[1] The Global Ultraviolet Imager (GUVI) instrument carried aboard the NASA TIMED satellite measures spectral radiance of Earth's far ultraviolet airglow in region from 120 to 180 nm using a cross-track scanning spectrometer design. Continuous operation provides images disk and limb five selectable bands. Also, spectra at fixed mirror position can be obtained. Initial results demonstrate quantitative functionality for studies dayglow, aurora, ionosphere. Moreover, through forward modeling,...

We analyzed measurements of ion number density made by the retarding potential analyzer aboard Atmosphere Explorer‐E (AE‐E) satellite, which was in an approximately circular orbit at altitude near 300 km 1977 and later 400 km. Large‐scale (>60 km) high‐altitude regions show large depletions bubble‐like structures are confined to narrow local time, longitude, magnetic latitude ranges, while those low‐altitude relatively small broadly distributed space. For this reason we considered below...

We present a new gap‐free version of the seasonal and longitudinal (s/l) variations P EFI , equatorial F region irregularity (EFI) occurrence probability, based on data from AE‐E spacecraft. The agreement this three earlier partial patterns verifies all four. reinterpret another gap‐ridden pattern, that topside ionogram index average darkening by range spread . comparent with and, using ionosonde radio science considerations, we conclude = times factor depending number plasma bubbles visible...

We investigate the longitudinal distribution of vertical E × B drift velocity and ion density in low‐latitude ionosphere using first Republic China Satellite (ROCSAT‐1) data acquired during 1999–2004. The ROCSAT‐1 observations daytime demonstrate presence longitudinally periodic patterns plasma on topside F region (600 km). four longitude sectors where peaks are found coincident with drift. This observation may indicate association large‐scale structure ‐region dynamo electric field. exists...

Abstract The Global Ultraviolet Imager (GUVI) onboard the Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics (TIMED) satellite senses far ultraviolet emissions from O N 2 in thermosphere. Transformation of radiances measured on Earth limb into O, , number densities temperature quantifies these responses demonstrates value simultaneous altitude geographic information. Composition variations are available 2002 to 2007. This paper documents extraction data products emission rates. We...

[1] Thermospheric O/N2 column density ratios referenced at a N2 of 1017 cm−2 are obtained using the IMAGE SI-13 and TIMED/GUVI far-ultraviolet (FUV) dayglow data, AURIC simulation results, MSIS86 model. Each magnetic storms occurring during 4-day period (1–4 October 2002) caused significant depletion that was detected by both GUVI instruments. The extended down to latitudes 10° −5° in Northern Southern Hemispheres, respectively. Simultaneous measurements show an excellent agreement between...

The effect of equatorial ionospheric scintillations on the operation GPS receivers is investigated, with special attention given to scintillation timescales code division multiple access (CDMA) protocol used by GPS. We begin examining fades modeled as a horizontally drifting pattern whose are determined Fresnel length and drift speed. model tested comparing speed, dividing autocorrelation time (width), speed estimated using spaced receivers, two independent estimates shown possess linear...

The occurrence statistics of equatorial plasma bubbles (EPBs) obtained from low‐inclination orbit satellites are significantly affected by the way data sampled and that EPBs counted. To resolve discrepancy between EPB frequency determined ground‐based observations in situ sampling density spacecraft, we have developed a new detection method minimizes dependence rate on processing method. global distribution maps created analyzing measurements ion first Republic China satellite (ROCSAT‐1)...

We investigate the seasonal, longitudinal, local time (LT), and altitudinal variations of F region morphology at low latitudes using data from first Republic China satellite (ROCSAT‐1), Global Ultraviolet Imager (GUVI), on board Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, Defense Meteorological Satellite Program (DMSP) F13 F15 satellites. Signatures longitudinally periodic plasma density structure emerge before 0900 LT. The wave is established noon further...

An accurate description of the irregularity region defined by a plasma bubble is critically important in understanding dynamics and its effects on radio scintillation. Here we describe depletion as “depletion shell” show how two‐dimensional optical images from space can be used to define shape shell. Our simple model calculation demonstrates that space‐based observation detect plasma‐depleted magnetic flux tubes only near F ‐peak height. The backward C‐shape observations trace shell westward...

Abstract The far ultraviolet (FUV) spectral range (from about 115 nm to 180 nm) is one of the most useful regions for characterizing upper atmosphere (thermosphere and ionosphere). principal advantages are that there FUV signatures major constituents as well high‐latitude energy inputs. Because absorption by thermospheric O 2 , seen against a “black” background, i.e., not affected ground albedo or clouds and, consequence, can make observations aurora during day when Moon above horizon. In...

Abstract This study reports different properties of ionospheric perturbations detected to the west and south Korean Peninsula after Hunga‐Tonga volcanic eruption on 15 January 2022. Transient wave‐like total electron content (TEC) modulations intense irregular TEC are in Peninsula, respectively, about 8 hr eruption. The propagate away from epicenter with a speed 302 m/s. Their occurrence time, propagation direction velocity, alignment surface air pressure indicate generation by Lamb waves...

Operational sensors are designed and intended to reliably produce the measurements needed develop high-value key environmental parameters. The Special Sensor Ultraviolet Spectrographic Imager (SSUSI) is slated fly on next five Defense Meteorological Satellite Program launches (beginning with launch of F16 in Fall 2001). SSUSI will routinely maps ionospheric upper atmospheric composition image aurora. In this paper we describe these products our validation plans process through which can...

We report on ionospheric optical emissions detected by the GUVI instrument TIMED satellite. As satellite crosses equatorial zone bright Appleton Anomaly region is imaged. Often these zones are interrupted regions slanted from west to east as equator approached forming a backwards ‘C’‐shape in image. To explain this feature we use simultaneous ground‐based observations looking equatorward Hawaii using 777.4‐nm emission. also compare inverted electron density maps, well those made radar and...

The measurements of vertical ion velocity from the first Republic China satellite (ROCSAT‐1) provide a unique database for development an annually and longitudinally high‐resolution plasma drift model in equatorial ionosphere. Currently, ROCSAT‐1‐based empirical models are available three seasons: equinox solstices. However, patterns not precisely divided by seasons. A monthly with high longitudinal resolution is desirable to accurately low‐latitude ionosphere identify coupling between...

We investigate the annual and local time variations of wave‐4 structures in plasma density vertical drift low‐latitude F region by analyzing measurements from first Republic China satellite (ROCSAT‐1) conducting simulations with Global Ionosphere Plasmasphere (GIP) model. The GIP model uses apex magnetic coordinates International Geomagnetic Reference Field (IGRF) for field, neutral wind HWM‐07, thermospheric parameters NRLMSISE‐00 In order to understand how drifts relate longitudinal...

KASI has been developing LEO satellite observation missions to study the Earth's ionosphere and upper atmosphere. These include SNIPE (Small scale magNetospheric Ionospheric Plasma Experiment), SNIPE-2 Experiment-2), ROKITS (Republic Of Korea Imaging Test System), ATHENA (Aurora THErmosphere ioNosphere for spAceweather). The successful launch of Experiment) mission in May 2023, featuring a formation flight three nanosatellites, enables simultaneous spatio-temporal changes plasma...

The Global Ultraviolet Imager (GUVI) is an imaging spectrometer on the NASA TIMED spacecraft which was launched December 7, 2001. This instrument produces a far ultraviolet (FUV) data cube of spatial and spectral information at each step scan mirror - that covers 140 deg in cross track direction span includes limb. GUVI simultaneous monochromatic images five "colors" (121.6 nm, 130.4 135.6 broader bands 140-150 nm 165-180 nm) as its field view scanned from horizon to horizon. consists...

[1] The winter anomaly (or seasonal anomaly) at middle latitudes is a phenomenon during which the daytime plasma density F-peak height (NmF2) greater in than summer. Radio occultation measurements from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites provide new data source study of on global scale. In this we investigate altitude, local time, latitude, longitude, hemispheric variations electron middle-latitude ionosphere by analyzing COSMIC...

Ionospheric irregularities and their zonal apparent drift were studied using Global Positioning System (GPS) measurements at Cachoeira Paulista (22.41°S, 45.00°W, −26° dip angle) in Brazil during November 6–19, 1998. Radio scintillations the GPS L1 frequency (1.575 GHz) monitored four receivers spaced geomagnetically east–west north–south. Total electron content (TEC) was measured through ionospheric advance of L2 (1.227 phases. Strong amplitude coincided with TEC fluctuations associated...

Latitudinal variations of scintillation activity and zonal plasma drifts were investigated simultaneously at three locations in Brazil during 23 November to 26 December 1999 using Global Positioning System measurements. The morphology 1.575 GHz showed large latitudinal differences activity. At the magnetic equator occurrence probability was very low without showing strong ( S 4 > 0.5) solar maximum period, whereas observed most days equatorial ionization anomaly (EIA). mostly limited...