fagundes, P.; de Jesus, R.; de Abreu, A.; Condor, P.;

Published by: Journal of Geophysical Research Published on: 10/2012

YEAR: 2012 DOI: 10.1029/2012JA018018

Electric field; Ionosphere; sudden stratospheric warming; thermosphere

Global observations of E region plasma density morphology and variability

The global morphology and variability of the ionospheric E region plasma density are estimated from satellite-based radio occultation total electron content (ROTEC) measurements. Vertical profiles of E region electron density are estimated using the inversion technique recently proposed by Nicolls et al. (2009). In this technique, the F-region contribution to each ROTEC measurement is removed using an assimilative model of the ionosphere in order to mitigate the effects of F-region gradients in the estimation of E region profiles. The technique is applied to occultation observations made by GPS receivers onboard COSMIC satellites aided by F-region electron density specification provided by the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm. Global estimates of hmE, NmE, and E region total electron content (TEC) are presented for two different months: April 2007 and January 2008. Results of our analysis show that ROTEC measurements such as those provided by the COSMIC constellation can produce reasonable and valuable estimates of E region parameters on a global scale when properly treated for the effect of F-region density gradients. The agreement between the α-Chapman theory of ionization and recombination and estimated profiles is demonstrated. Reasonable estimates of E region variability can also be specified by the global measurements. The dependence of the E region variability on latitude is quantified and presented.

Nicolls, Michael; Rodrigues, Fabiano; Bust, Gary;

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

YEAR: 2012 DOI: https://doi.org/10.1029/2011JA017069

E region electron density; E region morphology; E region variability; radio occultation

Characteristics of traveling ionospheric disturbances observed by the TIDDBIT sounder

Crowley, Geoff; Rodrigues, FS;

Published by: Radio Science Published on:

YEAR: 2012 DOI:

Towards ISO standard earth ionosphere and plasmasphere model

Space exploration has been identified by several governments as a priority for their space agencies and commercial industry. A good knowledge and specification of the

Gulyaeva, TL; Bilitza, Dieter;

Published by: New developments in the standard model Published on:

YEAR: 2012 DOI:

2011

The production of Titan\textquoterights ultraviolet nitrogen airglow

Stevens, Michael; Gustin, Jacques; Ajello, Joseph; Evans, Scott; Meier, R.; Kochenash, Andrew; Stephan, Andrew; Stewart, Ian; Esposito, Larry; McClintock, William; Holsclaw, Greg; Bradley, Todd; Lewis, B.; Heays, A.;

Published by: Journal of Geophysical Research Published on: Jan-01-2011

YEAR: 2011 DOI: 10.1029/2010JA016284

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21--22 January 2005

Sahai, Y.; Fagundes, P.; de Jesus, R.; de Abreu, A.; Crowley, G.; Kikuchi, T.; Huang, C.-S.; Pillat, V.; Guarnieri, F.; Abalde, J.; Bittencourt, J.;

Published by: Annales Geophysicae Published on: Jan-01-2011

YEAR: 2011 DOI: 10.5194/angeo-29-919-2011

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21--22 January 2005

Sahai, Y.; Fagundes, P.; de Jesus, R.; de Abreu, A.; Crowley, G.; Kikuchi, T.; Huang, C.-S.; Pillat, V.; Guarnieri, F.; Abalde, J.; Bittencourt, J.;

Published by: Annales Geophysicae Published on: Jan-01-2011

YEAR: 2011 DOI: 10.5194/angeo-29-919-2011

Effects of geomagnetic super storms on the ionospheric F-region in the South American sector using a GPS technique: A review

Sahai, Y; De Abreu, AJ; Fagundes, PR; De Jesus, R; Crowley, G; Klimenko, MV; Klimenko, VV; Brunini, C; Gende, M; Pillat, VG; , others;

Published by: Asian Journal of Physics Published on:

YEAR: 2011 DOI:

Numerical modeling of ionospheric effects in the middle-and low-latitude F region during geomagnetic storm sequence of 9--14 September 2005

This study presents the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations of the 9–14 September 2005 geomagnetic

Klimenko, MV; Klimenko, VV; Ratovsky, KG; Goncharenko, LP; Sahai, Y; Fagundes, PR; De Jesus, R; De Abreu, AJ; Vesnin, AM;

Published by: Radio Science Published on:

YEAR: 2011 DOI:

2010

Astronomy and Astrophysics Library. The Earth as a Distant Planet. The Outer Layers of the Earth

azquez, M.; e, Pall\; iguez, P.;

Published by: Published on:

YEAR: 2010 DOI: 10.1007/978-1-4419-1684-610.1007/978-1-4419-1684-6_4

Seasonal variations in ionospheric F-region parameters during the low solar activity period in the Brazilian sector and comparison with ionospheric models

Sahai, Yogeshwar; de Jesus, Rodolfo; Fagundes, Paulo; de Abreu, Alessandro; Crowley, Geoff; Pillat, Valdir; Guede, Jose; Bittencourt, Jose;

Published by: 38th COSPAR Scientific Assembly Published on:

YEAR: 2010 DOI:

Seasonal variations in ionospheric F-region parameters during the low solar activity period in the Brazilian sector and comparison with ionospheric models

Sahai, Yogeshwar; de Jesus, Rodolfo; Fagundes, Paulo; de Abreu, Alessandro; Crowley, Geoff; Pillat, Valdir; Guede, Jose; Bittencourt, Jose;

Published by: 38th COSPAR Scientific Assembly Published on:

YEAR: 2010 DOI:

Searching Across Multiple Datasets with the Virtual ITM Observatory

Morrison, D; Weiss, M; Immer, EA; Patrone, D; Potter, M; Barnes, RJ; Colclough, C; Holder, R; McGuire, RE; Candey, RM; , others;

Published by: Published on:

YEAR: 2010 DOI:

2009

Overview and summary of the Spread F Experiment (SpreadFEx)

We provide here an overview of, and a summary of results arising from, an extensive experimental campaign (the Spread F Experiment, or SpreadFEx) performed from September to November 2005, with primary measurements in Brazil. The motivation was to define the potential role of neutral atmosphere dynamics, specifically gravity wave motions propagating upward from the lower atmosphere, in seeding Rayleigh-Taylor instability (RTI) and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12, and the GUVI instrument aboard the TIMED satellite.\

Initial results of our SpreadFEx analyses are described separately by Fritts et al. (2009). Further analyses of these data provide additional evidence of 1) gravity wave (GW) activity near the mesopause apparently linked to deep convection predominantly to the west of our measurement sites, 2) small-scale GWs largely confined to lower altitudes, 3) larger-scale GWs apparently penetrating to much higher altitudes, 4) substantial GW amplitudes implied by digisonde electron densities, and 5) apparent influences of these perturbations in the lower F-region on the formation of equatorial spread F, RTI, and plasma bubbles extending to much higher altitudes. Other efforts with SpreadFEx data have also yielded 6) the occurrence, locations, and scales of deep convection, 7) the spatial and temporal evolutions of plasma bubbles, 8) 2-D (height-resolved) structures in electron density fluctuations and equatorial spread F at lower altitudes and plasma bubbles above, and 9) the occurrence of substantial tidal perturbations to the large-scale wind and temperature fields extending to bottomside F-layer and higher altitudes. Collectively, our various SpreadFEx analyses suggest direct links between deep tropical convection and large GW perturbations at large spatial scales at the bottomside F-layer and their likely contributions to the excitation of RTI and plasma bubbles extending to much higher altitudes.

Fritts, D.; Abdu, M.; Batista, B.; Batista, I.; Batista, P.; Buriti, R.; Clemesha, B.; Dautermann, T.; de Paula, E.; Fechine, B.; Fejer, B.; Gobbi, D.; Haase, J.; Kamalabadi, F.; Kherani, E.; Laughman, B.; Lima, P.; Liu, H.-L.; Medeiros, A.; Pautet, P.-D.; Riggin, D.; Rodrigues, F.; Sabbas, F.; Sobral, J.; Stamus, P.; Takahashi, H.; Taylor, M.; Vadas, S.; Vargas, F.; Wrasse, C.;

Published by: Annales Geophysicae Published on: Jan-01-2009

YEAR: 2009 DOI: 10.5194/angeo-27-2141-2009

Near Earth space plasma monitoring under COST 296

This review paper presents the main achievements of the near Earth space plasma monitoring under COST 296

Action. The outputs of the COST 296 community making data, historical and real-time, standardized and available\ to the ionospheric community for their research, applications and modeling purposes are presented. The contribution\ of COST 296 with the added value of the validated data made possible a trusted ionospheric monitoring\ for research and modeling purposes, and it served for testing and improving the algorithms producing real-time

data and providing data users measurement uncertainties. These value added data also served for calibration and

validation of space-borne sensors. New techniques and parameters have been developed for monitoring the near\ Earth space plasma, as time dependent 2D maps of vertical total electron content (vTEC), other key ionospheric\ parameters and activity indices for distinguishing disturbed ionospheric conditions, as well as a technique for improving\ the discrepancies of different mapping services. The dissemination of the above products has been developed\ by COST 296 participants throughout the websites making them available on-line for real-time applications.

Altadill, D.; Boska, J.; Cander, L.; Gulyaeva, T.; Reinisch, B.; Romano, V.; Krankowski, A.; Bremer, J.; Belehaki, A.; Stanislawska, I.; Jakowski, N.; Scotto, C.;

Published by: Annals of Geophysics Published on: 06/2009

YEAR: 2009 DOI:

Response of the Ionospheric F-region in the Latin American Sector During the Intense Geomagnetic Storm of 21-22 January 2005

Sahai, Y; Fagundes, PR; De Jesus, R; De Abreu, AJ; Crowley, G; Pillat, VG; Guarnieri, FL; , Abalde; Bittencourt, JA;

Published by: Published on:

YEAR: 2009 DOI:

Response of the Ionospheric F-region in the Latin American Sector During the Intense Geomagnetic Storm of 21-22 January 2005

Sahai, Y; Fagundes, PR; De Jesus, R; De Abreu, AJ; Crowley, G; Pillat, VG; Guarnieri, FL; , Abalde; Bittencourt, JA;

Published by: Published on:

YEAR: 2009 DOI:

Estimating E region density profiles from radio occultation measurements assisted by IDA4D

Nicolls, MJ; Rodrigues, FS; Bust, GS; Chau, JL;

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

YEAR: 2009 DOI:

The Spread F Experiment (SpreadFEx): Program overview and first results

Fritts, D.; Abdu, M.; Batista, B.; Batista, I.; Batista, P.; Buriti, R.; Clemesha, B.; Dautermann, T.; de Paula, E.; Fechine, B.; Fejer, B.; Gobbi, D.; Haase, J.; Kamalabadi, F.; Kherani, E.; Laughman, B.; Lima, J.; Liu, H.-L.; Medeiros, A.; Pautet, P.-D.; Riggin, D.; Rodrigues, F.; Sabbas, Sao; Sobral, J.; Stamus, P.; Takahasi, H.; Taylor, M.; Vadas, S.; Vargas, F.; Wrasse, C.;

Published by: Earth Planets Space Published on:

YEAR: 2009 DOI:

Effects observed in the Latin American sector ionospheric F region during the intense geomagnetic disturbances in the early part of November 2004

Sahai, Y; Becker-Guedes, F; Fagundes, PR; De Jesus, R; De Abreu, AJ; Paxton, LJ; Goncharenko, LP; Brunini, C; Gende, M; Ferreira, AS; , others;

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

YEAR: 2009 DOI:

Effects observed in the Latin American sector ionospheric F region during the intense geomagnetic disturbances in the early part of November 2004

Sahai, Y; Becker-Guedes, F; Fagundes, PR; De Jesus, R; De Abreu, AJ; Paxton, LJ; Goncharenko, LP; Brunini, C; Gende, M; Ferreira, AS; , others;

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

YEAR: 2009 DOI:

The Production of Titan’s Far Ultraviolet Nitrogen Airglow

Stevens, Michael; Gustin, Jacques; Ajello, Joseph; Evans, Scott; Meier, RR; Stephan, Andrew; Stewart, Ian; Larsen, Kristopher; Esposito, Larry; McClintock, William;

Published by: Space Published on:

YEAR: 2009 DOI:

2008

Simultaneous appearance of isolated auroral arcs and Pc 1 geomagnetic pulsations at subauroral latitudes

Sakaguchi, Kaori; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Otsuka, Yuichi; Ogawa, Tadahiko; Asamura, Kazushi; Connors, M;

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

YEAR: 2008 DOI:

Incoherent and coherent scatter radar studies of the equatorial F region

Radio waves are weakly scattered by thermal fluctuations in the quasiequilibrium ionospheric plasma. Coherent scatter echoes, meanwhile, are caused by non-thermal electron density fluctuations generated by plasma instabilities and are much stronger than incoherent scatter (IS) echoes. The spectra of IS echoes provide information about parameters of the background plasma such as electron density, temperatures, and ion composition. On the other hand, coherent scatter echoes provide an indication of the turbulent state of the ionospheric plasma. This dissertation describes coherent and incoherent backscatter radar observations of the F region ionosphere in the magnetic equatorial region using the Jicamarca IS radar in Peru and the Sao Lu ˜ ´ıs coherent backscatter radar in Brazil.

Rodrigues, Fabiano;

Published by: Published on:

YEAR: 2008 DOI:

Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread F

Rodrigues, FS; Hysell, DL; de Paula, ER;

Published by: Published on:

YEAR: 2008 DOI:

Leveraging Capabilities in the Community: CDAWeb Data and Services within VITMO

Bilitza, D; Barnes, R; Candey, R; Harris, B; Holder, R; Immer, E; McGuire, R; Morrison, D; Patrone, D; Potter, M; , others;

Published by: Published on:

YEAR: 2008 DOI:

Enabling Science Research with Coordinated Data From SuperDARN and VITMO

Barnes, RJ; Morrison, D; Weiss, M; Immer, E; Potter, M; Holder, R; Patrone, D; Colclough, C; McGuire, R; Candey, R; , others;

Published by: Published on:

YEAR: 2008 DOI:

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y.; Becker-Guedes, F.; Fagundes, P.R.; Lima, W.L.C.; de Abreu, A.J.; Guarnieri, F.L.; Candido, C.M.N.; Pillat, V.G.;

Published by: Published on:

YEAR: 2008 DOI:

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y.; Becker-Guedes, F.; Fagundes, P.R.; Lima, W.L.C.; de Abreu, A.J.; Guarnieri, F.L.; Candido, C.M.N.; Pillat, V.G.;

Published by: Published on:

YEAR: 2008 DOI:

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y.; Becker-Guedes, F.; Fagundes, P.R.; Lima, W.L.C.; de Abreu, A.J.; Guarnieri, F.L.; Candido, C.M.N.; Pillat, V.G.;

Published by: Published on:

YEAR: 2008 DOI:

2007

Brazilian ionosphere behavior during an intense solar flare

The 28 October 2003 solar flare was one of the most intense solar flares observed in the recent past. In the present investigation we show the ionospheric effects observed in the

Becker-Guedes, F; Sahai, Y; Fagundes, PR; Abreu, A; Pillat, VG; Lima, WLC;

Published by: Published on:

YEAR: 2007 DOI: https://doi.org/10.3997/2214-4609-pdb.172.SBGF0393_07

Brazilian ionosphere behavior during an intense solar flare

The 28 October 2003 solar flare was one of the most intense solar flares observed in the recent past. In the present investigation we show the ionospheric effects observed in the

Becker-Guedes, F; Sahai, Y; Fagundes, PR; Abreu, A; Pillat, VG; Lima, WLC;

Published by: Published on:

YEAR: 2007 DOI: https://doi.org/10.3997/2214-4609-pdb.172.SBGF0393_07

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y; Becker-Guedes, F; Fagundes, PR; Lima, WLC; De Abreu, AJ; Guarnieri, FL; Candido, CMN; Pillat, VG;

Published by: Published on:

YEAR: 2007 DOI:

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y; Becker-Guedes, F; Fagundes, PR; Lima, WLC; De Abreu, AJ; Guarnieri, FL; Candido, CMN; Pillat, VG;

Published by: Published on:

YEAR: 2007 DOI:

Unusual ionospheric effects observed during the intense 28 October 2003 solar flare in the Brazilian sector

Sahai, Y; Becker-Guedes, F; Fagundes, PR; Lima, WLC; De Abreu, AJ; Guarnieri, FL; Candido, CMN; Pillat, VG;

Published by: Published on:

YEAR: 2007 DOI:

Prelude to THEMIS tail conjunction study

Lui, ATY; Zheng, Y; Zhang, Y; , Angelopoulos; Parks, GK; Mozer, FS; Reme, H; Kistler, LM; Dunlop, MW; Gustafsson, Georg; , others;

Published by: Published on:

YEAR: 2007 DOI:

The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003

Becker-Guedes, F; Sahai, Y; Fagundes, PR; Espinoza, ES; Pillat, VG; Lima, WLC; Basu, Su; Basu, Sa; Otsuka, Y; Shiokawa, K; MacKenzie, E.; Bittencourt, J.;

Published by: Published on:

YEAR: 2007 DOI:

The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003

Becker-Guedes, F; Sahai, Y; Fagundes, PR; Espinoza, ES; Pillat, VG; Lima, WLC; Basu, Su; Basu, Sa; Otsuka, Y; Shiokawa, K; MacKenzie, E.; Bittencourt, J.;

Published by: Published on:

YEAR: 2007 DOI:

2006

Equatorial anomaly development mapped by TIMED/GUVI: Occurrence/suppression of scintillations at low latitudes and their modeling

Basu, S; Basu, S; Makela, J; Miller, E; Dasgupta, A; Roy, S; Huba, J; Groves, K; Rich, F;

Published by: Eos Trans. AGU Published on:

YEAR: 2006 DOI:

Structure and dynamics of a new class of thin current sheets

Sitnov, MI; Swisdak, M; Guzdar, PN; Runov, A;

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

YEAR: 2006 DOI:

Comparison of the Equatorial Anomaly Development Mapped by TIMED/GUVI and Occurrence of Scintillations at low Latitudes

Basu, S; Makela, J; Miller, E; Dasgupta, AK; Ray, S; Groves, K; Rich, FJ;

Published by: Published on:

YEAR: 2006 DOI:

A comparative study of the ionospheric F-region observations in the Brazilian low latitude region and the TIMEGCM model results during the super geomagnetic storm of 20 November 2003

Becker-Guedes, F; Sahai, Y; Fagundes, P; Crowley, G; Lima, W;

Published by: Published on:

YEAR: 2006 DOI:

A comparative study of the ionospheric F-region observations in the Brazilian low latitude region and the TIMEGCM model results during the super geomagnetic storm of 20 November 2003

Becker-Guedes, F; Sahai, Y; Fagundes, P; Crowley, G; Lima, W;

Published by: Published on:

YEAR: 2006 DOI:

Cluster observation of plasma flow reversal in the magnetotail during a substorm

Lui, ATY; Zheng, Y; Zhang, Y; Livi, S; Reme, H; Dunlop, MW; Gustafsson, Georg; Mende, SB; Mouikis, C; Kistler, LM;

Published by: Published on:

YEAR: 2006 DOI:

2005

Method for characterization of the equatorial anomaly using image subspace analysis of Global Ultraviolet Imager data

Henderson, S.; Swenson, C.; Gunther, J.; Chrsistensen, A.; Paxton, L.;

Published by: Journal of Geophysical Research Published on: Jan-01-2005

YEAR: 2005 DOI: 10.1029/2004JA010830

The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event

Some of the most intense solar flares measured in 0.1 to 0.8 nm x-rays in recent history occurred near the end of 2003. The Nov 4 event is the largest in the NOAA records (X28) and the Oct 28 flare was the fourth most intense (X17). The Oct 29 flare was class X7. These flares are compared and contrasted to the July 14, 2000 Bastille Day (X10) event using the SOHO SEM 26.0 to 34.0 nm EUV and TIMED SEE 0.1\textendash194 nm data. High time resolution, \~30s ground-base GPS data and the GUVI FUV dayglow data are used to examine the flare-ionosphere relationship. In the 26.0 to 34.0 nm wavelength range, the Oct 28 flare is found to have a peak intensity greater than twice that of the Nov 4 flare, indicating strong spectral variability from flare-to-flare. Solar absorption of the EUV portion of the Nov 4 limb event is a possible cause. The dayside ionosphere responds dramatically (\~2.5 min 1/e rise time) to the x-ray and EUV input by an abrupt increase in total electron content (TEC). The Oct 28 TEC ionospheric peak enhancement at the subsolar point is \~25 TECU (25 \texttimes 10¹² electrons/cm²) or 30\% above background. In comparison, the Nov 4, Oct 29 and the Bastille Day events have \~5\textendash7 TECU peak enhancements above background. The Oct 28 TEC enhancement lasts \~3 hrs, far longer than the flare duration. This latter ionospheric feature is consistent with increased electron production in the middle altitude ionosphere, where recombination rates are low. It is the EUV portion of the flare spectrum that is responsible for photoionization of this region. Further modeling will be necessary to fully understand the detailed physics and chemistry of flare-ionosphere coupling.

Tsurutani, B.; Judge, D.; Guarnieri, F.; Gangopadhyay, P.; Jones, A.; Nuttall, J.; Zambon, G.A.; Didkovsky, L.; Mannucci, A.J.; Iijima, B.; Meier, R.; Immel, T.J.; Woods, T.; Prasad, S.; Floyd, L.; Huba, J.; Solomon, S.; Straus, P.; Viereck, R.;