Global thermosphere-ionosphere response to onset of 20 November 2003 magnetic storm (original) (raw)
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Journal of Geophysical Research, 2008
1] We have investigated the thermospheric and ionospheric response to the 14-15 December 2006 geomagnetic storm using a Coupled Magnetosphere Ionosphere Thermosphere (CMIT) 2.0 model simulation. In this paper we focus on observations and simulations during the initial phase of the storm (about 8 h), when the shock was driving changes in geospace. The global ionospheric maps of total electron content (TEC), ionosonde data at four stations and Millstone Hill incoherent scatter radar (ISR) observations are compared with the corresponding simulation results from the CMIT model. The observations showed significant positive storm effects occurred in the Atlantic sector after the onset of this storm. The CMIT model is able to capture the temporal and spatial variations of the ionospheric storm effects seen in the GPS TEC observations, although the model slightly underestimates the daytime positive ionospheric storm in the South American sector. The simulations are also in agreement with the ionosonde and ISR ionospheric measurements. Term analysis of the ion continuity equation demonstrates that changes in the electric fields play a dominant role in generating the observed ionospheric positive storm effect in the American sector during the initial phase, although neutral winds and composition changes also contribute. The difference in the strength of the enhancements over North and South America can be explained by the slope of the topside electron density profiles in the two hemispheres. In the southern hemisphere electron densities decrease slowly with altitude, whereas the decrease is much more rapid in the northern (winter) hemisphere. The electric fields, therefore, cannot cause large increases in electron density by uplifting the plasma, so positive storm effects are small in the southern hemisphere compared with the northern hemisphere, even though the increase in h m F 2 is greater in the southern hemisphere. Nighttime changes in electron density in other longitude sectors are small, because the topside electron densities also decrease slowly with altitude at night.
Journal of applied science and environmental management, 2024
Ionospheric modelling is a major approach to predicting the behavior of the ionosphere particularly in regions where Global Positioning Systems (GPS) are not readily available. Hence, the objective of this paper is to measure and compare Total Electron Content (TEC) for Assessment of Ionospheric Models during April 7, 2000 Geomagnetic Storms. Measured Total Electron Content (TEC) from experimental records (April 5-9, 2000) were compared with those predicted by the improved versions of the International Reference Ionosphere (IRI-2012 and IRI-Plas2015) and the NeQuick models. The mean values of TEC in five days of the months were plotted against the hours of the same day and the root mean square error of the models which shows their deviations from the GPS data were used to observe the diurnal variations in TEC and the performances of the ionospheric models respectively. The data obtained confirmed that TEC has their highest values during the midnight period and lowest values during the sunset period at the Australian stations and we also confirmed that European stations had their highest TEC values during the daytime and their lowest values during the night time. We affirmed that the North American station in USA had its highest TEC values during the night time and lowest values during day time. The Asian station had its highest TEC values during the day time and lowest values during the midnight period. However, NeQuick, IRIPlas2015, and NeQ-IRI produced better estimate of TEC than the IRI-2001 and IRI-2001COR at all locations during the phases of the geomagnetic storm.
Response of the low- to mid-latitude ionosphere to the geomagnetic storm of September 2017
Annales Geophysicae
We study the impact of the geomagnetic storm of 7-9 September 2017 on the low-to mid-latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of two SYM-H minima with values of − 146 and −115 nT on 8 September at 01:08 and 13:56 UT, respectively. The study is based on the analysis of data from the Global Positioning System (GPS) stations and magnetic observatories located at different longitudinal sectors corresponding to the Pacific, Asia, Africa and the Americas during the period 4-14 September 2017. The GPS data are used to derive the global, regional and vertical total electron content (vTEC) in the four selected regions. It is observed that the storm-time response of the vTEC over the Asian and Pacific sectors is earlier than over the African and American sectors. Magnetic observatory data are used to illustrate the variation in the magnetic field particularly, in its horizontal component. The global thermospheric neutral density ratio; i.e., O/N 2 maps obtained from the Global UltraViolet Spectrographic Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to characterize the storm-time response of the thermosphere. These maps exhibit a significant stormtime depletion of the O/N 2 density ratio in the northern middle and lower latitudes over the western Pacific and American sectors as compared to the eastern Pacific, Asian and African sectors. However, the positive storm effects in the O/N 2 ratio can be observed in the low latitudes and equatorial regions. It can be deduced that the storm-time thermospheric and ionospheric responses are correlated. Overall, the positive ionospheric storm effects appear over the dayside sectors which are associated with the ionospheric electric fields and the traveling atmospheric disturbances. It is inferred that a variety of space weather phenomena such as the coronal mass ejection, the high-speed solar wind stream and the solar radio flux are the cause of multiple day enhancements of the vTEC in the low-to mid-latitude ionosphere during the period 4
Study of the March 31, 2001 magnetic storm effects on the ionosphere using GPS data
Advances in Space Research, 2005
Despite the fact that much has been learned about the Sun-Earth relationship during disturbed conditions, understanding the effects of magnetic storms on the neutral and ionized upper atmosphere is still one of the most challenging topics remaining in the physics of this atmospheric region. In order to investigate the magnetospheric and ionospheric-thermospheric coupling processes, many researchers are taking advantage of the dispersive nature of the ionosphere to compute total electron content (TEC) from Global Positioning System (GPS) dual-frequency data. Even though there are currently a large number of GPS receivers in continuous operation, they are unevenly distributed for ionosphere study purposes, being situated mostly in the Northern Hemisphere. The relatively smaller number of GPS receivers located in the Southern Hemisphere and, consequently, the reduced number of available TEC measurements, cause ionospheric modelling to be less accurate in this region. In the work discussed in this paper, the University of New Brunswick Ionospheric Modelling Technique (UNB-IMT) has been used to describe the local time and geomagnetic latitude dependence of the TEC during the March 31, 2001 magnetic storm with an emphasis on the effects in the Southern Hemisphere. Data collected from several GPS networks worldwide, including the Brazilian Network for Continuous Monitoring, have been used along with ionosonde measurements to investigate the global ionospheric response to this severe storm. Data analysis revealed interesting ionospheric effects, which are shown to be dependent on the local time at the storm commencement and the magnetic conditions previous to and during the storm period. The southward turning of the interplanetary magnetic field during the recovery phase of the storm began a process of substorm activity and development and intensification of electrojet activity over broad regions. Observed effects on the ionosphere during that storm are analysed and the mechanisms that gave rise to the ionospheric behaviour are discussed.
Response of low to mid latitude ionosphere to the Geomagnetic storm of September 2017
Annales Geophysicae Discussions
We study the impact of geomagnetic storm of September 6-9, 2017 on the low-to-mid latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of the two Dst minima of maximum negative values −148nT and −122nT on September 8 at 2UT and 15UT , respectively. The study is based on analyzing the data from GPS stations and the magnetometer observatories located at different longitudinal sectors such as Asia, Africa and America. The GPS data is used to derive the global, regional and vertical total electron content (TEC) in the selected regions. The data of the magnetic observatories is used to illustrate the variation in the magnetic field particularly, the horizontal component of the magnetic field. It is observed that the storm time response of the TEC over the pre-noon sector (Asia) is earlier than Africa and America. The global thermospheric composition maps by Global Ultraviolet Imager exhibits a storm time variation in the O/N 2 ratio. The positive storm effects in the vertical TEC and in the O/N 2 ratio occur in the low latitudes/ equatorial regions. Copyright statement. 1 Introduction It is well known fact that the geomagnetic storm is a temporary variation of the Earth's magnetic field induced by the interplanetary shocks or the high speed solar wind stream (HSSWS). In the modern space era, the strength of the geomagnetic storm is characterized by the minimum Dst (Disturbance-storm time) index and the B z component of the interplanetary magnetic field (Gonzalez et al. (1994)). On the basis of these parameters the geomagnetic storms can be categorized as: the Small Storm (Dst ≤ −30nT , B z ≤ −3nT), the moderate storms (Dst ≤ −50nT , B z ≤ −5nT), the intense storm (Dst ≤ −100nT , B z ≤ −10nT) and the great storm (Dst ≤ −200nT) (Tsurutani et al. (1992); Loewe and Prolss (1997)). The ionosphere features vary along the latitudes and longitudes due to different current systems flowing in the magnetosphere. Therefore, the effects of geomagnetic storms are non uniform in different regions of the magnetosphere. A number of studies have been devoted to investigate the storm effects in different longitudinal and latitudinal sectors. Sharma et al. (2011) investigated the low latitude ionosphere TEC response to the geomagnetic storm of August 25, 2005. On the day of storm, a doubly humped peak in the TEC is observed which is almost two times higher than that of the quiet day value. The first peak is
Ionospheric and thermospheric response to the 27–28 February 2014 geomagnetic storm
The present work explores the ionospheric and thermospheric responses to the 27-28 February 2014 geomagnetic storm. For the first time, a geomagnetic storm is explored in north Africa using interferometer, all-sky imager and GPS data. This storm was caused by coronal mass ejection (CME) associated flares that occurred on 25 February 2014. A Fabry-Perot interferometer located at the Oukaimeden Observatory (31.206 • N, 7.866 • W, 22.84 • N magnetic) in Morocco provides measurements of the thermospheric neutral winds based on the observations of the 630 nm redline emission. A wide angle imaging system records images of the 630-nm emission. The effects of this geomagnetic storm on the thermosphere are evident from the clear departure of the neutral winds from their seasonal behavior. During the storm, the winds experience an intense and steep equatorward flow from 21 to 01 LT and a westward flow from 22 to 03 LT. The equatorial wind speed reaches a maximum of 120 m/s for the meridional component at 22 LT, when the zonal wind reverses to the westward direction. Shortly after 00 LT a maximum westward speed of 80 m/s was achieved for the zonal component of the wind. The features of the winds are typical of TAD (Traveling Atmospheric Disturbances) induced circulation; the first TAD coming from the northern hemisphere reaches the site at 21 LT and a second one coming from the southern hemisphere reaches the site at about 00 LT. We estimate the propagation speed of the northern TAD to be 550 m/s. We compared the winds to DWM07 (Disturbance Wind Model) prediction model and find that this model gives a good indication of the new circulation pattern caused by storm activity, but deviates largely inside the TADs. The effects on the ionosphere were also evident through the change observed in the background electrodynamics from the reversal in drift direction in an observed equatorial plasma bubble. TEC measurements of a GPS station installed in Morocco, at Rabat (33.998 • N; 6.853 • W, geographic) revealed a positive storm. 1 Introduction The sun is the energy provider of our planet through electromagnetic radiations, solar wind, and interplanetary magnetic field. It is a highly variable star with sporadic events consisting of outbursts of huge amounts of energy. Solar flares are an impulsive release of a large amount of radiant energy that change in a very small time scale the physical properties of the ionosphere 1
2020
This study focused on the effects of space weather on the ionosphere during geomagnetic storms for the period 17 - 28 February, 2014 over the African low latitude region. During this period, a series of in- terplanetary shocks successively hit the Earth’s magnetosphere, leading to geomagnetic storms. The dual frequency Global Positioning System (GPS) data was analysed to obtain Total Electron Content (TEC) and this was used to study the response of the ionosphere to the geomagnetic storms. Positive and negative ionospheric storm effects were observed during the period of study. These storm effects were discussed in terms of the Prompt Penetration Electric Field (PPEF), storm induced wind-lifting effect, and Disturbance Dynamo (DD) electric field. Although these storms occurred during the same period and were all driven by Coronal Mass Ejections (CMEs), their impacts and associated features on the ionosphere varied due to different contributing factors to their driving mechanisms. In...
Ionosphere-thermosphere global time response to geomagnetic storms
2017
In this study, we investigate thermospheric neutral mass density heating associated with 168 CME-driven geomagnetic storms in the period of May 2001 to September 2011. We use neutral density measured by two low-Earth orbit satellites: CHAMP and GRACE. For each storm, we superpose geomagnetic and density data for the time when the IMF B$_\mathrm{z}$ component turns sharply southward chosen as the zero epoch time. This indicates the storm main phase onset. We find that the average SYM-H index reaches the minimum of −-−42 nT near 12 hours after storm main phase onset. The Joule heating is enhanced by approximately 200\% in comparison to quiet values. In respect to thermosphere density, on average, high latitude regions (auroral zones and polar caps) of both hemispheres are highly heated in the first 1.5 hour of the storm. The equatorial response is presumably associated with direct equator-ward propagation of TADs (traveling atmospheric disturbances). A slight north-south asymmetry in ...
Thermospheric composition changes deduced from geomagnetic storm modeling
Geophysical Research Letters, 1999
To test various hypotheses about positive ionospheric storm development, we numerically simulated the magnetic storm of 24-27 January 1974 to obtain the global pattern of its thermospheric and ionospheric effects. We use a global self-consistent numerical model of the thermosphere-ionosphere-magnetosphere system which calculates all plasma parameters as well as electric fields both of magnetospheric and thermospheric dynamo origin. The predicted neutral composition changes are consistent with observations of the AE-C and ESRO-4 satellites. The stormto-quiet density ratio of [O]/[N2] (at a fixed height) does not change significantly at middle and low latitudes while the absolute density of all neutral constituents is enhanced. The density ratio at a fixed pressure level can be slightly enhanced under certain conditions. Positive ionospheric storm effects during the main phase of the storm are shown to be mainly due to the uplifting of the ions along the field lines by an equatorward directed disturbance wind component at middle latitudes and their equatorward (convergent) movement at low latitudes. This is driven by the passage of travelling atmospheric disturbances and by the large-scale disturbance wind circulation. Under daylight conditions minor contributions arise from the general thermal density enhancement of all constituents favoring positive ionospheric response due to a stronger ion production rather than loss. Height dependent deviations from diffusive equilibrium of minor thermospheric constituents are due to the relatively rapid (in comparison with their diffusion) vertical bulk motion.
Journal of Geophysical Research: Space Physics
By using data from multiple instruments, we investigate ionospheric/thermospheric behavior during the period from 21 to 23 June 2015, when three interplanetary shocks (IS) of different intensities arrived at Earth. The first IS was registered at 16:45 UT on 21 June and caused~50 nT increase in the SYM-H index. The second IS arrived at 5:45 UT on 22 June and induced an enhancement of the auroral/substorm activity that led to rapid increase of thermospheric neutral mass density and ionospheric vertical total electron content at high latitudes. Several hours later, topside electron content and electron density increased at low latitudes on the nightside. The third and much larger IS arrived at 18:30 UT on 22 June and initiated a major geomagnetic storm that lasted for many hours. The storm provoked significant effects in the thermosphere and ionosphere on both dayside and nightside. In the thermosphere, the dayside neutral mass density exceeded the quiet time levels by 300-500%, with stronger effects in the summer hemisphere. In the ionosphere, both positive and negative storm effects were observed on both dayside and nightside. We compared the ionospheric observations with simulations by the coupled Sami3 is Also a Model of the Ionosphere/Rice Convection Model (SAMI3/RCM) model. We find rather good agreement between the data and the model for the first phase of the storm, when the prompt penetration electric field (PPEF) was the principal driver. At the end of the storm main phase, when the ionospheric effects were, most likely, driven by a combination of PPEF and thermospheric winds, the modeling results agree less with the observations. Recent development of networks of ground-based instruments and launch of new satellite missions allowed to reveal new aspects of the development of ionospheric and thermospheric storms with unprecedented details (e.g.,