scholarly journals A Study of Solar Flare Effects on the Geomagnetic Field Components during Solar Cycles 23 and 24

Atmosphere ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 69
Author(s):  
Oswald Didier Franck Grodji ◽  
Vafi Doumbia ◽  
Paul Obiakara Amaechi ◽  
Christine Amory-Mazaudier ◽  
Kouassi N’guessan ◽  
...  
Keyword(s):  
Solar Flare ◽  
Geomagnetic Field ◽  
Magnetic Equator ◽  
Solar Cycles ◽  
Low Latitudes ◽  
Cycle 24 ◽  
Using Data ◽  
Solar Flare Effects ◽  
The Impact ◽  
Monthly Variations

In this paper, we investigated the impact of solar flares on the horizontal (H), eastward (Y) and vertical (Z) components of the geomagnetic field during solar cycles 23 and 24 (SC23/24) using data of magnetometer measurements on the sunlit side of the Earth. We examined the relation between sunspot number and solar flare occurrence of various classes during both cycles. During SC23/24, we obtained correlation coefficient of 0.93/0.97, 0.96/0.96 and 0.60/0.56 for C-class, M-class and X-class flare, respectively. The three components of the geomagnetic field reached a peak a few minutes after the solar flare occurrence. Generally, the magnetic crochet of the H component was negative between the mid-latitudes and Low-latitudes in both hemispheres and positive at low latitudes. By contrast, the analysis of the latitudinal variation of the Y and Z components showed that unlike the H component, their patterns of variations were not coherent in latitude. The peak amplitude of solar flare effect (sfe) on the various geomagnetic components depended on many factors including the local time at the observing station, the solar zenith angle, the position of the station with respect to the magnetic equator, the position of solar flare on the sun and the intensity of the flare. Thus, these peaks were stronger for the stations around the magnetic equator and very low when the geomagnetic field components were close to their nighttime values. Both cycles presented similar monthly variations with the highest sfe value (ΔHsfe = 48.82 nT for cycle 23 and ΔHsfe = 24.68 nT for cycle 24) registered in September and lowest in June for cycle 23 (ΔHsfe = 8.69 nT) and July for cycle 24 (ΔHsfe = 10.69 nT). Furthermore, the sfe was generally higher in cycle 23 than in cycle 24.

scholarly journals An intense SFE and SSC event in geomagnetic <i>H</i>, <i>Y</i> and <i>Z</i> fields at the Indian chain of observatories

1997 ◽  
Vol 15 (10) ◽  
pp. 1301-1308 ◽  
Author(s):  
R. G. Rastogi ◽  
D. R. K. Rao ◽  
S. Alex ◽  
B. M. Pathan ◽  
T. S. Sastry
Keyword(s):  
Solar Flare ◽  
Geomagnetic Storm ◽  
Geomagnetic Field ◽  
Current System ◽  
Equatorial Electrojet ◽  
Start Time ◽  
Low Latitude ◽  
Ionospheric Current ◽  
Ionospheric Current System ◽  
Solar Flare Effects

Abstract. Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.

scholarly journals Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

2017 ◽  
Vol 35 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Vafi Doumbia ◽  
Kouadio Boka ◽  
Nguessan Kouassi ◽  
Oswald Didier Franck Grodji ◽  
Christine Amory-Mazaudier ◽  
...  
Keyword(s):  
Solar Flare ◽  
Electric Field ◽  
West Africa ◽  
Geomagnetic Storm ◽  
Geomagnetic Field ◽  
Equatorial Electrojet ◽  
Geomagnetic Disturbances ◽  
The North ◽  
Low Latitudes ◽  
Dip Equator

Abstract. In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north–south (Ex) and east–west (Ey) components of telluric electric field were analyzed, along with that of the three components (H,  D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of −110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex =  520 mV km−1 and Ey =  400 mV km−1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex =  550 mV km−1 and Ey =  340 mV km−1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

scholarly journals The impact of CMEs on the critical frequency of F2-layer ionosphere (foF2)

2019 ◽  
Vol 15 (S356) ◽  
pp. 400-402
Author(s):  
Alene Seyoum ◽  
Nat Gopalswamy ◽  
Melessew Nigussie ◽  
Nigusse Mezgebe
Keyword(s):  
Critical Frequency ◽  
Angular Width ◽  
High Latitudes ◽  
Solar Cycles ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Critical Frequency Fof2 ◽  
The Impact ◽  
Very High

AbstractThe ionospheric critical frequency (foF2) from ionosonde measurements at geographic high, middle, and low latitudes are analyzed with the occurrence of coronal mass ejections (CMEs) in long term variability of the solar cycles. We observed trends of monthly maximum foF2 values and monthly averaged values of CME parameters such as speed, angular width, mass, and kinetic energy with respect to time. The impact of CMEs on foF2 is very high at high latitudes and low at low latitudes. The time series for monthly maximum foF2 and monthly-averaged CME speed are moderately correlated at high and middle latitudes.

scholarly journals LOW-POWER SOLAR FLARES OF OPTICAL AND X-RAY WAVELENGTHS FOR SOLAR CYCLES 21–24

2020 ◽  
Vol 6 (3) ◽  
pp. 18-25
Author(s):  
Aleksandr Borovik ◽  
Anton Zhdanov
Keyword(s):  
Solar Activity ◽  
Low Power ◽  
Solar Flares ◽  
Optical Emission ◽  
Flare Activity ◽  
X Rays ◽  
Solar Cycles ◽  
X Ray ◽  
Cycle 24 ◽  
Using Data

Using data obtained in optical and X-ray wavelengths, we have analyzed solar flare activity for cycles 21–24. Over the last three cycles, solar activity is shown to decrease significantly. As compared to solar cycle 21 (the most active over the last 50 years), in cycle 24 2–4-class large optical flares are 4.4 times rarer; 1-class flares, 8.2 times; and S-class small flares, 4.1 times. The number of X-class flares decreased 3.7 times; M-class flares, 3.2 times. This confirms that secular solar activity trends affect peak values of 11-year cycles. It is shown that optical low-power flares can be accompanied by proton fluxes and X-ray bursts of different intensity, including X-class ones. Ranges of small flare emission in soft X-rays largely overlap with emission ranges of flares of high optical classes. We have confirmed that X-ray emission from solar flares appears on average 2 min before the optical emission. The X-ray maximum for small optical flares and 1-class flares occurs approximately 1 min later; for 2–4-class flares, 2 min.

scholarly journals LOW-POWER SOLAR FLARES OF OPTICAL AND X-RAY WAVELENGTHS FOR SOLAR CYCLES 21–24

2020 ◽  
Vol 6 (3) ◽  
pp. 16-22
Author(s):  
Aleksandr Borovik ◽  
Anton Zhdanov
Keyword(s):  
Solar Activity ◽  
Low Power ◽  
Solar Flares ◽  
Optical Emission ◽  
Flare Activity ◽  
X Rays ◽  
Solar Cycles ◽  
X Ray ◽  
Cycle 24 ◽  
Using Data

Using data obtained in optical and X-ray wavelengths, we have analyzed solar flare activity for cycles 21–24. Over the last three cycles, solar activity is shown to decrease significantly. As compared to solar cycle 21 (the most active over the last 50 years), in cycle 24 2–4-class large optical flares are 4.4 times rarer; 1-class flares, 8.2 times; and S-class small flares, 4.1 times. The number of X-class flares decreased 3.7 times; M-class flares, 3.2 times. This confirms that secular solar activity trends affect peak values of 11-year cycles. It is shown that optical low-power flares can be accompanied by proton fluxes and X-ray bursts of different intensity, including X-class ones. Ranges of small flare emission in soft X-rays largely overlap with emission ranges of flares of high optical classes. We have confirmed that X-ray emission from solar flares appears on average 2 min before the optical emission. The X-ray maximum for small optical flares and 1-class flares occurs approximately 1 min later; for 2–4-class flares, 2 min.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

Interculturalism and the Acceptance of Minority Groups

2020 ◽  
Vol 51 (2) ◽  
pp. 135-140 ◽  
Author(s):  
Maykel Verkuyten ◽  
Kumar Yogeeswaran
Keyword(s):  
Minority Groups ◽  
Psychological Research ◽  
Survey Experiment ◽  
Social Psychological ◽  
Negative Attitudes ◽  
Positive Attitudes ◽  
Social Psychological Research ◽  
Using Data ◽  
The Impact ◽  
Situational Effect

Abstract. Multiculturalism has been criticized and rejected by an increasing number of politicians, and social psychological research has shown that it can lead to outgroup stereotyping, essentialist thinking, and negative attitudes. Interculturalism has been proposed as an alternative diversity ideology, but there is almost no systematic empirical evidence about the impact of interculturalism on the acceptance of migrants and minority groups. Using data from a survey experiment conducted in the Netherlands, we examined the situational effect of promoting interculturalism on acceptance. The results show that for liberals, but not for conservatives, interculturalism leads to more positive attitudes toward immigrant-origin groups and increased willingness to engage in contact, relative to multiculturalism.

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