Determination of Magnetic Reconnections in a Low and a High Activity Year (original) (raw)
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An Analysis of Sources and Predictability of Geomagnetic Storms
2013
Solar transient eruptions are the main cause of interplanetary-magnetospheric disturbances leading to the phenomena known as geomagnetic storms. Eruptive solar events such as coronal mass ejections (CMEs) are currently considered the main cause of geomagnetic storms (GMS). GMS are strong perturbations of the Earth’s magnetic field that can affect space-borne and ground-based technological systems. The solar-terrestrial impact on modern technological systems is commonly known as Space Weather. Part of the research study described in this thesis was to investigate and establish a relationship between GMS (periods with Dst ≤ −50 nT) and their associated solar and interplanetary (IP) properties during solar cycle (SC) 23. Solar and IP geoeffective properties associated with or without CMEs were investigated and used to qualitatively characterise both intense and moderate storms. The results of this analysis specifically provide an estimate of the main sources of GMS during an average 11...
Geomagnetism and Aeronomy, 2011
A complex of geophysical phenomena (geomagnetic pulsations in different frequency ranges, VLF emissions, riometer absorption, and auroras) during the initial phase of a small recurrent magnetic storm that occurred on February 27-March 2, 2008, at a solar activity minimum has been analyzed. The difference between this storm and other typical magnetic storms consisted in that its initial phase developed under a pro longed period of negative IMF B z values, and the most intense wave like disturbances during the storm initial phase were observed in the dusk and nighttime magnetospheric sectors rather than in the daytime sector as is observed in the majority of cases. The passage of a dense transient (with Np reaching 30 cm -3 ) in the solar wind under the southward IMF in the sheath region of the high speed solar wind stream responsible for the discussed storm caused a great (the AE index is ~1250 nT) magnetospheric substorm. The appearance of VLF chorus, accompanied by riometer absorption bursts and Pc5 pulsations, in a very long longitudinal interval of auroral latitudes (L ~ 5) from premidnight to dawn MLT hours has been detected. It has been concluded that a sharp increase in the solar wind dynamic pressure under prolonged negative values of IMF Bz resulted in the global (in longitude) development of electron cyclotron instability in the Earth's magnetosphere.
A geomagnetic storm is a global disturbance in Earth’s magnetic field usually occurred due to abnormal conditions in the interplanetary magnetic field (IMF) and solar wind plasma emissions caused by various solar phenomenon. Furthermore the magnitude of these geomagnetic effects largely depend upon the configuration and strength of potentially geo-effective solar/interplanetary features. In the present study the identification of 220 geomagnetic storms associated with disturbance storm time (Dst) decrease of more than -50 nT to -300 nT, have been made, which are observed during 1996-2007, the time period spanning over solar cycle 23. The study is made statistically between the Dst strength (used as an indicator of the geomagnetic activity) and the peak value obtained by solar wind plasma parameters and IMF B as well as its components. We have used the hourly values of Dst index and the wind measurements taken by various satellites. Our results inferred that yearly occurrences of geo...
Within the framework of the "Space weather" program, 25-year sets of solar xray observations, measurements of plasma and magnetic field parameters in the solar wind and D st index variations are analyzed with the purpose of revealing the factors rendering the greatest influence on development of magnetospheric storms. Value of correlation between solar flares and magnetic storms (∼30%) practically does not exceed a level of correlation of random processes. Furthermore it was not possible to find out any dependence between importance of solar flares and value of magnetic storms. SOHO data on Earth-directed halo-CME for time interval 1996-2000 show that geoeffectiveness of CME is about 35-40%. The most geoeffective interplanetary phenomena are magnetic clouds (MC) which, as many believe, are interplanetary manifestations of CMEs and compressions in the region of interaction of slow and fast streams in the solar wind (so-called Corotating Interaction Region, CIR): About 2/3 of all observed magnetic storms. For storms with -100 < D st < -60 nT the numbers of storms from MC and CIR are approximately equal, and for strong storms with D st < -100 nT the part of storms from MC is considerably higher. Year numbers of storms from MC and CIR have 2 maxima per solar cycle and change in antiphase. In summary the problems of reliability of a prediction of geomagnetic disturbances on the basis of observations of the Sun and conditions in the interplanetary space are discussed.
Factors of geomagnetic storms during the solar cycles 23 and 24: A comparative statistical study
Scientific Research and Essays
The solar sources of 884 geomagnetic storms have been studied for the solar cycles 23 and 24 (1996-2019), regardless of their size ranges; using the Kp index and the NOAA G criteria (minor to extreme storms). It claims from our investigation that fast solar wind streams (HSSWs) is the main factor of small (G1) and medium (G2) storms and occur mostly on the descending phase of the solar cycle. Fast solar wind has contributed to about 59% of G1 storms; 50% of G2; 29% G3; and 10% G4 storm. Large storms (G3 to G5) are the effects of coronal mass ejections (CMEs) and they are observed mainly during the maximum and the descending phases of the solar cycle. About 10% of G1 storms, 26% of G2 storms, 59% of G3 (strong) storms, 87% of G4 (severe) storms, and 100% of G5 (extreme) storms were the effect of CMEs. Magnetic clouds contributed 11% of G1 storms, 15% of G2 storms, 9% of G3 storms, and 3% of G4 storms. A comparative statistical occurrence shows that the number of storms decreased during solar cycle 24 when compared with the solar cycle 23. These results showed that the magnetospheric energy transfer decreased in solar cycle 24 and that the magnetosphere was under the influence of intense solar magnetic fields in solar cycle 23. The phenomenon observed in these investigations highlight a drop in solar plasma geoeffectiveness since the long minimum that followed the solar cycle 23.
Journal of Space Weather and Space Climate
Extreme geomagnetic storms are considered as one of the major natural hazards for technology-dependent society. Geomagnetic field disturbances can disrupt the operation of critical infrastructures relying on space-based assets, and can also result in terrestrial effects, such as the Quebec electrical disruption in 1989. Forecasting potential hazards is a matter of high priority, but considering large flares as the only criterion for early-warning systems has demonstrated to release a large amount of false alarms and misses. Moreover, the quantification of the severity of the geomagnetic disturbance at the terrestrial surface using indices as Dst cannot be considered as the best approach to give account of the damage in utilities. High temporal resolution local indices come out as a possible solution to this issue, as disturbances recorded at the terrestrial surface differ largely both in latitude and longitude. The recovery phase of extreme storms presents also some peculiar feature...
Journal of Atmospheric and Solar-terrestrial Physics, 2010
Tremendous amount of solar energy is hurled into the space by transient sporadic emissions occurring within the Sun. A fraction of this energy is transferred into the Earth's magnetosphere by the magnetic reconnection process. Interplanetary magnetic field plays a crucial role in the excitation of geomagnetic storms and their subsequent evolution. The present study attempts to determine the influence of postshock duration of southward B z on the development and intensification of intense (Dst r À200 nT) geomagnetic storms. The study presents 18 big storm events that occurred during the solar cycle 23. In all the cases under study, the interplanetary shocks were driven by the interplanetary coronal mass ejections (ICMEs). The ICME structures may contain southward magnetic fields within the sheath, the magnetic cloud or both in succession, which can lead to the development of intense geomagnetic storms. In addition, dependence of storm strength on the total energy influx into the magnetosphere (E) and ring current (E RC ) energy is also assessed. Geomagnetic storm characteristics are examined at a lowlatitude station, Alibag (geographic lat. 18:63 3 N, long. 72:87 3 E; geomagnetic lat. 10:02 3 N, long. 145:97 3 ), using high resolution digital data. The minimum duration of southward B z for strengthening the storms is $ 1:25 h. All intense storms are found to have minimum values of southward directed B z to be r À18 nT and interplanetary electric field E y 4 12 mV=m. Intensity of geomagnetic storms at lowlatitudes follows a fairly linear dependence on the ring current energy.
Journal of Atmospheric and Solar-Terrestrial Physics, 2010
Tremendous amount of solar energy is hurled into the space by transient sporadic emissions occurring within the Sun. A fraction of this energy is transferred into the Earth's magnetosphere by the magnetic reconnection process. Interplanetary magnetic field plays a crucial role in the excitation of geomagnetic storms and their subsequent evolution. The present study attempts to determine the influence of postshock duration of southward B z on the development and intensification of intense (Dst r À200 nT) geomagnetic storms. The study presents 18 big storm events that occurred during the solar cycle 23. In all the cases under study, the interplanetary shocks were driven by the interplanetary coronal mass ejections (ICMEs). The ICME structures may contain southward magnetic fields within the sheath, the magnetic cloud or both in succession, which can lead to the development of intense geomagnetic storms. In addition, dependence of storm strength on the total energy influx into the magnetosphere (E) and ring current (E RC ) energy is also assessed. Geomagnetic storm characteristics are examined at a lowlatitude station, Alibag (geographic lat. 18:63 3 N, long. 72:87 3 E; geomagnetic lat. 10:02 3 N, long. 145:97 3 ), using high resolution digital data. The minimum duration of southward B z for strengthening the storms is $ 1:25 h. All intense storms are found to have minimum values of southward directed B z to be r À18 nT and interplanetary electric field E y 4 12 mV=m. Intensity of geomagnetic storms at lowlatitudes follows a fairly linear dependence on the ring current energy.
Geomagnetic storms, dependence on solar and interplanetary phenomena: a review
2005
Geomagnetic storms are probably the most intensively measured perturbations of the Earth's magnetic field. They are multi-faceted phenomena that result as a final element of a chain of processes that starts on the Sun, affects the solar wind and the interplanetary medium, and ends on the Earth. At present, one of the key questions in the scientific community is the ability to predict the occurrence of geomagnetic storms on the basis of solar and interplanetary space observations. For these reasons, in recent years a number of investigations have been carried out to understand the solar-terrestrial relationships and to ascertain those factors that are ultimately responsible for geomagnetic storms. Here a brief review of published results on the geomagnetic storm effectiveness from CMEs, solar flares, as well as interplanetary event observations, is presented.
Indonesian Journal of Earth Sciences/Indonesian Journal Of Earth Sciences, 2024
Geomagnetic storms (GMSs) are an important space weather phenomenon that poses serious threats to the advancement of space technology, power transmission lines, oil pipelines, and other infrastructure. This study investigates seasonal patterns of GMSs due to recent reports on the prominence of large storms (Dst ≤-50 nT) during equinox conditions. Hourly Dst index data provided by the World Data Center, Kyoto, Japan, for solar cycles 21-24 (1976-2019) were employed. Storm occurrences in each solar cycle considered were identified using the minimum Dst value. The identified storms were categorized and analyzed statistically. Results revealed that storm occurrence varied from month to month, season to season, and solar cycle to solar cycle based on storm categories. Furthermore, the observed seasonal distribution of GMS occurrence decreases in the following order: autumn, spring, winter, and summer. This indicates that equinox conditions are more likely to have GMSs, consistent with the Russell-McPherron effect, compared to solstice conditions. The findings suggest that the distribution and characterization of storm occurrence vary seasonally due to solar activity. The insights on storm occurrence, distribution, and characterization may serve as a guide to space scientists to avert the impacts of GMSs while exploring space.