Assimilative Modeling of Ionospheric Disturbances with FORMOSAT-3/COSMIC and Ground-Based GPS Measurements

Abstract

AB STRACTThe four-di men sional Global Assimilative Ion o spheric Model (GAIM) is ap plied to a study of ion o spheric dis tur bances. The in ves ti ga tion is fo cused on dis tur bance fea tures, par tic u larly in the al ti tude and lat i tude di men sions, at low lat i tudes dur ing a geo mag netic storm on 7 Au gust 2006, un der so lar min i mum con di tions. The mod el ing of storm-time ion o spheric state (elec tron den sity) is con ducted by as sim i lat ing an un prec e dented vol ume of line-of-sight TEC data col lected by the Global Po si tion ing Sys tem (GPS) occultation re ceiv ers on board six FORMOSAT-3/COS MIC sat el lites and geo detic-qual ity GPS re ceiv ers at two hun dred glob ally-dis trib uted ground track ing sta tions. With a band-lim ited Kalman fil ter tech nique to up date the ion o spheric state, the assimilative mod el ing re veals a pro nounced en hance ment in the equa to rial anom aly in the East Asia sec tor dur ing dusk and eve ning hours. The dis tur bance char ac ter is tics, ob tained by com par ing with the quiet con di tions prior to the storm also mod eled in this study through data as sim i la tion, in clude lifted F layer and re duced elec tron den sity in the equa to rial re gion, en hanced den sity at the mag net i cally con ju gate anom aly lat i tudes, and tilted fea ture of den sity in crease to wards higher al ti tudes at lower lat i tudes. The char ac ter is tics are at trib uted to the en hanced plasma foun tain ef fect driven by an en hanced east ward zonal elec tric field. These re sults en able us to dis tin guish the storm-time elec tric field per tur ba tions clearly from other sources dur ing the storm. The pos si ble origins of electric field perturbations are also discussed, including penetration of the magnetospheric electric field and wind dynamo disturbances. Ocean. Sci., 20, 273-285, doi: 10.3319/TAO.2008.01.04.01(F3C) IN TRO DUC TIONThe re cent de vel op ment of assimilative ion o spheric mod els marks a tran si tion from first-prin ci ples or for ward mod el ing to a new ca pa bil ity for spec i fy ing the Earth's ion ospheric weather. A fun da men tal dif fi culty of the for ward mod el ing ap proach is the spec i fi ca tions of the weather condi tions of re quired model driv ers, in clud ing the so lar EUV ra di a tion spec trum, elec tric field in the up per at mo sphere that drives plasma con vec tion, thermospheric com po si tion and wind, and charged par ti cle pre cip i ta tion. In tra di tional mod el ing prac tice these driv ers are pro vided ei ther by es timates ob tained from em pir i cal mod els that char ac ter ize statis ti cal pat terns, or from the first prin ci ples phys ics-based mod els. The re sults of such mod el ing ap proaches of ten deviate from the weather con di tions due to the sig nif i cant variabil ity of the driv ers. Assimilative mod els in cor po rate the first-prin ci ples mod els and op ti mi za tion mod ules, al low ing as sim i la tion of mea sure ments into the for ward mod els and help ing to bring the m...

Detecting ionospheric TEC perturbations caused by natural hazards using a global network of GPS receivers: The Tohoku case study

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Statistical characterization of ionosphere anomalies and their relationship to space weather events

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Sibsonian and non-Sibsonian natural neighbour interpolation of the total electron content value

“…Other ionospheric modelling methods are data-assimilative models (GAIM, at the Jet Propulsion LaboratorySchunk 2002; Pi et al 2003Pi et al , 2004Pi et al , 2009Mandrake et al 2005;Scherliess et al 2006;Komjathy et al 2010), harmonic spherical functions (Schaer 1999;Choi et al 2010;Han et al 2013) and empirical models (e.g., the International Reference Ionosphere project-IRI, http://iri.gsfc.nasa.gov/) (Strangeways 2009;Buresova et al 2009). …”