Multiwavelength Analysis of the Impact Polarization of 2001 June 15 Solar Flare

2005 ◽  
Vol 631 (1) ◽  
pp. 618-627 ◽  
Author(s):  
Z. Xu ◽  
J.‐C. Henoux ◽  
G. Chambe ◽  
M. Karlicky ◽  
C. Fang
Keyword(s):  
Solar Flare ◽  
The Impact ◽  
Impact Polarization

scholarly journals Evaluating the Impact of Pre-clustering and Class Imbalance on Solar Flare Forecasting

2018 ◽  
Author(s):  
Mirelle C. Bueno ◽  
Guilherme P. Coelho ◽  
Ana Estela A. Da Silva ◽  
André L. S. Gradvohl
Keyword(s):  
Machine Learning ◽  
Solar Flare ◽  
Transmission Lines ◽  
Solar Flares ◽  
Power Transmission ◽  
Class Imbalance ◽  
The Sun ◽  
Power Transmission Lines ◽  
Short Circuits ◽  
The Impact

Among the phenomena that occur on the surface of the Sun, solar flares may cause several damages, from short circuits in power transmission lines to complete interruptions in telecommunications systems. In order to mitigate these effects, many works have been dedicated to the proposal of mechanisms capable of predicting the occurrence of solar flares. In this context, the present work sought to evaluate two aspects related to machine learning-based solar flare forecasting: (i) the impact of class imbalance in training datasets on the performance of the predictors; and (ii) whether the incorporation of a pre-clustering step prior to the classifiers training contributes to a better prediction.

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.

First Results of Mgi(3p1P1–4d1D2) Line Linear Impact Polarization during the Solar Flare on 2001 June 15

2006 ◽  
Vol 650 (2) ◽  
pp. 1193-1198 ◽  
Author(s):  
Z. Xu ◽  
J. C. Henoux ◽  
G. Chambe ◽  
A. G. Petrashen ◽  
C. Fang
Keyword(s):  
Solar Flare ◽  
First Results ◽  
Impact Polarization

scholarly journals The morphology of average solar flare time profiles from observations of the Sun’s lower atmosphere

2021 ◽  
Vol 502 (3) ◽  
pp. 3922-3931
Author(s):  
Larisa K Kashapova ◽  
Anne-Marie Broomhall ◽  
Alena I Larionova ◽  
Elena G Kupriyanova ◽  
Ilya D Motyk
Keyword(s):  
Solar Flare ◽  
Power Law ◽  
Solar Flares ◽  
Lower Atmosphere ◽  
Decay Phase ◽  
Dense Layer ◽  
Time Profiles ◽  
Spectral Bands ◽  
The Impact ◽  
M Dwarf

ABSTRACT We study the decay phase of solar flares in several spectral bands using a method based on that successfully applied to white light flares observed on an M4 dwarf. We selected and processed 102 events detected in the Sun-as-a-star flux obtained with SDO/AIA images in the 1600 and 304 Å channels and 54 events detected in the 1700 Å channel. The main criterion for the selection of time profiles was a slow, continuous flux decay without significant new bursts. The obtained averaged time profiles were fitted with analytical templates, using different time intervals, that consisted of a combination of two independent exponents or a broken power law. The average flare profile observed in the 1700 Å channel decayed more slowly than the average flare profile observed on the M4 dwarf. As the 1700 Å emission is associated with a similar temperature to that usually ascribed to M dwarf flares, this implies that the M dwarf flare emission comes from a more dense layer than solar flare emission in the 1700 Å band. The cooling processes in solar flares were best described by the two exponents model, fitted over the intervals t1 = [0, 0.5]t1/2 and t2 = [3, 10]t1/2, where t1/2 is time taken for the profile to decay to half the maximum value. The broken power-law model provided a good fit to the first decay phase, as it was able to account for the impact of chromospheric plasma evaporation, but it did not successfully fit the second decay phase.

Is a whole-mantle convection the key to solving the Tunguska 1908 problem?

2020 ◽  
Author(s):  
Boris R. German
Keyword(s):  
Solar Flare ◽  
Mantle Convection ◽  
Shear Velocity ◽  
Outer Core ◽  
Surface Uplift ◽  
The Earth ◽  
Eastern Australia ◽  
Solar Perturbations ◽  
Tunguska Event ◽  
The Impact

<p>It is generally accepted that the Tunguska event in Siberia on 30 June, 1908 resulted from an explosion of cosmic body. However, there is no common agreement that this bolide really existed. Moreover, registered ultra low frequency (ULF) magnetic oscillations in Kiel, Germany on 27-30 June 1908 [1] had a correlate with the 'acoustic halo' (ULF) of a solar flare [2].</p><p>Large low-shear velocity provinces (LLSVPs) are linked to so-called blobs located atop the Earth's outer core [3]. It was shown the Earth's D"-layer core-mantle boundary was perturbed by both the solar flare and an anomalous lunar-solar tide during the Tunguska 1908 event [2]. Therefore, gravitational/magnetic lunar-solar perturbations could have triggered a plume/hotspot/LIP activation by means of a LLSVPs convection.</p><p>It was suggested that planetary hotspots chains are interconnected [4]. Indeed, during the Tunguska event brightest glows were observed over the Eifel volcano and more weak one over the Yellowstone volcano (both volcanoes are associated with hotspots) [5]. In addition, day by day a slowly lifting of the earth round the diabase stones was registered in Tasmania from 7 June till 29 June, 1908 [6]. This lifting was independent from atmospheric temperature variations and terminated as soon as a blast took place in the caldera of Tunguska paleovolcano on 30 June, 1908 [5, 6]. Observations in Tasmania remained a mystery for a long time. Recently scientists discovery the Cosgrove hotspot had moved from Eastern Australia to Tasmania [7]. In our opinion, the Cosgrove did not lose its activity fully 9 My ago as previously assumed: the Darwin crater in Tasmania originated about of 803 ka years and large volume ejected glasses in/around this small crater contradicts to the impact origin [5, 8]. Therefore, we consider the underground activation of Cosgrove hotspot as a cause of surface uplift in Tasmania from 7 to 30 June 1908.</p><p>As in Tasmania, moving mantle hotspots were registered in Eastern Siberia [9]. Probably, hotspots in Tasmania (near Pacific LLSVPs) and in the Tunguska basin (near Perm LLSVPs) are interconnected. Because common hotspots thermal energy was released in/by the Tunguska paleovolcano explosion on 30 June 1908, the fluidal pressure of the Cosgrove hotspot under Tasmania was reduced, resulting in the termination of surface uplift. Since meteorites could not have caused the earth uplift in Tasmania, the impact hypothesis for the Tunguska phenomenon can be excluded. All data favor an endogenic origin of this event due to lunar-solar perturbations and the whole-mantle convection.</p><p><span>[1]. Weber L. (1908) Astronomische Nachrichten, </span><strong><span>178</span></strong><span>, 23. [2]. German B. (2010) EPSC2010-430. [3]. Duncombe J. (2019) Eos, </span><strong><span>100</span></strong><span>. [4]. Courtillot V. (1990) ISBN 9780813722474, 401. [5]. German B. (2019) ISBNs 9783981952605(in Russian)/9783981952612(in English). [6]. Scott H. (1908) Nature, </span><strong><span>78</span></strong><span>(2025), 376. [7]. Davies D. (2015) Nature, </span><strong><span>525</span></strong><span>, 511. [8]. Haines P. (2005) Australian Journal Earth Sciences, </span><strong><span>52</span></strong><span>, 481. [9]. Rosen O. (2015) ISBN 9785902754954, 148.</span></p>

scholarly journals The theoretical impact polarization of the O I 6300 Å red line of Earth aurorae

2011 ◽  
Vol 29 (1) ◽  
pp. 71-79 ◽  
Author(s):  
V. Bommier ◽  
S. Sahal-Bréchot ◽  
J. Dubau ◽  
M. Cornille
Keyword(s):  
Cross Section ◽  
Threshold Energy ◽  
Incident Beam ◽  
Dissociative Recombination ◽  
High Energy ◽  
Electric Interaction ◽  
The Cross ◽  
The Impact ◽  
Impact Polarization ◽  
Red Line

Abstract. We are presenting a semi-classical theory of the impact polarization due to a quadrupolar electric excitation, which is the case of this forbidden line. In addition, this line is also radiatively forbidden being a triplet-singlet transition. This last feature is overcome by scaling the semi-classical result to a full quantum calculation at a single energy value. The cross-section and impact polarization are thus obtained as a function of energy, in agreement with the quantum calculations that exist only for the cross-section. The behavior of the impact polarization is found to be quite different than that of the usual dipolar electric interaction. Let us denote as radial the polarization parallel to the incident beam or magnetic field, and as tangential the perpendicular polarization. In the case of the dipolar electric interaction (permitted lines), the polarization is radial at low energy, and tangential at high energy, and it vanishes at energy about twelve times the threshold energy. In the case of the quadrupolar electric interaction, we observe quite different behavior, with the polarization vanishing point much closer to the threshold energy. This leads us to reanalyze the auroral red line polarization observation by Lilensten et al. (2008). From polarization observations made at Svalbard, they conclude to a rather strong tangential polarization observed during a 4-h recording including two auroral events. The existence of tangential polarization is questioned by our new theory, which leads to reconsidering the contribution of scattered parasitic light from a neighboring city that was mentioned but discarded by the authors. Finally, we conclude that the line is only weakly radially polarized by electron impact, and only during the auroral events. The weak polarization level leads to taking the competing depolarization by collisions with the neighboring O atoms into account, and by the competing isotropical (thus depolarizing) processes for populating the line upper level: the dissociative recombination of O2+ colliding with thermal electrons, and above all the reaction N(2D)+O2. The final diagnostic could be a density determination by depolarization, but it may be rather complicated because it involves several species.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

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