scholarly journals Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

2013 ◽  
Vol 31 (2) ◽  
pp. 263-276 ◽  
Author(s):  
O. P. Verkhoglyadova ◽  
B. T. Tsurutani ◽  
A. J. Mannucci ◽  
M. G. Mlynczak ◽  
L. A. Hunt ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Radiation Balance ◽  
Electron Content ◽  
Low Latitude ◽  
Emission Data ◽  
Total Electron

Abstract. We study solar wind–ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) – 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10–22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008–2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008–2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3 × 1010 W and 2.7 × 1010 W in 2008 and 2009, respectively. The roles of disturbance dynamos caused by high-latitude winds (due to particle precipitation and Joule heating in the auroral zones) and of prompt penetrating electric fields (PPEFs) in the solar wind–ionosphere coupling during these intervals are discussed. A correlation between geoeffective interplanetary electric field components and HSS intervals is shown. Both PPEF and disturbance dynamo mechanisms could play important roles in solar wind–ionosphere coupling during prolonged (up to days) external driving within HILDCAA intervals.

Variation on Solar Wind Parameters and Total Electron Content Over Middle‐ to Low‐Latitude Regions During Intense Geomagnetic Storms

Radio Science ◽  
2020 ◽  
Vol 55 (11) ◽  
Author(s):  
Roshan Kumar Mishra ◽  
Binod Adhikari ◽  
Narayan Prasad Chapagain ◽  
Rabin Baral ◽  
Priyanka Kumari Das ◽  
...  
Keyword(s):  
Solar Wind ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Solar Wind Parameters

scholarly journals Ionospheric Total Electron Content responses to HILDCAAs intervals

2019 ◽  
Author(s):  
Regia Pereira Silva ◽  
Clezio Marcos Denardini ◽  
Manilo Soares Marques ◽  
Laysa Cristina Araújo Resende ◽  
Juliano Moro ◽  
...  
Keyword(s):  
Solar Wind ◽  
Total Electron Content ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Long Duration ◽  
Wind Velocities ◽  
Hourly Distribution

Abstract. The High-Intensity Long-Duration and Continuous AE Activities (HILDCAA) intervals are capable of causing a global disturbance in the terrestrial ionosphere. However, the ionospheric storms' behavior due to these geomagnetic activity forms is still not widely understood. In this study, we seek to comprise the HILDCAAs disturbance time effects in the Total Electron Content (TEC) values with respect to the quiet days' pattern analyzing local time and seasonal dependences, and the influences of the solar wind velocity to a sample of ten intervals occurred in 2015 and 2016 years. The main results showed that the hourly distribution of the disturbance TEC may vary substantially between one interval and another. Doing a comparative to geomagnetic storms, while the positive ionospheric storms are more pronounced in the winter, this season presents less geoeffectiveness or almost none to HILDCAA intervals. It was find an equinoctial anomaly, since the equinoxes represent more ionospheric TEC responses during HILDCAA intervals than the solstices. Regarding to the solar wind velocities, although HILDCAA intervals are associated to High Speed Streams, this association does not present a direct relation regards to TEC disturbances in low and equatorial latitudes.

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 Ionospheric total electron content responses to HILDCAA intervals

2020 ◽  
Vol 38 (1) ◽  
pp. 27-34
Author(s):  
Regia Pereira da Silva ◽  
Clezio Marcos Denardini ◽  
Manilo Soares Marques ◽  
Laysa Cristina Araujo Resende ◽  
Juliano Moro ◽  
...  
Keyword(s):  
Solar Wind ◽  
Total Electron Content ◽  
High Speed ◽  
Electron Content ◽  
Direct Relation ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Long Duration ◽  
Wind Velocities ◽  
Hourly Distribution

Abstract. The High-Intensity Long-Duration and Continuous AE Activities (HILDCAA) intervals are capable of causing a global disturbance in the terrestrial ionosphere. However, the ionospheric storms' behavior due to these intervals is still not widely understood. In the current study, we seek to comprise the HILDCAA disturbance time effects in the total electron content (TEC) values with respect to the quiet days' pattern by analyzing local time and seasonal dependences, and the influences of the solar wind velocity on a sample of 10 intervals that occurred in the years 2015 and 2016. The main results showed that the hourly distribution of the disturbance TEC may vary substantially between one HILDCAA interval and another. An equinoctial anomaly was found since the equinoxes represent more ionospheric TEC responses than the solstices. Regarding the solar wind velocities, although HILDCAA intervals are associated with high-speed streams, this association does not present a direct relation to TEC disturbance magnitudes at low and equatorial latitudes.

Solar cycle variations in differential instrumental responses from ground‑based geomagnetic records

2020 ◽  
Author(s):  
Stuart Gilder ◽  
Michael Wack ◽  
Elena Kronberg ◽  
Ameya Prabhu
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
High Speed ◽  
Magnetic Measurements ◽  
Solar Wind Speed ◽  
Maximum Amplitude ◽  
Auroral Oval ◽  
Wide Frequency Range ◽  
The Magnetic Field

<p>We developed a new technique based on differences in instrument responses from ground-based magnetic measurements that extracts the frequency content of the magnetic field with periods ranging from 0.1 to 100 seconds. By stacking hourly averages over an entire year, we found that the maximum amplitude of the magnetic field oscillations occurred near solar noon over diurnal periods at all latitudes except in the auroral oval. Seasonal variability was identified only at high latitude. Long-term trends in field oscillations followed the solar cycle, yet the maxima occurred during the declining phase when high-speed streams in the solar wind dominated. A parameter based on solar wind speed and the relative variability of the interplanetary magnetic field correlated robustly with the ground-based measurements. Our findings suggest that turbulence in the solar wind, its interaction at the magnetopause, and its propagation into the magnetosphere stimulate magnetic field fluctuations at the ground on the dayside over a wide frequency range. Our method enables the study of field line oscillations using the publicly available, worldwide database of geomagnetic observatories.</p>

scholarly journals A combined analysis of geomagnetic data and cosmic ray secondaries in the September 2017 space weather phenomena studies

2018 ◽  
Author(s):  
Roman Sidorov ◽  
Anatoly Soloviev ◽  
Alexei Gvishiani ◽  
Viktor Getmanov ◽  
Mioara Mandea ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Characteristic Function ◽  
Space Weather ◽  
Solar Flares ◽  
Geomagnetic Storms ◽  
Cosmic Ray ◽  
Electron Content ◽  
Data Sets ◽  
Total Electron ◽  
Combined Analysis

Abstract. The September 2017 solar flares and the subsequent geomagnetic storms driven by the coronal mass ejections were recognized as the ones of the most powerful space weather events during the current solar cycle. The occurrence of the most powerful solar flares and magnetic storms during the declining phase of a solar cycle (including the current 24th cycle) is a well-known phenomenon. The purpose of this study is to better characterize these events by applying the generalized characteristic function approach for combined analysis of geomagnetic activity indices, total electron content data and secondary cosmic ray data from the muon hodoscope that contained Forbush decreases resulting from solar plasma impacts. The main advantage of this approach is the possibility of identification of low-amplitude specific features in the analyzed data sets, using data from several environmental sources. The data sets for the storm period on September 6–11, 2017, were standardized in a unified way to construct the generalized characteristic function representing the overall dynamics of the data sequence. The new developed technique can help to study various space weather effects and obtain new mutually supportive information on different phases of geomagnetic storm evolution, based on the geomagnetic and other environmental observations in the near-terrestrial space.

High-latitude ionospheric response to co-rotating interaction region- and coronal mass ejection-driven geomagnetic storms revealed by GPS tomography and ionosondes

2010 ◽  
Vol 466 (2123) ◽  
pp. 3391-3408 ◽  
Author(s):  
D. Pokhotelov ◽  
P. T. Jayachandran ◽  
C. N. Mitchell ◽  
M. H. Denton
Keyword(s):  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Plasma Density ◽  
Large Scale ◽  
Geomagnetic Storms ◽  
Interaction Region ◽  
Electron Content ◽  
Polar Cap ◽  
Total Electron ◽  
Mass Ejection

Positive ionospheric anomalies induced in the polar cap region by co-rotating interaction region (CIR)- and coronal mass ejection (CME)-driven geomagnetic storms are analysed using four-dimensional tomographic reconstructions of the ionospheric plasma density based on measurements of the total electron content along ray paths of GPS signals. The results of GPS tomography are compared with ground-based observations of F region plasma density by digital ionosondes located in the Canadian Arctic. It is demonstrated that CIR- and CME-driven storms can produce large-scale polar cap anomalies of similar morphology in the form of the tongue of ionization (TOI) that appears on the poleward edge of the mid-latitude dayside storm-enhanced densities in positive ionospheric storms. The CIR-driven event of 14–16 October 2002 was able to produce ionospheric anomalies (TOI) comparable to those produced by the CME-driven storms of greater Dst magnitude. From the comparison of tomographic reconstructions and ionosonde data with solar wind measurements, it appears that the formation of large-scale polar cap anomalies is controlled by the orientation of the interplanetary magnetic field (IMF) with the TOI forming during the periods of extended southward IMF under conditions of high solar wind velocity.

scholarly journals IONOSPHERIC DISTURBANCES OVER EASTERN SIBERIA DURING APRIL 12–15, 2016 GEOMAGNETIC STORMS

2020 ◽  
Vol 6 (1) ◽  
pp. 75-85
Author(s):  
Aleksandr Rubtsov ◽  
Boris Maletckii ◽  
Ekaterina Danilchuk ◽  
Ekaterina Smotrova ◽  
Aleksei Shelkov ◽  
...  
Keyword(s):  
Electron Density ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Peak Height ◽  
Negative Response ◽  
Small Scale ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Optical Instruments

We present the results of the complex study of ionospheric parameter variations during two geomagnetic storms, which occurred on April 12–15, 2016. The study is based on data from a set of radiophysical and optical instruments. Both the storms with no sudden commencement were generated by high-speed streams from a coronal hole. Despite the minor intensity of the storms (Dst ≥ –55 and –59 nT), we have revealed a distinct ionospheric response to these disturbances. A negative response of electron density and F2-layer critical frequency was observed during the main phase of both the storms. The amplitude of the negative response was higher for the second storm. The period of negative electron density deviations was accompanied by an increase in the peak height, as well as by the downward plasma drift in the evening and night hours, which is not typical of quiet conditions. We have also recorded sharp peaks in the AATR (Along Arc TEC Rate) index and in total electron content noise spikes on average 2–2.5 times. This indicates an intensification of small-scale ionospheric disturbances caused by disturbed geomagnetic conditions and high substorm activity.

A superposed epoch analysis of geomagnetic storms

1994 ◽  
Vol 12 (7) ◽  
pp. 612-624 ◽  
Author(s):  
J. R. Taylor ◽  
M. Lester ◽  
T. K. Yeoman
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
High Speed ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Magnetic Activity ◽  
Wind Pressure ◽  
Superposed Epoch Analysis ◽  
Controlling Parameter ◽  
Epoch Analysis

Abstract. A superposed epoch analysis of geomagnetic storms has been undertaken. The storms are categorised via their intensity (as defined by the Dst index). Storms have also been classified here as either storm sudden commencements (SSCs) or storm gradual commencements (SGCs, that is all storms which did not begin with a sudden commencement). The prevailing solar wind conditions defined by the parameters solar wind speed (vsw), density (ρsw) and pressure (Psw) and the total field and the components of the interplanetary magnetic field (IMF) during the storms in each category have been investigated by a superposed epoch analysis. The southward component of the IMF, appears to be the controlling parameter for the generation of small SGCs (-100 nT< minimum Dst ≤ -50 nT for ≥ 4 h), but for SSCs of the same intensity solar wind pressure is dominant. However, for large SSCs (minimum Dst ≤ -100 nT for ≥ 4 h) the solar wind speed is the controlling parameter. It is also demonstrated that for larger storms magnetic activity is not solely driven by the accumulation of substorm activity, but substantial energy is directly input via the dayside. Furthermore, there is evidence that SSCs are caused by the passage of a coronal mass ejection, whereas SGCs result from the passage of a high speed/ slow speed coronal stream interface. Storms are also grouped by the sign of Bz during the first hour epoch after the onset. The sign of Bz at t = +1 h is the dominant sign of the Bz for ~24 h before the onset. The total energy released during storms for which Bz was initially positive is, however, of the same order as for storms where Bz was initially negative.

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