scholarly journals Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

2000 ◽  
Vol 18 (4) ◽  
pp. 461-477 ◽  
Author(s):  
A. A. Namgaladze ◽  
M. Förster ◽  
R. Y. Yurik
Keyword(s):  
Numerical Model ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Atmospheric Composition ◽  
Reference Level ◽  
Quiet Time ◽  
Ionospheric Storm ◽  
Low Latitudes ◽  
Composition Changes

Abstract. Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions.Key words: Atmospheric composition and structure (thermosphere · composition and chemistry) · Ionosphere (ionosphere · atmosphere interactions; modelling and forecasting)

scholarly journals Total electron content responses to HILDCAAs and geomagnetic storms over South America

2017 ◽  
Vol 35 (6) ◽  
pp. 1309-1326 ◽  
Author(s):  
Patricia Mara de Siqueira Negreti ◽  
Eurico Rodrigues de Paula ◽  
Claudia Maria Nicoli Candido
Keyword(s):  
Solar Wind ◽  
South America ◽  
Total Electron Content ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Time Variability ◽  
Electron Content ◽  
Quiet Time ◽  
Total Electron

Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of storm-time TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O ∕ N2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from  ∼  25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

scholarly journals Role of neutral wind and storm time electric fields inferred from the storm time ionization distribution at low latitudes: in-situ measurements by Indian satellite SROSS-C2

2005 ◽  
Vol 23 (10) ◽  
pp. 3289-3299 ◽  
Author(s):  
P. Subrahmanyam ◽  
A. R. Jain ◽  
L. Singh ◽  
S. C. Garg
Keyword(s):  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Activity Period ◽  
High Solar Activity ◽  
Satellite Network ◽  
Neutral Winds ◽  
Weather Events ◽  
Low Latitudes ◽  
Time Changes

Abstract. Recently, there has been a renewal of interest in the study of the effects of solar weather events on the ionization redistribution and irregularity generation. The observed changes at low and equatorial latitudes are rather complex and are noted to be a function of location, the time of the storm onset and its intensity, and various other characteristics of the geomagnetic storms triggered by solar weather events. At these latitudes, the effects of geomagnetic storms are basically due to (a) direct penetration of the magnetospheric electric fields to low latitudes, (b) development of disturbance dynamo, (c) changes in atmospheric neutral winds at ionospheric level and (d) changes in neutral composition triggered by the storm time atmospheric heating. In the present study an attempt is made to further understand some of the observed storm time effects in terms of storm time changes in zonal electric fields and meridional neutral winds. For this purpose, observations made by the Retarding Potential Analyzer (RPA) payload on board the Indian satellite SROSS-C2 are examined for four prominent geomagnetic storm events that occurred during the high solar activity period of 1997-2000. Available simultaneous observations, from the GPS satellite network, are also used. The daytime passes of SROSS-C2 have been selected to examine the redistribution of ionization in the equatorial ionization anomaly (EIA) region. In general, EIA is observed to be weakened 12-24 h after the main phase onset (MPO) of the storm. The storm time behaviour inferred by SROSS-C2 and the GPS satellite network during the geomagnetic storm of 13 November 1998, for which simultaneous observations are available, is found to be consistent. Storm time changes in the delay of received GPS signals are noted to be ~1-3 m, which is a significant component of the total delay observed on a quiet day. An attempt is made to identify and delineate the effects of a) meridional neutral winds, b) the development of the ring currents and c) the disturbance dynamo electric fields on the low latitude ionization distribution. The weakening of the EIA is noted to be primarily due to the decrease in the eastward electric fields driving the equatorial fountain during the daytime. The meridional neutral winds are also noted to play an important role in redistribution of ionization in the EIA region. The present results demonstrate that storm time latitudinal distribution of ionization in this region can be better understood by taking into account the meridional winds in addition to E×B drifts.

scholarly journals Pre-storm <I>Nm</I>F2 enhancements at middle latitudes: delusion or reality?

2009 ◽  
Vol 27 (3) ◽  
pp. 1321-1330 ◽  
Author(s):  
A. V. Mikhailov ◽  
L. Perrone
Keyword(s):  
Magnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Activity ◽  
Critical Analysis ◽  
Geomagnetic Storms ◽  
Activity Level ◽  
Quiet Time ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Plasma Ring

Abstract. A critical analysis of recent publications devoted to the NmF2 pre-storm enhancements is performed. There are no convincing arguments that the observed cases of NmF2 enhancements at middle and sub-auroral latitudes bear a relation to the following magnetic storms. In all cases considered the NmF2 pre-storm enhancements were due to previous geomagnetic storms, moderate auroral activity or they presented the class of positive quiet time events (Q-disturbances). Therefore, it is possible to conclude that there is no such an effect as the pre-storm NmF2 enhancement as a phenomenon inalienably related to the following magnetic storm. The observed nighttime NmF2 enhancements at sub-auroral latitudes may result from plasma transfer from the plasma ring area by meridional thermospheric wind. Enhanced plasmaspheric fluxes into the nighttime F2-region resulted from westward substorm-associated electric fields is another possible source of nighttime NmF2 enhancements. Daytime positive Q-disturbances occurring under very low geomagnetic activity level may be related to the dayside cusp activity.

Global estimation of ionospheric drivers during extreme storms

2021 ◽  
Author(s):  
Aurora Lopez Rubio ◽  
Seebany Datta-Barua ◽  
Gary Bust
Keyword(s):  
Kalman Filter ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Spherical Harmonics ◽  
Space Weather ◽  
Basis Function ◽  
Geomagnetic Storms ◽  
Vector Spherical Harmonics ◽  
Neutral Winds ◽  
Global Estimation

&lt;p&gt;During geomagnetic storms, the space environment can be drastically altered as the plasma in the upper atmosphere, or ionosphere, moves globally. This plasma redistribution is mainly caused by storm-time electric fields, but another important driver of the velocity of the ions in the plasma is the neutral winds. These winds refer to the movement of the neutral particles that are part of the thermospheric layer of the atmosphere, that can drag the plasma. Geomagnetic storms increase the neutral winds, due to the heating of the thermosphere that comes from the storm. In this study we want to understand how these ionospheric drivers affect the ionosphere behavior because, among other reasons, during geomagnetic storms the plasma can refract and diffract trans-ionospheric signals and, consequently, can cause problems in the navigation systems such as GNSS (Global Navigation Satellite System)/GPS (Global Positioning System) that use the information from the signals.&lt;/p&gt;&lt;p&gt;In this work, our objective is to estimate the electric fields and neutral winds globally during a geomagnetic storm. Global GNSS TEC (total electron content) measurements are ingested by the Ionospheric Data Assimilation 4-Dimensional (IDA4D) algorithm [1], whose output is the electron density rate over a grid at different time steps during a geomagnetic storm. The density rates are treated as &amp;#8220;observations&amp;#8221; in EMPIRE (Estimating Model Parameters from Ionospheric Reverse Engineering), which is a data assimilation algorithm based on the plasma continuity equation [2,3,4]. Then, the EMPIRE &amp;#8220;observations&amp;#8221; are used to estimate corrections to the electric field and neutral winds by solving a Kalman filter. To study these drivers with EMPIRE, basis functions are used to describe them. For the global potential field, spherical harmonics are used.&lt;/p&gt;&lt;p&gt;To have a global estimation of the neutral winds, we introduce vector spherical harmonics as the basis function for the first time in EMPIRE. The vector spherical harmonics are used to model orthogonal components of neutral wind in the zonal (east-west) and meridional (north-south) directions. EMPIRE&amp;#8217;s Kalman filter needs the error covariance of the vector spherical harmonics decomposition. To calculate it, the basis function is fitted to the model HWM14 (Horizonal Wind Model) values of the neutral winds and the error between the fitting and the model is studied. Later, we study the global potential field and global neutral winds over time to understand how much each driver contributes to the plasma redistribution during the geomagnetic storm on October 25&lt;sup&gt;th&lt;/sup&gt; 2011. We compare the results to FPI (Fabry-Perot Interferometer) neutral winds measurements to validate the results.&amp;#160; &amp;#160;&lt;/p&gt;&lt;p&gt;[1] G.S.Bust, G.Crowley, T.W.Garner, T.L.G.II, R.W.Meggs, C.N.Mitchell, P.S.J.Spencer, P.Yin, and B.Zapfe, Four-dimensional gps imaging of space weather storms, Space Weather, 5 (2007),&amp;#160; doi:10.1029/2006SW000237.&lt;/p&gt;&lt;p&gt;[2] D.S.Miladinovich, S.Datta-Barua, G.S.Bust, and J.J.Makela, Assimilation of thermospheric measurements for ionosphere-thermosphere state estimation, Radio Science, 51 (2016).&lt;/p&gt;&lt;p&gt;[3] D.S.Miladinovich, S.Datta-Barua, A.Lopez, S. Zhang, and G.S.Bust, Assimilation of gnss measurements for estimation of high-latitude convection processes, Space Weather, 18 (2020).&lt;/p&gt;&lt;p&gt;[4] G.S.Bust and S.Datta-Barua, Scientific investigations using ida4d and empire, in Modeling the Ionosphere-Thermosphere System, J. Huba, R. Schunk, and G. Khazanov, eds., John Wiley &amp; Sons, Ltd, 1 ed., 2014.&lt;/p&gt;

Ionospheric dynamic and coupling processes during geomagnetic storms

2020 ◽  
Author(s):  
Chaosong Huang
Keyword(s):  
Electric Fields ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
Ion Composition ◽  
Hemispheric Differences ◽  
Ion Density ◽  
Ion Drift ◽  
Low Latitudes ◽  
Coupling Processes ◽  
Ionospheric Dynamics

&lt;p&gt;Geomagnetic storms cause the largest disturbances in the ionosphere-thermosphere system. We use measurements with satellites and ground based radars to study storm-induced variations in ionospheric plasma drift, ion density, and ion composition at low latitudes. It is found that the storm-time change of ion drift velocity in the equatorial ionosphere can reach 200-300 m/s, the change of ion density can be one or two orders of magnitude, and the change of ion composition can be 50-80%. These extremely large changes in the ionosphere can last for several hours or even a few days during the main and recovery phases of magnetic storms. The longitudinal, latitudinal and hemispheric differences of storm-time ionospheric disturbances are analyzed from measurements of multiple satellites or radar chain. Very long, continuous penetration of interplanetary electric fields to the equatorial ionosphere for 6 or even 14 hours are observed, and the time when disturbance dynamo electric fields become dominant is identified. The interplay of penetration, shielding, and disturbance dynamo electric fields in the storm-time ionosphere will be addressed. Mechanisms responsible for storm-time ionospheric dynamics will be discussed.&lt;/p&gt;

scholarly journals An investigation into the correlation of geomagnetic storms with tropospheric parameters over the South Pole

2003 ◽  
Vol 21 (5) ◽  
pp. 1095-1100 ◽  
Author(s):  
M. M. Lam ◽  
A. S. Rodger
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storm ◽  
Lower Stratosphere ◽  
Geomagnetic Storms ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Atmospheric Composition ◽  
South Pole ◽  
The South ◽  
Interplanetary Physics

Abstract. We test the proposal that the Sun’s magnetic activity, communicated via the solar wind, provides a link between solar variability and the Earth’s climate in the Antarctic troposphere. The strength of a geomagnetic storm is one indicator of the state of the solar wind; therefore, we use the dates of 51 moderate to strong winter geomagnetic storms from the period 1961–1990 to conduct a series of superposed epoch analyses of the winter South Pole isobaric height and temperature, at pressures of between 100–500 mbar. Using Student’s t -test to compare the mean value of the pre- and post-storm data sets, we find no evidence to support the hypothesis that there is a statistically-significant correlation between the onset of a geomagnetic storm and changes in the isobaric temperature or height of the troposphere and lower stratosphere over the South Pole during winter months. This concurs with a similar study of the variability of the troposphere and lower stratosphere over the South Pole (Lam and Rodger, 2002) which uses drops in the level of observed galactic cosmic ray intensity, known as Forbush decreases, as a proxy for solar magnetic activity instead of geomagnetic storms.Key words. Interplanetary physics (solar wind plasma; cosmic rays) – Atmospheric composition and structure (pressure, density and temperature)

scholarly journals MODEL BADAI IONOSFER INDONESIA TERKAIT BADAI GEOMAGNET (INDONESIA IONOSPHERIC STORM MODEL RELATED TO GEOMAGNETIC STORM)

2018 ◽  
Vol 15 (1) ◽  
pp. 25
Author(s):  
Anwar Santoso ◽  
Mira Juangsih ◽  
Sri Ekawati ◽  
Iyus Edi Rusnadi ◽  
Anton Winarko ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Geomagnetic Storms ◽  
Weather Conditions ◽  
Space Science ◽  
Ionospheric Storm ◽  
Science Center ◽  
Ionospheric Response ◽  
Future Space ◽  
Ap Index ◽  
Storm Model

 Knowledge about the ionospheric response to the geomagnetic storms is needed to support SWIFtS activity in Space Science Center-LAPAN. However, it is difficult to predict its behavior. As an approach, it needs a model of the ionospheric response to geomagnetic storms. In this paper, the modeling of the Indonesia ionospheric storms to the geomagnetic storm was done by modifying the global empirical models developed by Araujo-Pradere. By using ap index data, Dst index, and foF2 ionosphere from BPAA Sumedang of 2005-2015, it was obtained the Indonesia ionospheric storms model related to the geomagnetic storm. The analysis result showed that the Sumedang ionospheric storms model had a deviation or error < 40% of the data. Therefore it can be concluded that this models can be used to support the SWIFtS activity in Space Science Center-LAPAN for future space weather conditions.  AbstrakPengetahuan tentang respon ionosfer terhadap badai geomagnet sangat diperlukan untuk mendukung kegiatan SWIFtS di Pusat Sains Antariksa-LAPAN. Namun, sulit diprediksi perilakunya. Sebagai pendekatan, diperlukan sebuah model respon ionosfer terhadap badai geomagnet. Dalam makalah ini, dilakukan pemodelan badai ionosfer Indonesia terkait badai geomagnet dengan memodifikasi model empiris global yang telah dikembangkan oleh Araujo-Pradere. Dengan menggunakan data indeks ap, indeks Dst dan foF2 ionosfer BPAA Sumedang tahun 2005-2015 diperoleh model badai ionosfer regional Indonesia terhadap badai geomagnet. Dari analisis disimpulkan bahwa model badai ionosfer Sumedang tersebut memiliki simpangan atau kesalahan < 40% terhadap data. Hal ini menunjukkan bahwa model badai ionosfer Sumedang tersebut dapat dipergunakan untuk mendukung kegiatan SWIFtS di Pusat Sains Antariksa-LAPAN sebagai bahan pertimbangan dalam memprediksi kondisi cuaca antariksa akan datang.   

scholarly journals The Feature of Ionospheric Mid-Latitude Trough during Geomagnetic Storms Derived from GPS Total Electron Content (TEC) Data

2022 ◽  
Vol 14 (2) ◽  
pp. 369
Author(s):  
Na Yang ◽  
Tao Yu ◽  
Huijun Le ◽  
Libo Liu ◽  
Yang-Yi Sun ◽  
...  
Keyword(s):  
North America ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Quiet Time ◽  
Ionospheric Storm ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Storm Effects ◽  
Storm Effect

This study aims to investigate the features of the ionospheric mid-latitude trough over North America by using the MIT total electron content data obtained during three geomagnetic storms that occurred in August 2018, September 2017, and March 2015. The mid-latitude trough position sharply moves equatorward from the quiet-time subauroral latitude to mid-latitude with the decrease in SYM-H during geomagnetic storms. We find that the ionospheric behavior of TEC around the mid-latitude trough position displays three kinds of ionospheric storm effect: negative ionospheric storm effect, unchanged ionospheric behavior, and positive ionospheric storm effect. These ionospheric storm effects around the mid-latitude trough position are not always produced by the mid-latitude trough. The ionospheric storm effects produced by the mid-latitude trough are limited in the narrow mid-latitude trough regions, and are transmitted to other regions with the movement of the mid-latitude trough.

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