scholarly journals Even moderate geomagnetic pulsations can cause fluctuations of foF2 frequency of the auroral ionosphere

2020 ◽  
Author(s):  
Nadezda Yagova ◽  
Alexander Kozlovsky ◽  
Evgeny Fedorov ◽  
Olga Kozyreva
Keyword(s):  
Space Weather ◽  
Critical Frequency ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Pressure Fluctuations ◽  
Weather Conditions ◽  
Geomagnetic Pulsations ◽  
Station Pair ◽  
Using Data ◽  
Magnetic Meridian

Abstract. Using data of the ionosonde in Sodankyla, (SOD, 67° N, 27° E, Finland), variations of the critical frequency of o-mode radiowave reflected from ionospheric F2 layer (foF2) in 1–5 mHz frequency range and their possible association with long period (Pc5/Pi3) geomagnetic pulsations are studied. For that, a technique of automatic detection of the foF2 critical frequency from an ionogram is developed and applied to daytime Pc5/Pi3 geomagnetic pulsations and foF2 fluctuations during several months of years 2014–2015 near the maximum of 24-th Solar cycle. The variations of foF2 are compared with the Pc5/Pi3 geomagnetic pulsations at SOD station, and the influence of pulsations' spatial scale is analyzed with the data of a station pair located at the same magnetic meridian but separated in latitude. The variations of foF2 are in the majority of cases decoupled from the geomagnetic pulsations on the ground. Meanwhile, the analysis of geomagnetic and foF2 variations show intervals with noticeable coherence for both horizontal components. These coherent pulsations are predominantly registered in the afternoon sector of the magnetic local time (MLT). Statistically, their spectral content, polarization and spatial distribution differ from averaged parameters of post-noon Pc5 pulsations. The pulsations, coherent to foF2 fluctuations, demonstrate features typical for Alfven field-line resonance. The analysis of space weather conditions favorable for the occurrence of coherent geomagnetic/foF2 pulsations show that these pulsations are registered mostly under moderately disturbed conditions. Comparison of space weather parameters for all the intervals analyzed and the intervals of high geomagnetic/foF2 coherence show that the latter correspond mostly to intermediate values of indexes of geomagnetic (Dst) and auroral (AE) activity, solar wind speed and dynamic pressure fluctuations.

scholarly journals Geomagnetic pulsations in the Pc5/Pi3 frequency range and fluctuations of foF2 frequency

2019 ◽  
Author(s):  
Nadezda Yagova ◽  
Alexander Kozlovsky ◽  
Evgeny Fedorov ◽  
Olga Kozyreva
Keyword(s):  
Spatial Distribution ◽  
Critical Frequency ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Automatic Detection ◽  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Spectral Content ◽  
Using Data ◽  
Fof2 Critical Frequency

Abstract. Using data of the ionosonde in Sodankyla, (SOD, 67° N, 27° E, Finland), parameters of variations of foF2 critical frequency in the Pc5/Pi3 (1–5 mHz) frequency range are studied. For that, a technique of automatic detection of critical frequency from an ionogram is developed. The variations of foF2 are compared with the Pc5/Pi3 geomagnetic pulsations on the ground and in the magnetosphere. The variations of foF2 are in the majority of cases decoupled from the Pc5/Pi3 on the ground. Meanwhile, the analysis of geomagnetic and foF2 variations at SOD show intervals with noticeable coherence for both horizontal components. These coherent pulsations are predominantly registered in the afternoon MLT sector. Statistically, their spectral content, polarization and spatial distribution differs from those of background variations. Coherent pulsation tend to occur under moderate geomagnetic and auroral activity, SW speed, and dynamic pressure fluctuations. The fraction of coherent geomagnetic and foF2 pulsations is higher for the geomagnetic pulsations registered in the magnetosphere, than on the ground.

scholarly journals Even moderate geomagnetic pulsations can cause fluctuations of <i>fo</i>F2 frequency of the auroral ionosphere

2021 ◽  
Vol 39 (3) ◽  
pp. 549-562
Author(s):  
Nadezda Yagova ◽  
Alexander Kozlovsky ◽  
Evgeny Fedorov ◽  
Olga Kozyreva
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Critical Frequency ◽  
Solar Wind Speed ◽  
Weather Conditions ◽  
Wind Pressure ◽  
Geomagnetic Pulsations ◽  
Radio Waves ◽  
Magnetic Pulsations ◽  
Solar Wind Pressure

Abstract. The ionosonde at the Sodankylä Geophysical Observatory (SOD; 67∘ N, 27∘ E; Finland) routinely performs vertical sounding once per minute which enables the study of fast ionospheric variations at a frequency of the long-period geomagnetic pulsations Pc5–6/Pi3 (1–5 mHz). Using the ionosonde data from April 2014–December 2015 and colocated geomagnetic measurements, we have investigated a correspondence between the magnetic field pulsations and variations of the critical frequency of radio waves reflected from the ionospheric F2 layer (foF2). For this study, we have developed a technique for automated retrieval of the critical frequency of the F2 layer from ionograms. As a rule, the Pc5–6/Pi3 frequency band fluctuations in foF2 were observed at daytime during quiet or moderately disturbed space weather conditions. In most cases (about 80 %), the coherence between the foF2 variations and geomagnetic pulsations was low. However in some cases (specified as “coherent”) the coherence was as large as γ2≥0.5. The following conditions are favorable for the occurrence of coherent cases: enhanced auroral activity (6 h maximal auroral electrojet (AE) ≥800 nT), high solar wind speed (V>600 km/s), fluctuating solar wind pressure and northward interplanetary magnetic field. In the cases when the coherence was higher at shorter periods of oscillations, the magnetic pulsations demonstrated features typical for the Alfvén field line resonance.

scholarly journals Several special conditions in the solar wind fora supersubstorm appearance.

2020 ◽  
Author(s):  
I.V. Despirak ◽  
◽  
A.A. Lubchich ◽  
N.G. Kleimenova ◽  
◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Data Base ◽  
Space Weather ◽  
Large Scale ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Weather Conditions ◽  
The Other ◽  
Solar Wind Parameters

Analysis of the space weather conditions associated with supersubstorms (SSS) was carried out. Two magnetic storms, on 11 April and on 18 April 2001 have been studied and compared. During the first storm, there were registered twoevents of the supersubstorms with intensity of the SML index ~2000-3000 nT, whereas during the second storm there were observed two intense substorms with SML ~ 1500 nT. Solar wind conditions before appearance of the SSSs and intense substorms were compared. For this purpose, the OMNI data base, the catalog of large-scale solar wind phenomena and the data from the magnetic ground-based stations of the SuperMAG network (http://supermag.jhuapl.edu/) were combined. It was shown that the onsets of the SSS event were preceded by strong jumps in the dynamic pressure and density of the solar wind, which were observed against the background of the high solar wind speed and high values of the southern ВZcomponent of the IMF. Comparison with the usual substorms showed thatsome solar wind parameters were higher before SSSs, then before usual substorms: the dynamic pressure, the speed and the magnitude of IMF. On the other hand, the PC index values was the same for these all substorms, that leads to the conclusion about the possible independence of SSS appearance on the level of solar energy penetrated to the magnetosphere.

3D MHD study of the Earth magnetosphere response during extreme space weather conditions

2021 ◽  
Author(s):  
Jacobo Varela Rodriguez ◽  
Sacha A. Brun ◽  
Antoine Strugarek ◽  
Victor Réville ◽  
Filippo Pantellini ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
Coronal Mass Ejections ◽  
Main Sequence ◽  
Dynamic Pressure ◽  
Weather Conditions ◽  
The Sun ◽  
Earth Surface ◽  
The Earth ◽  
The Imf

&lt;p&gt;&lt;span&gt;The aim of the study is to analyze the response of the Earth magnetosphere for various space weather conditions and model the effect of interplanetary coronal mass ejections. The magnetopause stand off distance, open-closed field lines boundary and plasma flows towards the planet surface are investigated. We use the MHD code PLUTO in spherical coordinates to perform a parametric study regarding the dynamic pressure and temperature of the solar wind as well as the interplanetary magnetic field intensity and orientation. The range of the parameters analyzed extends from regular to extreme space weather conditions consistent with coronal mass ejections at the Earth orbit. The direct precipitation of the solar wind on the Earth day side at equatorial latitudes is extremely unlikely even during super coronal mass ejections. For example, the SW precipitation towards the Earth surface for a IMF purely oriented in the Southward direction requires a IMF intensity around 1000 nT and the SW dynamic pressure above 350 nPa, space weather conditions well above super-ICMEs. The analysis is extended to previous stages of the solar evolution considering the rotation tracks from Carolan (2019). The simulations performed indicate an efficient shielding of the Earth surface 1100 Myr after the Sun enters in the main sequence. On the other hand, for early evolution phases along the Sun main sequence once the Sun rotation rate was at least 5 times faster (&lt; 440 Myr), the Earth surface was directly exposed to the solar wind during coronal mass ejections (assuming today&amp;#180;s Earth magnetic field). Regarding the satellites orbiting the Earth, Southward and Ecliptic IMF orientations are particularly adverse for Geosynchronous satellites, partially exposed to the SW if the SW dynamic pressure is 8-14 nPa and the IMF intensity 10 nT. On the other hand, Medium orbit satellites at 20000 km are directly exposed to the SW during Common ICME if the IMF orientation is Southward and during Strong ICME if the IMF orientation is Earth-Sun or Ecliptic. The same way, Medium orbit satellites at 10000 km are directly exposed to the SW if a Super ICME with Southward IMF orientation impacts the Earth.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;This work was supported by the project 2019-T1/AMB-13648 founded by the Comunidad de Madrid, grants ERC WholeSun, Exoplanets A and PNP. We extend our thanks to CNES for Solar Orbiter, PLATO and Meteo Space science support and to INSU/PNST for their financial support.&lt;/p&gt;

MMS observations of wave activity in the particle foreshock bubble foreshock region

2020 ◽  
Author(s):  
Mengmeng Wang ◽  
Quanqi Shi
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Wave Activity ◽  
Trailing Edge ◽  
Energetic Ions ◽  
Transient Phenomena ◽  
Magnetospheric Multiscale ◽  
Using Data ◽  
The Waves

&lt;p&gt;Foreshock bubbles (FBs) are kinetic transient phenomena formed due to the interaction between IMF discontinuities and backstreaming energetic ions in Earth&amp;#8217;s foreshock region. FBs can be driven by both rotational discontinuities and tangential discontinuities and are typically observed under higher solar wind speed conditions. They play important roles in the solar wind-magnetosphere coupling because of very large dynamic pressure variations associated with them. The trailing edge of an FB is usually a fast shock which forms due to the expansion of the thermal plasma in the core. Using data from Magnetospheric Multiscale (MMS) mission, we investigate an FB structure with a particle foreshock region upstream its trailing edge. Distinct wave activity is observed in the particle foreshock region and wave analysis shows that the waves with periods of a few seconds may be generated by shock-reflected ion instabilities. The ions reflected at FB shock are observed and the acceleration mechanism needs to be analyzed.&lt;/p&gt;

Space weather at Mercury as observed by the THEMIS telescope from Earth

2020 ◽  
Author(s):  
Melinda Dósa ◽  
Valeria Mangano ◽  
Anna Milillo ◽  
Stefano Massetti ◽  
Zsofia Bebesi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Space Weather ◽  
Dynamic Pressure ◽  
Weather Conditions ◽  
Angular Distance ◽  
Special Role ◽  
Solar Wind Magnetic Field

&lt;p&gt;The dynamic changes of Mercury&amp;#8217;s Na exosphere are investigated here, in relation to space weather conditions. Sodium plays a special role in Mercury&amp;#8217;s exosphere: due to its strong resonance D lines at 5890-95&amp;#197; it has been observed and monitored by Earth-based telescopes for decades. Different and highly variable patterns of Na-emission have been identified. In addition to the release processes already studied extensively in the past, we aim here to investigate the following factors more in detail: the distance to the Sun, position in relation to the ecliptic plane and solar wind magnetic field strength and direction. In order to better investigate the relationship of these factors, we have studied the intensity of Na-emission as a function of solar wind dynamic pressure and TAA of Mercury by means of the extended dataset images collected from 2009 to 2013 by Earth-based observations performed at the THEMIS solar telescope. Solar wind velocity and density values are propagated with the magnetic lasso method to the position of Mercury from nearby space probes and compared with Na emission intensity. Data of either ACE or one of the two STEREO spacecraft were used, depending on which spacecraft had a smaller angular distance to Mercury. Single cases are studied qualitatively, and a longer-term quantitative comparison is shown, including further parameters (solar wind magnetic field strength and direction, TAA).&lt;/p&gt;

scholarly journals Using Machine Learning Methods to Identify Particle Types from Doppler Lidar Measurements in Iceland

2021 ◽  
Vol 13 (13) ◽  
pp. 2433
Author(s):  
Shu Yang ◽  
Fengchao Peng ◽  
Sibylle von Löwis ◽  
Guðrún Nína Petersen ◽  
David Christian Finger
Keyword(s):  
Machine Learning ◽  
Weather Conditions ◽  
Dust Storms ◽  
Machine Learning Algorithms ◽  
Lidar Data ◽  
Data Sets ◽  
Doppler Lidar ◽  
Lidar Measurements ◽  
Using Data ◽  
Filter Noise

Doppler lidars are used worldwide for wind monitoring and recently also for the detection of aerosols. Automatic algorithms that classify the lidar signals retrieved from lidar measurements are very useful for the users. In this study, we explore the value of machine learning to classify backscattered signals from Doppler lidars using data from Iceland. We combined supervised and unsupervised machine learning algorithms with conventional lidar data processing methods and trained two models to filter noise signals and classify Doppler lidar observations into different classes, including clouds, aerosols and rain. The results reveal a high accuracy for noise identification and aerosols and clouds classification. However, precipitation detection is underestimated. The method was tested on data sets from two instruments during different weather conditions, including three dust storms during the summer of 2019. Our results reveal that this method can provide an efficient, accurate and real-time classification of lidar measurements. Accordingly, we conclude that machine learning can open new opportunities for lidar data end-users, such as aviation safety operators, to monitor dust in the vicinity of airports.

scholarly journals Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

2005 ◽  
Vol 23 (2) ◽  
pp. 609-624 ◽  
Author(s):  
K. E. J. Huttunen ◽  
J. Slavin ◽  
M. Collier ◽  
H. E. J. Koskinen ◽  
A. Szabo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Interplanetary Shock ◽  
Wind Pressure ◽  
Shock Propagation ◽  
Interplanetary Shocks ◽  
Maximum Variance ◽  
The Magnetic Field

Abstract. Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary.

Environmental Conditions Associated With Youth Delinquency Events: A Temporal, Meteorological, and Contextual Perspective

2021 ◽  
pp. 001391652110605
Author(s):  
Alexander Trinidad ◽  
César San Juan ◽  
Laura Vozmediano
Keyword(s):  
Violent Crime ◽  
Weather Conditions ◽  
Violent Crimes ◽  
Public Places ◽  
Youth Delinquency ◽  
Violent Youth ◽  
Direct Association ◽  
Using Data ◽  
Public Holidays ◽  
Rainfall Level

Research on youth delinquency has been essential for gaining a deeper understanding of the etiology of delinquent behavior. Studies considering the environmental perspective have increased during the last decade, but relatively little attention has been paid to temporal patterns and weather conditions. The present study explores the seasonality of youth delinquency as well as the association between violent and non-violent youth offenses and temperature, rainfall, level of darkness, type of day, type of place, and companionship, using data gathered by the police along with data obtained from official weather agencies. To this end, we conducted ANOVA and contingency table analyses. Seasonality was found for non-violent crimes. Companionship, semi-public, and public places were all associated with a higher likelihood of non-violent crime, while darkness and public holidays raise the odds of violent crime to happen. No direct association was found between temperature and type of crime.

Sign in / Sign up

Export Citation Format

Share Document