DOCSLIB.ORG

Forecasting the Arrival of Shockaccelerated Solar Energetic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Forecasting the Arrival of Shockaccelerated Solar Energetic JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. A10, PAGES 20,979-20,983, OCTOBER 1, 2001 Forecasting the arrival of shock-accelerated solar energetic particles at Earth C. M. S. Cohen, R. A. Mewaldt, A. C. Cummings, R. A. Leske, and E. C. Stone Califomia Instituteof Technology,Pasadena, California P. L. Slocum and M. E. Wiedenbeck Jet PropulsionLaboratory, Califomia Instituteof Technology.Pasadena, California E. R. Christianand T. T. von Rosenvinge NASA GoddardSpace Flight Center,Greenbelt, Maryland Abstract. Energeticparticles accelerated at interplanetaryshocks can result in an increased radiation dose for astronauts as well as an increased risk to satellite hardware. These shocks are known to occasionallyaccelerate protons to energiesgreater than 100 MeV and can resultin very high fluxes. Advancedwarning of the arrival of stronginterplanetary shocks can enablesteps to be takento minimize the potentialrisks. In an effort to monitor and assessthe radiationrisk to astronauts,two real-time countrate monitorswere implemented in the Solar IsotopeSpectrometer (SIS) on the ACE spacecraft.These ratesmeasure protonswith energies>10 and >30 MeV. Since ACE is locatedat the L1 Lagrangianpoint, theserates provide information and warning up to 1 hour beforean interplanetaryshock reachesEarth. Using ACE and GOES, data we have examinedexamples of shocksand associatedenergetic particles that have been detectedat ACE and were later observednear Earth in an effort to developmore fully the forecastingcapability of ACE. Becauseof the limited amountof solaractivity during 1997-1999, this currentwork is primarily a proof of concept. 1. Introduction magnetosphere[Shea et al., 1999]. The sameshocks which Recently, the Committee on Solar and Space Physics compressthe magnetospherein these geomagneticstorms (CSSP) and the Committee on Solar-Terrestrial Relations may acceleratesubstantial numbers of protons(and heavier ions) to energies greater than 100 MeV. Such local (CSTR) examined the risk of increased radiation hazards to acceleration(as well as turbulencenear the shock,which can astronautsworking on the International Space Station ([SS). confine the particlesto the shock region) can result in The results of the study were published in the report intensities at the shock which temporarily dominate an "Radiation and the International Space Station: Recommendations to Reduce Risk" and indicated that there is ongoingsolar energetic particle (SEP) event,as wasthe case duringthe October19, 1989,SEP event. Duringthe decline a significantprobability that severalconstruction flights of the of this event,the passageof the associatedshock resulted in a ISS could be impacted by penetrating particle radiation greater than fivefold increase in >100 MeV protons as events. Of primary concernto the astronautsare events with measuredby the GOES 7 spacecraft(Figure 1). Since the significant fluxes of >10 MeV/nucleon particles. During time profile of particle intensities in a typical SEP event these events, astronauts could experience a significantly decaysrelatively smoothly(especially at E > 100 MeV), such increasedradiation dose (especially if they are perforlning an increase during the decay phase is unexpected and extravehicularactivity), possiblyaffecting their future health and flight schedules.Additionally, increasedexposure could therefore would not be predictedwithout information about requiremore frequentrotation of the crews,thereby impacting the arriving shock. Forehandknowledge of such a situation spacestation schedules and costs. would allow astronautsto move to more protectedareas of the The radiation hazard can be especially high when a ISS or to rescheduleplanned extravehicular activities. suppressionof the geomagneticcutoff is coincidentwith high A large effort was made in the 1980sto understandshocks fluxes of energeticparticles [Leske et al., this issue]. The and their accelerationof particles to MeV energies. It was found that shockscan be divided into two broad categories, geomagneticcutoff is suppressedduring geomagneticstorms when a favorable orientation of the interplanetary magnetic parallel (where the angle betweenthe shocknormal and the field is combinedwith increasedsolar wind pressureon the magneticfield, O•, is 00-45ø) and perpendicular(where Ot• is 45ø-90ø). At parallel shocks,ions gain energythrough Fermi Copyright2001 by the AmericanGeophysical Union. acceleration,a processwhere the ions are reflectedby waves upstreamand downstream of the shock. Sincethe wave fields Papernumber 2000JA000216. are converging,the particles are being reflected by moving 0148-0227/01/2000JA000216509.00 barriers and thus gain energy. The more times an ion is 20,979 20,980 COHEN ET AL.: BRIEF REPORT 2. Instrumentation and Data Selection The Solar IsotopeSpectrometer (SIS) on ACE measures o• energeticions from -10 to 100MeV/nucleon [Stone et al., 1998b]. A stackof large-areasilicon detectors is usedto determinethe kinetic energy,nuclear charge, and massof incomingparticles. The largegeometry factor of SIS allows 02 measurementsof low fluxes of heavy ions to be made with goodtemporal resolution. These measurements require trajectoryinformation which is obtainedfrom the top two 0 ø detectors,which are positionsensitive. While energetic ß protonstypically do not depositenough energy in these detectorsto exceed the set thresholds(which are optimized -• ..... • I I for higher-Zparticles), the energythresholds of single 292 294 296 298 300 detectorsdeeper in the stack are low enoughthat the Doy of 1989 associatedsingle-detector rates are dominated by protons. Figure 1. GOES 7 fluxes of >10, >30, and >100 MeV protons Shortlybefore launch, provisions were made to include during the eventsof October 1989. two such rates from SIS among those telemetered continuouslyas partof theReal Time Solar Wind monitoring systemon ACE [Zwicklet al., 1998]. Thesetwo ratesare the reflected,the more energy it gains. At perpendicularshocks, countingrates of the singleT4 detectorand the coincidence betweenthe T6 and T7 detectors(Figure 2). The T4 and shock drift accelerationis the primary processinvolved. In T6oT7 ratesrespond primarily to >10 and>30 MeV protons, this case the particlesdrift accordingto v x B forces in the direction of the induced electric field at the shock and are respectively,similar to the I3 and I4 rateson the GOES accelerated.The more time the particlespends near the shock spacecratl.Increases in theseSIS rates due to a passingshock shouldbe followedby correspondingincreases in the GOES (under the influence of the electric field), the more energy it rates when the shock reaches GOES. gains. In both casesthe amount of energy a particle gains In an effort to study this correlationand develop the dependson Ot• and the speed of the shock. In shock drift accelerationthe energy gain also dependson the pitch angle capabilityfor near-real-timeutilization of the SIS ratesin a warningsystem, we have examinedthe dataobtained since of the ion. Comprehensiveoverviews of both types of shock launchin August1997 throughDecember 1999 for shock- accelerationhave been presentedby Armstronget al. [ 1985] related increases in the T4 rate. An indication that the and Scholer [ 1985]. increases are a result of local shock acceleration is that both Unfortunately, althoughthe general accelerationprocesses have been established, the details of shock acceleration of energetic particles and their subsequenttransport involve a number of interplanetaryparameters, and it is hard for particle acceleration events such as that of October 19, 1989, to be '% II ', entrance ,' II accurately forecast from observations of the coronal mass ejections(CMEs) typically driving the shocks[Feynman and o,. 75 ", ,'• M1 Gabriel 2000]. It is also difficult to predictfrom observations of eruptingCMEs whether a shockwill developthat will still be capable of acceleratingsignificant numbersof particles when it arrives at Earth. Kahler et al. [1984] found a significantcorrelation between the speedof CMEs observed with the Solwind coronagraph and the associatedproton fluxes measured by the IMP 8 and ISEE 3 spacecraft. However, for a given CME speedthe observedproton fluxes 75" "M2 varied from event to event by as much as 4 orders of 100 T1 magnitude[see Kahler et al., 1984; Figure 5]. 100 T2 250 13 The Advanced CompositionExplorer (ACE) [Stone et al., 5OO T4 1998a], at the L 1 Lagrangianpoint, is far enoughupstream of 75O T5 the Earth that it can provide advancedwarnings (---1 hour) of 2650• incoming shocks. Since few shocks are strong enough to accelerate particles to high energies, it is not adequate to merely observethe shock at L1. A measureof the energetic particleslocally acceleratedby the shockwhen it passesACE 1 ooo , T8 is needed for a reasonable indication of what will occur-when I I the shock reaches Earth. The Real-Time Solar Wind i cm monitoring system [Zwickl et al., 1998], 'which is a Figure 2. Schematicof the Solar IsotopeSpectrometer (SIS; one compilation of ACE measurementstelemetered in near real of two telescopes). Two real-time rates are derived from the time, providesthe necessaryinformation for monitoringshock single T4 detector and the coincidence of the T6 and T7 events. detectors. COHEN ET AL ß BRIEF REPORT 20,981 the T4 and T6.T? rates rise togetherwith negligible energy plottedin Figure3. Shocksidentified by the MAG and dispersion.Energy dispersion is typicalof SEPevents with SWEPAM teams (C. Smith, private communication,2000) accelerationoccurring near the Sun, sincethe higher-energy
Load more

Recommended publications
  • Ultraviolet and Extreme Ultraviolet Spectroscopy of the Solar Corona at the Naval Research Laboratory
    F222 Vol. 54, No. 31 / November 1 2015 / Applied Optics Research Article Ultraviolet and extreme ultraviolet spectroscopy of the solar corona at the Naval Research Laboratory 1, 1 1 2 1 1 J. D. MOSES, * Y.-K. KO, J. M. LAMING, E. A. PROVORNIKOVA, L. STRACHAN, AND S. TUN BELTRAN 1Space Science Division, Naval Research Laboratory, 4555 Overlook Avenue S.W., Washington DC 20375, USA 2University Corporation for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307, USA *Corresponding author: [email protected] Received 8 June 2015; revised 3 August 2015; accepted 17 August 2015; posted 18 August 2015 (Doc. ID 242463); published 17 September 2015 We review the history of ultraviolet and extreme ultraviolet spectroscopy with a specific focus on such activities at the Naval Research Laboratory and on studies of the extended solar corona and solar-wind source regions. We describe the problem of forecasting solar energetic particle events and discuss an observational technique designed to solve this problem by detecting supra-thermal seed particles as extended wings on spectral lines. Such seed particles are believed to be a necessary prerequisite for particle acceleration by heliospheric shock waves driven by a coronal mass ejection. OCIS codes: (300.2140) Emission; (300.6540) Spectroscopy, ultraviolet; (350.1270) Astronomy and astrophysics; (350.6090) Space optics. http://dx.doi.org/10.1364/AO.54.00F222 1. INTRODUCTION with the launch of the Solar and Heliospheric Observatory [3] Many activities of the sun that affect the terrestrial environment (SoHO) in 1995, and the Solar Terrestrial Relations Observatory [4] (STEREO) in 2006.
    [Show full text]
  • Kein Folientitel
    The Solar Origins of Space Weather STP-10/CEDAR 2001 Joint Meeting June 17 to 22, 2001 Longmont, Colorado Rainer Schwenn Max-Planck-Institut für Aeronomie Katlenburg-Lindau Space Weather! Northern lights, Aurora! Space “storms” may cause severe damage to, e.g., power systems on earth! The Sun as the driver of Space Weather Major geomagnetic storms may cause •bright aurorae, down to low latitudes, •damage to high voltage lines in arctic regions, •anomalous corrosion of oil pipelines in arctic regions, •damage to long distance communication cables, •malfunction of magnetic compasses, •damage to satellites and satellite systems, •effects on biological systems. The Sun’s huge atmosphere, the “corona” Eclipse and LASCO-C2 coronagraph images processed and merged by Serge Koutchmy The Sun’s corona, well-known from eclipses The eclipse of 30.6.1973, recorded and processed by S. Koutchmy. The corona evaporates the “solar wind” Never seen before: the „smoke clouds“ near the equatorial plane are due to inhomogeneities in the solar wind, which thus becomes visible Note further: • The moving star field, • Our milky way which the sun traverses righ at Christmas, • A little comet plunging into the sun and evaporating Christmas 1996: LASCO-C3 shows the sun (though occulted) as a star amongst others in its own galaxy, the milky way! Tw o types of coron a and so wind lar Coronal “holes” were discovered in green light and in X-rays Yohkoh SXT 3-5 Million K Tw o types of coron a and so wind lar Coronal holes are apparent in all “hot” coronal emission lines EIT: 19.5 nm 1.5 Million K The two states of corona and solar wind Note the coronal hole edges: they transform nicely into stream boundaries The corona of the active sun (1998), viewed by EIT and LASCO-C1/C2 The “quiet” Sun and its minimum corona LASCO C1/C2, on 1.2.
    [Show full text]
  • Space) Barriers for 50 Years: the Past, Present, and Future of the Dod Space Test Program
    SSC17-X-02 Breaking (Space) Barriers for 50 Years: The Past, Present, and Future of the DoD Space Test Program Barbara Manganis Braun, Sam Myers Sims, James McLeroy The Aerospace Corporation 2155 Louisiana Blvd NE, Suite 5000, Albuquerque, NM 87110-5425; 505-846-8413 [email protected] Colonel Ben Brining USAF SMC/ADS 3548 Aberdeen Ave SE, Kirtland AFB NM 87117-5776; 505-846-8812 [email protected] ABSTRACT 2017 marks the 50th anniversary of the Department of Defense Space Test Program’s (STP) first launch. STP’s predecessor, the Space Experiments Support Program (SESP), launched its first mission in June of 1967; it used a Thor Burner II to launch an Army and a Navy satellite carrying geodesy and aurora experiments. The SESP was renamed to the Space Test Program in July 1971, and has flown over 568 experiments on over 251 missions to date. Today the STP is managed under the Air Force’s Space and Missile Systems Center (SMC) Advanced Systems and Development Directorate (SMC/AD), and continues to provide access to space for DoD-sponsored research and development missions. It relies heavily on small satellites, small launch vehicles, and innovative approaches to space access to perform its mission. INTRODUCTION Today STP continues to provide access to space for DoD-sponsored research and development missions, Since space first became a viable theater of operations relying heavily on small satellites, small launch for the Department of Defense (DoD), space technologies have developed at a rapid rate. Yet while vehicles, and innovative approaches to space access.
    [Show full text]
  • From the Heliosphere Into the Sun Programme Book Incuding All
    511th WE-Heraeus-Seminar From the Heliosphere into the Sun –SailingagainsttheWind– Programme book incuding all abstracts Physikzentrum Bad Honnef, Germany January 31 – February 3, 2012 http://www.mps.mpg.de/meetings/heliocorona/ From the Heliosphere into the Sun A meeting dedicated to the progress of our understanding of the solar wind and the corona in the light of the upcoming Solar Orbiter mission This meeting is dedicated to the processes in the solar wind and corona in the light of the upcoming Solar Orbiter mission. Over the last three decades there has been astonishing progress in our understanding of the solar corona and the inner heliosphere driven by remote-sensing and in-situ observations. This period of time has seen the first high-resolution X-ray and EUV observations of the corona and the first detailed measurements of the ion and electron velocity distribution functions in the inner heliosphere. Today we know that we have to treat the corona and the wind as one single object, which calls for a mission that is fully designed to investigate the interwoven processes all the way from the solar surface to the heliosphere. The meeting will provide a forum to review the advances over the last decades, relate them to our current understanding and to discuss future directions. We will concentrate one day on in- situ observations and related models of the inner heliosphere, and spend another day on remote sensing observations and modeling of the corona – always with an eye on the symbiotic nature of the two. On the third day we will direct our view towards the future.
    [Show full text]
  • University of Florida Thesis Or Dissertation Formatting Template
    DESIGN OF A REPRESENTATIVE LEO SATELLITE AND HYPERVELOCITY IMPACT TEST TO IMPROVE THE NASA STANDARD BREAKUP MODEL By SHELDON COLBY CLARK A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2013 1 © 2013 Sheldon C. Clark 2 To my family - forever first and foremost - for making me who I am today and supporting me unconditionally through all of my endeavors. To my friends, colleagues, and advisors who have accompanied me on my journey – I am forever grateful. 3 ACKNOWLEDGMENTS I would like to thank all those who have given me the opportunity to grow to the person I am today. I thank my parents and family for their unconditional love and support. I am grateful to Dr. Norman Fitz-Coy for the learning opportunities he has provided and the guidance he has shared with me. I also thank my longtime friends, my colleagues in the Space Systems Group, and my peers at the University of Florida for their support and help through the years. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 LIST OF ABBREVIATIONS ..........................................................................................
    [Show full text]
  • Solar Activity and Its Evolution Across the Corona: Recent Advances
    J. Space Weather Space Clim. 3 (2013) A18 DOI: 10.1051/swsc/2013039 Ó F. Zuccarello et al., Published by EDP Sciences 2013 RESEARCH ARTICLE OPEN ACCESS Solar activity and its evolution across the corona: recent advances Francesca Zuccarello1,*, Laura Balmaceda2, Gael Cessateur3, Hebe Cremades4, Salvatore L. Guglielmino5, Jean Lilensten6, Thierry Dudok de Wit7, Matthieu Kretzschmar7, Fernando M. Lopez2, Marilena Mierla8,9,10, Susanna Parenti8, Jens Pomoell11, Paolo Romano5, Luciano Rodriguez8, Nandita Srivastava12, Rami Vainio11, Matt West8, and Francesco P. Zuccarello13 1 Dipartimento di Fisica e Astronomia, Sez. Astrofisica, Universita` di Catania, Via S. Sofia 78, 95123 Catania, Italy *Corresponding author: [email protected] 2 Instituto de Ciencias Astrono´micas, de la Tierra y el Espacio, ICATE-CONICET, Av. Espan˜a Sur 1512, J5402DSP, San Juan, Argentina 3 Physical-Meteorological Observatory/World Radiation Center, Davos, Switzerland 4 Universidad Tecnolo´gica Nacional – Facultad Regional Mendoza/CONICET, Rodrı´guez 273, M5502AJE, Mendoza, Argentina 5 INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123, Catania, Italy 6 UJF-Grenoble 1/CNRS-INSU, Institut de Plane´tologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France 7 LPC2E/CNRS (UMR 7328) and University of Orle´ans, 3A avenue de la Recherche Scientifique, 45071 Orle´ans Cedex 2, France 8 Solar – Terrestrial Center of Excellence – SIDC, Royal Observatory of Belgium, Av. Circulaire 3, 1180 Brussels, Belgium 9 Institute of Geodynamics
    [Show full text]
  • The High Energy Telescope for STEREO
    Space Sci Rev (2008) 136: 391–435 DOI 10.1007/s11214-007-9300-5 The High Energy Telescope for STEREO T.T. von Rosenvinge · D.V. Reames · R. Baker · J. Hawk · J.T. Nolan · L. Ryan · S. Shuman · K.A. Wortman · R.A. Mewaldt · A.C. Cummings · W.R. Cook · A.W. Labrador · R.A. Leske · M.E. Wiedenbeck Received: 1 May 2007 / Accepted: 18 December 2007 / Published online: 14 February 2008 © Springer Science+Business Media B.V. 2008 Abstract The IMPACT investigation for the STEREO Mission includes a complement of Solar Energetic Particle instruments on each of the two STEREO spacecraft. Of these in- struments, the High Energy Telescopes (HETs) provide the highest energy measurements. This paper describes the HETs in detail, including the scientific objectives, the sensors, the overall mechanical and electrical design, and the on-board software. The HETs are designed to measure the abundances and energy spectra of electrons, protons, He, and heavier nuclei up to Fe in interplanetary space. For protons and He that stop in the HET, the kinetic energy range corresponds to ∼13 to 40 MeV/n. Protons that do not stop in the telescope (referred to as penetrating protons) are measured up to ∼100 MeV/n, as are penetrating He. For stop- ping He, the individual isotopes 3He and 4He can be distinguished. Stopping electrons are measured in the energy range ∼0.7–6 MeV. Keywords Space instrumentation · STEREO mission · Energetic particles · Coronal mass ejections · Particle acceleration PACS 96.50.Pw · 96.50.Vg · 96.60.ph Abbreviations 2-D Two dimensional ACE Advanced Composition Explorer ACRs Anomalous Cosmic Rays ADC Analog to Digital Converter T.T.
    [Show full text]
  • Statistical Analysis of Dynamical Parameters of Solar Ejections Observed from 1996 to 2006
    358 RevistaMuñoz Mexicanaet al. de Ciencias Geológicas, v. 27, núm. 2, 2010, p. 358-365 Statistical analysis of dynamical parameters of solar ejections observed from 1996 to 2006 Guadalupe Muñoz1,2,3,*, Bernardo Vargas2, and José Luis López-López4 1Escuela Superior de Ingeniería Mecánica y Eléctrica, Instituto Politécnico Nacional, Av. IPN s/n, Unidad Profesional Adolfo López Mateos, Edificio 2, Col. Lindavista, Del. Gustavo A. Madero, 07738 México D. F., Mexico. 2Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Del. Coyoacán, 04510 México D. F., Mexico. 3Instituto Max Planck para Investigaciones del Sistema Solar, Max-Planck Str. 2, 37191, Katlenburg-Lindau, Germany. 4Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Av. IPN s/n, Unidad Profesional Adolfo López Mateos, Edificio 9, Col. Lindavista, Del. Gustavo A. Madero, 07738 México D. F., Mexico. * [email protected] ABSTRACT In this work we show a statistical analysis of the main parameters of solar ejections observed from January 1996 to December 2006 and reported on the SoHO-LASCO CME Catalog by the Coordinated Data Analysis Workshops (CDAW); this catalog contains the most complete data bank of coronal mass ejections (CMEs) ever compiled. The parameters of the CMEs analyzed are: angular position, angular width, speed and acceleration. For them, we obtained the distribution for each parameter and their representative values in order to characterize CMEs during solar cycle 23. These values are compared with the ones reported by previous analyses; we found that extreme values (maximum and minimum) are, for this sample, even more extremes. We discuss some specific cases from where can be shown that such extreme values correspond not only to a higher sensibility of the instruments, but to an overestimation of the values, and the consideration of events that are not properly CMEs.
    [Show full text]
  • –1– Photometric Study of the Kreutz Comets Observed by SOHO from 1996–2005 Matthew M. Knight1,2, Michael F. A'hearn3, Do
    – 1 – Photometric Study of the Kreutz Comets Observed by SOHO from 1996–2005 Matthew M. Knight1,2, Michael F. A’Hearn3, Douglas A. Biesecker4, Guillaume Faury5, Douglas P. Hamilton3, Philippe Lamy5, Antoine Llebaria5 Contacting author: [email protected] Astronomical Journal revised version Accepted January 5, 2010 Manuscript pages: 71 pages text (double spaced) 5 tables 16 figures 1Lowell Observatory, 1400 W. Mars Hill Rd, Flagstaff, AZ 86001 2Work completed while at the University of Maryland. 3Department of Astronomy, University of Maryland, College Park, MD 20742-2421 4NOAA Space Weather Prediction Center, 325 Broadway, Boulder, CO 80305 5Laboratoire d’Astronomie Spatiale, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13, France – 2 – Proposed running head: SOHO Observed Kreutz Comets 1996–2005 Please address all editorial correspondence and proofs to: Matthew M. Knight Lowell Observatory 1400 W. Mars Hill Rd Flagstaff, AZ 86001 [email protected] Office: 928-774-3358 Fax: 928-774-6296 – 3 – Abstract We present analysis of the photometry of more than 900 Kreutz comets observed by SOHO from 1996–2005. The Kreutz comets have “sungrazing” orbits with q≈1–2 R , high inclinations (i≈143◦), and periods of 500–1000 years. We find that they do not have a bimodal distance of peak brightness as previously reported, but instead peak from 10.5–14 R (prior to perihelion), suggesting there is a continuum of compositions rather than two distinct subpopulations. The lightcurves have two rates of brightening, typically ∝r−7.3±2.0 when −3.8±0.7 first observed by SOHO (at distances of 30–35 R ) then rapidly transitioning to ∝r between 20–30 R .
    [Show full text]
  • Coronal Mass Ejections
    1998 CEDAR Workshop Boulder, Colorado June 7-12.1998 Coronal Mass Ejections Tutorial Lecture by A. J. Hundhausen High Altitude Observatory NCAR CEDAR Presentationon Coronal Mass Ejections I. Introduction A. Coronal mass ejections are spectacular (even beautiful) disruptions of the solar corona (Figure 1) - but what on earth are they doing at a CEDAR meeting? 1. Ultimate responsibility rests on organizers 2. But my answer to this question would involve a. Culture b. Physics (and chemistry) - the same laws apply on the sun and on the earth c. The solar-terrestrial connection (Figure 2) B. Approach in this presentation 1. Large body of observational/empirical knowledge 2. Description of mass ejections based on that knowledge a. Role of theoretical models in i. Sharpening the description ii. Making it a physical description based on known physical processes b. Remaining crucial gaps that compromise the description 3. Get to key issues or questions regarding a. The origin(s) of mass ejections b. The interplanetary and terrestrial effects of coronal mass ejections 4. These two foci are related to recent fame (or notoriety) of mass ejections in contexts of a. "The Solar Flare Myth" b. "Space Weather" II. Observational/empirical foundations A. Mass ejections have been observed by the thousands since discovery about 25 years ago (Figures 3,4,5) 1. Occur in a highly structured background corona a. Eclipse photo shows that structure (Figure 6) b. Interpretation as magnetically-dominated equilibrium between plasma and field with both open and closed magnetic regions (Figure 7) 2. Many beautiful mass ejections that give special insights, are starting point for interpretation a.
    [Show full text]
  • Correlation Between Halo Coronal Mass Ejections and Solar Surface Activity?
    A&A 397, 1057–1067 (2003) Astronomy DOI: 10.1051/0004-6361:20021463 & c ESO 2003 Astrophysics Correlation between halo coronal mass ejections and solar surface activity? Guiping Zhou1;2, Jingxiu Wang1, and Zhuoliang Cao2 1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: [email protected]; [email protected] 2 Department of Physics, AnHui University, HeFei 230039, PR China e-mail: [email protected] Received 22 May 2002 / Accepted 17 September 2002 Abstract. We survey all the coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph Experiment (LASCO) aboard the Solar & Heliospheric Observatory (SOHO) in the interval from 1997 to 2001, and select 197 frontside halo CMEs whose associated near-surface activity could be clearly identified from SOHO EUV Imaging Telescope (EIT) and other space-borne and ground-based observations. A statistical analysis has been made with the emphasis on the correlation between CMEs and solar surface activity. We have found in our sample that all the CMEs were accompanied by local brightening in the CME source regions in EIT and/or Hα images. However, if we only classify the events with a brightening increase more than 50% above the quiet background as flares, as measured from EIT data, approximately 88% of the earth-directed CMEs are associated with flares and more than 94% are associated with eruptive filaments. With regard to the locations of CME source regions, there are about 79% CMEs initiating from active regions, while only 21% originate outside active regions. We evaluate the symmetry between CMEs and associated solar surface activity in spatial distributions.
    [Show full text]
  • On Some Properties of Coronal Mass Ejections in Solar Cycle 23
    On some properties of coronal mass ejections in solar cycle 23 Nishant Mittal1, 2 and Udit Narain1, 2 1. Astrophysics research group, Meerut College, Meerut-250001, India 2. IUCAA, Post Bag 4, Ganeshkhind, Pune 411007, India E-mail: [email protected] Abstract We have investigated the some properties such as speed, apparent width, acceleration, latitude, mass and kinetic energy etc. of all types of CMEs observed during the period 1996-2007 by SOHO/LASCO covering the solar cycle 23. The results are in satisfactory agreement with previous investigations. Key words: sun; coronal mass ejections; general properties; solar cycle 23 1. INTRODUCTION The solar cycle and activity phenomena are some of the interesting physical processes that are least understood. Since the discovery of sunspots, their origin and formation with their cycle activity remains a mystery. In a similar way, physics of the recently discovered (compared to dates of sunspots’ discovery) solar activity phenomenon, viz; the coronal mass ejections (CMEs) is yet to be understood. Because of CMEs geoeffectiveness and space weather effects that ultimately involve the societal effects on the earth, frequency of their occurrence and other physical parameters such as mass and kinetic energy need to be documented for theoreticians in order to come out with a reasonable CME model. Coronal mass ejections (see. e.g., Cremades & St. Cyr, 2007, Gopalswamy, 2006, 2004, Gopalswamy et al., 2003a, b and references therein) are a topic of extensive study, since they were first detected in the coronagraph images obtained on 1971 Dec. 14, by NASA’s OSO-7 space craft (Tousey, 1973).
    [Show full text]