Relationship Between the Low-Latitude Coronal Hole Area, Solar Wind
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Cmes, Solar Wind and Sun-Earth Connections: Unresolved Issues
CMEs, solar wind and Sun-Earth connections: unresolved issues Rainer Schwenn Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany [email protected] In recent years, an unprecedented amount of high-quality data from various spaceprobes (Yohkoh, WIND, SOHO, ACE, TRACE, Ulysses) has been piled up that exhibit the enormous variety of CME properties and their effects on the whole heliosphere. Journals and books abound with new findings on this most exciting subject. However, major problems could still not be solved. In this Reporter Talk I will try to describe these unresolved issues in context with our present knowledge. My very personal Catalog of ignorance, Updated version (see SW8) IAGA Scientific Assembly in Toulouse, 18-29 July 2005 MPRS seminar on January 18, 2006 The definition of a CME "We define a coronal mass ejection (CME) to be an observable change in coronal structure that occurs on a time scale of a few minutes and several hours and involves the appearance (and outward motion, RS) of a new, discrete, bright, white-light feature in the coronagraph field of view." (Hundhausen et al., 1984, similar to the definition of "mass ejection events" by Munro et al., 1979). CME: coronal -------- mass ejection, not: coronal mass -------- ejection! In particular, a CME is NOT an Ejección de Masa Coronal (EMC), Ejectie de Maså Coronalå, Eiezione di Massa Coronale Éjection de Masse Coronale The community has chosen to keep the name “CME”, although the more precise term “solar mass ejection” appears to be more appropriate. An ICME is the interplanetry counterpart of a CME 1 1. -
Coronal Holes
Living Rev. Solar Phys., 6, (2009), 3 LIVING REVIEWS http://www.livingreviews.org/lrsp-2009-3 in solar physics Coronal Holes Steven R. Cranmer Harvard-Smithsonian Center for Astrophysics 60 Garden Street, Mail Stop 50 Cambridge, MA 02138, U.S.A. email: [email protected] http://www.cfa.harvard.edu/~scranmer/ Accepted on 15 September 2009 Published on 29 September 2009 Abstract Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed solar wind. This paper reviews measurements of the plasma properties in coronal holes and how these measurements are used to reveal details about the physical processes that heat the solar corona and accelerate the solar wind. It is still unknown to what extent the solar wind is fed by flux tubes that remain open (and are energized by footpoint-driven wave-like fluctuations), and to what extent much of the mass and energy is input intermittently from closed loops into the open-field regions. Evidence for both paradigms is summarized in this paper. Special emphasis is also given to spectroscopic and coronagraphic measurements that allow the highly dynamic non-equilibrium evolution of the plasma to be followed as the asymptotic conditions in interplanetary space are established in the extended corona. For example, the importance of kinetic plasma physics and turbulence in coronal holes has been affirmed by surprising measurements from the UVCS instrument on SOHO that heavy ions are heated to hundreds of times the temperatures of protons and electrons. -
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. -
Predicting Maximum Sunspot Number in Solar Cycle 24 Nipa J Bhatt
J. Astrophys. Astr. (2009) 30, 71–77 Predicting Maximum Sunspot Number in Solar Cycle 24 Nipa J Bhatt1,∗, Rajmal Jain2 & Malini Aggarwal2 1C. U. Shah Science College, Ashram Road, Ahmedabad 380 014, India. 2Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India. ∗e-mail: [email protected] Received 2008 November 22; accepted 2008 December 23 Abstract. A few prediction methods have been developed based on the precursor technique which is found to be successful for forecasting the solar activity. Considering the geomagnetic activity aa indices during the descending phase of the preceding solar cycle as the precursor, we predict the maximum amplitude of annual mean sunspot number in cycle 24 to be 111 ± 21. This suggests that the maximum amplitude of the upcoming cycle 24 will be less than cycles 21–22. Further, we have estimated the annual mean geomagnetic activity aa index for the solar maximum year in cycle 24 to be 20.6 ± 4.7 and the average of the annual mean sunspot num- ber during the descending phase of cycle 24 is estimated to be 48 ± 16.8. Key words. Sunspot number—precursor prediction technique—geo- magnetic activity index aa. 1. Introduction Predictions of solar and geomagnetic activities are important for various purposes, including the operation of low-earth orbiting satellites, operation of power grids on Earth, and satellite communication systems. Various techniques, namely, even/odd behaviour, precursor, spectral, climatology, recent climatology, neural networks have been used in the past for the prediction of solar activity. Many investigators (Ohl 1966; Kane 1978, 2007; Thompson 1993; Jain 1997; Hathaway & Wilson 2006) have used the ‘precursor’ technique to forecast the solar activity. -
Lectures 6, 7 and 8 October 8, 10 and 13 the Heliosphere
ESSESS 77 LecturesLectures 6,6, 77 andand 88 OctoberOctober 8,8, 1010 andand 1313 TheThe HeliosphereHeliosphere The Exploding Sun • We have seen that at times the Sun explosively sends plasma into the surrounding space. • This occurs most dramatically during CMEs. The History of the Solar Wind • 1878 Becquerel (won Noble prize for his discovery of radioactivity) suggests particles from the Sun were responsible for aurora • 1892 Fitzgerald (famous Irish Mathematician) suggests corpuscular radiation (from flares) is responsible for magnetic storms The Sun’s Atmosphere Extends far into Space 2008 Image 1919 Negative The Sun’s Atmosphere Extends Far into Space • The image of the solar corona in the last slide was taken with a natural occulting disk – the moon’s shadow. • The moon’s shadow subtends the surface of the Sun. • That the Sun had a atmosphere that extends far into space has been know for centuries- we are actually seeing sunlight scattered off of electrons. A Solar Wind not a Stationary Atmosphere • The Earth’s atmosphere is stationary. The Sun’s atmosphere is not stable but is blown out into space as the solar wind filling the solar system and then some. • The first direct measurements of the solar wind were in the 1960’s but it had already been suggested in the early 1900s. – To explain a correlation between auroras and sunspots Birkeland [1908] suggested continuous particle emission from these spots. – Others suggested that particles were emitted from the Sun only during flares and that otherwise space was empty [Chapman and Ferraro, 1931]. Discovery of the Solar Wind • That it is continuously expelled as a wind (the solar wind) was realized when Biermann [1951] noticed that comet tails pointed away from the Sun even when the comet was moving away from the Sun. -
Our Sun Has Spots.Pdf
THE A T M O S P H E R I C R E S E R V O I R Examining the Atmosphere and Atmospheric Resource Management Our Sun Has Spots By Mark D. Schneider Aurora Borealis light shows. If you minima and decreased activity haven’t seen the northern lights for called The Maunder Minimum. Is there actually weather above a while, you’re not alone. The end This period coincides with the our earth’s troposphere that con- of Solar Cycle 23 and a minimum “Little Ice Age” and may be an cerns us? Yes. In fact, the US of sunspot activity likely took place indication that it’s possible to fore- Department of Commerce late last year. Now that a new 11- cast long-term temperature trends National Oceanic and over several decades or Atmospheric Administra- centuries by looking at the tion (NOAA) has a separate sun’s irradiance patterns. division called the Space Weather Prediction Center You may have heard (SWPC) that monitors the about 22-year climate weather in space. Space cycles (two 11-year sun- weather focuses on our sun spot cycles) in which wet and its’ cycles of solar activ- periods and droughts were ity. Back in April of 2007, experienced in the Mid- the SWPC made a predic- western U.S. The years tion that the next active 1918, 1936, and 1955 were sunspot or solar cycle would periods of maximum solar begin in March of this year. forcing, but minimum Their prediction was on the precipitation over parts of mark, Solar Cycle 24 began NASA TRACE PROJECT, OF COURTESY PHOTO the U.S. -
Prediction of Solar Activity on the Basis of Spectral Characteristics of Sunspot Number
Annales Geophysicae (2004) 22: 2239–2243 SRef-ID: 1432-0576/ag/2004-22-2239 Annales © European Geosciences Union 2004 Geophysicae Prediction of solar activity on the basis of spectral characteristics of sunspot number E. Echer1, N. R. Rigozo1,2, D. J. R. Nordemann1, and L. E. A. Vieira1 1Instituto Nacional de Pesquisas Espaciais (INPE), Av. Astronautas, 1758 ZIP 12201-970, Sao˜ Jose´ dos Campos, SP, Brazil 2Faculdade de Tecnologia Thereza Porto Marques (FAETEC) ZIP 12308-320, Jacare´ı, Brazil Received: 9 July 2003 – Revised: 6 February 2004 – Accepted: 18 February 2004 – Published: 14 June 2004 Abstract. Prediction of solar activity strength for solar cy- when daily averages are more frequently available (Hoyt and cles 23 and 24 is performed on the basis of extrapolation of Schatten, 1998a, b). sunspot number spectral components. Sunspot number data When the solar cycle is in its maximum phase, there are during 1933–1996 periods (solar cycles 17–22) are searched important terrestrial consequences, such as the higher solar for periodicities by iterative regression. The periods signifi- emission of extreme-ultraviolet and ultraviolet flux, which cant at the 95% confidence level were used in a sum of sine can modulate the middle and upper terrestrial atmosphere, series to reconstruct sunspot series, to predict the strength and total solar irradiance, which could have effects on terres- of solar cycles 23 and 24. The maximum peak of solar cy- trial climate (Hoyt and Schatten, 1997), as well as the coronal cles is adequately predicted (cycle 21: 158±13.2 against an mass ejection and interplanetary shock rates, responsible by observed peak of 155.4; cycle 22: 178±13.2 against 157.6 geomagnetic activity storms and auroras (Webb and Howard, observed). -
Waves and Magnetism in the Solar Atmosphere (WAMIS)
METHODS published: 16 February 2016 doi: 10.3389/fspas.2016.00001 Waves and Magnetism in the Solar Atmosphere (WAMIS) Yuan-Kuen Ko 1*, John D. Moses 2, John M. Laming 1, Leonard Strachan 1, Samuel Tun Beltran 1, Steven Tomczyk 3, Sarah E. Gibson 3, Frédéric Auchère 4, Roberto Casini 3, Silvano Fineschi 5, Michael Knoelker 3, Clarence Korendyke 1, Scott W. McIntosh 3, Marco Romoli 6, Jan Rybak 7, Dennis G. Socker 1, Angelos Vourlidas 8 and Qian Wu 3 1 Space Science Division, Naval Research Laboratory, Washington, DC, USA, 2 Heliophysics Division, Science Mission Directorate, NASA, Washington, DC, USA, 3 High Altitude Observatory, Boulder, CO, USA, 4 Institut d’Astrophysique Spatiale, CNRS Université Paris-Sud, Orsay, France, 5 INAF - National Institute for Astrophysics, Astrophysical Observatory of Torino, Pino Torinese, Italy, 6 Department of Physics and Astronomy, University of Florence, Florence, Italy, 7 Astronomical Institute, Slovak Academy of Sciences, Tatranska Lomnica, Slovakia, 8 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA Edited by: Mario J. P. F. G. Monteiro, Comprehensive measurements of magnetic fields in the solar corona have a long Institute of Astrophysics and Space Sciences, Portugal history as an important scientific goal. Besides being crucial to understanding coronal Reviewed by: structures and the Sun’s generation of space weather, direct measurements of their Gordon James Duncan Petrie, strength and direction are also crucial steps in understanding observed wave motions. National Solar Observatory, USA Robertus Erdelyi, In this regard, the remote sensing instrumentation used to make coronal magnetic field University of Sheffield, UK measurements is well suited to measuring the Doppler signature of waves in the solar João José Graça Lima, structures. -
Automated Coronal Hole Identification Via Multi-Thermal Intensity
J. Space Weather Space Clim. 2018, 8, A02 © T.M. Garton et al., Published by EDP Sciences 2018 https://doi.org/10.1051/swsc/2017039 Available online at: www.swsc-journal.org Developing New Space Weather Tools: Transitioning fundamental science to operational prediction systems RESEARCH ARTICLE Automated coronal hole identification via multi-thermal intensity segmentation Tadhg M. Garton*, Peter T. Gallagher and Sophie A. Murray School of Physics, Trinity College Dublin, Dublin 2, Ireland Received 8 June 2017 / Accepted 21 November 2017 Abstract – Coronal holes (CH) are regions of open magnetic fields that appear as dark areas in the solar corona due to their low density and temperature compared to the surrounding quiet corona. To date, accurate identification and segmentation of CHs has been a difficult task due to their comparable intensity to local quiet Sun regions. Current segmentation methods typically rely on the use of single Extreme Ultra-Violet passband and magnetogram images to extract CH information. Here, the coronal hole identification via multi-thermal emission recognition algorithm (CHIMERA) is described, which analyses multi-thermal images from the atmospheric image assembly (AIA) onboard the solar dynamics observatory (SDO) to segment coronal hole boundaries by their intensity ratio across three passbands (171 Å, 193 Å, and 211 Å). The algorithm allows accurate extraction of CH boundaries and many of their properties, such as area, position, latitudinal and longitudinal width, and magnetic polarity of segmented CHs. From these properties, a clear linear relationship was identified between the duration of geomagnetic storms and coronal hole areas. CHIMERA can therefore form the basis of more accurate forecasting of the start and duration of geomagnetic storms. -