DOCSLIB.ORG

Solar Activity and Transformer Failures in the Greek National Electric Grid

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Solar Activity and Transformer Failures in the Greek National Electric Grid J. Space Weather Space Clim. 3 (2013) A32 DOI: 10.1051/swsc/2013055 Ó I.P. Zois, Published by EDP Sciences 2013 RESEARCH ARTICLE OPEN ACCESS Solar activity and transformer failures in the Greek national electric grid Ioannis Panayiotis Zois* Testing Research and Standards Centre, Public Power Corporation, 9 Leontariou street, GR 153 51, Kantza, Pallini, Athens, Attica, Greece *Corresponding author: [email protected] Received 3 August 2012 / Accepted 27 October 2013 ABSTRACT Aims: We study both the short term and long term effects of solar activity on the large transformers (150 kV and 400 kV) of the Greek national electric grid. Methods: We use data analysis and various statistical methods and models. Results: Contrary to com- mon belief in PPC Greece, we see that there are considerable both short term (immediate) and long term effects of solar activity onto large transformers in a mid-latitude country like Greece. Our results can be summarised as follows: 1. For the short term effects: During 1989–2010 there were 43 ‘‘stormy days’’ (namely days with for example Ap 100) and we had 19 failures occurring during a stormy day plus or minus 3 days and 51 failures occurring during a stormy day plus or minus 7 days. All these failures can be directly related to Geomagnetically Induced Currents (GICs). Explicit cases are briefly pre- sented. 2. For the long term effects, again for the same period 1989–2010, we have two main results: (i) The annual number of transformer failures seems to follow the solar activity pattern. Yet the maximum number of transformer failures occurs about half a solar cycle after the maximum of solar activity. (ii) There is statistical correlation between solar activity expressed using various newly defined long term solar activity indices and the annual number of transformer failures. These new long term solar activity indices were defined using both local (from the geomagnetic station in Greece) and global (planetary averages) geomagnetic data. Applying both linear and non-linear statis- tical regression we compute the regression equations and the corresponding coefficients of determination. Key words. geomagnetically induced currents (GIC) – solar activity – technological system – non-linear phenomena – aeronomy 1. Introductory theory – motivation currents (GICs), ionospheric disturbances which cause radio and radar scintillation, disruption of navigation by magnetic The primary cause of space weather are explosions in the Sun compass and auroral displays at much lower latitudes than nor- powered by its strong magnetic field which affect man-made mal. In this article we shall focus on GICs and their effects on technological infrastructure in space, disturb communications electric grids, in particular large transformers. GICs are the and GPS signals and couple through Geomagnetically Induced ground level manifestations of space weather (namely geomag- Currents (GICs for short) with the large-scale high voltage netic storms) and they are driven by the variations of the terres- power grid. The most well-known case of the impact of trial magnetic field (temporary disturbances of the earth’s large-scale space weather events on the electric grid is the magnetosphere) via Faraday’s Law of Induction. 1989 Hydro-Quebec blackout caused by the 13 and 14 March One can briefly describe the emergence of GICs as a six- super storm. Highly acclaimed institutions (like the US step process (see Pulkkinen et al. 2001a, 2001b, 2003a, National Academy of Sciences 2008,theUK Royal Society 2003b, 2003c): of Engineering 2013, etc.) have issued extended reports arguing that space weather super storms may cause trillions of dollars of 1. Plasma is ejected from the Sun. damage although it is acknowledged that these estimates may 2. The magnetised plasma structures propagate in the inter- not be totally accurate. There is general consensus however that planetary medium (solar wind). space weather super storms constitute a serious threat. The main 3. Solar wind interacts with the magnetosphere. Here the cause of GICs is the interaction of the geomagnetic field with dominant factor for determining how much Earth is the magnetic field carried within CMEs and the surrounding affected is the orientation of the solar wind magnetic background magnetised solar wind that is modulated by them. field. The energy feed into the magnetosphere is highest There are several space weather phenomena which tend to during strong reconnection of the solar wind and the ter- be associated with a geomagnetic storm or are caused by a geo- restrial magnetic field. Increased energy flux into the sys- magnetic storm (see Chapman & Ferraro 1930). These include: tem sets the conditions for dynamic changes in the Solar Energetic Particle (SEP) events, geomagnetically induced magnetospheric electric current systems. One of such This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. J. Space Weather Space Clim. 3 (2013) A32 dynamic changes are magnetic storms which are charac- catastrophic failure. Moreover, the distorted output wave form terised by enhanced convection of the magnetospheric can create higher harmonics, can cause the triggering of the pro- plasma and enhanced ring current circulating the Earth tective relays (Buchholz, etc.) and various control assets may be (see, e.g., Tsurutani & Gonzalez 1997). switched out. In addition to all the above the magnetising cur- 4. Magnetosphere-ionosphere interaction. The closure of the rent can get outside the design specifications leading to magnetospheric currents goes via polar regions of the increased VAr consumption and voltage instability. Let’s ionosphere. Consequently dynamic changes in the mag- describe the situation with slightly more details. netospheric currents couple to the dynamics of the iono- GICs are driven by the variation of the (terrestrial) magnetic sphere. An important class of dynamic variations are field, so they are characterised by slow changes. A transformer auroral substorms which are related to loading-unloading core saturates under GIC bias, causing it to operate in the extre- processes in the tail of the magnetosphere (e.g., Kallio mely non-linear portion of the core steel magnetisation (B-H) et al. 2000). During auroral substorms particles injected curve. This quasi-direct current (GIC) flowing through a trans- from the tail of the magnetosphere are seen in the iono- former offsets the power frequency magnetisation curve so that sphere in terms of auroras and rapid changes in the auro- the magnetic circuit operates asymmetrically on the (B-H) ral current systems. Although some of the basic features curve. Transformers are designed to operate in the linear portion are understood, the details of the storm and substorm pro- of the curve with only a small magnetising current, without cesses as well as the storm/substorm relationship are one approaching the non-linear regions of core saturation. Even of the most fundamental open questions in the solar-ter- small GICs can produce sufficient offset for the transformer restrial physics (see Kamide & Baumjohann 1993; to reach half-cycle saturation of the ac current that is in the Kamide 2001). same direction as the GICs. As the core saturates the permeabil- 5. Rapid changes of the ionospheric and magnetospheric ity tends to 1 and the flux fills the whole space of the winding, electric currents cause variations in the geomagnetic field so it is very different from the flux distribution under normal which, according to Faraday’s law of induction, induce an conditions. Normal leakage flux is controlled by non-magnetic electric field which drives an electric current in the sub- (stainless steel or aluminium) shields, shunts or cheek plates, surface region of the Earth. The nature of this geoelectric the dimensions of which are critical for controlling eddy current field depends on the characteristics of the ionospheric- losses and heating. Under normal conditions, with most flux in magnetospheric source and on the conductivity structure the magnetic core, the non-magnetic plates carry little flux and of the Earth. As a rule of thumb, the magnitude of the generate only small losses. Under half-wave core saturation, the geoelectric field increases with increasing time deriva- losses in some parts of the leakage flux shields may increase tives of the ground magnetic field and with decreasing significantly, causing localised heating. ground conductivity. Half-wave saturation also increases the magnetising current 6. Finally, the geoelectric field drives currents within con- and distorts the magnetisation current waveform (see, e.g., ductors at and below the surface of the Earth. The mag- Takasu et al. 1994). The distorted magnetising current has nitude and distribution of the currents are dependent on harmonics that correlate well with the GIC. Without adequate the topology and electrical characteristics of the system control of the flux under saturation conditions, local heating under investigation. The induced currents flowing in tech- in parts of the transformer may not be cooled effectively, lead- nological systems on the ground are the GICs. ing to rapid temperature increase. The intensity of overheating depends on the saturation flux paths, cooling flow and the ther- From steps 3 and 4 above it is expected that the greatest mal condition or loading of the transformer.
Load more

Recommended publications
  • Statistical Properties of Superactive Regions During Solar Cycles 19–23⋆
    A&A 534, A47 (2011) Astronomy DOI: 10.1051/0004-6361/201116790 & c ESO 2011 Astrophysics Statistical properties of superactive regions during solar cycles 19–23 A. Q. Chen1,2,J.X.Wang1,J.W.Li2,J.Feynman3, and J. Zhang1 1 Key Laboratory of Solar Activity of Chinese Academy of Sciences, National Astronomical Observatories, Chinese Academy of Sciences, PR China e-mail: [email protected]; [email protected] 2 National Center for Space Weather, China Meteorological Administration, PR China 3 Helio research, 5212 Maryland Avenue, La Crescenta, USA Received 26 February 2011 / Accepted 20 August 2011 ABSTRACT Context. Each solar activity cycle is characterized by a small number of superactive regions (SARs) that produce the most violent of space weather events with the greatest disastrous influence on our living environment. Aims. We aim to re-parameterize the SARs and study the latitudinal and longitudinal distributions of SARs. Methods. We select 45 SARs in solar cycles 21–23, according to the following four parameters: 1) the maximum area of sunspot group, 2) the soft X-ray flare index, 3) the 10.7 cm radio peak flux, and 4) the variation in the total solar irradiance. Another 120 SARs given by previous studies of solar cycles 19–23 are also included. The latitudinal and longitudinal distributions of the 165 SARs in both the Carrington frame and the dynamic reference frame during solar cycles 19–23 are studied statistically. Results. Our results indicate that these 45 SARs produced 44% of all the X class X-ray flares during solar cycles 21–23, and that all the SARs are likely to produce a very fast CME.
    [Show full text]
  • Space Weather — History and Current Status
    Space Weather — History and Current Status Ji Wu National Space Science Center, CAS Oct. 3, 2017 1 Contents 1. Beginning of Space Age and Dangerous Environment 2. The Dynamic Space Environment so far We Know 3. The Space Weather Concept and Current Programs 4. Looking at the Future Space Weather Programs 2 1.Beginning of Space Age and Dangerous Environment 3 Space Age Kai'erdishi Korolev Oct. 4, 1957, humanity‘s first artificial satellite, Sputnik-1, has launched, ushering in the Space Age. 4 Space Age Explorer 1 was the first satellite of the United States, launched on Jan 31, 1958, with scientific object to explore the radiation environment of geospace. 5 Unknown Space Environment Sputnik-2 (Nov 3, 1957) detected the Earth's outer radiation belt in the far northern latitudes, but researchers did not immediately realize the significance of the elevated radiation because Sputnik 2 passed through the Van Allen belt too far out of range of the Soviet tracking stations. Explorer-1 detected fewer cosmic rays in its orbit (which ranged from 220 miles from Earth to 1,563 miles) than Van Allen expected. 6 Space Age - unknown and dangerous space environment 7 Satellite failures due to the unknown and Particle dangerous space environment Radiation！ Statistics show that the space radiation environment is one of the main causes of satellite failure. The space radiation environment caused about 2,300 satellite failures of all the 5000 failure events during the 1966-1994 period collected by the National Geophysical Data Center. Statistics of the United States in 1996 indicate that the space environment caused more than 40% of satellite failures in 1958-1986, and 36% in 1986-1996.
    [Show full text]
  • Space Weather and Aviation Impacts
    Space Weather and Aviation Impacts Char Dewey NOAA/National Weather Service Salt Lake City, UT @DeweyWx [email protected] IWAWS 2020 Space Weather and Aviation Impacts What is space weather? How space weather affects Earth and aviation; hazards and impacts How to monitor conditions and be space weather-aware Space Weather 101 Space Weather 101 Weather originating from the Sun and traveling the 93 million miles to reach Earth and our atmosphere, interacting with systems on and orbiting Earth. Observations come from satellite sources with instruments that monitor space weather. Model data (some now operational!) developing. Coronal Mass Ejections (CME), Solar Energetic Particles (SEP), and Solar Flares. Space Weather 101 Active regions on the sun are where solar activity begins; where sunspots are located on the solar disk. Magnetic “instability” where solar storming forms. Space Weather 101 Coronal Mass Ejections (CME) An eruption of plasma particles and electromagnetic radiation from the solar corona, often following solar flares. Originate from active regions on the Sun’s surface (sunspots). Very slow to reach the Earth from 12 hours to days or a week. Space Weather Impacts Coronal Mass Ejections (CME) Impacts: Geomagnetic storming compresses Earth’s magnetosphere on the day-side, extending night-side “tail” and reconnecting, focusing energy at the poles and resulting in Aurora. Increase electrons in the ionosphere at high-latitude regions, exposing to higher radiation values. Space Weather 101 Solar Energetic Particles (SEP) High-energy particles; protons, electrons Originate from solar flare or shock wave (CME) reaching the Earth from 20 minutes to many hours, depending the location it leaves the solar disk.
    [Show full text]
  • On Polar Magnetic Field Reversal in Solar Cycles 21, 22, 23, and 24
    On Polar Magnetic Field Reversal in Solar Cycles 21, 22, 23, and 24 Mykola I. Pishkalo Main Astronomical Observatory, National Academy of Sciences, 27 Zabolotnogo vul., Kyiv, 03680, Ukraine [email protected] Abstract The Sun’s polar magnetic fields change their polarity near the maximum of sunspot activity. We analyzed the polarity reversal epochs in Solar Cycles 21 to 24. There were a triple reversal in the N-hemisphere in Solar Cycle 24 and single reversals in the rest of cases. Epochs of the polarity reversal from measurements of the Wilcox Solar Observatory (WSO) are compared with ones when the reversals were completed in the N- and S-hemispheres. The reversal times were compared with hemispherical sunspot activity and with the Heliospheric Current Sheet (HCS) tilts, too. It was found that reversals occurred at the epoch of the sunspot activity maximum in Cycles 21 and 23, and after the corresponding maxima in Cycles 22 and 24, and one-two years after maximal HCS tilts calculated in WSO. Reversals in Solar Cycles 21, 22, 23, and 24 were completed first in the N-hemisphere and then in the S-hemisphere after 0.6, 1.1, 0.7, and 0.9 years, respectively. The polarity inversion in the near-polar latitude range ±(55–90)˚ occurred from 0.5 to 2.0 years earlier that the times when the reversals were completed in corresponding hemisphere. Using the maximal smoothed WSO polar field as precursor we estimated that amplitude of Solar Cycle 25 will reach 116±12 in values of smoothed monthly sunspot numbers and will be comparable with the current cycle amplitude equaled to 116.4.
    [Show full text]
  • Nonaxisymmetric Component of Solar Activity and the Gnevyshev-Ohl Rule
    Solar Physics DOI: 10.1007/•••••-•••-•••-••••-• Nonaxisymmetric Component of Solar Activity and the Gnevyshev-Ohl rule E.S.Vernova1 · M.I. Tyasto1 · D.G. Baranov2 · O.A. Danilova1 c Springer •••• Abstract The vector representation of sunspots is used to study the non- axisymmetric features of the solar activity distribution (sunspot data from Greenwich–USAF/NOAA, 1874–2016).The vector of the longitudinal asym- metry is defined for each Carrington rotation; its modulus characterizes the magnitude of the asymmetry, while its phase points to the active longitude. These characteristics are to a large extent free from the influence of a stochastic component and emphasize the deviations from the axisymmetry. For the sunspot area, the modulus of the vector of the longitudinal asymmetry changes with the 11-year period; however, in contrast to the solar activity, the amplitudes of the asymmetry cycles obey a special scheme. Each pair of cycles from 12 to 23 follows in turn the Gnevyshev–Ohl rule (an even solar cycle is lower than the following odd cycle) or the “anti-Gnevyshev–Ohl rule” (an odd solar cycle is lower than the preceding even cycle). This effect is observed in the longitudinal asymmetry of the whole disk and the southern hemisphere. Possibly, this effect is a manifes- tation of the 44-year structure in the activity of the Sun. Northern hemisphere follows the Gnevyshev–Ohl rule in Solar Cycles 12–17, while in Cycles 18–23 the anti-rule is observed. Phase of the longitudinal asymmetry vector points to the dominating (active) longitude. Distribution of the phase over the longitude was studied for two periods of the solar cycle, ascent-maximum and descent-minimum, separately.
    [Show full text]
  • Arxiv:1901.09083V2 [Astro-Ph.SR] 3 Jun 2019 2 University of Maryland, Department of Astronomy, College Park, MD 20742, USA
    Solar Physics DOI: 10.1007/•••••-•••-•••-••••-• What the Sudden Death of Solar Cycles Can Tell us About the Nature of the Solar Interior Scott W. McIntosh 1 · Robert J. Leamon 2,3 · Ricky Egeland 1 · Mausumi Dikpati 1 · Yuhong Fan 1 · Matthias Rempel 1 c Springer •••• Abstract We observe the abrupt end of solar activity cycles at the Sun's Equa- tor by combining almost 140 years of observations from ground and space. These \terminator" events appear to be very closely related to the onset of magnetic activity belonging to the next Solar Cycle at mid-latitudes and the polar-reversal process at high latitudes. Using multi-scale tracers of solar activity we examine the timing of these events in relation to the excitation of new activity and find that the time taken for the solar plasma to communicate this transition is of the order of one solar rotation { but could be shorter. Utilizing uniquely com- prehensive solar observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory (SDO) we see that this transitional event is strongly longitudinal in nature. Combined, these characteristics suggest that information is communicated through the solar interior rapidly. A range of possibilities exist to explain such behavior: for example gravity waves on the solar tachocline, or that the magnetic fields present in the Sun's convection zone could be very large, with a poloidal field strengths reaching 50 kG { considerably larger than conventional explorations of solar and stellar dynamos estimate. Regardless of the mechanism responsible, the rapid timescales demonstrated by the Sun's global magnetic field reconfiguration present strong constraints on first-principles numerical simulations of the solar interior and, by extension, other stars.
    [Show full text]
  • SOLAR CYCLE 23: an ANOMALOUS CYCLE? Giuliana De Toma and Oran R
    The Astrophysical Journal, 609:1140–1152, 2004 July 10 # 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A. SOLAR CYCLE 23: AN ANOMALOUS CYCLE? Giuliana de Toma and Oran R. White High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80301; [email protected], [email protected] and Gary A. Chapman, Stephen R. Walton, Dora G. Preminger, and Angela M. Cookson San Fernando Observatory, Department of Physics and Astronomy, California State University at Northridge, 18111 Nordhoff Street, Northridge, CA 91330; [email protected], [email protected], [email protected], [email protected] Received 2004 January 24; accepted 2004 March 19 ABSTRACT The latest SOHO VIRGO total solar irradiance (TSI) time series is analyzed using new solar variability measures obtained from full-disk solar images made at the San Fernando Observatory and the Mg ii 280 nm index. We discuss the importance of solar cycle 23 as a magnetically simpler cycle and a variant from recent cycles. Our results show the continuing improvement in TSI measurements and surrogates containing infor- mation necessary to account for irradiance variability. Use of the best surrogate for irradiance variability due to photospheric features (sunspots and faculae) and chromospheric features (plages and bright network) allows fitting the TSI record to within an rms difference of 130 ppm for the period 1986 to the present. Observations show that the strength of the TSI cycle did not change significantly despite the decrease in sunspot activity in cycle 23 relative to cycle 22. This points to the difficulty of modeling TSI back to times when only sunspot observations were available.
    [Show full text]
  • Statistics of the Largest Geomagnetic Storms Per Solar Cycle (1844-1993) D
    Statistics of the largest geomagnetic storms per solar cycle (1844-1993) D. M. Willis, P. R. Stevens, S. R. Crothers To cite this version: D. M. Willis, P. R. Stevens, S. R. Crothers. Statistics of the largest geomagnetic storms per solar cycle (1844-1993). Annales Geophysicae, European Geosciences Union, 1997, 15 (6), pp.719-728. hal-00316271 HAL Id: hal-00316271 https://hal.archives-ouvertes.fr/hal-00316271 Submitted on 1 Jan 1997 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Ann. Geophysicae 15, 719±728 (1997) Ó EGS ± Springer-Verlag 1997 Statistics of the largest geomagnetic storms per solar cycle (1844±1993) D. M. Willis1,*, P. R. Stevens1,2, S. R. Crothers1 1 Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK 2 Holmes Chapel Comprehensive School, Holmes Chapel, Crewe, Cheshire CW4 7DX, UK Received: 8 January 1996 / Revised: 1 December 1996 / Accepted: 20 January 1997 Abstract. A previous application of extreme-value sta- satisfy the condition aa < 550 for the largest geomag- tistics to the ®rst, second and third largest geomagnetic netic storm in the next 100 solar cycles. The statistical storms per solar cycle for nine solar cycles is extended to analysis is used to infer that remarkable conjugate fourteen solar cycles (1844±1993).
    [Show full text]
  • Solar Cycle Predictions
    LOGO.049 Goddard Space Flight Center Solar Cycle Predictions W. Dean Pesnell NASA, Goddard Space Flight Center LOGO.049 Goddard Space Flight Center What should Space Weather predict? What kinds of predictions are there? For long-term work we usually report predictions of sunspot number (RZ). How well have we done at predicting RZ? What can we do better? LOGO.049 What is a Sunspot? Goddard Space Flight Center RZ = 93! 2014. 2014. - Oct - HMI Image with AR 12192 from 24 from 12192 AR with Image HMI LOGO.049 What is a Sunspot? Goddard Space Flight Center Granulation Penumbra 2014. 2014. - Oct Light bridge - Umbra HMI Image with AR 12192 from 24 from 12192 AR with Image HMI LOGO.049 First Prediction was at Discovery Goddard Space Flight Center Schwabe noted a 10-year period in his observed sunspot count. He also noted that sunspot number should increase if he was correct. “The next few Samuel Heinrich Schwabe years will show whether or not this period (Dessau, 1789–1875) persists in the sunspot record.” LOGO.049 Mathematicians like Predictions Goddard Space Flight Center Yule treated RZ as data to test prediction techniques. He developed autoregression to predict RZ better than periodograms. George Udny Yule, 1871-1951 LOGO.049 Chaos ≠ Unpredictable Goddard Space Flight Center Mandelbrot and collaborators used RZ as data to test chaos-oriented prediction techniques. He showed RZ can be predicted better than white noise (Hurst exponent of white noise is 0.5.) Benoit Mandelbrot, 1924-2010 LOGO.049 Goddard Space Flight Center What Kinds of Predictions?
    [Show full text]
  • The New Grand Minimum New Skills Have Been Developed by Actuaries If They Are to Understand the Changes in Risks That Are Occurring in the New Solar Grand Minimum
    The New Grand Minimum New Skills have been developed by actuaries if they are to understand the changes in risks that are occurring in the new solar grand minimum. Prepared by Brent Walker Presented to the Actuaries Institute Actuaries Summit 20-21 May 2013 Sydney This paper has been prepared for Actuaries Institute 2013 Actuaries Summit. The Institute Council wishes it to be understood that opinions put forward herein are not necessarily those of the Institute and the Council is not responsible for those opinions. The Institute will ensure that all reproductions of the paper acknowledge the Author/s as the author/s, and include the above copyright statement. Institute of Actuaries of Australia ABN 69 000 423 656 Level 7, 4 Martin Place, Sydney NSW Australia 2000 t +61 (0) 2 9233 3466 f +61 (0) 2 9233 3446e [email protected] w www.actuaries.asn.au Brent Walker - May 2013 Table of Contents Introduction ............................................................................................................................................ 3 New Solar Grand Minimum ................................................................................................................ 3 History of Solar Activity over Last Millennium .................................................................................... 3 International Panel on Climate Change View ..................................................................................... 5 Use of Predictive Models ...................................................................................................................
    [Show full text]
  • Magnetic Storm and Solar Cycle Dependences
    PUBLICATIONS Journal of Geophysical Research: Space Physics RESEARCH ARTICLE Supersubstorms (SML<À2500nT): Magnetic storm 10.1002/2015JA021835 and solar cycle dependences Key Points: Rajkumar Hajra1,2, Bruce T. Tsurutani3, Ezequiel Echer1, Walter D. Gonzalez1, and Jesper W. Gjerloev4,5 • Extremely intense substorms/ supersubstorms are often isolated 1Instituto Nacional de Pesquisas Espaciais, São José dos Campos, São Paulo, Brazil, 2Now at Laboratoire de Physique et events and are not obvious statistical ’ ’ 3 fluctuations of the geomagnetic Chimie de l Environnement et de l Espace, CNRS, Orléans, France, Jet Propulsion Laboratory, California Institute of 4 indices Technology, Pasadena, California, USA, The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA, • Supersubstorm occurrence and 5Birkeland Center, University of Bergen, Bergen, Norway intensity have no obvious relationship with geomagnetic storm intensity • Supersubstorms exhibit annual Abstract We study extremely intense substorms with SuperMAG AL (SML) peak intensities < À2500 nT variation with peak occurrence during “ ” spring in SC 22 and fall in SC 23 ( supersubstorms /SSSs) for the period from 1981 to 2012. The SSS events were often found to be isolated SML peaks and not statistical fluctuations of the indices. The SSSs occur during all phases of the À solar cycle with the highest occurrence (3.8 year 1) in the descending phase. The SSSs exhibited an annual variation with equinoctial maximum altering between spring in solar cycle 22 and fall in solar Correspondence to: R. Hajra, cycle 23. The occurrence rate and strength of the SSSs did not show any strong relationship with the [email protected] intensity of the associated geomagnetic storms.
    [Show full text]
  • Solar Cycle Related Variation in Solar Differential Rotation and Meridional
    Solar Cycle Related Variation in Solar Differential Rotation and Meridional Flow in Solar Cycle 24 Shinsuke Imada ( [email protected] ) https://orcid.org/0000-0001-7891-3916 Kengo Matoba ISEE, Nagoya University Masashi Fujiyama Nagoya Daigaku Haruhisa Iijima Nagoya Daigaku Full paper Keywords: solar surface ow, solar cycle Posted Date: November 6th, 2020 DOI: https://doi.org/10.21203/rs.3.rs-29415/v3 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Version of Record: A version of this preprint was published on November 26th, 2020. See the published version at https://doi.org/10.1186/s40623-020-01314-y. Solar Cycle Related Variation in Solar Differential Rotation and Meridional Flow in Solar Cycle 24 Shinsuke Imada, Institute for Space-Earth Environmental Research, Nagoya University, Aichi 464-8601, Japan, [email protected] Kengo Matoba, Institute for Space-Earth Environmental Research, Nagoya University, Aichi 464-8601, Japan, [email protected] Masashi Fujiyama, Institute for Space-Earth Environmental Research, Nagoya University, Aichi 464-8601, Japan Haruhisa Iijima, Institute for Space-Earth Environmental Research, Nagoya University, Aichi 464-8601, Japan, [email protected] Preprint submitted to Earth, Planets and Space on October 27, 2020 1 Abstract We studied temporal variation of the differential rotation and poleward meridional circulation during solar cycle 24 using the magnetic element feature tracking technique. We used line-of-sight magnetograms obtained using the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory from May 01, 2010 to March 26, 2020 (for almost the entire period of solar cycle 24, Carrington Rotation from 2096 to 2229) and tracked the magnetic element features every 1 hour.
    [Show full text]